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Post by irishkev on Jan 17, 2014 13:38:08 GMT
Sorry Posted in 600 and moved here. Hi When out on the bike going to work I noticed that when I brake I could feel a shuddering sensation. I thought at first that a brake disc was warped and this was the feeling I was getting through the handlebars. I removed a calipers from it position around the disc and secured it to the so that it did not move but it was still attached to the brake hose. I then went for a spin and applied the brake but didn't get any shuddering sensation at the handlebars so I then put the calipers back on the bike and removed the other calipers. I went out again and applied the brake and again I didn't get the shuddering. I next put the calipers back and took bike out again and while applying the brakes I got the shuddering back again. I thought maybe the bearing in the wheel might be the problem so I checked for movement but it was OK.
I am looking to see what checks I can make to find the cause before I jump in and spend money getting a mechanic to look at it. If anyone has any idea as to what I might try next or can advice as to what the problem might be I would be very grateful. I don't have deep pockets and the bike is the only transport for getting to work.
IrishKev
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Post by teejayexc on Jan 17, 2014 15:28:29 GMT
Give the calipers a bloody good overhaul first. Sticking pistons can give the symptoms you describe.
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Post by Deleted on Jan 17, 2014 17:40:37 GMT
Give the calipers a bloody good overhaul first. Sticking pistons can give the symptoms you describe. +1, also check the caliper slider pins, they can seize and give the impression of warped discs
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Post by irishkev on Jan 17, 2014 21:20:14 GMT
Calipers were stripped and the pistons checked and they move freely with no binding.
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Post by bobh on Jan 18, 2014 23:15:04 GMT
Have you tried checking to see if there's any significant run-out on the discs? It's easy enough to get a feel for it by using a pencil held against a fixed point (e.g. the caliper body) and spinning the wheel.
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Post by irishkev on Jan 19, 2014 14:51:44 GMT
Hi Bobh I am sorry but what do you mean by significant run-out on the disc?
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Post by HRHpenfold on Jan 19, 2014 15:24:38 GMT
Hi Bobh I am sorry but what do you mean by significant run-out on the disc? He means warped discs, run out is the amount of warp, more runout and they are more warped!
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Post by bobh on Jan 19, 2014 18:10:04 GMT
There's a figure in Haynes - I don't have mine any more, but I think it's about 0.25mm (10 thou in old money) total run-out. Which actually seems quite a lot - I think having fixed, rather than floating, discs on the D9 makes it more susceptible to any warpage.
To get an accurate reading it needs to be checked with a dial gauge, but as I say you can get a good idea using a pointy thing attached to the forks, with the point touching the wear face of the disc from the side, towards its outer rim (beyond the outermost holes). Turn the wheel and move the point in or out until it just touches on the highest spot on the disc, then turn the wheel again until you find the lowest spot where the gap is at its maximum, and make a visual estimate of it, viewing from above or the front. If you're very careful, and the point is held very rigidly, you can use a feeler gauge to measure the gap. But just a visual check will tell you if it's negligible or not. Also by rotating the wheel slowly it is easy to spot if there's a significant "ding" around one point where maybe the disc's had a clout from something - I think that's more likely to give rise to a judder than a gradual wave. If there's a reflection from the disc surface that can help to estimate the size of the gap, by effectively magnifying it by a factor of two.
Hopefully the above is fairly clear, though I realise that it's something where a picture would be worth any number of words. If you've ever trued up a push bike wheel, or maybe set up a workpiece in a 4-jaw chuck using a scribing block, as we had to do when we did our apprenticeships many years ago, it's basically the same technique.
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Post by teejayexc on Jan 19, 2014 19:47:38 GMT
Gonna have a go at fashioning something up to check run out on my bikes.
Thought about a simple rig of a small plate with holes on you bolt to the caliper mounts, obviously moving the caliper out of the way first, another hole through the centre of the plate with a nut welded on* and a bolt screwed through to use as a run out gauge.
*
If the plate was thick enough you could even tap the centre hole.
Waddyareckon?
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Post by neilmud Lord Protector on Jan 19, 2014 20:04:18 GMT
Gonna have a go at fashioning something up to check run out on my bikes. Waddyareckon? I thought that was a thermometer & seaweed Neil
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Post by Deleted on Jan 20, 2014 12:19:38 GMT
Gonna have a go at fashioning something up to check run out on my bikes. Thought about a simple rig of a small plate with holes on you bolt to the caliper mounts, obviously moving the caliper out of the way first, another hole through the centre of the plate with a nut welded on* and a bolt screwed through to use as a run out gauge. * If the plate was thick enough you could even tap the centre hole. Waddyareckon? Good idea, but why not just put a long enough bolt through the caliper mount ? (not sure it would contact the disk because I haven't checked, if not you only need a bracket on the end to touch the disk) You could use feeler gauges to check the run out.
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Post by CD on Jan 20, 2014 14:02:44 GMT
IIRC its a fine thread but a smaller and even longer bolt with two nuts would do the same job. If there is a run-out, before you buy new discs take the old ones off and check for disc mounting face corrosion on the wheel. You could also consider turning the disc 180 degrees or shimming some mounts.
My bike had a run out on one disc but the new discs with Blue Spots were fine for 30K miles. Maybe the better calipers stress the disc more evenly. Who knows.
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Post by bobh on Jan 20, 2014 17:59:00 GMT
IIRC its a fine thread but a smaller and even longer bolt with two nuts would do the same job. If there is a run-out, before you buy new discs take the old ones off and check for disc mounting face corrosion on the wheel. You could also consider turning the disc 180 degrees or shimming some mounts. My bike had a run out on one disc but the new discs with Blue Spots were fine for 30K miles. Maybe the better calipers stress the disc more evenly. Who knows. I also had to shim one of the mounting bosses to get one of my discs true(er). A piece of Coke can (other brands are available) thin wall was perfect. I suspect plastic shim wouldn't stand the heat. I like Trev's idea. Though if you're using a screw with a known thread pitch you wouldn't need feelers - just count the angle you have to turn it in or out to make contact. E.g. for a 1 mm pitch screw a quarter-turn = 0.25 mm.
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Post by CD on Jan 23, 2014 22:31:58 GMT
Sums? Nooooo!! But turn the bolt and see how much the stop varies will give a good idea of where the low spot is. If its an even wave the problem may be the disc mounts. If its a sudden change the disc may have been bent e.g. forgetting to remove a disc lock.
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