Disc Brakes: new legislation/WOF checks

[LB]

If this subject has already been talked about, can someone please point me in the right direction to find the thread?

I have just found out, via a workmate, about this.

He has just moved over here from the UK, and shipped his bike out. When getting a VIN for the bike, they measured the thickness of his discs and he was told they were too thin. He asked me about it, and I thought they were having him on. However, talking with two mechanics at a bike shop, they tell me that in February legislation came in saying that the thickness of discs must be measured, and once they get to the minimum thickness (as specified by the manufacturers, sometimes punched on the discs near where they bolt onto the axle) they must be replaced.

Holy shit, at the rate I clock up kms I'll be in for a new set of discs every 18 months or so. That's big money.

FYI my workmate's bike is a ZXR600 (I think that's the model, I haven't seen it yet) and it's done 26,000 miles.

Anyone else know anything about this?

[Lou Girardin]

As far as I know, it's true. Having said that, I've never seen them measure discs for a WOF. They do for compliance though.
Lou

[Motu]

Well,yeah it's true - but it's another of thoses things that is in the book but not done in real life.Rules are car biased of course.Disc rotors are to be failed if they are below minimum thickness - but how do we test this in a visual inspection? it's not possible in a car inspection,we are not allowed to pull wheels off - but on a bike,yeah,they are right out there,easy to test - but remember...if he thinks they are below minimum and doesn't have the specs on hand - you will have to find and supply the data.

That said,it is something that is picked up in a VIN inspection,as is this case,would be rare in a WoF test.

[Kwaka-Kid]

really?! hasnt this law been out for like millions of years?! my dad said its always been around and they could fail you, and why not? if your discs and past the thin mark they might shatter under hard braking oneday (it doesnt take a while, but its happend alot) anyways it takes forever to wear discs? my bikes dont 30,000km and still no reasonable edge to the discs... maybe its soft pads i run? dunno.

[Andrew]

This scares me each time I go to get a new WOF.

[Kwaka-Kid]

gotta lvoe not being scared when it comes ot WOF's :) relaaaaxed :D

[Motu]

Yep,it's been a rule for a long time.

[Coldkiwi]

the min thickness is usually stencilled on the rotor holding the disc isn't it? hardly takes rocket science to read it then work out the thickness off vernier calipers!

[F5 Dave]

Having just had the discs skimmed on my new (old) touring barge they are close to min thickness. Someone there told me that in Tauranga some of the cops were carrying around mics & measuring bike discs. Hell we skim & wear them down a lot thinner in racing & I have never see a modern disc shatter. Old Iron ones were thick for a reason.

Notice how cops like to pick on people who look like they can afford the fines? Criminals never do & they are harder to catch + they might get a bop on the nose.

But back to my discs which I will probably have to replace eventually, I got them skimmed as they were so warped the bike jumped like a kango when the brakes were applied. It was seriously dangerous on the test ride & I didn’t ride it again until fixed. The bike wore a new WOF which was issued by a testing station. Before they were skimmed they passed the measure test, they obviously didn’t ride the bike that’s for real.

Safety? Nah - LTSA & Police wouldn’t know about it if it toppled off a ladder & bonked them on the head.

[White trash]

Kawasaki owners beware!

We probably fail one Kawasaki a week for rear disc below min thickness.

Sorry.

[Motu]

the min thickness is usually stencilled on the rotor holding the disc isn't it? hardly takes rocket science to read it then work out the thickness off vernier calipers!


I've just had a look at all the bikes in my shop - only the Ninja has min thickness stamped on it...it may be on the others,but could take some finding.Remember,the cost of your WoF is based on the time it takes to do the test - waste the inspectors time and he has the right to charge you for it.

[Kwaka-Kid]

ok F5 dave, maybe ur right but i have heard of 2 people in Formula 3 to have had a disc Shatter, aswell as my old man telling me hes had it happen/heard of it with mates.

[Posh Tourer :P]

If this subject has already been talked about, can someone please point me in the right direction to find the thread?

I have just found out, via a workmate, about this.

He has just moved over here from the UK, and shipped his bike out. When getting a VIN for the bike, they measured the thickness of his discs and he was told they were too thin. He asked me about it, and I thought they were having him on. However, talking with two mechanics at a bike shop, they tell me that in February legislation came in saying that the thickness of discs must be measured, and once they get to the minimum thickness (as specified by the manufacturers, sometimes punched on the discs near where they bolt onto the axle) they must be replaced.

Holy shit, at the rate I clock up kms I'll be in for a new set of discs every 18 months or so. That's big money.

FYI my workmate's bike is a ZXR600 (I think that's the model, I haven't seen it yet) and it's done 26,000 miles.

Anyone else know anything about this?

