I'm looking to get a set of "street tires" to auto-x on in the Tire PAX class. Largely because street tires can be bought for less than a set of V710's or A6's.

Anyway, I'm planning to get a set of Bridgestone RE-01R tires, my only question is size: I'm torn between the 205/45ZR16 and 225/50VR16. The 205's are smaller diameter so better gearing (~7% smaller), but the 225's have 10.7% wider tread.

So, which size would you go with? Keep in mind the 205's are about $100 more for a set.

Edit: I've got an '04 MC in Stock class, so I'm not exactly pushing a lot of power here. Though I've always heard that more rubber is better.

 

i personally love the gearing you get with 205/45
but wide tires are also sweet (https://www.northamericanmotoring.co...ad.php?t=87381)
and his gearing ain't bad :-P

what about the dunlop direzza z1 in 205/50R16? they are cheaper and quite similar in performance
http://www.tirerack.com/tires/tires.jsp?tireMake=Dunlop&tireModel=Direzza+Sport+ Z1\

on first thought i think the 225/50 is a bit big on the dia... but i haven't down the math to compare it too stock yet...

just did the math, they ain't that much bigger than stock, but i think in autoX accel gearing is just as important as grip... so i don't know lol but i think the dunlops are worth a look

 

If using stock 15x5.5 rims then
195/50-15

If using stock 16x6.5 rims then
205/45-16

If using stock 17x7 rims then
205/45-17

So there is not much to think about since the tires you use will be fit on the rims as specified. It's different if you can choose any rim width, then you can make use of a wider tire.

For example if you weren't in stock class you can run the 225/50-16 on a 16x7.5" rim for better effect, otherwise you squeeze a wide tire on a narrow stock 16x6.5" rim, it's not the best fit although the tire itself is wider.

 

I haven't heard of that one until now. After some reading it seems pretty impressive. So, anyone know of any other tires I should consider to further confuse me?

 

Not sure if you can source them yet as they were just released in Japan on the 1st of March.

The Potenza RE-11, supposed to replace the RE-01R.

 

I just bought the Dunlops in a 215/40/17. My first autox using them will be this weekend. So far I would have to say that turn in is much more predictible than the Bridgestone RE01's. The ride is definitly rougher going down the freeway though. I haven't really tried to reach the total grip factor yet, that will come this weekend.

I have also had the Falken Azenis RT615 which isn't a bad tire it just gets way to hot to quick. The Dunlops take quite a bit of abuse before they get to hot. I have an 04 MCS with no LSD so I can experience quite a bit of tire spin and the Dunlops seem to be OK with that.

 

RE-11 replaces Bridgestone Potenza RE-01R as of March 2008 in Japan, US can get the RE-11 in about one year, no promises. Import from Japan if you can.

Any tire size that gives smaller than stock tire diameter will offer some gearing advantage to any MINI with taller gears like the 2002-2004 MCS 6 speed but the 2005 and later MCS got shorter gears so it's not that bad or crucial. I run tires that are 22.9" tall compared to 24.3" stock height. My street tires are 24.7".

Dunlop Direzza Z1 is a good Extreme performance Summer tire. Especially for wet handling but it's not as comfortable for daily street driving. It may last a little longer and costs less depending on the tire size you need.

 

The tires are going to go on a dedicated set of rota slipstreams's that will only be put on for events, so I'm not too concerned with their street mannerisms. I can't really seem to find an answer to this: do the Dunlop's need to be shaved? I know it's always suggested to shave tires, but some need it so they don't chunk up in auto-x; is the Z1 one of these? If so, what depth should it go to?

 

For track use, shaving tread down to about 6/32nd inch helps to improve performance and reduce risk of chunking.

For autocross use usually you don't get the same heat built up so unless your course times run over one minute I would say it's likely you don't have to shave any street tire unless used for track AND autucross.

I run street tires new for autocross and they do fine for me. Run time is 30 to 40 seconds, hardly builds up much heat.

One other concern is with stock front camber you aren't using the full tire tread, mostly the front tire outer edge when cornering hard so if you have a pyrometer check that part of the tire to monitor for heat. I have -2.5 degrees negative front camber so temperatures tend to be quite even for the front tires.

 

Thanks for the note on the shaving - before this all I've ran in auto-x was r-comps on a Miata where I could adjust just about any alignment setting I wanted. Which reminds me...
That reminds me of another question I thought of yesterday - I know in a car where you can adjust camber you want to try to get uniform temp's across the tire, so you adjust camber and pressures accordingly. What about in a car that can't adjust camber (like a stock class MINI)? Do I just adjust pressure so that the middle and outer are the same or so the middle is equal to the average of the outer and inner temps?

 

In the older 2002-2004 MINIs you cannot adjust front or rear camber without adding adjustable or fixed front camber plates and lower adjustable control arms. In the 2005 MINIs and later you can adjust the rear lower shock a little for some negative camber and in the newest R56 you can adjust a little in the front for more negative camber.

