EX Suspension

[Duncan]

The suspension on the EX is way too soft for my liking.
I'm 210 lb dry and ride New England single track that includes a copious amount of rocks and roots.

Stock rear spring is a 60/260.
I'm assuming that is 6.0 kg/mm?

Anyone know what stock fork spring rate is?

The MX has similar components (4CS fork, larger reservoir on shock) but different springs.

Philip (228 lb with gear) reported that his MX came with 6.3 rear and he went to 6.6
and front came with 5.2 and went to 5.5

I'm all ears on any successful re springing done out there for the EX.

The 4CS fork was performing very well but last ride it was harsh and topping out with a "clunk", and that's with clickers all the way in.
Hoping a fluid change will get me back under control.

 

[Philip]

I remember that fork top-out clunk. It went away immediately after the revalve and never came back. I even forgot about it, until you brought it up, LOL.

Regardless of what your stock front springs are, you can upgrade to the MX spring specs, and you should be much better when trail riding. Changing springs is easy on the 4CS and the shock.

Or you can upgrade all the way up to the same springs that I upgraded to, and also revalve. Just to warn you, it is at times too stiff for trail riding, but you do gain the pleasure of hopping off of some bumps and small jumps.

 

[Philip]

60/260 means 60 N/mm spring rate and 260mm length. Divide by 9.81 to get kg/mm. This unit conversion is simple, but everyone gets it wrong at times, including myself. The error is only 2%, so most people not not know they made a calculation error.

 

[Duncan]

OK good info
How did you determine that stock MX front is 6.3 kg/mm?
My fork springs are not labeled, would be nice to know their spring rate,
I do know they are 18.625"long (beware that earlier 4CS fork had shorter 18.250 length spring), wire dia 5.24mm, 25 coils.

I'm thinking of searching for .52 fork springs and a 6.3 rear spring, what do you think?

Stock fork oil height was 3.1875" so plan to set at same when fill with fresh oil, and will go to Amsoil 'medium'' fork oil rather than my usual 'light' to firm up slightly.

 

[Philip]

The stock MX spring is actually 63N. I saw it written on the spring only later.

The recommended oil height for MX is 65mm. Your 81mm is still very reasonable.

 

[Philip]

Oh... changing oil on 4CS can be easy if you know what you are doing. It is not an open cartridge fork, but you still can change oil without major disassembly. Just need to burp that fork after you add new oil and before you set the level. Google the procedure. There is a manual burping procedure and the one that involves 6 bars of air pressure.

 

[Duncan]

Oh, I was trying to ask you how you determined that your MX fork spring is .52 kg/mm as shown in your chart below.
I have no numbers stamped on mine but Alex at Slavens Racing (very cordial on phone) said he believes EX fork is 5.0 N/mm.
And your MX rear is labeled 63N/mm thus its a 6.422 kg/mm, right?
I'm on the phone now zoning in on some new springs...

 

[Philip]

Alta told me the MX fork spring rate. I should dig up that email. They made a mistake in units on one of the springs, so the information could be 2% off.