nkaminar
Well-known member
I recently visited a good friend who has a 30 coupe with 6.50-19 tires on it. He has 25,000 miles on the tires and they looked like they would go another 25,000 miles or more. He has radial ply tires. He runs with 35 psi tire pressure.
My 1930 Fordor sedan is heaver than his coupe. I decided to try the 6.50-19 tires after a disappointing 8,233 miles out of my radial 4.75/5.00-19 tires (brand name withheld). My sedan weighs over 3,000 pounds based on a truck scale and a lot of the weight is at the rear because of the sedan body and a heavy trunk full of heavy tools and parts and the spare mounted at the back of the trunk. The rear tires wore out first.
I used the correct size tubes from Lucas and tire talc from Aircraft Spruce. The tires are Lucas at about $200 each. They are bias ply. The tread width is 4.75 inch which is more than a passenger car 6.00-16 tire.
The larger tires are about 5% larger in diameter so my mph is 5% faster at the same engine rpm. This lowered my effective rear end ratio from 3.78 to about 3.6 and in overdrive from 3 to 1 to about 2.85 to 1. I am now using second overdrive rather than third direct and third direct more than third overdrive.
The specification calls for 35 psi. I tried that first but the car did not seem sure footed. It felt like I was driving on ice. I ended up using the caulk test to find the best tire pressure. The caulk test is where sidewalk caulk is put on a patch of the tire, see figure 1 below, and then the car is driven to look at what part of the tire is not in contact with the pavement, see figure 2. I found it was easier and more accurate to look at the print on the asphalt rather than the tire. It was clear where the tire was making contact with the pavement, see figure 3. Figure 3 shows an extra mark to identify it as a rear tire and this was after reducing the tire pressure.
I ended up with 14 psi in the front and 18 psi in the back. I know that this seems low, but the car handled well and gripped the road well. The 6.50-19 tires are 6 ply rated and meant for heavy cars like Franklins or smaller Rolls Royces. Because of the steel bands in the tread area of radial tires, the tread area does not bulge out like these bias ply tires do. So if you want to try 6.50-19 tires, and can afford radials, and are concerned about running low tire pressure, that would be your better bet.
I wanted to stick with the 19-inch wheels so I did not consider the 16-inch tires. The 16-inch truck tires are low cost and will last a long time. It will be interesting to see how long these tires last. If I am not dead when they wear out, I will report how long they lasted to the group.
On my car, there is still plenty of fender clearance and no interference with the brake rods.
My 1930 Fordor sedan is heaver than his coupe. I decided to try the 6.50-19 tires after a disappointing 8,233 miles out of my radial 4.75/5.00-19 tires (brand name withheld). My sedan weighs over 3,000 pounds based on a truck scale and a lot of the weight is at the rear because of the sedan body and a heavy trunk full of heavy tools and parts and the spare mounted at the back of the trunk. The rear tires wore out first.
I used the correct size tubes from Lucas and tire talc from Aircraft Spruce. The tires are Lucas at about $200 each. They are bias ply. The tread width is 4.75 inch which is more than a passenger car 6.00-16 tire.
The larger tires are about 5% larger in diameter so my mph is 5% faster at the same engine rpm. This lowered my effective rear end ratio from 3.78 to about 3.6 and in overdrive from 3 to 1 to about 2.85 to 1. I am now using second overdrive rather than third direct and third direct more than third overdrive.
The specification calls for 35 psi. I tried that first but the car did not seem sure footed. It felt like I was driving on ice. I ended up using the caulk test to find the best tire pressure. The caulk test is where sidewalk caulk is put on a patch of the tire, see figure 1 below, and then the car is driven to look at what part of the tire is not in contact with the pavement, see figure 2. I found it was easier and more accurate to look at the print on the asphalt rather than the tire. It was clear where the tire was making contact with the pavement, see figure 3. Figure 3 shows an extra mark to identify it as a rear tire and this was after reducing the tire pressure.
I ended up with 14 psi in the front and 18 psi in the back. I know that this seems low, but the car handled well and gripped the road well. The 6.50-19 tires are 6 ply rated and meant for heavy cars like Franklins or smaller Rolls Royces. Because of the steel bands in the tread area of radial tires, the tread area does not bulge out like these bias ply tires do. So if you want to try 6.50-19 tires, and can afford radials, and are concerned about running low tire pressure, that would be your better bet.
I wanted to stick with the 19-inch wheels so I did not consider the 16-inch tires. The 16-inch truck tires are low cost and will last a long time. It will be interesting to see how long these tires last. If I am not dead when they wear out, I will report how long they lasted to the group.
On my car, there is still plenty of fender clearance and no interference with the brake rods.
