MOT - warped brake discs

Originally Posted by Wideboy

well i duno, it was just an advisory last year and the MOT bloke said not to bother with it until next MOT

its not major pulsing on the brakes, just a slight one

Your call then...

[flymo]

the tester will not even consider warped discs unless there is some evidence of this in the way the brakes feel. If they apply smoothly with no pulsing you are good to go, no point in replacing them if they are ok.

If you really want to measure runout properly you can use an engineers dial indicator. It gets positioned onto the disc surface and then the wheel is rotated, you will get an accurate measure of the runout. Unless its excessive it will pass just fine.

If you can no longer feel it then you have nothing to worry about. Check them again though after your next bout of enthusiastic braking and see if the problem returns.

[fastdruid]

Bear in mind that even new discs may not be totally flat!

0.3mm IIRC is the limit which is also what one of the brand new GSXR1000K2 discs[1] was, didn't make a difference though as it cured the warped disc feel.

Druid

[1] Bought a pair of new ones as I was fed up with buying warped ones off ebay, worked a treat, no more pulsing!

[Wideboy]

cheers peeps, done 30 miles and they still seem fine.

[Richie]

Originally Posted by Wideboy

a slightly warped disc is hardly going to kill me

This Ship is unsinkable.
Comes to mind. But true what you say

Originally Posted by GavinD

could have been a rusted up floating pivot that the jig managed to free up?

Had this happen on my 6-pot mountain bike calipers that have floating discs!

I'd be thinking the same.

Originally Posted by Wideboy

a slightly warped disc is hardly going to kill me ...

Maybe not, but warped disks will push the pistons further back up into the calipers and may depending on the extent of the problem limit the maximum braking effort that can be applied.

Originally Posted by Wideboy

a slightly warped disc is hardly going to kill me most is going to do is cause my pads to wear un-evenly

i thought they had some sort of way of checking them for trueness

Had my MoT last week and got similar advice. The tester had the bike on a brake tester device (funny that) you know like the two roller type things in the floor that sit in front and behind each wheel. He applied constant pressure on the brake lever/pedal and the force generated showed up on the analogue dial. The dial was allowed to move a certain amount whilst under this constant pressure which indicates the pulsing. If the dial is fluctuating too much it's a fail.



One of them.

Yup, thats the way its done.

Mine had its first MOT last month and the tester (who I know) said to me "Did you know you had warped discs?"

Obviously my answer was no (second hand eGay GSXR discs). He asked if I had any pulsing through the lever when applying the brakes and I said no.

He said..."Don't worry about it then. They aren't that bad"

Having been told that my discs are warped, I am now more aware (aka paranoid) of any subtle difference in feel or brake response, but there still isn't any pulsing at all.

LOL my MOT tester just sits on the bike pushes it forwards and makes sure they work?!?! Will not state who they are tho......

[Wideboy]

Originally Posted by ryanh1418

........

just what i was looking for, very informative thanks



my last MOT'er was the same, just checked they worked and that was fine but he got shut down lmao , new bloke i use has a very high-tec testing station aswell as garage so he nit picks on any little thing