Front End Geometry On 29"ers: Set In Stone

Since the 29″er was first a reality with the introduction in 1999 of the Nanoraptor in 700c size, geometry for the wagon wheelers has been in flux. It was commonly known that the bigger wheel would automatically increase trail figures with the geometry carried over from the smaller 26 inch wheels. So, to gain back the quicker handling that had been honed in to perfection on the 26 inch side, various things were hit upon to make 29″ers more like 26″ers, at least in terms of turning.

Fox  F-29
Gary Fisher Bikes use a Fox fork with a 51mm offset, but don’t bet on that becoming the “standard” for 29″ers.

Of course, in the early days only a custom rigid fork would address the front end geometry needs necessary to get a big wheeler to steer in a manner that most riders craved. There were some early attempts to change suspension fork geometry for 29″ers, most notably Marzocchi with the special forks made for Fisher Bikes. Trouble was, at the time, most suspension fork manufacturers were loathe to make new forgings to reflect the offset needs desired by what was deemed a small, niche market. So other means were employed to gain some steering quickness back for 29″ers.

Reba crown
Until the 2009 Reba’s came out, all Rock Shox 29″er forks sported a 38mm offset.

Most commonly, the head tube angles were steepened. Most of the time 72 degree angles were used, but some bikes went as far as a 73mm head tube angle. While this worked in theory, the bikes tended to make suspension forks bend backward along the length of the legs instead of activating the damper. Finally the level of sales was attained that made getting fork manufacturers to make new forgings a possibility. The first salvo was launched by Gary Fisher Bikes, just like they did in the early part of the decade. They convinced Fox to manufacture a 29″er fork with 51mm offset. But not only this, Fox decided to also sell aftermarket forks with 46mm offset. This was actually the bigger story, as it turns out.

With Fox on board with 29″er geometry, the other 29″er fork makers were put on notice to make changes as well. Manitou changed their offset in conjunction with Fox, and then for the 2009 model year, Rock Shox announced it too would shed the old 38mm offset from the 26″er days. What Rock Shox did sealed the geometry for 29″er front ends for the future.

2009 Reba Team
2009 Reba’s have 46mm ofset

Now with Fox, Rock Shox, Manitou, and the up coming Marzocchi 44 fork all having offsets nearly identical to one another, it is safe to say that the front end geometry for 29″ers is likely set. The time for experimentation is over. Gary Fisher Bike’s G2 geometry not withstanding, this is the future for 29″ers now. Sure, we’ll see things like through axles, tapered steer tubes, and longer travel forks down the road, but the offset issue for 29″ers is over.


The 2010 Marzocchi 29″er fork will feature a QR15 front axle and an offset nearly identical to the current crop of 29″er forks.

So, look for your 29″er to have some new fangled features in the future, but don’t expect too much change in the area of front end geometry anymore. Some folks will welcome that part with open arms, as just the mere thought of “offset”, “trail figure”, and “head angle” makes their heads spin. Others will lament the pasing of the “old geometry” for 29″ers, because they much prefer the way those early rigs handled. Whatever side of that coin you are on, one thing is for certain, this marks 29″er bicycles as being something that has come of age in the mountain biking world.

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No Responses to “Front End Geometry On 29"ers: Set In Stone”

  1. Willie Says:

    So is the new “standard” 70-71 degree head tube angle and 46mm fork offset, with a trail figure in the mid-70’s?

  2. Guitar Ted Says:

    Willie: I am sure head tube angles will vary a bit, but I still see plenty of 72 degree head angle 29″ers out there. Will it “standardize” there? Probably, I’m thinking, it will.

  3. grannygear Says:

    So, Mr. Ted…does it not seem like the increased head angle was a step towards quickening up things, and if the 38mm offset worked with that 72* angle, why keep that when a slacker 71* or less plays well with the increased offset forks? Economics?

  4. Guitar Ted Says:

    grannygear: The thing is, the perception was that a 72 degree head angle/38mm offset was deemed as “not enough” by lots of 29″er critics, so again, I do not see the average trail bike or hard tail veering away from 72 degree head angles too much. Some thought that the 72/38 combination was great, but those folks apparently were in the minority, or not heard.

    But again, we must also allow for companies that will develop their own geometry for marketing or specific use purposes. So you will see things going slacker, or maybe even steeper on occasion.

  5. grannygear Says:

    Odd. The last 26er I had was running a 69* ht angle and around 46mm of offset. Granted, the tiny wheels do change that up a bit, but it felt just right. Excellent trail bike.

    The Lev is likely 70* static with the higher than designed for 100mm fork. It could stand to be juuust a might faster every so often, but really it works very well with a 38mm offset Reba.

    The KM is very agile with a 72* ht angle and the over 40mm offset of the RST M29. It gets pretty nervous at speed over rough terrain but it still feels a bit slow when I need to turn fast.

