I'm considering changing my '09 base wheels 175/65 15 to a set of '05 S Size:17x7, Lugs: 4, Bolt Pattern: 100mm, Offset: 48mm with 205/45 17, is this a good idea or not?

 

Well it can be both! Our Justa’s have lightweight wheels to help with the lower hp and torque. The tall 176/65-15 tires also give a better ride. Depends on what you are going for; A new look and sportier ride?(note also harsher). Wider wheels and tires for greater contact patch? (But also tend to be worse on fuel mpg). I love my White Holies on my 05 Justa and have a set with performance tires and can tear up the Dragon and autoxes quite nicely.

Have fun! Make your MINI what “you” want it to be!

 

I would think about going to16" instead.
Better ride and you could still use a 205 x 50 x 16 tire.
Look at Enkei PF01 or RPF01 for lightweight well made wheels.

 

I agree that 16” wheels are a great compromise, but be careful tire choices are more limited. Please check tires before buying wheels to make sure you can get the package you desire.

 

I love my 2005 MINI Cooper R50 with 15” White Holies

 

You have a Base Cooper? Using it for street driving only? No track or driving events? Any cold weather under 40 degrees? How many miles a year do you drive?

If you have a base Cooper then standard wheels and tires were likely 15" or 16" (with runflats). You can mount and use 17" MINI wheels no problem but you get tire sizes with much shorter sidewalls that are very stiff and firm riding. On smooth roads it's OK but on bad roads the taller sidewall of 15" or 16" tire sizes are much better.

Also if you do switch to 17" wheels then the most common tire sizes are 205/45-17 and 215/45-17 in order to fit the MINI OEM suspension. Base cooper and Cooper S suspensions are very similar. So mostly you have 45 series sidewalls and not much else. Most tires in these sizes are summer tires but there are some Ultra High Peformance All Season tires that are OK for cold weather.

If you choose 15" then you can use 175/65-15, 185/65-15, 195/60-15 or 205/55-15 for street driving. On OEM 15x5.5" wheels, I have 195/60-15 (Grand Touring All Season) and they work great for daily driving. Notice there are a variety of tire sizes and sidewalls that are much taller. A tall sidewall can flex more and absorb some shock but it's also less responsive for crisp handling. Everything is a compromise.

That's why some suggest a compromise and consider a 16" wheel like 16x7". This usually works with 205/50-16 or 205/55-16 tire sizes.

Any time you use a smaller diameter wheel or more narrow tire sizes you tend to reduce weight and cost, while decreasing rolling resistance and improving mpg a little. These alternate tire sizes do give slightly different odometer and speedometer readings but not that bad.

 

Thanks for all of the good ideas. I'll be going with the 17's for now since I was able to get the set for under $100. However, I'm going to be on the lookout for a set of 16's as I think I'll probably enjoy the ride a little better in the long run.

 

I note that no one explained why the ride is harsher on the bigger wheels. It's air pressure. Maybe you're putting 35psi into your 15" tire and 50psi into a 17" tire. Low profile tires need lots of air, otherwise they can "snakebite" if you hit a hard bump. That's caused by the rim bottoming out on the bump. Potentially one can even bend a rim. It's important to understand this because it allows for some flexibility. If you get 17" wheels and the tires want 50psi max cold, put in 45psi and see what the profile looks like and if you can feel a softer ride. Then, depending on the quality of roads in your area, try 40psi. Just realize that, as you drop air pressure, you become vulnerable to damaging the tire because of the big hole you didn't see coming.

The 17" tire at 40psi will feel just as soft as the 15" tire at 40psi.

Note that you have to account for temp. In daily driver mode, tires don't gain in temp much. You can assume that your tires gain a psi for every 10deg. So as you're experimenting with tire pressure and feel, don't put 40psi into your tires in 90deg in Aug and fail to adjust for the fact that Dec is 20deg. That's 7psi of pressure drop.

 

For all MINIs it's common to use about 32-36 psi for street tires no matter what size wheels you run. Over inflation will result in more wear on the middle treads. Low profile tires need the same air as any other size tire for the MINI from 15" to 19" wheels as determined by the owners manual.

I daily drive on 17" wheels with non runflat tires at 32psi and they are no different than when I use 15" wheels and taller sidewall tires at air pressures from 32 to 36 psi. If you can bottom out going over a bump on a 17" rim then you need to be careful and slow down or avoid the bump if possible.

