Had my 380mm Movits re-faced to help to kill the shuddering..some thoughts?? - The Unofficial BMW M5 Messageboard (m5board.com)

Apples · 4th August 2002, 16:19

I took the 380mm Movits into my BMW Techs shop for a bit of a touch up last week. I had been getting some bad shuddering the past few months as some of you might have known, and it needed some serious attention.
So we went for the reface to make sure she's 100% true. He takes them to a shop that he's used for years. He puts them back on after the re-face and calls me to tell me that they are miles worse then before....

He decides to go to another shop and get them re done again, he finds out they are much improved and miles better

. The first shops cutter was all screwed up and it needed a tune up of it's own.
I still have the same pads in as before (blue ones l guess Pagid not sure) and i'm wondering if l should change to a new set or if it's ok to just stick with the oldies and re-run them into the new rotor

....seems to be fine now.
I'm thinking of getting some track pads as well....any ideas
After some sprinted back road driving and braking the LM wheels are so dam hot you can hardly touch them, and l've come back 30min later after she's parked and they are still bloody warm. I'm pretty sure that for the track l could go a higher temp compound??? Saying that l've yet to induce any fade into them, but how could you with street driving.
The rotors have almost had the re-face grooved marks rubbed out after doing 10+ firmish 80-40mph slowdowns, and there is very little shudder to be felt at all now. The only thing l really feel is the tires trying to grip the tarmac the best they can. I also asked the Tech about the bearings and he said that after the brakes were re-fitted he did measure some run out....l think it was 5 thou.......that seems a lot, but l hardly feel much at all under 75% braking power.
I wonder how out of round the rotors were before they were re-cut and how they got worse over time

it might have been rotor/bearing combo??
If it gets worse again we know the bearings are on their way out, and we will replace them from there.
I got email a got from the Movit man and he said that l would/could have probs at around 10k as the bearings won't handle that rotor too well. I've only done 4K so far so l'm well short of the 10K mark......no big deal, thats only maybe a new set every 12 months
Question how would l find out what size pads and colors l would need for the 380mm movits for a street/track pad maybe the blues l have could work for all conditions..... what about a straight track setup pad (pagid yellows???).....should l just give Pagid a call and chat to their techs...whata you guys think???
BTW....I don't think my Tech has any high temp brake fluid in the system at the moment.... l should upgrade there to???
Summary
1... should l get new pads for the new re-cut rotors, make a difference....feels fine now??

2...Should/could l use a different compound pad if l get to the track...what one would be good.

3...What high temp oil should l be using.
Thanks in advance guys
APPLES

TCM · 4th August 2002, 18:35

Well, I am no brake expert but I would say since you have already done some braking with the old pads then you mines well leave them on as they have already worn themselves into the newly surfaced rotors. If you are experiencing no braking problems I say leave them. From all that I have read it appears to me that there is no need for track pads if you are not an all out racer. The stock pads and aftermarket pads should be fine to take a couple runs around the track IMHO. If you find that you want to race more, I think race pads become a better option. I suggest either Motul 600 or Superblue brake fluid. Castrol SRF is the best but cannot be mixed with any other type of fluid. If you need to add brake fluid and do not have access to the rare and expensive Castrol SRF then you are screwed. The Superblue and Motul can be mixed with generic fluid in case of an emergency. I think Dave Z. is the man for this arena so maybe he can shed more light on the subject. Glad to see you resolved your braking problems Apples.

CruizinKO · 4th August 2002, 18:45

Hey Apples, I replied to your last thread with the pics of your X5 and M5 with some questions about the big brake kits, but I'm not sure if you saw it.

Anyways let me ask it again

How do you like the Mov'it brakes? Did you consider any other big brake kits like Brembo or AP Racing or anything like that? I am currently trying to decide on a big brake kit to purchase and I have no idea what to get.

Also, after reading this post I'm a bit concerned on how long the rotors will last and where you can purchase new ones from and the cost of the rotors. Can you buy from any Porsche dealership or does it have to be from Mov'it? Thanks!

DZeckhausen · 4th August 2002, 23:02

Quote:

Originally posted by Apples
He takes them to a shop that he's used for years. He puts them back on after the re-face and calls me to tell me that they are miles worse then before.... He decides to go to another shop and get them re done again, he finds out they are much improved and miles better . The first shops cutter was all screwed up and it needed a tune up of it's own.

Depending on how much material was removed, the first shop owes you a new set of front rotors. And those 380mm Porsche rotors aren't cheap! You should find out how thick the rotors are currently. They started life at 32mm thick and I'm not sure what the minimum allowable thickness is. But if one shop cut them and put them way out of whack and a second shop cut them again, then it's my guess you don't have much life left in them. Use a set of calipers and measure the thickness or have your mechanic do it. In the meantime, I'll try to find out the minimum thickness allowed on that rotor and we can calculate the percentage of life those two cuttings took away.

