i-Drive Clonking!

thedktor

Bike is a new Halfords GT XCR5 with Rock Shox Ario 2.1 rear shock.

Sitting down the action is very good, plush and quiet.

Stand up over bigger bumps and the suspension makes a loud clonk over each bump, which can be felt as well.

Now, the problem is (a) when sitting down there is no issue, (b) nothing appears loose, (c) its not something I can demonstrate when I take it back to Halfords tomorrow.

My theory is that the shock is just crap and this is a "working as designed" problem. The Ario shock is only 120 quids-worth so is not going to work that great anyway.

From what I can gather from experimenting with the pressure and damping:

a) there is nothing clever in the shock to stop top-out clonk

b) increasing the rebound damping to reduce the top-out puts extra strain on the shock's internals resulting in more general clonking

So, any suggestions, or similar experiences?

Thanks.....

TD

thedktor

It *might* be the rear mech and I have tried flicking it but nothing is really obvious. It does it in the big ring just as much, which I thought would be a valid test. Maybe I need to test some more.

I can get top-out noise easily when static by backing off the rebound and then the shock merrily clunks away just by compressing and releasing. Riding like this results in continual clatter as it tops-out, but the noise over bigger bumps seems to be a mixture of this and something very similar.

For example, winding up the rebound also addds in extra compression damping, and the bigger clunking noise is worse like this, but the top-out noise appears to go. The two noises are very similar, hence the vague fault diagnosis!

TD

supersonic

Could be a fualty shock, though this unit does have big top out bumper. The compression circuit and rebound circuit are seperate, you are probbaly experienceing the shock 'packing' down as rebound is added. I had a similar probelm with my saracen. It was the mech!

thedktor

Did some more investigation last night, and in the absence of a bumpy garden had to resort to stoppies and banging the back wheel down hard!

And..... I am now 90% sure its the rear mech .....

Its worth noting that the top part of the (Shimano) derailleur (ie the bit that can move to hit the frame) does not really change vertical position much with different gears, so my original theory that it should do it less in the big ring does not hold. But.... different gears on the back results in different potential contact areas of the frame and mech, and hence different noises.

Next test is quite simple - put a bit of sponge between mech and frame and do some more stoppies. The adjusting screw on the mech is not wound in very far so there is scope to increase the tension to reduce the amount the mech flaps about, but I am not sure what else this screw affects?? Cheers for any guidance....

TD

thedktor

Sorted!

Increasing the mech tension with the adjusting screw was the answer.

Very happy

TD

thedktor

Hmmm, ok, so problem not gone entirely having now tested it again on a longer ride.

I have noticed that one of the main causes of noise is indeed the rear mech, but its not actually banging against the frame. It is in fact the chain and upper pulley wheel banging against the cassette.

The adjusting screw is wound right in which certainly helps, but does not stop the noise completely, not sure how I could increase the spring tension without welding something to the hanger stop!

Also considered shortening the chain, but this would appear to make the upper arm of the derailleur move closer to the cassette.... and lengthening the chain would presumably make it bang about more? !

Any ideas, or do I just live with it?

Thanks...


TD

supersonic

Live with it, or try Sram!

thedktor

supersonic wrote:

Live with it, or try Sram!

Aha I knew someone would suggest SRAM, in fact I knew it would be you supersonic !

I much prefer the finger change of Shimano as its suits how my hands naturally rest on the bars, or even better the dual-shift option (I forget the name ) of the upper Shimano range - its the biz.

Anyway, as for the clunkin clonkin bike, guess I will get used to it eh :roll:

TD

thedktor

OK, so here's an update on this other suspension noise.

Increasing the derailleur tension reduced one noise, and I have found a shock setting to reduce the main clonking to virtually zero - pump up the shock to give 20% or less sag, and back off the damping to nothing or just a few clicks out.

Result! The clonk only appears on more extreme downhill bumps, when to be honest there is a lot of other noise from the chain etc anyway. Otherwise its silent! (see Stumpy thread for significance!)

With the shock that little bit harder the bike feels noticeably more lively and taught, and in fact I’m really impressed with it having ridden it for around 10 hours over the last week. Its taken everything I can throw at it, in all weathers, and is surprisingly fast for a 34lb bike.

Cool!

TD