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MG MGB Technical - V8 Tyre Choice

The V8 CB B is getting closer to the MOT.
The tyres have been on the car for the past 30 years while it was in storage, so I am going to change them before it goes for mot. It currently has 175 14 88H on standard V8 chrome alloy wheels, but I would like to change to either 175 70 14 or 185 70 14.
Does anyone have any experience with any of these sizes? or has anyone suggest an alternative size.
My RB 1800 has 5.5j minilite alloy wheels and runs on 185 70 14 with no problems.


a goldup

Hi,

I run Kuhmo XR11 steel radials 185/75R14 on my roadster. These were recommended by my tyre supplier. For what it's worth the speedo seems to be accurate with these.

When I bought the car it had brand new Dunlops on it, still with the little injection pips around the tread. Unfortunately they were so old that there were cracks in the rubber at the bottom of the tread.

Herb

Herb Adler

Hello,

Sumitomo HTR 200 they are speed rated H.

Cheers,

Jean G.
Jean Guy Catford

Although I do not own a v8, I recently reviewed all the current thoughts on tyres and sizes, check out the archives, I think someone posted relatice sizes and sections and their effect on total diameter which is important when considering whether speedo changes were called for. I cannot therefore recall but it seems one could go to a 15" wheel and a 65 section and still not upset the 24" total diameter critical figure. If you are using the full grunt of the V8, then I expect the more rubber you put to the tarmac the better! So a 185 I should think is a necessity, can you squeeze a bigger wheel, or perhaps you don't want to go down this road. Mike
J.M. Doust

Use a tyre size calculator to find out whether your choice will affect the speedo. Here's an example http://www.etyres.co.uk/tyre-size-calculator.htm

I have 6" wide 15" wheels on my V8 shod with 195/60 x 15 tyres. These are 3.3 percent smaller in diameter than a standard V8 tyre but since I have a programmable speedo it doesn't matter to me.
Mike Howlett

The height of the standard tyre (175/80R14) is 80% of 175mm = 140mm.

To get the same gearing you should aim for that height, if you fit lower tyres the accelleration should get better but with the V8 that shouldn't be the biggest worry?

a 185/70R14 is 129,5mm high
a 175/70R14 is 122,5mm high
a 195/70R14 is 136,5mm high

The 175/80R14 is a standard tyre for the "economy" VW Golf IV, therefore the choice in A-brands should be very good.

I run my MGB on standard 165/80R14 tyres and if it was my MGB V8 I'd go for a standard look with either Michelin or Continental tyres in 175/80HR14.

How wide are the standard V8 wheels? (5"?). If you can fit the 195/70R14 tyres without rubbing that would be the best "performance option".
Willem vd Veer

V8 wheels are 5J. Tyres were originally 175/80 14". 185/80 gives a 2.3% increase in rolling radius making the speedo read lower for a given speed than before. 185/70 will read 3.6% higher than before. 195/70 will read 1.3% lower than before. Remember the speedo can be anything up to 10% under reading, so on average you could go to 5% lower tyre-wise and still not be actually running faster than the speedo shows. 195 tyres fit the arches well enough, but are pretty fat for spare wheel storage if you want to fasten the cover.
PaulH Solihull

You are right as usual Paul, the 195 tyre won't go under the load floor and allow it to close. So I carry a standard wheel and tyre as an emergency spare. A bit like a modern space saver, purely for get-you-home duty. My pal Geoff, who has 205 tyres on his MGB, doesn't carry any spare. He regularly drives to France in the car, and has been as far as Greece. So far he has never needed a spare....
Mike Howlett

Hi
Have recently fitted 185 60 14 H Goodyear Excellence. I am very pleased with the better grip. The old tyres (over 20 years old)on mine were also full profile and although had lots of tread were lethal in the wet.

But be aware that fitting lower profile tyres does lower the car considerably. This can give grounding problems if the exhaust is low at the middle. 60 profile will be some 2" smaller diam.

I have checked the speedo using my Tom Tom sat nav and the speedo seems accurate now. But think it gave a high reading before.

Alan
Alan Stevens

I have gone for the 185/70/R14 88T Continental as ther are readily available and are a reasonable price.
Will keep you posted on how they perform and what the change to the ride height is.
The continental tyres where recommended to me as they are a softer compound and should soften the ride as the V8 has Spax fitted both front and rear. I have been warned they may not last as some other tyres.
a goldup

It's better for the tyre to be worn out due to lack of tread than to be dried out due to lack of use (loads of tread but cracked). You feel better about getting a new set!

Mike

I run my S/C B on 185/70 14 Yokohama A Drive, relatively cheap and are a good looking tyre...lots of grip too.
I K Jackson

AS an interesting aside. My father owned a TD in Venezuela, lovely little thing, wish we still had it! Anyway it was bought with what looked like new tyres, no wear on them at all. But as has been said, in the wet lethal! The rubber was hard and glazed, they were probably original! ( this was back in 55.) New tyres absolutely transformed the handling. Dad used to tinker with the relative pressures front and rear, and could 'drift' like the professionals all with standard engine. So yes, if you are running old tyres, that still look good, do not trust them! Mike
J.M. Doust

This thread was discussed between 18/01/2011 and 11/02/2011

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