Spotted this thank's to Steve C' :-

Specification/Sidewall/Radius/Diameter/Circumf./Revs/Mile

205/45-17 3.6in 12.1in 24.3in 76.2in 831
205/40-17 3.2in 11.7in 23.5in 73.7in 860

205/40-17 has a Difference of -3.3%


So can I fit 40's or not ?


:doh:

 

The second figure (40/45) is the height of the tyre wall as a percentage of the width. IE 205/40 means that the wall is 40% of 205 high.

This means that the walls of the two tyres you state will be different heights, resulting in a larger rolling diameter for one. This will affect the accuracy of the speedo.

HTH

 

Hmm ok techy info I found,

Std 205,45,17
Sidewall 3.6in
Rad 12.1
Dia 24.3
Circ 76.2
Revs/Mi 831

New 205,40,17
Sidewall 3.2in
Rad 11.7
Dia 23.5
Circ 73.7
Revs/Mi 860


so your speedo wioll be out by 3.3 % and i'm guessing you tacho will be also !!!

I guess you can fit them but you'll be travelling slower than you think !!

 

lmao..

"WOOHOO! 100mph!" *looks out window as granny overtakes*
"Erm... wtf?" :wtf:


Okay, so you said 3.3% but leave me alone. uch:

 

So if I buy say 17x7 OZ-Superlaggas, I just have to make sure I fit the Michelin Pilot Sports then @ 205/45 then ? :wtf:

Problem being most companies only seem to offer the 40's ??? :2c:

 

Have a look at this page to get the right size.

http://www.tyresave.co.uk/tyresize.html

205/40's are the closest match to 185/55's that are Rover standard alloy tyre size.

 

there's something else that affects the car though.. the actual weight of the wheels.. because they act like flywheel's.

But it's as minimal as the tyre size. *shrug*

 

The unsprung weight of the extra size wheel and tyre will affect acceleration to a degree.

 

so your speedo wioll be out by 3.3 % and i'm guessing you tacho will be also !!!

Speedo will be 3.3% out... Rev Counter (tacho) will be correct still... This isn't related to the wheels...

 

The speedo will be out, but only by a small amount. If you fit 40s and your speedo is dead accurate for tyres of that size, then fitting 45s will have you travelling at 72.5 when your speedo says 70.

In my opinion, that's within a reasonable tolerance - especially as your speedo is probably... no, *certainly* under reading at the moment anyway.

Fit 45s if you prefer - the ride will be marginally less harsh.

 

And if you stick your hand out that car, you fuel consumption will go up. :err:

So there.

 

And if you stick your hand out that car, you fuel consumption will go up. :err:

So there.

That's well funny :hyper: :hyper: :hyper:

 

Well technically.. just opening your window will have that affect.. it's just minute amounts of change though. *sigh*

:lol:

 

Recent studies in the States suggest that driving with your window open can increase fuel consumption by as much as five percent. That's a couple percent more than using your air conditioning.

As with all such studies, actual figures would depend upon the type/design of the car involved, including the engine size and mass of the car, as well as the design of the windows.

 

And wether it was a head wind

 

LoL.. the actual design of the car will also be a factor in the normal fuel consumption. Tss.