What's the magic offset number number for an 18x8 wheel if I want to lower a Cooper S but NOT use spacers for strut clearance? Most likely going with KW coils or Eibachs/Koni FSD for about a 1" drop or so.

 

Stock MCS R53 is 17x7 +48mm offset 205/45-17 tire

So if we use 18x8 then offset can be from +45 to +38 mm range with +40 to +42mm being relatively safe.

The more you lower your car the less clearance you have to the tire once mounted. Using tires that have diameter of less than about 24" is safer compared to stock tire diameter of about 24.3".

For a 18x8 wheel then tires could be-
205-40-18 24.4" diam. narrow tire for 8" rim, more comfort.
215/35-18 23.9" diam. most popular size for lowered MINIs.
225/35-18 24.2" diam. Good performance tire selection.
235/35-18 24.5" diam is tall, BFG KDW2 good show tire, noisy for street.

Tire selection varies with each size. Wider tires have slightly higher risk of rubbing on the inner fender plastic liner. Wheel offsets that are closer to +38mm have more risk of rubbing than +42mm.

You can use this calculator to play around with the numbers-
http://www.wheelsmaster.com/rt_specs.jsp

Since this is 1st gen suspension forum we will assume you have an R50 or R53 MINI and 12mm wheel bolts. If you have an R56 then 14mm bolts, make sure the wheel vendor knows what year MINI you have.

OK, whenever you change wheels you have to consider tire and tire size. If you have an R50 you have less power and want less weight not more weight and 18x8 rims are both larger and wider than stock so you might be adding weight.

Keep in mind that if you are only doing street driving you don't have to be as concerned about heavy wheels but larger wheels also usually mean shorter stiffer sidewalls and a harsher ride except over smooth roads and more risk to damage your wheels, tires or suspension if you do hit a pothole at speed.

Using no spacers is a good idea and any thicker spacers will require long enough bolts or longer studs to give enough threads to lock the wheel. You usually can use stock bolts once the spacer is more than 3 to 5mm.

What wheels and tires do you have now? What are you going to use the MINI for mostly? If these are show wheels and hardly used then you can run almost any sort of wheel and tire combo as long as it fits. Some show cars have wheels put on at the show that rub so much they cannot be driven. Only for show. If you plan to use these wheels and tires for street or daily use then that would require some thought. Also look at your budget. Remember that any lowering reduces clearance and usually you will need an alignment after suspension height is changed but do alignment last.

Don't forget that many aftermarket wheels will need a centering ring that allows you to fit your wheel on the MINI hub more easily. MINI hub bore is 56.1mm. Ask your wheel vendor for center caps and rings if needed.

 

Wow, thanks so much. I currently have a BMW 1-series after trading my 03 Cooper S but it won't last. I need to be back in a Mini so I will be looking for a used 05-current car. I prefer the look of the R53 and would be happy with a moderatly lower car with 17" wheels. I had H-Sport springs with Koni FSD on my old car. The R56 with it's greater heft and SUV ride height would need the 18s and a greter drop. I do only street driving and prefer not to loose my fillings over every bump. Thanks again for all the info.

 

Well there are many options depending on which MINI, suspension, and how aggressive you want to be.

17x7 to 8 or 18x7 to 8 are possible.

Tires vary a lot and some only come in certain sizes.

Your budget is another factor as wider wheels and tires usually can cost more.

Since this is purely street driving then weight is not as much a factor but generally if you can keep weight down that is a good thing.

Tire selection is part of the equation. If you like handling and performance with some comfort then you have to be careful what you get. If you have a budget then that constrains things a bit.

If you live in a place with some cold weather and you don't want to have winter wheels and tires then All Season tires become a consideration.

Longer treadlife tires usually mean less performance, all weather use, sometimes good comfort and variable prices- but usually ok.

The best handling tires will be faster wearing and some cost more.
Extreme and Max Performance Summer tires are great on the street but a bit of overkill and don't uaually last as long. Some are noisy but some are comfortable enough for daily use.

Ultra High Performance tires are in between and come in Summer and All Season forms. They won't handle as nicely but they do last longer and some are well priced and come in sizes that will work.

If your roads are bad and full of potholes then 18" rims are not going to be easy to use safely. 17" rims and 205/45-17 or 215/40-17 would work on a lowered MINI on bad roads. Some 18" tires have a softer sidewall and are OK in 215/35-18.

Best is to plan ahead. 2005 MCS is a good choice. BMW 1 series is a nice car but NOT a MINI.