Archive for the ‘Questions and Answers’ Category

Question: Can You Put Road Tires On A 29"er Rim?

January 15, 2009

From time to time I get questions on the site in the form of comments, or e-mails that I like to address with a post. Today’s question is about putting road tires on 29 inch rims. Can you do it? Are they compatible? What sizes are recommended? There are a lot of confusing answers floating around out there, so let’s take a look and see if we can figure this one out………..

Easton XC One wheels These Easton single speed wheels are for 29″ers, but have a narrow-ish rim width suitable for road rubber.

The Fit Question- Diameter: Okay, let’ get this cleared up right away. It is commonly thought that 29″er wheels are a different diameter than everything else out there. I suppose the moniker, “29”er” is to blame, but make no mistake, it is 700c. 700c, or ISO 622mm is the rim diameter for both 29″ers and road racing bikes. In fact, the ISO 622 is a very common rim diameter that is used on a wide spectrum of bicycles. The term- 29″er- refers to the total diameter of the tire and wheel together, with the rim size being ISO 622mm, or as it is commonly referred to as, 700c. Okay? That part is the simple part.

Salsa Gordo rims
A wide 700c rim, like these 35mm wide Salsa Gordo rims, are not suited for road going rubber unless it is 50mm wide or wider.

The Fit Question- Rim Width: Now here is where things get a little dicey. To make it simple, you will need to match your tire width to your rim width after you determine that the diameters are compatible. So, what does that mean exactly? Let’s assume we are using only 700c/ISO 622 rims and tires to keep that part of the equation constant.

A typical road tire will measure around 23mm to 28mm wide. To support the tire properly, and to allow it to function in a way that is safe, the rim the tire is mounted to must be within a certain range. Too narrow and the tire will “roll” or squirm in corners, and too wide will cause the height of the casing to be to low in relatioship to the rim walls. This will encourage tire blow offs and more pinch flat problems, not to mention a higher likelyhood of rim damage. To properly support a tire in this width range, I would recommend any rim that was 19mm wide to no more than 24mm wide. Any wider and you will start to see a drastic increase in the problems I detailed above.

Some 29″er wheels have rims in this range. The Easton set, pictured above, has a 23.5mm wide rim, which should work fine with road tires in our 23mm to 28mm range. What about wider 29″er rims? Well, you would by necessity start to have to look at a wider tire.

A 24mm to 28mm wide rim, which covers a lot of 29″er rims, would probably work best with tires 30 to 35mm wide, the wider rims needing the wider tires in this range. Something on the order of the Gordo (pictured above) would require a much larger tire, say at least a 2.0 inch tire and on up.

I suppose some folks will say that these recommendations are too conservative, but in my mind, it is best to match proper components for the job at hand. (Of course, it could be said that running narrow tires on mountain bike rims is not matching up your components properly in the first place!) Putting a 25mm tire on a 28mm wide rim is not fitting that ideal in my mind, and I would not recommend doing that.

Conclusion: So, the answer to our question is a qualified “yes” with the qualification being that your diameters, while matching for rim and tire, are not the sole determination of whether certain combinations will work. Width of the tire and rim must match within a reasonable range also, or you will be inviting trouble.

Twenty Nine Inches Plays "Tag"

August 6, 2008

Editors Note: “Blog Tag” is a harmless form of a chain letter that bloggers engage in consisting of several questions that are meant to be humorous and yet insightful. Normally we wouldn’t engage in such tom foolery, but since this “tag” is heavily bicycle oriented, I figured that it might prove to be some fun, comic relief for all of you out there. Especially after wading through all of this fork testing recently. Enjoy!

If you could have any one — and only one — bike in the world, what would it be?

Okay, so you do realize this is Twenty Nine Inches, the site about 29″ers? The answer should be obvious then. But to be specific I would opt for a single speed, since I could only have one bike and all. A single speed that could be converted into a geary, of course.

Do you already have that coveted dream bike? If so, is it everything you hoped are you working toward it would be? If not, getting it? If you’re not working toward getting it, why not?

The perfect answer was given to this question by the person who “tagged” me. So I am going to use their answer as mine, since I can’t possibly put this any better than they did.

