Longer lower legs on inverted forks OK?

Folks: I have a GSXR 1000 front end (less wheel and trees) waiting to be grafted onto a Z1 someday. I am concerned about ride height and geometry. Looking at a couple threads in the Projects side, there is real concern the shorter gixxer forks would make the front end too low. Just brainstorming for a bit, what are the pros and cons of simply ordering longer lower tubes from Franks?

For example, I wonder if longer lower legs would apply too much leverage for the seals, etc, to deal with under full braking conditions.

I see the logic in sourcing a longer front end like from a ZX-9, but I got the gixxer stuff from a friend of mine and know these forks are in great shape. Nor do I want to lower the rear end to bring geometry back to spec.

I did a search here, but nothing seemed to address my specific question about putting longer lower legs on inverted forks.

I'm not too worried about the reduced turning radius, the bike will sport a full fairing which would probably reduce turning radius anyway.

I got ´98 GSXR1100 USD front in my ´83 ELR. No problems in geometry but it sits lower than stock. Ground clearance can be an issue when trying to find headers that stack the pipes in line. Didn´t find any so I had to make my own...

But what I´m wondering is that simply getting longer tubes won´t be that easy. The whole mechanism inside the tubes is very precisely the right lenght so you cannot just put longer tubes. Doing so might mean modding the inside parts and thats another story. Or am I wrong? I took mine totally apart so I know whats inside of them.

i would think that longer tubes and appropriate spacers would make the whole thing work just like stock with a lil more clearance.
give it a whirl and report back :ohmy: .

I chose the zx9 forks for this reason. Since then i have seen many with shorter forks and there dosent seem to be any major problems. even with the rearends jacked up higher,as many guys do with the zrx11 arms.
I lowered the rear to be more level . it steers quicker than stock but not fast like a sport bike. I think it could use a lot less rake. i dont have any stability issues at full speed.
I supose the lack of clearance is somewhat like the smaller turning radius. Not rally a big deal.

You could use stepped fork clamps to raise the front end, problem is that's not something you can buy off the shelf. You would need to find yourself a good machinist willing to work with you to design and build it.

Check out the front end swaps forum on 750turbo.com.

9R forks will work (as we all have attested) and your forks will work. Best thing to do is to get them installed, then if it's too low you can do the lengthened tubes, or have a "gull wing" triple tree cut as several have done. Appropriate spacers inside the internals would address most issues, plus a good suspension shop can navigate those minor issues for you. The Europeans do it all the time in the Streetfighters magazine. Just remember that the more a modification is a 'bolt on' the less work and money you're going to have to drop.

steell wrote:

You could use stepped fork clamps to raise the front end, problem is that's not something you can buy off the shelf.

I can't remember exact fork sizes but compare the fork tube sizes between the Gsxr1000 and the CBR929/954. I think the forks interchange and the CBR uses a stepped yoke to gain up to an 1" or so.



You'll need both the upper and lower clamps from the CBR as the offset and fork spacing is different from the Gsxr.

Later, Doug

Thanks for all the help, folks. Now I have some more options. Plus, I've bookmarked that 750turbo forum, lots of info there, will slowly digest over time.

Did I mention that 750turbo.com is my hero's (Lorcan, also a member at KZR) website? 211 mph on a GPz750 Turbo :woohoo:

I'm trying to talk my Nephew into doing a Bonneville assault with his GPz750 Turbo and me as the rider :evil: :evil: