Disc Brakes: new legislation/WOF checks

[LB]

Hey Joe - don't forget to keep me posted on how things go, so I can show you some of the great roads we love riding on. You'll be the only boy in town on a RED ZX6R!!

[Posh Tourer :P]

Yeah DIE.

DIE. DIE. DIE. DIE. DIE.

Best you replace that brake lever too.

Ok sorry enough sarcasm, obviously a visual check will suffice. If the disc has worn with deep grooves (semi recent Hondas like to do this esp.) then the pads will have too -so time to replace. If the guy was competent then this is what he noticed & fair call to him.

But some discs just wear evenly so the pads will be ok, check them for parallel & give them a clean up with some sand paper. Clean the new discs with brake clean as they will have grease on them from handling & bed in as normal.

While you are at it clean the calliper pistons, pad pins & lube slides if so equipped.

If you have badly grooved discs that are still above minimum thickness, you can wear them back into flatness by taking out the pads, flattening them with emery etc, and putting them back in. Repeat every so often ie when you notice the pads match again etc, and you will end up with dead flat discs again after 2-3000km?? (never done it myself, but my dad has) depending on your brakes and riding habits etc etc
Just be careful when you have flattened the pads and not the discs, your braking will be below par for a while. Even better, if you notice your discs starting to groove, flatten your pads nice and early and minimise all this fluffing around...

[Motu]

Why do that? actualy grooves have no effect on your braking efficiency - they add more surface area...is that a good thing? yeah,a bit,from a wear point of view.What determins how powerfull your brakes are is the mechanical or hydraulic leverage and mean effective radius - nothing else,apart from how well they diperse heat.Size of pad means nothing apart from wear rate.These new rotors at the rim (actualy very old,Paul Dunstal made them back in the 60s) are right at the limit of possible mean effective radius.Lateral run out is what you need to worry about,this makes the judder,if the disc becomes too thin it can overheat,there is also the possibility of the piston popping out.

[Posh Tourer :P]

Grooves dont develop by themselves. Often crap in the pads etc etc. This means you wear the discs faster. Grooves by themselves arent bad, its just a symptom of dirty crap in your pads wearing your brakes down. Also, grooved discs tend to get more grooved, and fail a warrant earlier.

[Lou Girardin]

If you have badly grooved discs that are still above minimum thickness, you can wear them back into flatness by taking out the pads, flattening them with emery etc, and putting them back in. Repeat every so often ie when you notice the pads match again etc, and you will end up with dead flat discs again after 2-3000km?? (never done it myself, but my dad has) depending on your brakes and riding habits etc etc
Just be careful when you have flattened the pads and not the discs, your braking will be below par for a while. Even better, if you notice your discs starting to groove, flatten your pads nice and early and minimise all this fluffing around...

Why not get them machined and have even less fluffing around?
Lou

[Drunken Monkey]

I am the poor recipient of the enforcement of this legislation. It was my Ninja that failed the Wof that started this thread. Not wanting to part with $550 (EACH) I've been hunting around for a pair of 4mm disks. Does anyone out there know of any wreckers, importers even an old ZX6R wheel lying around the house ?????

Or am I off to the bank at lunchtime ??

I'm certainly guilty of passing off the bodgiest tape & string fixes to get old cars passing warrants just to get around, but surely you don't want to cheap out on a sport bike that goes from 0 to warp 9 in a matter of seconds? I have always bitten the bullet and got things done properly when its comes to fixing bikes. Don't want something critical to fall to bits slowing the gsx-r down from 270 for that hairpin at Pukekohe...

[F5 Dave]

If you want to take small grooves out of your discs & you know someone with a lathe. Spin them & hold a flat block with some sandpaper against them. I’ve surprised an experienced machinist with this trick, it works quite well. Of course if they are deep grooves then only grinding or replacing will help. Finely grooved discs can tend to get glazed a little quicker & this lowers the coefficient of friction.

