Thread: For Don Shilady

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Jerry is correct again. A "flying brick with a 2 inch chop" is still a "flying brick" aerodynamically! For reasons I don't remember I had a 3/16" spacer between the coil and the firewall allowing the mount to flex and pushing the top of the coil toward the lip of the firewall eyebrow. Removing the spacer and adding a foam rubber pad (pipe insulation) reduces the mount flex. I will rerun the test as soon as we get some clear weather here and I can pump up the tires to the 35 psi maximum. I think the 1st-to-2nd shift is too sharp with almost always a tire chirp which may have loosened the seal of the tubeless tires to the rims. Hopefully using the 35 psi pressure will seal again or maybe I will have to remove the tires and apply some sort of sealer to the rims or use tubes as a last resort. I'll post new results when I can run the course again with better tire pressure. The interesting thing is that the car is light enough so that even at 10 psi the tires were barely noticeable as underinflated. Another chore I need to do is to weigh the car but I expect it to be in the 2600 pound range. This kind of open-ended discussion with experts is what makes this Forum valuable!

Don Shillady
Retired Scientist/teen rodder

Originally Posted by Don Shillady

Jerry is correct again. A "flying brick with a 2 inch chop" is still a "flying brick" aerodynamically! I will rerun the test as soon as we get some clear weather here and I can pump up the tires to the 35 psi maximum. I think the 1st-to-2nd shift is too sharp with almost always a tire chirp which may have loosened the seal of the tubeless tires to the rims. Hopefully using the 35 psi pressure will seal again or maybe I will have to remove the tires and apply some sort of sealer to the rims. I'll post new results when I can run the course again with better tire pressure. The interesting thing is that the car is light enough so that even at 10 psi the tires were barely noticeable as underinflated. That is another chore I need to do is to weigh the car but I expect it to be in the 2600 pound range.

Don Shillady
Retired Scientist/teen rodder

Don,
Running 35psig may give you better mileage, but it will also prematurely wear out your tires due to them running "crowned" with only a portion of the tread pattern contacting the ground fully. To get the best mileage plus the best wear you need to chalk the tires, drive a short distance (100' is enough) and look at the chalk line. Raise or lower pressure until you see the whole line disappear at the same point, showing you that the whole tire is in contact with the road. You'll then get the best of both performance and mileage from those tires. I'd venture that about 20 to 24 psig will be the right numbers for the back.