Shouldn’t dream bikes remain just that…as Dream Bikes. As soon as you acquire your Dream Bike your mind begins to wander to yet another bike. And suddenly you’re committing Bike-dultry on your dream ride. So, much like dating, I’ll continue to ride bikes that are ‘obtainable’ and allow my Dreams to evolve with the industry.

If you had to choose one — and only one — bike route to do every day for the rest of your life, what would it be, and why?

I like single track and gravel roads. I like long rides. So my route would include all of that. It would take all day, every day. There would be great Mexican food and beer at the end with my family and friends too. (Hey! Every route has to have a destination, right?)

What kind of sick person would force another person to ride one and only one bike ride to do for the rest of her / his life?

I don’t know, but they are truly sick and twisted. Oh…….and unrealistic too!

Do you ride both road and mountain bikes? If both, which do you prefer and why? If only one or the other, why are you so narrowminded?

Hmm….I didn’t realize there were different kinds of bikes in this regard. I use my bike on the road- then it is a “road bike”, if I ride off road,it is a “mountain bike”. Right? I mean, in the end, they are all just bikes.

Have you ever ridden a recumbent? If so, why? If not, describe the circumstances under which you would ride a recumbent.

Actually, I have ridden quite a few recumbents as part of my gig as a shop wrench. Plus, I got to ride one all day for a commercial film shoot.

Have you ever raced a triathlon? If so, have you also ever tried strangling yourself with dental floss?

No, I have not. But I did do a mountain bike race once that included a 75 yard in the river hike a bike on each lap and numerous sections where we all had to dismount and traverse some nasty ravines. Does that count?

Suppose you were forced to either give up ice cream or bicycles for the rest of your life. Which would you give up, and why?

At least this isn’t a tough question. Now really, it should have been a choice between beer and bikes. That would have been tougher! Obviously, the ice cream would have to go.

What is a question you think this questionnaire should have asked, but has not? Also, answer it.

My question would be: If you could change one thing- and only one thing- about cycling, what would it be?

Answer: I would banish all the “us vs. them” factionalism in the sport. Hey, we all love to ride bikes, right?

You’re riding your bike in the wilderness (if you’re a roadie, you’re on a road, but otherwise the surroundings are quite wilderness-like) and you see a bear. The bear sees you. What do you do?

Say, “Hey! How’s it goin’?” and hope he’s in a good mood.

Editors Note: Normally at this point you are to name some other bloggers and link them, so they are “tagged” into passing on this nonsense. I don’t often play by the rules, so I am not going t engage in that facet of this. I hope you enjoyed the break from the “normal” Twenty Nine Inches fare. Now….I return you to your regularly scheduled programming!

A 29″er UST Standard: An Update

July 23, 2008

A little over a year ago, I wrote a post here about the coming of UST standard approved tires and rims. I recently got a question regarding this subject:

Is there any word on when we will get more choice in tire(s)? This article is over a year old and still only one tire is available.

Well, while this is true, there have been several developments since then that bear looking into. Let’s see where we are and where we might be going.

Hutchinson Python tubeless ready tires

The “tire” in question that has a UST certification for use with sealant is the Hutchinson Python. Huthinson has also introduced a Toro model in 29″er size that should become available soon. This would make two 29″er tires available with the much ballyhooed UST certification seal. That doesn’t quite seem to be cutting it for some folks. The feeling I get perusing the various forums and talking to folks is something that isn’t congruent with what tire manufacturers are doing, and really, is incongruent with riders own expectations.

Right now there is a group of folks waiting for a “true UST” tire in 29″er size. My opinion is that you will probably never get it. What is “true UST”? It is the idea some folks have based from the earliest 26″er UST tires that all tubeless UST tires need no sealant. In many riders minds, there isn’t any other UST type tire out there. But there is. It is the UST tire that requires sealant to work, most commonly known as “tubeless ready”. These tires meet UST certifications and are compatible with UST certified rims. Yet some riders do not recognize this as UST.

Bontrager XDX tires

Why won’t you see a UST tire that requires no sealant in 29″er size? Because of weight. A UST tire requiring no sealant adds extra butyl rubber to the casing making it air tight. Some may see this as a cool thing for sharp rocks or more abusive riding, but for mere tubeless uses, it is a deal killer for 29″er freaks and the manufacturers know it. I’m not saying it will never happen, but I wouldn’t hold my breath.

