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TR6 TR6 tire psi?

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Brighton Bob

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I am running 205 tires on my TR6, the 185's called for 20psi front and 24psi rear. I have been playing around with 28psi on the 205's. What say yee?

Brighton Bob
 
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"What say ye all?" I'm betting that every TR owner tweaks the psi to a comfy compromise between road grip, control while driving, and comfort. Comfort is probably the least important.
 
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Where did the 20/24 PSI spec come from? Most modern tires are designed to run around 30 PSI. I keep mine around 28-30, which seems to give the best feel. I don't do a lot of (ahem!) sporty driving, so I can't comment on that.
 
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Thanks for the responses. The 20/24psi came from the plate on the inside of the glove box door. I agree that's too low, when I had the 185's I would run 24-26psi all around. With the 205's 28psi all around. I read a article recently that said to Decrease psi when going to bigger tires. I bought my car new in '74 and back then we would run 30+ psi at autocrosses, chalking the tire edges and adding psi until we stopped rolling off the tread onto the side walls. But we would lower the psi for the drive home. I suppose too high psi might affect wet braking. Just the retired engineer in me coming out.
 
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The late engineer Randall Young ("TR3driver" on this forum) used to run 27 psi in the front and 31 psi in the rear, if I recall correctly, and that is what I use in my TR4 with front and rear anti-sway bars.
 
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My TR4A, back in the 1960s, specified 18 PSI, I believe, in the front for Michelin X tires. I remember that because it surprised me so much. So a factory spec of 20-24 doesn't surprise me a lot.

Of course, in those days, that was for cross-bias-ply tires, which are not used today. So I think Randall's 27-31 makes sense. One consistent trend, I see, is still fairly low (by today's standards) front-tire pressure.
 
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just a thought here, if the 20/24 figures came from a plate on the car itself, as those Triumph's recommendations for bias-ply (pre-radial) tires in the year the car was built? Bias-ply and radials used psi calculated very differently, as the two types of tires responded very differently to weight, speed, temperature, and maneuvering.

TM
 
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I have always run a couple more psi in the front than rear, theory being there is more weight in the front, decrease under steer. Like 30 psi front 28 rear, give or take a few pounds. I think the manufacturers, even back in the day, wanted to keep the cars biased towards under steer for safety and liability reasons, I could be wrong. Also, not so much on TR6s, but leaf sprung British sports cars tend to ride a little rough and hop around on bumps, the lower rear pressure helps compensate for this.
 
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This might be faulty thinking, but I run 28lb front and rear now. I have a IRS TR4A and the rear lever shocks have been uprated, and the rear spring is uprated and poly bushings also. So, I don't have the soft rear end that would have come from the factory, and my thinking was that I don't need to have a lower back pressure to compensate. Bruce
 
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I think the 20/24 psi for the Michelin X tires was to tame the oversteer. I bought the car new in 74 and the MIchelin X's would howl like Banshees when the car was pushed. But now with better tires, a little oversteer is more sporting. So the same all around is good. Thanks for the responses, I don't feel like 28 psi all around isn't over doing it. My BF Goodrich TA's will age out before they show any signs of over or under inflation wear.

Bob
 
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I usually run about 30PSI on 205/70-15 tires on stock rims. Keep in mind at that pressure or higher you will be really running on just the center of the tire. The optimal wheel size for a 205/70 is 6-6.5 inch wheels. Our TR6’s have 5.5-inch wheels so that in itself makes the tires run a little more just in the center of the tread, combined with higher pressure you will see most of the wear in the center of the tire. Again, if you drive your car like most of us the tires age out long before they wear out
 
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