CRM250AR road shock rebuild

[Jeram]

Iv got my suspension guy rebuilding my shock right now.

Ive asked him to document all the changes including shim stacks and spring swap for you guys...

he reckons although it is pretty basic, we should be able to get a decent firm road set up which will do me fine for a seasons or two of SM racing.

feel the love fellas haha

[SkidMark]

ask him if he can modify it to add rebound adjustment.

[Jeram]

Nah, If I want to go to that effort I will just send Nitron 450 pounds to make me a race spec CRM SM shock.

But it really wouldnt cost much or be hard to get a CRF shock or similar, remove the bottom eye and get a custom machined eye made that perfectly mounts up to the CRM and gets the length spot on. or if there are hydraulic reservoir fitment issues, find a dirt bike that can have a remove reservoir installed.


something like this from a TM250 couldn't be too hard to fit as long as the length was shorted than the CRM shock.
just unscrew the TM eye and insert your own eye which includes the appropriate extension.

http://www.ebay.co.uk/itm/OB-TM250-TM35 ... 122wt_1185

[Jeram]

actually, that one would fowl on the frame near the top eye... it really does need a remote reservoir shock.

hence in my case I skipped that headache and just decided to make my CRM shock function better


then once Im pushing that shock past its limit at the track Ill consider whether to invest in a nitron shock or whether to invest in a new bike... (Im eyeing off 2013 husky WR300, mates with a dealer, told me they are going to be a whole new kind of animal)

[SkidMark]

you need to remember that not everyone has the skills you have to go into those kinds of modification, or the money to pay someone else to. Therefore if there is a relatively cheap way to modify parts already on the bike then that is usually going to be a more viable option for the CRM masses! Hence my question!

[Jeram]

sorry, I kind of went off on a tangent, but what I was getting at is that it would cost fair bit to get something like that done.

I would say itd cost me say 160 pounds minimum to get something like that done, plus 140 for my mate to do the full rebuild with new spring.
if I wanted to do both together that would cost me 300 pnds...

for 400 pounds you can get a top of the line nitron GP spec race shock made...

so why bother spending that much on modding the crappy CRM shock when you can get the bees knees for slightly more

[Jeram]

Here is the info Iv got from my shock rebuilder, DMCC

SHOCK REBUILD, STOCK SHIMS and PLANNED MODS


Hi Jeram,

The stock shim stacks for the shock are:

Compression
40.2 x 7
23.1
30.1
40.2
38.3
36.3
34.3
32.3
30.3
28.3
26.3


Rebound
36.15 x 6
28.1
36.15
34.2
32.3
30.3
28.3
27.3
26.3
25.3 x 4

Just texted you about the forks... if you can let me know exactly what bike they came from ill do my best to match a shock spring to them to keep the bike as balanced as possible.

All im going to change on the shock is increase the low speed compression by adding some 40.2's to the top of the stack... hopefully this will hold it up in the stroke better and keep it from diving under brakes as much. Not going to bother changing anythign else at this stage just cause the whole setup is unknown its probably better to ride it first then see how it reacts.

cheers Dave"



hope this helps anyone wanting to do their CRM shocks so that you can plan the rebuild in advance, Ill keep you updated as it progresses.
I dare say that It will be a long trial and error set up and might take another rebuild or two to get it perfect, but this will at the very least vastly improve on the stock shock!

[lgingell]

thanks very much for posting this - please keep us posted about how it "feels", and how it performs, lap time etc???

[Jeram]

Based on my shock measurements from another thread Iv found the potential donor KTM shock spring...

it is the 260mm Long spring from the 90's lineup of KTMs

As seen here:
http://slavensracing.com/products/ktm/s ... -620625640


its 15mm longer than the CRM spring and the ID is maybe slightly smaller but only by a small amount.
I hope this will fit.

trying to contact another member who may have used a KTM spring to see what spring rates they used...


DOES ANYONE KNOW WHAT THE STOCK CRM SPRING RATE IS?

[lgingell]

i use a 105 n spring on my crm - its designed for a wp rear shock (ktm, husaberg etc) - i weight 15 stone

The stock spring for the crm is 80n - its designed for a rider of around 9 stone

the stock fork springs are 3.6n.

i use fork springs that are 4.6 n - they are from a kayaba fork (as fitted to some yz 125's)

[Jeram]

bloody champion you are!

what sort of riding was that for? trail?

if you are 95kg and have a 105n spring for trail riding?
I could see myself (80kg) using a 100n spring for road riding/racing?

[lgingell]

hi

teknik racing has the crm listed, and a spring rate calculator on their website

i tried to open their website tonight - but it would not open. I suggest trying again in a day or two - maybe the site is down for maintenance?



alternatively you could use the following link

http://www.pontiacracing.net/js_coil_spring_rate.htm

[Jeram]

my shock rebuilder called up teknic but does not like what they are quoting as the stock spring rate, there are saying that its a 60n spring but Dave whos rebuilding the shock more or less beleives your estimate of 80n

so we are waiting for a enduro suspension guru to to get back from holidays next week as he has aparently dont many crm rebuilds over the years and his input will be vital to selecting the best spring.
At this stage we think 95n is a good guess but want to confirm

[Jeram]

After my suspension rebuilder consulted with an oldskool guru with CRM experience for a week or so, they decided that an 8.5kg/mm spring would be perfect (from a WP KTM/BERG shock) for my needs and will match the forks nicely.

all the parts should turn up on monday and I should have the shock back this time next week!

I might actually get to use my trackday voucher that I got for Xmas before it expires! hahaha

[back off road]

this project seems to be dragging on Jeram