Solo 15x6.5's vs 16x7's
#1
15x6.5's vs 16x7's
New to autocrossing Mini's. Looks like I have what I call an "oddball car". With a 2004 MCS, I can't do an LSD(05+) or JCW Sport Suspension (07+) in DS. So my car is what it is.
With autocrossing Miata's and Honda's, and with Pro3, Spec Miata, and ChumpCar Miata, I'm used to 15" wheels. BFG G-Force Rival S is what I'm used to in ChumpCar, and Toyo RS3 for everything else road racing wise.
I can find 15x6.5 wheels around 11lbs new. The lightest 16x7 wheel is roughly 16lbs (the SSR's appear to be discontinued).
Would it be worth going to 15" wheels to loose a total of 5 lbs each wheel, or is gearing to be too far off to even make a difference?
With autocrossing Miata's and Honda's, and with Pro3, Spec Miata, and ChumpCar Miata, I'm used to 15" wheels. BFG G-Force Rival S is what I'm used to in ChumpCar, and Toyo RS3 for everything else road racing wise.
I can find 15x6.5 wheels around 11lbs new. The lightest 16x7 wheel is roughly 16lbs (the SSR's appear to be discontinued).
Would it be worth going to 15" wheels to loose a total of 5 lbs each wheel, or is gearing to be too far off to even make a difference?
#2
I went from a 16x6.5 (205/55, a little tall) to a 15x7 (205/50) and it woke the car up incredibly. The 2004 has a longer 1st/2nd then the 05+, so the reduction of top speed in second is no problem. The chart below shows ratio to do the calc. I want to say the quick math says I lost 3 mph at the top end.
MINI Cooper S
Builds thru 06/2004:
| 1 | 11.425
| 2 | 7.181
| 3 | 5.397
| 4 | 4.407
| 5 | 3.656
| 6 | 2.986
You can use this formula to get max speed
R * 60 * 3.14159 * (W * P / 100 * 2 / 25.4 + D) / 12 / 5280 / G
R = RPM of engine [4750 Diesel - 6750 all other models]
W = Width of tire
P = Profile (aspect ratio) of tire
D = Diameter of wheel
G = Gear Ratio
Oh, and I went with the Rival S as well for the 15's. Coming from Hankook RS3's, they seem to have another level of grip.
MINI Cooper S
Builds thru 06/2004:
| 1 | 11.425
| 2 | 7.181
| 3 | 5.397
| 4 | 4.407
| 5 | 3.656
| 6 | 2.986
You can use this formula to get max speed
R * 60 * 3.14159 * (W * P / 100 * 2 / 25.4 + D) / 12 / 5280 / G
R = RPM of engine [4750 Diesel - 6750 all other models]
W = Width of tire
P = Profile (aspect ratio) of tire
D = Diameter of wheel
G = Gear Ratio
Oh, and I went with the Rival S as well for the 15's. Coming from Hankook RS3's, they seem to have another level of grip.
#3
Diameter/weight of Bridgestone RE-71r:
205/50-15 23.1" 21lbs.
205/45/16 23.2" 19lbs.
OEM 195/55-16 24.4" 22lbs.
Wider wheel good for handling
shorter tire sidewall good for handling
heavier wheel/tire bad for acceleration
shorter tire diameter good for acceleration (if you can get the power down)
205/50-15 23.1" 21lbs.
205/45/16 23.2" 19lbs.
OEM 195/55-16 24.4" 22lbs.
Wider wheel good for handling
shorter tire sidewall good for handling
heavier wheel/tire bad for acceleration
shorter tire diameter good for acceleration (if you can get the power down)
Last edited by hsautocrosser; 07-05-2016 at 08:39 AM.
#4
Ok, an update.
I'm looking at one of two wheels. I was going to go with Konig Helium at $80/wheel, but the offset was too much by 1mm. The option would be to mill them 1mm to bring the offset within spec. The other option is Rota Circuit 10's. A little heavier, and a little more expensive at $120/wheel The 11 lbs wheels are RPF1's. Gotta pay to play.
I'm not SRS BNS any more. With more time spent officiating SCCA and NASA club races and pit crewing for a Trans Am TA1 car, my plate is full. I did a total of 4 autocrosses this year.
I'm looking at one of two wheels. I was going to go with Konig Helium at $80/wheel, but the offset was too much by 1mm. The option would be to mill them 1mm to bring the offset within spec. The other option is Rota Circuit 10's. A little heavier, and a little more expensive at $120/wheel The 11 lbs wheels are RPF1's. Gotta pay to play.
