I've read elsewhere where the bigger wheels, wider tires are the Performance option of choice. In other words, for performance go bigger. However, with MINI most people seem to want to get the lightest wheel even it means 16 (or 15") vice 17 or 18.

The advice seems contrary. JCW offers 18" wheels only, why not a lighter 17"?

Others have told me that the real question is not lighter unsprung weight, but rather the trade-off of the lighter weight versus the bigger contact patch and better traction gained by the bigger wheels/tires. Better traction offsets the lighter wheels.

Dunno how you measure that. So what do you all think?

 

I think that when it comes to some things, like the wheels, leather dash etc, JCW is just putting out some things to make some money. I personally do not think their wheels do anything to really help the performance and that its just about looks/branding (and they went with the 18s as an appearance preference).

Edit: Also there is no 18" OEM wheel that competes with them, right? So they are offering a wheel option that augments the Mini wheel lineup without competing against something they offer.

 

Nevermind - I'm not an expert

 

Actually, I was using them only as an example. What do they run in the JCW challenge series? 18". There has to be a reason and I dont think its market. There is a tradeoff between traction vice weight ... I am trying to understand it.

 

larger size=looks, and somewhat more handling feel as because you are closer to the road... but the performance gains pretty much stop there (ill let the expert go there... i rather not tread that deep into it).. but essentially... larger size wheels get you better steering feedback

smaller wheels are smaller, lighter, but come on..... does anyone really really like small wheels? (well, im sure there's alot) but not everyone who buys MINI is going for performance... some just want looks... i for one, run my 17s on the road just because it fills out the gap in the fender much better... also, less rubber... although in my case is wont make a difference, still, i like my 17s because it looks just right.... i even thought of running 18s for awhile... but i didnt...

in the end.... smaller wheel and smaller tire equates better acceleration, because the wheel itself is smaller, and the engine power transferred therefore has less force to overcome from the resistance of the wheel (if that made any sense!) but also, you pay the price with speed by going smaller wheel (in my case, i run 215/40-16 on the track.... needless to say i gain alot of acceleration because the wheel spins one cycle faster than if i was running my street 215/45-17s, but as a result.. gearing is affeced...

now that i just blurted out a huge chunk of garbage..... ill leave the explanation to the experts

i know the JCW challenge Coopers run 15s

 

Let me throw my uninformed opinion in here:

Depends on what you are doing. Short track, AutoX: smaller wheel. Long track, DS: larger wheel. A little something else to add to the mix. I went from 16 inch oem with runflats to 17 inch aftermarket with Yokos. End result was a smaller diameter and lighter weight wheel/tire combo.

Hope this didn't help you any.

 

OK, I understand the acceleration part but I guess I should have put this in perspective. The question was more about "performance" basically around a large track. The theory being the larger contact patch means more traction and thus around the corners faster. Acceleration isnt going to mean much if it comprimises top speed in the straights?

I had read one comment from a professional driver that if he 19" wheels on a Porsche he was testing, he would have gotten around the Ring faster by so many seconds vice 18" wheels.

Make sense? or not?

 

But isn't it different on a rear wheel drive car since you can stagger the wheel and tire size for a better result then on a front wheel drive car?

 

Dunno. However the stagger you mention is not between wheel size but rather tire size. For example, the rears might be 265s while the fronts are 235. But, the wheel size itself is still 18 or 19".

 

Well, actually you can have bigger diameter wheels on the rear vs front (like the Crossfire) but actually I was referring to wheel width. I had wider wheels, and tires, on the rear of the E46 and also have that on the M Coupe.

 

yes, the rears are wider wheels.

 

it's actually quite simple...

the reason for using larger diameter wheels is to accomondate larger
brake rotors. it comes with a side effect of making initial turn-in response
quicker due to the shorter tire sidewall.

on my MCS, the brake rotors are stock and tiny. brake capacity sucks.
the handling is imho too nimble especially on expressways... so went
backwards from 17" to 16" to get the added benefit of making the
wheels lighter, matching the wheels size to the brake rotor and to
slow down the initial turn-in response for a better straightline stability.
i even chose the GS-D3's instead of the stiff sidewall S03's to make
it even softer.

 

You don't get any more traction from a larger wheel unless you use a wider tire (which you could also do on a smaller wheel). Large wheels are for fitting larger brakes, or for glass-smooth GP tracks, and where you have power to throw away.

You will get a noticable loss of acceleration, worse braking, a harder ride, and a major loss of cornering traction when you use a heavier wheel, regardless of the size. Unsprung weight and low sidewalls are the culprits, as both keep the tire from staying in contact with the road over irregularities. These are not subtle effects - lighter, smaller wheels make the MINI ride and handle like a Porsche instead of a truck.

Mini tire size is limited to a 205 or 215 width (depends on the tire), and a 7-1/2" wheel, unless you want to start whacking away at the fender liner and use hub spacers, both of which are foolish ideas for a street-driven car, IMHO.

