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Wilwood GT Spec 37 Rotor Life

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358
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128
Location
riverbank
#1
Hey guys,

I am starting to notice Cracking on my Spec 37 rotors from Wilwood. I bought these in hopes that they would hold up better than the regular Ultralite rotors. They're almost twice the cost as them too. Anyways here are some photos. I have about 300 miles of HARD track time on these rotors with 2 Autocross Sessions with about 3000 miles of Daily Driving.

Do this wear look about right?








Appreciate the Help!
 


RAAMaudio

5000 Post Club
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#2
That is what I call heat checked which I have seen rotors last a very long time with it including on all out race cars.

Yours is a bit more severe but with TVC, if you run with the nannies on, even more heat....might be time for ducting some air to the rotors.

My 11.75x.81 GT rotors have around 200 track miles and a lot of pretty hard use from making a lot of tuning runs and jumping on the brakes to get my speed down quickly and have about 1/3 the amount of checking as yours.

Normally GT rotors should be good for a whole race season on a race car without TVC at least.

I would check with somebody that deals in racing that sells these rotors and or Wilwood, give them a call, they can be quite helpful.

I think you are fine but looking into this would be a good idea.

Let us know what you find out, please.

Rick
 


Chuckable

Active member
Messages
559
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90
Location
South Florida
#3
Hey guys,

I am starting to notice Cracking on my Spec 37 rotors from Wilwood. I bought these in hopes that they would hold up better than the regular Ultralite rotors. They're almost twice the cost as them too. Anyways here are some photos. I have about 300 miles of HARD track time on these rotors with 2 Autocross Sessions with about 3000 miles of Daily Driving.

Appreciate the Help!
Any update on this?
 


OP
J
Messages
358
Likes
128
Location
riverbank
Thread Starter #4
Any update on this?
That is what I call heat checked which I have seen rotors last a very long time with it including on all out race cars.

Yours is a bit more severe but with TVC, if you run with the nannies on, even more heat....might be time for ducting some air to the rotors.

My 11.75x.81 GT rotors have around 200 track miles and a lot of pretty hard use from making a lot of tuning runs and jumping on the brakes to get my speed down quickly and have about 1/3 the amount of checking as yours.

Normally GT rotors should be good for a whole race season on a race car without TVC at least.

I would check with somebody that deals in racing that sells these rotors and or Wilwood, give them a call, they can be quite helpful.

I think you are fine but looking into this would be a good idea.

Let us know what you find out, please.

Rick


I will contact Willwood tomorrow and ask them. Based on other Trackday forums that I have checked, this is normal when the rotors get driven hard. Once a crack develops from the hub straight out to the edge, it is time to replace the rotor.
 


Chuckable

Active member
Messages
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Location
South Florida
#5
I'm no expert, but have seen rotors like yours and they were considered normal wear. But since brakes are obviously essential, best to check with Wilwood like you're doing. Please let us know what they say!
 


maestromaestro

1000 Post Club
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#6
I have Spec 37s and after just two days of track, the slots on the fronts are pretty much gone, with Carbotech pads. [Great performance overall - some fading after they got to temp, but then stayed consistent for the rest of the session. But, boy, were these hot - I could not even touch the rim, and the rotors were still over 350F about 10 minutes after I got off the course.]

I don't see any cracking though. Is there a "minimal acceptable thickness" on those?
 


Siestarider

Senior Member
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Stuart
#8
I temperature tested my WW BBK in August, surprised to find peak temps at disc edge did not hit 1000F. This with GT 37 rotors and Carbotech XP10 pads. And no mercy on brakes, I brake hard and late on track, and running on sticky Rivals.

Stock rotors with stock pads were exceeding 1250 F at edges without cooling, and still exceeding 1000 F with cooling. No nannies, CMB duct plates and my design fog facia vents plumbed with 2" hose seem to work better with WW setup than with stock. Extra rotor mass cannot be it, the GT 37 actually weighs less than stock rotor. Limited slip same for both.

The CMB duct plates probably work better with WW setup, get more air into rotor centers than stock setup allows. I left my XP 10's on after last track day just to see how they work on street. A bit grabby but so noise. Next time I have wheels off I will mike the thickness and get an idea of wear on street. I will be surprised if its much, I am easy on brakes on street.
 


M-Sport fan

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Princeton, N.J.
#9
^^^Thanks for that info, and the future mic readings. [thumb]

One question though, the XP-10s will slow the car down, and even stop it dead quickly on a first, stone cold, brake hit on the street?! [???:)]
 


Siestarider

Senior Member
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Stuart
#10
^^^Thanks for that info, and the future mic readings. [thumb]

One question though, the XP-10s will slow the car down, and even stop it dead quickly on a first, stone cold, brake hit on the street?! [???:)]
At least as good as stock setup, which surprises me to no end.
 


maestromaestro

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#11
I called WW today to find out if they have a "minimal thickness" on the rotors - again, what with the slots gone after 10-12K miles using Carbotechs XP8, and they gave me the GloMar response, saying essentially that once the slots are gone, the rotors are "questionable" (or, better yet, as they put it "if you are questioning the rotors"), time to replace them. These are originally 0.81" (20.6 mm) thick and the slots are gone with the remaining thickness being 18.5 mm; so - their view is that the rotors are only good for about 90% of the original thickness, which is baloney. I was actually told by the guys that sold me these (not WW) that the minimal thickness is 17.46 mm (oddly precise), which is still awfully bad as a proportion of the original thickness... This, from materials property perspective doesn't make a lot of sense - as the clamping force on the marginally thinner rotor can't be impacted all that much. The slots are there, ostensibly, for two purposes - to route the hot gas and to prevent pad material build-up. I don't see any difference in performance on the track w/o the slots, and (I am using degassed pads) no uneven wear on the pads or the rotors.