Why don’t we see more UST certified tubeless ready tires? I think manufacturers are finding out they can do rims and tire manufacturers are finding out they can do tires that will work together tubeless without spending the money for the UST certifications. Bontrager’s Tubeless Ready tires and wheels are an excellent example- no UST certification needed. However; in my mind the real underlying reason for the lack of tubeless ready UST tires and rims is Stan’s NoTubes and the efforts of individual riders all over the world who have turned to making tubeless work on their own terms. If you, as a manufacturer, see what is going on out there, why would you spend the money on a certification when you can make an end around on the whole thing. Think about Panaracer, who when introducing the Rampage more or less gave its blessing on using it tubeless. Continental has essentially done the same thing, declaring all their mountain bike tires safe to use with any of the mountain bike tire sealants commercially available. Doesn’t sound as though either of those manufacturers is interested in doing a UST 29″er tire anytime soon, does it?

Stan's NoTubes Flow rim diagram

Then you have the various rim manufacturers who are doing a lot of refinements to rim bead seat designs on 29″er rims, not saying they are “tubeless compatible”, but making it a lot easier to do just that. WTB, Sun, and Salsa are three that I saw at Interbike that were doing new rim bead seat designs, but not going so far as to say they were tubeless compatible.

What of Geax and Michelin? I have seen that Geax has gone their own route with the “TnT” concept and Michelin is also rumored to be doing their own tubeless ready type designs without seeking UST certification. At one time it was rumored that these companies would do a UST 29″er tire, but this seems to be not the case now.

So, revisting that article of over a year ago makes me say that I was wrong. There still is “that” argument against 29″ers. However; you can choose to stick with looking for a UST 29″er tire, but the rest of your riding buddies and competitors at the races are already doing something about it. Tubeless ready type tires are here now and there are rims that work as well. Some will scoff and say the risk isn’t worth it, but it’s something that isn’t going away anytime soon. Advantage or disadvantage for 29″ers? You’ll have to make that call.

Salsa "Sol Sessions": The Big Mama

June 17, 2008

Salsa Cycles has been working on this new full suspension platform for quite some time and now……here it is!

The new model!

The Big Mama is a four inch travel suspension platform with several important features which I’ll get into a bit later. First off, I was able to get a chance to ride this bike on Sunday at the local Murphy-Hanrahan trail system. It is a great buff, fast, tight and twisty single track loop. I was able to put in 16 miles on the new rig and I will say, it was a very satisfying ride.

My observations of 29 inch wheeled full suspension bikes is that most of them are compromises of what I like in a 29″er. They seem to be good at some things, but have lost certain handling characteristics, aesthetic characteristics, or structural characteristics in the translation from hard tail to full suspension. There are few that seem to have it dialed and look good doing it. Is the Big Mama in that rarefied air? Let’s take a look.

New graphics

I have ridden a lot of full suspension bikes and the first thing one should determine is “what type” of full suspension are we talking about. Salsa head honch, Jason Boucher, says this is first and foremost an “all day trail bike”. Taking that into consideration as I rode it, I could then discern if it fit into my expectations for such a bike. I would say that such a bike should be maneuverable, respond to pedaling input in a positive way, (read “like a hard tail”), be stiff laterally, and have overall handling that is easy to navigate when the rider is tired. It should also do what the best trail bike full suspension should do, that is, keep the rider fresh and keep the wheels in contact with the ground. Finally, it should be fun and look cool. (Hey! I like my rigs to look good!)

one piece forged linkage

The heart of the Big Mama is it’s detailed suspension and frame fittings. Things like the one piece forged link, (pictured above) help keep things tracking correctly. The hidden part here is the Enduro brand bearings used at all pivot points. The drive side of the swing arm is even fitted with two bearings, while the non-drive side has the traditional single bearing, which helps keep the swing arm pivot stiff and resist twisting forces from the pedaling input of a rider. Did it work? Well, all I can say is that I never once felt anything close to flex in the bottom bracket area. The huge bottom bracket forging, which includes the swing arm pivot, no doubt helps in this area. In fact, that swing arm felt pretty stout too. The reason why was evident……

