Can you suggest some (comprehensive) reading on springs for rear shocks?


I'll tells ya!
Staff member
Dear Friends and Colleagues,

As you may be aware I have recently purchased a bicycle that comes assembled with a rear shock absorber. This 'shock' is of the spring variety, a type I have not used for approximately 12, or so years. Given the technological advances made and the quantity of brain cells exchanged for experience during this period I've got next to no fucking chance of working shit out for myself. With this as the backdrop I am need of guidance as to how I might increase the preload of my Fox Van R shock on the bicycle I've acquired.

Given time I'm likely to replace this shock for an up-to-date model more appropriate for a bourgeois chap taken to ale and cigars such as myself. But until that particular chime strikes I must make do. Unfortunately, due to my generous physique, sitting on this cycle results in sag of approximately 50%. I am advised that this outcome is unsatisfactory. Thusly, I am interested in placing a spring with greater fortitude on the shock so the sag is closer to the 30%mark. The confounding factor here is in the numbers printed on the shock - 450X2.37. I understand the relevance of 450 but 2.37 may as well be hieroglyphics the good it does me. I've searched far and yonder for the code to unlock this mystery but to no avail. And this is where I must extend my request to you.

Could you possibly point me toward the manuscript which can unlock this riddle? Should I place the finest possible point on this request it would be to ask whether I can put a spring with the markings 550X2.75 or such on the shock? I note that the preload nut has a good 40mm of thread on which it can be screwed to accommodate a longer spring. Are all springs the same inner diameter and whilst we're traipsing this briar how the hell do I increase preload on this existing spring by screwing the nut tighter? I get the mechanics of it but how the hell to turn this cunt with that bedevilled spring resisting my efforts? I would be ever so grateful if you could enlighten this black path of frustration and ignorance.

Yours sincerely,

Go Fuck Yourself


is a man of many talents
Second numbers are spring travel or compressibility you can safely achieve without the spring binding or bottoming out. It needs to be bigger then the shocks travel.

Best not to mix and match brands due to inner diameter size differences.

Preload adjuster, like all tight things, needs lube and a good grip, mutligrip pliers will help. Don't take spring preload to the point of binding.

Some info here:


I'll tells ya!
Staff member
Christ I dribble shit when I'm drinking....

Anyway, I did read that CRC page and found it poorly written and inadequate, hence the use of 'comprehensive' in the thread title. I did just find this, which was helpful in understanding binding anyway

So really, when I'm replacing a spring in the rear shock the second number isn't a huge deal. What matters is inner diameter, free height and obviously the spring rate for the relevant weight and usage. When I replace my current spring I simply endure matching brand, correct rate and that the free height suits. Is that correct?


Likes Bikes and Dirt
Close... ID, rate and stroke are important.. free height various with brands, rates and materials..
Eg a 2.5in stroke spring on a 3in stroke shock is all types of bad news.

Get a 475 or 500 x 2.25/2.37 Fox spring (there are 2 different measurements in stroke.) if your shock stroke is 2.25 then alot of brands will call that a 2.25 spring. however Fox and a few other brands measure the total stroke till coil bind so its normally a little larger than the recommended stroke you could theoretically fit a 2.5 or 2.75 stroke spring in there but its heavier...

Also avoid Cheap/Chinese springs...


I'll tells ya!
Staff member
Yeah, sorry, I should have been clearer in saying the spring stroke only matters in that it has to be equal to or greater than shock stroke. It doesn't have to match exactly and can be higher/longer without causing problems.

Found a 550 & 600 in the for sale section, giving them a look see.

pink poodle

You can only preload the spring a few rotations without reducing the stroke too long, or so the Bear and other suspension gurus used to say back in the day. In modern time this may be a little different, especially with fox running longer stroke springs. To crank on preload I usually just grab the spring and wind it. As it is in firm contact with the collar they usually work together. Otherwise one hand on the collar and the other on the spring.

I suspect your 2.75 spring will have a bit too much length for your shock. Wind the collar all the way out and measure your available distance and you might get lucky. A 2.5 should fit.


I'll tells ya!
Staff member


Likes Dirt
Ah, all the memories of owning a DH bike coming flooding back. How I didn't remember that myself escapes me.

Can't believe I just paid $1 for a spring. Thanks for the suggestion.
No problems at all I couldn't believe they were $1 either. You could have bought one in every weight to make sure the sag was perfect and still only spent $5 hahaha.