help with tyres

[P15UL T]

was looking in to replacing the rubber on my car
i have two yokohama advan a-046 on one side which are pretty worn and two bridgestones potenza rf 040 on the other which are ok
so want to get them all the same and dont know wether to go for another 2 bridgestones or four new ones altogether.
seen these on ebay and wondered what you all think of them
215/40/17 zr toyo proxes t1-s for £69.99 inc postage each
would there be any difference changing from a 45mm tyre to a 40mm ?
cheers guys

 

[Duncs]

you will be hard pressed to replace your tyres as it sounds like they have jap spec fitted which are not available in uk. (unless somebody has a couple of spare for sale on here)
never used the toyo but a few have them fitted, i put goodyears on mine and using the uk spec tyre also softens the ride a bit, not sure about the change of profile, smaller profile less rubber, harder ride?

 

[P15UL T]

cheers for your imput, didnt realise you couldnt get those here
probably just go for a full new set
the toyo's i was looking at look sweet 8)

 

[phil_444]

Lots of the people on the civic forum rate federal tyres, i cant remember the model but they seem to go down well for around £55 each

 

[Trung]

DO NOT use Federals. :!:
In this world you only get for what you pay for.

 

[Zero7]

I've just got rid of the Jap tyres and fitted a set of Goodyear F1's and these do grip very well and the ride is much better, highly recomend them.

 

[anticlaus105]

Woundn't dropping from a 45 to a 40 reduce the total circumference and hence cause your speedo to read over and your miles clock up faster than they actually are doing?

Or does it not work like that?

 

[P15UL T]

but that would mean if you changed to a 18" or 19" wheel you mileage would be reduced. :?
who knows???

 

[T666YPR]

Apparently there's some new legislation coming in about the 10p/c innaccuracy with speedo's etc soon,won't get much joy from the manufacturers about the discrepancy 'til it happens though.

How do we stand with speed cameras etc with misreading the speed?

Can we say "modded" and so have no proper readings?

Simon

 

[kingston]

http://www.goodyear.co.uk/services/guides/reading_a_tyre.html

Has anyone tried Yoko A539's on theirs yet?

For cheap Tyre; http://www.elite-design.co.uk & http://www.topgear.co.uk

Car speedos become more inaccurate the faster you go, i think at about 40 mines 1mph out (got photo evidence to prove so too :cry: :evil: ) An interesting item to note however is that if you go up in size by one inch, it can overcome the mis-reading discrepancy & give you actual speed.

 

[Duncs]

when the cars are ESVA'd part of the test is to do a speed test on a rolling road, (freewheel) this check the accuracy of the speedo, and the conversion.

 

[Evs]

but that would mean if you changed to a 18" or 19" wheel you mileage would be reduced. :?
who knows???

You can calculate the rolling diameter of the wheel & tyre as follows...

The three dimensions on the tyre are the tread width in mm, aspect ratio ie the height of the sidewall as a proportion of the tread width, and the diameter of the rim in inches. Don't ask me why they mix metric and imperial...

So for the standard wheel and tyre ie 215/45/17 the overall rolliing diameter is

(17*25.4) + (2*0.45*215) = 431.8 + 193.5 = 625.3mm

if you're using 215/40/17s then the diameter is

(17*25.4) + (2*0.4*215) = 431.8 + 172 = 603.8mm

603.8/625.3 = 0.965 ie the overall rolling diameter is about 3.5% less, so the speedo will over-read by about this amount (you're actually going slower than the speedo reading)

If you go for a larger rim you just select a lower profile tyre (ie smaller aspect ratio) to compensate, ie the smaller sidewall height compensates for the larger rim diameter. HTH.