rear drop out area

……Notice something missing? Yep! No pivot. Salsa Cycles designed the suspension with no rear drop out pivot, not because they think the rear pivot idea wasn’t any good, it just rode better than the designs that had rear pivots in their testing. So, to get around the pivot and have it ride well, Salsa designers went to the toolbox and pulled out their experiences with the Dos Niner. The soft tail classic has chain stays designed to flex up to an inch and survive trail abuse over the long haul. The flattened Scandium enhanced structure makes a return here on the Big Mama in the seat stays and only has to flex a whopping 5mm throughout the stroke of the shock. Salsa claims it helps reduce starting shock pressures needed and with the custom tuned Fox RP2, it helps achieve full travel from the damper. Did it work? Well, with the shock set to the open position on my test ride the Big Mama rode with small bump sensitivity and didn’t feel like it ramped up or stiffened in any way towards the end of it’s travel. It just reacted to bumps with no drama and made me forget all about suspension. That’s what a good suspension design should do, become invisible.

shaped down tube

head tube/down tube junction

Salsa Cycles tried to maximize the weld areas on the bike and to reduce the places that required welding on the Big Mama. To do this they utilized special forged frame fittings, like the drop outs and the bottom bracket area. They also shaped the Scandium tubes, which were all specially designed by Salsa, to help combat flex where riders don’t want it. Check out that down tube/ bottom bracket junction, pictured above, or that down tube/ head tube weld area. There is some serious manipulation of tubes going on with the Big Mama. Did it work? Well, one of my biggest pet peeves about 29″ers is that many of them exhibit a torsional twist in the front triangle which leads to a vague steering feel and in bad cases a total disconnect between tracking of the rear and front wheels. I can say that I felt the Big Mama tracking a good straight line and that it didn’t feel like it had any significant torsional flex in the front end. yeah, I’d say all that tube shaping and weld area work was worth it.

swingarm clearances

Of course, this being an all day trail bike sort of rig, it would only make sense that you would be able to run big meats and still have some clearance around the tire for mud and trail debris. Salsa engineers made sure that you will be able to mount up a 2.5″ wide tire on a 35mm wide rim and have that clearance. I’ll have to take their word on that, as the samples I rode and saw all had Nevegals on them, but to my eye, it looks like a sure fit. That swing arm forging also helps solidify things laterally too. Nicely done!

Post mounts!

Salsa’s design goals for this project were to have reliability, durability, and attention to detail. In that vein, they chose to fit the Big Mama with post mount type fittings for the rear disc brake. This is in keeping with the move by fork makers who have gone to post mounts and should give the Big Mama better braking performance given that the brake caliper is now mounted to a sturdy forged bit directly welded to the frame.

A few notes on my ride that I have not mentioned: The Big Mama was easy to wheelie, and was nimble feeling with a slight nod to the stable side of the handling spectrum. When I rode the production prototype, I had no idea about the “numbers”, since they were kept from me. I found out only later that the head angle is 71 degrees and that the Fox fork has 46mm of off set here. With this combination, I felt the Big Mama felt calm and collected on hairy fast descents through the tight single track. Climbing didn’t require any extra attention to the front end other than that I had to weight the front a bit more or I could wheelie at will. Something that could be cured if I wanted to with positioning tweaks, but frankly, I liked it this way. The bike cornered really well and what impressed me most was its ability to carve around a really tight corner with stability. This rig should help you clean switchbacks that have given you fits on other big wheelers.

The Big Mama will also be available as I got to ride it with Fox suspension, Race Face stem and seat post, and a good helping of Shimano XT parts including the brakes, hubs, and drive train. Salsa bits round out the package which will be topped off with a WTB saddle. Frame sets will include the Fox RP2 and a Salsa Flip-Lock seat collar. Look for the frame sets to become available in September with a suggested MSRP of $1435-$1500. The complete Big Mama bikes will come in January of ’09 and will be MSRP at about $3800-$4000. (One note, the bike pictured here has the black Fox shock, which is the color for the ’09 120mm travel F-29. The complete bike will actually be spec’ed with the 100mm travel fork and was white in our hand outs) Go to Salsa Cycles and check out the specs and information on the Big Mama. I also should mention that the very similar 26″er model, the El Kaboing, will also be available and was presented at the press release as well.

