Lap times: 15" vs 16" wheels

[WP0ZZZ]

Has anyone done lap time comparisons between using 15" and 16" wheels on track?

I'm particularly interested in the lap time difference when the rolling radius of the rear tires is held constant. For example between the common:

225/50 R15 (about 23.9" diameter)
225/45 R16 (about 24.0" diameter)

Both have nice options from Toyo and Yokohama.

[Jonny042]

Grassroots motorsports have done numerous tests over the years and pretty sure they've covered that ground.

[Bill Verburg]

Originally Posted by WP0ZZZ

Has anyone done lap time comparisons between using 15" and 16" wheels on track?

I'm particularly interested in the lap time difference when the rolling radius of the rear tires is held constant. For example between the common:

225/50 R15 (about 23.9" diameter)
225/45 R16 (about 24.0" diameter)

Both have nice options from Toyo and Yokohama.

It's going to be pretty much a toss up

the 225/45 on an 8 will have ~5% more grip than 225/50 on 8, if you used 8.5 for the 225/45 that would would go up a bit.

but you lose ~5lb-ft w/ the 16 mostly in the front where the really short 205/50 x15 provides more than 1/2 the difference, 5lb -ft isn't going to be very noticeable at all

[WP0ZZZ]

Originally Posted by Bill Verburg

It's going to be pretty much a toss up

That's what I think too.

It would be awesome if someone could share some first-hand experience!