'98 M3 rotors - can/should they be re-machined?

feeling vibration in my '98 M3 during braking.

Can / should I have the rotors machined to remove run out? Or just replace?

Reply to
derek_mcquarrie
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BTW only 55000 miles on the car, and less than 20000 miles on the current rotors & pads.

derek snipped-for-privacy@hotmail.com wrote:

Reply to
derek_mcquarrie

google is your friend

Reply to
adder1969

well the thing is if you have cross drilled or slotted rotors, i would say that you need to replace as i have never come across a shop who cuts those and i would also see the the slots and or cross drill holes presenting a problem to the lathe. If you have standard rotors, check the service manual, or perhaps even the manual to see what minimum rotor thickness is. If there is severe warp replacement may be the only option. If you have standard rotors and after cutting, they still fall within guidelines for your safe driving id say go for it because replacement rotors should not be the cheap sort, not on that car. Happy motoring.

Reply to
varan

Reply to
derek_mcquarrie

Reply to
derek_mcquarrie

How did you bend them? Hard stop from speed and then hold on brake?

Reply to
R. Mark Clayton

I wouldn't be convinced that they've warped anyway. Did '98 M3s come from the factory with cross drilled brakes???

Reply to
adder1969

If the rotors are not warped, what else could cause vibration only during braking?

I d> >

Reply to
mcquarrie

Not much.

Maybe you do. Where do you drive? How often do you brake from high speeds? How often do you have to sit in traffic with the brakes held after doing so? How many steep downgrades do you have to brake on? All subjective and also influenced by your personal braking habits. No; it's not inevitable, but if you tend to warp them on other cars, the BMW will be little different.

You can warp rotors in a half day on track. Or on a mountain road. Or maybe even a bad day on the interstate. It's more of an 'incident' thing than a cumulative mileage thing.

-- C.R. Krieger (Been there; warped that)

Reply to
E28 Guy©

OK. So I did it . I confess.

Whatever the cause, the consensus is my rotors are warped because the vibration only happens during braking.

So, on the question of purchasing new rotors and pads for an M3;

Is the OEM rotor cross drilled? someone expressed some doubt about that. my existing rotors are.

BMW dealer prices are stratospheric, but that's what I get for being married to a woman who wants an M3. I want equal-to-OEM performance but a lower cost. What are some of your experiences regarding aftermarket rotors/pads?

I would prefer pads that didn't squeal quite as much as my current ones do. Other than that I'm happy with my current braking performance.

E28 Guy=A9 wrote:

Reply to
mcquarrie

I wouldn't guarantee it. Worn bushes can give the same symptoms - slight run out that would otherwise go unnoticed sort of excites them into a wobble. It's been a characteristic of strut suspension for ever.

Reply to
Dave Plowman (News)

New BMW rotors are not all that expensive. I've found them to be one of the cheapest options. And performance is just fine. BMW dealer labor is pretty high, though.

For brake pads there are a number of good options that produce less dust and squeal than OEM. I like Axxis Ultimates, although they are still a little "dusty." I've run Porterfield R-4S pads on other cars (not BMW) and they are very low dust, although they don't last as long as the Axxis pads. Both have great braking performance, by the way.

By the way, the most common reason for warping rotors that I've seen is unevenly torqued wheels/excessively torqued wheels. Modern aloy wheels are much harder than cast iron rotors. Torque the wheels too tight, add a little heat from a brisk ride with heavy braking, and those rotors will warp every time. Buy a torque wrench and torque your wheels yourself, if you don't want warped rotors.

Original M3 rotors drilled? Call the parts department of your local BMW dealer and they'll be happy to clear that question up for you. I'm pretty sure that OEM BMW M3 rotors are not drilled, but check to be sure.

-bill w. in loveland, oh "B On Trak"

mcquarrie wrote:

Reply to
bwoodson99

if you have dust covers on the brakes, that may lead t owarpage, if not driving and braking as usual heats em enuff that if you hit a puddle, the sudden cooling effect will warp em. check to make sure theyre the front rotors or back ones. front rotors warping bad may give a lil shimmy in the steering or a slight nudge when braking accompanied by pedal pulsing. if not they may be the rear ones. have the sho check using a dial gauge if they have one, i have yet to see a shop that owns em.

Reply to
varan

true overtightening will lead to warpage. MAny tools dealers like snap on or matco or mac have torque sticks that are appropriate for your car. ask if your shop has them, if not try to order the one specific to your car and bring it into the shop each time your wheels come off, they use the torque stick instead of the regular socket (17 mm probably for your beemer) and will use it to put the wheel bolts back on. ..... i wish i had a 98 m3....

Reply to
varan

try bavauto.com theyre pretty good

Reply to
varan

I've heard this forever, even repeated it. But I'm now convinced this is essentially urban legend.

Reply to
Rex B

Thanks for the tip about the torque stick.

yes, it is a nice car, but it does have it's flaws. The grass is always greener....

varan wrote:

Reply to
mcquarrie

Try

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Steve is a well-known qualityaftermarket parts supplier to the BMW community. A good guy who'swilling to offer advice, as well. And, front pads are a 20-minute jobto install yourself. Learn it; do it; get instant gratification.

I've always been a fan of PBR (fka Axxis, fka Repco) Metalmasters. I know a lot of folks like the slightly less aggressive PBR Deluxe for the street. Both dust light grey, about the same color as your alloys. They also dust less then OEM pads.

So what's the most common reason for warped rotors on a car that

*always* has its wheels cross-sequentially torqued to the proper specs? One like mine ...

It's almost invariably *heat*. Even your theory requires it. Although I'm known for going easy on my brakes, I can feel incipient warping sometimes when on track (and Road America can be very nasty on brakes). At that point, there are two choices. Get them even hotter and 'drive through it' or get off the track and into the paddock (where one stops

*without application of the brakes!*) to let them cool. Either way, it takes them a few days to get back to normal street feel.

-- C.R. Krieger (Been there; dodged that)

Reply to
E28 Guy©

No; you get the opportunity for a real bonding experience. Get the parts, tools, and *share an afternoon* with her changing the pads and rotors.

Personally, I don't think anything you do can guarantee these brakes won't squeal. There are a half dozen 'cures', but none is certain. It's an inherent characteristic of high performance disk brakes. You want quiet; get a Buick.

-- C.R. Krieger (Been there; done that)

Reply to
E28 Guy©

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