Shortening USD forks?

I bought some 48mm USD forks for my DR-650. I've been running the bike with the stock front end lowered via the factory method. Stock forks measure 23 inches unloaded (bottom of bottom triple and bike on stand) ... the USD's measure 26 inches unloaded. I've gotten so that i like the lowered configuration and now am wondering what i can do to reliably shorten the USD forks to match the stock DR's. Is this possible or is my only other option street bike USD's that will probably be too short?

Thanks in advance for any help.


You could certainly shorten travel, just like the stock DR650 forks, by machining travel limit spacers for the USD forks. Of course you'd want to do it correctly to make sure you wouldn't suffer from top out issues but I see no reason why it could not be done for a reasonable amount of time and $ invested.

Thanks for the info Rob. I've never had USD forks apart so with your idea in mind, i'll take these apart and see what i can make. I can probably also shorten stiffer springs to match. Thanks for the help!

most suspension company's can do this, normally around 2". sorry i don't know how its done. somebody?? maybe post up on the suspension form. there is some info there, but not how it's done. good luck----

Shortening forks isn't a huge deal I've done it several times by installing newer forks on older MX bikes, just remember that the spacer goes between the short top out spring and the damper rod.

One thing though, your measurements are throwing me off, try measuring from the axle center to the top of the fork. The difference is how much you need to shorten by.

Once the spacer is installed check the spring preload, on my dirt bikes I normally only look for about 10 to 15mm of preload. In your case because you are using different forks you need to know what spring rate you had and what you are going to have. If you happen to get lucky and find out that the rates are the same then you only need to have the same amount of preload.

If you do have to cut the donor fork spring to get the preload right just remember that anytime you cut a spring down you increase the spring rate. And at that point I would consider calling someone like Race Tech and see if they have a shorter spring for your newer forks with the proper rate.

Thanks bergman and zig. I'm going to need about 3"total in length reduction and since the bike is now in supermoto form, it's not going to see any off road work. So, i can experiment with the spring rate until i get it to handle like i want.

EDIT: Well, i just looked at the fiche on Ron Ayers and it appears that these forks are a cartridge type of fork and do not have a top out spring or a spacer. Looks like i'll need to find another set of forks.

Thanks guys.

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