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?

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.

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)

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 run 15x8 and 16x7 both re71r and the end result is tire weight that's very very close

the 15x8 are faster or at least feel faster, I have never swapped mid event to see

I can't run 15x8's per class rules.

Unfortunately due to the strange autocross rules you are down 40hp, LSD and port installed jcw springs on my 2006 JCW

I run 16x7 with 205/45/16 re71r on my jcw, I have beat all but the local club president in DS, he too is in a jcw and is able to post top 5 raw times.

It's not strange rules. They have basically been the same, except the addition of rear sway bar in 2011 (before then, we removed front sway bars), port installed parts (something I haven't noticed until I owned a Mini), and the move to DS.

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

I think the rules are strange and unfair, the 05-06 has a huge advantage and it's the same model car, IMO they should allow the same mods to all R53's

crx SI are stupid fast in SMF, so are the new civic SI's we have a guy in a 2008 civic posting fastest raw times and he runs HS

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.

Update / backdate is SP, not ST.

A full tilt DSP build would be interesting on the right course. Basically build a GP2 clone on a non stability control chassis, unlimited boost, 275-15 front HoHos, and an OS Giken.

I've never raced ST, SP, or SM. That's why I said "I think". Only GS (87 CRX Si, Saab 900S), CP 81 Mustang), DP (96 Miata), and EP (87 Civic Si and 87 CRX Si)


I do know an LSD is legal in ST, so it's a moot point at that point.

In STX, yes. In STF, no.

Boost change makes you smf

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,

14.8 pounds, these are what I ran at Nationals this year. OZ.

My B38 Justa is in G Street.

All the best,

Charlie

you can only change offset by something like 7mm in DS

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.

my rpf1's were not that bad from tire rack

you could just run STX, you get to add camber and more wheel, tires last a lot longer my running costs are lower but I'm not sure that makes up for the cost of coilovers/camberplates

Boost changes are legal in SP for turbo cars.

15.10.b.4.f:

https://cimg5.ibsrv.net/gimg/www.nor...88d8ebd710.jpg

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.

I've been looking at the TR wheel -C1. 16x7. ET42. 15.2lb. $128/ea

sorry I'm in a r53, boost change makes you go SMF, any pulley change make you SMF in the r53

Ah yeah, I guess that makes sense. I miss my r53, I preferred it to my r56.

Is it spring yet? I'm ready to smash some cones.

R56 is faster, I was on the track all weekend and a 2011 with intake/catback/intercooler walked away from me every straight

I have a 17% pulley, intake, catback. I think I'm going with a track cam, 550cc, catless header and tune soon.

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