rear spring weight

[Taffy]

i weigh 200lb & the rear spring is a 5.5kg which i'm now thinking should be a 5.75kg for enduro racing.

i sit in a corner & hit the bottom of a rut & wait to be launched out the saddle. i've had the unit revalved & the compression is an improvement but i'm still going to the 17/18 click on the rebound to try & stay in the saddle at these specific places.

i've been thinking that the rear spring can sink too far when i'm sitting. it's at about 250mm. sag is 100mm. when i lift the seat it only comes up about 10mm.

what are the race guys running, do you think i need a heavier spring, what should i do?

thanks. Taffy

[Kevin_in_New_Hampshire]

Taffy,

Set your rear sag to about 3.5 - 4 inches (??mm)with you sitting on the bike in full gear. Make sure you bounce up and down on the bike to ensure you are getting accurate numbers.

Once the sag is set for you, check the free sag. I think free sag is 10 - 20 mm. If the bike is topping out the rear spring while measuring free sag, your spring is too light for you.

This is a good starting point. After that, I am over my head in suspension.

Kevin

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99 WZ, all YZ mods, de-octopused, OEM YZ tank and IMS seat, jetting by Clark/James, got forked by Pro Action, DSP airbox, PB Header, Stroker SX-1 SA, Thumper Rad Guards, Acerbis Hand Guards. Moab, HERE I COME!!

[sam]

Taffy you only need a heavier spring if your bottoming out a lot.If your descibing kick back then it sounds like the spring is already to heavy given that your rebound damping is up so high.Are you sure you went the right way with the damping? Are you sure who ever valved it didn't cock it up?In the mean time keep the back end down with some rear brake and throttle at the same time, works a treat! ?

[Dougie]

Taffy,

If I am not mistaken, and chances are I very well could be, I think if you are 17/18 clicks out on your rebound you actually sped up your rebound which could be your launching problem.

I remember reading an article (I can't find it right now, if I do I will post a link) that described rebound as follows:

S (soft) = fast

H (hard) = slow

If you are looking to slow down your rebound, you want to go in on your clicks towards H. I think. I am by no means a suspension specialist but I think that is the way it goes.

My stock spring is 5.0 and is set perfectly for my poundage of 163lbs according to Racetech. Your 5.5 is probably pretty close for you weight.

[Taffy]

cheers lads!

kev, i have been checking the sag with my gear on & a bit of help-sorry.

your inches equate with what i've got. my lifted seat sag is 1/4- 1/2".

sam, i'm happy that the rebound is no better or worse than when i sent it. it should have been toughened up (but wasn't/wasn't enough) as i have gone from a 4.8 std to the 5.5kg spring already.

the only time i sit down this thing wants to spit me out! it's just when you go from brake to throttle-mid apex.

i've gone clockwise towards the H so i should be good. i tried the damper rod on the bench when it used to be standard & the thing was just about locked by the 18th click.

hopefully one or two more of you that race etc have swapped springs...

[sam]

Taffy when you bounce the bike with your hand (ie not sat on it) can you tell a difference in the rebound damping when adjusting it.Try going full the other may and see if the speed change is noticeable.There should be a big difference.

When you go into turns does the bike kick up of braking bumps?What sort of riding do you do?Does this new spring seem exceptionaly hard?Did you have the po-go effect with the old spring/before re-valving?

[Taffy]

Sam,

i haven't the bike around as the friend who brought it home from the Isle of Man will have it until Friday night.

i haven't a pogo effect! i brake into corner on soft soil where it's point & squirt. i brake stood & leaning back, sit up front, foot out lean in & as i hit throttle at the bottom of the rut-it just launches me, both up & out!!

i've run with this spring for 4 months but only had the damper done 6 weeks ago. it was on about the same click before it went actually. unfortuately our riding over in the UK varies from rock hard soil to soft sand followed by gloop.

the damper definately gets stiffer as i winde it up-but why the 17/18 of 21 clicks?

has the bike sunk too deep on a soft spring?

is the damping not strong enough for the spring?

cheers Taffy

[Matt_Porritt]

Silly question Taffy.. but you do know that the clickers for the shock are upside down compared to the forks? ?

I way 200 all up with gear and the stock YZ spring is about bang on.

What do you mean that: rear spring can sink too far when i'm sitting. it's at about 250mm. sag is 100mm. when i lift the seat it only comes up about 10mm.???

-How far does the bike sink when you sit on it?? (with 0 being with the rear off the ground)

-How far does the bike sag under its own weight (with 0 being on a stand)

We'll go from there after we get thos figuers sorted!