First hand, straight from the horse's mouth....
Got the VIN for the BM, new registration after a complete rebuild. Had to fill out a brake certification check sheet, detailing what work had been done on the brakes, and specifying actual and min thicknesses for all components (pad and disc as well as drum and shoes), and runout vertical and horizontal (as it were). Also certify condition of all hydraulic hoses and components, and that the brake fluid had been drained and replaced (complete rebuild duh...). This all had to be signed by a mechanic. Ass covering if ever I saw it, but was deemed necesary. The rule may have been around forever, but a directive to actually pay attention to it may be the cause of any new attention. Eg Onehunga Vehicle Testing Station have just recently (last yr) started brake testing bikes, where they havent for the last 20yrs.
In the sphere of cages, yes disc thickness is sometimes checked, normally by the garages who stand to gain from offering to replace it themselves (experience of friends).

[Motu]

If they removed a wheel to check rotor thickness ask them why,they are not allowd to do that - it's a VISUAL inspection only,no invasive tactics allowd.

From my case book - once did a car WoF and as we had a wheel off to do some suspension work I noticed it had a cracked rotor,so failed it on that,I can do that even though I didn't fail it on the original inspection.A rotor for a 73 Galaxy was not available so the owner took it away.A few months later he brings it back - now I know it still has a cracked rotor,but I can't see it,I can't use prior knowledge...so 4 years later I am still issuing WoFs to this vehicle.If I fail it on a tyre and pull the wheel off,then I've got him again...until then,it's out there....somewhere.....?

There are many sound engineering reasons to fail an undersized rotor,but only one is relavent - it's out of manufacturers specifications,end of story.

[Andrew]

the min thickness is usually stencilled on the rotor holding the disc isn't it? hardly takes rocket science to read it then work out the thickness off vernier calipers!

A fine example of a paper engineer and not a practical engineer! Using Vernies wouldn't you be measuring the thickness of the lip? Isn't a micrometer a better instrument to use?

[Firefight]

A fine example of a paper engineer and not a practical engineer! Using Vernies wouldn't you be measuring the thickness of the lip? Isn't a micrometer a better instrument to use?



and of course we all have a pair of those things sitting around :Pokey:

firefight <_<

[Motu]

More specificaly the correct tool for the job,a disc brake micrometer,which has points on the anvils to get right into the grooves.

[Kwaka-Kid]

you guys dont realise how skilled i am with my High school 30cm plastic ruler! hah and i can measure right down to mm!! :p

[Andrew]

you guys dont realise how skilled i am with my High school 30cm plastic ruler! hah and i can measure right down to mm!! :p

Now try cutting that mm into a million parts!

[Kwaka-Kid]

what on earth for? we are talking Racing tolerances here, everythings made with a bit of slop :)

[Andrew]

what on earth for? we are talking Racing tolerances here, everythings made with a bit of slop :)

Just smack some grease on to take up the slop ay?

[Posh Tourer :P]

Just smack some grease on to take up the slop ay?

Tried that on the drum brake rear..... doesnt work..... :laugh: :P
Eventually had to replace rear mainseal, and o-rings on the brake pin (running through the diff).... Drum brake in oil bath = vrey good at hill starts using front brake only

[6Chris6]

Mine failed on the first warrant i got for bike, the front rotors come in new at 4.0mm and min wear is 3.5 so your acceptable wear is 0.25mm each side!
And by the way new ones are $550 each!
And yes they check with micrometer at centre of disc so no you can't use a ruler even if you could pick up 0.5 of a mm

[JoeinWellie]

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 ??

[riffer]

Hey Joe (wow, there's a song in that somewhere...) -

You could try Graham at power motorcycles (sales@powermotorcycles.co.nz)

He sells a heap of stuff on trademe and has a lot of auctions on trademe for replacement rotors. He could help you out.

I've bought a bit of stuff off him recently. Seems a good bloke...

[Kickaha]

Kawasaki owners beware!

We probably fail one Kawasaki a week for rear disc below min thickness.

Sorry.


Whats the deal with Kawasaki rear brakes,I am just having one laser cut after a rear brake problem because the rear disc has between 4-6mm runout in it (ZZR250 rear wheel on a F3 Ducati) and thats the second one I know about with the same problem.

[F5 Dave]

Having one Laser cut? I hope you don’t just mean from some steel plate. The problem here (I am told) is that ordinary plate has different densities & therefore heats up at different rates making warping likely. There was a crowd in Auckland doing this I don’t think they are still around because of this.

Yamaha brakes used to always warp easily. I got some rotor kits from PFM in the UK for my SP. Weren’t totally cheap but better than many other options.

[pete376403]

My mates rat-bike K100 BMW had a pair of rotors turned from Land Rover flywheels (he had a friend who worked in the tool room at Mitsi Motors in Porirua). good British Cast Iron plus the Brembo calipers made that PoS stop a lot better than it deserved to. This was about 6-7 years ago, 'spose you wouldn't be allowed to do that now.

[Kickaha]

Having one Laser cut? I hope you don’t just mean from some steel plate. The problem here (I am told) is that ordinary plate has different densities & therefore heats up at different rates making warping likely. There was a crowd in Auckland doing this I don’t think they are still around because of this.


When I had my BMW R75/7 I had a cast disc made from a Hillman Hunter front disc,they were still crap though.

