James88

Thanks Rob
I'll have him take off one front wheels while I'm there, what should I be looking out for?

993GT

No worries Jim!
If he is running GT2/3 spec discs on a TT upright/front end, the disc will be offset towards the outward portion of the caliper, not centred as it should be
Cheers,
Rob

James88

So this is not a good thing then.

993GT

Suboptimal anyhow, would need to measure piston heights and calculate if there is any danger of failure when pad life is low

James88

Great, now I'm worried.

993GT

I would only be concerned when pads are down to the last 1mm or so(and again, there may be no danger even when worn to backing plate), to compensate the offset difference.
I will probably rebuild my calipers when I put my car into winter storage, will try to take the critical measurements/calculations when they are apart.
Get 997TT spec discs when you can....or smarten up and get a 2wd/GT2 front end done

James88

Just spoke to him and he re assured me that everything lines up and is true and correct. Like you said once these rotors wear out I'll be replacing with 997TT ones.

993GT

I would check it out and verify measurements just for peace of mind...I see no issue running them for now

James88

My indie said it will be just fine but you, Kevin and Pwdrhound have changed my mind, they're not centered, they're out by about 1.5mm.
I told him if he cant supply correct 997T sized ones l don't want them and put my old ones back on. He is now looking for 997t ones.


Pwdrhound
"The offset between the GT3 and TT rotor is different by 1.5mm. The GT3 rotor will bolt up but will not be centered relative to the caliper centerline. You want it centered. Trust me. Look at it with your own eyes. If the rotor lines up perfectly than you have a TT rotor, not gt3. I have done this a thousand times. I would find a competent shop Jim. You can run a TT rotor with a 1.5mm spacer on a gt3 but not the other way around."

SteveMFr

Don't want to throw a monkey wrench in the discussion, but I know of guys here in Germany who are running GT3 rotors on 6TTs with no issues. The pad support pins need to be shortened to make this work, but that is about it. The difference is not great enough to cause problems on the other side even if you run the pads all the way down to metal on metal. And the calipers don't care if there is a little more fluid on one side than on the other.

I am not running this setup on my car (just to be clear) and if I were installing new rotors I'd def go with proper rotors so that everything is centered, but if I already had this setup on my car I would run with it till I needed new rotors.

993GT

posted over on 6SO; am glad you are doing the right thing! no need to take unnecessary chances due to the tech..
cheers,
Rob

993GT

Good to note!
Jim, make sure your tech has not cut down the pad retaining posts...if he has, replace them!

James88

He's asked for an extra $300AUD = $216USD for the 2 front 997T rotors, he said they cost him double that but is prepared to split the cost. Is it OK to use lightly used old pads with new rotors? I will also ask if he cut the pins on the pads, if he did then no go like Rob said.

James88

He said he didn't cut pins but knocked them back a little, does this sound ok?