07-23-2022, 12:30 PM | #1 |
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rotor cracks
Looking at buying an M2 competition. Went to the dealer today and noticed these cracks in the rotors
https://cdn.discordapp.com/attachmen...723_100325.jpg He insists they are fine and won't need to be replaced but I am skeptical. Car has 23k miles on it and the rotors are worn that bad. I am assuming this means the car has been tracked heavily (not a deal breaker, kind of expected on a car like this). I tried getting 2k off the price to replace the rotors but they refused. What are your guys thoughts on this? Am I crazy for thinking these rotors will need to be replaced soon? |
07-23-2022, 12:42 PM | #2 |
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Are you able to catch your fingernail in any of the cracks? If not, you're probably good to go for a while. These discs are notorious for developing those cracks even with canyon driving, hard street driving, and not just track use.
I took mine in a few years ago and the dealer had a printout ready to hand me saying that it was normal on "performance brakes" and not to worry. I ended up replacing them with StopTech slotted rotors later due to the frequent track use and peace of mind.
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07-23-2022, 12:45 PM | #3 |
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Those darker ones you can catch your fingernail in. I know the brakes aren't completely gone yet but they are definitely more than halfway through their life. Dealer told me the same thing, but these just look too far gone imo.
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07-23-2022, 02:26 PM | #4 |
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Those stress cracks indicate extreme heat for a sustained period of time and the grooving/deposits within the holes suggests that these rotors have seen some shit. Likely tracking.
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07-23-2022, 02:41 PM | #5 |
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Yeah I passed on the car and lost my 1k deposit. Really disappointing, I literally had the check from the bank to buy it and everything. Guy said there was a PPI for the car and when I asked him for it he said this
View post on imgur.com Just really disappointing overall I drove 7hrs to buy this car I wouldn't recommend these guys to anyone. |
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07-23-2022, 04:08 PM | #6 | |
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07-23-2022, 04:56 PM | #8 | |
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07-23-2022, 07:22 PM | #9 |
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I dont want to start a witch hunt, but I can DM you the link if you want.
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07-23-2022, 08:10 PM | #10 | |
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Also, I looked at a dozen or so m2 comps on autotrader and I'd never seen the brakes in that state (all of which had close ups of the brakes). This car doesnt have any close ups of the brakes on the autotrader post (I wonder why). Was a huge oversight by me to not think to check that. All this stuff combined to make me feel like the deal was sketchy and back out. Maybe it wasnt the right move, but my gut was telling me this was sketchy. |
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07-23-2022, 11:16 PM | #12 |
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07-24-2022, 01:09 PM | #13 | |
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Dirty and missing valve stem caps...but no cracks that I can see. Hope this is helpful. |
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07-24-2022, 01:45 PM | #14 |
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Conversely here are mine with 17k, garage queen. The cracking does not mean the rotors need replaced or will spontaneously combust, but it does suggest tracking and a SHORTER rotor life. To be clear there is nothing wrong with tracking the car, that's what it was made for in part, but OP was correct to get the dealer to replace them or get a credit. It sounds like not only did the dealer scoff, they didn't offer any concession whatsoever and then sent a condescending response that the vehicle was sold to someone else.
OP, you probably dodged a bullet all around. There are plenty of clean cars (and dealers) out there. |
07-24-2022, 06:36 PM | #16 |
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[IMG][/IMG]
2NH brakes after 7 track days, maybe 10 hours on track. Running Ferodo DS2500 pads, Castrol SRF brake fluid, and titanium caliper shims. 25,500 miles total. Edit: maybe that was a press car. Went through that jungle looking for my 1M. Or another possibility it was tracked and improperly cooled-down. This also points to it being a press car. Perillo BMW of Chicago has been known to resell them. |
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07-24-2022, 07:18 PM | #17 | |
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07-25-2022, 08:13 AM | #18 |
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I agree that the car has probably been on the track. The rotors are also probably ok. You would need to make sure that there are no cracks connecting the drilled holes. That is a major failure waiting to happen.
P.S. If you are tracking your car, don't use drilled rotors. |
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07-25-2022, 08:58 AM | #19 |
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All other things being fine, I wouldn't have forfeited a $1000 deposit over this. Could have used that money for new rotors instead of wasting it.
Also, aren't there state laws against non-refundable deposits? |
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07-26-2022, 12:19 PM | #20 |
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Stress cracks like those in the pics are a result of rapid expansion and contraction of the discs, which is what happens on the racetrack. Discs that are only driven on the street typically don't show that type of wear. Below is an article I wrote on interpreting disc wear. The discs shown in the pics are our AP Racing units, but the same idea applies to any iron brake disc. These pics show you how our customers' discs would progressively crack when beaten on the track repeatedly. They provide an idea about what everything from 'minor wear' to 'throw them out' looks like.
"When is it time to replace my iron brake discs?" |
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07-26-2022, 04:45 PM | #21 |
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07-27-2022, 03:40 AM | #22 | |
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Still went to the track 4 times after this picture was taken as it still had enough thickness |
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