Is the ride harsher with bigger wheel diameter? Yes, maybe and mostly due to having a shorter and stiffer sidewall but not necessarily if you use a tire that is built for ride comfort.

If you look at a modern Max Summer tire like Michelin Pilot Sport 4S which comes in 17" sizes it will give you excellent ride comfort for daily use at 32-34 psi but it's costly. A 15" or 16" wheel allows for other non runflat tires in the Grand Touring tire class with taller sidewalls that are softer and allow for good ride comfort for street use and usually lower cost with good tire selection of sizes compatible for the MINI.

 

People tend to run tire pressure based on the owners manual and door sticker because they don't know any better. Every tire has a design pressure that varies with the weight of the car, that's why they have the "Max Cold Pressure" molded into the sidewall. "Over inflation" isn't relative to the sticker, it's relative to the tire's design pressure.

Rides are not harsher due to the bigger wheel diameter, it's the air pressure, and (as you mentioned) sidewall stiffness, but the latter is a small player. Thought experiment: Imagine a 1' square block of cement and a 5' square block of cement. Now put a big round balloon on top of each. With your finger, compress each balloon by 2". Can you sense the difference between the small block vs. the big block? The firmness your finger feels is a product of the air pressure in the balloon, not the size of the cement block.

Certainly tires vary in sidewall stiffness and I'm no tire engineer. It's a big player in car handling so one can't monkey with it much or handling will dramatically effected. Design pressure being equal, tires designed to bear heavier loads have stiffer sidewalls to do it.

 

Using the tire pressure as stated in the owners manual is the correct approach and is not because owners don't know better.

https://www.cars.com/articles/how-do...1420676891878/

OK, tire sidewalls can be so stiff as to not be deformed from pressing your finger to check for relative inflation with changes in air pressure. The most extreme example is any runflat tire. It carries the load with little or no air in the tire and you can't tell it's flat or low, hence TPMS is needed to assist.
A tall sidewall standard load tire is soft but a 205/45-17 tire used on the MINI might not be as easy to assess if pressure is higher or lower. The amount of air used for driving can be adjusted up or down depending on your use but rolling resistance, tire wear, handling and ride quality may all be changed.

XL load rated tires are common and are designed with a stiffer sidewall construction and allow for higher loads. Since sidewall is stiffer the ride quality can be firmer but not always, depends on rubber compound, tread design and other factors.

 

The problem is that most what you read on the web about this sort of thing is written by non-engineers for simple consumers (vs. knowledgeable enthusiasts).

Thought experiment. Pull off our OEM wheel/tire combo and imagine installing some crazy tall wheel and extremely low profile tire. You've not got an inch of sidewall. One inch of tire compression and the tire is going to snakebite on the rim. Tire mfr recommends keeping tire above 50psi. You gonna go with the psi sticker on the door jam or with the tire mfr guidance. You figure the guy that came up with the spec on the door jam sticker knew what tires you're putting on?

Putting on tires that differ from OEM, but choosing OEM guidance instead of the guidance from the tire mfr is silly. Where does that kind of thinking end? If you put a crate engine into your 60's muscle car, you gonna adhere to the engine maint guidance from the engine mfr or the car's owners manual? As I probably mentioned in this thread, I race BMWs. Racers set tire pressure with great care. No one knows how to get max performance out of a tire like a racer. We're a thousand times more obsessive re. tire pressures then the average Joe. Each corner of my car is set at a different cold pressure. The delta between hardest working and least working tire is 4-5psi cold. We carefully account for ambient temps. All this is very tire dependent. The optimum cold pressure difference between Toyo RR's and Hoosier dry tires is prob 4psi. Different tire designs so different optimum pressures.

Each month I tow a trailer, the better part of 8k lbs, 8-12hr round trip. My tow vehicle's OEM tires were standard light duty junk.. After those wore out I put on better tires that were designed to support more weight. The max pressure on the new tires was 50% higher than the old tires. If I went with the pressure sticker on the truck's door jam I'd be putting in not much more than half of the air the new tires needed to handle max load, and they were going to be handling a fair fraction of max load. So I inflate them to something a bit short of max load. If I didn't, the tire sidewalls would bear too much of the load and the additional sidewall flex would result in early failure.

Tire pressures should be a product of the car's weight and tire mfr recommendations. If you have tires similar to OEM, fine, go with the decal. But if your tires differ from OEM, look into what the tire mfr says about proper inflation of their tires.

 

OK, so I thought we were discussing what the OP had a question about. The OP had a choice of 15" OEM vs 17" OEM wheels and the tire sizes that would fit a MINI.

