All,

I know big wheels look great on the MINI, but is bigger better when it comes to Autocrossing ? Certainly for higher speed track work, where you need the additional space for a bigger break kit, a bigger wheel works great. But I'm not sure this makes sense for auto-x

Any insights would be most appreciated.

BB

 

I think it depends on which class you're talking about.

The majority of the fast stock class Mini's run on 16's. I think this is a function of 2 thinks: the HS legal 15" wheel is only 5.5" wide, and the GS legal 17" wheel is only 7" wide, which apparently isn't "wider enough" to make up for the extra weight compared to the 16 (that, and there may not be good sizes available in the good tires).

I think that in classes where you're allowed to run non-stock wheel sizes, the fastest diameter is actually a function of tire availability, rather than anything else.

My 2 cents at least.

 

Agreed!

I've been running 15's for a long time now, with 225/50R15's... I'm going up to 16's for next season, though, in order to clear a Wilwood 11.75 kit, with 225/45R16 rubber. Our AX courses are really, REALLY big and the Wilwoods will be a great asset.

So, it all depends on what you want... I do know that it's prety hard to stuff more than a 225 under the fenders. A 235/40R17 is possible, but it takes the right offset, the right width and trimming to make it work...

 

Thanks for the reply, I'm confused by your last statement.

"fastest diameter is actually a function of tire availability, rather than anything else"

I have some mods (pulley specifically) which put me in street modified class, so I guess you're saying that whatever I can afford and buy will be the fastest wheel ???

BB

 

In my original post, I was referring more to wheel diameter, and not so much on width. So, to be more precise, my decision is, do I buy a 16" or 17" race wheel for Auto-X ???

BB

 

I'd probably buy some sweet 15x8's or 15x9's, and go with a 225/45/15 Hoosier A6
http://www.tirerack.com/tires/Sizes....osier&model=A6

If it'd fit a 245/45/16 might also work, although the sidewall might be a bit tall (I'll let someone else do that calculation).

Edit, and what I meant is, there are a limited number of tire sizes available for purchase. Pick the size tire that you think will be fastest, and whatever diameter it happens to be, is probably the fastest sized wheel. For a Mini, my guess is that 15 or 16 inch wheels are best. But it's just a guess.

 

As a general rule of thumb, smaller wheels will weigh less and put the car's RPMs at a higher point (if yr running low profile tires (speedo readings are pretty irrelevant for autox)), both good things.

Unless you've got a large brake kit or running stock class, I don't see a reason for running anything larger than a 15", if you've got the money to burn on dedicated autox wheels.

*waits for someone to disagree with him*

 

JMHO, for SM, I'd be running 15's with a Wilwood 11.75" BBK up front and 225/somethingR15 r-comps...

 

how much would an 18 " tire affect your auto x time??

 

Based on my experience, the stickiness of the rubber makes a bigger difference than the size and weight of the tire/wheel combo...

BUT, that being said, on our cars the smaller O.D. you have, the better the gearing advantage and faster the times will be... And, the less weight, the better. 15's really squirt you out of AX corners QUICK!

IIRC from some testing, some back-to-back runs of 15's vs. 17's with the same Falkens Azenis, albeit different O.D.'s, proved the 15's to be quicker by 0.3-0.4 seconds. Statistically significant AND could make all the difference between 1st and 3rd place (if you're wanting to be competitive).

However, I'd go AX'ing on any size wheel/tire combo just to do it!

 

Sounds like the concensus is 15" wheels. The logic sounds good to me. I guess I just have to decide whether the lower weight and gearing offset the reduced contact patch.

BB

 

The Racing and Competiton sub-forums have lots of useful info on auto-x wheels and tires.
https://www.northamericanmotoring.co...isplay.php?f=7

See threads in STS and STX and SM forums.

 

\

225/45/15 works awesome - yes its short, but short enough to get on w/o mods! Not a street size.

Alex

 

I'll make it short and simple.

If you plan to stay stock, get 16 X 6.5 wheels. You'll notice improved acceleration and you won't loose that much grip by going down .5

If you plan on anything outside stock (i'll be doing this in 2008), I would get 15X7 or 15X8. Preferably 15x8 due to more grip. Obviously your biggest gain beyond that is choosing the right tire.

Good luck.

 

thanks tex