    I don’t know for sure, but I do think that the entire bike has to be considered…the rest of the geometry, build, set-up. The numbers are not everything, sometimes I wonder if they are anything at all, but lets not let that get out to the world. The internet ‘discussions’ would run out of things to debate!

  6. Dirt McGirt Says:

    Crimalls. Just go out and ride for God sake…..

    JEEEEEEEEEEEEEEEEEEEEEZZZZ

  7. Guitar Ted Says:

    Hey Dirt! It’s winter up here. We gotta have something to chaw about while it’s too cold to ride and our trails are under the snow. 😉

  8. dan Says:

    Hi GT wondering if you know the specs for early marzocchi 29er forks for fisher bikes, I’m running a marathon 29 fork on my hi fi and liking the handling. thinking about the new reba fork to upgrade in future. i read your article on the 120mm reba great info once again. i still lean on old school geometry myself

  9. Guitar Ted Says:

    dan: I do not know the axle to crown off hand, but I can tell you that it has a 43mm offset.

  10. Dirt McGirt Says:

    Get on the trainer, son!

    And who says you can’t ride in the snow?!?! I grew up in New England, kid, you can’t tell me you gotta stay in all winter off the bike.

    But that’s one of the many many reasons I love Seattle. Mild weather!

    West side fo life!

    Nong!

  11. Cloxxki Says:

    I truly feel that discussion on this very site and MTBR have contributed in Fisher having the guts to set this al in motion. And it’s a good thing.
    Looking forward to seeing bike brands coming up with their own version of 29″ geometry.
    Has there ever reall been as much thinking and testing been done on geometry for MTB’s since the birth of it? It’s bringing us new and wonderful bikes to differentiate our riding experience.
    In Europe at least, it was at one point hard to find an XC hardtail with anything but 71/73 angles. How different it now is in 29″er land. From one tire in 1999, to multiple beliefs and approaches to geometrically design the bikes to fit it.
    Oh, and I feel like G2, which first hit Fisher’s 26″ bikes, was really thought up for 29″. Perhaps their 26″ers needed a new geometry update harder?

  12. Dirt McGirt Says:

    Umm… I really wouldn’t compare this site to MTBR.

    With all the drivel flying back and forth over there I’m starting to have doubts that the “R” stands for review. I think it stands for retarded…..

    The official forum for the MounTain Bike Retarded.

    And then there’s Pinkbike….

    That’s for another time.

    Peace be with you, my brothers and sisters.

  13. gin/fs Says:

    I ‘m riding a 2007 Paragon in Utah and the steering for me has been a little goofy-using Kenda small block tires front and rear with Stans juice-this spring will probbably go to a stronger tread-I had an accident this fall basic ride moving a liitle fast front tire slip flew over the front and broke an elbow big ouch*** this is my first aluminum frame so I am also thinking about going back to steel-so I am really paying attention to all this steering talk- any guidance, suggestions about my present fork, tires, etc. Thanks-George-SLC-UT

  14. Davidcopperfield Says:

    I wonder why 51mm wans’t the one offset to be engraved in stone? 51mm indeed yield a trail about 72mm like on XC 26ers. Why not make 29ers with exact trail numbers’ ranges like on 26ers?

  15. Guitar Ted Says:

    gin/fs: I think you would be much better served by a tire with some great traction. Think Nevegal, Rampage, or even a WTB Stout. I think it would transform your ride dramatically. Just a thought for ya.

    Davidcopperfield: Keep in mind that Fisher employs a slacker head tube angle to achieve a similar trail figure to a 46mm offset/72 degree head angle bike. Just a different way of getting there, really. That said, the slow speed maneuvering of a G2 bike is pretty phenomenal.

  16. Davidcopperfield Says:

    Yes, but suspension forks work better with slacker angles than steeper, don’t they? I would rather choose 71/51mm offset than 72/46mm combo.

  17. Guitar Ted Says:

    Davidcopperfield: To a “degree” <==ha! However, there is a point of diminishing returns. Fishers slacker head tube angle creates a shorter top tube, so we must look at the effects of front end geometry choices as they relate to the whole bicycle.

  18. gin/fs Says:

    GuitarTed-thanks*** for your input-I was changing front for sure-Are you saying both front and back-And I’ve been riding I think 2.1-Any comments about that-Thanks-George-SLC-UT

  19. Guitar Ted Says:

    gin/fs: I would seriously consider a 2.4″ up front and for the rear something more aggressive as well. Maybe a combination of Continental Mountain King 2.4/2.2 or Specialized The Captain 2.2 inch front and rear.

  20. Flatlander 59 Says:

    GT,

    I noticed on my Rockhopper 29 that Head angle is 70.5 degrees I’ll have to check out the offset on the RockShox Tora Race SL fork. All I know is it will turn quick when I need it to. Like I said too, on another post with the Swiss DT 470’s and FasTrack Control LK’s cornering braking control is there and tight as needed.

    Marc

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