Sponsored by The Tire Rack

[Tom K.]

Since my worn out rear Goodyear NCTs have been discontinued, I decided to replace all four tires with non run-flat Continental DWS rubber at my excellent local tire shop. Upon arriving home, I noticed that one of my rear wheels was very dirty but one of my front wheels was relatively clean, and it turned out that one of the 205/50R17 tires had been mistakenly put on the rear and one of the 225/45R17 tires had been put on the front - although they were on the correct rims. When I returned to the shop, they put me at the front of the line (it's usually a 1~2 hour wait), inspected and changed the wheels, corrected the pressures and I was on my way in about 10 minutes.

The assistant manager apologized and explained that apparently one of the tire mounters saw the 225/45/R17 marking and assumed it was a front tire - as this is the case on some 3 series models. So since us 1ers still don't get no respect compared to 3ers, it's a good idea to double check these things. (My next car will not have staggered wheels!)

Tom

[JimD]

Tom,

Thanks for the tip. I agree about the staggered wheels/tire sizes. Seems like too much trouble for too little benefit.

Another thing I am thinking about is goint up to a 50 series tire to almost correct the speedometer error and probably improve the ride a little. I think tire rack also indicates that we could mount this size tire on the front rims too - make the tires the same even if the rims are not. I think a wider tire probably means a lower gas mileage tire, however, and the offset difference probably means we can do a normal tire rotation so I will probably stay staggered - but possible slightly larger in diameter to drop rpm a little and make the speedometer significantly more accurate. Assuming 3mph is the current error at 60mph, I get less than 1mph error in my calculation just by going up to a 50 series.

Jim

[Tom K.]

Jim, As I hated to discard my two front tires with 1/2 the tread left,I was planning to simply replace my rear OEM NCTs. But I found out there were only 4 in the country (on the opposite coast) and shipping would be nearly $30 per tire - bringing the total cost to about $700 including mounting, balancing & tax for 2 tires. And Tire Rack no longer even lists the Goodyear in the 128i F/R sizes. So I wound up going to W rated, non RFT all-seasons which cost only $600 out the door for all 4 wheels!

The revs per mile difference between the 205/50R17 front and 225/45R50 rear is very small -about 1/3 of 1%. So that wouldn't correct your speedo error. And while going to an oversize 225/50R17 for the rear would be almost a 3% reduction in wheel revs, it seems to me it would exacerbate the understeer. Also, I don't think you would want to rotate 225 rears with 205 fronts!

I guess I'm lucky as my speedo has no discernible error, although the odometer is about 1% pessimistic!

Tom