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Old 07-20-06, 09:40 AM   #1
Peek the Geek
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Question re. Forks and Travel

All other things being equal, will an 80mm travel fork feel any different than a 100mm fork (before reaching bottom-out, of course)?

I'm thinking of replacing my current 80mm fork, and one of my choices is whether or not I want to stick with 80mm or go up to 100mm. I'm wondering, though, if the two forks would feel any different through the first 80mm of travel.

I currently only bottom out a few times a ride, so 80mm is enough. Would I gain anything at all from going with 100mm? Or should I stick with 80, which would be lighter and not alter my bike's geometry?

(for what it's worth, the forks I have in mind are the Fox F80RLT and the Fox F100RLT)
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Old 07-20-06, 09:52 AM   #2
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since the two forks look equivalent (going by model, couldn't find pics?), the 100mm will be plusher than the 80mm.

i suspect that the weight is nearly the same, i wouldn't be surprised if it is practically the same fork internally adjusted to 80 or 100...no?

with the above said, i would take a high end 80mm fork over a low end 100mm fork any day...but since you stated they are the same model except length...

most will tell you 20mm is nearly negligible for geometry changes. i didn't notice a 20mm difference really on my homegrown.
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Old 07-20-06, 10:01 AM   #3
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Originally Posted by mx_599
since the two forks look equivalent (going by model, couldn't find pics?), the 100mm will be plusher than the 80mm.

i suspect that the weight is nearly the same, i wouldn't be surprised if it is practically the same fork internally adjusted to 80 or 100...no?

with the above said, i would take a high end 80mm fork over a low end 100mm fork any day...but since you stated they are the same model except length...

most will tell you 20mm is nearly negligible for geometry changes. i didn't notice a 20mm difference really on my homegrown.
Looking more closely at the specs, I'm betting that you're right. There's only a claimed 20g difference in weight, so they probably are the same fork with the only difference being internal adjustment.

So what do you mean by saying the 100mm will be plusher? Is it really going to feel different than the 80mm in the first 80mm of travel?

Sorry if these are pretty basic questions, but forks are the one part of the bike I really don't know much about.
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Old 07-20-06, 10:43 AM   #4
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Originally Posted by Peek the Geek
Looking more closely at the specs, I'm betting that you're right. There's only a claimed 20g difference in weight, so they probably are the same fork with the only difference being internal adjustment.

So what do you mean by saying the 100mm will be plusher? Is it really going to feel different than the 80mm in the first 80mm of travel?

Sorry if these are pretty basic questions, but forks are the one part of the bike I really don't know much about.
no prob at all. the only reason i state that it will be plusher is for the fact that nearly any suspension design, regardless of air/spring/whatever, is going to become "stiffer" in the final part of the stroke. in fact, sometimes you can feel the effect far sooner than the final part of travel. for example, if a given bump causes 50mm of travel, the 80mm is going to be nearing that zone more so than the 100mm fork.

technically, you will have also have more sag on the 100mm fork. this will allow the wheel to "flow" better with the contours of the ground, if you will. like i said, technically ...sag on these short travel forks is kind of like due to stiction etc, you would be hard pressed to make that accurate of a sag adjustment on a HT bike. for the most part, just make sure it sags a little and is not topped out if you can while sitting on it.

it would probably be worth your time to hear straight from the horses mouth and contact fox to find out whether or not this is a simple internal spacer adjustment or not before you buy. it might impact your decision. say if you get the 80mm (usually the shorter one would have the spacer) fork, you might be able to take the spacer out and suddenly have 100mm!! then you can try both, that would be awesome.

but you need to find out for sure. i am only speculating.

but this is similar to what i did with my Reba. i think i went from like 100mm to 85mm with the simple addition of a plastic spacer that came with the fork.

you might be able to down load a service manual from fox and see if there is an exploded view of parts or any mention of internal travel adjustability on that model.

Last edited by mx_599; 07-20-06 at 10:53 AM.
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Old 07-20-06, 10:54 AM   #5
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OFF-TOPIC ALERT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

This question wasn't asked but it's an important consideration when choosing your fork:

Putting a 100mm fork on a bike that was designed around an 80mm fork will affect the way that the bike handles. The head angle will be slacker with the taller fork. Steering will be more sluggish at slow speeds but more stable at higher speeds.
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Old 07-20-06, 11:30 AM   #6
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Originally Posted by Hank Rearden
OFF-TOPIC ALERT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

This question wasn't asked but it's an important consideration when choosing your fork:

Putting a 100mm fork on a bike that was designed around an 80mm fork will affect the way that the bike handles. The head angle will be slacker with the taller fork. Steering will be more sluggish at slow speeds but more stable at higher speeds.
Thanks, Hank. I'm actually aware of how the longer fork would slacken the head tube, but it's my understanding that the difference would be negligible. I have e-mailed Fox, though, to see what the difference in fork length would be between the two forks.

In fact, the current year's model of my bike (Marin Pine Mountain) is now spec'ed with a 100mm fork---very interesting. My '04 model has the exact same geometry and was spec'ed with an 80mm fork.

EDIT: Now that I rethink my post, I'm probably wrong. The current Pine Mountain frame would probably have been altered to acheive the same geometry with a longer fork. In any case, the 20mm difference still shouldn't effect the handling too much.

Last edited by Peek the Geek; 07-20-06 at 12:34 PM.
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Old 07-20-06, 11:35 AM   #7
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mx_599,

Thanks for clearing that up. Makes perfect sense.

Fox's online manual states the following: "An F100 can be lowered in travel to 80mm, but an F80 cannot be increased to 100mm." And yes, this is done with the addition of a travel spacer.

Given that, and the fact that Marin now specs this bike with a 100mm fork, I think I'll go with the F100 if I do decide to upgrade to a Fox (which now calls this model the F100RLC, since Low-Speed Compression adjustment has been added for '07).

Thanks for the replies.
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Old 07-20-06, 01:04 PM   #8
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Thanks, Hank. I'm actually aware of how the longer fork would slacken the head tube, but it's my understanding that the difference would be negligible.
I've got a RS Psylo that adjusts from 80mm to 125mm. (my bike originally came with an 80). I'd say the difference between riding at 80mm and 100mm (where I usually keep it) is more than negligible. Certainly not a dealbreaker, and you may prefer the longer fork, but there is a definite difference for me. YMMV.
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Old 07-20-06, 01:08 PM   #9
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Originally Posted by jalexei
I've got a RS Psylo that adjusts from 80mm to 125mm. (my bike originally came with an 80). I'd say the difference between riding at 80mm and 100mm (where I usually keep it) is more than negligible. Certainly not a dealbreaker, and you may prefer the longer fork, but there is a definite difference for me. YMMV.
Very good to know. How would you describe the difference in ride?
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Old 07-20-06, 04:46 PM   #10
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Very good to know. How would you describe the difference in ride?
"Steering will be more sluggish at slow speeds but more stable at higher speeds"
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