I'm not SRS BNS any more. With more time spent officiating SCCA and NASA club races and pit crewing for a Trans Am TA1 car, my plate is full. I did a total of 4 autocrosses this year.
Last edited by Gustav129; 11-27-2016 at 06:45 PM.
#5
#6
#7
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#8
I used to keep up with many Cooper S's in an 87 CRX Si in GS. No front sway bar, 13x5" wheels, 10 year old Yoko AO48's. 175/60r13
#9
#10
You are probably thinking of an 88+ Honda CRX Si. That's the only one the tuners acknowledge. Mine was older. Completely different suspension (torsion bars in the front and straight axle in the rear). Completely different engine, only 90 hp.
The update/backdate is available in ST I think. I prefer stock honestly.
The update/backdate is available in ST I think. I prefer stock honestly.
#11
#12
I do know an LSD is legal in ST, so it's a moot point at that point.
#14
#15
My Cooper S doesn't go into STF.
All Cooper S and S JCW are automatically in STX. Only the Justa 2000-2013 Qualify for STF. I'm assuming all older Justa's fall under NOC of STS.
If anything, my question about wheels was answered by Chili_Head. I'm just having a hard time finding wheels with the right offset, no matter what diameter size I go with. I found a set of Rota's that will work,
All Cooper S and S JCW are automatically in STX. Only the Justa 2000-2013 Qualify for STF. I'm assuming all older Justa's fall under NOC of STS.
If anything, my question about wheels was answered by Chili_Head. I'm just having a hard time finding wheels with the right offset, no matter what diameter size I go with. I found a set of Rota's that will work,
#18
I know.
Most of the popular light weight wheels of any diameter has an offset of ET40. This is the point where having them milled 1mm is an option.
There are a couple ET45's out there, but I'm not to thrilled about them. I'm not so serious with autocross anymore to justify spending $1000 on RPF1's. Over 10 years ago, that would be a different story. The cheapest and lightest being the Rota Circuit 10.
Most of the popular light weight wheels of any diameter has an offset of ET40. This is the point where having them milled 1mm is an option.
There are a couple ET45's out there, but I'm not to thrilled about them. I'm not so serious with autocross anymore to justify spending $1000 on RPF1's. Over 10 years ago, that would be a different story. The cheapest and lightest being the Rota Circuit 10.
#19
#20
Boost changes are legal in SP for turbo cars.
15.10.b.4.f:
It was changed within the last two or three years.
For wheels I run the Kosei K1TS. 17x7ET42, so within the legal range compared to the OE size of 17x7ET48. About the same weight as an RPF-1 (15lb vs 14.6lb) but a little cheaper.
EDIT:
If you want a 16x7 ET42 TR lists the Enkei J10 at $116/ea and 16.6lb which isn't too bad.
15.10.b.4.f:
It was changed within the last two or three years.
For wheels I run the Kosei K1TS. 17x7ET42, so within the legal range compared to the OE size of 17x7ET48. About the same weight as an RPF-1 (15lb vs 14.6lb) but a little cheaper.
EDIT:
If you want a 16x7 ET42 TR lists the Enkei J10 at $116/ea and 16.6lb which isn't too bad.
Last edited by Burglar; 12-01-2016 at 11:59 AM. Reason: Added 16" option
#22
Boost changes are legal in SP for turbo cars.
15.10.b.4.f:
It was changed within the last two or three years.
For wheels I run the Kosei K1TS. 17x7ET42, so within the legal range compared to the OE size of 17x7ET48. About the same weight as an RPF-1 (15lb vs 14.6lb) but a little cheaper.
EDIT:
If you want a 16x7 ET42 TR lists the Enkei J10 at $116/ea and 16.6lb which isn't too bad.
15.10.b.4.f:
It was changed within the last two or three years.
For wheels I run the Kosei K1TS. 17x7ET42, so within the legal range compared to the OE size of 17x7ET48. About the same weight as an RPF-1 (15lb vs 14.6lb) but a little cheaper.
EDIT:
If you want a 16x7 ET42 TR lists the Enkei J10 at $116/ea and 16.6lb which isn't too bad.
#24
#25
I've been running 16x7s on my HS mini for the last 3 years. on street tires, nothing beats added width to the wheel. never tried 15x6.5, but I went from 245s on a 17x8 to 255s on a 17x9.5 and it completely woke the car up. obviously that is a huge leap in wheel width, but still - street tires need that wheel width
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