Dr.Ron

So I'm at the track now and my wheel lugs loosened up after each session on the fronts only.
I'm on new to me ccw's and conti slicks for the first time. I have a 2011 Carbon Edition Z06. I know some guys say they put a spacer before the front wheels go on, but it looks like I don't need them as I believe the wheel to be flush on the hub. Plus, the spacer shortens the stud so less threads for the lugs to grab.
Any suggestions or experience with this issue?
I'm seeing about 1/4-1/2 turn loose at most.

Thanks.
Ron

andy3101

What are you torquing the lugs to? Ft/lb. on our race cars we torque to 100. We take wheels off after every session so they get torqued to 100 for every session. Standard operation procedure for track cars.

It's not uncommon for them to loosen.

Dr.Ron

It was at 100, but I went to 106/108.
Just sstrange the rears really didn't loosen and it never happened before for me basically.

RDnomorecobra

hey Ron, not too unusual. remember the slicks put more demand on everything so that may be contributing.

Do not re-torque while they are real hot after a session. Bolts will shrink while cooling effectively increasing the amount of torque. If you went to 106/108 while hot I would back them off until they cool, then re-torque to 100.

Dr.Ron

Ok. Ray, so far after 2 sessions (actually 1, because they black flagged the group on my warmup lap and we pitted for a while. Then I got just 3 laps and we got the checkered flag) my best lap time is 2 seconds faster and I'm still learning the slicks!

RDnomorecobra

They are fun. NJMP? which track? I'm jealous. It's a beautiful day out today.

Dr.Ron

Yes, Thunderbolt

ErnieN85

normal with new wheels. they will stop after a few days of this keep checking them

phipp85

You need to have a spacer on your front wheels unless the backside of the wheel has been radiused or beveled specifically for your rotors. If they haven't been machined then you have virtually no contact between the rotor hat and bearing surface of the wheel leaving about a .150" gap in that area.

I run a .160" thick spacer and installed longer ARP wheel studs to get more thread engagement.

froggy47

Please explain more of this. I have used dozens of rims with many different patterns of contact on the back sides, flat, hollowed out for weight etc.

Never heard of this.

Also, not trying to argue here, but, if the spacer is a flat spacer how does that change anything? If it's a fancy spacer (I have seen some that have the same cut out pattern as the rim) how does that change anything?

Talking hat contact to rim contact area?

Either type spacer you end up with the same contact pattern, right?

PS I agree NEVER torque or retorque hot studs/nuts.

I do use spacers all the time, but to change the track so tires clear the fender liner or to clear brakes. OF COURSE you need appropriate length studs.

I think the OP just got some bad info & simply needs to retorque (COLD) between sessions & eventually the loosening will moderate.

fcarga

What Froggy47 said! Be sure to use star pattern when tightening and just one click on the torque wrench.

phipp85

My information only applies to the OEM front ZR1 carbon ceramic rotor. Yes I'm talking about the rim contact area to rotor hat area.

froggy47

Again, not to argue just to learn. Is this in the owner's manual?
Who told you to do it?

I'm from the school, where I don't just do stuff because someone tells me to. It needs to meet my common sense test. I like to understand things b4 I do them.

Please provide more info.

Actually I am thinking about trying to find a Carbon Edition, so this really interests me.



Does anyone have a picture of the two surfaces we are discussing. The hat and the back of the rim. It's hard for me to picture that there is something different on a ZR1 brake regarding those two surfaces.

phipp85

Are you serious? No, there is no information about running aftermarket wheels with continental slicks in the owners manual.

Common sense told me to use the spacer. The rotor hat is recessed and the back of the wheel is flat. The diameter of the back of the wheel is larger than the diameter of the recessed area on the rotor hat.

Werks

Not trying to create a debate but I've been running different wheels with ZR1 CCM rotors on the track since 2011 and have never used a spacer. Maybe the wheels from Forgeline or Finspeed that I have a machined specifically for CCM's???

dfinke23

I will chime in when I get the kids to bed, but unless your fronts were cut specifically for the ZR1 hats, you need the spacers. I will outline why later, but you are lucky you didn't lose a wheel.

phipp85

No experience with Forgeline but when I was speaking with Finspeed about ordering a set he said they could make them so a spacer is not required if that's what I would like. I would think yours are made to run without a spacer.

I have a set of CCW's and when I called them to ask about running them with ZR1 rotors John said always run a spacer with that particular rotor. CCW may offer wheels cut specifically for the ZR1. When I spoke with him it was clear that he did not. Dr. Ron said his wheels are "new to me" implying that he didn't buy them directly from CCW so he may not be aware of the need to run the spacer.

I was just trying to look out for the guy so he doesn't stuff his car into a concrete barrier because of something he may not be aware of. If your aftermarket wheel does not occupy any more space on your rotor hat than your OEM wheel does then you are good to go. I will try to post a picture this weekend if I have time.

froggy47

Yes please explain to me in as much detail as you can (pictures would probably do it, even a picture of an illustration).

If the rim surface we are discussing is flat and you put a flat spacer on top of a flat rim surface what in the heck have you changed CONTACT SURFACE wise?

If the rim surface area is smaller (area) than the rotor hat area, and you add a bigger (area) spacer to make the contact area match the hat, well, unless you weld it on, one side is touching (take a guess) that's right AIR, the other matches the hat (I guess). So yeah maybe that would make you feel better, but wouldn't make me feel much better.

Unless I've got it all wrong, which is possible.



All the spacers I use match the hat area plus the contact area of the rim. So zero gain/loss/effect of the contact area.

Werks

That must be it then, both sets of wheels were ordered for my car from Forgeline and Finspeed.

0Finspeed

Think of the rotor hat (wheel mounting surface) as a 9" diameter flat disc and the back pad of your wheel is 7" in diameter. No problem with this, as you have good, solid, load bearing contact. No spacer needed.

Now, with the CCB's, think of your 9" flat disc (hat) and your 7" back pad....
but this time the 9" flat disc has a 0.160" (~4mm) deep section of the center machined out, with a diameter of 6.900". With the back pad of your wheel being 7" in diameter and a 6.9" diameter, 4mm deep section of the rotor hat (wheel mounting surface) removed, you only have a .100" wide ring supporting the entire load you are putting through the wheel, and a 4mm gap under 95+% of the back pad. The spacer fills this gap and allows for solid contact with the entire back pad.

The hats are this way bc that's how Ferrari spec'd them and GM did not want to spend the money to have a hat machined to accept their wheel as it was cheaper to lathe turn a step in the backpad of the wheel to make that diameter fit the hat. Running without the spacer is VERY dangerous on the street, and worse on the track.

Call me tomorrow and I can get you a set.... And I do not recommend driving the car on those wheels until you have them.

BTW, all of the measurements listed above are to illustrate what is going on, and are not precise.

Br,
Daniel