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how do i know if my rotor is cracked?

  • Thread starter Thread starter DerekStangGT
  • Start date Start date Sep 13, 2005
D

DerekStangGT

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its my stock rear rotor that might be cracked. ive been doing a lot of hard driving lately. Lime Creek for those in the Austin area, and i drive City Park rd hard every day on my way to class. anyway, the driver side rear rotor has two lines going from the hub (inside) all the way to the outside of the rotor. i'd snap a pic, but my digi is broken is this harmful to continue driving?
 

Pughman

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mine is to .. its like a small line... and i have been on mine for like 3 months now...
 
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DerekStangGT

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Pughman said:
mine is to .. its like a small line... and i have been on mine for like 3 months now...
Click to expand...
exactly, its like a small line, but i dont know if its a crack or what
 

tomustang

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well it ain't a marker stain! you running the barake too hard?
 
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DerekStangGT

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tomustang said:
well it ain't a marker stain! you running the barake too hard?
Click to expand...
i have been pretty hard on the brakes lately. i was just throwing around ideas, do you think i could have cranked the E-brake too hard one time? probably not, but i was just trying to think of other things.
 

tomustang

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excessive heat, they are stock rotors, just a matter of time
 
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DerekStangGT

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tomustang said:
excessive heat, they are stock rotors, just a matter of time
Click to expand...
is it unsafe to continue to drive on them?
 
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wickedgt70

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I would replace it soon. Most likely it will only shorten the pad life. Worst case is if it chunks off and wrecks the caliper/axle/etc.
 

tomustang

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it's already scratching the pad (barely) so you might as well change both pads + rotors anyway, I wouldn't worry about it, just don't drive too hard
 

sgarlic

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I'd say you're probably ok to drive til you can get a new one (if indeed it is cracked,) but if it goes, don't be surprised if you have to step on the brakes extra hard to stop.
 

tomustang

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it's in the rear so it won't affect braking much, i think the rear ratio is less than 40% power
 

300bhp/ton

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tomustang said:
it's in the rear so it won't affect braking much, i think the rear ratio is less than 40% power
Click to expand...
contradicting youself again Tom.

tomustang said:
well it ain't a marker stain! you running the barake too hard?
Click to expand...
tomustang said:
excessive heat, they are stock rotors, just a matter of time
Click to expand...
If it won't affect the braking they wouldn't be doing much, but then how could you run them too hard?
 
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Kilgore Trout

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300bhp/ton said:
contradicting youself again Tom.



If it won't affect the braking they wouldn't be doing much, but then how could you run them too hard?
Click to expand...
Wow! I always though you knew a lot about cars 300bhp/ton... Guess not...

Just because the rear brakes are only 40% of the brake force does not mean that they cannot be pushed to the limit of the braking that they were designed for. Ever heard of a performance envelope? They were pushed to the limit of their PE and failed...
 

300bhp/ton

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Kilgore Trout said:
Wow! I always though you knew a lot about cars 300bhp/ton... Guess not...

Just because the rear brakes are only 40% of the brake force does not mean that they cannot be pushed to the limit of the braking that they were designed for. Ever heard of a performance envelope? They were pushed to the limit of their PE and failed...
Click to expand...
not at all, it was more to just wind Tom up, lol.

As for the brakes them selfs, well that would depend. Unless cracked rear disc's is common on Mustangs (never heard/read it before myself) I would think it very unlikley that it is cracked.

As cracking would be associated with rapid heating and cooling over a short period of time, cracks can appear but it is far more common in cross drilled disc's as the hole introduces a weak spot where the crack will form.

It would be quite likley that any marks on the disc are just that marks, either from the pads or just part of the metal.

If the disc's are getting on a abit and are well used then blueing, glazing and uneven wear are much more likely. If they are already in this condition then there may cause for them to crack.

If there appears to be nothing wrong with the operation of the brakes then I personally wouldn't worry too much. If you do replace them make sure you do the pads as well.

It might be worth lifting the wheel off of the hub and having a closer look at the disc, if it is indeed cracked then it should become obvious. If it is just a mark then try cleaning that area of the disc with a cloth and some vapour degreaser. You may be able to do this with out taking the wheel off the car, depending what style wheels you have.
 

timeless2

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300bhp/ton said:
contradicting youself again Tom.



If it won't affect the braking they wouldn't be doing much, but then how could you run them too hard?
Click to expand...


He also fails to mention whether or not he was doing excessive burnouts (heavy rear brake use) or e-braking for fun. Those two can cause the entire stress of the braking effort to be pointed directly at the rear brakes.
 

Pughman

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git-it-83 said:
He also fails to mention whether or not he was doing excessive burnouts (heavy rear brake use) or e-braking for fun. Those two can cause the entire stress of the braking effort to be pointed directly at the rear brakes.
Click to expand...


i for one did NOT do that to my car .. and i have a crack in mine..


where to get some new ones ? not stock , something nice ?
 

timeless2

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Pughman said:
i for one did NOT do that to my car .. and i have a crack in mine..
Click to expand...

Those aren't end-all indicators, but rather two events where I have seen someone generate excessive heat and subsequent fractures.
 

tomustang

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Power Slot makes nice replacements

300bhp/ton - you think mustangs are made if high quality?
 
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DerekStangGT

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git-it-83 said:
He also fails to mention whether or not he was doing excessive burnouts (heavy rear brake use) or e-braking for fun. Those two can cause the entire stress of the braking effort to be pointed directly at the rear brakes.
Click to expand...
i dont have the $$ to do burnouts, nor E-brake. i do drive hard and brake hard though

Pughman said:
i for one did NOT do that to my car .. and i have a crack in mine..

where to get some new ones ? not stock , something nice ?
Click to expand...
look on ebay and search for "mustang rotors". i found some nice Brembo drilled/slotted rear discs for $120
 
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