Assuming you have a MINI that cannot be adjusted you can change toe settings for front and rear but not camber when you do alignment for track or autocross. More toe out in front helps with turn in steering response up to a point, then the steering can become twitchy- usually past 1/4" toe out.

Since you cannot change camber you do change tire pressures but you won't be able to make the tire temperatures as even across the tread surface especially in front. I usually look for about 2-3 degrees difference from inner to outer edges but with not enough negative camber you can be 10+ degrees different.

If tire pressure is too high you will see the middle of the tread having the highest temperature. Usually when you corner hard you will see the outer edge temperature go up. Usually you can look for a good pressure that gives you similar temperatures for outer and middle treads, inner thread will always be lower until you run a pressure that is too low.

You can also chalk your tires to check for how much they roll over and keep that under control, use the tread you have but don't go too low and rollover too far.

 

Anyone know if the 225/50R16s have any clearance problems on a stock R56? I was thinking about going that route when I eventually move over to slicks. The car is fine down low and I feel that it is already too easy to top out 2nd with the stock diameter, so I rather not jump down to a smaller diameter.

 

I am currently using the 225/50-16 'Stones RE-01's on Rota stock size wheels (16x6.5). There are no clearance issues with my stock R56 MCS in mixed autocross and daily driver use. FYI, If I had it to do over again I think I would go with the 225/45-17 size. I got spanked at my last event by a guy using the 17 inch setup, and it looks to better than the pinched tires on 6.5 wide wheels.

 

shorter OD isn't always a benefit. if you run out of rpm and have to shift vs. a taller tire where you could stay in gear, you won't be faster. it depends on the course and how it matches up with your gearing.

 

Thanks, yeah I was thinking the rotas and kuhmo slicks, because kuhmos suggested width range included the 6.5. The 17 setup is interesting but I assume there is no way around that being heavier and more expensive too. Something I guess ill look at more.

 

Weight and cost were the big issues when I was deciding what to buy and the 16 inch setup is substantially less expensive. The 225/50-16 RE-01's weigh in at 27 pounds each on my scale (listed at 26 pounds on the website below) and the Rota slipstreams weigh 13.0 pounds. I never checked the weight of the tires before buying them and never expected they would be so heavy. The 225/45-17 RE-01's weigh less at 25 (according to the website). So I don't know how much heavier the 17 setup is versus the 16, and to what degree the rotating inertia is increased? Also; is the wider wheel available with the 17s utilizing the tire width more effectively/efficiently? Will they wear better? Since most of the cornering in a camber challenged stock MINI comes from the outside shoulder it seems that that a wider tire might not be providing any additional contact patch at maximum cornering, but what about during acceleration? I had no idea I had so many questions until I started this reply!!!

http://www.bridgestonetire.com/tires...roduct_ID=1111

Sorry if I muddied the water. Thank goodness I'm in a stock class, because if I was in a class that allowed a lot of adjustment it might drive me crazy.

 

We have the Bridgestone Re01R's in the 205's priced $28 more for the set than the 225's.

Leo Barrios
leo@edgeracing.com
800-489-5353 x211
http://www.edgeracing.com

 

At 28 lbs., those are some seriously heavy tires.

You should be able to get tires in the 21-22 lb. range, and six extra lbs./corner is not a good thing. My combo weighs 29.5 lbs. for wheel and tire combined...

 

light tires won't matter if the tire sucks. I had 15" BBS RG-F with 205/55/15 Ecsta SPT. Ya, it sucked and I ditched them forthwith. Sure, they were light, but there was NO steering response whatsoever. Steering response requires a stiff sidewall and that means weight. The best tires for steering response are generally heavy.

 

this is definitely true, i am speaking from experience on a r50, dunno how different the gears are on an S. i can to ~64mph in 2nd if i poke the fuel cut and only have come across one cross where i shifted to 3rd (for a tiny bit) where does the S get to in 2nd?

 

I just went to wikipedia to their definition of autocross and there is a mini picture on it. Cool!

who is that?

http://en.wikipedia.org/wiki/Autocross


Same picture on the SCCA web site.

 

Yeah hard to say how affectively the car can actually use the 225s. I think it could use the tire getting out of the corners. With the torque on the R56 even after I straighten out its hard to put the throttle down all the way on my current summer tires. The RE01Rs are pretty heavy but supposed to be really good in the street tire classes. Weight does seem a bit crazy to me, but they better have a super stiff sidewall. Most of all I would want to avoid shrinking down the OD cause i like my gearing.

 

keep in mind a 215 width RE01R is wider than most 225's. Heck....maybe more like a 235 width.

 

Thanks acender, that's good to know.
I'm thinking of getting 225/50R16 Hoosier A6 for autox, since I have a spare set of 16's, but that is the first confirmation I've heard that that size will fit. My rims are 16x7 though, so the tires might be a tad wider than on your 6.5". How much leeway to you figure there is?

Sorry, in answer to the original question: go with width. traction rules in autocross +you're saving $100.

 

Hey Mike,

so how did the auto-X go on the Dunlops ? Do you think they are better for auto-X than the Falken RT615 ?

Rennsemmel