Stumpjumper FSR changes gear on suspension compression

hoberinos

Hi all,

I have a Specialized Stumpjumper FSR 2005. When peddling over undulating ground the rear suspension compresses and the rear derailleur tries to move into a lower gear (and then back again).

I think it's got worse over time, but can't be sure...
Anyone else got a 2005 FSR?
Is this a design flaw, or is there something wrong?

Thanks.

supersonic

Are the cables the correct length? When the sus compresses it may cause the gears to change if the cable outer from the main frame to the linakes is too short.

hoberinos

Thanks supersonic,

That makes sense - I'll try replacing the outer in that spot.

Cheers.

Anonymous

there should be a decent sized length of slack cable under the bottom bracket and as long as the cables are nice and clean, all will be well again.

Mancunianfightingcat

Sounds to me like the loop of cable under the bottom bracket is too short, either take your shock out or let all the air out of it and see what the cable is like when the suspension is compressed. I very nearly made this mistake when I had a Stumpy

nicklouse

Or there is a pinch point or just mucky/rust cables.

hoberinos

Thanks for all your responses.

As suspected, I had made the outer between the downtube and the swingarm too short and this was causing the cable to be pulled under compression.

I've replaced it and it seems to have solved the problem (I'll test it on a proper ride tomorrow).

Thanks again!