An Experiment In Front End Geometry: Fork #3

The next fork up in the test is the Origin 8 Black Ops fork, (Which we are also going to be reviewing separately. Please look for an updated post on this particular fork coming soon!) Note: The Black Ops comes in two axle to crown lengths. We are using the shorter of the two offerings.

Origin 8 Black Ops fork on the test rig

I decided to see what might happen if I used a “short” fork with less offset than the radical Blackbuck fork. Here is how the numbers panned out with the Black Ops fork:

Head Angle: 74.2 degrees
Axle To Crown: 430mm (measured- claimed 420mm)
Offset: 43mm
Wheelbase: 42 inches
Bottom Bracket Drop Range (EBB) 76mm- 87mm
Approximate trail*: 65mm

Changes Made: Almost identical set up to the Blackbuck/Blackbuck combination. (Fork #1 in the test) Very minor deviance from that in spacer height to attain proper handle bar height and a touch further back with the saddle.

Handling Characteristics: With numbers so close to the fork in the “Fork #1” report, one might be led to think that the performance would mirror that test. Not so fast! Let us take a quick look at the trail figure here, which is 10mm different to the stable side of the first fork. Also, keep in mind that I had the lowest bottom bracket height with this Black Ops fork than I have had with any of the other forks. In my mind, these two factors weighed heavily upon the outcome.

Black Ops fork

The bike felt more stable in out of the saddle climbing, slow speed manueverings, and on high speed descents than it did with the Blackbuck fork. Not a whole lot, but definitely noticeable. Somewhere short of the feeling with the Switchblade in these regards though. The front end also lost that “pinned to the trail” feeling that the Blackbuck fork had, and I think alot of that was due to the shorter wheelbase and lighter fork weight with the Black Ops. In my opinion, this set up reminded me the most of what a great 26 inch wheeled single track bike felt like.Quick- but not too quick. Good manueverability and stable feeling on the down hills.

A Note On The Forks Ride: Please see the Origin 8 First Impressions post coming soon!

Final Thoughts: Again we see that tuning the ride with a different fork geometry can yeild a very different feeling bike. We see where wheelbase and bottom bracket height can also play a part in what the outcome will be. I again will say that this is the most 26″er-ish feeling set up so far. What might be surprising is how steep the head angle was and how short the fork was to get there! The bottom bracket height is a bit of a concern though, but it did yeild a very stable feeling in the turns and downhills. I might be willing to take that trade off for my trails.

Next stop: A little longer fork with a similar offset!

*The trail charts I used all gave slightly different answers and of course, your tire selection will also affect the trail figure slightly. Take my trail figures with a grain of salt. Your mileage may vary!


No Responses to “An Experiment In Front End Geometry: Fork #3”

  1. GreenLightGo Says:

    this may make a good 96er conversion fork for that Nashbar frame we discussed – continuing to enjoy the test updates!

  2. thad Says:

    Interesting reading and great timing. I’m not able to test out all these variations, but your reports and numbers are extremely valuable. This also helps figure out how a bike might handle that I can see numbers on in the internet, but can’t get ahold of locally to test ride.

    This and fork #1 sound closer to my kind of bike preference than the 29’ers I can readily throw a leg over.

    Keep up the good work.

  3. jason Says:

    Is the shorter fork a converted 26er or just a shorter 29er ?

  4. Guitar Ted Says:

    jason: The best answer is that it is a shorter axle to crown option for a 29″er wheel. J&B Importers, the distributor for Origin 8, markets it as an “either or” fork for 26 inch or 29 inch wheels. However; I’ve got to believe that with 43mm offset, Origin 8 was aiming squarely at 29″er riders. πŸ˜‰

  5. Doug Says:

    Hey Ted,
    Love this series! I’ve done a little of this myself but nowhere near as in depth or extensive. Glad to see you mention the need to change saddle position and stem length. I think many people over look this. Did you also compensate for the change in wheelbase induced weight distribution shift? After one of my fork swaps I forgot to compensate for the wheelbase and cg change and ended up with a much different than expected weight distribution. The most straightforward way would be actually measuring before and after weight distribution but in my haste I only compensated for the angle changes.
    What tire diameter are you using for trail calculations? All the formulae I’ve tried result in a far smaller trail value than you report. The only way I can reproduce your results is with about a 3.5-inch tire. Obviously this has no effect on your results but may impact someone trying to reproduce the same ride characteristics. I look forward to the rest of the series especially regarding suspension forks. I can grasp the rigid fork concepts well enough but the dynamics of constantly changing trail, angles, cg, weight distribution, weight transfer with a suspension fork is hard to grasp. I think my head might explode if I try to understand full suspension. I think it best to find what one likes and just ride ride ride. So thanks Ted for saving me from buying many more forks as I search

  6. Guitar Ted Says:

    Doug: I didn’t mess with considering weight distribution because you tend to compensate for that as a rider. Case in point: My going from the Blackbuck fork (#1) to the Bontrager fork (#2). I was all over the trail in the first quarter mile, but by the end of the loop, I had already assimilated any differences in handling/weight distribution that the different fork had imposed.

    That’s part of this whole experiment that I find most intriguing- the fact that a lot of the minutiae doesn’t matter since the human mind can adapt for it and overcome. What the outer boundaries of what your mind/body can adapt to, I am not sure, but I am finding out that for me, it is a lot wider range than I would have thought it to be.

    Whether or not I feel comfortable with certain set ups is an entirely different discussion. Weight distribution is a part of that, for sure.

    Most trail calculators ask for a radius or a diameter overall for the wheel/tire set up you are using, so I simply measured mine with a tape measure. Schwalbe Racing Ralph on a WTB Speed Disc rim.

    Thanks for your comments and compliments. πŸ™‚

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