[Mountain]

Originally Posted by TheRealJA105

Strano and another fast guy went slower on them than G3s at VIR this weekend. First data point and not enough time to be really conclusive.

I'm betting they will be exactly like RE71Rs. Faster than the G3 at autocross and for 1 TT lap, but can't knock the Yok off the top step for either of those things.

Pick your speed and wear per dollar that you can stomach and decide how badly you want to win...

I was looking for his comments about the GY vs TR660 at VIR, but did not see them. I did see him mention the RT660 was very slippery at, first, being brand new and the GY already used. Good to know.

[AJD]

Are the 660s significantly wider than comparable 71r's? I've been running 275/35/r19 re71rs on 8.5" and 9.5" wheels for my 2.0 1LE to stay DS legal. I'm noticing the section width on comparably sized 660s is 0.4" wider. The Bridgestones were no problem, but should I be concerned about shoehorning the 275 Falken on the 8.5" wide fronts?

[Mountain]

Originally Posted by AJD

Are the 660s significantly wider than comparable 71r's? I've been running 275/35/r19 re71rs on 8.5" and 9.5" wheels for my 2.0 1LE to stay DS legal. I'm noticing the section width on comparably sized 660s is 0.4" wider. The Bridgestones were no problem, but should I be concerned about shoehorning the 275 Falken on the 8.5" wide fronts?

They seem to run a bit wider, in general, to the RE71R. But... it may be size-dependent. I've only seen pictures online of various sizes on various width wheels, various comparisons to RE71R, Rival-S, RS4, A052 and various Nittos.

Some are saying the sidewall seems softer than the RE71R, some are saying it's similar

I can tell you that the 275 19"s fit more like a 285 on a 10" wheel and do look a bit pinched on a 9.5"...

The TireRack dimensions certainly suggest the 265/35R19 RT660 is more in-line with a 275/35R19 RE71R. I have seen a picture of the RT660 255/35R18 on a 9.5" and it fit perfect/ever-so-slight stretch.

I actually have on order 275/30R19 and 315/30R19 (can't source 305/30 for a while) in the RT660 for my SS 1LE (running 19x10/19x11). Seeing as you are in Detroit, you can take a look once autox starts up.

If I were you, I'd run 265/275 or 265/265 in the RT660 on the Turbo 1LE.

[funked1]

I am thinking of 295/35/19 and 315/30/19 on 19x10 and 19x11 Apex ARC-8 w/ stock offsets. Anybody see any problems?

[TheRealJA105]

Strano ran them again on his vette at Summit Point and got almost identical laptimes vs G3s.

[DaveC113]

Originally Posted by funked1

I am thinking of 295/35/19 and 315/30/19 on 19x10 and 19x11 Apex ARC-8 w/ stock offsets. Anybody see any problems?

Fronts may be too tall.

[funked1]

Like in terms of clearance?

[Mountain]

Originally Posted by DaveC113

Fronts may be too tall.

Ditto

27.2" front with a 26.3" rear... changing the rake of the car. should be better for drag racing.

Let's look at it in maybe another way: 765 rev/mile front vs. 791 rev/mile rear

Stock is a split of +14 rev/mile in respect to the front (front is 14 revs faster than rear), whereas you would be going -26 rev/mile in respect to the front (rear is 26 rev/mile faster than front).

[DaveC113]

Originally Posted by funked1

Like in terms of clearance?

No, as Mountain said the OEM fronts are smaller vs the rears. You can run square but I would never run a larger diameter front vs rear on this car. You're probably better off with a stock-like stagger vs square, but you can rotate square, that's it's main draw.

Personally, I'd go 315/18 square on 11.5 or 12s using spacers + camber plates + grinding a bit of strut up front. Probably ~40 offset w/ 20mm spacers and +1" wheel studs, maybe 5mm spacers out back + moving the wiring. A bit of work, lol...

Or stick with stock widths and offsets with 275/30 and 305/30, then you can keep the BS classification.

[AustinTXracer]

The 285/35R19 front and 305/30R19 rear setup I ran last will definitely not play well with the PTM. As in it will only give you full throttle if you turn everything off. You'll need to either go square or keep the front smaller than the rear to take advantage of any of the traction management stuff. Works fine with it all off though - just looks a little weird.

[AustinTXracer]

I'm loving the 275F/305R RT660 setup - two events in a row for top PAX, and I got FTD on the one this weekend. My car is all stock with alignment and the balance is great.

[AustinTXracer]

Can confirm the RT660 275/30R19 runs wide and is pretty much exactly the same width as the 285/35R19 RE71R. The RT660 305/30R19 is not oversized and is exactly the same width as the 305/30R19 RE71R.

[Mountain]

Originally Posted by DaveC113

No, as Mountain said the OEM fronts are smaller vs the rears. You can run square but I would never run a larger diameter front vs rear on this car. You're probably better off with a stock-like stagger vs square, but you can rotate square, that's it's main draw.

Personally, I'd go 315/18 square on 11.5 or 12s using spacers + camber plates + grinding a bit of strut up front. Probably ~40 offset w/ 20mm spacers and +1" wheel studs, maybe 5mm spacers out back + moving the wiring. A bit of work, lol...

Or stick with stock widths and offsets with 275/30 and 305/30, then you can keep the BS classification.

Right. GM programs a certain expectation per vehicle in respect to what the wheel/tire package is on the vehicle (so, think about wheel revs or wheel speed deltas and how the vehicle computer will monitor that for TC, Stab., e-Diff, etc). I have heard... that even the TMPS data is monitored to a minor extent (pressure and temperature).

The various sensors are all there for a reason. OEs will harness the data as much as they can to get the vehicle to perform better/their criteria and these new vehicles have more linked systems than in the past... sure, there are likely allotted allowances in things like wheel speed deltas, but how tight those deltas are are likely reliant on the vehicle engineering team's collective decisions, with the potential usage of the vehicle in mind, and are really not known to the public unless someone tests various setups back-to-back. This isn't to say the car won't drive within, whatever, 95% of it's capability, but... I've heard of some "findings" on these newer vehicles after "weird things" happen, you're attempting 10/10ths and your setup is very off from OE setup expectations. Just saying.

[foshjowler]

Originally Posted by Mountain

Right. GM programs a certain expectation per vehicle in respect to what the wheel/tire package is on the vehicle (so, think about wheel revs or wheel speed deltas and how the vehicle computer will monitor that for TC, Stab., e-Diff, etc). I have heard... that even the TMPS data is monitored to a minor extent (pressure and temperature).

The various sensors are all there for a reason. OEs will harness the data as much as they can to get the vehicle to perform better/their criteria and these new vehicles have more linked systems than in the past... sure, there are likely allotted allowances in things like wheel speed deltas, but how tight those deltas are are likely reliant on the vehicle engineering team's collective decisions, with the potential usage of the vehicle in mind, and are really not known to the public unless someone tests various setups back-to-back. This isn't to say the car won't drive within, whatever, 95% of it's capability, but... I've heard of some "findings" on these newer vehicles after "weird things" happen, you're attempting 10/10ths and your setup is very off from OE setup expectations. Just saying.

When I put the 305/30-19s on I will adjust the revs per mile for the speedo in HP Tuners, and have found that if I go with 790 my cruise control stops working. So I just do 785 and call it good enough. Stock, it was set to something like 745.