Help Setting Up Front Forks

iLukeKendall

Hi all,

So I'm kinda new to MTB, and bought a 2013 Trek Mamba about 4 months ago. It came with a RockShox XC32 (Coil Spring), and since owning it I've not been completely satisfied with the fork - it seems very stiff and doesn't seem to absorb much at all.

The fork allows for two adjustments;
1) Rebound - Adjusted by turning a dial under the right fork towards either a tortoise or a hare.
2) Preload - Can be loosened or tightened.

I have tried adjusting these but I don't really now what I'm doing and haven't seen a massive difference (not that I've extensively tested different settings).

I mainly ride across open moorland which can be quite rocky. At the moment it feels almost as if its locked out all the time, even when it's not (although it will budge if I stand up and start bouncing the fork).

I was wondering if anyone could please offer me some advice on how I should best set this up for my weight/body size, as I have no idea! Should I have the rebound set to the hare or tortoise? Should the preload be loose or tight?

I'm 18, around 6ft tall and weigh around 10st 11lbs, or 69kg (slim build) in case that helps at all!

Thanks a lot for reading and for any suggestions!

nicklouse

preload sets the SAG. you want about 20%
rebound controls the speed that the fork extends. you should just be able to pick the bike off the ground before the fork fully extends from compressed.

that is all you have to play with.

iLukeKendall

nicklouse wrote:

preload sets the SAG. you want about 20%
rebound controls the speed that the fork extends. you should just be able to pick the bike off the ground before the fork fully extends from compressed.

that is all you have to play with.

Thanks for the reply. With regard to the SAG, should this be 20% from when it's fully loose or fully tight?

supersonic

Whatever it takes to achieve that amount of fork sag when stood on the bike.

iLukeKendall

supersonic wrote:

Whatever it takes to achieve that amount of fork sag when stood on the bike.

Sorry, I'm being completely dumb here - does this mean how much it compresses when I'm stood on the bike? So it should compress by about 20% when standing?

cooldad

Yes.

plasma_man

When sitting on it in a normal riding posture.

supersonic

No, standing in attack position!

iLukeKendall

Thanks for all the advice - I'll try some different settings tomorrow.

I have been doing a bit more research and came across this: http://cdn.sram.com/cdn/farfuture/w-Vgi ... _rev_c.pdf

According to that guide, for my weight I should have a 'yellow' soft coil - the fork came with a 'blue' firm coil. Would this make much difference?

supersonic

Possibly, see what measurement you get.

iLukeKendall

supersonic wrote:

Possibly, see what measurement you get.

Sorry, by this do you mean the sag measurement? What would I be looking for to decide whether the coil is too stiff?

I'm sorry for my stupidity - I've fallen in love with riding but I'm slowly trying to get my head around all the mechanical stuff.

cooldad

If you can get enough sag the spring will be ok. If not you need a softer one.

The Rookie

Measure sag as follows....
Measure exposed length of upper stanchion with no weight on bike.
Measure exposed length of upper stanchion with you on the bike in the 'attack position' get someone else to do it, you can't do it yourself.
Correct nominal travel by nominal sag (so 100mm travel, 20% sag is 20mm) and see if that is the reduction in stanchion length you got, if it sagged too much add preload, not enough, take it off.