That's very piss poor! The first shop should have measured the runout of their brake lathe BEFORE touching your rotors. It's easy to do and it's common practice at any decent shop. Sounds more like the antics of Pep Boys than a decent performance shop.

Quote:

I also asked the Tech about the bearings and he said that after the brakes were re-fitted he did measure some run out....l think it was 5 thou.......that seems a lot, but l hardly feel much at all under 75% braking power.

When you say "hardly feel much" does that mean you do feel a little bit of vibration? You should be able to get less than 5 thousandths of runout on a non-floating rotor such as the Mov'it. Was that measurement of runout taken on the brake lathe or was it taken on the car?

If the measurement was taken on the car, you should try indexing the rotors 180 degrees and measure again with all 5 wheel bolts torqued down. Mov'it hats have extra holes that engage the hub pins so that you can take the rotor off, turn it 180 degrees and then remount it. Sometimes you will find that the hub runout and the rotor runout can cancel each other out almost entirely if you index the rotor. On non-M5 E39s, you have 5 different positions you can index the rotor to. On the M5, only two positions.

Finally, if the rotor isn't held in place by 5 wheel bolts that are all torqued to at least 50 lb-ft (using washers to avoid bottoming out the bolts or damaging the aluminum hat) then the runout you measure will be totally inaccurate. You can try an experiment by torquing 4 wheel bolts down and just snugging the 5th one hand tight. (Mark that one with a piece of tape.) Then measure runout with a dial indicator. You will find that the high spot corresponds to the untorqued wheel bolt!

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I wonder how out of round the rotors were before they were re-cut and how they got worse over time it might have been rotor/bearing combo??

Probably not "out of round" or warped at all. You may just have had some pad deposition on one side or there may have been some corrosion on the surface between the hub and the rotor hat. The rotors should have been measured OFF THE CAR and the high spots noted and marked. Then the rotors should have been turned as little as possible and measured and marked again. Like this:

Quote:

If it gets worse again we know the bearings are on their way out, and we will replace them from there.
I got email a got from the Movit man and he said that l would/could have probs at around 10k as the bearings won't handle that rotor too well. I've only done 4K so far so l'm well short of the 10K mark......no big deal, thats only maybe a new set every 12 months

Your bearings are probably fine. Steve is VERY conservative when it comes to these kits. I'll bet your bearings last 30,000 miles or longer. Don't replace them until you have had someone who knows what they are doing measure the rotor runout both on and off the car and eliminated the more likely sources of trouble. (And of measurement errors!)

Quote:

Question how would l find out what size pads and colors l would need for the 380mm movits for a street/track pad maybe the blues l have could work for all conditions..... what about a straight track setup pad (pagid yellows???).....should l just give Pagid a call and chat to their techs...whata you guys think???

I'll find out the pad size for you and get back to you. For the street, you should continue to run the Pagid Blue pads. For the track, you should start out with Pagid Orange (compound RS 4-4) and see if that works for you. The good thing about these pads is that you can drive home after the track event and they will work reasonably well when cold. You can reinstall the Pagid Blue pads at your leisure. If your rotor temperatures exceed 600 degrees C, then the RS 4-4 compound pads will still work (you won't lose your brakes) but they will wear away rapidly. You may go through a set of pads in a single day of tracking the car. If that happens, then you should go to the Pagid Black (compound RS 14) which is good to about 650 degrees C. But don't try to drive home from the track with the Pagid Blacks! When cold, the first time you hit the brakes, the pedal will be firm but the stopping power will NOT be there. You'll zip right past that stop sign!

Quote:

BTW....I don't think my Tech has any high temp brake fluid in the system at the moment.... l should upgrade there to???

Yes. Use Motul 600. With fresh Motul 600, the brake fluid will be taken out of the equation and you won't have to worry at all. ATE Super Blue Racing (or ATE TYP 200) are distant 2nd choices but have a dry boiling point more than 50 degrees lower than Motul 600. Still, they are better than most other stuff out there.

Apples · 4th August 2002, 23:59

Good stuff guys...much needed info.

CruizinKO...Set up a post on that topic or do a search under..... brakes, they are very well covered in this board. The kit for the M5 was custom from Nowack in Germany so it was an optional brake upgrade l chose to take, and Movit don't sell that kit in the USA. I'm sure the Movit 355mm set up would be perfect for M3 M5 X5. They say the Stop Tech brakes are good to. You will get plenty of opinions from piles of users. My Movits are from the Porsche motorsport division so their not the same as most other brake upgrades and hard for me to do a comparo...