The Kawasaki rear discs that we have the problem with are the factory discs.

We had discs done in 4mm mild steel and have run them on the front of my 250 superkart,we have also had some done from stainless on a period 82 CBX550 which won the local club champs and in mild steel on a 91 KDX200 and we haven't had any problems with any of them.

We havebeen told we shoul try using bizalloy? and are just looking for some info on it

At Blenheim I was on the other GN125 without the fairing,see you at Kaitoke one day!

[Motu]

You can have aftermarket rotors,as they have no standard markings and none are required,who's to know who made them - but must be original mountings.Cast iron makes the best rotor material,but it doesn't look nice - and looking nice comes before performance in this day and age...who wants those rusty looking things on the front of a $23,000 bike.

[pete376403]

What would be the deal on alternative calipers? I saw a early GSX with late model 4 spot calipers on fabricated brackets, would these be legal? hafta be engineer certified?

[F5 Dave]

Not anymore so I have been told by VINZ. Even changing the master cylinder will require certification. This doesn’t bode well for my old 1100 (sold some while back) with late model callipers & brackets + old style braided lines. Stopped so much better & hence was much safer, but now may be dubious from a legal point of view. Sorry to whoever bought it, -I didn’t change the law.

This whole scene is a knee jerk reaction to the boy racer car phenomenon. By the kids bodging their suspension etc & driving like dorkheads they have got the safetycrats up in arms & it affects Bikes now as well.

Poos I say. :mad:

[Kwaka-Kid]

looks like im going to mount these 4 pot tokico GSXR250 calpers to the gs1000, and its already got vt250 mastercylander and GT750 brakes, the only thing thats given probs b4 is the unmarked braided lines, ah well.

[Motu]

So long as you don't fabricate mounts you should be ok,but not likely eh - bigger calipers to fit bigger rotors are not going to bolt onto original mountings.

It's not so much new rules as implementing ones already in place - what it really comes down to is who's responsable if something goes wrong...never the owner,he's going to blame someone else for the fuck up....we need to take it all the way back to the manufacturer,he's got the biggest pockets after all,and to blame him and not have them weasel their way out...it has to be exactly as they built it....and if somebody modified it....yeah,let's screw him too.Isn't it luverly to be following the American way....I'm never wrong,but someone is,an I'm gunna sue them for everything they got.

The LTSA is just reacting to outside pressure....I just wonder who it is?

[Lou Girardin]

I don't know if it is outside pressure Motu. They have a lot of staff trying to justify their positions by coming up with new 'safety' initiatives.
Lou

[Motu]

Yeah - the ''inventors''

[riffer]

Joe - would these do?

http://www.trademe.co.nz/mcat-0001%2D0026%2D0135%2D/0001-0026-0135-/auction-10189646.htm

[F5 Dave]

Well found! Any idea who makes these & what of?

[LB]

Thanks Celtic, I'll pass this info on to Joe (he's a workmate, and not sure how often he logs onto KB).

He's ordered a set of discs from Victorian Motorcycle Wreckers in Oz, so probably it's too late to cancel the order.

[riffer]

Well found! Any idea who makes these & what of?
Actually, I do. Guy's name is Graham, he has a business called Power Motorcycles and he's been manufacturing brake rotors in NZ for about 2 years.

Claims he makes replacement rotors for ANY bike. If you look at his profile on trademe it even gives you his email address so you can make enquiries...

I've bought brake pads but not rotors from him and had no worries.

[JoeinWellie]

As Lynda said, I ordered a pair from Victoria.

On the bright side, this discovery seems to have sparked a lively debate. On the downside, it cost me (AUS) $500 for the pair.

Another interesting point here, and I am not sure that the bike shop were trying to pull the wool over my eyes here but I was 'advised' that I should change the pads too. He sugested that I would be failed on them too if I had been failed on the disks. As if by default.

This struck me as odd as a. I replaced the pads myself recently and there's only about 5k on them and b. He is the guy checking them for VINZ as the bike was sent to him for the brake inspection. Surely he can see that there is only minimum wear.

[Motu]

Yeah but they have bedded into the old rotors,following their contours,it would take a few weeks to wear to the new rotors and possibly damage them (trust me,some nameless idiot has been there before you) you could resurface the old pads or stop playing around with your life and put a new set in - you wanna die for 30 bucks?

[F5 Dave]

Yeah DIE.

DIE. DIE. DIE. DIE. DIE.

Best you replace that brake lever too. :baby:

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.

[Motu]

My post was sarcasim too,I can't beleive how anal some people can get - just reface the pads with emery on a flat surface until they are smooth - high spots on the pads can cause localised overheating and possibly damaging your new rotors.

[JoeinWellie]

Thanks for that.. I think.

Does this mean I'll have to familiarise myself with that funny pedal under my right foot to slow down while I bed in my new disks...

(I'm sure the instructor showed me how to use it for my test, but I haven't wanted to wear out the rubber on it since then).

[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. :baby:

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..:laugh: :niceone:

[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.