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MG MGA - Tyre Pressures

When new MG suggested different tyre pressures for Roadspeed & "standard" tyres.

In the case of "standard" tyres the recommended front tyre pressures were:-

Normal 17 psi
Full load 21 psi
Sustained high speed driving 23 psi

Rear tyres were recommended to be 3 psi over front tyre pressures.

In the case of Roadspeed tyres the recommended front tyre pressures were:-

Normal 18 psi
Full load 22 psi
Sustained high speed driving 24 psi

Rear tyres were recommended to be 2 psi over front tyre pressures.

I’m using Goodyear GT80 165HR15 tyres, and find that on modern roads 24 psi at the front is about right - BUT I am running the rears at 22 psi unless both the boot (trunk) and the luggage rack are fully loaded; in which case I up this to 24 psi.

I should add my 1600 Mk I Roadster is in excellent “unmodified” condition, but does have a front anti-roll bar, and thicker oil in the dampers.

I am trying to achieve easily induced throttle oversteer, a reasonable ride, and reasonably sharp turn in.

Can anyone else with a similar set-up say what tyre pressures they are using, and to hat effect?
Nigel Steward

Tire pressure is a very individual thing that varies by driver preferece, suspension setup, use tire, size, type and tread. The original pressures given in the book were for the old bias ply tires and normal road driving--however--you needed a bit less pressure in the old style tires to get a decent bit of road grip....and then they wore quickly. The best thing to do is to experiment with different pressures until you find the combo that feels right to you. I run 23 front and 25 rear with Kumho 165's. However, since I have 48 spoke wires, I seldom, if ever, drive aggressively. It gives me a nice ride and good control. You'll just have to play with it a bit, as someone elses "perfect" my not feel at all right to you. Be carefull using thicker oil in the dampers--I ruined a front shock on the old '64 I once owned by doing that...it was OK as long as the roads were smooth, but when I had to drive a patch of rough stuff--it stripped out the splines on the lever. You're much better off to buy a new set of valves that will give you more damping.
R. L Carleen

Nigel
If you are running radials 24psi front - 27psi rear. This keeps the differential at 3. The low original pressures were for the old crossplys, then fitted as standard, with their stiffer walls.
Pete
Pete Tipping

The MG car Club suggested to me 26 all round, which seems to be OK
Nigel Munford

I'm running BF Goodrich Silvertown Radials and the manufacturer is emphatic that they must be run at 35 psi no matter what the car manufacturer says. They work well at that pressure.
David Breneman

I typically run 30 PSI all around, sometimes a little more sometimes a little less. 2-3 PSI more in the rear than the front seems to be about right.

Different tires will function best at different pressures as well. One set of tires I use has fairly weak sidewalls compared to another tire on a different car. I run 32/34 to stiffen the handling a bit, where on the other car I run 30/30, sometimes 28/30.

Just food for thought....
Steve Simmons

<<I am trying to achieve easily induced throttle oversteer, a reasonable ride, and reasonably sharp turn in.>>
Naturally tyre pressures are important, but every tyre requires different pressures to achieve same results. More so though is the way the suspension is set up and especially the front tracking.
To achieve good front end grip and turn in, (which is what you desire) then setting the front track at zero or even 1/2 degree TOE OUT will greatly improve TURN IN. At these settings the car become very responsive and manufacturers stay away from these settings to ensure the car UNDERSTEERS which is better for joe public in times of problems.
Bob (robert)

Why isn't it best to use the recommended pressure on teh side of the tires (tyres)?
Jack

I would imagine the recommended pressure is for an average vehicle. MGAs are far lighter than the average vehicle.
Steve Simmons

Nigel (Munford)
The 24F & 27R pressures were recommended to me by the MGOC and seem OK. I am sure this is around what I used to run my Cinturatos at back in '64 to'65.
Interesting the MGCC thought different...
Not sure about the racing bit though Nigel (Steward)- like to look after mine.
Pete
Pete Tipping

The pressure value moulded into the side wall of the tyre by the manufacturer is the maximum recommended pressure. As noted in all above, tyre pressure depends upon the tyre and type of driving.
I think Barney Gaylord (www.mgaguru.com) has a technical article on determining the ideal pressures for each situation.
I run 28 lb/sq in on all four Michelin 165-15 XAS with tubes on disc wheels and that give me just the amount of oversteer I want, when pushed.
Cheers! Fraser
Fraser Cooper

Reminds me of the time I had new tires put on a rear engine VW. The guy was adamant about knowing what pressure to put into tires.. He had WAY too much in the front, making it steer and ride like a real POS. So play around with the pressure, you'll find a combination that's right for you. Playing with the toe in is fun, too. Who cares what a gauge says, they probably all read different anyway! Just use the same one each time..or maybe try different guages until you find one that reads right for your car..hehe.
Tom

This thread was discussed between 10/05/2005 and 22/05/2005

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