Braking distance increases with size of rim ie 26" vs.

[graywolf624]

As far as I know, the bigger the rim, the bigger the wheel = more grip... but thats the end of story.

Not really true. Wider wheels = larger foot print. Larger diameter wheels do not equal bigger footprint. Instead you get a change in the shape of the footprint. (perhaps a slight increase in foot print.. but thats mainly a minor side effect. It isnt proportional as in a width increase, but it does exist since a tire is not a rigid structure. Read my article on tires posted here some time ago for more info.
Thats why in drag cars (non top fuel) the rule is generally small diameter and as wide as possible.

)... the braking distance that will increase is almost meaningless; doesn't it? those are the kind of calculations that you consider zero or simply don't care.

They are more significant then you think.
You can use this tool http://www.csgnetwork.com/multirpmcalc.html
to calculate the difference youll see in rpm at a given mph.

There are only 3 real reasons to go with larger diameter wheels..of varying degrees of importance.
1) clearance for larger brakes.
2) looks
3) higher top speed all other factors equal.

[antonioledesma]

^^ thanks a lot for the link!! needed one some months ago, but not now

and yes, they are more significant than I thought, of course I would not consider them, but you, vansquish and zrfk are the know-all for cars and can consider this factors

[5vz-fe]

Originally Posted by graywolf624 3) higher top speed all other factors equal.

I don't think u will have a higer top speed......(conservation of energy)

[sentra_dude]

Originally Posted by 5vz-fe Originally Posted by graywolf624 3) higher top speed all other factors equal. I don't think u will have a higer top speed......(conservation of energy)

lol...its called having a larger circumference, in effect changing your gearing. Why do you think you have to re-calibrate your speedo when you change wheel size? For each revolution of a larger wheel you go farther...

[Vansquish]

Originally Posted by sentra_dude Originally Posted by 5vz-fe Originally Posted by graywolf624 3) higher top speed all other factors equal. I don't think u will have a higer top speed......(conservation of energy) lol...its called having a larger circumference, in effect changing your gearing. Why do you think you have to re-calibrate your speedo when you change wheel size? For each revolution of a larger wheel you go farther...

Right...but you're neglecting the higher moment of inertia of the wheel and the fact that it actually takes more energy to get it rolling. All in all unless you manage to increase the diameter of the wheel without increasing the moment of inertia of the wheel (i.e. by using a lighter-weight material or redistributing the masses of the wheel so that they lie closer to the hub) then you will in fact lower the top speed of the car. That it takes more energy to move an object with a larger moment of inertia is I think what 5vz-fe was trying to say. Indeed this is the case.

On a slightly different note, one of the other things you have to include when doing top-speed calculations is the fact that there is a fair amount of tire-growth depending on how fast you're moving. In the Mclaren F1, it accounted for something like 5-10mph total in their calculations (simulations showed it would probably max out at 225-230mph, but we know it actually can go faster)

[5vz-fe]

Thanks for typing all that out for me Vanquish.

On a side note, as long as u manage to pull down the same (wheel) horsepower with the larger wheel on a dyno, it will provide u with the SAME top speed. (As Vanquish, higher inertia is a mean of power loss thus it will show up on dyno as part of ur drivetrain loss). Of course, all this is under the assumption that the car is not having a redline limited topspeed.

[23790554]

wouldn;'t bigger wheels be more stable at higher speed?

bigger wheels is also more sexy

[Iwan]

Originally Posted by 23790554 bigger wheels is also more sexy

don't know if i can agree to this if you look at those freaks here.

i think 19/20 inch for 'normal' cars is the maximum - but i remember
back to the early 90's. in those days, 17 inch was the 'maximum'.....


cheers,
iwan