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Adjustable travel forks
#1
Not sure how best to describe this!

So when you have a fork that's adjustable, say 140 to 100mm, does the overall fork length change by up to 40mm or is it just the amount it travels? Do you get what I mean?

I'm on about the overall length from the the bottom of the headset to the centre of the axle, does that change by 40mm from min to max?

Never owned adjustable forks, ta.

Lee.
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#2
The fork grows longer as you extend the travel
Keep it foolish...
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#3
The length of the whole fork changes.
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#4
Yep, axle to crown length would be reduced.  Personnally I wouldn't bother though as after experimenting with my old U Turn Pike's I don't think it makes any difference to climbing ability, and I always forgot to increase it back to full travel for the downs so I never bothered. I think the same about lock out too. You thinking of getting some?
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#5
Doesnt change a2c on Devilles with trc but quite a niche fork so...... Yes 99.8% of forks change their overall length. Treehugger is incorrect, lowering the front will aid climbing. U-Turn is not an on the fly adjustable system but it is handy to allow you to the run the same bike at different amounts of travel depending on your riding ie wind them out with more travel if doing downhill etc. Fox Talas system works ok but with added stichion due to the extra seals. Current Rock shox is now a 2 position setting like Talas so can be used on the fly

Consider very carefully if you need it. The extra weight/loss of performance/cost etc are not really worth it if its just to make climbing slightly easier. If you want fork length flexibility for a frame/bike then they can be a good idea although if you are thinking of running 100-140 forks on a bike, make sure it can use forks of that length without voiding the warranty
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#6
I have a vague recolection that the new rock shox dual position forks do something odd say 120/150 dual postion, flick to 120 and yes the fork lowers however if you lift the wheel off the ground it will fully extend back to 150 until compressed again, it doesnt actually stop it extending beyond 120. This would be fine for climbing but I dont think would work well if you wanted a bike fixed at 120mm for most of the time then 150 for playtime as regardless what it does to the compression stroke, its still going to be noticeable as it compresses back beyond its lower travel position

The above may be complete nonense, I just vaguely remmeber it when looking for some new forks which made me go for older u turn ones
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#7
Wow cheers guy's, super fast responses! You understood what I was getting at then.

Have considered them before but what I'm really getting at is if a bike frame is designed to use an adjustable fork length of 100 - 140 (Spesh Stumpjumper) it should work fine, geometry wise, with a fixed 120 fork?

Basically I've cracked my Lapierre frame which I'm in the process of sorting at the mo but if I don't have any luck I may buy a Stumpjumper frame and want to keep my 120mm forks.

Not really clued up on the geometry side of frames.
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#8
Breezer- I didn't state it dosn't make any difference, just personnally didn't notice myself.
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#9
"LeeI" Wrote:Basically I've cracked my Lapierre frame which I'm in the process of sorting at the mo but if I don't have any luck I may buy a Stumpjumper frame and want to keep my 120mm forks.

If you are dealing with Hotlines then good luck, it took them 4 months to fix my front wheel on warranty. I also emailed Lapierre nearly a month ago to complain about the service but they didnt even bother to reply. Needless to say it will be the last Lapierre I buy, no matter how good the bike.

Regarding forks, I would steer clear of adjustable travel (the exception being BOS forks) mainly because of the performance loss usually inherent in this sort of fork. Also its not that difficult to adjust your climbing technique to overcome longer forks anyway.
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#10
The Stumpjumper is probably designed to be run at 140mm most of the time. Running 120mm forks will be okish, the head angle will be a bit steeper so it will steer quicker and be slightly twitchier at speed. The bottom bracket will be 15mm or so lower as well.

Most important thing if planning on using new forks is whether the steerer tube is long enough or not. Some frames are short headtubes so if the steerer has been cut short with little to no spacers under the stem then flush on top, it would not be long enough for a frame with a longer headtube. You would also need to run the stem higher than current requiring more steerer length if you wanted to retain the stock bar height of a stumpjumper but stem height is a personal thing and you can always get higher rise bars etc
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