MR Pro 300 springs.
 

Just picked up a '23. I weight around 205 so I'm figuring 54 N/mm for the forks. What's a good # for the shock? I looked at the owner's manual which claims a 4.4 N/mm but that doesn't seem right.

Who's a good source for the springs?

Thanks.

54 sounds very stiff to me. I have KYB SSS forks from a 2007 YZ450F on my 2000 XC300. I used the RaceTech calculator and they estimated 48 for me when I weighed 245 lbs for Enduro B. I am down to 235lbs and I wanted it a bit softer so I went back to the stock 47 springs.

Are you going to ride SX on that thing? .54 up front is seriously stiff for your weight. I run .38 front and 4.8 rear for my weight at 140lbs, Beers (remember him? lol) runs .40 at 170lbs with his KYB SSS and a 5.0 rear. That said, I can ride his bike without issue.

For your weight I would probably be looking at going .44 up front with a 5.4 in the rear.

First, you probably know this Ud luz, but make sure that you are recognizing the difference between N/mm and Kg/mm when you're dealing with springs, both in this discussion and when ordering.

The N/mm to Kg/mm conversion is 0.10197. So in my case, I had miscommunication with the Dealer - I asked for a 5.4 N/mm shock spring (when I meant 54 N/mm - no decimal) and he got me a 5.4 Kg/mm spring, which is only a slight step above the stock rear spring (which is 52 N/mm or 5.3 Kg/mm).

Some confusion also exists in this thread where you mention 54 N/mm for the forks, and we are assuming that you mean .54 Kg (which I agree is way too stiff). A 5.4 N/mm fork spring would be too stiff also. The GG manual that I have shows recommendations in N/mm, which is the "less common" designation used.

A second question - are you 205 lbs. with or without gear? If that's your "dry" weight (no clothes), add 25 lbs. for gear. The answer to that question obviously changes things :)

I will try to attach a chart and then post again with later with my experience.

Jeff

Attachment 9518

Oops, I meant 44 on the forks, not 54. I'm 205 without gear.

Jeez, might as well put 2x4's in with 54 springs. lol

LOL! Glad that's straightened out. :D

I am using .44 springs in the Kayabas on my 2018. I am approximately 185lbs with no gear. If you are a fast rider you may benefit from .46 springs.

I would buy the .46 springs and then you have the option of running one stock .42 and one .46 to achieve the .44 spring rate, or use both .46 springs. Gives you options.

I am using a .54 spring on the shock, just for reference. Sag is good, bike handles well.

No worries there, and at 205# w/o gear you're probably more like 230# with gear. So you are a "step up" from Jacob and I. That would indicate .47 Kg on the forks and 5.7 Kg on the shock, if you go by the GG manual (which seems consistent from what I've read).

But you will find available springs (in Kg) to be either .46 or .48 for the forks; shock will be 5.6 or 5.8. So (being no expert) I would suggest .46 for the forks and 5.6 for the shock. But those could be one step too light! (Google "kyb spring rate for 230# rider"). You might want to consult a tuner.

For a source - Cannon Racecraft (Oklahoma City). They are high quality and can get you whatever you need. Ask for springs for a YZ250.

Jeff

PS -
The stock GG fork springs are 454mm long (you don't want 470s).
The stock GG shock spring is 260mm long (you can order the YZ spring at 270mm, which is what they have in stock and it fits just fine).

And at the risk of getting "too far into it", I really like this post on how to select the right shock spring.

http://www.gasgasrider.org/forum/sho...hlight=preload

The idea is that you only want 8-9mm of preload on the spring. If I understand it right, when you add a bunch of preload to get the correct sag, you are also creating a stiffer situation in the initial part of the stroke with no benefit overall. If the sag isn't right, get a different spring (vs. cranking up the preload).

-----------------
From the post:

"The main thing is the preload and the beginning of shock/wheel travel, how easy it is for the wheel to respond to small hits, and how fast the wheel is rebounding from those hits. This has the most effect on how the bike sucks up trail trash. If your spring is too light steering may suffer, and jacking the preload to correct it is the whole point of this thread. Keep in mind that the basic shock valving must be sound for your spring/weight/speed/terrain so you don't attempt to over compensate somewhere else. I'm running.44/5.4 combo and I'm 190 lbs. 1mm preload on the fork springs, around 9-9.5mm on the shock...

Another thing. Don't soften up the fork in an attempt to get rid of the harsh mid spike in certain conditions. This will pitch the bike foward and make the shock feel worse. Solve the real problem (rebound) discussed in the other thread, and things will start falling into place nicely."

"But, what we are discussing here is primarily how less preload provides a more comfortable ride. A bit more static sag will always provide a plusher ride in the initial part of the stroke than a spring that has been screwed down to be stiffer."

"The whole thing is a bit of a catch 22. The right spring will give you the right figures. You may be borderline where you can either run with more preload, or go up a rate and run less. In this case I'd go for less preload and a heavier spring."