Gentlemen! I purchased my first model A last year. I don't know a great deal about the car but am enjoying the learning process. I flooded the engine recently after it sat for weeks and I believe I left the fuel line opened. The information I found on the site was invaluable!! I like to run the tire pressure a bit elevated in my "modern" cars. I would like some feedback on tire pressure for Firestone tires 5.60-15 for front tires and rear tires are 7.50-16 I thank you in advance for any input. What tire pressures do you recommend and why?
Check on the side wall of the tire it will show you the max air pressure Are you running tubes? Higher pressures will keep the tubes from sliding in the tire. I’m running 6.00R16 and 7.00R16 being a radial tire I usually run them at 35 psi I’m testing 40 psi at the moment with no issues not sure about bias ply tires
Back in the early 70's when I was working in a Firestone store in Texas we normally aired bias tires up to 26 lbs unless the rig needed a higher pressure. Still it isn't about looks it is about tire contact on the road and ride comfort. 40 lbs is going to have the weight of the car riding on the center two inches of a 600 tire while 24 would have it riding on on the outer edges. That 40 lbs of air "to make them look good" reminds me of old farts in the early 70's who bought new cars that had radials on them and then came into that Firestone that I worked in bitching about "those damned rough riding Firestone radialtires" Check the pressure and some of them had 65 or more lbs of air in the tire because they didn't like the looks of the sidewalls with the correct pressure. Then they would gripe and whine when you set the pressure correct because they didn't like the look.
Tons of advise from hambers over the years. This is a list of posts regarding tire pressures. https://www.google.com/search?q=tir...QQwLjIzmAEAoAEBsAEY&sclient=mobile-gws-wiz-hp
Easiest answer is to draw a line of chalk across the tire tread. Roll the car forward on a flat surface and check the line of chalk on the tread. It should be an even wear across the tire. More worn off in the center, reduce tire pressure. More worn on the sides, increase pressure. If a tire is not riding evenly on a flat surface it will be even worse on an irregular surface.
Radials like a higher pressure, as well as it not affecting tread wear nearly as much with a bias ply. With bias ply tires you adjust pressure to get the best compromise between ride quality and tread wear. In a non-stock application it can be a bit of trial and error to arrive at what works best. AS @Mr48chev says, 26 psi is a decent starting point in most cases. For the smaller fronts, somewhere in the 26 to 30 psi range will work, the larger rears can use less, maybe as low as 20 psi.
Thank you! Great information and looks like I will spend some tome tomorrow playing tire pressures! Stuck at work today
Most folks run em too high in these lighter cars. On my Touring with a W motor I ran about 23# front with a 5.10 tire and 28# rear with stiffer cheater slicks
I run 8.20 tires and a heavier car and got around 24 - 25 psi, these tires runs alot better with lower pressure than radials, they get less sensitive to road conditions and also gives better comfort. Best if to start around 23 - 28psi and keep an eye so the wearing gets even, many cars with bias tires wear them uneven because of to high pressure
Also for clasic cars, the laws of nature count. End 2007 this "pigheaded Dutch selfdeclared tyrepressure specialist" got hold of the official european formula for tyrepressure for radial tyres, and went running with it. For diagonal tyres the formula was introduced in 1928, and adapted for radial tyres in the 1970ties. For radial tyres main goal is to give the tire a deflection that wont overheat any part of tire material when driving the speed constantly, for wich deflection is determined. For diagonal tyres a bit different, speed was not such an issue in those days. More to get total contact over the total width, so no centrewear or sidewear. To keep my already to long post short, its all about load on tyre, and maximum speed you use, and wont go over for even a minute, for radial tyres. Read back tires, so will go on using tires instead of tyres. If tires are radial, I can make a pressure/axleloadcapacity list with maximum reserve, but still acceptable comfort and gripp. Then need next from tires. 1. Maximum load or loadindex 2. Kind of tire to determine the maxloadpressure 3. speedcode, can be lower then Q (160kmph/99mph max) for classic tires. Then you " ONLY" have to determine the axleloads acurately in your use, an search them back in my made list for the needed cold pressure. For diagonal tires, I can also make a list with use of the old formula.
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