RSU GSXR upgrade, 954 triple tree question.

[wkmpt]

Hi.

I have a complete '90 GSXR 750 front end to be installed on my 750. I want to try to resolve ground the potential ground clearance issues.

I've seen that some folks are using the 954rr drop triple to gain a little height, I was wondering if anyone knows if I could get away with just the top tree of the 954 and the lower tree from the gsxr.

Reason I'm asking is complete 954 triples seem stoopid expensive, also I'm concerned that most of them have the opening in the bottom triple for the larger diameter usd forks, and not the RSU forks I'm installing.

Barring that, anyone know of a CNC guy that does quality work on the inexpensive so I can get a set of extenders similar to Mindless's:

These look awesome, the only thing I'd change would be to design them so they could be clamped to the forks.

Thanks for the time and input!

[Billy Ricks]

Won't work, you have a 43mm fork and the 954 triple is 50mm at the top. Even when using inverted GSXR forks you have to use the complete 954 triple. The '90 forks probably won't cause you any grief with the suspension properly set up.

[Quasimodo]

Don't mean to hijack the thread, just for my own info, am I to understand that a Honda CBR954RR triple bolts on to a GS (e.g., a 1983 GS750E)?

[ukilme]

Ya, they bolt on but you have to change the bearings (depending on the year). They can be expensive on ebay but keep your eye open. I got a 02 set for 50 bucks. They only isuse was no bolts and dirty as hell.

You do have to use the upper a lower as I believe the offset is different from a cbr triple and gsxr triple tree

[posplayr]

big question is how long are the forks from axle center to the top of the tube?

What is the difference in height between the top of the tube clamp and the top of the bearing race in the frame (this is a measurement of offset of the top triple)

[salty_monk]

What is the length of the front end you have at full extension from centre of the axle to the top of the tubes?

What size front wheel are you planning on going with? 17"? 18"? Stock?

[wkmpt]

big question is how long are the forks from axle center to the top of the tube?

What is the difference in height between the top of the tube clamp and the top of the bearing race in the frame (this is a measurement of offset of the top triple)

What is the length of the front end you have at full extension from centre of the axle to the top of the tubes?

What size front wheel are you planning on going with? 17"? 18"? Stock?

I measure the forks from axle center to crown at (or damn close to) 735mm.

Top triple tree--Measuring from the bottom of the nut that tightens over the race (tightened as far down as it will go on the stem) to the bottom of the tree, there is no more than 13mm of space. Would this make it a +10-12mm?

The wheel that I have presently is a 17x3.5, "twisted tri-spoke" style GSXR rim.

[posplayr]

I measure the forks from axle center to crown at (or damn close to) 735mm.

Top triple tree--Measuring from the bottom of the nut that tightens over the race (tightened as far down as it will go on the stem) to the bottom of the tree, there is no more than 13mm of space. Would this make it a +10-12mm?

The wheel that I have presently is a 17x3.5, "twisted tri-spoke" style GSXR rim.

OK you had me a little confused; You must have the 88-89 GSXR 750 RSU; they went USD in 90.

The USD is about 729mm and I think you lose another 0.5" relative to a stock ED triple clamp.

You need to looks at how your bearings will stack and how much more you will loose there with the triple clamp comparing yours to the GSXR.


what are your plans for rear shocks and wheel?

[wkmpt]

OK you had me a little confused; You must have the 88-89 GSXR 750 RSU; they went USD in 90.

Gotcha. I thought they went USD in '91. So I don't know the exact year, but one way or the other I CAN say that they are RSU 43mm forks.

The USD is about 729mm and I think you lose another 0.5" relative to a stock ED triple clamp.

You need to looks at how your bearings will stack and how much more you will loose there with the triple clamp comparing yours to the GSXR.

Guess I won't know until I get there...still have to get the bearings in-hand.

What are your plans for rear shocks and wheel?

