MTFCA Forum

What is reccommed tire pressure on 30X3.5 demountable rims? Thanks, paul

60psi. 60psi.

If it is a roadster, you might consider 55 PSI instead of 60 for a gentler ride.

I do run 60psi on my clincher tires----- is this also required for the demountables on my `24 touring? seems a litle high.......thanks

paulgriesse wrote: ↑

Wed Aug 31, 2022 2:55 pm

I do run 60psi on my clincher tires----- is this also required for the demountables on my `24 touring? seems a litle high.......thanks

YES. The high pressure is REQUIRED to keep the clincher tire on the rim. Demount-able or not, they are the same tire.
The 21" is a non clincher & will not roll off the rim. hence 32# & less works fine & allows for a softer ride.

I don't think 65 or 70 psi will hurt. The important thing is to not let them get below 55 psi. Low pressure means adios llanta.

The problem with running them low is that they tend to slip on the rim and if the slip, it might pull your valve stem off leading to a quick flat tire. They can also flip off the rim if too low.
Norm

55-60psi. Since the tubes aren't the best quality and leak slowly, I check pressure every week when driving.

John, makes a good point. Being a 24 model normally means 30 x 3.5" clincher tyres, which need 60 psi. If your car has demountable 21" tyres, they are straight sided tyres like ordinary cars, and can be run at lower pressures. Both 30 x 3.5" Clinchers and 21" straight sided tyres can be demountable, so describing them as demountable without reference to the actual size is not going to give you reliable responses.

Hope this helps.
Allan from down under.

The "high pressure" clincher tires are just that: high pressure. 55 psi would be the minimum cold pressure for safe operation on a light bodied, lightly loaded Model T, and 60-65 psi cold pressure would be appropriate for a closed car or a load-carrying pickup. An accurate gauge and frequent pressure checks are necessary.

Years ago I built a speedster and mounted the tires and filled with 60#. Months latter I finished the car and went for a test run. My friend was holding the GPS calling out the speed as I drone the car. He called out 45-50-52-54 mph and the left rear tire came off the rim. We were lucky and no damage to car or us. I forgot to check air pressure before driving off for test run. The other 3 had about 20#.

Model T tires, including the "low pressure balloon tires" are low volume tires. They do not need to lose much air to lose a substantial amount of pressure. I find that small variations in tire pressure can materially affect ride and handling with 4.40 X 4.50 X 21 "balloon" tires. The clincher tires get downright dangerous if correct pressure is not carefully maintained.