FRONT BRAKE WAVE WASHERS (RESOLVED PROBLEM)

[MIXR]

Anyone else noticed something unusual?

I've been doing some brake work on my 2001 R1150R. My front disks have always been rattly. Jingling and jangling like Christmas bells. The disks are original. They have never been removed from the wheel in 140,000 kms. The bike is non-ABS, so has not got the ABS ring. Being an early model, it does not have servo brakes either.

A closer inspection of some noises after a front pad change has revealed the following:

The left disk has five 'buttons' that make it a floating disk. Each button has one wave washer to take up the slack so that the disk doesn't rattle.

The right disk also has five buttons that make it a floating disk. Each button has a gap behind it AND NO WAVE WASHERS. Same amount of space as the side with wave washers fitted, but the disk is free to move about two millimetres and rattle and bang like crazy when I spin the wheel.

What gives? Is this a common thing? Is it a screw-up from the factory in 2001? Did someone forgot to fit the wave washers on the right hand disk during assemble? Anyone else come across this? I've never noticed it before (obviously).

I've checked the Parts Catalog and it says that there are 10 (count them - 10) wave washers required for two disks. I'll assume that means 5 per side. Funny that.

I can't see how all 5 wave washers on one side could have worn out and fallen off!

Can anyone enlighten me?

[boxermania]

They will normaly flex until they brake off and fall away. I see that you have an early, 2001 R1150R and that makes only two BMWs that I have seen that happen, the other was a 1994 R1100GS of a rider friend that I noticed excessive play on the rotor while on a ride.

Can't help with the event that lead to the failure, alhough a weak/defective spring washer (maybe improper heat treat) seems to be the issue. Replace the washers (xxxx888), take a good look at the roll pins (xxxxx887) and the rotor holes, if they are out of round or elongated a new rotor wiil have to be fitted.

Good luck

[MIXR]

Buttons (roll pins) looked fine, as did the disk mounting holes. Very little rotational movement of the disk when I was checking everything out. I'm ordering new wave washers and a set of bolts anyway, but just couldn't see how all of them could have gone missing in one go. The disk has always rattled. I never gave it much thought having been used to floaters on other bikes that also rattled. Now I've realised that it isn't as 'normal' as I thought it was, especially when it's only one side. Can't figure out what happened, but it may relate to a new set of pads that have given me trouble lately. Anyway, I'll get the bits and break out a fresh bottle of locktite for the bolts. Cheers.

[iowabeakster]

I remember a thread from a long time ago. There was a guy who was absolutely positive that the front brakes did not have any wavy washers. He claimed to have just removed his rotors, so he knew!

My bike has them...the service manual shows them...so, I thought that he might have been a little crazy.

Boxermania's theory would explain that guy's situation too.

[MIXR]

Rotor bolts came undone with ease. Hard to tell if wave washers were ever fitted (checking for marks) but the buttons (bobbins or roll-pins) look reasonable. Small wear where they have been sitting for so long, but not enough to worry about. Rotor holes are ok. My research says that the buttons should be the wear item rather than the rotor anyway.

Looks like a simple job of getting new wave washers and some fresh locktite and putting it back together. I'll do the other side as well. The assumption would be that it would have some wear in the wave washers as well, but I'll know for sure when I see how thick the new ones are by comparison.

Interesting machines these Bee Em Trouble Yous. Strange things start to happen when the miles and years are getting on.

[MIXR]

I think I have resolved my brake issues.

After much stuffing about over the past fortnight, and removing callipers and pads several (hundreds?) of times, and washing and cleaning things with brake-clean, and wearing out my torque wrench, I discovered a few things and also learned some really interesting stuff. As you know, it all started with binding brakes after a major service where the fork seals were also done, but not the pads as I had a new set sitting at home. This is what I learned:

One – Make sure that when you refit hand guards they don’t foul the brake lever.

Two – Make sure the service guys don’t overfill the brake reservoir when the old pads are really worn down.

Three – Brake callipers are not sensitive instruments – You can treat them fairly roughly. I sure did.

Four – When you discover that one floating disk rotor is missing it’s wave washers, don’t be surprised that the BMW shop has never ordered any or that very few people (none?) have ever heard of the problem.

Five – When you get the new wave washers in ($2.20 each) and you pull the rotor and fit the washers and loctite and torque everything, don’t be surprised when the ‘fix’ doesn’t actually fix anything.

Six – When the brakes are still binding after you have new wave washers, properly fitted pads, a working master cylinder, and working callipers, sit down and have a closer look.

Seven – I discovered that both right-hand pads were loose. Good sign.

Eight – I discovered that both left-hand pads were tight against the rotor. Bad sign.

