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Discussion Starter #1
My understanding was that all the wheels had a similar outside diameter when fit with the factory tires.

5.5" x 15" 175/65 R15"
6.5" x 16" 195/55 R16"
7.0" x 17" 205/45 R17"

The only difference being the sidewall height, stiffness and tread width. So the gearing ratios and speedometer would be intact when a customer simply ordered a larger rim as an option.

People on the forum have mentioned ET or offset. Is this a function of the rim or the car. I expect it has something to do with where the wheel is centered under the car.

I have pre-ordered a Cooper S, and certainly want the 17" runflats. Does anyone know if these are fitted with all season or summer tires?

I also require winter tires. So how do I do this? Ideally I'd buy the 15" steel rims for winter use, and run the thinner non-runflat tires, but the Cooper S cannot carry a spare, it's used for the battery box. So is there a runflat winter tire manufactured in any of the above sizes?

Does a runflat require a different rim? I think it does. Secondly, does a runflat rim come in cheap steel, or are they all alloy rims.

I could always get a compressor and a can of sealant like the MINI MS. Then choose regular winter tires, but this makes me feel uneasy. I've only had two blow-outs in my life, but neither could have been mended with a can of goo.

Would the MINI MS pump and goo kit suffice legally in the US? I'm pretty sure it's not legal in Canada. All of the North American MINI Spec's call for a 15" with a compact space-saver spare, or 16"/17" with runflats.

Ultimatly, well-maintained, all-season runflats is looking like my only option here, but I don't like it. Canada is not the arctic, but I do visit my cottage and drive through snow-belts often. Snow chains, cables or studs are not legal in Ontario.

One other point I suppose: Put on a compact spare, or try to run on a deflated runflat in snow and you're as good as stuck anyways. Compact spares are nearly bald at the factory and a runflat buckles in the centre, just runs on the two outer edges. On the front, you just spin the bad wheel, and on the back the car starts to spin over 5 mph or on braking.
 

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noahe

Quote
' People on the forum have mentioned ET or offset. Is this a function of the rim or the car. I expect it has something to do with where the wheel is centered under the car '

' The offset of a wheel is the distance from its hub mounting surface to the centerline of the wheel. The offset can be one of three types.

Zero Offset
The hub mounting surface is even with the centerline of the wheel.

Positive
The hub mounting surface is toward the front or wheel side of the wheel. Positive offset wheels are generally found on front wheel drive cars and newer rear drive cars.

Negative
The hub mounting surface is toward the back or brake side of the wheels centerline. "Deep dish" wheels are typically a negative offset.

If the offset of the wheel is not correct for the car, the handling can be adversely affected. When the width of the wheel changes, the offset also changes numerically. If the offset were to stay the same while you added width, the additional width would be split evenly between the inside and outside. For most cars, this won't work correctly.'
Taken from:-

http://www.tirerack.com/wheels/tech/offset.htm

where there is a diagram which, for some reason, I couldn't copy & paste.

I did know what 'Offset' was already, honest. This site has a lot of info on wheels & tyres, (Sorry, tires!), brakes, suspension etc.

Merry Christmas, ( It's now Christmas Day in England.)

Geoff Poad.
 

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Standard R53 tyres will be 'all season'. The Cooper S on 16" and 17" will be run flat tyres rendering the IMS (can of goo) and space saver wheel (no room - the battery is in the floor of the trunk/boot).

The run flat rims are standard (unlike the old Dunlop system) but the tyres are unique - e.g the Good Year F1 Eagle with EMT.

For snow, 15 x5.5 steel wheels are required if snow chains are to be used (clearances) with an IMS. Not sure of the legalities in Canada, but I believe a Lamborghini Diablo has a pump and goo system - are those sold in Canada?
 

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BMW M Z3 and M Coupe, have similar setup as well. All selling BMW dealerships have to have a front and rear tire available for those cars at all times, I've heard. :cool:
 

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Discussion Starter #5
For Ontario, Canada, here is part of the text of the Motor Vehicle Safety Standards (MVSS) regulation that all vehicles must conform to, as outined by the Highway Traffic Act:

1. Tires
Tires must not have cuts, breaks, or show excessive un-even wear. Tire wear bars must not be showing. Tire tread depth shall not be less than two/thirty-seconds (2/32) of an inch of an original tire. The vehicle must have a spare tire, fully inflated, and in the same condition as required above. Tires must all be of the same type (either radial or bias).

So that's about that. I hope there is a bill that ammends this somewhere, because Lamborgini Diablos and Chevrolet Corvettes ARE sold here, so someone is getting around this. It often takes a while to get the text of the law changed. I cannot imagine that a police officer would in-practice issue tickets for having a tire that actually exceeds the safety requirements.

Does anyone know if a run-flat tire is clearly marked as such on the tire's sidewall?
 
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