Any guides as to what this is caused by - and how to fix it?

Message

Aladinsaneuk · #1 Post by **Aladinsaneuk** » Wed Apr 18, 2007 1:32 pm

took the bike in for its MOT and it passed but with an advisory notice

Front Roller Brake test indicates slight fluctuation of brake effort

obviously something to do with frong brakes but what?

bigun · #2 Post by **bigun** » Wed Apr 18, 2007 1:51 pm

Warped discs or pulsating discs? I'd bet its the latter, if so, clean the 'buttons' between the disc and the disc carrier so they can move. They're semi floating discs and these buttons seize up with brake dust etc and give the illusion of warped discs. Its a common fault.

HTH

Bigun

Tervueren · #3 Post by **Tervueren** » Wed Apr 18, 2007 1:51 pm

I would think that you are getting more effort from one caliper, maybe a weak hose

DavShill · #4 Post by **DavShill** » Wed Apr 18, 2007 1:52 pm

Usually means imperfection in braking efficiency, poss cuased by uneven wear on discs or warped discs. Lots of old threads about freeing the disc rotor bolts. Unless its a real worry from a riding/safety perspective i wouldn't worry too much - have you noticed and brake vibe ?

Any other ideas?

Samray · #5 Post by **Samray** » Wed Apr 18, 2007 2:13 pm

I warned my tester of a similar effect on rear brakes, it passed but with an advisory of a worn caliper pivot.

fastasfcuk · #6 Post by **fastasfcuk** » Wed Apr 18, 2007 2:15 pm

just roll your bike down the road and lightly pull you brake leaver so that the pads are just touching if there's a problem with your disk's you'll feel the bike rocking, then do as bigun says.

danowat · #7 Post by **danowat** » Wed Apr 18, 2007 6:15 pm

Warped disc rotors, mine are like it, after the snetterton trackday, and I half expect them to be the same in the MOT.

xrphil · #8 Post by **xrphil** » Wed Apr 18, 2007 6:32 pm

as bigun said
had same notice on my MOT, I had cleaned them up and improved them as they were terrible when i first got the bike. The guy said looking at the milage since the last mot they would need a bit of working in, and they have got beetr now.
it took a lot of cleaning to sort them though.

Aladinsaneuk · #9 Post by **Aladinsaneuk** » Thu Apr 26, 2007 9:44 pm

if so, clean the 'buttons' between the disc and the disc carrier so they can move. They're semi floating discs and these buttons seize up with brake dust etc and give the illusion of warped discs. Its a common fault.

ok - i admit to being easily baffled... i went to have a go at this earlier today, and gave up - I searched on a couple of forums and could not find an idiots guide, preferably with photos, to see exactly what I should be doing....

I assumed this was referring to the black "buttons" under the contact part of the disk.... but mine seem soild.....

Tweaker · #10 Post by **Tweaker** » Fri Apr 27, 2007 9:21 am

I assumed this was referring to the black "buttons" under the contact part of the disk.... but mine seem solid.....

As has been said, there's your problem then. The buttons have a spring washer behind them so that the discs are semi-floating. The best way, IMO, is to take the discs off the wheel as you can't really clean them thouroughly in situ. Then, a nut and bolt through the button so you can turn it and plenty of brake cleaner should see it free up. Repeat for all the other buttons - and yes, it takes quite a while to do! Some have recommended using a screwdriver to flatten the spring washer to allow a bit more movement but I haven't tried this.

Tweaker

Aladinsaneuk · #11 Post by **Aladinsaneuk** » Fri Apr 27, 2007 10:03 am

aha :)

now to find a simple way of supporting the front end while i whip the wheel off - i suspect a front stand may have to be bought....