Hi all,

I have just ordered an Alfa Romeo 147 JTD 16V. This is quite a technical message regarding tire sizes. The factory standard tires are: 195/60R15.
The factory gives as optional 16 inch alloys or 17 inch alloys with the following tires respectively:
205/55R16
215/45R17

Now I was wondering... for the 15 inch standard tires the overall rolling diameter is: 2*(.6*195)+(15*25.4)=615mm. Am I right?

For the 16 inch option similarly: overall rolling diameter=631.9mm:confused: Thus you can see that the factory has allowed an increase in 15mm to the rolling diameter. :banghead:

For the 17 inch option similarly as above: overall rolling diameter=625.3mm! :banghead: :banghead: :banghead:

Now I have ordered the 147 with the 215/45R17 tyres and 17inch rims however I would like to go to 225/45R17 tyres. Would I damage the suspension, or handling/performance of my 147? Moreover since all safety features take the speed as input will it GREATLY affect these components? With 225/45R17 the overall rolling diameter would be 634.3mm thus .3mm larger than the 205/55R16 option.

Excuse me for this lengthy message but I had to explain my situation very clearly. Thanks a million. Impatiently awaiting your response...

Best Regards,
Gilbert.:confused:

Given Alfa's are not available in the states we don't have any fit info on your car . . . in general though we recommend staying within a 3% margin of the original diameter to avoid issues with ABS, traction control etc

I see that's what I didn't know... about the 3% margin. Thanks a real lot.
So I would be over the 3% margin by about .95mm which is nothing right?

So I can safely go up to 225/45R17. gonna order some of those Goodyear F1 Eagles then :biggrin:

Thanks a real lot for your help... much obliged

3% versus the original tire size.