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How To Shorten Triumph Motorcycle Forks

This how-to was written and photographed by Joe Zito (scraper on the JJ), and posted here with his permission. It covers an easy and free way to shorten your british front end / forks. This is especially useful to make your chopper or bobber frame sit nice and level to the ground with a hardtail that has drop. Thanks Joe!

When I took the springs out of my fork and let the bike drop as low as it could go, the tire was about 1/2" from the lower tree. It didn't make sense to me to cut the tubes down since that would then let the tire hit the tree when it was fully compressed, quickly leading to some heavy crashing. It may be different on other bikes, but my setup is a '70 TR6C frame with a '71 fork. After a bit of brainstorming and looking around to see what I had, I came up with this sketch:

The drawing on the left is the stock setup with 6.5" of travel (total) and the one on the right, with the 2" spacer, has 4.5" of travel. still plenty enough to be safe. You could probably go more or less depending on the stance or ride quality you were going after. It all depends on how long the spacer you put between the top out spring and the shuttle valve is.

Here are the spacers I made, cut out of the old spacers that were originally in the fork with the chopper tubes - making them longer when installed on top of the main spring.

Since the fork was going to have less travel, I thought it would be wise to firm up the spring a bit by adding some preload. I did this by cutting the main spring a half inch less than i cut the spacers. This makes the spring sit up above the top tree a bit when it's in the fork so you have to compress it some to get the caps on. aka - preloading the spring.
Here's what the shuttle valve looks like with the spacer installed:And here it is being installed into the fork tube: So, overall it shortened the fork 2". Take into account how much weight is going on the bike too because it will have the weight of the motor, gas, oil & your ass on it. Here is the bike with the modified fork and a 4" stretch / 2.5" drop hardtail. Overall I wanted a very flat stance but low as hell. The bottom of the frame is about 4" from the pavement so she's right where I wanted her.

The stock fork tubes were pretty cheap & the "lowering kit" was free. It took me about an hour, tops to lower the fork. It's safe, looks good and it's ready to roll.


One thought on “How To Shorten Triumph Motorcycle Forks”

  • Did a similar thing to the (stock) forks on my 1969 Triumph by adding an extra stock 2" spacer. My question is ; how much less fork oil do I put in? I put in the stock/book cc amount, but now feel the fork hitting/bottoming, possible due to a hydraulic compression effect from too much oil. Is there a way to calculate a correct cc ratio? I'd like to try this before trying a heavier weight oil or reducing the spacer and changing the stance. Thanks

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