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Post by m40man on Mar 31, 2009 19:02:23 GMT
I've taken both the front discs off my Fazer 600, investigating why I get a vibration under braking. (When I bought the bike the previous owner did mention this, & that it seemed like a disc was warped.) But how are you supposed to tell if one or both actually are warped? And could something else give the same symptom? I understand the tolerance is only something like 0.3mm run out, & that isn't easy to see even on a known good flat surface - because the studs holding the outer to the inner ring are proud, so the disc faces don't actually lie on the surface themselves. So before I dig into my dusty wallet I thought I'd ask for any other issues likely to cause the judder / vibration? (I admit, I can't think of anything else myself, but you never know ..... or maybe you do ......  ? |
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Post by Padster on Mar 31, 2009 21:18:54 GMT
Worn steering head bearings can produce a vibrating brake effect. A garage should have a run out gauge they could test the disc with.
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Post by teejayexc on Mar 31, 2009 21:27:49 GMT
May be talking out my a*se here, but eh, nowt new there  , failing the garage having a run out gauge as suggested by Padster, could the wheel be put on a tyre balancing machine and the discs tested for run out?  |
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Post by General Gman on Mar 31, 2009 23:18:47 GMT
Wouldn't have thought you could test for runout on a wheel balancer.... best to beg / borrow a dial gauge and measure the runout properly.
Easy to see warpage on solid discs cos you can just put them on a sheet of glass - harder with semi / fully floating discs because, as Martin said, the bobbins sit proud.
Mebbe bodge a warpage idicator with a graphite pencil mounted to the forkleg....
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Post by teejayexc on Apr 1, 2009 7:27:13 GMT
Wouldn't have thought you could test for runout on a wheel balancer.... best to beg / borrow a dial gauge and measure the runout properly. Easy to see warpage on solid discs cos you can just put them on a sheet of glass - harder with semi / fully floating discs because, as Martin said, the bobbins sit proud. Mebbe bodge a warpage idicator with a graphite pencil mounted to the forkleg.... That's the one Gm, keyword alert! |
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Post by m40man on Apr 1, 2009 10:16:11 GMT
Mebbe bodge a warpage idicator with a graphite pencil mounted to the forkleg.... Thanks GM. So what you're saying is, put them back to check them  ?? (I only whipped 'em off 'cos I couldn't detect any warpage with 'em fitted .) Have you got a dial guage I could borrow ? Paddy:I understand a garage / workshop could prob measure them for me - but I don't do garages (they might want cash off me) ;D. |
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Post by General Gman on Apr 1, 2009 10:28:19 GMT
Mebbe bodge a warpage idicator with a graphite pencil mounted to the forkleg.... Thanks GM. So what you're saying is, put them back to check them ?? (I only whipped 'em off 'cos I couldn't detect any warpage with 'em fitted .) Have you got a dial guage I could borrow ? Paddy:I understand a garage / workshop could prob measure them for me - but I don't do garages (they might want cash off me) ;D. Don't have a dial gauge, but do have a pencil |
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Post by m40man on Apr 1, 2009 13:41:19 GMT
.... but do have a pencil Sufficient lead? |
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Post by General Gman on Apr 1, 2009 14:34:20 GMT
.... but do have a pencil Sufficient lead? Enough for my needs  |
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Post by cam7777 on Apr 1, 2009 16:35:57 GMT
Usually a warp will show up as a dark spot on the disc itself
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Post by m40man on Apr 1, 2009 19:00:41 GMT
Usually a warp will show up as a dark spot on the disc itself Oh. No such mark . But the steering bearings are good, wheel bearings are good so ..... think I'll invest in replacement discs & see if that sorts it. Whilst on the subject of warped discs - are they a cause or a symptom? I mean, are they likely to warp because summat else is 'out' or do they just warp on their own  (Brake pistons are fine & free, but for instance if they'd been binding before, that might have overheated & warped the discs?) If it's likely to be caused by anything else, I'd like to sort that out too, so the new ones don't warp! |
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Post by teejayexc on Apr 1, 2009 19:21:25 GMT
Whilst on the subject of warped discs - are they a cause or a symptom? I mean, are they likely to warp because summat else is 'out' or do they just warp on their own (Brake pistons are fine & free, but for instance if they'd been binding before, that might have overheated & warped the discs?) If it's likely to be caused by anything else, I'd like to sort that out too, so the new ones don't warp! Were they warped before the Lincs run practice |
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Post by cam7777 on Apr 1, 2009 19:50:11 GMT
It has been said that warping can happen if you are heavy on the brakes from high speed and then when stopped, keeping the brake lever held on.
The disc cools down except for the part where the pad is held in contact with the disc
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Post by bobh on Apr 1, 2009 21:17:39 GMT
Martin,
As this bike passed through my hands a while ago I should admit that the lady from whom I acquired it did tell me that there was some vibration when she applied the front brake. But I doubt if she ever applied the brakes hard enough herself to cause them to overheat and warp - as Fiasco can testify, said lady doesn't believe in slowing down.
I think it's likely that an overheated disc would show some blueing, which I don't recall seeing any evidence of. Personally I think it's just as likely that one of the discs could have been damaged during careless maintenance, either by a tyre fitter or an owner dropping the wheel after taking it out. I'd certainly check both discs and initially only replace the one with the worst run-out before forking out for a pair.
