USD Forks

You might find this link useful, worth checking with a chassis guy but in my experience geometry is measured with a vehicle in it's normal rest position (sitting on the suspension)

 ​​​​​​​https://www.datamc.org/downloads/motorcycle-rake-and-trail-calculator/

Thought I would share that I found a Japanese company that makes a conversion axle for using Öhlins RWU forks with the original Zephyr front wheel. Given that the Öhlins forks and my ZX6R forks have the same diameter at the clamps (35mm), that means it should be the axle I would need. The downside would be no provision for the speedo drive, which I had intended to incorporate into my axle design. 

Here’s the link:
www.spec-hiroshima.com/1003/203/302/401/index.html

Another interesting finding, the ZX6R and Zephyr stock axles measure the same length on the insides when fully tightened (by hand anyway).

Stereordinary wrote:

Thought I would share that I found a Japanese company that makes a conversion axle for using Öhlins RWU forks with the original Zephyr front wheel. Given that the Öhlins forks and my ZX6R forks have the same diameter at the clamps (35mm), that means it should be the axle I would need. The downside would be no provision for the speedo drive, which I had intended to incorporate into my axle design. 

Here’s the link:
www.spec-hiroshima.com/1003/203/302/401/index.html

What year are the forks you are using? I am using ZX9R RWU forks in ZX6R trees (the stem is longer and the top bearing is the same size as my KZ) both use 46mm forks (the bottoms are identical but the top tubes are longer on the 900) I have also harvested material from a bent set of ZX6R forks (they where cheap) for my extensions. I am guessing the 35mm forks are an earlier model (I used 2002 600 parts and 1998 900 parts)

At this time I am trying to fit a set of forks from an '03 ZX6R. I chose them because that particular year used the same rotor diameter (300mm) as my stock Zephyr rotors. Figured that would be one less thing I'd have to worry about. I'm not totally married to these forks though, if there's a more "plug and play" option I'd love to hear it.

I've been working on modeling the forks and some of the other related bits in an attempt to design my own custom top and bottom triples and conversion axle. Here's what I've got so far.





I'm gonna need some more advanced measuring tools if I'm ever going to finish the brake mounts on the forks. For what I'm trying to do though, I think I've probably got enough already. The top triple uses the ZX6R's 210mm spacing between each fork, but the Zephyr's 40mm fork offset. What I might have to do is drop the clamps down in order to make the shorter USD forks match the length of the stock Zephyr forks. Any and all input welcome. 

You might want to check out Zed1015's BOTM build, he has used ZX10 forks and triples (with some reworking) in a 750 Zephyr frame. What is the length difference between the USD's and your stock forks (Rob managed to gain 32mm in length by re-working the fork internals) there is more detail on his build if you check out the Z1OC link for the build thread (in the BOTM feature). Custom triples are nice if you have the skills /budget but there may be a more cost effective solution.

I’m familiar with Zed1015’s bike, he posted about it in one of my own threads a while back. I’d forgotten about how he somehow internally extended the length of the forks and I’m curious how to do that. 

I should measure again to be sure, but last I checked my stock Zephyr forks are about 29.5” axle to top uncompressed, and the ZX6R forks are about 29.125”. Converting to metric that’s only about 35mm difference. 

Stereordinary wrote:

I’m familiar with Zed1015’s bike, he posted about it in one of my own threads a while back. I’d forgotten about how he somehow internally extended the length of the forks and I’m curious how to do that. 

I should measure again to be sure, but last I checked my stock Zephyr forks are about 29.5” axle to top uncompressed, and the ZX6R forks are about 29.125”. Converting to metric that’s only about 35mm difference. 

Check out the build thread here for more info 
urldefense.com/v3/__http:/z1ownersclub.c...p4CGbDvkqLhdJ0nmZqw$

I re-measured the forks and need to correct my previous post. Zephyr forks are actually more like 30.5” and ZX6R forks are 29”, so a difference of about 38mm. 

I did wonder   to be fair if you can get approx 30mm from the originals using Zeds method then you should be "good to go"

Stereordinary wrote:

 

I should measure again to be sure, but last I checked my stock Zephyr forks are about 29.5” axle to top uncompressed, and the ZX6R forks are about 29.125”. Converting to metric that’s only about 35mm difference. 

Pretty much all these forks can be internally extended by 32mm with a simple damper rod extension .
This seems to be the stock length of unswept stanction all manufacturers design into them..
There's actually more like 37- ish mm of unused fork stanction above the top bush but there's around 5mm of spring loaded top out damping which allows the fork to momentarily over extend by that amount if the wheel leaves the ground. 
If you put a fork leg in the vice in it's resting state, stick a piece of tape on the chrome stanction level with the top of the fork seal and pull on the slider it will extend by around a further 5mm against the top out spring pressure and return when you let go..
Those ZX6 forks look to be almost identical to the 05 zx10r forks i used and the 32mm extension worked out perfect.
I also used the 10R yokes with the Zeph stem fitted .