wheels affect speedo?

[kennyboy]

I want to replace my standard 993 17" wheels with some 18" RS items and perhaps at the same time change the suspension so it sits a little lower.

I'm concerned that the bigger diameter wheels will make the speedo read incorrectly.....can anyone give some advice plus other stuff I should be aware of when doing this.

Also if anyone can recommend the best widths for 18" wheels that would be good.

Cheers

Kenny

 

[bones]

Can't advise on wheel widths Kenny, someone else will but the bigger rims may affect the speedo . What you need to measure is the outside diameter of the wheel including the tyre on the 17" rims and then compare that to the overall diameter on the 18" rims. If the new tyre have a substantially lower profile then the overall width may not be too badly affected and you will hardly notice any difference. If there is a large difference or you are very anal (just jokin') then measure the outside diameter of the new set up (the rolling width) and send the measurements with the clock to one of the clock repair /adjustment companies in the motoring press.

 

[Elliot Davies]

Play around with this site Kenny

http://www.miatanet.com/garage/tirecalc.html

 

[Elliot Davies]

and here too

http://www.1010tires.com/tiresizecalculator.asp

 

[968er]

If you have a Road Angel or something similar which shows speed via GPS, or can borrow a friends this will give an accurate readout of your speed. Your speedo can be as much as 10% out on the low side e.g speedo 70, actual speed 63.

William

 

[kennyboy]

Thanks guys - everything I need there before I make the purchase.

Surprised Porsche made the RS rims heavier than the rest of the wheels when the RS is all about weight saving?!

They do look great though don't they - I only know of carnewal who stock them, any others in UK?