Spring Rate (Rear)


5 replies to this topic
  • bobpara

Posted April 29, 2013 - 05:32 AM

#1

I have ridden my new WR a couple of times and the rear spring seems OK. I used to race when I was younger but now just do some pretty hard trail riding. I weigh 200 lbs.
Everything I read tells me max rider weight for the stock rear spring is 175 lbs....ie, rear spring should be too soft for me
I look at the last section on the shop manual and they have a section on chassis tuning. They even call out a 'stiff' spring at 5.7 kg/mm (stock is 5.3 kg/mm)
I'm kind of confused. If I convert to lbs/in (a set of units I'm a bit more comfortable with) that's 296 lbs/in vs 318 lbs/in or, at 10" deflection 2,960 vs 3,180 lbs.....not much difference

I'm confused and was wondering what others have done with their rear spring rate.
How much do you weigh, how hard do you ride, and what spring rate do you use?

  • Krannie McKranface

Posted April 29, 2013 - 08:03 AM

#2

It's ALL about setting your sag, and maintaining the desired steering geometry (fork angle). That is the purpose of sag.
It has nothing to do with deflection, or suspension travel. That is all in the damping.

You want to aim for 25mm static and 100mm race sag.
You MUST wear all your riding gear, hydration pack, have a full tank of gas, and measure in the seated semi- ATTACK position. You will need someone to help you.

If you are able to achieve the 100, but your static sag is less than 25mm, then you need a stiffer spring
if you are able to achieve the 100, but your static sag is more than 25mm, then you need a softer spring.

The 25mm is very important, and should be your goal, more than the 100mm

I run 26 / 98, cause I like oversteer.

200lbs WITHOUT riding gear mean you are probably looking at a 5.9 spring.

Use the Racetech and Factory Connection spring rate calculators for targeting in on the spring rates, front and rear.

IF YOU CHANGE YOUR REAR SPRING, YOU NEED TO CHANGE THE FRONT SPRINGS AT THE SAME TIME or the bike will handle terribly......

If you have a pre-2012 WR, you will need to change the damping at the same time, or your bike will pogo.

Edited by Krannie, April 29, 2013 - 08:05 AM.


  • bobpara

Posted April 30, 2013 - 06:21 AM

#3

I understand what you are saying, and your approach is quite interesting.
I have 100mm race sag and maybe 6 mm static sag= need stiffer spring.
So, if I did not want to spend $100s if not more $, the 'optimal' setting for what I have now is to set it for 25mm static sag.
This will probably make for 150+ mm race sag
If I do that, what do I do with the front?
If I don't bring the front down the same amount I'll be riding a chopper !!!!

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  • Krannie McKranface

Posted April 30, 2013 - 01:13 PM

#4

I understand what you are saying, and your approach is quite interesting.
I have 100mm race sag and maybe 6 mm static sag= need stiffer spring.
So, if I did not want to spend $100s if not more $, the 'optimal' setting for what I have now is to set it for 25mm static sag.
This will probably make for 150+ mm race sag
If I do that, what do I do with the front?
If I don't bring the front down the same amount I'll be riding a chopper !!!!


if you dont change springs keep it at 6/100

  • YHGEORGE

Posted May 02, 2013 - 01:18 PM

#5

Just be aware you will have a poor handling and riding bike with 100/6. A very light spring with a huge amt of preload is a very bad combination. And the rear ALWAYS affects the front, the front ALWAYS affects the rear. ALWAYS. I have found that a static sag number from 25 to 35 is acceptable with 100 to 105 rider sag. I have always found discounted used springs from Factory Connection or other riders. Just be sure you can verify the rating of the springs.

  • GuyGraham

Posted May 03, 2013 - 10:29 AM

#6

210 lbs without gear
60N/mm spring
I race (but I'm not very good)
my sag figures are 28mm /103mm

Stock spring is ridiculously soft for a 200lbs rider
Stock spring (2008) is 5.5kg/mm (approx 55N/mm)
Shock has enough rebound damping adjustment to cope with this spring


Front
0.46kg/mm springs
Have had to add extra shims to rebound stack as ran out of rebound adjustment with the stronger springs
Stock springs are supposed to be 0.44kg/mm, but mine measured 0.41kg/mm (and they felt very soft)
5wt Motul factory line fork oil




 
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