Hot Rods Here we go Again!. Tire Pressure

I just put a pair of firestone F560, 165R/15 tires on my 32 roadster. Car has dropped axle, hairpins panhard bar,vega box. and a 57 Red Ram Hemi with 350TH. Put 35psi in the tires drove home and what a bear it was to handle. The steering control became horrible was a white knuckle ride home, was as if the box had extensive play. Dropped down to about 32psi seemed a little better but not much. Must drop more before I make the trip to Baltimore, but what is a safe tire pressure without creating more havoc.

 

I run 21 -22psi around town. 24 psi on long highway trips. Any higher and the ride knocks my teeth fillings outa my noggin.

In Eastern M***achusetts we have awful roads. State wont repair them 'till enough people get killed on them. Its a horrible and sad state of affairs.

I have 6,000 miles on my tires now. Show virtually no wear on the treads.
Still shows the yellow ink between the treads. D.B. White wall radials.

 

...doesn't sound like an air pressure problem to me. Next stop needs to be a qualified alignment shop.

.

 

Listen to 73RR above...Not your air pressure

 

I think your air pressure is a tad high. Lowering the pressures smoothes out the ride. But that may be masking some problem in your front end.

 

Sure having all the adjustments ,balance and roundness is a must,but tire PSI must be adjusted to load,not 32#if on a lite hotrod ="""How many lb's your car is puting on to the tire=,the shape of tire tells you by looking at the side wall,from 32#to start with let out PSI tell you see a little flex start to show in the sidewall near the road{just like on bigger cars] this is a good start point/from there you can play with PSI by droping down a few lb's at a time tell best ride is found

 

You said you replaced the fronts only. Is there any chance you still have bias plies on the rear? I bought a set of radials for my '51 and when I mounted them, I only had time to do the fronts before dinner. The drive home from my shop with the old bias plies on the rear was a real "white-knuckle" affair. I was glad it was only 3 miles on a county road. I never really believed the horror stories about mixing bias and radial tires, but I do now.

 

Never adjust ride quality with under inflated tires. Always run the suggested pressures. I'm sure others will argue,but if the ride quality suffers with properly inflated tires the issue is with the suspension. As Tubman said,never mix bias with radials. Been there done that. Big big mistake. All so check the steering box and ***ociated parts.

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All of the above posts have some merit to them. I would drop the pressure to 28, see how it goes and as low as 24. That's a pretty light car with low load-per-tire. Watch the mix-n-match of bias ply to radials and shake down the front end to see if anything is loose.

I have an OT 2012 car with P255/17 radials on it, it weighs in at around 2500 lbs and I run them around 35 PSI.

 

I put an engine in a guys vette one time and topped off the tires to 32 psi to deliver the car back to him. That car was all over the road, the worst handling car I ever drove. I couldn't keep it in my lane. So I stopped and opened the door and the tag said something like 22 front and 24 rear (I forget exactly) so I dropped it down to that spec and it was a totally different car.

So, air pressure can play a big part in how a car handles.

Don

 

Suggested by whom? or what? The maximum pressure stated on the tire? or the pressure recommended in the owner's manual or on the door tag? What if the tires are not the original size, or type?

It's a good question, and the answer is complicated.

 

thanks for all the input..the tires are radial front and rear. and the car handled good before, with the 135r15 but were too small for the north east

 

drop the pressure, see what happens. As was mentioned, you can probably go down to around 22-24 psi.

 

you can lower the air pressure for the light weight of the car , but when you do check the sidewalls after a few miles to see if they are hot , if they are then increase the pressure as it means they are working too much ( flexing ) and the belts will fail

 

thanks everyone for the help

 

My roadster has 135s in the front and 255s in the rear. I run 28 front and 16 rear. The way I set my cars up is I drive up my drive way, concrete, in a straight line. Then look at the dust pattern on the tires. This will tell me if the tires is over or under inflated for the load of that particular car. If there is any black part of the tread with no dust on it then the tire is over inflated. I bleed off 2 psi at a time and repeat until the full tread is covered. If the dust pattern is to the edge of the tread and a bit beyond then it is under inflated for the weight of that particular car. I add 2 psi and repeat until pattern covers just the tread. And yes I know when the tire warms up psi will go up and I adjust pressure after I find out how much it increases after I drive it for a while because I will measure them when the tires are hot and adjust for the increase.
Good luck
Fuzzy

 

My 26 Ford 2000lb coupe runs 18psi in the front tires and 19psi in the rear tires. The tires wear even, the ride and handling is good...................

 

All theses recommendations about "dropping the tire pressure" are guesswork. You need detailed information. All tire manufacturers have "Tire Inflation Charts" for their products. The inflation chart specifies the correct pressure for a certain size and model tire for the load being carried. You need to do at least two things. One is, have your car weighed and get individual axle weights. The second is, access the tire inflation chart, either through your tire dealer, the manufacturer or maybe it's on the internet.

Follow the chart's recommendations for pressure. If you still have a handling problem, as said above, you then have a suspension and/or alignment problem to solve.

Ray