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PostPosted: Sun Sep 18, 2011 10:50 pm 
retrobike rider / Gold Trader
retrobike rider / Gold Trader
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Location: South Buckinghamshire
In my early bike days, suspension forks were but a figment of my dreams. Now, well things are different and I've got Fox forx on two of my bikes.

The issue? I'm clueless.

Set-up is a mystery
Maintenance gives me cold sweats.

I'm not being lazy and have spent many a minute reading up/ researching but I don't understand what each bit does, nor what to do (after fitting / before or after rides).

My reference manual has been....

http://www.foxracingshox.com/fox_tech_c ... _32_en.pdf

I hoping I'm not on my own here and there's others in the same boat.

If you could spare 5 mins to give a man some pointers, you'd be very kind.

thanks.

TL


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PostPosted: Sun Sep 18, 2011 10:54 pm 
retrobike rider / Gold Trader
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These are the ones on my zaskar

Image

And my specialized epic. (for 80mm travel do they look low/compressed to you?)

Image


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PostPosted: Mon Sep 19, 2011 1:39 am 
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Location: Antwerp, Belgium
Okay ...

Take a cup of coffee/soup/soda first, because this is going to be a reasonably long post.

Basically the suspension depends on 3 things : preload, bound and rebound. We'll go through them one at a time.

-----

Preload is basically the spring's tension (or the air pressure in case of air suspension). Ideally this must be set to a level where the fork compresses around 20% when you are on the bike.
This is important because it allows you to have 80% of your forks' travel for bumps. The other 20% is for situations where your front wheel would normally be lifted clean off the ground.

To set this up, you need to know the forks' travel (80, 100, 120mm). put a ty-wrap or rope around one of the forks' upper legs, tighten it securely and slide it all the way down.
Get on the bike (lean with your ellbow against the wall if necessary) and sit like you normally would. Then get off again and extend the forks completely. Measure the distance between the ty-wrap/cord and the fork's seal. Adjust if necessary.

That should give you a good starting point. If you notice the suspension bottoms out too often or never compresses fully, you may want to adjust the preload until it suits your preferences.

-----

Bound is the inward damping. That is meant to slow down the compression of the forks. There is no formula for that, but there are some guidelines.
Fast/low bound means that the forks can contract fast, whereas slow/high bound means the movement is slowed a lot.

Basically the front wheel will move up when it hits a bump. The bound is meant to slow that down as much as necessary.
If the bound is too fast/low, the front wheel will continue its upward movement and lift itself off the ground, meaning you don't have control over the front wheel.
If the bound is too slow/high, the forks won't compress fast enough and the entire front end of the bike will be pushed up. It stands to reason that this also has a negative influence on the handling.

As for how to set it, the optimal value depends on the terrain, the speed and your driving style. Basically you'll need to learn how to feel what the forks are doing.
Once you get a feel for them and understand what's going on, you can adjust to your liking.

-----

When the fork is compressed due to a bump (or rock, or branch or whatever caused the compression), the spring (or air pressure) will cause it to extend again.
Rebound is the setting that slows down this process. It's just as important as the bound and unfortunately you also need to feel it work and understand what the bike is doing before you can successfully adjust it.

Too little rebound damping will cause the forks to extend too rapidly, causing the pogo-effect of older forks.
Basically the fork extends too fast and the entire front end of the frame is lifted a bit. Once the forks are extended, the frame will drop again and this will compress the fork again (not as much as before tho). It can feel like a bouncy ride.

Too much rebound damping will cause the fork legs to extend too slowly. This will cause the front end of the bike to drop a bit after a bump, and can also mean that the forks can still be extending at the moment of the next bump, which means you have less travel to soak up that bump.

As with the bound setting, the correct setup depends on the terrain, the speed, your driving style, etc.
There is no set formula for this and you really need to test it yourself by trial and error.

-----

I know it's a lot to read, but I urge you to read it two or 3 times. Read it slowly and take the time to understand it.

There's one more thing you need to understand, and that's the following bit :
While suspension set-up may have an effect on the bike's grip and behaviour, don't expect to become a better driver once it's set up properly. Ride a lot and improve yourself first.
Once you can feel what the front wheel is doing, you can start setting the bike up. At that point you'll really feel the difference of any adjustment to either setting.

