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[2woody]

195/65 x 15 would be your best choice

[Shackeng]

I agree, but this entails buying, and storing, yet another set of wheels, I have one set of 16" alloys already in the garage, hence consideration of 205's.

[cem_devecioglu]

It would be great if someone could write an accurate calculator, actually.

Oh, 5h1t! that's as good as volunteering.

[cem_devecioglu]

from last week's thread.... (adjusted to suit)

the maths on all of these websites and in the hand calcs is worng, sorry.

the tyre business and the auto business doesn't use them because they're wildly inaccurate. The problem stems from the static figures vs. what actually happens on the road. It's for that reason that every profile is tested and the measured figures are what's used. There are two important figures, the wheel revs per mile ( which gives you the gearing ) and the hub height, around which the suspension geometry is designed. Using measured figures takes out the installed sag and the effects of slip.

Omega B is designed around 817 wheel revs per mile. Anything between 807 and 827 will be acceptable ( i.e. 5 either way )

some comparisons :-

205/55 x 16     811 wrpm     594mm diameter on the car     654mm diameter calculated
245/50 x 16     811 wrpm     594mm diameter on the car     651mm diameter calculated
235/45 x 17     820 wrpm     595mm diameter on the car     643mm diameter calculated

tell you what - I'll write a sticky on the subject......

honestly, rare drivers keeps the tire pressures upto spec (and I'm not one of them ) .. so most of the tires are more flat compared to the original calculations..

[Kevin Wood]

honestly, rare drivers keeps the tire pressures upto spec (and I'm not one of them ) .. so most of the tires are more flat compared to the original calculations..

I over-inflate the ones that lose pressure to compensate for the fact that I can't be @rsed to check them very often, so on average, they are perfect.

 

[cem_devecioglu]

honestly, rare drivers keeps the tire pressures upto spec (and I'm not one of them ) .. so most of the tires are more flat compared to the original calculations..

I over-inflate the ones that lose pressure to compensate for the fact that I can't be @rsed to check them very often, so on average, they are perfect.

 

so you are one of those drivers

seriously , roads are so bad that I always use 2-3 psi lower than the normal spec..