In conclusion, I felt that Salsa Cycles has done their homework and applied solutions with elegance and effectiveness to the problem of making a great 29″er trail bike. Have they come up with something that fits my definition of a 29″er trail bike? If the 16 miles I got to ride it is any indication, I would say that the Big Mama is well on it’s way to filling that rare place in my mind. Will it work for you? I know that there will be those who won’t like it, but my guess is that the Big Mama will be a very popular rig with a lot of 29″er freaks. If the design fulfills the goals that Salsa Cycles set for it, and it gives every indication that it will, I would go as far as to say that this will be its best selling 29″er rig. Time will tell on that, but for now, this bike is high on my list of full suspension 29″ers.

Edit 6-22-08: Salsa Cycles Jason Boucher has informed me that the Fox F-29 will indeed be black as shown on the pics above. He especially spec’ed a black fork. It is still the 100mm travel fork. Sorry for the confusion this may have caused.

A Question Of Wheel Strength

February 26, 2008

Question: Why don’t they make the hubs for 29″er wheels with bigger diameter hub flanges so the wheels can be stronger?

Answer: The matter of wheel strength for 29″ers has been a concern ever since the modern 29″er hit the scene almost ten years ago now. Longer spokes are often times pointed at for being the culprit here. However; is that really the case? Let’s take a look at somethings that may clear up this matter for us.

Wheels have several things that can affect their strength. The way the materials are used, the way they are assembled, and how these two work together are the basics of wheel strength. Particular things such as the spokes, their shape, number and length can affect wheel strength to a degree. Rim diameter, profile, and design are other critical factors. Hub flange strength is important to anchor those spokes well. Let’s assume we are using high quality, well made parts in our wheel assembly and we have the best wheel smith putting it all together.

So, in this scenario, why would a 26″er wheel be stronger than a 29″er wheel? Lots of you are going to say it’s the long spokes. In reality, it’s the geometry of the wheel that is the issue. Let’s take a rear wheel as an example.

Back in the 80’s, when wheels had but 6 speeds, wheels were pretty much symmetrical in nature. That is to say, the angles at which the drive and non-drive side spokes left the hub flange were identical, or nearly so. Now with the addition of each speed up to the 9 we have today in a mountain bike cassette, compromises in wheel geometry had to be made to accomodate the space taken up by the cassettes. Take a look at any rear wheel with a multiple speed cassette. You will notice the drive side spokes leave the hub at a much shallower angle than the non-drive side spokes do. Front wheels are not exempt either. Disc brake rotors cause the same compromises in spoke angles. This is called “dish and causes wheels to be weaker than they would be if they had symmetry of spoke angles from drive side to non-drive side.

This is the biggest influence on wheel strength beyond materials design. In fact, hub flange diameter, and thus spoke length, are much less of a factor. Increasing flange diameter has not been proven to show much, if any, increase in wheel strength.

So, in terms of our original question, the hub flanges have a nominal effect on wheel strength. Increasing the distance between the hub flanges and having a dishless wheel has a much more dramatic effect on wheel strength.

What can be done then? Wheel overlock dimensions have been set since the onset of the 90’s for mountain bikes at 135mm for a rear wheel and 100mm for a front. Is this as good as it gets? Well, some things are pointing to changes in this area.

Niner’s W.F.O 9, an all mountain 29″er that is currently in developement, has a 150mm OD rear hub, a width commonly used for tandem bicycles and some down hill specific machines. (Guess why!) Lenz Sport’s Lunchbox full suspension 29″er also already is using this rear over lock dimension to get a dishless, thus stronger, rear wheel. But what about the front?

Well, that is being looked at by Paul Components who showed a 120mm OD front disc hub aimed at 29″ers at the recently held NAHBS in Portland, Oregon. Word is a suspension fork manufacturer is also looking at this standard as well.

For now it’s best to use a rim, spoke count, spoke guage, and hub design best suited to you and your riding style and to have a competent wheel smith put it all together.

A Question Of Making a 69er Out Of A 29"er

February 14, 2008

Editors Note: From time to time we get a question that we choose to post here. The answers given hopefully will help others and at the least, be somewhat entertaining.

Question: Can I put a 26 inch rear wheel in my 29″er? How will that affect the bike? Is it a good thing to try?

Answer: Well, three answers really. Yes. Negatively. Not really. Now, let me flesh this out for you.

The answer to your first question is “yes” only if you are dealing with a frame and wheel that is disc brake compatible. Rim brakes won’t work with such a change in diameter. Pretty simple there.