Why is this so? How can this be? (He asked himself with a quizzical look on his face and a nice glass of red wine in his hand)

Only one thing left. The front wheel. This does not need to be removed for any of the work I had been doing. It was removed by the service guys for the fork seal job. Prior to that it (the brakes) had been working fine.

So I undid the pinch screws and undid the axle bolt. Or tried to undo the axle bolt. An eight-inch spanner wouldn’t do it. Trying to ‘stand’ on it wouldn’t do it. So I positioned the spanner nicely and gave it a sharp kick to break the tension. That worked! Boy was it tight.

Some notes here - The axle can be done up very tight and the wheel will still spin IF THERE ARE NO CALLIPERS OR PADS FITTED. What happens (or did on my bike) is that the tight axle was ‘loading’ the brakes in one direction. So we continue with:

Nine – The release of the tension on the axle bolt will allow the front end to spring and relax a minute amount. Barely perceptible, but noticeable.

Ten – The over-torque on the axle seems to load the disks from left to right. This has a few interesting effects. It pushes the left pads on each disk into the rotor (Tight pads). It pushes the right pads away from the rotor (Loose pads). Or more correctly, it puts a slight twist in the front end and clamps the rotors to the left. Whatever works for you by way of visualisation.

Eleven – What this also does is moves the load away from the left-hand rotor wave washers. That’s why they were ok. However, the load on the right-hand rotor pushes into the wave washers, thus loading them in the ‘collapsed’ position as the disk rotates. This is severe enough to fatigue the wave washers, they break, and fall out. This is called Mick’s theory of wave washer disintegration.

Twelve – Loosen everything off again and do it all with a torque wrench. Bounce the front end to settle and align things, then torque the axle, the pinch bolts, and finally the calliper bolts.

Thirteen – It all seems ok. The new pads are tight as expected, but no noises, no rattles, all pistons moving.

Fourteen – Test ride 10 kilometres. Not too far from home. Lots of braking. Back in the shed. All good.

Fifteen - 100 kilometre test ride. Problem appears solved.

Sixteen – Phone service guys who refitted front wheel to see what their view is. They don’t believe that they would have done an over-torque on the axle bolt. It took a lot more than 30 NM (22 ft lb) for me to ‘break’ the tension. They were the last ones to touch the bike. Hmmmmm - That's strange.

Seventeen – Lessons for everyone. This is one torque value (The front axle bolt) you should never guess at. It can have major ramifications for brake life and brake operation, plus put extreme stresses into bearings, calliper mounts, and even disk rotor mounts.

Big ride tomorrow just to make sure it’s all good.

Mick.

[Ol' Jeffers]

Nice report, Mick!
What would tick me off is the fact that the service guys are supposed to
know what they're doing and let's be honest, you pay them enough.
I wonder what they would have said if the maladjustment had caused you to
have an accident? You shouldn't have to check their work!

[MIXR]

I phoned the manager to relay my findings rather than to have a shot at him or his boys. I know the guy, he has done me favours and good deals in the past, and he is a genuine all-round nice guy. His response was not quite denial that it could have been over-done (incorrectly torqued) at the shop, but that if he had fitted the new pads he might have picked up the problem on his test ride before he released the bike back to the customer.

My problem is that if the bike hadn't needed pads, he would have released it anyway as it rode ok for 50 or so kilometres from the shop to home. It would have been loading the crap out of the front end, and I might have done a disk (or two), popped a calliper, or had a catastrophic failure of the disk or calliper mounts. The problem only really became evident when I rode the bike home and fitted the new pads. The extra thickness exacerbated the problem, causing binding, shudder, and overheated rotors. Plus all the noises as the disk floated when the wave washers 'fell out'.

Disappointing as they say. But definitely a learning experience.

[boxermania]

Excellent write up mate, know you are far more knowledgeble, in my estimation, than the chaps at the shop and the bike is doing great.

[MIXR]

Thanks boxermania. In my Air Force days we torqued everything on aircraft. Hell, we even had to torque the lid on the coffee jar! That's how important that sort of stuff is. A lot of us (and I include myself in this) will often go by 'feel' when we do up nuts and bolts. That works ok for lots of things, and the more practice you get the better a torque-judge you can become. But not on things that have to move, rotate or slide. That's what the Air Force taught me and what I had to teach others later in my career. I guess I should have looked at the wheel earlier in this process, but R1150R brakes do not require wheel removal, so ......................

Anyway - Big ride today to make sure.

[MIXR]

Nice long ride confirmed that everything appears to be back to normal.

Not rapt in the 'whizzy' sound the Goodridge brake pads make, but that will diminish with time I guess. Haven't used them before. Pity I spent a week and a half chasing a brake problem that was a front axle issue. Oh well - We should learn something new every day to keep our minds alive.

Cheers guys. Mick.