Basic fork set up questions

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danlightbulb
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Basic fork set up questions

Postby danlightbulb » Tue Dec 18, 2012 13:36 pm

Hi all,

I have never set up my rockshox recon fork properly (100mm travel).

I recently looked at it and discovered I have the preload set quite high. I don't know why but I did find myself always tweaking it up one when out on rides. I think this may be due to the fear of bottoming out the fork when dropping the front wheel down rocks / steps etc. Am I correct in thinking that turning the preload UP (+) stiffens the fork? How does one get around having a nice soft feel to absorb trail bumps but a firmer feel for when the front drops heavily down a rock or step etc? I weigh 70kg.

The second thing is the rebound damping. The knob on the underside of the fork seems to turn 180 degrees in total. I have it set in the middle and its always been like that. I'm not really sure what turning it up or down would do.

Thanks
Dan

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The Rookie
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Re: Basic fork set up questions

Postby The Rookie » Tue Dec 18, 2012 13:51 pm

Turning the preload plus moves the upper spring seat down and raises the front, it doesn't stiffen the fork (spring) as it has one spring rate which isn't changed. You can't get both of the attributes you describe from your fork.

Turning the rebound adjuster +ve will slow down the time it takes fro the fork to rebound, turning it negative speeds it up, you should aim when doing a step up (say a low kerb without lifting the wheel just riding up it) for the fork to return to it's original static ride height as quickly as possible with only a small overshoot, if in doubt leave it in the middle.

Plyphon
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Re: Basic fork set up questions

Postby Plyphon » Tue Dec 18, 2012 14:15 pm

preload adjusts how much the fork is compressed when the rider is in a normal riding position (attack position) - Adjust this for your weight so when stationary in the attack position you get 20% - 25% sag.

To increase fork stiffness you will need a stiffer spring.

The rebound controls how much dampening you have on the fork returning to full length after being compressed. More rebound - more dampening - slower return. Having it in the middle is a good start, however if you feel the fork is packing down into the travel through multiple hits then you'll want to turn it down (toward the rabbit/hare). I like very little rebound as I don't like the feeling of the fork sitting below my 25% sag setting for very long - other people like more :)

danlightbulb
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Re: Basic fork set up questions

Postby danlightbulb » Tue Dec 18, 2012 16:00 pm

So the preload doesnt do anything for stiffness whatsoever?

Its simply for setting the right starting position? So my feeling that increasing the preload made fork harder to move, and therefore harder to bottom out, was wrong then.

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The Rookie
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Re: Basic fork set up questions

Postby The Rookie » Tue Dec 18, 2012 17:40 pm

danlightbulb wrote:So the preload doesnt do anything for stiffness whatsoever?

Its simply for setting the right starting position? So my feeling that increasing the preload made fork harder to move, and therefore harder to bottom out, was wrong then.

It doesn't increase stiffness at all...

It will increase the effort required to make it move at the top of it's travel as you have to apply enough force to overcome the pre (as in before it compresses) load (err...well load!), after that it will change the load v point plot, so if you change sag by 10mm from 30 to 20mm then the load at 20mm compression will be the same as it used to be at 30mm, but the stiffness (the amount of load to change compression by a set amount) hasn't changed, this is set by the spring rate, expressed in force/deflection so pounds per inch or Kg per cm etc etc.

danlightbulb
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Re: Basic fork set up questions

Postby danlightbulb » Tue Dec 18, 2012 18:01 pm

Thanks.

I never noticed the fork moving up and down as i adjusted the preload dial before. Is it a very marginal movement?

Thanks
Dan

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Re: Basic fork set up questions

Postby The Rookie » Tue Dec 18, 2012 18:05 pm

It doesn't move up or down, that's why it's aclled pre-load, load on the spring before compression in use, there is some there at minimum and then you add more by moving the spring end seat, but the rebound stop will stop the fork lengthening.

danlightbulb
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Re: Basic fork set up questions

Postby danlightbulb » Tue Dec 18, 2012 18:34 pm

Thanks for the knowledge.

