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MG MGB GT V8 Factory Originals Technical - Tyre c hoice - advice please!

I need to change two tyres on the rear of my '74 factory GT. With special offers from so many tyre depots it seems better to change all four. The problem is that the car is set up so nicely now that
I wouldn't want to change it too radically although I would maybe be tempted by a lower profile than the standard (I understand that I could go to 195 from 175
with a profile of about 60). If I go too radical I could make the steering too heavy and put the gearing out but I don't understand the relationship between width and the profile and how this relates to the gearing of the car. There won't be any track days or Grand Prix starts but there have always been plenty of spriited 'A' road driving (without speed cameras) and 'B' road driving. For info the car is set up with
a Spax adjustable tele conversion (set on 4 all round)
and has PH handling kit front and rear. The handling is not quite neutral but tends to the understeer when
pushed, which is the way I like to use the power.
I would be very appreciative of any advice - thanks
Martin

Martin,

I use 195x60x15 Goodyear Eagle F1.

With 195's you will need to be careful with LHR clearance. You may need to roll or cut lip. Best bet is to try before you buy and if in my area you are welcome to try my spare.

Paul
Paul

Martin,

I use Vredestein Protrac 2 185x70x14. 14" because the standard wheels are 14" and upgrading to 15" would cost at least 4x75 pounds, which I think is expensive. Also the 70 (means that the height of the tire-wall is 70% of its width) is nice and gives some comfort. Running on 2 bars or higher seems best for cars like ours.
185 width will fit without any clearance problems. Possible rolling back of lip could cause cracks in the paint and is potential rust area.
The previous owner fitted Goodyear Eagle, but it was not to my liking. Bit hard. Bridgestone also makes some nice tires.

Frank
Frank de Groot

Martin,
You queried "the relationship between width and the profile and how this relates to the gearing of the car". I don't know what size you have at the moment, but calculating this is quite easy. "Standard" tyres (ie those that don't quote a profile...of 70, 60, 50 or whatever) have a profile of 80. For example....
165-14 would give an overall diameter of 14" + 2(165mm x 80%)= 619.6mm
195/60-15 would give 15" + 2(195mm x 60%)= 615mm
There is clearly a direct relationship between tyre diameter and gearing.
Pete
Pete Green

Have you tried the Tyre Wheel Calculator on http://gs.tolan-hoechst.com/

Very useful!!
Stuart Robson

I have just driven to the arctic circle and back 1900 miles in 5 days on 195's and they were fine.
K Herbert

Thanks for all that to all of you. Very useful. Thanks offer of spare Paul but I'm on standard 14" alloy/steel factory wheels. Will check out that calculator Stuart. Probably stay safe and go to a 185X70X14

Thanks to all - Martin
Martin

This thread was discussed between 09/06/2002 and 10/06/2002

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