The Lotus Cars Community banner

1 - 9 of 9 Posts

·
Registered
Joined
·
650 Posts
Discussion Starter #1
My thickness looks OK but starting to see small cracks on my front Ultradisk rotors. nothing big or to the edge just small hair line cracks. Any reason for concern or should I replace now? I running Carotech XP10 XP12 pads and love them and have a two day track weekend June 30/July 1

 

·
Registered
Joined
·
841 Posts
Take a set of spare rotors to the track. Swap them out when a crack gets to an edge or when you can catch your fingernail on one.
 

·
Premium Member
Joined
·
606 Posts
What causes these cracks? I have seen them too.

Obviously the answer is brake use but is it: high temp, rapid cooling, normal result of heat cycling, etc?
 

·
Registered
Joined
·
216 Posts
My thickness looks OK but starting to see small cracks on my front Ultradisk rotors. nothing big or to the edge just small hair line cracks. Any reason for concern or should I replace now? I running Carotech XP10 XP12 pads and love them and have a two day track weekend June 30/July 1

Try BOE's new rotors...Very nice, add the SS pistons you'll be pleased with them as well. I have had none of these cracks since I changed . The cracks you have are similar to what I was seeing but mine were worst. I too have the REV 400 so I believe we are just getting to the point that the brakes are playing catch up to the power...
 

·
Banned
Joined
·
3,239 Posts
Those wiping grooves are machined to your minimum thickness. Once you can't see the grooves any more, replace the rotors. Keep an eye on the back side too. Those are not cracks you see on the surface of the discs. The metal crystallizes at those high braking temperatures on the surface and that is what you see…some of the crystalline demarcation lines. The discs will not crack along those lines.
 

·
Registered
Joined
·
650 Posts
Discussion Starter #6
Those wiping grooves are machined to your minimum thickness. Once you can't see the grooves any more, replace the rotors. Keep an eye on the back side too. Those are not cracks you see on the surface of the discs. The metal crystallizes at those high braking temperatures on the surface and that is what you see…some of the crystalline demarcation lines. The discs will not crack along those lines.
Thank you Sir!
 

·
Registered
Joined
·
713 Posts
What causes these cracks? I have seen them too.

Obviously the answer is brake use but is it: high temp, rapid cooling, normal result of heat cycling, etc?
Yup, thermal expansion and contraction causes this when the rotors get super hot. Get a set of spares. Those are still safe to run, as long as the cracks are tiny like that. The rule of thumb is that if you can catch a nail on it, it's too big.
 

·
Plug Whisperer
Joined
·
6,305 Posts
Brembo, says:

"BRAKE DISC
Check carefully the disc braking
surfaces.
The disc can’t be used again if:
- on the braking surfaces there are
cracks having length higher than 5
mm; in case the crack begins from
the external or internal diameter,
even if the length is shorter, the disc
must be replaced (see Fig. 8).
- It has a wear of 1 mm compared to
the new thickness (0,5 mm on both
sides);
- The braking surfaces show scorings,
which can damage the correct pad/
disc contact."

Just one source...
 

·
Super Moderator
Joined
·
5,453 Posts
Brembo, says:

"BRAKE DISC
Check carefully the disc braking
surfaces.
The disc can’t be used again if:
- on the braking surfaces there are
cracks having length higher than 5
mm; in case the crack begins from
the external or internal diameter,
even if the length is shorter, the disc
must be replaced (see Fig. 8).
- It has a wear of 1 mm compared to
the new thickness (0,5 mm on both
sides)
;
- The braking surfaces show scorings,
which can damage the correct pad/
disc contact."

Just one source...
That isn't right. The original thickness is 26mm and minimum is 24mm so at 1mm wear either side it is toast.
 
1 - 9 of 9 Posts
Top