After a terminal air leak due to a threaded swivel air valve on my Monarch 4.2 I was facing buying a new shock (NOT IDEAL)or trying to fit something else to swap in. I swapped the mounting kit over to a Fox RP23 that was on another frame that has a longer length (about 15mm)and fitted it. It took a wee bit of effort to compress the shock partially and shoogle it to make the eyelet line up but it is in and looks / feels ok. No idea if this is a big no-no and if this to cause problems to the shock or way it rides - any info , advice??
Bike Forum
using a rear shock of different length?
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Posted 5 months ago #
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longer overall length (eye to eye) will raise the BB and steepen the bike.
without anymore details I couldn't say exactly how badly it will effect your bike but a 15mm longer shock would **** up the geometry of most bikes monumentally!if it feels fine to you no need to care what I think though!
Posted 5 months ago # -
i think as a rule of thumb it'll raise the BB and steepen the HA
*edit* - sorry, GW beat me to it
Posted 5 months ago # -
Fair points - thanks. It is a DW linkage on the frame and thought HA migfht be efected a bit. What if I run shock with a touch more sag - will this lessen the impact of the length change? I have just fitted an angle reducing headset to the frame to lessen HA by 1 degree anyway so maybe it still ride ok.
Posted 5 months ago # -
NOT recommended, the RP23 has a bypass port (that little bump at the end of the air can)for when the shock reaches full extension, if you dont allow the show to fully extend then it wont work properly.
Posted 5 months ago # -
I replaced the Triad on my 2008 stumpy with an rp23 after it got stuck down for the second time.
The original shock was 184mm eye to eye with a stroke of 45mm
The closest RP23 was 190mm x 50mm. Specialized said it would void the frame warranty etc, but I rode it for a year with it on, no issues.
IMO as long as the frame isnt fouling the shock or itself anywhere along its travel, I would use it.
Posted 5 months ago # -
Yeah, but 6mm and 15mm are worlds apart. I fitted some offset bushings to my bike that made the shock only 4mm shorter and it dropped the BB by almost 1/4 of an inch. Assuming all the same stuff then adding 15mm would raise it by nearly an inch which would make the bike horrible IMO.
Posted 5 months ago # -
I used to have a 222mm shock fitted to my old patriot 66 (215mm as standard), which worked fine as I could tweek the angles with the shock shuttle.
I also short-shocked a Nicolai helius ST from 222 down to 215mm, and it actually improved what was already an amazing bike.
I would reccommend letting air out and 'cycling' the suspension through its full range of travel to ensure nothing interferes, or bashes into anything. Do this static in the garage, not by bouncing on the thing, as this will result in knocking air valves off etc. (the voice of experience).
Posted 5 months ago # -
cheers folks - mildred I have "cycled" the shock and it is fine with nothing touching etc - the bike appears to be no different in the way it "sits" although I completely appreciate the fact that angles might be changed a wee bit and the BB might be raised slightly - however, when fitted the new shock length is no longer than the original one it replaced (when measured up against it. (is this to do with the DW suspension linkage mounting perhaps?) it so I'm not clearly seeing how it is gonna make a massive difference to angles when rider weight is on it and under shock is under partial compression anyway. What techsmechs says is a good point and one I had not considered.
Posted 5 months ago # -
Is it just longer eye to eye? Or longer stroke too?
Initial concerns as above on angles, as well as checking for clearance between shock, linkage and frame at both ends of travel to ensure nothing clashes under top out or bottom out.
You'll be running the frame in a different part of it's designed stroke, possibly affecting leverage ratios.
Running more sag will just let you blow through the travel easier.
If you are going to run it and the clearances are fine, some offset shock bushes could reduce the jacking up of the back end.
Posted 5 months ago # -
Must type quicker...
Posted 5 months ago # -
Eye to eye is obviously longer but Im not sure about stroke length - how is this actually measured anyway? - it came off a frame with same amount of rear travel 5.5inch so I (perhaps stupidly?) assumed it would be same or close in stroke length. Ive not ridden the bike yet in carpark test mode - and the more feedback I am receiving here the more I am thinking Im possibly gonna have to face up to the ugly truth of a new shock purchase. raised BB, steeper head angle and shock only partially working all sound pretty rubbish for the kind of trails I ride.
Posted 5 months ago # -
Stroke is difference between fully extended and fully closed.
A longer stroke will let you run more actual sag (same %age) as you'll have more travel.I completely appreciate the fact that angles might be changed a wee bit and the BB might be raised slightly
My 50mm stroke shock gives 140mm at the back. Therefore increasing the eye to eye by 15mm would move the rear axle down by just over 40mm.
Rule of thumb is 25mm on the fork slackens the bike by 1 degree so a rear height increase of 42mm is around 1.7 degrees and a BB raise of 20mm.
In terms of bike geometry, that's a big change.
Of course, if it works without clashing, the proof will be in how it rides.
Posted 5 months ago #
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