Sure, I can see your point that in the extreme example if you ran a wheel that literally required a tire size that doesn't exist for the average consumer then air pressures would NOT apply that came with the owners manual. If that is your point then yes, one can modify air pressure to be appropriate to the exact use and fitment required.

I would argue that for street driving (not racing which is totally different) if one used OEM range wheels and tires sizes that fit the wheels and fit OEM suspension then air pressures will likely in the same general range with small adjustments needed for the intended use. I would not be very concerned about tire design max pressures which are there for safety reasons.

https://www.tirerack.com/tires/tiret...jsp?techid=196

 

Mini has different tire pressure recommendations for different tire sizes and even between models. They also recommend different pressures for the same tire when you are driving over 100 MPH. There's 6 pages of tire pressures in the 2019 F56/F55 owner's manual.

 

Yes there is a range listed for OEM wheels and tires for street use 32-35 psi cold for 2009 Base Cooper

https://tirepressure.com/2009-mini-cooper-tire-pressure

 

The 2019's go from 33 to 49 PSI depending on the tire size and car.

 

I went back to stock because I felt the comfort outweighed the discomfort. Looked good but the ride sucked.....

 

Also consider how bad or OK your roads are where you drive. Poor roads are harder to live with as wheel diameter gets larger than 16".

My 2003 MCS gets 15" OEM wheels and Grand Touring All Season 195/60-15 tires for daily street use and it's OK. Low cost, less rolling resistance, forgiving on bad roads, good enough in dry or wet but not the crisp handling of 17" tires. I also have wheels and tires in 16" and 17" and have used them for daily driving in the past. The lighter 15" wheel and tire combo allows for good acceleration and decent braking.

 

Change in tire size = performance. MPG can be improved by using smaller or skinnier tires. Off-road tires that are larger or wider may be preferable. Change in wheel size = change in appearance. Some people believe that large or "oversized" "rims" are attractive. Some people do not another option is tire pressure. They appear to be more flashy. Smaller wheel sizes are also better for off-roading.

 

OK, the thread's original question was based on the option for tire and wheel size for a 2009 Base Cooper but the idea can be applied to each MINI no matter the year or body style.

Yes you can change wheels and tire sizes but there are limits to what might fit and not rub depending on if you use OEM or aftermarket suspension.

"Change in tire size = performance. MPG can be improved by using smaller or skinnier tires. Off-road tires that are larger or wider may be preferable. Change in wheel size = change in appearance. Some people believe that large or "oversized" "rims" are attractive. Some people do not another option is tire pressure. They appear to be more flashy. Smaller wheel sizes are also better for off-roading."

Change in tire size = performance. - tire size can affect many things including fitment, which tire models are available, the classes of tires available in a given size or range, and the performance traits of a given tire model.

MPG can be improved by using smaller or skinnier tires. - a more narrow tire may allow for less rolling resistance, small tire size alone may not improve mpg, many eco tires are made with rubber compounds better for mpg as well as tread designs for less rolling resistance, look for tire models that market for better economy if you want tops in mpg.

Off road tires that are larger and wider may be preferable. - Yes if you are doing only or mostly offroading. Some tire sizes will require more tire clearance and an off road suspension, off road tires tend to use tread blocks that are large and deep for offroad use and are very noisy for street or highway use and they get poor mpg and not so good handling or comfort for daily use.

Change in wheel size = change in appearance. - Yes to some degree this can be the case, not as much if one inch difference in diameter of wheel there is a difference. As the tire diameter gets smaller the tire sizes that fit will have a taller sidewall for more ride comfort but less sidewall stiffness and less sharp handling. A result of a wheel diameter change is the limitation of tire sizes that work and still allow for an OEM tire diameter to fit the suspension.

Large rims are attractive. - To some yes because you can use smaller shorter sidewalls which can look aggressive or cool. But larger rims are heavy and costly and tire selection gets more limited for tires that are better for daily driving such as Grand Touring All Season tires. Also tires for larger rim sizes can be more costly.

The option of tire pressure. - for a little better mpg using higher tire pressures is possible. You can hypermile more easily and get less rolling resistance. Best used for highway commuting.

Smaller wheel sizes better for off-roading. - Larger wheels may not always work with off road tire models and still fit a MINI suspension. Some smaller wheels may work and give some grip for off roading, search for rally cross tires in 15" to 17" wheel sizes that fit the wheel diameter and have tire diameter about 24.4" or less.

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