I don't think any thing was said about narrower tires being better for handling (unless we are taking wet / snow conditions) ?

A 205/50/15 has virtually the same contact patch as a 205/45/17 (they are the same width). In nearly all cases the 15 inch tire will be considerably lighter which will improve handling by reducing un-sprung weight -- The 15 inch will also have "gearing" advantage of about 4.7%.

If you compare a 225/45/15 to the 205/45/17, the 15 inch will wider and have a larger contact patch (it is wider) and a 5.7% gearing advantage.
The 225/45/15 compared to a 215/45/17 would be equal in width, but will be much heavier and the gearing advantage to the 15 goes up to 6.8%.

 

I think the reference to gearing is irrelevant because you can choose a different sidewall profile to equate the overall diameter and effective gearing between different wheel sizes. Replace the 215/45/17 in your last example with a 215/35/17 and the gearing would be just about equal, slightly in favor of the 17. And there's only one non-track tire available on tire rack in 225/45/15 and it only carries a 140 treadwear rating, so not really a viable choice for most people.

Also, regarding weigh advantage, that's coming from the wheels, not the tires (again using tires of equal overall diameter). If you think about it, the outer tread would be exactly the same, with the sidewall actually shorter on the 17, so less total rubber. The increased weight is coming from the larger wheel, and I agree is a disadvantage. I have an 09 JCW, so I am forced to go with 17s to clear the brake calipers. When I purchased wheels, I went with a Kosei K1-TS at 15 lbs. A lightweight 15" wheel is going to be around 13 lbs, so the difference is not a great as it's made out to be.

 

Tires can have a lot of difference in their weights as well. For example, a 215/45 17 tire can weigh 20 lbs to 26 lbs depending on the tire and brand. Of course going to a smaller tire, such as 205/50 16 will save you more weight but still there is a range of weights in that size as well.

I thought 225/45 17 is a very popular size with lots of choices?

 

Forgot to mention, not all tires of the same size have the same diameter. for example the diameter of a 225/45 17 tire is roughly 25" in diameter but some at 24.9" and others 24.8" in diameter.

For example, in that size, 225/45 17:
Bridgestone RE11 is 25" diameter and Bridgestone RE070 is 24.9" diameter. I think Hoosiers and BFG R1 run small at 24.8"

And I just checked tirerack.com, there are 162 choices in the 225/45 17 size and only 13 of them are track tires and 14 of them snows.

 

Sorry, that was a typo, I'll correct it to 225/45/15 which is what was mentioned in the thread I was responding to. In comparing tire weights, I think it's only fair to compare same vs same (brand, model, diameter) to compare a 15 vs a 17

 

I spoke of gearing because the original question was how to "improve" and the smaller diameter wheel / tire combination has this advantage.

And remember the OP has a "just a cooper" and gearing matters a lot on this car.

It is very difficult to match the 225//45/15 diameter with a 17 inch -- a small sidewall 225/35/17 is still 3.7% larger and you would have a rock hard ride.

Same brand tire comparisons generally show about a 3lb difference in tire weights with the 17 being heavier.

Same brand wheel comparisons show a similar weight difference.

 

If your objective is to lower the unsprung weight on the car, it is possible to do it with a lower weight wheel and a lower weight tire. Why not use both when you have a chance?

 

I believe his question was how to improve given that he already has installed 17x7 - 205/45r/17

Agreed, although the 225/45/15 appears to be an oddball size that is an inch smaller (5.2%) in diameter than the smallest tire that comes stock on a MINI.

Can you provide an example of this, I checked a few tires and see 0-1lb differences on the Dunlop Direzza DZ101, Yokohama S.Drive and Kumho Solus KH16; and Bridgetone G019 Grids are actually a couple lbs heavier in 15 vs 17.

Agreed, the wheel is where the difference in weight is.