So I'm still wondering, the preload means that its harder to get the fork moving but when it does finally move it will behave the same no matter what the preload setting? So does this mean that it is harder to bottom out a fork with a higher preload setting or not, and if so, should this be a consideration in the set up or am I chasing red herrings.

Thanks

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bennett_346
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Re: Basic fork set up questions

Postby bennett_346 » Tue Dec 18, 2012 18:35 pm

If i'm understanding correctly preload adjust does nothing except change where the fork sits in it's travel at base load? If that's the case why do we run any sagged travel on coil forks? Surely you'd want the most amount of useable travel.

Though i'm guessing i've simply misunderstood.

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supersonic
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Re: Basic fork set up questions

Postby supersonic » Tue Dec 18, 2012 18:52 pm

Preload is added by winding the spring down in it's housing ie the stanchion leg. This creates a force that you have to overcome when you get on the bike hence the fork will sag less if more preload is applied.

The actual spring rate does not change. However if you are repeatedy unloading and loading the fork it may feel as if it is softer ie if sprinting out of the saddle. Less sag means more available travel and actually does make it slightly harder to bottom out. But only because you may have 80mm of travel vs 75 mm (after sag).

The adjuster is there to make very fine adjustments to sag and ride height.

danlightbulb
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Re: Basic fork set up questions

Postby danlightbulb » Tue Dec 18, 2012 19:01 pm

supersonic wrote:The adjuster is there to make very fine adjustments to sag and ride height.


Aah this might be what the problem is. I previously thought that the preload adjuster makes noticable changes to fork behaviour, which is why its then confusing when I'm out on the trail and not really being able to notice any difference when I change the setting.

Plyphon
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Re: Basic fork set up questions

Postby Plyphon » Tue Dec 18, 2012 21:59 pm

bennett_346 wrote:If that's the case why do we run any sagged travel on coil forks? Surely you'd want the most amount of useable travel.


Because you want the fork to be able to extend into holes in the ground to maintain traction as well as absorb bumps to keep the wheel on the ground.

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RyanMK43
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Re: Basic fork set up questions

Postby RyanMK43 » Thu Dec 20, 2012 23:02 pm

Hi guys, sorry to hijack the OP but my recon silvers (coil) have just started to feel really soft, like when i am out of the saddle climbing up hill it seems to eat through its travel way to easily than what it used to be like and nearly bottoming out, i have the sag set up to about 25%. What would be the course of this? Thanks

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cooldad
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Re: Basic fork set up questions

Postby cooldad » Thu Dec 20, 2012 23:07 pm

New? Probably just the seals loosening up so less stiction. Try less sag - 20% or so. .
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RyanMK43
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Re: Basic fork set up questions

Postby RyanMK43 » Thu Dec 20, 2012 23:08 pm

No, they are just over a year old

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cooldad
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Re: Basic fork set up questions

Postby cooldad » Thu Dec 20, 2012 23:12 pm

Been eating lots of pies?
I don't do smileys.

There is no secret ingredient - Kung Fu Panda

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RyanMK43
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Re: Basic fork set up questions

Postby RyanMK43 » Thu Dec 20, 2012 23:18 pm

No comment.... lol. No im still the same weight as i was before

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The Rookie
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Re: Basic fork set up questions

Postby The Rookie » Fri Dec 21, 2012 11:17 am

Fitter and putting more force on the pedals? - or maybe an issue with the compression or rebound damper so it's bouncing more.

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RyanMK43
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Re: Basic fork set up questions

Postby RyanMK43 » Fri Dec 21, 2012 11:59 am

nope same leavel of fitness as before, so maybe it could be to do with your second suggestion do you think?

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supersonic
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Re: Basic fork set up questions

Postby supersonic » Fri Dec 21, 2012 12:52 pm

What sag are you getting now?


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