315 R6s on all four corners

[DGRacing]

@Grant 302 here is the deal

At a familiar track, only about a mile and a half long, the R7s were good for a full second over PZeros.
Set my new personal best by 1.01 second.
Also won my race class (ST2) on Saturday (started 4th overall finished third overall), took the overall race pole on Sunday out of 27 big/small bore cars (finished 5th overall after I ran out of fuel on the final lap, doh!), and set a new track record for NASA TT2 at this track by 1.5 seconds.

Took a while and some very skeptical tire pressure adjustments to make the R7s really work but I think I have a pretty good handle on them now.
And best of all, there were 6 people in my race and TT class each day so I was able to bank a whole set of Hoosiers for free in contingency for the weekend Not sure if I will order R7s or A7s yet.

I read on FB Tom was having a heck of time getting the R7's to hook, but it seems like a pressure thing. They seem to have much softer sidewalls and need even more pressure. What pressures did you end up using?

At a familiar track, only about a mile and a half long, the R7s were good for a full second over PZeros.

Don't forget to specify sticker R7's vs "pzero scrubs". My sticker PZero's were about 1.5 seconds faster (requiring 10psi less) than my sticker Hoosier R100's which were 1.5 seconds faster than sticker R6's. The R100's lasted less than the R6's and the pzeros are holding tread the longest so far. Just my exp.

 

[Black Boss]

@Grant 302 here is the deal

At a familiar track, only about a mile and a half long, the R7s were good for a full second over PZeros.
Set my new personal best by 1.01 second.
Also won my race class (ST2) on Saturday (started 4th overall finished third overall), took the overall race pole on Sunday out of 27 big/small bore cars (finished 5th overall after I ran out of fuel on the final lap, doh!), and set a new track record for NASA TT2 at this track by 1.5 seconds.

Took a while and some very skeptical tire pressure adjustments to make the R7s really work but I think I have a pretty good handle on them now.
And best of all, there were 6 people in my race and TT class each day so I was able to bank a whole set of Hoosiers for free in contingency for the weekend Not sure if I will order R7s or A7s yet.

Congratulations

Look forward to video.

 

[ArizonaBOSS]

I read on FB Tom was having a heck of time getting the R7's to hook, but it seems like a pressure thing. They seem to have much softer sidewalls and need even more pressure. What pressures did you end up using?

Don't forget to specify sticker R7's vs "pzero scrubs". My sticker PZero's were about 1.5 seconds faster (requiring 10psi less) than my sticker Hoosier R100's which were 1.5 seconds faster than sticker R6's. The R100's lasted less than the R6's and the pzeros are holding tread the longest so far. Just my exp.

Agreed. Sticker PZeros are going to trump everything (Yokohama slicks might be close/better)--but at $2500+ per set

For the R7s, you're going to want to run your cold pressures even higher than hot pressures on R6s. For TT and Qualifying I was going out from 33-35psi cold depending on tire position, and these would yield best lap times mid/late in the session (15 min session, would run 6-7 laps). I didn't get a good read on hot pressures due to cool-down lap and having to scale the car, but the one reading I was able to get said 44 hot front 42 hot rear--so I'm guessing they were probably another pound or two higher hot if I didn't run the cool-down or have to weigh-in.
For a 30+ min sprint race I think the pressures need to come down 1-1.5psi from there cold to make sure they don't go away towards the end of the session.

Now I know those cold pressures seem absurd; but they work.
I started out 29-27 cold and the car was skating all over the place. I figured going higher would only make it worse.
I tried running them low (24-25psi cold) like PZeros and they had grip, but the car would push quite a bit because you'd just roll the sidewall over.
I decided to try the higher pressures anyways for my first session the next day.
To my pleasant surprise, the higher pressures were better right out of the gate and the tires got much better as they got more heat into them.

I wish I had tried the higher pressures at Willow Springs last weekend; with the additional grip they probably would have been worth another second on top of the gains they already had.

 

[cloud9]

For the R7s, you're going to want to run your cold pressures even higher than hot pressures on R6s. For TT and Qualifying I was going out from 33-35psi cold depending on tire position, and these would yield best lap times mid/late in the session (15 min session, would run 6-7 laps). I didn't get a good read on hot pressures due to cool-down lap and having to scale the car, but the one reading I was able to get said 44 hot front 42 hot rear--so I'm guessing they were probably another pound or two higher hot if I didn't run the cool-down or have to weigh-in.

That's good info right there. That's a couple psi higher than I found as the sweet spot on the R6s. Your car is probably lighter than mine too so could need even a pound higher? My TT3 weight is 3715. Is the "Max pressure" still 44 on the R7 or did they increase it?

 

[ArizonaBOSS]

That's good info right there. That's a couple psi higher than I found as the sweet spot on the R6s. Your car is probably lighter than mine too so could need even a pound higher? My TT3 weight is 3715. Is the "Max pressure" still 44 on the R7 or did they increase it?

I don't know what they print on the sidewalls, but I've heard people I trust telling me that they've run up to 51 psi with Hoosier's trackside support.
YMMV for pressures, but at least now you have a starting point to work with.

My car scaled in at 3530 +/-20 lbs with me in it the past two weekends. Aiming to knock 80-100lbs off that in the next month or so.

 

[cloud9]

I don't know what they print on the sidewalls, but I've heard people I trust telling me that they've run up to 51 psi with Hoosier's trackside support.
YMMV for pressures, but at least now you have a starting point to work with.

My car scaled in at 3530 +/-20 lbs with me in it the past two weekends. Aiming to knock 80-100lbs off that in the next month or so.

You must be getting pretty close to 8:1 already. Will you have to detune if you knock 80-100 lbs off? I can't remember if you did LTHs but I assume at a minimum you're running an O/R mid-pipe.

