Lengthening USD's

[speeddemon]

Can you extend USD forks by lengthing the damping rod to effectively give you a longer fork length (no more travel though). This can be useful for bandit owners where the stock GSXR1000 forks etc are a bity on the short side

Yes - I asked this question on Old Skool and was told it was done by someone but knowone gave me much insight.

This also raises another issue - you could take the internals from a R1 and stick em into 1100 USD's, given they fit diametr wise and Ohlins makes em anyway..see where Im going? It has bee done.

So how the hell do I do it - Anyone done it here?

[ozkat]

Ive got 50mm titanium extensions on my USD forks in my Katana, i can try to find out more info if you want.

[Large]

quote:Originally posted by ozkat

Ive got 50mm titanium extensions on my USD forks in my Katana, i can try to find out more info if you want.


Hey Oz,

Do tell...pics too pls

While you're at it...How long are your forks (without the extensions) and how much ground clearance have you got from the frame to the ground?.

Cheers

Rich

[chopaweeza]

I saw a set of RGV250 USD's stretched a few years back with T6 Ally extensions. They were on a worked GSX750ESD . The owner told me they were one piece units with solid internals(removing the adjusters effectively) Looked good as they were smooth on top but they would have to be set up the old fashioned way with shims to get them spot on. Doings them that way would require not alot of machining to get right as you are simply screw cutting a solid piece to act as a plug. There are obviously better ways to do it and I'm curious what they are as I have shorties on the Buildoff GSXR and am interested in making them longer.

[EXBEN]

Do it the easy way with some extensions that clamp around the fork leg then go into the top clamp,much easier than modifying the internals,I did a Vmax like that I'll see if I can dig out a pic if ya want.

[EXBEN]

http://www.streetfighters.com.au/forum/upload/24845113373827.jpg
Maybe not the easiest to make out but the extension is the shiny bit at the top If you didn't know.

[ozkat]

ok here are some pics and dimensions, im pretty sure im running RGV usd forks. from the lowest point of the frame to the floor is 190mm (thats with the bike standing upright and just the weight of the bike on the suspension. The outer fork tubes measure 470mm standard height and 520mm with the extensions. total length of the forks (again with just the weight of the bike on the suspension measured from the top of the standard forks to the centre of the axle) is 690mm or 740mm with extensions. i hope this helps.

[ozkat]

http://www.streetfighters.com.au/forum/upload/24845114768838.jpg
extension covered by clipon clamp

[ozkat]

http://www.streetfighters.com.au/forum/upload/24845114760222.jpg Ti extension 50mm

[ozkat]

http://www.streetfighters.com.au/forum/upload/24845114761158.jpg 190mm from frame to ground

[ozkat]

http://www.streetfighters.com.au/forum/upload/24845114762126.jpg 520mm total length of outer tube

nice legs shaynno,do you shave or wax?

[ozkat]

http://www.streetfighters.com.au/forum/upload/24845114756846.jpg RGV forks into Katana

[Large]

quote:Originally posted by ozkat

http://www.streetfighters.com.au/forum/upload/24845114760222.jpg Ti extension 50mm


Thanks Ozkat,

I'll compare mine when I get them back.

So what's holding the extension on in this pic...just the top triple and clip ons?

[ozkat]

i presume its threaded and simply screws into the tops of the forks.

[chopaweeza]

Bob Brown Engineering in Victoria were doing 75mm screw in extensions for RGV forks a while ago. I don't remember the price though. They where in a magazine article or something.

[speeddemon]

Thanks OzKAt - Ill consider external extender - possibly easiest option. I assumke it just threads into the existing cap thread and extends down far enough for your rebound adjustment to still work?? As most of the bending load is on the bottom tripple it would seem to work OK.

The other option I was implying was:

You know in a USd when you are changing fork seals there is a hell of alota chrome slider in there and the only reason it is the length you see (basically your travel) is cause of the dampening rod length cause it bolts to the top of your fork and effectively sets how long the fork extension can be.

If you extend the rod length and/or make an adaptor to suite your stock top fork cap you can keep the stock fork caps but you gain just say and inch down at the slider - now there is no travel gain though, just extra fork length. Obviously you can't go too far as your forks can bend easier, but if all you need is an inch? And like I said there seems to be no limit on what internal you actually chose to use (except from internal diamater and spring to suite).

[stevo]

Just a tip if ya gonna extend like Ozcats done....

machine the plug to be longer than the thread and have that diameter the same as the inside of the forks .... basicly ya wanna have it as long as ya can to give it more strength...

have done a few like this

[speeddemon]

Thanks Stevo - figured as much.

[stevo]

I may be doin a normal set in the next few weeks ..We're just waitin on the triple clamps to come in first.... if so I'll take some pics ta show what I mean...the principle is the same ...but as ya say the damening rod may need to be longer ..
It would depend on the fork design as there's a few different designs in use..





Probably the easiest way on most USD with preload and rebound adjusters on the top would be to make a new extension cap with the preload adjuster recessed into the new cap ... using that idea you could then make a dummy cap to have a clean top...and nothing internally needs to be changed....

Ben's way of going over the outside and turning that into a feature is another good way to do it..

either way ya want the extension piece to be as neat a fit as possible and as long as possible to give the most strength

[UKB12]

How's things going with this? Stevo i'm not quite sure what you mean as the inner size of the original fork tube under the thread is wider than the thread so if you 'machine the plug to be longer than the thread and have that diameter the same as the inside of the forks' it'll be wider than the male thread & you won't be able to screw it in? I think!