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Changing shock stroke - DIY???

42 posts & 17 voices | Started 1 year ago by BoardinBob | Latest reply from LoCo

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BoardinBob - Member

My bike: 09 FSR XC Comp, very basic X-Fusion shock with a proprietary size 190mm x 45mm.

CRC has a 190mm x 50mm Fox Float RP2 for £100 which is too good to pass up

I foresee two options

1) I fit the shock as is and hope that the extra 5mm stroke doesn't result in any problems

2) I open the shock up and change the stroke myself. I assume it's just a case of fitting some kind of spacer/ shim

Anyone done this already? Either fitting the shock as is, or changed the stroke length themselves? I know I could send it to TF tuned but I won't pay for something that I can do myself.

Posted 1 year ago #
The Great Stonk - Member

the stroke adjustments would take place inside the damper itself, not the air sleeve.

fox rear shock dampers are nitrogen charged, so unless you have the equipment needed to perform a professional strip down and rebuild of the entire shock, your better off just sending it in for the work to be done properly.

running the shock with a longe rstroke will only do bad things to the frame/geometry of the bike. it will raise the bb, steepen the head angle and possibly create a number of other issues with clearances and stresses in the frame itself...

when people mode shock strokes and lengths its usually to lower and slacken the bike and or limit travel, which is always done with a shorter stroke/length.

Posted 1 year ago #
AndyPaice - Member

I dont think 5mm will make that much difference really. As TGS said, it will slightly steepen the head angle.

I am running a 2.75" stroke shock on my Enduro, where it should have a 2.5" stroke shock and it's not a huge difference in handling.

The RP2should be a much better shock so I recon it's worth a go. Don't forget to buy the mounting hardware too.

Posted 1 year ago #
BoardinBob - Member

. it will raise the bb,

Given the amount of pedal strikes I get that wouldn't be a bad thing!

Posted 1 year ago #
cynic-al - Member

Compress it (deflated) and see if it fouls.

Posted 1 year ago #
Jase_MK - Member

Some more discussion on replacing shocks on FSR XCs here:
http://www.singletrackworld.com/forum/topic/quick-shock-length-question

Posted 1 year ago #
PeterPoddy - Member

As TGS said, it will slightly steepen the head angle

Err, no, it won't!
You need to read the OP properly - Both shocks are 190mm in length, so at rest and in use, all angles will stay the same. Fact.

Where the RP2 differs is that is has a longer STROKE - 5mm more. This will enable the suspension to COMPRESS more than the older shock. This may cause problems with the linkages compressing further than they were intended to and striking the frame.
You need to check clearences on anything that moves!!

IF (big 'if'!) it DOES work, you'll end up with a bike that has more travel from the same starting point, so it will in fact end up CLOSER to the floor at the extreme of compression, which given that FSRs are low slung beasts, might not be good at all.

If the shock has the usual 2.5:1-ish compression ratio, you'll end up with 12.5 mm more travel

Then, on top of all this, there's the 'tune' the shock is supplied with - The basic Propedal and compression and/or rebound settings. All Fox shocks have this. It's the basic settings that the manufacturer specs when they buy a shock. It's printed on the side of Fox shocks, go on, have a look at one if you think I'm kidding!

Personally, I wouldn't bother with it. There's too many variables to go wrong. A £100 shock might cost you double that to get working properly, so you might as well go straight to Fox and get one off the shelf that works straight off, IMO of course!

Posted 1 year ago #
Burls72 - Member

You could always run it with slightly less air pressure and therefore get more sag.

Posted 1 year ago #
PeterPoddy - Member

You could always run it with slightly less air pressure and therefore get more sag.

Won't make the blindest bit of difference. Why would it?

Posted 1 year ago #
clubber - Member

FWIW, on my older Enduro, I fitted a 200x50 shock whihc is around 10mm longer than stock but with the same stroke. It sorts out the low BB issue and the head angle is fine.

So... it might be worth considering a 200x50mm shock which will then not cause any clearance issues and may actually improve the overal handling.

But what PP said is also right - you need to get a shock with the right tune for your bike.

Posted 1 year ago #
PeterPoddy - Member

Clubber's idea is bang on. Longer eye to eye will jack the back end up nicely.

Posted 1 year ago #
J0N - Member

AS PP says. There will be no difference with the bike uncompressed. Everything will stay the same until you bottom the shock out, at which time it may hit the frame.
FSR suspension needs the minumum pro pedal setting but spesh are renowned for there specific settings so its a gamble buying anything and expecting it just to work.
In saying all that check the specs on the higher models, it may just work. at least phone TFT or like and get an opinion.

