16" Spider vs 18" Spider rolling diameter

[T40ORA]

Anyone know if the RD of the two, with recommended tyre sizes, is equivalent? Or would they be different enough to cause the geo to have to be changed when swapping between them.

Thinking of some 16s for track days....

[RichardD]

Assuming you know the tyre sizes, put some numbers in here :-

http://www.1010tires.com/Tools/Tire-Size-Calculato...

[T40ORA]

RichardD said:

Assuming you know the tyre sizes, put some numbers in here :-

http://www.1010tires.com/Tools/Tire-Size-Calculato...

Thanks. New question now - +2.64% variance front, -2.17% variance rear, so how would the geo me affected?

[7erbera]

T40ORA said:

Thanks. New question now - +2.64% variance front, -2.17% variance rear, so how would the geo me affected?

I can really help with the question, aside from saying a change will mean different behaviour, just how much probably better to ask one of the TVR performance garages out there. Or choose a tire size that closer matches the rolling diameter.


Just wanted to post that I am pretty sure most TVRs have speed detection on the rear axle, so your speedo will be out if tire size changes - MOT considerations and all that...

[T40ORA]

7erbera said:

I can really help with the question, aside from saying a change will mean different behaviour, just how much probably better to ask one of the TVR performance garages out there. Or choose a tire size that closer matches the rolling diameter.


Just wanted to post that I am pretty sure most TVRs have speed detection on the rear axle, so your speedo will be out if tire size changes - MOT considerations and all that...

They do have speed detection I think - but as the Tamora was specified with 16" rims I think that will be OK. If I am right, the slightly smaller diameter will show me travelling faster than with 18" rims, so I will be in the safe zone - I think!

And the handling will be different - most agree that it will be better, again as the Tamora was designed around 16" rims.

This a more general question, as I really want to know what tolerance there is in geo set up. I.e. will a change of <3% make a difference.

But you are right; asking an expert is the best route....

[s6boy]

T40ORA said:

And the handling will be different - most agree that it will be better, again as the Tamora was designed around 16" rims.

Was it? I know the Tuscan was but thought by the time they got to the other T cars the 18" was diameter of choice as so many Tuscan owners had upgraded as they looked better.

[T40ORA]

s6boy said:

Was it? I know the Tuscan was but thought by the time they got to the other T cars the 18" was diameter of choice as so many Tuscan owners had upgraded as they looked better.

The flyers that I have from when I bought mine new in 2006 show 16" rims with 225/50 front and rear.

Just heard from a TVR mechanic that the different wheels should run nicely on the same geo settings, which is good....

[RichB]

7erbera said:

I can really help with the question...

Can or can't