Tires, Low Gear, and Brakes


By E. Meloan

(This article was originally published in the November, 1999 issue of the Spark Coil.)

Howdy, fellow Model T’ers!  The summer touring season is over and Susan and I have had a lot of fun touring in Georgia, Tennessee and Mississippi this year.  During those tours, I’ve seen some  folks who have experienced problems I’d like to chat about.

A surprising number of folks who own Model T’s with 30×3 1/2 and 30×3 clincher tires do not know what the tire pressure in these clinchers should be!  Several T’s had tire problems because the tires had too little air in them.  Clincher tires require much higher pressures than the later 21 inch balloon tires.  A clincher tire should be inflated to at least 50 pounds pressure and 55 to 60 is probably better!  Lower pressures will allow the tire and tube to creep around the rim and will eventually cause the valve stem to be severed!   I was watching as one gentleman with a very nice touring car, backed it out of his trailer at the beginning of one tour.  The tires all looked low and, when I asked him what pressure he was running,  he replied 35 pounds.  35 is great for a 21 incher but NOT for 30’s!  Another fella, on a different tour, was remarking about having to change a flat and when I asked what happened, he said the valve stem was cut off.  When I asked if he was using 35 pounds, he replied yes!

While on the subject of clincher rims and tires, I’d like to suggest that all clinchers should be installed with a tire flap.  I realize there are some who don’t think they are necessary but flaps can eliminate many of the problems clinchers seem to have.  They help protect from tube pinches when installing the tire and they help protect the tube in the area where the tire edges come together in the rim.  While a little expensive, they can be used over and over and I feel they are well worth the cost.  I once had a demountable clincher rim separate because of rust!  The flap kept the tube protected and I was able to continue driving until I reached a service station and could change the tire safely.

Most of us know about the danger of the Model T low gear peddle going past center and locking in the low position but in case we have some new folks who don’t, lets mention it.  One of the participants of the tour along the Natchez Trace had the very unsettling experience of pushing his pedal into low and having it lock  there!  He finally reached down and pulled it back with his hand but it is a scary feeling!

This problem can occur if low gear is allowed to become too loose.  The pedal swings past the center of the linkage with the high speed clutch and is locked there!  The fix is simply to tighten the low band so that the pedal cannot go down that far.  When adjusting the low band, a good method is to loosen the band, push the pedal all the way down, and then tighten it until the pedal has been moved about two inches from the extreme down position.  This should result in a good low that is not too tight on the drum but will give a solid engagement of low gear.

Lets talk briefly about the Model T brakes…  While a well adjusted transmission brake can lock the rear wheels on a T, they are placing a terrible stress on the entire drive train when they do it!  The normal ring and pinion ratio give you almost a 4 to 1 mechanical advantage when pressing the brake pedal but this advantage is also putting a tremendous strain on those 80 year old ring and pinion gears and axles!  If any of these fail, you will be left with NO brakes at all!

For this reason, I  heartily recommend external rear brakes such as the “Rocky Mountain” brand!  While not cheap they can save a lot of expensive repairs to the drive train and they may save your life!  This is even more important for folks who are using two speed rear ends.  If these get shifted to neutral, you have NO brakes unless you have installed external rear brakes.  If you tour a lot, you really should have “Rocky Mountain” brakes for safety and peace of mind.

See you down the road…