The second answer, “negatively”, is a bit more complicated. Let’s take a look at what really is going on when we pop a 26″er wheel in a 29″er frame. Think of the front axle as a pivoting point. Now imagine lowering the rear end of your bike without a rear wheel in it by pivoting the bike downwards around that front axle. Watch how the angles all become slacker and the bottom bracket gets a little closer to the ground. Yep! That’s what is going to happen to your 29 inch wheeled bike when you put a smaller rear wheel back there.

This causes several things, all of which I would deem negative, and I think most of the time, in most cases it is true. First the head angle gets shallower, causing slower steering and strange cornering behaviour. The seat angle changes, putting you further behind the bottom bracket and adversely affecting your seated pedaling posistion. It also will make seated to standing pedaling posistion maneuvers more difficult to pull off. Finally, your bottom bracket will be closer to the ground, increasing the chances for pedal strikes.

Now for the third answer, “not really”. It isn’t going to be a good representation of what a properly designed mixed wheel bike will do. At best, you will have a functional bicycle, at worst, it may be deemed unridable off road. Best to save up for a properly designed mixed wheel bike and leave the 29″er alone.

Who Does "Monstercross"?

January 29, 2008

A Twenty Nine Inches fan photo

Monstercross, that category of bike that isn’t quite a 29″er, and isn’t really legal for “true” cross racing in most sanctioned circles. The category of big wheeled bikes that blurs the lines between road and mountain bike. If you are not familiar with “monster cross” type bikes, here is a loose definition of the breed.

A typical monster cross build could perhaps best be described as a cyclo-cross bike on steroids. Usually a cyclo-cross frame with enough clearance to fit something between 45mm and 52mm of fat rubber will get you the “monster cross” tag. (Well, if you are actually using the fat rubber, that is.)

Twenty Nine Inches wants to know, “Who does ‘Monstercross’ out there?” and why. How do you use your “monster crosser”? Should it be included in 29″er coverage?

Use the comment section and let us know what you think.

Tuning The Ride: 29"ers and Steering Performance Part III

January 8, 2008

Editors Note: This is the third and final installment of this series. However; it is not the end of the story. We’ll be focusing in on different aspects and theories concerning 29″er geometry throughout 2008

One of the things I mentioned on Twenty Nine Inches in a different post concerned the seemingly divergent paths that the designers of 29″er bikes and forks are pursuing. I’ve also seen it mentioned in recent comments. This post will explore a bit of those concepts to perhaps get a clearer picture of what is going on.

Hi Fi Pro with G2 geometry

One of the paths that designers have been pursuing over the last few years is a way to get 29″ers to feel more “26”er-ish”. This mostly has to do with getting away from the feeling that a 29″er sometimes has of requiring more input to initiate turn in and to overcome the 29″ers natural tendency to want to stay on its path as it spins, or in other words, its gyroscopic tendencies. Combined with a larger trail figure, this can be felt as a “sluggish” feeling in some riders minds. Various types of designs have attempted to address this trait of big wheels to various degrees. The flagship design of this type of philosophy in my opinion is the G2 29″er geometry that Gary Fisher Bikes has offered on its 2008 line of 29″ers. It excells in being a design that 26″er devotees can hop aboard and feel right at home on. Still possessing 29″ers abilities to roll over stuff and carry momentum easier, it has erased the “heavy” feeling some associate with 29″ers.

Interestingly, some refer to the Fishers and similar bikes as “new school” geometry. I think, if anything, it should be called “old school” geometry because most of these bikes are trying to emulate the “old” 26″er steering feel. Not a bad thing, but in no way is this a “new” thing. Whatever you call it, it is a definite trend and I expect it to expand with the passing of time.

LenzSport Lunchbox: Sometimes the #'s don't add up!

There still is a contingent out there that celebrates the 29″er wheels stability and steering quirks as being the very thing that differentiates 29″ers from 26″ers in the first place. This design philosophy was best demonstrated to me by this LenzSport Lunchbox 29″er. It has dual suspension and longer travel, and that certainly factors into things, but the trail figure on this bike was off the charts high compared to anything I had yet ridden. Still, it behaved quite well on the trail and imparted a sense of security that inspired me to want to tackle bigger hits and attain more speed while doing so. I think the enhancement of the 29″ers inherent traits made me feel these things as much as the longer travel did, if not more so. (Special mention for a bike like this would also go to the Raleigh XXIX+G with stock geometry. We’ll be testing this bike in that form again soon.)