If you're still working on your own skill but know someone who knows how to set up forks (and has a similar weight to you), ask him/her to set them up.
The resulting setup may not suit you 100%, but it'll probably be a lot better than a default setup.

-----

As for maintenance of modern forks, I prefer to leave that to my local bike shop.


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PostPosted: Mon Sep 19, 2011 7:48 am 
Old School Grand Master
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Joined: Tue Oct 19, 2010 9:55 am
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Location: The land of Lea & Perrins
The red dial on your Fox's is for the REBOUND damping. Set it slow enough so that the fork does not bounce back like a pogo stick when you compress it, but fast enough so that it can cope with rapid, successive bumps. I'd suggest finding a small section of track/pavement/road with a few successive small bumps and fiddling with the rebound until you find a setting which suits you. No setting is 'right' or 'wrong'.

The blue dial on your RLCs (on your Zaskar) is for COMPRESSION damping. This controls the spring rate. Too much compression damping and you will not get the full amount of travel from your forks as they will 'ramp up' as they go through their travel. Too little damping and you will be able to bottom the forks out too easily. Again, experiment with it. No setting is right or wrong!

The blue lever on the forks is the lockout. Turn it one way to lock the forks (so they're like rigid forks), and turn them the other way to unlock them.

The blue cap on the other fork leg hides the air valve (I think). Unscrew this cap and you should see the valve. Attach a shock pump to it to add/reduce air pressure. Check out the owner's manual for the forks to see how much air to put in for your weight.

I usually put a little more air in than is recommended for my weight, as I like a slightly firmer fork.

Simple! ;)
Have fun:)


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PostPosted: Mon Sep 19, 2011 8:13 am 
retrobike rider / Gold Trader
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Both. Thank you. Practical and theory! Kind of you both to take the time.

I'm going to swot up and then do some experimenting.

I've never set the forks up for sag, which I'll prioritise. Then work on the damping and rebound.

What's a blow-out valve? I think both forks have one on the base of the fork leg.

Cheers TL


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PostPosted: Mon Sep 19, 2011 9:03 am 
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Location: Heathfield, East Sussex
The blow-out valve is there to protect the fork seals and internals, it releases the internal pressure above a certain level if you, say, hit too big a bump too hard, or attempt a Danny MacAskill style drop-off without the recovery skills! :wink:


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PostPosted: Mon Sep 19, 2011 1:25 pm 
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Location: Antwerp, Belgium
You're welcome.

By the way : Next time you go anywhere near that Specialized, check the front disc for a rotation arrow. I'm not 100% sure, but normally discs with such "spokes" are mounted the other way around.

Like this :
Image

There have been a few cases where the discs were mounted the wrong way around, which caused them to fold and lock the wheel completely.


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PostPosted: Mon Sep 19, 2011 1:28 pm 
East Midlands AEC
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Location: Derby, UK
[moved to correct section]


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PostPosted: Mon Sep 19, 2011 8:11 pm 
retrobike rider / Gold Trader
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Raging_Bulls wrote:
You're welcome.

By the way : Next time you go anywhere near that Specialized, check the front disc for a rotation arrow. I'm not 100% sure, but normally discs with such "spokes" are mounted the other way around.

Like this :
Image

There have been a few cases where the discs were mounted the wrong way around, which caused them to fold and lock the wheel completely.


Thanks will go and check later.


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PostPosted: Mon Sep 19, 2011 9:58 pm 
retrobike rider / Gold Trader
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Joined: Tue Apr 20, 2010 11:29 pm
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Location: South Buckinghamshire
trickylad wrote:
Raging_Bulls wrote:
You're welcome.

By the way : Next time you go anywhere near that Specialized, check the front disc for a rotation arrow. I'm not 100% sure, but normally discs with such "spokes" are mounted the other way around.

Like this :
Image

There have been a few cases where the discs were mounted the wrong way around, which caused them to fold and lock the wheel completely.


Thanks will go and check later.


Just checked and for the bloody life of me I can't see any arrows suggesting direction. There's no markings on the discs of any type whatsoever. Not even branding.

What should I do?


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