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Lets get serious=tire pressure

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jlaird

jlaird

Great Pumpkin
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Ok I know what the good book says but I have 155/60 R 13.

What would be appropiate, not the 30 lbs I have in them?
 
Lower. Likely (purely a WAG!) I'd start with 20~22 front, 4 to 6 higher rear. Increase proportionately if you see rapid inside/outside edge wear, or feel it to be ploughing.
 
I would not go any lower than 25 on radials. Underinflation creates heat and that is what destroys a tire. I run 28 rear and 29 front. Our old cars came with bias ply tires which had a much heavier side wall and used lower pressure. You can watch for wear in the center if you think it is too high, but low pressure can be more dangerous. The majority of cars on the road today are running underinflated tires. Remember the Firestone-Explorer problems were caused by underinflation.
 
I'm taking GVW into account here as well, Steve. "underinflation" is as much a function of load as it is pressure. The contact patch needs to be uniform. 25# may be closer to a proper "lowest" for the Frogeye but only if it keeps the tread contact even across the 'patch'.

I run 28 front, 32 rear in the MGB; 18 front 22 rear(!) in the Elan; 24 front, 28 rear in the +2. Never had a bead come away even flogging thru auto-X courses. Tires wear evenly and not had a catastrophic tire failure yet. All radials, all the time. Last bias-ply tires I had were in 1969. Had 'em about two weeks before going to a set of Semperits on my first B.

OTOH, I've had belt separation with one rear on the Benz... running it at 35#. <shrug> Michelins.
 
My midget is light enough that the tires support it well at about 25-26 psi and they are wearing fairly well. I've run them as low as 23psi, but it caused some understeer that I couldn't get used to. However, the ride was much smoother.
 
I have always used 24/26 psi and found that to provide good, even wear and crisp handling!
 
Think I might experiment with the tire pressures.
 
Love it when I ask a question an it becomes an all out fest.
 
It all depends on tire size and model, car weight, and personal preference. Obviously, there are hazards to over inflating and underinflating... but I think you have a wide range to experiment with since the car is light.
 
I run what the tire manufacture puts as the rating on the side of the tire. Keep in mind that the bias ply tires that came on these cars had 4ply sidewalls and the raidials you buy today have 2ply sidewalls. My last set of tires were cheap tires and I put fifty thousand miles on them. I hope to get well over that with the Michelin's that I have on it now.

just my 2 cents
Anthony
 
Since I just got my car, I also just ordered a set of four Kumho Power Star 758 tires in 155/80/13 from tirerack.com.

At 26.00 a pop, they're the cheapest tires I've ever purchased, and oddly enough, perform better on the Sprite than any other tires on my other cars /bcforum/images/%%GRAEMLIN_URL%%/wink.gif

The place I had them put on inflated the durned things to 45psi. Needless to say, my car was getting hoppy up front with it's nearly dead shock arms and these rock solid tires.

I have the fronts at 30psi and the rears at 35psi right now, but they could probably stand to lose a little bit of air.
 
45 PSI?!?! Whoa. The Elan dances around like a spider on a hot griddle with 25~30!!!
 
I stand corrected. The Sprite has a weight bias front to rear. Higher pressure in the rear tires than the front will actually help reduce understeer by giving the fronts more contact patch than the rear. My bad. However, the actual contact patch for our cars is pretty small compared to heavier MGBs and such.
 
Talk about cheap! When the Memorial Day tire sales come along and they advertise tires as low as $9.99, guess what, that is what fits the BE!! They are radials, good for 45,000 miles and handle just fine!! Stems, mounting and balancing cost more than the tires!!! Still under $100 for new skins!
 
I have bought those before ("$99.00 for all four") and after a month of taking it back for them to say that everything was fine (it was out of ??? & bumpy as heck!!) I put on 4 Michelines and it was smooth as glass! Just be a bit careful.
Bill
 
middleagecrazy said:
I run what the tire manufacture puts as the rating on the side of the tire. Anthony
Click to expand...

Anthony, that rating is the maximum allowable pressure at the highest GVW. Not a good choice for either ride, handling, or longevity.

With Michelin ZX, 155 80's on the '63, it likes 22 front, 24 rear.
The '72 is on Sumitomo 175 70's, and wants 24 front and 26 rear, but it's heavier than the '63.

Jack, I think I'd start with 22F, 24R on the Bugeye, and see how it feels. There are a few tricks you can use to optimize the inflation pressures, such as chalking the sidewalls, driving through some good corners, then checking the marks for evidence of rollover, checking temps across the face of the tread, etc.
Jeff
 
32/35 in the Spider. Thing weighs as much as a Hummer. /bcforum/images/%%GRAEMLIN_URL%%/jester.gif
 
24 26 is it for a start.

Great thread I think.
 
If you know someone who has a pyrometer you can set them up perfectly in an afternoon. Mislaid mine though (not that Baby Bertha is going anywhere for a while), must get another one. 26psi sounds about right, just put a few extra in if you are carrying a load.
 
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