Hi folks, not sure what to do here.

I want to increase the general performance of my car i.e 0-60 0-100 1/4 mile and top speed

I just want some advice re tyre wheels size,

I have 16's at the mo with a 40 profile 195/40/16 toyo t1r's

I'm thinking that if I got some 17" wheels and some r888 (205/40/17) that would work as i'm struggling for grip in 1st and second if I go for it. But I don't want the expense of buying a new set of 17's (£700?) and then some r888's (£300+) aswell, can I get some r888's fpr my wheels with a 50 profile and they have the same overall diameter?

The reason being the 16's are limiting my top speed

I'm getting the car re-mapped next week my the dreamscience boys so i'm gonna ask them to raise the limiter so I can go faster in 5th but i'm already at 7k so I have chosen wheels tyres as the best option



sorry for the long ass post but i'm trying to get my point across

Thanks

 

Smaller overall diameter better for acceleration (lower gearing).
Larger overall diameter better for top speed provided the power is there. It's a compromise.
Surely you have to find something that will fit on the car.
Check out Toyo website for sizes available on 16s and 17s

 

I know that Dave, but i'm saying will my 16's with a 50 profile be the same as 17's with a 40 profile?

the fact that I will have traction with the r888's & 17's mitigates the fact that i've gone from 16's to 17's (cos you would think 17's would be slower 0-60 wise, but i'm saying going to r888's will give me alot more grip and there for I can get a better start)

Cheers

 

http://www.miata.net/garage/tirecalc.html

 

205/50/16 are roughly the same footprint as 205/40/17 anyway

 

cheers Twellsie

I got from that link

Tire Size Comparison

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
195/50-16 3.8in 11.8in 23.7in 74.4in 852 0.0%
205/40-17 3.2in 11.7in 23.5in 73.7in 860 -0.9%

So am I right in thinking the 16's would give me a better top speed?

 

1% difference in size is LESS than the difference between new tyres and old.

 

but don't forget i'm not going from a 195/50/16 to a 205/40/17 i'm going from a 195/40/16

hmmmm so it doesn't matter either way except me getting 17's will cost alot more

 

The 17s are unlikely to bring anything useful to the party TBH unless you need clearance for bigger brakes.

IMHO you would be better off just getting decent tyres and replacing all your suspension bushes if you havent done so already.

 

This is the calculation I needed

Tire Size Comparison

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
195/40-16 3.1in 11.1in 22.1in 69.6in 911 0.0%
195/50-16 3.8in 11.8in 23.7in 74.4in 852 6.9%

Which gives me a 7% increase in top speed? Or am I reading it wrong?

 

Would need to see your torque curve, and a datalogged run up through the 5th gear to the current max speed to comment on if higher gearing is likely to improve your top speed, it might actually make it WORSE.

 

how could it make it worse chip?

is that because my car would struggle to make the wheels turn as fast with a larger diameter than it does with a smaller diameter?