In reference to the question about wide tires on a mid '70s Shovel swingarm frame with a Panhead driveline, I'd say the biggest tire that can be run would be a 130 maybe a 140 depending on the side wall of the tire (tire to chain clearance). The main problem as I see it is the '49 Panhead driveline. These engines came with a tapered sprocket shaft that doesn't lend itself readily to offsetting the transmission, due the minimal selection of offset sprockets sprockets for this type of shaft.

Another point, would be the inner primary case and the engine case would have to be modified to bolt together. Early Panhead cases have a cast in lip that was used to locate the front of the tin inner primary cover, later hard aluminum inner primary covers were machined flat in the area where they mated to the engine cases.

If this gentleman is still using an early 4-speed transmission case or wants to, he will need to modify the transmission mounting plate and fifth bolt mount, when moving the trans to the left and all. A suggestion would be to go to a later model case, so an inner primary can be mounted or a motor plate if some one offers a plate with a belt drive kit.

A quick and cheap (relatively) way of going to a 150 tire would be to run a primary chain with some type of shroud. Fit a 1/4 inch longer mainshaft in the transmission, and obtain another front motor sprocket. Machine both sprockets so they fit inside each other. In plain terms, machine the center out of one and the teeth from the other until they just slip fit together, offset them the same as the trans mainshaft and weld them together.

I've been through this. You don't offset your tranny. CCI makes a kit with an offset tranny sprocket and spacer to offset the rear sprocket. A 150 will work.

Anything larger and you get swingarm/chain interference. I did run a 160 for a while , but had to shave the chain side of the tire for clearance. You might also have to space the fender struts out a bit if the tire hits. Then widen the fender, It's a bit of work. Just put a 140 on. No changes, fits right in.