What Size Tyres

[Jon Bradbury]

Heck, we need a FAQ.. I must have asked this old chestnut before.

 

Anyway, what is the correct tyre fitting for the Arays wheels supplied by Robin Hood? What is the widest tyre? It would need to preserve the Sierra's speedo accuracy.

 

Thanks

 

JonB

[Guest Phil Slater]

Hi Jon

 

RH have said that 205/50 R15 can be fitted to their alloys and maintain the accuracy of the Sierra speedo. A good site to visit is:

 

www.chris-longhurst.com/carbibles/

 

On this site you will find amongst other things the "Tyre Bible" which explains all the theory and, if i remember correctly, a calculator for checking what effect various tyre options will have on the accuracy of your speedo reading.

 

Hope this helps.

 

Phil Slater

[Les Welsher]

Jon,

you can fit 205/50 15 or 195/55 15 tyres to keep your speedo pretty acurate.

I fitted 195/50 15 because this size of tyre is cheaper, when my speedo reads 70 MPH I am actually doing about 2 1/2 MPH slower, but I can live with that.

This is ok for SVA, as the car can be going slower than the speedo reading but not faster.

 

Les.

[Guest Stuart Ainslie]

I have 205/50 15's on the Arays wheels - they look good but area bit too wide for the cycle wings and had to fit oversize rear arches to cover the tyres.

 

Stuart

[Jon Bradbury]

How about 195s on the front and 205s on the rear?

 

Anyone tried that?

[Guest Tim Norman]

I would think 205's would be too wide, reducing the grip. I actually went down from 195 to 185's all round and the car handling was transformed

 

Cheers

Bobsmate

[Guest jwaterman]

I Fitted toyo proxes ts1 195/55/15 all around on mine. they look the mutts nuts. They only cost me £42 per tyre off the internet. When the car was being tested for the speedo accuracy, the SVA man said that my speedo was very accurate, on 30, 40, 50, and 60 it was spot on, at 70 is was doing 68 1/2 so not bad me thinks!!!

 

john

[geoff shep]

Tyre size calculator

 

Try this handy calculator - compare donor wheels vs supplied ones - you can save the page and use it offline too.

 

Tyre Size Calculator

[Guest Wallace]

Where has anyone got any cheap tyres from on the internet im looking for some 195 55 R15, any ideas?

[Guest TerryBarry]

You could try

www.mytyres.net or .co.uk

or

www.topgear.co.uk

 

195.50R15's are generally cheaper than 195.55.R15's

 

The 50's have a slightly smaller rolling radius than the 55's but this should not present a problem for SVA since the speedo will read 3% high - this is not considered to be a sin

 

Terry

[Guest Wallace]

Has anyone fitted 195 50 R15 on the robin hood alloy wheels and passed there SVA with these, these have a 577 running diameter which seems way out compared with the recomended tyres 205 50 R15 (running diameter of 587mm).

[Mitch]

Hi All

Right if you go to the old RHOCAR website. On the links page goto the tyre bible

This will give you the difference in the speedo for the differance in the tyres.

its much the same as the above link but tells you the speed diferance for the tyres you pick from the standard doner tyres

HTH

Mitch

[Guest j0ngreen]

Hi all,

 

 

My donor appears to have had 13" wheels and I have 14" alloy wheels which I believe were supplied with the kit (They look like Fiesta Turbo Wheels or at least have Ford on them)

 

How accurate do you have to be with the tyre calculator listed earlier in the posts? And is it best to have the percentage in the negative?

 

 

 

Regards

 

 

Jonathan

[Guest gordon_macnab]

For SVA there's quite a high percentage of error that can be on your speedo and still pass as long as it is on the high side ( reading 80 when actually doing 70 ), but if the speedo reads low by any ammount its a fail so don,t fit larger wheels that the donor had.

 

To work out the overall rolling diameter just add the wheel size 13"/14"/15" etc (x25.4 to get into mm) and then add on twice the tyre side wall height. The tyre height is a percentage of the tyre width 195 x 50 = side wall height of 50% of width 195

 

Gordon

[Les Welsher]

Jonathan,

Try HERE and go to calculators

If you use the tyre diameter calculator at the bottom of the page to work out the difference in diameters then you can use these diameters in the speed calculator at the top of the page to find the difference in MPH.

 

eg. at 70 mph on 185/65/14 will read

68.812 mph on 205/50/15 and

67.640 mph on 195/50/15

 

 

Les