There is a good article at http://www.ballards.cc/tech.htm for those who are confuzzled!

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**Ride it like you Stole it!**

Matt Porritt

99 YZ400F

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[Taffy]

Matt

i've taken it that the rebound is set under the bike. hard (slower) to the right = clockwise.

stood on it's own to lifted off the floor is 10-15mm. from stood on it's own to me in the riding position with full gear on & a mate at the front = a drop of 90mm. the spring on the shock, on the bench, ready to re-install measures at 250mm & came i think at 270mm free length.

as my second note expands upon is it sinking too deep in the corner as i hit the seat? i suppose it's a bit of a double edged sword having some idea's but there you go. i was hoping to find out what everyone else is running in enduro & motocross etc.

Taffy

[Matt_Porritt]

Taffy.. they sound about spot on! ? (close enuf!)

If anytinhg prob too much tension on the spring.

From the rest of the specs you've given it souns like your rebound is way high!

I'm presuming that 17/18 clicks is from full in?

If so.. thats your problem!

Fully in is right in on the 'H' which is the slowest your rebound will be... 17-18 out is 'S' and is the fastest the rebound will be.

Think of it this way.. 'damping' is the slowing down of somehting... so 'rebound damping' is the slowing down of the rebound.

Toward 'H' it makes it harder to rebound therefore it will be slower.

I think standard is about 12 out from fully in.. try that and if still bouncing you off go a click or 2 towards 'H' (clockwise).

-You don't want to go too far in as then you'll start getting packing in woops etc as the rear won't rebound fast enough to handle the next bump.

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**Ride it like you Stole it!**

Matt Porritt

99 YZ400F

Vist the Rubber Chicken Racing Online Shop

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[Harold_in_So_Cal]

Since you guys are talking suspension, What is the rear high speed compression. Is it that thing that looks like a notched nut on top of the rear shock around the compression clicker?

Harold

[Matt_Porritt]

On a 2000 models, yes it is.. on the 98/99 there is no high speed.

In my opinion its just another variable that we could do without! ?

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**Ride it like you Stole it!**

Matt Porritt

99 YZ400F

Vist the Rubber Chicken Racing Online Shop

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[Bill]

Taffy,

You may want to go to the links sectiona sdn send an email to Jeremy at MX-Tech. His company won the fork shoot out in MXA. He is very helpful.

I to am trying to sort out my suspension and this is what info he gave to me using a "C" class rider of 205 pounds.

95-100mm of sag

Front forks tend to pack so try 8 clicks of compression. Try 8 on the rebound also.

The rear comprression 10 or 11. Rear rebound 7 to 9 clicks out. Keep going higher on rebound til the bike "bucks up/hits you in the bottom" on braking bumps going into turns and then go down 1 or 2 clicks on the rebound.

He did not advise a change of spring rate for me and suggested I try this and if I still wasn't happy to send him the suspension for a re-valve.

I like the fact that he offered help prior to me being a "paying" customer....even asked for my phone number so he could call me a discuss this......I called him instead and he said he asked for my phone number so it wouldn't have cost me to get his advice. This is not true everywhere!

Bill

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86TT225, 98CR80, 99WR, WR timing, throttle stop trimmed, air box lid removed, White Bros head pipe, silencer and air filter. Odometer and headlight removed. Moose hand and mud guards. YZ stock tank and IMS seat. Renthal Jimmy Button "highs" and Renthal Soft half waffle grips. AMA, SETRA.

[Taffy]

Bill et al,

thanks lads. i'm sure we're all agreed that the spring rate for a MX & a green laner are going to alter even if it's by one spring weight.

as i understood it, the valving is set up for you Americans (yet again!) to go Dualsport on & not for racing in british sh--ugar!

if you change the spring rate is it true that the valving will now be wrong?

this weekend i'm doing a proper enduro; 4 one-hour laps. the only thing i'm going to touch is the rebound on the rear. that's it.

let you all know Monday.

[Taffy]

the bike was excellent yesterday. i went three harder on the compression & three softer on the rebound. i only have the problem on soft sand/fen peat etc so i was unable to replicate my problem.

some once told me that you need stiffer suspension when racing on sand, can anyone give it credence?

Taffy

[Matt_Porritt]

Yeah Taffy.. generally the softer the terrain then the more comp you can run and visa versa.

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**Ride it like you Stole it!**

Matt Porritt

99 YZ400F

Vist the Rubber Chicken Racing Online Shop

Discounts for ThumperTalk members.