Touring progressive fork spring upgrade


Sep 4, 2013
Raleigh NC
2013 R3T, 1960 Franken-Pan
Decided as I can't ride for a month or so while I recover from surgery, might as well do some upgrades.

Got out the manual and read through it and went what the heck??? Looked at the bike and lo and behold, no drain plugs on the lower sliders. Could understand that in a Roadster or such with inverted forks. BUT, the touring has plain old forks that Harley started using in 1949.

Was going to flat rate it and pull the bolts that secure the dampers at the bottom and let her drain for a day or so. Started clearing the decks and noticed the left fork tube is just a bit to far through the top yoke. Took an eyeball on the right one and it's through the clamp by over a quarter inch. Supposed to be flush with the top of the upper clamp. So in a nutshell, my right fork is considerably shorter than the left and has probably been like that since it left the factory.

Solved that decision, it's coming all the way apart so I can see what else they hosed up in jolly old England.

Now first tech question. Book says air gap of 110mm. Instructions from Progressive sez nay. They say 140mm is absolute minimum air gap due to the spring design displacing more oil.

I tend to think that the spring instructions over rule the manual in this case.

Anybody else that's done this, what air gap did you use and with what results?


stand up straight and grab the world by the a$$
Jan 24, 2013
07 rocket III classic
i would say that the air gap would have a very small effect on the spring size but may have a large effect on the amount of oil.
a 30mm = 1.1811 inch
a little less oil would be a lot better than to much.
more air gap safter
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