Rear suspension sag?

[marks]

Hi

I just fitted a new rear shock and spring to my klr.

the sag before was 8cm
the sag with the new bits was 5 cm

I presume this means I have too much preload on the new setup?

except the actual ride hide with me on the bike hasn't changed - that is the unladen ride height has dropped 3cm which implies I don't have enough preload

I think the klr has about 200mm rear travel and 8cm is regarded as about right.

I am very confused

[ducatijim]

You like me Mark, no rides today?

The only variable in ride height( weight aside!) is preload, yes.

I'm far from competent here, but the greater the sag laden,( within reccomended range) the more compliant the ride should be.

I would have thought thou, that 8cm static was a bit much? How much sag is there loaded?

Sorry, prolly no help at all?

[marks]

You like me Mark, no rides today?

The only variable in ride height( weight aside!) is preload, yes.

I'm far from competent here, but the greater the sag laden,( within reccomended range) the more compliant the ride should be.

I would have thought thou, that 8cm static was a bit much? How much sag is there loaded?

Sorry, prolly no help at all?

nope - no rides today

bike maintenance day (always something to fix/unbend/replace)

thanks for the response

I whacked a bit more preload on so it sits a bit more stably on the side stand and I'll ride it for a while and see how it feels

cheers

Mark

[NordieBoy]

Usually around 15% static sag and 30% rider sag.

3-4cm static and 6-8cm rider.

Sounds like you've got a heavier spring now too?

[marks]

Usually around 15% static sag and 30% rider sag.

3-4cm static and 6-8cm rider.

Sounds like you've got a heavier spring now too?

oops - I only measured the difference between the bike sitting on its wheels and the bike sitting on its wheels with my fat bum on it - so I suppose I'm talking only rider sag (50mm - 25%).

and yes - of the 4 spring rates on offer I got the 3rd strongest one.

now I need to get out and do something bumpy and test it out

[warewolf]

oops - I only measured the difference between the bike sitting on its wheels and the bike sitting on its wheels with my fat bum on it - so I suppose I'm talking only rider sag (50mm - 25%).

Nope, that's the difference between static & rider sag... Padmei made this same mistake recently - must be a KLR feature!

Measure the free length, wheels off the ground so the suspension is topped out. Call this A.

Measure the length with the bike on its wheels, call this B. Static sag is A-B.

Measure the length with you on the bike in normal riding gear, call this C. A-C is rider sag.

The trick is, you set the preload to get the correct rider sag. The subsequent static sag tells you if the spring is correct. Too little static sag means the spring is too light, you've over-preloaded it to cope with the rider weight. Too much static sag means the spring is too heavy, you've backed off the preload too far.

I wouldn't worry too much about was it was with the old spring. Aim to get it correct on the new spring. Lots and lots of good stuff on the interweb about this.

[warewolf]

Try Teknik racing bike setup guides.

[ducatijim]

See Mark, I told you I didn't know much about this!!!!!

Good info.

[buggsubique]

vaguely related story ... my DRZ 400 stock spring was too light so I compensated by winding up the preload. Problem I found was it made the bike shite to ride downhill - esp gravel downhill roads. the geometry was all f*cked up and it was difficult to keep the rear under control. I did the sag equations and I should have had a heavier spring but I was too pezza and suffered for it...

[marks]

Nope, that's the difference between static & rider sag... Padmei made this same mistake recently - must be a KLR feature!

Measure the free length, wheels off the ground so the suspension is topped out. Call this A.

Measure the length with the bike on its wheels, call this B. Static sag is A-B.

Measure the length with you on the bike in normal riding gear, call this C. A-C is rider sag.

The trick is, you set the preload to get the correct rider sag. The subsequent static sag tells you if the spring is correct. Too little static sag means the spring is too light, you've over-preloaded it to cope with the rider weight. Too much static sag means the spring is too heavy, you've backed off the preload too far.

I wouldn't worry too much about was it was with the old spring. Aim to get it correct on the new spring. Lots and lots of good stuff on the interweb about this.

thanks Colin

I'll check it again tomorrow

[Eddieb]

Wanna do mine next? it's all black magic and voodoo to me.

[Frodo]

Try Teknik racing bike setup guides.

Very interesting. I've just used stock settings and seems to work for me. But perhaps I can do better. Anything for dual sport, i.e. between the road racers and motocrossers?

Thanks, Bob

[Woodman]

Tried setting up mine after the intiminatorerers and the raising link fitment and couldn't get any where near the percentages ww talked about. One would effect (affect) the other so I just set it up close and its definitely better (I think). It would be good to have a choice of springs and a decent shock to play with in the first place though.
Be interested in your thoughts after a decent hoon though marks.

[XP@]

oops - I only measured the difference between the bike sitting on its wheels and the bike sitting on its wheels with my fat bum on it - so I suppose I'm talking only rider sag (50mm - 25%).

I've done that too, and totally mucked everything up the preload in the process.

To fix it (with the advice from my suspension tech) turned out to be easy!

"Forget about rider sag - you cannot set it by yourself, also you are effectively setting it anyway when you adjust the pre-load"

So I re-set the pre-load to the mid point and the static sag to 25mm (about 15% of total). Fortunately this was damn near perfect all that was needed was a bit of hardening up (initially by 1/4 turn then I backed it off by 1/8th turn)

If you really get stuck then contact this guy: www.dukicperformance.com (he does bikes not websites) he is in Lower Hutt, and really knows his stuff. He re-built an "un-rebuildable" rear shock and installed cartridge emulators (plus a few other bits) for me. The emulators put in my front forks were perfect first time (and a bloody good price compared to others I was quoted).

[warewolf]

vaguely related story ... my DRZ 400 stock spring was too light so I compensated by winding up the preload. Problem I found was it made the bike shite to ride downhill - esp gravel downhill roads. the geometry was all f*cked up and it was difficult to keep the rear under control. I did the sag equations and I should have had a heavier spring but I was too pezza and suffered for it...

Very related story. Preload only fine-tunes your correct spring. The spring does the primary job of supporting the bike, damping is mainly there to control the spring. Don't have the correct spring? No amount of preload will fix it, and going to extremes of preload (over/under) can introduce worse effects than moderate preload on the wrong spring.

eg High preload on a soft spring makes the initial travel harsh but won't stop the suspension blowing through its stroke, whereas a stronger spring will be softer initially but firm up appropriately.

Very interesting. I've just used stock settings and seems to work for me. But perhaps I can do better. Anything for dual sport, i.e. between the road racers and motocrossers

Sorry that site is probably a bad example, I see it is mostly race-focused and a little more detailed - search for more, there is heaps online. But the principles are the same, refer Nordieboy's percentages listed earlier. Try google?


Don't forget these numbers are a starting point - like the clickers - so vary them to suit yourself. Eg as ducatijim suggests, setting the preload at the softer end of the suggested range gives a more compliant ride. But I strongly suggest if you don't really know what you are doing (ie all of us who aren't pro suspension ppl) that you start with the suggested settings, see what it feels like, and vary from there. Experiment - make one change at a time, go for a ride on a test loop, see how it behaves. Make another change - ride the same loop. Did that work better? Did it introduce ill-effects somewhere else in the loop? etc