Frosty
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| posted on 13/5/09 at 08:53 AM |
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Sierra Rear brake self adjustment
Hi all, you will see in a previous thread I have been complaining about a poor pedal due to the rear brakes.
http://www.locostbuilders.co.uk/viewthread.php?tid=112681
To summarise, the pedal is rock solid with the handbrake on, and has a bit of travel with the brake off, so nothing to do with trapped air.
I was reading up on some old threads last night and it could be down to the piston self-adjustment.
One person has suggested that the piston must be wound back so it literally just clears the pads, as the self adjustment only has a limited range.
When I fitted the pads I would the pistons right the way back, aligned the nipple of the pad with the piston groove, and then pumped the pedal a
couple of times to allow the pistons to take up the slack.
Then again, I have read that you should wind them right back to their stops, fit the pads, and then pump the pedal by someone else.
Which is right? The first one would make sense I guess given the poor feel I have.
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JAG
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| posted on 13/5/09 at 09:25 AM |
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I used to work for the company that made these rear calipers (TRW/Girling/Lucas) so this is the official route;
1) detach the handbrake cable
2) change the pads and wind back the piston
3) reassemble the caliper
4) depress the foot brake pedal between 6-12 times or until all adjustment is complete.
5) reattach the hand brake cables
6) adjust the handbrake cable tension until the lever on the caliper is between 0.5-1.5mm off the stop
The amount you wind back the piston during changing the pads will only affect stage 4. You may need more presses of the pedal to get the adjustment
correct.
The adjuster works over the entire range of piston travel and is unaffected by the wind back procedure.
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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Frosty
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| posted on 13/5/09 at 09:36 AM |
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Thank you Justin. That dispels the myth about winding back only a small amount then.
I think I'll remove the callipers tonight and check both pistons move freely and go from there.
Regards
Laurence
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britishtrident
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| posted on 13/5/09 at 10:23 AM |
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As above ------- the mistake most peple make is making the handbrake cable too tight --- doing this stops the selfadjuster working (true for
both disc and drum brakes) with disk brakes it can actually knacker the self-adjuster.
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adithorp
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| posted on 13/5/09 at 10:33 AM |
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As said above. But I'd add the warning...Do not pull the handbrake untill after you've pumped the pads out with the pedal! That will mess
up the adjuster. Also without servo assistance you'll have to pump very hard.
adrian
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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Frosty
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| posted on 13/5/09 at 11:11 AM |
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I'm going to remove the hand brake cable from the hooks right now during lunch and give the pedal several really good pumps and see if it helps
at all.
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Frosty
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| posted on 13/5/09 at 12:12 PM |
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I've removed the handbrake cable from the handbrake lever so that the hooks on each calliper machanism are free and can be wiggled. Is this
slack enough, or do they actually have to be off the hooks totally?
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