USD forks?

has anyone fitted USD forks to a GPZ550, Z500, KZ550?

i want to do the mod on my Z500 and was wondering what bikes they got the forks off, would be easier to have a starting point!!

all the USD forks on ebay seem to be really expensive or off trials/motorcross bikes.

Ok, I give up... what are USD forks?:blink:

There a re few on here that have done it to the 900's and 1000's so I'm sure the 550 would be about the same. Try going to suspension on ebay and type in gsxr or what ever brand you want to use.

USD are the upside down style forks on almost ever bike made nowadays.

Bluemeanie wrote:

Ok, I give up... what are USD forks?:blink:

USD = upside down forks

Is there a reason for going with USD forks? Is it for looks, or what? You probably need something from a 600-750cc range to get close to spring rating you need.

Conventional forks work just as good as are a little easier to install seals on. Plus are alot cheaper!

That's just my $0.02.

Later, Doug

because they look cool as fook!
and the front end needs a rebuild anyway!

Taken for wikipedia, "This is done for two reasons: to reduce unsprung weight by having the heavier components be suspended, and to improve the strength and rigidity of the assembly by having the bulkier and stronger component being directly supported by the pivot"

Unless you get a set from some the later oil cooled Gsxr's you're gonna lose your speedo drive.

Frank wrote: "Taken for wikipedia, "This is done for two reasons: to reduce unsprung weight by having the heavier components be suspended, and to improve the strength and rigidity of the assembly by having the bulkier and stronger component being directly supported by the pivot" "

The 500 isn't a heavy weight so the strength given from the USD aren't going to matter all that much. Plus my thought is that going with a beefier front end is just going to transmit for forces into the frame which might not be able to handle it. Your frame might not be able to cope with larger convential forks but USD will be over kill.

If you do decide that the extra $$ is worth the look then go for it. Keep us informed with lots of pics!

Later, Doug

The only thing that would be different is the stiffness and such of the springs. Also there is probably less travel. It would probably be a rougher ride, but the stiffness along with less unsprung weight "should" make it handle better. You have to take into account the length of the new forks compared to yours, if they are shorter or longer it will affect the steering geometery.

Post edited by: Frank, at: 2007/12/06 12:03

iandz500 wrote:

because they look cool as fook!
and the front end needs a rebuild anyway!

Ha-haaaaaaaaaa! Right you are! And they'd look bitchin' on your bike.

First off the old school components are done in the old school way of making it built to last and over-building in some areas. The travel - as noted - will most likely be more on your stock conventional forks, as compared to USD forks. More travel can get you a more compliant (ie: softer) ride...weigh that in for what it's worth to you. Frank noted that the beefier forks are stronger and will transmit more energy into your frame. Correct. What's that mean? The frame will flex more (when ridden hard) b/c the forks aren't going to, and that energy has to go somewhere. The frame will take a lot of energy and then it will flex some. You will feel it if/when you ride so hard that this happens (ex: a track-day, deep, deep, deep into a corner...and the bike might not want to hold the line as well as you want it to; but it's not like the bike is going to suddenly break in half). Ask youself this: Am I going to ride this bike hard enough for this to matter? If you are and you want to keep the bike, brace the frame in key areas (steering head, swing-arm pivot/rear motor-mount area, etc...).

Fiction: the big forks weigh more than the conventional forks.
Fact: Older forks are (as noted) often very heavily built (another way they gained structural rigidity), most new USD forks and triples (b/c you have to have the triple also) weigh less than the old components...shocking, but true.
Fact: if you go with 17"s (since you will have the forks to take 'em) you will have access to superior tire selection, improved braking, improved handling, less reciprocating mass, etc.

Fiction: The suspension won't work b/c your bike is smaller and weighs less.
Fact: Most likely, the front suspension will be better right off the bat b/c the new bikes weigh about the same as your bike and the suspension will have far superior adjustment capacity. (ex: a Suzuki TL1000S weighs within two pounds of your bike...dude, I lose more than that in a morning...er..."setting"...:lol: )


Drawbacks: it's going to take a bit of work.
Suggestion: look at other bikes on this site to answer questions before you get into your build. My personal suggestion: buy a complete front end, modify the new triple to fit your bike, then bolt the new front clip on and 'go'. (Be cautious at first as you may want to adjust your new front suspension.)
Conclusion: I'm chiming is b/c I've done it several times. It's worth it. The bike handles much better (simple physics, but do be cautious in modifying the rake), looks cool (subjective), and allows access to superior components (tires, brakes, etc...).

Just my 2 pennies; please keep us posted on your progress...I love a good project.
Good luck, man!!!

iandz500 wrote:

because they look cool as fook!
and the front end needs a rebuild anyway!

Ha-haaaaaaaaaa! Right you are! And they'd look bitchin' on your bike.

First off the old school components are done in the old school way of making it built to last and over-building in some areas. The travel - as noted - will most likely be more on your stock conventional forks, as compared to USD forks. More travel can get you a more compliant (ie: softer) ride...weigh that in for what it's worth to you. Frank noted that the beefier forks are stronger and will transmit more energy into your frame. Correct. What's that mean? The frame will flex more (when ridden hard) b/c the forks aren't going to, and that energy has to go somewhere. The frame will take a lot of energy and then it will flex some. You will feel it if/when you ride so hard that this happens (ex: a track-day, deep, deep, deep into a corner...and the bike might not want to hold the line as well as you want it to; but it's not like the bike is going to suddenly break in half). Ask youself this: Am I going to ride this bike hard enough for this to matter? If you are and you want to keep the bike, brace the frame in key areas (steering head, swing-arm pivot/rear motor-mount area, etc...).

Fiction: the big forks weigh more than the conventional forks.
Fact: Older forks are (as noted) often very heavily built (another way they gained structural rigidity), most new USD forks and triples (b/c you have to have the triple also) weigh less than the old components...shocking, but true.
Fact: if you go with 17"s (since you will have the forks to take 'em) you will have access to superior tire selection, improved braking, improved handling, less reciprocating mass, etc.

Fiction: The suspension won't work b/c your bike is smaller and weighs less.
Fact: Most likely, the front suspension will be better right off the bat b/c the new bikes weigh about the same as your bike and the suspension will have far superior adjustment capacity. (ex: a Suzuki TL1000S weighs within two pounds of your bike...dude, I lose more than that in a morning...er..."setting"...:lol: )


Drawbacks: it's going to take a bit of work.
Suggestion: look at other bikes on this site to answer questions before you get into your build. My personal suggestion: buy a complete front end, modify the new triple to fit your bike, then bolt the new front clip on and 'go'. (Be cautious at first as you may want to adjust your new front suspension.)
Conclusion: I'm chiming is b/c I've done it several times. It's worth it. The bike handles much better (simple physics, but do be cautious in modifying the rake), looks cool (subjective), and allows access to superior components (tires, brakes, etc...).

Just my 2 pennies; please keep us posted on your progress...I love a good project.
Good luck, man!!!

As far as unsprung weight goes; the aluminum slider on my KZ550 weighs very little compared to the big steel fork-tube. It probably weighs less than the steel tube on USD forks, plus the USD has to add a large bracket to carry the brake hardware and fender, which adds a little more weight.