Another possibility, and this is a pure guess, is that some of the bushes that connect the inner and outer parts might have seized so the outer part can't float as intended. Some WD40 ought to help with that one.
As to checking it, as suggested a pencil held against the fork will give a good rough guide to whether there is any significant runout. If you've ever built or trued pushbike wheels you'll know the technique. I have managed to get an approximate measurement (on a D9 with solid discs) by clamping a pointer firmly to the fork leg and using feeler gauges at various points aroung the disc.
Good luck - Bob
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Post by General Gman on Apr 1, 2009 21:30:30 GMT
Bob raises a good point there about the disc bobbins - if they are seized then the disc can't float.If they won't free off with wd40 a good trick is to put a bolt through the centre of the bobbin and tighten a nut up on it - can help to free them if they are stubborn.
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Post by CD on Apr 3, 2009 13:53:09 GMT
My 900 has a slightly warped RH front disc. It's not enough the fail the MOT, but I got a spare pair to fit when necessary. I've have been waiting for the warp to get worse or the brake pads to wear out. Its amazing how long those Golfren things do last.
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Post by m40man on Apr 3, 2009 19:14:48 GMT
Well thanks for all the advice chaps. In the end, I've bitten the bullet & bought new. (Yes - Brand NEW!). THe new discs [1] arrived today & I've them & a replacement front tyre whilst the wheel was off. So tomorrow I will take her out & see how things are. I decided on a pair as I couldn't save too much on single prices, what with postage. Very quick service from Sandy Bikes Spares. Paid yesterday morning, delivered to work this morning around 11:00am. (When I paid, they didn't say I *might* get them today - they assured me I would - excellent . ) [1] Kagizume brand, very good match to originals. I didn't go for those wibbly-wobbly sorts! |
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Post by Flymo on Apr 3, 2009 19:32:45 GMT
[1] Kagizume brand, very good match to originals. I didn't go for those wibbly-wobbly sorts! Oh dear... very mixed reviews on that brand, will be very interested of your opinion once you've done a few 000's of miles Flymo |
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Post by m40man on Apr 3, 2009 19:47:26 GMT
Oh dear... very mixed reviews on that brand, will be very interested of your opinion once you've done a few 000's of miles Flymo Any links? I did a wander about on the Net & found 'nowt bad about them. (Or 'nowt good, either ;D.) Edit: Website has some good pics: www.kagizume.com/main_page.htm . |
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Post by Flymo on Apr 3, 2009 20:08:14 GMT
have a search on various bike forums
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Post by m40man on Apr 3, 2009 20:38:39 GMT
have a search on various bike forums Prob with those is that disasters are always on 'a mate's' bike, or are references like 'didn't someone say ....'. I tried to find first-hand references, & the only ones found were OK. (On the Zephyr site & on a Gixxer site I think. ............. I'll be the YDC test-pilot & will report, warts & all. It's a good job I ain't one of those hooning types, just in case they're rubbish . |
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Post by Padster on Apr 3, 2009 23:08:11 GMT
I have the Kagizume ones on my divvy and have not had any problems with them.
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Post by mikestrong on Apr 4, 2009 6:52:21 GMT
& wots wrong with wibbly wobbly? they pretty  |
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Post by m40man on Apr 4, 2009 9:34:51 GMT
& wots wrong with wibbly wobbly? they pretty Reduced surface area for contact with the pads, & some say they're alledged 'self-cleaning' extra edges wear the pads more quickly too. |
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Post by m40man on Apr 4, 2009 9:38:23 GMT
I have the Kagizume ones on my divvy and have not had any problems with them. Dammit Paddy - I thought I was required to go out & road-test them for the benefit of YDC-kind. Now I find you've already done it . Might have to go out & road-test the new tyre instead then . |
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Post by mikestrong on Apr 4, 2009 13:21:31 GMT
Ugh
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Post by m40man on Apr 4, 2009 14:13:21 GMT
Preliminery report: No juddering under braking, so the initial reported problem is cured . I've only done a few miles, probably less than 30, with my youngest on the back (Happy Birthday Alex - 14 years old today ) so a long-term test will have to wait. Braking isn't up to what it should be yet, with both new discs & pads needing bedding in a bit yet. But nothing fell off or cracked ;D. |
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Post by teejayexc on Apr 4, 2009 14:38:26 GMT
(Happy Birthday Alex - 14 years old today ) so a long-term test will have to wait. Braking isn't up to what it should be yet, with both new discs & pads needing bedding in a bit yet. But nothing fell off or cracked ;D. bloomin brave young man that!, (happy birthday btw), getting on the back after you've re-fitted everything!  Oh, and well done on curing the judder |
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, failing the garage having a run out gauge as suggested by Padster, could the wheel be put on a tyre balancing machine and the discs tested for run out? 
?? (I only whipped 'em off 'cos I couldn't detect any warpage with 'em fitted 
(Brake pistons are fine & free, but for instance if they'd been binding before, that might have overheated & warped the discs?) If it's likely to be caused by anything else, I'd like to sort that out too, so the new ones don't warp!