You can fit a 205 or 215 (good luck finding 215 widths) tire on a 15x7" wheel as easily as on a 18x7" wheel, and you can get a variety of high-performance tires in 15" sizes (not as many options as a 16" size, but lower priced in 15" for the same tire, and lots less costly than 17 or 18" sizes).

The effective final drive ratio is determined by the tire sidewall in addition to the wheel size, and you can go up or down a few percent by changing the sidewall by 5, i.e. 55-section sidewall instead of 50-section is about a 3% difference.

Personally, I think that "filling the wheel-well" with wheel instead of tire makes the Mini look like a child's HotWheels toy, but opinions vary.

 

alright.... in essence.... you are right, and ken's got it hit in the head as well.... larger brake rotors require larger wheels.... always (well, some exceptions, but most bbks on the market require 17' wheels)

wider contact patch does somewhat equate more grip.... but there's alot more factors at play too....

i was contimplating running 16x8 wheels up front and 16x6.5 wheels in the rear in my race tire setup before i settled on all 16x7... the staggered wheel fitment would stiffen up the sidewall on the front and soften up the rear, making it turn in better, but trade off is inability to rotate them forward backward...

i use the acceleration vs. top speed here once more... acceleration is much more important in an autox where top speed will never be reached and often times people stay in the first 3 gears.... as for top speed i guess ill find out when my track day come in about a week

okay, so overall.... running small wheels dont always equate you cant run equally wide tires

 

When I look at performance for the MINIs I first look at what I will use the MINI for that requires performance and what tire meets my requirements, then I choose a light and strong rim that best fits that tire.

So I choose the tire, then I choose the size that will fit a MINI, then I optimize the rim size to fit the tire. Many owners do nearly the opposite going for rim first then picking a tire to fit but unless you go with a very popular tire some don't come in a size that will fit your MINI in a given rim size.

Only certain sized tires fit the MINI and the selection of rims is reduced with any sort of performance suspension upgrade (coilovers or springs).

The biggest benefit of larger diameter wheels would be that they can fit really wide tires. This best suits cars that have more power than the MINI has and a larger wheel well to fit the wider tires. MINIs could fit 225mm wide tires but don't do well with sizes beyond that. 205 (suited for 45 and 50, and 55 series sidewalls) is a good fit as is 215mm tires (suited for 35, 40 and 45 series sidewalls),

Larger wheels are likely going to be heavier and could be more expensive. Light wheels in 18" and 19" that are strong are going to be much more expensive-however often they offer a greater selection of widths that match wider tires. Big brake kits will fit larger rims as mentioned but Willwood and others do make larger than stock brakes that will fit 15x7" rims.

Are there people that like their 15" rims for performance? Sure, mostly those lesser powered import owners with lighter cars and limited budgets. They can do just as well or better on the track as any other car provided the track isn't too long and stretched out to help those cars with high power but it that is the case then no tire and wheel combo is going to help the MINI enough- better get a turbo kit.

MINI and JCW don't really make performance wheels. All are too heavy to be effectively raced on. They are made with looks and cost in mind. Your best performance rims are not always going to look that good by comparison. And the best performance wheels can be limited to certain sizes. 15x7 is about as wide as rims come that are easy to find. For an 8" wide rim you have to look at 17 or 18" diameter rims.

Try talking to Alex@tirerack to learn more about tires and rim options, there are alot of ways to approach better performance. It usually starts with removing the stock runflats.

 

I am not an expert either but i saw a mini race car, i dunno if it was a challenge car, at the mini booth at the detriot autoshow it was running 205/50R15 on what looked like enkei rpf1

i will see if i can dig out those pics and tell if it is a challenge car or not

 

Apparantly what I was refering to is a comment by Walter Roehlr, who I believe is the Porsche Factory driver commenting on speed around the Ring in relation to a Cayman. I dont have the exact quote but it was something like to get the ultimate perforance, you need the 19" wheels. But the 18" wheels would be better for everyday street driving. It may have been from the book Excellence.

Other comments were something about the 19" wheels gave a bigger contact patch means more traction, better braking, etc.

 

Not necessarily intuitive, but the size in square inches of the tire/road contact patch is determined solely by the tire pressure, the weight on the tire, and the tread pattern.

Divide weight by lbs./sq.in. and get the contact patch. Higher air pressure = smaller contact area.

The Shape of the contact patch is determined by the width and outside diameter - a larger outside diameter tire size slows acceleration because of the higher effective gear ratio, but can create a longer, narrower rectangle of contact patch, which can aid braking at the expense of cornering traction.

A larger outside diameter can sometimes increase top speed if a car runs up against the rev limiter, but is highly unlikely to do so on a MINI, as its limiting factor is aerodynamics, not the engine RPM.

In some cars a smaller-diameter tire will increase top speed, by giving the engine a lower overall gear ratio to work against air resistance. It depends on the torque peak of the engine - if the gear ratio is not well chosen, the car hits top speed at other than its most powerful RPM.

 

In the early MCS, wasn't the car's top speed found in 5th gear instead of 6th?