 

Unsprung weight is one thing and if that is the only goal, then by all means use both. However I believe overall handling is much more complex than any one factor such as unsprung weight, and finding the ideal balance of multiple factors is what we're all after. I'm just trying to make the point that 17s in and of themselves don't mean you end up with massive unsprung weight and a poor handling car. I think good choices can be made across a range of wheel and tire sizes. And I think unless we spend most of our time on a track, looks are a factor for most of us and wheels are a great opportunity to enhance the looks of our vehicle (with many preferring a larger wheel & lower profile tire).

 

My 205/45/17 Dunlop Sport Runfalts were 22 lbs each.

My Michelin 215/45/17 Exalta PE2 Non-Runflats are 22 lbs each

When I change tires I wanted a little wider but did not want extra weight.

Now all I need is a nice set of "OZ" wheels @ 14lbs each in place od my 22 lb. Challenger wheels and I will be a Happy guy.

 

+1 I agree whole heartily -- If handling is your goal what ever size used, weight and diameter should be considered. On a really fast MINI big brakes become a important issue and with a "just a cooper" I think the gearing is very important.

 

215/35-17 Eek!

I have 225/35-18 on a 18x7 wheel and its hard enough cannot imagine a 215/35 with less tread section width and slightly less sidewall. EEK Again!

You cannot choose a 215/35-17 simply for better gearing, you have to take into consideration that some folks live in potholed cities, or simply like a little more ride comfort that a 215/40-17 would provide, even that many think is still to small of sidewall and prefer 215/45-17, especially if they live in wartorn streets. "The Right Wheel Set-Up" is a compromise of wheelweight, size, offset, tire size, compound, mileage(? ?) diameter, etc. The 205/50-15 on a 15x7 is a good set-up for most occasions including performance oriented driver.

 

That was exactly my point - if you need gearing you better go smaller wheels!

 

thanks to all who contributed useful info to my thread, especially DrObnxs

before i pull the trigger and purchase $300 camber plates i have a few questions.

having negative front camber (from -1 to -2 degrees) would make me put my rear sway bar (h-sport comp 25mm) at its softest setting

this would mean having more body roll/lean while optimizing front contact patch?

i know my sway bar is at an aggressive setting but i like the absence of body roll, i'm not sure i want to give that up

but i understand the concept of how negative front camber would help handling/reduce understeer, while at the same time causing me to back off the rear sway bar (which would reduce oversteer) and improve front/rear bias handling overall

i get the idea, just not sure if i like it

 

If you do -2 or -2.5 you could prolly leave your RSB at stiffest setting, but play with your PSI, (to mitigate understeer/oversteer) set your front at what feels good, and run a bit higher in the rear is the common practice. But I suggest you ""defualt" your psi somewhere like 33 to 36 cold psi front and back, find an empty parking lot and if you get too much understeer drop psi in front, if you like more drop-throttle (brake) induced oversteer increase the rear PSI. Until you get it right where you like it. It will take some tinkering to get it right, but air is free at many gas stations. I have my front camber at 2.4 (it was the most I could run safely due to wider tires impeding on JCW struts)

So for example stock camber is more like this [ ] and when you make a hard LEFT turn it would turn to this / / decreasing your right tires contact patch, which is the most important for cornering left.

With a more aggressive front camber your front wheels would look like this / \ but when make a hard LEFT they would look like this / ] increasing your right tires cornering ability to its fullest.

Note: buy a good digital gauge or a very good dial gauge, don't trust the gauge at gas stations

Note 2: Negative camber will increase inner tread wear.

Note 3: I won't suggest you improve your driving skills via DE, cause I know it not what you asked for, but I will suggest you go to local Auto-X events and buddy up with the MINI guys, and they will share some of the secrets of the black magic art of suspension fine tuning. Also, good to safely (legally test your suspension set-up.

 

for you to ponder....

Roll stiffness is affected by a couple of things: Sway bar stiffness and spring stiffness being the biggest two. You can have softer bars with stiffer springs and have the same roll stiffness as softer springs and stiffer bars.