Posted 1 year ago #
tinsy - Member

PP, is right, but you can check if the extra 5mm will do any harm by just removing the shock and lowering the bike until the measurement I to I of the 2 shock mounting points is 190-50= 140mm appart. If nothing fouls then there is no reason not to fit the other shock.

Yes the BB will get lower in full compression, but other than that no geometry changes.

Posted 1 year ago #
BoardinBob - Member

Thanks folks.

I'll whip the shock off tonight and get measuring.

Posted 1 year ago #
J0N - Member

It would definately be better to opt for a 200x50. Then you might want to consider some longer forks to balance the front end and slacken the angle for quality trail bike (stumpy fsr 140).
muah ha ha ha.....

Posted 1 year ago #
BoardinBob - Member

Forks are perfect. Replaced the Toras with Reba Teams and couldn't ask for anything more but the back end is crying out for an updgrade and at that price it's hard to say no!

Posted 1 year ago #
PeterPoddy - Member

PP, is right, but you can check if the extra 5mm will do any harm by just removing the shock and lowering the bike until the measurement I to I of the 2 shock mounting points is 190-50= 140mm appart. If nothing fouls then there is no reason not to fit the other shock.

It's a good tip. Good way to check it!

Posted 1 year ago #
BoardinBob - Member

Don't think this looks promising.

I removed the top bolt on the shock and moved it out the way and fully compressed the suspension until it hit resistance and won't move any further.

At that point the i2i distance is 145mm so I'm assuming then than the 190mm x 50mm shock would definitely result in the frame hitting itself at some point?

Posted 1 year ago #
BoardinBob - Member

Distance between the arrows is 145mm

The point circled in red is where the rear triangle hits the linkage and stops the suspension compressing any more

Posted 1 year ago #
LoCo - Member

The only option for a 190/45mm fox shock is find a O.E spesh maybe?
Or to get Mojo to custom build one for you as Fox do not allow sales of internal shock parts to anyone other than authorised service centres. That is apart from air can seals. Unless you can get a suspension company to put a 5mm spacer on the internal shaft to reduce the travel. However this would need a re-gas and re-oil.
I can't do this yet as my machinery,seals e.t.c are still in the 'post' and have a baby due next week however will be up and running in a month or so..........

Posted 1 year ago #
BoardinBob - Member

The x-fusion is basically alright but the fox at £100 was a great bargain however I can't justify spending £300+ at Mojo or TF for essentially the same shock with 5mm lopped off it.

Posted 1 year ago #
LoCo - Member

yeah I know, what I was saying was that you could get the CRC £100 shock and get a 5mm spacer put on the shaft to reduce the travel to 45mm and solve fouling issues. A re-gas and re-oil with spacer should only be £30 , maybe..
Unfortunately I'm not in a position to say I can do it at the moment otherwise I would.
Ring around the other suspension firm and see what they say, seals shouldn't need changing as new shock so just oil,gas, labour and 5 mins on the lathe turning a spacer.

Posted 1 year ago #
solamanda - Member

Just measure your bike without the shock fitted. Remove the existing shock and move the rear end so the gap between the pivot bolt points are 190mm MINUS 50mm = 140mm. At this point check if anything strikes on the frame include tyre clearance on the front mech in the granny ring. If nothing hits it'll be fine.

It might ride low when the bike bottoms out but there are other bikes out there that are even lower, you'll be fine.

Posted 1 year ago #
BoardinBob - Member

But the problem is I can't compress the frame to a point where I've got a 140mm i2i gap. The smallest gap I can achieve is 145mm

I'll give tf a call to get a cost for the mod

Posted 1 year ago #
PeterPoddy - Member

Sounds like it won't fit without work then, Bob. Let us know how you get on....

One other idea - Have you looked for a used one on ebay or advertised on here?

Posted 1 year ago #
tinsy - Member

Boarding Bob, OK another couple of check's,

1 have a good look around the bike and find out what is actually hitting and asses how much damage the odd bottom out would be likely to cause.
(remember if you got your sag about right it shouldnt really ever bottom out REALLY hard, just the odd donk)

2 let all the air out of the shock bolt it back into the frame, and compress it just to see if it actually acheives the 45mm stroke its supposed to.. (this is to asses if the shock actually stops the sus moving before the parts that clash in step 1 shows up)

I would'nt know how difficult restricting the shocks stroke is, so cant help on that one, BUT you might just get away with it still, but obviously only you can asses the damage you might cause by bottoming out, and how often your likely to hit hard given the riding you do.

My pal just broke (cracked) the H shaped shock link on an 06 stumpjumper by running too low a pressure and bottoming out hard once too often so even with a standard setup if you dont have it set right, it causes damage.

At a guess the part that stops the movement will be the big rocker arm.

