Fitting a 1-1/8″ suspension fork into the 1″ Dyno Glide frame

 

I modified, enlarged, the inner diameter of the lower bearing cup that came with the frame.

For clarity: I am calling the part of the bearing that is press fit into the head tube the bearing cup, and the part of the bearing that fits on the steerer tube the bearing cone. The inside diameter, or ID, of the bearing cup, is an interference fit with the larger 1-1/8″ steerer tube.

The larger diameter of the 1-1/8″ steerer tube is too large to fit inside the bottom bearing cup. Using a Dremel (die grinder would work) I ground off the inner face of the bottom bearing cup to accommodate the taper of the 1-1/8″ steerer tube. This allowed for the 1-1/8″ tube to fully seat into the head tube without binding. I left the bearing cup in the frame but blocked off the head tube with a rag, while grinding, to keep the filings out of the frame.

The original lower ball bearing cage did not fit because the balls are too large for the larger diameter of the 1-1/8″ bottom bearing cone. I used 1/8″ loose ball bearings, lots of ’em from McMaster, to complete the task. I lubed up the bearing cup and carefully installed the new 1/8″ balls in place.

One must get creative to replace the original dust cover and seal to keep dirt out of the bearing assembly.

I think this would work with other 1″ frames and 1-1/8″ forks. I took out the original fork and wiped off all the lubricant around the lower bearing cup and head tube in general. Then I took the all the parts off the fork steerer tube except for the lower bearing cone and carefully inserted the steerer tube into the head tube and noted where the steerer tube bound on the ID of the bearing cup. If you are installing a new fork then you may have to press the lower bearing cone into place on the steerer tube.

The ball bearings will ride on slightly different points in the cup and cone but as long as the balls ride on a hardened bearing surface this will not be an issue.

Not much to see with a photo…but when I take the frame apart for powder coating I will take a few pics.