Running larger Diameter rear tyres?

[Guest Tubbygit]

Here's the basic question:

 

What would the effects be of running an N/A Supra for normal road driving with rear tyres that are a larger overall diameter than the fronts?

 

Advice needed please, however please bear in mind the following:

- I'm trying to save money here, so telling me to just go and buy a full set of new tyres would not be all that helpful

- I have tried searching the forum and Google

- I have checked the Wheel / Tyre Fitment guide spreadsheet

- I have no intention of changing wheels again (I like the set I've got)

- I am aware that larger Diameter tyres will effect the accuracy of the speedo

 

 

Here's the background / details :

 

I've got an N/A 5 speed manual 1995 Supra. As far as I know it has standard j-spec suspension (it does have OEM skirts and spats and a front splitter).

I drive it fairly hard, but I'm not a total maniac and I have no intention of ever taking it on a track.

 

Having recently changed wheels I have found that I need to change to smaller diameter and width front tyres as the ones that came with my new wheels rub at full lock (the spreadsheet says that they should rub too)

Also they seem to have made the steering heavier / slower (I assume that this is because they are wider than the fronts that were on the car).

 

The Wheels are all 18 8.5j (offset: 35 - they fit & fill the arches perfectly) with 245 45 tyres on them front and back.

 

I would like to keep the rear tyres as they are nice bridgestones with plenty of tread left on them. They do seem to fill the arches to the maximum but I don't think that they will rub (although I have not tried loading the back of the car down with heavy stuff to double check yet).

The tyre size spreadsheet does say that they are "too tall"

 

I plan to change the Front Tyres to 235 / 40 or 225 / 40

(I'm thinking that the 235 / 35 & 225 / 35 sizes will be are too small)

Recommendations please, bearing in mind that the rears will be 245 / 45 (or if I have to change them to they will be 245 / 40 or maybe 255 / 35)

 

So what I'm asking is:

 

1: Do I need to change the Rear Tyres?

 

2: What size front Tyres should I go for?

[merckx]

In my opinion.

 

1: Do I need to change the Rear Tyres?

 

No.

 

2: What size front Tyres should I go for?

 

235/40 18