But what is it that you want? Do you want a corning feel like the car stays flat or do you want a car that is fast in the corners? Here's an example.... When I had the suspension put on my Mustang I selected to have one that was really nice on the street (it's an old convertable...) the springs are softer as is the front bar. The car leans a lot more in corners than it used to, but it's much much faster through those turns because the tires can do thier job better.

Many are under the assumption that stiffer is faster. While this is a bit true for race cars, it's not very true for cars on the street. The reason why is that the surfaces we drive on are crap, and too stiff tends to bounce on the imperfections in the road and you ultimately loose grip.

Matt

For your reading pleasure I suggest you read this thread. It's not exactly the same issue, but it's the same situation. Someone put on "higher performance" parts (in this case larger wheels with lower profile tires) and found that the car handled like craap in turns. After a bunch of fighting back and forth, he finally listened and learned that it's how all the parts work together that makes the suspension work well. Another interesting thing is that it illustrates how "stiffer" (in this case tire sidewall) will degrade handling in street driving.

 

wow thanks guys, i learned a lot from this thread!

i don't go to the track, don't plan on it, i just like enjoying the tight cornering on street roads. i just want my mini to corner flat, that's why i keep my rear sway bar on full stiff, i don't rly care about going fast thru the turns

-Dr Obnxs

about the crappy road surfaces we drive on, aren't most streets generally concave?

so wouldn't negative camber contribute negatively towards optimizing contact patch?

i understand that camber plates work well on the track, but unless the street surface was smooth and flat (and most roads are not) wouldn't this negate the purpose of camber plates/negative camber?

 

if you make your car flat by unbalancing the front/rear roll stiffness the way you are going, you will spin when in an emergency situation, or if you have to lift off the gas in a turn. Don't plan for every day, plan for the what ifs.

As to the question of camber vs road type, it has less to do with the road surface per se, then how the car changes in a corner. The mac struts up front have little camber gain. That is when the suspension changes in a turn, and the outside compresses and the inside extends, the camber doesn't really change much. The car leans and this means the the wheel is no longer perpendicular to the car. That's why serious cars use something called "double wishbone" or "unequal a-arm" suspensions. They are designed to point the top of the tire inwards under compression to help maintain the contact patch as the car leans and the tire shears (due to sidewall flex).

At the back of the car, we have a trailing arm setup with lateral control arms. Because the arms inner pivots are closer together where they attach to the subframe than at the trailing arm, the camber changes as the suspension moves. Much moreso than the front. This is also why you need to do something about camber in the back when you lower the car....

Now, if you have a lot of negative camber and always drive on freeways in the panhandle of Forida or something (lots of flat straight roads), then going to too much camber will cause unequal wear. If you take that very same set-up that wears unevenly with mostly freeway driving, and bias the driving to curves, you may get even wear, or if driving really agressively, still get more wear on the outside.

It's about matching the settings to the driving environment and the driver. There is no "best" set up, there is just what works well for you.

But I fear that by keeping the car flat in turns by just changing the rear bar, you have screwed up the front/rear roll stiffness bias, resulting in a very aggressive potential overstear bias, that is not good for either ultimate traction or safety.

There was a track even out west in CA at Laguna Seca hosted by Phil Wicks a few years ago. I don't know why, but a bunch of people had comp rear bars put on thier car before the event (just bad luck I guess) and at least three of the cars spun, and I think one or two rolled in the gravel.

If you want your car to handle a certain way, find a performance suspension alignment shop in your area. Talk to them about how you want your car to behave, and follow thier lead on how to set up your car. They will have tons of man-years of experience on setting cars up, will be able to read your tire wear patterns, and you will end up with a car that handles like you want in that maximizes safety AND handling charecteristics.

Matt

 

I agree, modding to learn on, that day is not wise.

If this is the gravel @ the bottom of 1 after the 1st of the double apex, I have seen many cars spin here, and end up in the gravel trap.

From the Mondial Ford/Barber cars, to factory 5's, to Vette's all come loose here. Huge charging straits get poeple in hotter than their skill set can handle. Double apex's are tricky, and even more tricky @ speed for most.