Which size tyres for IVA
 

I'm a bit confused over what size tyre to fit. I'm using the sierra gearbox and speedo and I want to make sure that the speedo readings are within IVA spec.
The sierra original tyres were 185/65 R14 and I am looking at Toyo T1R's. The perfect match are 195/55 R15's at Approx £60 each whereas 195/50 15's are £36 each.
Will the cheaper ones be ok. I assume that the speedo will read less than actual.

Cheers

Peter

Gus's car went through IVA with 195/50/15 tyres, so go for the cheaper ones.

Cheers,

Thats was what I wanted to hear.

Peter

Hi Peter

As far as I know, 50 is the correct aspect ratio for a 15" Sierra wheel rim :)

This will ensure that the circumference of the wheel is correct for the Sierra's speedometer ;)

I have a set of Toyo TR1's for my own build & they are 195/50/15

Cheers Ronnie,

I used this website for comparison.

http://www.etyres.co.uk/tyre-size-calculator.htm

I was sure that a lot of people were using the 50 profile ok.

Peter

Hi Peter

I use this site for reference.

Alloywheels.com

That said, I notice in the Haynes manual that both 195/65/14 & 195/60/14 were fitted to various Sierra models as standard.

195/60/14 had a V rating

Hope I am not confusing the issue too much :o :o
Perhaps the tyres speed rating has a bearing on the aspect ratio of the tyre ?

forget t1r's fit r1r's they stick like poop to a blanket compared to the t1r's which i now consider to be rubbish after fitting r1r's. i would guestimate that i have about 40% more grip now with the r1r's

my car will be 2 years old in jan and i have already been through three sets of tyres. track days are fun :D

Cheers lads,

Are R1R's track use only ?

Peter

I,ve just done a tyre size comparison between

185 / 65 / 14 = total tyre diameter =596mm

195 / 50 / 15 = total tyre diameter =576mm

so does this mean the speedo will under read ? :confused:

cheers
andy

It might under read compared to the original tyres, but how far over did the original tyre combination over read?

You might actually be making the speedo more accurate to real life than the original.

Either way Gus's passed with 195/50/15 tyres so I would not wory about it.

HTH

Dave

r1r's are road legal track tyres :D

Good point Dave :)

I have fitted 15inch rims with 195/50/15,s tyres too so shouldn,t have a problem, :cool:

was just me trying to cover all concerns in prep for the IVA test :o

cheers
andy

Hi Peter,

If you're going for the standard sierra dash and speedo cable, non adjustable, i would stick with the tyres that we know pass with that setup, ie 195x50x15. I dont think we know exactly how accurate the sierra speedo is but i think they all tend to over read to some extent. If you fit slightly smaller tyres, 50 profile, then it may over read too much. After all you're allowed to over read by 10% but not under read at all so you only have + - 5% to play with.

Probably why the 195x50 tyres are cheaper.

Hope that helps....AndyH