DZ...I know that the venting holes in the rotor had a taper to them in the start, and now after the re-cut there is very little of that left, almost a normal looking hole. I don't feel like an unreal amout has been lost but having them recut has hurt their life time.
Towards in inside of the rotor (near the hat edge) you can see the old higher section that used to be just that fraction higher maybe enough to run/catch your finger nail on.
I won't be home for 3 more weeks so l will have to wait to do a rotor remeasure. My guess and only one for loss is about .5-1.5mm
What are the Pagid blues temp rated to.....if you go over that temp will they fade??
I look forward to knowing the min thinkness for that rotor
I havn't taken them out for a good work out, but i'm confident all will be good.
DZ....I will PM you my email address for any pics you can help me with on this problem....thanks heaps
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CruizinKO · 5th August 2002, 03:46

Quote:

Originally posted by Apples
Good stuff guys...much needed info.

CruizinKO...Set up a post on that topic or do a search under..... brakes, they are very well covered in this board. The kit for the M5 was custom from Nowack in Germany so it was an optional brake upgrade l chose to take, and Movit don't sell that kit in the USA. I'm sure the Movit 355mm set up would be perfect for M3 M5 X5. They say the Stop Tech brakes are good to. You will get plenty of opinions from piles of users. My Movits are from the Porsche motorsport division so their not the same as most other brake upgrades and hard for me to do a comparo...

I see... I will definately do a search and post if I need more info, thanks Apples!

01M5 · 5th August 2002, 04:04

Davez,

Is the bearing runout problem also noticeable in Stoptech brakes? I would guess the larger the rotor, the greater the risk of the problem-is that correct?

DZeckhausen · 5th August 2002, 05:18

Quote:

Originally posted by 01M5
Davez,

Is the bearing runout problem also noticeable in Stoptech brakes? I would guess the larger the rotor, the greater the risk of the problem-is that correct?

I've only had one StopTech customer with an E39 wheel bearing issue and that car had over 70,000 miles on it. The symptoms included the typical worn wheel bearing rumble (sounds like snow tires) as well as a pad knockback problem. The StopTech brakes were soft the first time you pressed the brake pedal at high speed but were then firm for subsequent applications. After replacing the wheel bearings, the brakes were as firm on first application as second.

The concern with the 380mm rotors is that they are MUCH heavier than stock. I've picked one up at Steve's place (The Ultimate Garage) and was amazed at the heft of those suckers. Combine that with the 19" wheels that are typically required to clear them and you have lots more rotating mass putting stress on the bearings. The concern is that the wheel bearings would then wear out much faster than normal.

The StopTech rotors are not much heavier than stock and, unless you race your car every weekend, I do not expect to see accelerated wheel bearing wear with them.

stever · 5th August 2002, 19:19

if you overheat the Pagid Blues you'll probably get uneven pad deposition and brake vibration before they fade -- they just are not up to stopping the M5 lap after lap when you start to go fast

i agree with DaveZ that Oranges are the minimum for the track, but they may not be enough on demanding tracks, from my experience you might as well go to the Blacks (or Johann's beloved Yellows) if you're going to change pads (which shouldn't take more than 30 minutes at the track -- most of the time is jacking the car up and removing and replacing wheels)

no matter which pad you use on the track (and if you've been using Oranges on the street) you've got to bed the pads during the first session

stick to pads from one manufacturer for compatability of the material deposited on the rotors when switching from street to track pads

i think putting temp paint on is worthwhile -- if something goes wrong you've then got a clue and you're reassured that the pads are in the right temp range -- i found that OEM rear pads were still fine even with the front Blacks working in their temp range

if you want to shop pads, check out some of the Porsche aftermarket guys advertised in Excellence

if the rotors are getting close to minimum thickness then their heat capacity has been diminished -- not good -- similarly track pads should not be run to less than 1/3 of original thickness

Apples · 5th August 2002, 22:59

Quote:

Originally posted by DZeckhausen

The concern with the 380mm rotors is that they are MUCH heavier than stock. I've picked one up at Steve's place (The Ultimate Garage) and was amazed at the heft of those suckers. Combine that with the 19" wheels that are typically required to clear them and you have lots more rotating mass putting stress on the bearings. The concern is that the wheel bearings would then wear out much faster than normal

Have a look at this "BRAKE" Post and click on page 7 and scroll down the last two threads.....l have the weights for my current Movits 380mm fronts and the 322mm rears...caliper/rotor, and the next reply has the weights of the OEM/Movit/stoptech front and rear setup.
And the 380mm Movits are a fair bit lighter then the OEM's as you can see.
The 19 inch BBS LM's are very much the same as the OEM 18's in respect to the weight, so l'm actually down on reciprocating mass, so thats good, but saying that the SO3's are heavier then the old OEM Dunlops, so l wonder what the real total weight is???
http://www.bmwm5.com/vbulletin/showt...eferrerid=2324

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