Most 29″ers out there today are somewhere in the middle of this “handling continuum”. Being able to tune the handling to go towards one end of this continuum or the other is a trick that we didn’t have only just a year ago. What a great time to be riding big wheels!

Look for “updates” to this story over the course of 2008 as Twenty Nine Inches seeks to discover just how all this geometry works out on the trail.

Tuning The Ride: 29"ers and Steering Performance Part II

January 6, 2008

Now we’ll be able to tune our rides.

Gary Fisher

I am leading out with this quote uttered to me at Interbike 2006. It was the first inkling I heard that there would be several suspension forks coming out with different and longer offsets. The quote is important to how I think one needs to look at what has happened to the 29″er landscape. “Tune your ride”, has opened a veritable can-o-worms in the way we can look at our rigs and their potential these days. However; I think it is important to recognize that the recent “revolution” in fork/front end geometry isn’t really all that new.

Here is a super brief history lesson on fork offset and front end geometry for mountain bikes. It goes way back to the beginning of modern day mountain biking with things like variable head tube angles and multiple off set forks that were well known back in the 80’s to most enthusiasts. The work done on fork offset by Keith Bontrager in the late 80’s/early 90’s was a well known and popular alternative to the “standard” geometry of the day. It wasn’t until the advent of the suspension fork that front end geometry settled on the 38mm offset/71 degree head angle that became known as “NORBA Geometry” because of the professional racers that preferred the handling this produced. Things didn’t really change all that much for the shorter travel XC bikes after that point.

As I noted in my previous post, early 29″ers followed this same geometry formula for the most part and only a slight increase in head angle was first tried out. Then Gary Fisher Bikes came out with 29″ers equipped with Marzocchi forks sporting a 43mm offset. This was followed by what I consider the ground breaking move in fork offsets for 29″ers.

On One came out with a 29″er single speed bike that sported a 47mm offset mated to a 72 degree angle head tube. This pairing gave On One 29″ers a snappy front end that was the closest approximation of a 26″ers handling yet seen on the trail. It is also good to note that it also retained a good bit of “29”er-ish” qualities as well. Of course, this daring offset was on a rigid fork. What would occur if it were to be translated to the dynamic world of suspension?

Well, we now know what happened, of course. The questions now are about mixing and matching different frames to forks with varying offsets. Should it be done and what effect will it have? Will you “ruin” your ride? Can you make it better?

The answers are not as clear as it would seem. (Take a look at the comments section from the previous post in this series to see what I mean) You can get somewhat of an idea from these simplistic guidelines.

More offset = quicker/less stable handling Keeping in mind that our baseline offset is 38mm, (which a lot of 29″ers still use, by the way) and “more offset” is a measurement longer than 38mm. Also, you may want to take note of your bicycles head angle. You might not want to install a longer offset fork on a bike that already has a 73mm head angle, for instance.

Axle to crown measurements may affect your head angle to start with. The axle to fork crown measurements can vary slightly from one suspension fork, or even rigid fork, to another. If the net result of axle to crown difference from one fork to another is great enough, it can affect your static head angle as much as 1/2 to 1 degree either way. Keep this in mind when considering a fork swap. And remember, suspension is dynamic in all its important dimensions. Add rear suspension and it gets even more hairy!

After doing all the math, install the fork and ride! This is probably the most important advice here. You will only know if your experience has been enhanced by actually riding the bike. Chances are if you did your homework, you’ll be okay.

I’ve done fork swaps taking the fork offset to a shorter figure from a longer one and vice versa. My experience is that you can certainly tell a difference in how the bike steers and reacts in turns. Some of my experiences were negative, some were really successes, and others mildly interesting. None of them were what I would term as “failures” or experiments that “ruined” my handling. In each case, I had a notion of what the change might do based upon previous calculations. Trail rides sometimes revealed surprises that I didn’t expect. In the end, I think it is entirely possible to “tune” your ride if you do it with consideration and forethought.

