How much front fork pre-load?

M

motopsycho87

New member
Herro everyone!

Just wondering, what is the 'optimal' amount of pre-load for my shiver 45's, when I've fitted the correct springs for my weight, I know, I should get 25% of travel with my ass on it and adjust until I get it, but roughly, what pre-load should I have? I'm pretty sure the person riding the bike before me was a fat bastard and ran a 6.1 spring in the rear and 5's up front, I re-used the front spacers giving approx 25 - 35mm pre-load, which seems a bit much for me...

Too much caffeine...
 
Just set my forks to that range, they were at 20 :o lol.

0.45 in one and 0.48 in another, fingers crossed this makes it soak up the little bumps a bit easier, been getting a horrible juddering through the bars :(.
 
Mmmm

Well, using your old springs Ive found a great setting at 35mm preload ?

It has transformed the old girl, no more washing out, headshake or harshness, rode today in a tricky woodland with loads of roots and G'outs Awesome

Ive also gone to 10wt oil set at 110mm

Not going to mess anymore, perfect
 
There is no right or wrong. Just what works and what doesn't, and to a large extent that will depend on the rider, and where they are riding.

For me, if I can't get the bike to sit up in the stroke with around 5mm preload it indicates I am undersprung. Its essentially the same as cranking a load of preload onto a shock spring to try and make up for one thats too light.

From what I have seen with these valve stacks it appears they run too much free bleed which gives the initial action very little valving at all, and the additional preload is to stop it falling through. I'd rather a heavier spring, less preload, and less bleed shims which will allow the valving and spring to work together more.

Remember with preload, all you are doing is increasing the amount of force required until the spring begins to move.
 
32:1 said:
Well, using your old springs Ive found a great setting at 35mm preload ?

It has transformed the old girl, no more washing out, headshake or harshness, rode today in a tricky woodland with loads of roots and G'outs Awesome

Ive also gone to 10wt oil set at 110mm

Not going to mess anymore, perfect
Click to expand...

Good to hear! Those are the conditions mine doesn't feel great for atm :(, great on big landings etc, but horrible on roots and rocks.

Jakobi said:
There is no right or wrong. Just what works and what doesn't, and to a large extent that will depend on the rider, and where they are riding.

For me, if I can't get the bike to sit up in the stroke with around 5mm preload it indicates I am undersprung. Its essentially the same as cranking a load of preload onto a shock spring to try and make up for one thats too light.

From what I have seen with these valve stacks it appears they run too much free bleed which gives the initial action very little valving at all, and the additional preload is to stop it falling through. I'd rather a heavier spring, less preload, and less bleed shims which will allow the valving and spring to work together more.

Remember with preload, all you are doing is increasing the amount of force required until the spring begins to move.
Click to expand...

I haven't gone down the route of a re-valve yet as I don't know whether it's been done before and want to get all other variables correct before I try. My problem was that it felt too harsh going over roots etc and even slight bumps in road surface, but if I opened the compression up too much to alleviate the symptoms, the front end would then wash out on fast cornering off-road. So my theory was, more compression damping, less pre-load, what d'ya think? There is very little stiction in the forks, and apart from increasing the high speed compression (surely the extra free bleed acts the same?) I can't think of another option?
 
Easy enough to take a heap of preload out and then adjust the clickers. You'll soon know if its better or worse.. or you may find it sits too low in the front under its(and/or your) weight.
 
OK
I rode the kentenduro Sunday at Exedown, wooded hillside with tight technical sections, roots, climbs and drops, with one fast field section, approx 1 mile skirting fields and quite fast

The bike was awesome with great feedback and not one washout, good news for me ;)

One issue I did have was a touch of headshake on one fast section :eek:

It was just cresting hill and although not wide open, I was trailing the throttle. It happened every lap in the same place, not dangerous but a little bit of a warning and made me slow down a bit as Im a bit to old for reckless abandon ;)

Not sure how to attack this problem, forks were flush with top triple clamp, 115mm of rear rider sag. bike feels plush and faultless everywhere except that one area, none of my buddies had that problem there ?

Any ideas on what to adjust ??

Chris
 
The suspension bible seems to think you should check all your bearings, chassis straightness etc


Now I'm a bit concerned that my springs are too wimpy, gonna chuck in the other 0.48 and keep the low preload. High preload on 0.465 still tucked
 
Im going to add a touch more rear sag, say 5mm first

When you say the front tucks, do you mean it pushes the front away midcorner, or as we say, washes out !

If so mine did that until I went up on springs and preload, mine (I think) was far to soft for the first part of the stroke and that caused it to feel harsh, as the fork was working in the mid to hard part of the valving to start with. I even tried 3 different tyres as I thought it was a tyre issue ?

I confused harsh with a too soft set up. Honestly, since I preloaded those springs it feels like a different bike, the front end is on rails and still plush enough to ride over off camber roots. I also went from 5wt oil to 10wt, that I think helped the rebound side of things ?

The shivers do work as Ive found out, as as stated earlier, they must be far to soft/open valved in the early part of the stroke, relying on the latter part ?

If I experience more headshake I'll get more involved, but right now these and this bike feel great.

Chris
 
By tucks I mean I'm oversteering, the suspension was composing too much creating almost a mini endo situation. Still waiting on my crank so can't test anything :(
 
Yep. Washing is front pushing outwards/understeering. Tucking is it trying to bury itself under the bike/oversteering. I find this generally relates to rebound where if the front is coming back too fast it'll want to sit up and push, and too slow will want to bury down and tuck. When its just right it'll track like its on rails. *given that its not already way in the stroke from diving excessively under brakes, and that the general front to back geometry and damping are balanced.

In my opinion, and that is all that it is, is that by adding a load of preload you have worked around what appears to be a valving issue caused by excessive bleed. Its great that its working better than it was, but you may find a heavier spring with less preload, and then valving the mush out will be even better. Quite often with suspension its only the best you've had that makes you realise what they can be.
 
All guides I've read so far seem to think that I should go up on the spring rate so I'll do that and keep the pre-load as low as possible for now and see if that removes the harshness I've been getting.

Crank returns tomorrow so I can start the rebuild :D!!!!
 
Took the bike out yesterday with 0.465 up front and f all preload, very soft over roots etc but felt too wallowy in corners and tucked. Just changed to 0.48 up front, same preload, about to go to go for a play!
 
I found the std spring right for me but took out high speed compression so it didn't lock up so bad over roots and stutter bumps. Made a big difference over roots and can feel it riding my mates 07 from my own.

But it still beats me up hence $200 worth of YZ SSS forks are now slotted in the headstock as of today awaiting some welding to steering stops. Hopefully this will sort it as I love the rest of the bike.
 
I found the 0.48 handle a lot better, but are slightly harsher of breaking bumps etc, so I might back off the compression, or perhaps go with a thinner oil to get some of that plushness back. Feels much better than with the 0.465 option, far more balanced and planted, even if my race sag is a little on the low side :rolleyes:
 
You could also consider one of each springs which will give you an effective rate between the two.
 
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