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MG TD TF 1500 - TD Radial Tyre Pressures

I thought there would be plenty in the archive on this but could only find mention of 25 psi in one thread, which seems really low. I run 36 in my daily drive (1991 Cressida) and have had 40 recommended for it, though I don't go that high. I'm about to drop the TD off its stands so I can move her about. I understand under inflated tyres wear on the edges and overinflated in the centre, all other things being equal. I'm also aware that the suspension geometry was set up ex factory for cross ply tyres and I'm using radials with tubes. I assume the vehicle weight also figures in the perfect psi figure. Personal preference aside, is there a definitive answer? Cheers
Peter TD 5801
P Hehir


Peter,

There was a prior discussion regarding tire pressures quite some time ago. Here is what I copied from that discussion.

"Here's the advice that I received from Lawrie Alexander, and that I follow:

I've always found that, with bias ply tires of the original size, 22lbs in
front and 24lbs in the rear gave the best combination of wear, handling and
ride.

With radial tires of the size you are using, I recommend 24lbs in
front, 26lbs in the rear for general use. Add 4 lbs at each end if you are
going on a long, fast drive, and increase the differential from front to
rear to 4lbs if you are carrying a suitcase on a luggage rack (esp. the
low-mount rack.)"

I am using Vredestein Classic radial tires and I find the 24/26 pressure somewhat hard so I use a 22/24 combination.

Regards,
Jim
James Neel

I run 24F/26R and add 2 psi when doing Interstate driving. These were recommended to me by Lawrie Alexander a bunch of years ago. My 2007 Ford Focus Wagon is spec'd at 35 psi all around and my 2015 Prius is also at 35 psi. But they are different wheels and suspensions. This topic has been covered on the list. Try searching "tire pressure" in the Archives. Bud
Bud Krueger

Thanks Jim and Bud. I searched "tyre" instead of "tire", which explains the lack of info. Still seems incredibly low. Maybe the rationale is explained in the "tyre" threads. I'll check them out. Cheers
Peter TD 5801
P Hehir

Hi Peter,

When I got my last set of Michelins, there happened to be a company rep visiting the tyre shop, we discussed this and he recommended 22 to 24psi. What I like to do is fine a dusty drive way and drive slowly to let tyres pick up dust, then look at contact patch, this gives a good indication if really over or under inflated.

Regards
Bernie
B W Wood

OR
Get yourself a cheapy point and shoot temp gauge and go for a drive and get it up to temp and shoot your tyres and adjust pressure to get an even temp accross the tyre
Important to have it up to temp to get a correct reading
willy
William Revit

Peter,I tried 26 pound but now run about 22lb front and back on radials, I started on good rag tires for about 10 miles but could not get radials fitted quick enough
Gordon W
Gordon Wright

Checked out the 8 threads in the archive and discovered there is no consensus. Figures ranged from 22 to 35 psi. It was suggested that lower pressures produce a softer ride but heavier handling at low speeds; high pressures give better handling but transfer more vibration, a less comfortable ride and may result in greater tyre wear as well as a tendency to bounce all over the road; if planning a long trip then increase the pressures; rear has a couple more psi than the front. So... Still none the wiser. Cheers
Peter TD 5801
P Hehir

I have Firestone radials on the TF and found that 28 lbs in the front and 30 in the rear works best for me. Long trips without a passenger I drop the rears to 28 lbs. Any lower on the fronts give heavy steering due to the heavy grip of the tires. I think different brands require different pressures. PJ
PJ Jennings

There is no definitive answer to this without doing extensive testing or years of experience from racing, road use, etc. I think its better and safer to use a higher pressure rather than low and chose to use 26 / 28 psi with Blockley radial tyres. The make of tyre and road conditions might make a couple of psi difference either way.
Dave H
Dave Hill

To develop this thread further should small plastic collars be fitted to the holes in the wheel where the tube valves exit? I am concerned that a tube could rotate slightly and the edge of the metal would shear off the valve.

Jan T
J Targosz

Jan T,

If you had an SBC (small block chevy) engine in your TD then I might be concerned with spinning the wheels inside the tires. I don't think that under normal driving conditions an XPAG or EG would produce sufficient torque to do the same on a properly mounted tire & wheel. Unless of course you are hillclimbing and pop the clutch at 5,000 rpm. Heh, Heh.

Jim
James Neel

Yes, Jan, IMHO it is a good idea. Jim, if you get the chance take look at the valve stem openings in a number of wheels. You'll find a tendency to rust around the hole. This can eventually cut through the stem. When the wheel comes to rest with the valve opening at the bottom there is a bit of a deflection that puts pressure on the stem. I've had first-hand experience with this. The inserts are very inexpensive. Bud
Bud Krueger

26-28 is what I was told, I run 28, it works.

Peter
P G Gilvarry

Bud,

Thanks for that advice, never heard about the rust situation before.

Jim
James Neel

This thread was discussed between 02/11/2018 and 05/11/2018

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