[1day]

Originally Posted by ake109

I keep hearing and reading that if you swap your say 205 tyres to 235 tyres, the wider width of the 235 saps your fuel economy but gives you more grip.

OK, first the fuel economy due to rolling resistance bit:

Assuming the same inflation pressure AND rolling radius, shouldn't the 205 give the same contact patch area as the 235? Newton's law on equal and opposite reactions and all that. In fact, with the same rolling radius, the 235 will have a thinner profile and thinner profile tyres IIRC use higher inflation pressures. So the 235 actually has a SMALLER contact patch area.

You don't need a physics major to tell you that the 205 tire is going to be lighter than the 235. That has a bigger impact on fuel economy than the footprint, especially in stop-and-go traffic.
As far as grip..I would rather have a sticky -narrow- light tire, than a hard compound tire that's twice as heavy and twice as wide.
Rolling resistance has as much to do with tread design, tire compound and weight. Probably more so than the dimensions of the tire.

[ake109]

Originally Posted by frostyrock7c

, ...i.e. more surface area = better heat displacement... .

But here we go again. A wider tyre doesn't = "More surface area"

I think we have all agreed on that. Wider yes. Larger contact patch no.

So does it come down to wider tyres giving more grip because :

The normally have lower profile and stiffer sidewall

They normally tend to be higher end tyres with correspondingly better compounds

And lastly (the question I am trying to ask) - Does contact patch width matter more then contact patch length?

[frostyrock7c]

Originally Posted by ake109

But here we go again. A wider tyre doesn't = "More surface area"

I think you meant a wider tire doesn't = more "contact patch". A wider tire does have more surface area as there is more matter for heat to be displaced. It doesn't matter if all of the rubber contacts the road, it still aids in at least some heat dissipation.

[Wolverine 250R]

Originally Posted by ake109

In fact, with the same rolling radius, the 235 will have a thinner profile and thinner profile tyres IIRC use higher inflation pressures. So the 235 actually has a SMALLER contact patch area.

A wider tire that has the same radius as stock will have the same profile as stock.

ex: 225/45-17 has the same sidewall as a 255/40-17

[blindfold]

Originally Posted by ake109

And lastly (the question I am trying to ask) - Does contact patch width matter more then contact patch length?

width is more important, it's the whole point of going wider to gain the batter contact patch shape

[jrdriller]

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