Hate to toss what looks like a perfectly good rotor to me; plus, they are not exactly cheap either. Thoughts?
 


Todd TCE

New Member
Messages
2
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3
Location
tempe
#12
Browsing...came upon this thread.

For thickness use the GT rotor can be used down to roughly a 10% reduction in thickness; .750" or about 19mm. Can they be used beyond that? And safely? There is not direct answer to that. For use on a 1000lb buggy perhaps. On a and open track day, at speed on a 3500lb car on an open track day? I'd say not. Don't do it.

Keep in mind these rotors and the entire 12.2" DP6 kit was never intended for open track use. Or the ST. It was built as a low cost, street enthusiast kit. It's not even in best trim suited to extended use open tack day use with good pads and high speeds. If your vendor sold it to you as such they should learn more about the product. Can it be used for such? Of course it can. With the understanding that it's light weight will give you but modest use on this car with the speed/weight balance. There's a reason the heavier kits are more money, take up more room, require wheel spacers, have larger pads....you get the idea.

The pad wear I'm seeing is most likely from use of track or race pads on the street more so than track day use. Someone suggested Brand X Compound Y Race Pad? If they did not tell you to put them in the day of the event and remove them after they did you a disservice. The BP10 supplied standard is suited to the street. 20 street and very light few laps of track day. Moving to real track pads such as Poly B or H will meet the needs of the heat generated. But leaving such pads in for the street, regardless of brand is a bad idea. "But these pads are dual purpose"...no. No pad is dual purpose. Regardless of what anyone tells you. Dual purpose pads are a compromise of function, fade, wear and cost. They do a modest job of all that and a poor job of most specific ones.

Keeping that system cool will help also. Proper ducting can go a long way.


Hope some of that helps. If you choose to disagree that's ok too. I've sold this kit, and others in the same flavor, for nearly 20yrs now and seen the good and the bad. It's an excellent product for quality and value. But there's a reason it's only $800 and not $2k.
 


maestromaestro

1000 Post Club
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#14
Browsing...came upon this thread.

For thickness use the GT rotor can be used down to roughly a 10% reduction in thickness; .750" or about 19mm. Can they be used beyond that? And safely? There is not direct answer to that. For use on a 1000lb buggy perhaps. On a and open track day, at speed on a 3500lb car on an open track day? I'd say not. Don't do it.

Keep in mind these rotors and the entire 12.2" DP6 kit was never intended for open track use. Or the ST. It was built as a low cost, street enthusiast kit. It's not even in best trim suited to extended use open tack day use with good pads and high speeds. If your vendor sold it to you as such they should learn more about the product. Can it be used for such? Of course it can. With the understanding that it's light weight will give you but modest use on this car with the speed/weight balance. There's a reason the heavier kits are more money, take up more room, require wheel spacers, have larger pads....you get the idea.

The pad wear I'm seeing is most likely from use of track or race pads on the street more so than track day use. Someone suggested Brand X Compound Y Race Pad? If they did not tell you to put them in the day of the event and remove them after they did you a disservice. The BP10 supplied standard is suited to the street. 20 street and very light few laps of track day. Moving to real track pads such as Poly B or H will meet the needs of the heat generated. But leaving such pads in for the street, regardless of brand is a bad idea. "But these pads are dual purpose"...no. No pad is dual purpose. Regardless of what anyone tells you. Dual purpose pads are a compromise of function, fade, wear and cost. They do a modest job of all that and a poor job of most specific ones.

Keeping that system cool will help also. Proper ducting can go a long way.


Hope some of that helps. If you choose to disagree that's ok too. I've sold this kit, and others in the same flavor, for nearly 20yrs now and seen the good and the bad. It's an excellent product for quality and value. But there's a reason it's only $800 and not $2k.
Well, I have bought a a new set of rotors, and another set of XP8s. I hear you about changing out the pads for the track - that's what a lot of people do. The trouble is that the design of the WW calipers is such that I have to remove them from the rotors each time. And - it is a pain in the neck, literally, the way they attach to the front brackets - making sure that the shim washers don't fall out as you threading in the bolts. That, and the fact that I drive with a great deal of "spirit" on the H-town highways, so - my street tires have a 200 UTOQ rating.
 


Sekred

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#16
General rotor wear limit is in the range of 2-2.5mm, that's after any machining if you were going to reuse the rotors. OEM discs are 23mm with a limit of 21mm thickness. I am surprised at the thickness of the WW rotors at 20.6mm, no wonder they fit behind the OEM rim and no wonder they seem a little prone to overheating during track use. My K-Sport discs are 28mm, over engineered really and heavy as well.
 




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