At this point I will dispute Motu’s statement

"What determins how powerfull your brakes are is the mechanical or hydraulic leverage and mean effective radius - nothing else,apart from how well they diperse heat.Size of pad means nothing apart from wear rate"

(Sorry dude I’m not trying to get to you honest), but different pads & disc material work better or worse together & so therefore are an essential part of the equation. Try soak your pads in fork oil & see how well they work.

Further more, from a point of friction the size of the pad if it was smaller would bear more weight on the disc rather than spreading it over a larger area (like the idea of a woman with stilettos making holes in the floor compared to a sumo in flat shoes making no damage). The had Police made this argument many years ago trying to debunk Fat tires as being unsafe. However this ignores ‘shear’. The larger surface area does win out in the end.

From a heating point of view the difference in heat between the inner part of the brake pad and the outermost point on the disc will cause a distorting effect that can ‘cone’ or warp the disc. This is why disc pads have been getting thinner & thinner but longer to increase the shear area & thus generate more heat converting the potential energy to kinetic & hopefully as a by-product helping you avoid stoving the back of that car in.

[Posh Tourer :P]

If you want to do it quickly then by all means take them off and machine them. My way doesnt cost anything. Very few private individuals with lathes, only a few businesses have them too.

PS I've tried soaking brake shoes in gearbox oil from diff.... they definitely dont work..... Can sweat the oil out of them with heat though if you do it carefully and dont unglue the brake material from the seat. Dont know about the legality/safety of it, but it was rear brake, and it hasnt failed yet

[Motu]

Yeah,oil on brakes trashes any theory alright,I've worked on brakes that were multidisc working in oil,but coefitiant of friction is a tricky subject.If I remember from my tech days,brass had the same friction as the lining material,and in practise disc pads worn to bare metal will pass a WoF brake test as far as stopping efficiency goes.F1 cars have carbon to carbon brakes and glow red hot in use.Soft pads will have more bite when cold,hard pads will have more when hot,just depends on where we want to stand when applying theory with a broad brush.Yes a smaller pad will apply more pressure on that point,but in real life there are no gains in doing so,we could make a brake to do a stoppy with one finger,but it won't haul you in from 180kph.

[Kwaka-Kid]

i tried drenching my GS1000 fornt discs/pads in fork oil, not on purpose of course, rode for nearly 2 years like that, saved on brake wear! oh i then had a good fire going in the fireplace and held the old pads in tongs and burnt them in it at high temp, got all the oil out i think, 50% of my braking came back! awesome home-guessed trick, hope it hasnt done anything odd to the pads, they havnt shatterd yet etc its been 1,000km

[Lou Girardin]

i tried drenching my GS1000 fornt discs/pads in fork oil, not on purpose of course, rode for nearly 2 years like that, saved on brake wear! oh i then had a good fire going in the fireplace and held the old pads in tongs and burnt them in it at high temp, got all the oil out i think, 50% of my braking came back! awesome home-guessed trick, hope it hasnt done anything odd to the pads, they havnt shatterd yet etc its been 1,000km

You're kidding. Aren't you?
Lou

[Lou Girardin]

i tried drenching my GS1000 fornt discs/pads in fork oil, not on purpose of course, rode for nearly 2 years like that, saved on brake wear! oh i then had a good fire going in the fireplace and held the old pads in tongs and burnt them in it at high temp, got all the oil out i think, 50% of my braking came back! awesome home-guessed trick, hope it hasnt done anything odd to the pads, they havnt shatterd yet etc its been 1,000km

You're kidding. Aren't you? Have you tuned out 50% engine power to match?
Lou

[SPman]

You're kidding. Aren't you?
Lou

This is DIY Logan talking here..

[Kwaka-Kid]

no way lou! why not? it works! i just saved myself the cost of a new set of pads by burning then sanding my old ones. great.

[Motu]

Damn,I just had to deal with this bullshit myself this morning - the hoses were done years ago,before this crap came in,I know who did them,so I'll give them a ring on monday,maybe a signed letter head with the standard to which they were done would be the way to go here.This bike doesn't get used much,for obvious reasons - 100hp in 1987.