Posted 1 year ago #
BoardinBob - Member

Yeah it's the rocker arm that stops the movement. I reconnected the shock, let all the air out it and compressed the suspension and even with then it's the rocker arm that stopped it moving any further.

Posted 1 year ago #
BoardinBob - Member

Sounds like it won't fit without work then, Bob. Let us know how you get on....

One other idea - Have you looked for a used one on ebay or advertised on here?

I'm on the lookout for the Fox Triad which as far as I can tell was a custom job for Spesh and comes in the required size!

Posted 1 year ago #
tinsy - Member

If the rocker arm bottomed first with the X fusion and not the shock itself, then you wont be doing anything different with the Fox you have found..

Good shock the Triad, my 04 Stumpjumper had the first of them, it cost me near on £150 for a service and a new shock shaft once though!! And if one is for sale its because its borked.]

However what is it you dont like about the X fusion? what isnt it doing that you are trying to gain?

Posted 1 year ago #
GW - Member

BoardinBob - Member
Yeah it's the rocker arm that stops the movement. I reconnected the shock, let all the air out it and compressed the suspension and even with then it's the rocker arm that stopped it moving any further.

No no no..
You need to remove the shock (or at least disconnect one eyelet)

Posted 1 year ago #
james - Member

"asses how much damage the odd bottom out would be likely to cause"
That sounds like a recipe for a cracked frame (though it might not). I somehow doubt specialized would warranty a frame with a shock not meeting the shock 'specification' for the frame (what does the frame manual say? - have you got 190mm/45mm from the manual or measured it by hand?)

"shouldnt really ever bottom out REALLY hard"
But if you start trying to learn to do drops, or let someone a bit heavier try then theres a decent chance it could
Given the reason that they redesigned the '08 SJer (and '09 FSRXC) (or so Bikescene told me) to reduce the load on the top tube to get it lighter, theres a decent chance those parts of the frame aren't upto a hard bottoming out of the frame. I assume a shock will have some sort of hard ramp up at the very end of its stroke to help reduce sudden hard bottoming out forces too?

"I reconnected the shock, let all the air out it and compressed the suspension and even with then it's the rocker arm that stopped it moving any further"
Thats worrying!

Posted 1 year ago #
BoardinBob - Member

You need to remove the shock (or at least disconnect one eyelet)

I've done both. I've tested it with the shock in place and with the top eyelet removed and the shock moved completely out of the way

Posted 1 year ago #
tinsy - Member

James
Not really, its obvioulsy how its been designed in the first place, if the movement is checked by the rocker arm with the std shock then why would it be wrong to allow the rocker arm to check the movement with a replacement shock?

Something has to restrict the movement, be it the end of the shock travel or designed into the likages themself's.

Yes your right an air shock naturally ramps up as it compresses, its in the nature of them, and is also tuneable by reducing the air can volume, Fox actually used to make air cans that were adjustable for volume (cant remember the model)

Of course your right about the warranty.

ps you will of course have noticed the FSR design has swapped back to putting the stresses through the top tube, they change stuff to make it different, I have a tenner says the leverage ratio for either design is within 10% of each other its just a different way of doing the same thing.

Posted 1 year ago #
mildred - Member

I've never had a fox shock that achieves full travel anyway - at that price i would give it a try and then sell it on if it does foul anywhere.

Posted 1 year ago #
khani - Member

have a look at mojo's clearance section they usualy have a few 190x50's and ask to have a reducer fitted, wont be too much then
mate of mine got a vanila for a enduro and they fitted a reducer for free before sending it out

Posted 1 year ago #
james - Member

" its obvioulsy how its been designed in the first place"
I realise that having read further down the thread. I didn't think to retype what I'd written relating to what had been posted before the bottomed out shock catching the frame as new, if that makes nay sense. Basically mostly ignore that entire post

I'm pretty suprised it phycially bottoms out on the frame from new though

Posted 1 year ago #
tinsy - Member

Some bikes move so far the tyre hits the seatube, in the end something stops it somewhere..

Posted 1 year ago #
goodgrief - Member

Some bikes move so far the tyre hits the seatube, in the end something stops it somewhere..

i've done the same on my own rotec but have no pics to prove it. i have rotate the seatclamp round at a funny angle so the lever doesn't point rearwards!

with air shocks you can make them more progressive by packing the can with grease to reduce the volume. if it really does achieve 50mm stroke you can add grease till it doesn't hit the frame.

Posted 1 year ago #
mildred - Member

When I had them, the back wheels on both my Patriot 66's and 224 used to hit the back of the seat and front mech cable stop. I never even noticed it when riding.

Posted 1 year ago #
tinsy - Member

What a great picture..

Posted 1 year ago #