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PostPosted: Sat Sep 08, 2012 10:25 pm 
Old School Grand Master
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Location: Fircombe.
Nuff said!
A stiffer axle , or even QR should help, or switch to discs with manual pad spacing adjustment- BB7s, Hope C2, or Formulas


Last edited by suburbanreuben on Sat Sep 08, 2012 10:31 pm, edited 1 time in total.

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PostPosted: Sat Sep 08, 2012 10:28 pm 
retrobike rider
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...what axle/QR would you suggest? Currently XT...


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PostPosted: Sat Sep 08, 2012 10:34 pm 
retrobike rider
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Or does anyone have any experience of the Marin quad link sus linkage?


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PostPosted: Sat Sep 08, 2012 10:46 pm 
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wookiee wrote:
...what axle/QR would you suggest? Currently XT...

Xt are just about the tightest clamping QRs around, but they are, apparently, no match for 10/15/20mm, or whatever, bolted axles..
Bolts do help with stopping the wheel moving around in singlespeed track dropouts, but I'm only assuming, from the marketing blurb, they help stiffen up poorly designed/ over stressed suspension arms.
You may find that with a few miles on them the pads develop the designed clearance and no longer rub. A couple of hard rides may well sort it out.


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PostPosted: Sat Sep 08, 2012 10:53 pm 
retrobike rider
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Hmmm maybe...since fitting they have done around 500-600 offroad miles and have been rubbing over the last 100...


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PostPosted: Sat Sep 08, 2012 10:59 pm 
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look at that swing arm - the chain and seat stays form a triangle but with a small angle - that i reckon is flexing, which is why you are ok on the bike stand but not when riding /cornering.

I have a variety of disc brakes and they have different amount of clearance between the pads and disc; on some there is barely a gap.


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PostPosted: Sat Sep 08, 2012 11:00 pm 
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wookiee wrote:
Hmmm maybe...since fitting they have done around 500-600 offroad miles and have been rubbing over the last 100...

Is that 5-600 miles with no tinkering?
Fit as best you can and leave them to it. THey should sort the,mselves out.


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PostPosted: Sun Sep 09, 2012 8:30 am 
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Sticking my 2p in here....
In my experience standard qrs are pushed to the limit with decent discs. Even the 185mm hope c2 on my commuter is able to pull the left side of the hub down a fraction of a mm on a very hard stop. It's enough to get the pads to drag until I either stop and retighten the wheel or hit a large bump to reseat the wheel in the dropout. I need to find a very tight clamping skewer, I may even try the old chrome shimano ones as they used to be good.

The other issue I've found is one that I've also experienced on old cars converted to discs that haven't been setup properly and it's one that stems from the master cylinder end of the hydraulic circuit.
I'm not sure if XT levers have it, but hopes have a pushrod adjustment. If its too tight and the master cylinder piston can't return all the way then the system appears to gradually tighten up. On cars it can result in a wheel completely locking up on its own as the system gets hotter progressively, but on bikes there isn't the heat levels to do that so you just get a bit of drag. I've found that just the tiniest bit of clearance between the piston and pushrod seems to be about right.
Like I say I don't know if this adjustment is available on the XT system, but it's worth mentioning.

My money's on the hubs moving about in the dropouts though.


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PostPosted: Sun Sep 09, 2012 9:11 am 
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bren wrote:
Sticking my 2p in here....
My money's on the hubs moving about in the dropouts though.


I'm not so sure - the spindle should rest against the drop out cut out - obviously vertical drop outs are better, then the axle nut usually has serrations that dig into the drop out, the whole caboodle kep in place by the QR. I need to measure it by the QR spindle but cannot be much more than 3 mm in diameter, that is not strong enough to hold the axle in place, and it doesn't - it provides the clamping force so the shear plan is not in the QR spondle but in the axle it self.

one thing to check is that there is not too much fluid in the reservoir. my latest 2 wheeled acquisition has formula r1 brakes - the front lever had much more travel than the left, so yesterday i opened the rear bleed screw a fraction whilst squeezing the rear lever to let out a droplet of fluid and now the rear lever has more travel.


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PostPosted: Sun Sep 09, 2012 9:14 am 
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.... you said: I've tried the "loosen off caliper, pull brake lever hold and re tighten"

this only works for post mount callioers - these have a slot for adjusting their position about the rotor. IS mount use shims for the method you describe will not work.

early XT shmano were IS, later and current ones are post mount - i don't see it mentioned which type you have...... but then i have not studied all the posts.


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