tire preasure

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Leaford Burnett
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tire preasure

Post by Leaford Burnett » Wed May 20, 2020 2:46 pm

I mounted new 30 X 3 1/2 inch clincher tires on demountable non split rims. Somewhere on this forum it was said that tires should be inflated to 60 PSI

Could someone confirm this as when taken out on the road with that amount of pressure it seems to handle poorly, the front axle has had all pins and bushings replaced, bearings inspected and repacked, alignment, toe in and gather all seem per specs so don't think that's the problem, I never driven Model T before and not sure what to expect.

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Re: tire preasure

Post by RajoRacer » Wed May 20, 2020 3:14 pm

60 lbs. is the correct pressure for that size - some folks run up to 65 - 70 lbs. - I'm a 60 lb. guy !

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Re: tire preasure

Post by ChrisB » Wed May 20, 2020 3:15 pm

Clincher tires definitely need 60 PSI or the tire and tube will spin on the rim and rip the valve stem off.
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Re: tire preasure

Post by Piewagon » Wed May 20, 2020 4:04 pm

Could you be more specific with regard to " it seems to handle poorly" Is it wandering by itself or do you have excessive play in the steering. If the thing pulls to the right really hard as you pass a place that is selling ice cream - that is normal.

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Re: tire preasure

Post by Norman Kling » Wed May 20, 2020 4:21 pm

The T does not have power steering, so it might seem different from what you are used to.
Handling poorly can be many things. If the castor, camber, and toe in are set correctly, it should run straight ahead without pulling on the steering wheel. Sometimes the camber of the road can cause it to pull slightly in one direction, toward the lower side. You could also have some tight parts which would cause it to steer hard.

Other things which can cause problems are also a bent chassis. If it is bent the U joint could be off center which could cause the two axles to be out of alignment with each other. Try measuring diagonally between the same point on the front axle, such as end of the axle where the spindle bolt is bolted to a point on the opposite rear axle such as a bolt where the radius rod is bolted to the axle. The measurements should be the same in either direction.
This problem could cause the car to pull hard to one side.

If there seems to be looseness and play in the steering or shimmy of the wheels, you could have a loose connection anywhere in the mechanism. Typical trouble spots would be spindle arms to spindles, pitman arm to the steering column, loose gears or worn parts in the steering box. Most often can be loose ball joints at ends of the drag link and or the radius rod ball under the crankcase.

One more thing I can think of would be wrong length drag link. different year models had different lengths. When you are using the correct length for your car, the pitman arm should point straight down when the wheels point straight ahead.
Norm


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Leaford Burnett
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Re: tire preasure

Post by Leaford Burnett » Wed May 20, 2020 4:24 pm

John
maybe when I get the speedo you sold me installed it will ride better as of right now I've driven less than 6 miles on it and just not comfortable with it, thanks to all for confirming PSI


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Re: tire preasure

Post by Norman Kling » Wed May 20, 2020 4:27 pm

The T does not have power steering, so it might seem different from what you are used to.
Handling poorly can be many things. If the castor, camber, and toe in are set correctly, it should run straight ahead without pulling on the steering wheel. Sometimes the camber of the road can cause it to pull slightly in one direction, toward the lower side. You could also have some tight parts which would cause it to steer hard.

Other things which can cause problems are also a bent chassis. If it is bent the U joint could be off center which could cause the two axles to be out of alignment with each other. Try measuring diagonally between the same point on the front axle, such as end of the axle where the spindle bolt is bolted to a point on the opposite rear axle such as a bolt where the radius rod is bolted to the axle. The measurements should be the same in either direction.
This problem could cause the car to pull hard to one side.

If there seems to be looseness and play in the steering or shimmy of the wheels, you could have a loose connection anywhere in the mechanism. Typical trouble spots would be spindle arms to spindles, pitman arm to the steering column, loose gears or worn parts in the steering box. Most often can be loose ball joints at ends of the drag link and or the radius rod ball under the crankcase.

One more thing I can think of would be wrong length drag link. different year models had different lengths. When you are using the correct length for your car, the pitman arm should point straight down when the wheels point straight ahead.
Norm


Norman Kling
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Re: tire preasure

Post by Norman Kling » Wed May 20, 2020 4:29 pm

If the chassis sags in the center by the rear crankcase mounts, it could alter the castor which would also cause hard steering.
Norm


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Re: tire preasure

Post by Roz » Wed May 20, 2020 4:36 pm

You can also get your steering components too tight which will cause your car to wander all over the road and be difficult to drive.

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Re: tire preasure

Post by Mark Gregush » Wed May 20, 2020 6:51 pm

What Ros said. jack the front end up and see how much drag there is on the king pins. I once snug mine up a bit too much and when making a turn it wanted to stay turning. Other thing to check is toe in, if it is wrong steering will be wonky.
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Re: tire preasure

Post by Susanne » Wed May 20, 2020 8:15 pm

I was told decades ago that the formula was 20 PSI per inch of width... that puts me in the 60/70 PSI crowd, kind of like a bicycle tire... I did try running lower pressure (40-ish IIRC) because someone told me 60 was way too high... and it cost me the stems out of my tubes and a rim cut tire... Went back to 60 front, 70 rear, and no more problems...

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