What tyre pressures are suggested today for an MGV8?


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Posted: 301210
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Although much has been written about tyres on the V8BB, I haven't seen anything about tyre pressures used by other members. This was how Julian Holmes began his message on the V8BB noting the MGBGTV8 Driver's Handbook (AKD 8423) states the following pressures on page 68 under General Data:
Normal conditions 21(F) - 25 (R)
Gross weight 26 (F) - 32 (R)
But Julian found these pressures surprisingly low and said "I would be interested in finding out what tyre pressures members are using on their V8s."
Difficulty in finding authoritative advice on tyre pressures for the V8
Victor Smith notes his experience with his current tyres.
As tyre technology has moved on a great deal since the less than impressive Grand Prix radial tyres originally fitted to the V8 at the Factory in 1973-76, it is proving very difficult these days to find authoritative information of the pressures for the modern tyres in sizes which fit the MGBGTV8. I have Continental Contact Eco 175/80 R14 88H on my MGBGTV8, which I have to say are very good in terms of comfort, ride and handling plus wet and dry grip. Experimenting with pressures I have found 22 (F) and 26 (R) certainly gave greater comfort and less thump from drain covers and bumps in the road, but have found the tyres at those pressures do squirm to some extent on corners. Raising them to 26 (F) and 30 (R) has given a more positive feel, good handling but a noticeable reduction in ride comfort.

When you try and find advice on suitable tyre pressures for modern tyres using the websites of tyre manufacturers and suppliers you find they offer only general advice about maintaining the correct tyre pressures. They avoid any indication of suitable pressures for their tyres and simply suggest you "need to consult the vehicle manufacturer's handbook"! That's fine for cars built in recent years but for a classic car like the MGBGTV8 the handbook was first published over 35 years ago!

So I contacted a leading MG specialist, Ron Gammons at Brown & Gammons in Baldock who has a MGBGTV8, for his views on the pressures he feels are appropriate for a modern tyre in the original size and profile on an MGBGTV8.

What tyre pressures are suggested today for an MGBGTV8?
Ron Gammons sets out his views and suggested tyre pressures.
Inevitably ride comfort and tyre grip are different things. The softer the tyre the softer the ride, the harder the tyre the less distortion of the tyre and tread rubber and therefore the better the grip. However by having the tyre too hard you reduce the area of the contact patch and then too much pressure is not a good thing. Tyre pressures are a subjective issue, everybody has different ideas but the following are my personal views.

Understeer is safer rather than oversteer - you have to be seriously quick to handle an oversteering car. But too much understeer can be almost as bad.
However bearing in mind that the MGB or V8 generally understeers, I feel that to have the front pressure at 21 is far too low. That will undoubtedly allow the tyre to squirm around and literally lose grip because it's rolled away. Therefore a higher pressure at the front is definitely required. Personally I tend to run the fronts higher than the rear, trying to dial out some of the understeer. So my preference, depending on tyre and load, is normally say 30 (F) and 28 (R) but if really loaded or driving hard, at least 30 rear as well. I would agree that you sacrifice a little by way of ride comfort but I rate living by driving safely as more important! You could go to say 28 front and 26 rear but the point is that to dial out understeer you have to increase the pressure on the front tyres compared with those at the rear.

By the way, as another way of trying to limit the understeer, I also only go to a 3/4" front anti roll bar since a stiffer bar does induce understeer. For more normal road use a 11/16" is quite stiff enough. If you have one of the dreadful front suspension upgrade kits that used to be marketed some five or more years ago fitted to your V8 with a 1" bar, then take it off unless the car is only going to used in the dry for race use on a track. It's far too stiff for road use with varying climatic conditions!

What tyre pressures are suggested today for an RV8?
Ron Gammons sets out his views and suggested tyre pressures.
An RV8 has a much larger contact patch (the area of tyre tread in contact with the road surface) than an MGBGTV8 because it has larger tyres on wider wheels. With lower pressures the tyres squirm about and higher pressures help to reinforce the tyre walls. To maintain ride comfort you need soft tyres and to handle well they need to be firmer. Whilst the RV8 Owner's Handbook (AKM7144ENG) shows the pressures at 22 (F) and 24 (R) (Technical Data, page 124), personally I tend to run higher pressures at 28 (F) and 28 (R). But the standard dampers are so poor and often tired too, so you need to consider whether a routine replacement is due or better still an upgrade which can provide better handling and ride performance.
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