 

[ArizonaBOSS]

You must be getting pretty close to 8:1 already. Will you have to detune if you knock 80-100 lbs off? I can't remember if you did LTHs but I assume at a minimum you're running an O/R mid-pipe.

I'm a bit over, right now. 410 hp at the tires and 3505ish weight, puts me at 8.5 raw ratio, then you get a credit for being so damned heavy so close to 8.8 final.

With latest setup sheet, I'll be at 3401 minimum weight (probably closer to 3420 actual) and can put down up to 436 whp (25hp cushion for wacky dynos). With 410hp at the tires, plus the lard-ass credit, I'll be around 8.2 adjusted; but the classing sheet is written for lowest weigh and max power "8.0".

Stock exhaust manifolds with off-road X!

 

[ArizonaBOSS]

BTW no rubbing front or rear w/ 315s and 10.5 +38 all around, after fender roll.

 

[cloud9]

I'm a bit over, right now. 410 hp at the tires and 3505ish weight, puts me at 8.5 raw ratio, then you get a credit for being so damned heavy so close to 8.8 final.

With latest setup sheet, I'll be at 3401 minimum weight (probably closer to 3420 actual) and can put down up to 436 whp (25hp cushion for wacky dynos). With 410hp at the tires, plus the lard-ass credit, I'll be around 8.2 adjusted; but the classing sheet is written for lowest weigh and max power "8.0".

Stock exhaust manifolds with off-road X!

Yea I forgot the full-figure bonus. The classing system is not Mustang friendly since a 2800 lb BMW at 8:1 or 9:1 is still at a huge braking and acceleration advantage.

 

[ArizonaBOSS]

One more benefit--I was able to mat the throttle in 2nd from a 30mph roll and the car will hook up. At least for starts. I don't know if I'd try that while cornering. Really helped me get a jump on my starts this weekend. Probably not useful for open track/TT. With other rubber, the car would just blow the tires off and I always started in 3rd.

 

[cloud9]

So after all the feedback and the test fit of the 315 on an 18 x 11 up front I have settled on the following. I ordered two sets of Forgestar F14 18 x 11 with the separate offsets for front and rear from Vorshlag. The stock of 12" material is out to midsummer so since I'll only be running these this year I went ahead with 18 x 11s all around. I am going to run R7s in 295/30 on the front and 315/30 on the rear. You can't rotate these wheels due to the different offsets for front and rear. I'm hoping the car will still be neutral with the staggered tire sizes front to back, but it could end up being a little tail happy. If so, I have an adjustable front FRPP sway bar, but I hate to give up grip by going to the stiffer setting (currently in the middle of 3 positions). The most logical step might be to try a smaller rear bar. The problem is I'm trying to get by for one more year since I'm switching to the GT350 next year and don't want to invest too much more in the Boss, otherwise I'd go with an all new suspension setup like Rick did.

 

[ArizonaBOSS]

Well, if nothing else, you will look good!

 

[Grant 302]

That sucks about the 12" blanks.

 

[JScheier]

I'll buy them from you when the GT350 comes in

 

[cloud9]

I'll buy them from you when the GT350 comes in

Works for me.

 

[cloud9]

Well, if nothing else, you will look good!

I still expect a performance increase going from a 9.5 to an 11" wheel up front. That 295 will have a larger contact patch. The same for the rear albeit not as much going from a 10.5 to 11" with the 315. I "may" end up deciding to roll the fenders and try to stuff the 315 up front, but am going to wait and see how that goes for John ;D

 

[ls110]

I still expect a performance increase going from a 9.5 to an 11" wheel up front. That 295 will have a larger contact patch. The same for the rear albeit not as much going from a 10.5 to 11" with the 315. I "may" end up deciding to roll the fenders and try to stuff the 315 up front, but am going to wait and see how that goes for John ;D

Just ordered a set of the 315 R7s to put on the front 11"ers. Also talked to a good body shop that has had experience with rolling the fender. Hopefully late next week I will have it completed.

 

[cp85gt]

Discount Tire Direct is running there $100 off a $400 purchase sale on Ebay now. Got a set of (4) 305 35 18 Nitto NT01's by ordering 2 sets of 2 for a $200 discount. CMOTORS315 is the discount code. Now to decide on wheels. 11" Forgestar's with no rotation or 10.5" Enkei's with rotation. Tough choice as the 305 Nitto's are definitely pinched a bit on the 10.5" wheels.

 

[VoodooBoss]

Discount Tire Direct is running there $100 off a $400 purchase sale on Ebay now. Got a set of (4) 305 35 18 Nitto NT01's by ordering 2 sets of 2 for a $200 discount. CMOTORS315 is the discount code. Now to decide on wheels. 11" Forgestar's with no rotation or 10.5" Enkei's with rotation. Tough choice as the 305 Nitto's are definitely pinched a bit on the 10.5" wheels.

Have you looked at the CorteX wheels?

http://www.cortexracing.com/shop/jongbloed_700/

 

[cp85gt]

I have looked at the Cortex wheels, both the Jongbloed and the Enkei +47. Both are 10.5" wide and require a decent sized spacer in front for a stock type strut that would require longer studs. Having the wheels poke out in back a bit is not that big a deal to me for a track set-up that would justify the extra cost of those wheels compared to the +38 Enkei's (about $450 if you shop around). The Forgestar's are $100 to $120 more per wheel when the Enkei's are on sale. I guess the decision would be that for an HPDE car with some non-competitive time trial use, is the utility of wheel rotation of greater benefit than the extra wheel width. It seems that several mustang owners who already have Enkei 10.5" wide rear wheels have opted for the wider Forgestar wheels rather than get some 10.5" wide Enkei's for the front for a square wheel set-up.