Should you try tuning your fork/front end handling? Well, keep in mind that the human that rides the bicycle is a very adaptive creature and a very subjective one. I would caution against jumping in without very careful consideration. Forks are not cheap and making a choice without doing your homework ahead of time could be disastrous if you go the wrong way with things. That said, a fine tuning of your bikes handling can be done in many cases without jumping all the way into a new rig. Test rides are always the best bet, but if you can not score a test ride on someone elses rig, you’ll have to pony up for your own “research”. It can be fun and rewarding if you are careful.

Next post: 29″er handling vs. 26″er handling: How much is good to have on your 29″er?

Tuning The Ride: 29"ers and Steering Performance

January 5, 2008

One of the recent developements in the history of 29″ers that has caused more confusion and questions than probably the existence of 29″ers themselves is the change in fork offset by prominent suspension manufacturers to “tune” the handling of 29″ers. Why was this done? Is there an “old 29″er geometry” and a “new 29″er geometry”? Can you mix and match forks and frames from different design philosophies? And the questions go on. In these posts I will try to briefly touch on some facts and try to dispel some myths about the current state of affairs as it relates to handling characteristics of 29″ers.

Fact: A 29 inch front wheel will have more trail because of its size. This is the reason for everything that follows and the first thing one needs to understand to be able to follow along. Fork trail is the measure that helps one determine the relative stability/instability of an inline wheeled vehicle. Simply picture a shopping cart wheel or a dolly wheel. The “pivot” that attaches to the cart/dolly is the steering axis. The contact patch of the cart/dolly wheel follows this axis as you push the cart/dolly along. The distance from the centerline of the steering axis to the wheel contact patch is a measure called “trail” or in the case of a bicycle, “fork trail”.

This “trail” measurement increased when modern 29″ers were first developed as a direct result of using a larger diameter wheel. (I won’t get into the details of this, but trust me, it is true) While most of the other critical front end measurements stayed the same, this increase in fork trail dialed more stability into the front end of the earliest 29″ers. The early adopters liked this trait, and so they did not try to change the front end geometry much if at all.

Fact: Many judged the 29″er against what they knew before- the 26 inch wheeled mountain bike. Some early critics of 29″ers were quick to point out this new 29″er geometry as being “not quick and snappy, like a 26″er”. Thus they panned the new wheelsize for this, (and several other) reasons. Others were interested in seeing if something could be done to “improve upon” the matter at hand, so the first of many “fixes” were applied to 29″er bikes. These were sometimes used alone or in combination with each other. The most popular being to increase the head angle from the 26″ers 71 degree angle to something around either side of 72 degrees head angle. This had the effect of decreasing the trail measurement back closer to a 26″ers and made the front end steer with less effort and lost a bit of stability in the process. Of course most applauded the effort to more closely approximate 26″er handling, but the critics still said, “Too sluggish!”

Okay, that should set the stage for what has happened recently. The big problem was always that you were pretty much stuck with using the fork offset on suspension forks that was developed for 26″ers on 29″ers. This made getting a suspended hardtail or full suspension 29″er to steer with a snappy, quick feel hard to obtain. The idea was that if the slate could be wiped clean, a new offset(s) that would work to make 29″ers more like a 26″er in turn in feel and not be unstable could be obtained. Either that or use the same offset as always, (38mm) and keep steepening the head angle to achieve a more snappy, quick front end. And finally, some companies have elected to keep doing the same type of front end geometry that 29″ers have been using since about 2003, which is a slightly steeper head angle than a 26″er and keeping the offset at 38mm or so. Some would call the first two examples “new” 29″er geometry, and some would call the last example “old school geometry” for 29″ers.

Myth: There are “old” geometry 29″ers and “new” geometry 29″ers This is simply false. The fact of the matter is that there are several types of geometry solutions all being worked on at the same time. This is a time that is marked by ongoing experimentation and research into just what a 29″er should steer like; and quite frankly, it is not going to shake out anytime soon. Nor should it. The situation now days is a blessing and a curse. For one thing, it is a blessing in that we can now “tune our rides”. It is a curse in that now you have to think about this stuff. It is not a moot point like it was back in the earlier days of mountain biking when every hardtail had “NORBA geometry” and you just assumed it would handle like a 26 inch wheeled mountain bike “should” handle. No, now there are options to consider, and the wise 29″er shopper will be aware of these options going in.

Next post: Can you swap around forks and frames to acheive a desired result?, and other 29″er handling questions. Stay tuned!