195/45/16 or 205/45/16 or 205/40/16?

[Herdie172]

sorry if this has been ask before?

got 195/45/16 on turinis which are fitted to a mk 2 172. want more grip so gonna need wider tyres. so was thinking 205/45/16 but how does this effect rolling radius, or shall i get 205/40/16. what will be best as i dont really want speedo to be out. cheers

 

[TheCake]

205x40x16 Speedo might be out though. Get a GPS camera detector with a GPS speedo and it'll never be out again

 

[GordonD]

If its a Renault the speedo is almost certainly already out. It appears to be Renault policy to make their speedos give significantly optimistic readings. Ie, they tell you you're going faster than you actually are.

All the tyre sizes you mention will merely make it more or less optimistic. None of them will get it to the point where it would read low.

The Clio Sports that run 195s - either 195/50x15 or 195/45x16 - run 580 mm rolling diameter tyres. If your Clio runs a 205/45x16, that's a 590 mm rolling diameter tyres. That extra 10 mm reduces how optimistic the speedo is. It varies a bit from car to car but a 590 mm tyre means the speedo would read 100 at about an actual speed of about 95-96. whereas with a 580 mm tyre the speedo would read 100 at about 93-94.

A 205/40x16 is a 570 mm rolling diameter tyre that would slightly increase how optimistic the speedo is. A 570 mm tyre would mean the speedo would read 100 at about 91-92.

 

[Chris n nic]

They are off but not by a great deal...100 is about 98 (pretty much as you said) but not sure how much off higher up. Some cars seem miles off...my m8s mk5 Golf GTi is (130 in mine is near 140 in his) and my m8s Civic Type R was miles out (his words where " I`ve never done 155 b4" even though he wasn`t gaining on me!?) I suppose they aren`t too bothered about accuracy at speeds that you never really use

Chris

 

[Leeshez]

I have 205/45/16 on my car

 

[jooliona]

tyre calculator

http://www.rochfordtyres.co.uk/TyreCalc.asp

mytyres has a very limited range in 205/40 anyway