I have a nice 39T ring gear. Can I use a standard 11T pinion or I must use the 13T pinion to get a good gear mesh ?
I don't think so. Roll the pinion around the ring gear. Hear all that noise? I doubt if you would get a quiet rear end. Hell its hard enough with gears that mesh. Maybe is you left a ton of lash. I have the same parts and wondered the same thing but chose not to do it.
Another thought is to buy one of Chaffins 12 tooth pinions. Cheaper than a complete new set and I think the 12 tooth will run fine with the 3 to 1 ring gears. That's the info I got from Glen when I asked about proper gear profile and mesh. It gives 3.25 to 1 RE ratio. I think it'd be fine for a speedster, roadster or travelling on the flat and gentle rolling hills. Not where I live in the foothills of California.
Pat:
I rebuilt the axel with the 39 ring gear & the 12 tooth pinion......... and changed it back to standard gearing 3 years later.
Although we live in a coastal region, we do have some hills..... and it did affect the 'ole T's ascending. Slowed down so much, and also affected braking...... needed more pedal pressure.
Henry knew what he was doing with a 20 hp. engine with limited torque.
Bob Jablonski
I've got a 12 tooth I'm contemplating putting in my 26 Coupe Ruckstell. I also have a dual exhaust manifold, high volume intake, Z-head, and .280 cam, plus Rocky Mountains brakes. I hope I have enough power to pull it easily but I hear mixed reviews. I do live in some long gentle hills and hope to do more touring in the Black Hills. Should it work OK?
Then, again, you could sell the 39 tooth ring for a few bucks and a good standard ring. I might be interested and am sure others would also be. The 39 tooth 3 to 1 rings don't fit on the carriage the same as the standard ring does. Mounting to a standard pinion would be difficult.
W2
An 11 tooth standard pinion gear will not work with a 39 tooth ring gear. the diameter is too small.