a wee wobble

[hugeduck]

just fitted cbr front brakes and braded lines. i used the pads that came with the calipers and they started off absolutely shite, so i went down the road doing 100 touching the brake and boom the brakes started working like a charm. but when i brake from 60+ hard theres a strong vibration coming from the brakes, but when i'm just going slow and use the brakes i dont feel any vibration at all. its feels 100% like warped discs but i'm not shore thats the problem becuase i should feel it at slow speeds as well as high speeds? any advice? any way i can test them to see if the discs are warped or not?

cheeeeers

[scott02464]

If they are ever so slightly warped then it will be exaggerated at high speed (faster rpm of the disc) giving the sensation of a vibration.

You could try jacking the front end up and tie wrap the brake lever in ever so slightly then spin the wheel by hand and feeling for the 'bite' where the disc is warped? You could tighten the tie wrap one notch at a time until you get any result? Iv not done this before but just an idea.

Also take the discs of and lay them flat on a bench

Good luck mate ;-)

[seb421]

Hows the wheel bearings? are the pistons on the callipers clean and back of the pads clean and copper greased up too?

For me on two previous sets of warped original discs i've had they have been they noticeable at slow speed with the pumping at the lever

[hugeduck]

Hows the wheel bearings? are the pistons on the callipers clean and back of the pads clean and copper greased up too?

For me on two previous sets of warped original discs i've had they have been they noticeable at slow speed with the pumping at the lever

thats whats i thought, my car has had warped discs for about a year lol so ive got a good bearing of warped discs

the wheel bearings where fine before the caliper change, so unless its a strange coincedence?? but i'll get the front up and give the wheel a wobble to see if theres any movement tomorow

i gave the calipers a bloody good clean and the pistons move in and out freely. i didnt copper slip the back of the pads but i thought that was just to stop them binding?


not to shore the cable tie will work, the front wheel locks up straight away with the slightest of touch without weight.

[hugeduck]

If they are ever so slightly warped then it will be exaggerated at high speed (faster rpm of the disc) giving the sensation of a vibration.

You could try jacking the front end up and tie wrap the brake lever in ever so slightly then spin the wheel by hand and feeling for the 'bite' where the disc is warped? You could tighten the tie wrap one notch at a time until you get any result? Iv not done this before but just an idea.

Also take the discs of and lay them flat on a bench

Good luck mate ;-)

i thought about putting them on a flat surface, might give that a go

[benny hedges]

lots of things to try / check.

wheel bearings as seb said
headstock bearings
check the disc bobbins are free and not seized with brake dust

check tyre pressures and wheel balance

if you do suspect the discs are warped try this.... remove the calipers, get the wheel off the deck.
screw a length of m10 threaded bar in the caliper mounting holes, with a nut either side.
screw it in til it touches the disc and check for run-out, marking any high spots.

tw@ said high spots with a copper / hide mallet.
rinse and repeat.

personally i think itl be the headstock or bobbins seized.

[hugeduck]

what do you mean bobbins? cheers

[lumpyv]

on my mot I got a sort of verbal advisory from the guy doing it. he said that as he spun the the front wheel on the test machine it could detect the brake pad touching the disk at one point of the revolution.?

you could,nt hear it or see it but the numbers on the screen of the machine confirned it. I said "what do I do?" he told me not to worry, so I,m not.

anyway I guess your friendly local mot tester may be able to check it out for you for a small drink?

[geodude]

Try this too?

[youtube][/youtube]

[benny hedges]

Try this too?

[youtube][/youtube]

good tip that - you'll find its when brake dust (very fine, almost like smoke) gets wet, it gets right in there and after a ride when the discs are hot, it sets solid like cement.
another way to free them off is with an easy-out stud extractor, same as with the nut n bolt, just pop it in and turn it until all the bobbins turn free.

[AMCQ46]

I had exactly he same when I uprated my calipers. Anything above 60 I got judder through the brake still the speed dropped. Tried everything from bobbins to sanding the disks, new pads and used pads still the same. Measured the run out and they were In Spec but the ony thing that cured it was fitting new discs . I sold my discs to another member on the forum and they worked fine for hm, so it was strange?

New Armstrong discs did further help the braking and it's is smooth and powerfull now

[tony.mon]

Yep. Get them bobbins cleaned, use a can of brake cleaner while rotating.

The seat that the disc sits on machined into the wheel hub surface has to be very clean and true. If you've had the wheel powder coated you have to scrape off the coating on that area. Otherwise, because the coating isn't of uniform thickness it will make straight discs seem out of true.

If very slightly out of true, you can try taking off the discs, carefully noting their position, and rotate them half a turn. Remeasure to make sure you haven't made it worse.

Best tool for the job is a dial test indicator (dial gauge) or dti, they're only a tenner or so on ebay, but you can probably find a local garage that will lend you one or check it for you.

[hugeduck]

cheers for the link, didnt even know what bobbins where before! i'll give that a go at the weekend