tony-devon
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| posted on 3/8/11 at 01:43 PM |
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sierra pad to disc gap
Hi all this might seem a silly question, but on my custom build I have a wierd problem, the brakes seem to retract off so far that most of my master
cylinder travel is used in getting the pads out to the discs, then it bottoms
I have 5/8" master, that in theory should shift enough fluid to work.
operating the footbrake and you can see both calipers moving
if the pads stayed closer with just a few thou gap as I had expected, then I think it would work fine, and 20mm stroke on 5/8 master will move 4cc of
fluid, and I only need 2.5cc of fluid to move 2 off 40mm pistons 1mm, but I have much bigger gap, so all the fluid is being used in just moving the
pads, not gripping the discs
what stupid mistake am I missing
heavy is good, heavy is reliable, and if it breaks, hit them with it
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matt_gsxr
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| posted on 3/8/11 at 01:56 PM |
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Tony,
These are front brakes or back ones?
You can get residual pressure valves that will stop the pads moving back so far. Something like 2psi. Not sure why you would need one, though as
most people don't have this problem.
If they are back brakes then the handbrake auto adjust should look after you.
Matt
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britishtrident
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| posted on 3/8/11 at 01:58 PM |
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Know exactly what you mean Been there got the T shirt ---
Are you using special brackets to mount the callipers ??? ---- in which case I would suspect they are not presenting the brake pad surface
square on to the disc surface.
A bit of patience and traditional hand fitting & fettling is required ie bending filing and shimming required.
The other possibilities are the calliper is sticking on a guide pin or the spring clip clip that steadies the floating part of the caliper is
missing
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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daviep
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| posted on 3/8/11 at 02:24 PM |
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Got any play in the wheel bearing?
Disc running nice and true?
Clamp off each flexi to see if one side is travelling too far.
Pump the piston out and clamp the flexi before realeasing the pedal, if you can get the calipers to squeeze the disc you may see something
moving/twisting indicating an alignment problem.
Personaly I would say the master is possibly a bit small as full stroke only moves each piston 1.5mm which seems a bit small to me. I've got no
theory to back this up though just one of those great forum opinions 
Davie
“A truly great library contains something in it to offend everyone.”
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tony-devon
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| posted on 3/8/11 at 02:24 PM |
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Hi guys, these are rear brakes, calipers are mounted at the front of the upright with the bleed nipple towards the top, using the standard sierra
parts
I havent connected the handbrake up yet, as I need to make the cable and a whipple bar due to my custom setup
tonight Im going to wind the pistons all the way back in, and start again. will strip and go over the calipers as well, running out of time, money and
patience LOL
Ive never had so much stress and aggro with anything in my life, as I have these rear brakes.
heavy is good, heavy is reliable, and if it breaks, hit them with it
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daviep
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| posted on 3/8/11 at 02:28 PM |
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Got any pics?
“A truly great library contains something in it to offend everyone.”
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mookaloid
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| posted on 3/8/11 at 02:35 PM |
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quote:
Originally posted by tony-devon
Hi guys, these are rear brakes, calipers are mounted at the front of the upright with the bleed nipple towards the top, using the standard sierra
parts
I havent connected the handbrake up yet, as I need to make the cable and a whipple bar due to my custom setup
tonight Im going to wind the pistons all the way back in, and start again. will strip and go over the calipers as well, running out of time, money and
patience LOL
Ive never had so much stress and aggro with anything in my life, as I have these rear brakes.
I think you need to fit the handbrake cable and keep operating the handbrake cable till it adjusts itself up. Then it should be ok on the foot brake.
"That thing you're thinking - it wont be that."
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britishtrident
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| posted on 3/8/11 at 03:18 PM |
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ISTR it is the hydraulics that operate the adjuster but I could be wrong on that, given the added info I would suspect the self-adjuster
mechanism\s are U/S perhaps somebody in the past forced them back without slackening the handbrake cable.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Arthur T wareing
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| posted on 3/8/11 at 03:22 PM |
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Hi I had a problem with a offside rear calliper at sva I didn't have time to find the reason so just changed it for a new one for retest after
when I did a bit of research I discovered if the hand brake is activated before the vehicle has had the brakes bled it can cause problems with the
calliper.
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adithorp
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| posted on 3/8/11 at 03:30 PM |
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quote:
Originally posted by mookaloid
quote:
Originally posted by tony-devon
Hi guys, these are rear brakes, calipers are mounted at the front of the upright with the bleed nipple towards the top, using the standard sierra
parts
I havent connected the handbrake up yet, as I need to make the cable and a whipple bar due to my custom setup
tonight Im going to wind the pistons all the way back in, and start again. will strip and go over the calipers as well, running out of time, money and
patience LOL
Ive never had so much stress and aggro with anything in my life, as I have these rear brakes.
I think you need to fit the handbrake cable and keep operating the handbrake cable till it adjusts itself up. Then it should be ok on the foot brake.
DO NOT operate the handbrake lever untill the pistons have been pumped out with the foot brake! Otherwise the lever moves too far and fubars the
adjusting mechanism.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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mookaloid
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| posted on 5/8/11 at 08:23 AM |
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quote:
Originally posted by adithorp
quote:
Originally posted by mookaloid
quote:
Originally posted by tony-devon
Hi guys, these are rear brakes, calipers are mounted at the front of the upright with the bleed nipple towards the top, using the standard sierra
parts
I havent connected the handbrake up yet, as I need to make the cable and a whipple bar due to my custom setup
tonight Im going to wind the pistons all the way back in, and start again. will strip and go over the calipers as well, running out of time, money and
patience LOL
Ive never had so much stress and aggro with anything in my life, as I have these rear brakes.
I think you need to fit the handbrake cable and keep operating the handbrake cable till it adjusts itself up. Then it should be ok on the foot brake.
DO NOT operate the handbrake lever untill the pistons have been pumped out with the foot brake! Otherwise the lever moves too far and fubars the
adjusting mechanism.
oops! I stand corrected 
"That thing you're thinking - it wont be that."
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tony-devon
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| posted on 5/8/11 at 10:16 AM |
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thanks guys, I linked up the handbrake and one side works a treat, just getting that side working has made a difference to the footbrake
feel/travel/pressure etc
but the other side isnt playing ball, looks like the handbrake mechanism is either damaged or siezed? I was planning on only running handbrake one
side, as its a trike thats all I need, but now its annoying me that I know the other caliper is knackered. will actuate the handbrake, and releases a
tiny bit, but the lever wont spring all the way back up. this results in the brake dragging/not fully releasing
time to get messy again and delve in to work out how to strip and fix the calipers, thanks for the help
heavy is good, heavy is reliable, and if it breaks, hit them with it
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