I have a 17x4.5 twisted-spoke 94-96 rf600 wheel on the way, and an aluminum 1100 swing arm in the basement to go with it.

For shocks, I'm not set on what I'm doing yet, I was contemplating getting something a little longer than stock to shrink the perceived rake of the front end, and stiffer too since I'm a solid 225# right now.

My plan is also to go 530 chain, I need to do some searching homework here to figure out which size offset sprocket I'm going to need in the front and what gear ratio to consider.

[posplayr]

PM if you want the Excel spreadsheet, but after running the numbers the best way for you to not have clearance issues using that short of a front fork is to do essentially what 80GS1000 did which was to get the rear up and increase exhaust clearance.

That means add about 1" to the rear shock length (get swing arm shock mounts modified to increase the effective shock length)

Get a 4:2:1 exhaust which will buy you more clearance than anything else. This usually buys about 0.75-1.0" depending on how close they fit.

You see each row is a different configuration. Mine is listed across the top and is compared to a stock GS1100EZ/ED. Assuming your bike is similar then look through the variation I have in yellow with your name at the left.

There are different tire/wheel combinations. I have your fork length included. The primary adjustments beyond that are triple adjustments, rear shock adjustments and exhaust clearance adjust. Depending upon the combinations you get the result at the extreme right hand side. A typical GSXR 750 with 17" wheels doing nothing else will lose 1.93" and with the longest GSXR 1100 fork 1.28". Generally the GSXR 1100 conversion doesn't seem to have ground clearance issues because the forks act better than the old GS RSU forks. So you don't have to fully compensate for ground clearance loss.

So by either raising the rear with an elongated shock or modified mount, or going 4:2:1 with would allow you scrape free riding with your setup.

[wkmpt]

PM if you want the Excel spreadsheet, but after running the numbers the best way for you to not have clearance issues using that short of a front fork is to do essentially what 80GS1000 did which was to get the rear up and increase exhaust clearance.

That means add about 1" to the rear shock length (get swing arm shock mounts modified to increase the effective shock length)

Get a 4:2:1 exhaust which will buy you more clearance than anything else. This usually buys about 0.75-1.0" depending on how close they fit.

You see each row is a different configuration. Mine is listed across the top and is compared to a stock GS1100EZ/ED. Assuming your bike is similar then look through the variation I have in yellow with your name at the left.

There are different tire/wheel combinations. I have your fork length included. The primary adjustments beyond that are triple adjustments, rear shock adjustments and exhaust clearance adjust. Depending upon the combinations you get the result at the extreme right hand side. A typical GSXR 750 with 17" wheels doing nothing else will lose 1.93" and with the longest GSXR 1100 fork 1.28". Generally the GSXR 1100 conversion doesn't seem to have ground clearance issues because the forks act better than the old GS RSU forks. So you don't have to fully compensate for ground clearance loss.

So by either raising the rear with an elongated shock or modified mount, or going 4:2:1 with would allow you scrape free riding with your setup.

Capital! I like both methods. Hmm...perhaps I can raise the rear end a little and get a 4-2-1...

Getting the mounts moved wouldn't be difficult, it's not on the bike. I also figure that a few simple welds would be less expensive than a 4-2-1...

That said, I would like very much to begin weighing my options for 4-2-1 exhausts. Who makes them? I know there's a Bassani, who else?

[wkmpt]

Would it be a bad idea to simply use longer shocks to raise the back end?

I've been looking at some of the Ikon shocks out there that would be longer than stock. Here's a .pdf with the details of their shocks.

http://www.ikonsuspension.com/download/2009-shock-absorber-details-full.pdf

[Billy Ricks]

You're already going to be dropping the front a bit which is going to quicken the steering. Raising the back will make it steer even quicker. Do the front first and see where you are as far as clearance and how the bike sits. Get used to riding it like that then decide if you want the longer shocks.

[CCC-TT]

back from the dead... any more info on this setup?