Rear shock sizing (RockShox Monarch)

d3matt

I wonder if anyone can give me any help on rear shock sizing tonight (while my bike is apart)?

My Boardman Team 2010 has a RockShox Monarch 3.1 rear shock. It is leaking air and Halfords are going to send it away for a rebuild. But as I'll be loosing my bike for two weeks, just as the nice weather starts, I thought I'd buy a spare shock of eBay so I can keep riding. A spare shock would also be handy so I can learn how to take them apart and service them too, as I can see I'll be having to do this after the warranty expires (due to the reputation of Monarch shocks leaking).

Any, I've purchased a Monarch 3.3. It listed as 200mm between the eyelets and 60mm stroke. Mine looked 200mm, but now I've taken mine off, I can see that the mine is 190mm.
I've spent ages looking for Monarch sizing on Google and found these sizes below on a Park page. They are shown as the options for a Monarch 4.2HV:
There seems to be no way of ID'ing what you have!

140 x 25 (5.5" x 1")
152 x 32 (6" x 1.25")
165 x 38 (6.5" x 1.5")
190 x 51 (7.5" x 2") - My original Monarch 3.1
200 x 51 (7.875" x 2")
200 x 57 (7.875" x 2.25") - My replacement Monarch 3.3
216 x 63 (8.5" x 2.5")
222 x 70 (8.75" x2.75")

Is this going to matter putting this 200mm shock on my bike? If I slacken off the gear cable, there is enough suspension travel to allow it to fit.
Also will the extra 6mm travel matter?

supersonic

It will make a difference. Firstly the 10mm eye to eye difference will steepen the angles of the bike, probably about a degree or so. The 6mm extra stroke will give you 20mm of extra travel (ish). This can cause problems with clearance at full compression, but the longer eye to eye will stop this.

You will probably void any warranty too.

nicklouse

and as the body is longer running less pressure to return the geo to something like it should be will give you less travel. as the shock rtill bottom out sooner.

d3matt

Thanks for the quick reply.
Tried to measure the effect and it looks like the rear tyre drops by 20-25mm with the longer shock.
What clearance issues do you meant at full compression? With no shock fitted, there is massive travel on the suspension. With the wheel up as high as it goes (until the rear frame hits the seat post), the shock mountings are 130mm apart. Measuring the between the shock mounting points on the frame, the total distance is from 130-215mm.
Would this new shock I've brought, compress to 143mm?

Are you saying it's a definite "no" or a "will be ok for two weeks or more".
Or should I just put it back up for sale and not use it?

supersonic

The compression issues can happen with some bikes if the shock stroke is too long. 190-51 = 139mm. 200-57mm = 143mm, so at full compression there will be no issues as the longer overall length has offset it.

If you run the same sag in mm, the angles of the bike will be steeper and the bottom bracket higher. I also think you will kill your warranty.

So up to you. But I don't see any big issues, but if like nick says you compensate for geo changes with more sag, you will be running less pressure and will bottom the shock easier.

My advice would be to run the same percentage sag if you go ahead.

d3matt

Thanks for your advice. I'll put my original back on for tomorrow mornings ride ride (god I should be in bed now :shock:) then and take it off again to return it to Halfords during the week. I'll then decide if I use this new shock or sell it on.

What annoys me is that there is no way of telling (on either of these shocks) what version they are. I only know this has 57mm travel as the guy selling it stated it. But it could just as easy be a 51mm version. Without compressing it with a tape measure, which isn't easy, you'd never know.