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A modern fork upgrade for 17,18 and 19" wheels

J

John Kat

Forum Sage
I've been playing with three type of forks on my GS 1000/1100's ( std,GSXR 1100G/H and GSXR 1100/Bandit 1200)
To me the clear winner is the later Bandit 1200/ GSXR 1100 K fork:D
The reason is simple, these forks are equipped with a cartridge type damper that makes a huge difference in terms of comfort but also in terms of roadholding, bringing the bike in the modern age.
The only issue is that this fork works only with the original 17" wheels as the spindle measures 20 mm in diameter.
To make this work with our 19" wheels that run on a 15 mm spindle, I devised a simple reduction scheme that you can see in the pictures below.
As the spindle I use comes from a GSXR 750/1100 G, the fork can also take the 18" wheel these bikes had.
Coming back to the GS 1000 wheel, the pictures also show that it will be very easy to adapt the corresponding calipers.
I can't wait to try this on the road:)

GS1000forkupgrade013_zps36e9c1b8.jpg


GS1000forkupgrade001_zps65dc8135.jpg


GS1000forkupgrade014_zpsec15043e.jpg
 
Dogma said:
Very interesting. What work is required on the triple clamps?
Click to expand...
The triple clamps I use come from the GSXR 1100 K ( 1989) that drop right in!
The lock stops have to be added:o
I believe the stem on the Bandit 1200 is too long for the GS 1000/1100?
Here's how I did them on my 1100 Kat.
fec3dd4d.jpg
 
To get around the 15/20mm axle mismatch when I put 17's in our racebike, I made up a full width spacer 15bore and 20OD - this gives the benefit of a 20mm axle which is much stiffer than a 15mm one.
Probably not necessary on a road bike but I wanted torsional stiffness. It worked, we don't need a fork brace.
 
John Kat said:
The triple clamps I use come from the GSXR 1100 K ( 1989) that drop right in!
The lock stops have to be added:o
I believe the stem on the Bandit 1200 is too long for the GS 1000/1100?
Here's how I did them on my 1100 Kat.
Click to expand...

I am watching this thread closely! I have a similar swap in mind. In an attempt to upgrade me ES with "period improvements" :cool:I also want to use RWU forks, rather than the more common USD forks. I have my eye on a complete bandit front end. Can anybody confirm that the Bandit stem IS too long for the GS1000/1100 frame? Thanks in advance, Paul
 
salty_monk said:
How long are they John? :)
Click to expand...
The GSXR 1100 K stem is 230 mm long from the base of the bottom bearing to the top of the stem.
Talking about lengths, a quick reminder of the length of the fork legs;)
GS 1000: 775 mm
GS 1100 Kat: 800 mm
GSXR 1100 K: 745 mm
Bandit 1200: 775 mm
The ideal set-up is thus : GSXR 1100 K triple trees with Bandit 1200 fork legs.
The downside is that the Bandit components are not adjustable in compression nor rebound.
If you run with a 19" wheel the GSXR 1100 K legs will be long enough IMO.
 
Hi John, great write-up and photos about the fork upgrade, will be watching this one through to the end. Only problem is watching the price of B12 front ends climb now.

Cheers.
 
I can add some useful info.

Today I pressed the stem out of my 78 gs1000ec to press into my newly acquired 1999 bandit 1200 front end triples.:clap:

But, it is a smaller diameter:(. My machinist is going to fix it for me but hopefully this will clear up some confusions as it was mentioned that it should fit, we now know it does not.

I have read that an 1100e does press in though.

I will post pictures when the machining is complete.

Daryl
 
Fjbj40 said:
I can add some useful info.

Today I pressed the stem out of my 78 gs1000ec to press into my newly acquired 1999 bandit 1200 front end triples.:clap:

But, it is a smaller diameter:(. My machinist is going to fix it for me but hopefully this will clear up some confusions as it was mentioned that it should fit, we now know it does not.

I have read that an 1100e does press in though.

I will post pictures when the machining is complete.

Daryl
Click to expand...
It would be interesting to measure the exact offset of the B12 triples and compare it to the GSXR 1100 K?
If they are identical, we could use the lower triple from the GSXR with the upper triple of the B12 in order to avoid the clip-ons:cool:
The offset of the GSXR 11K is 43/2+25/2=34 mm
I've included the way I measured it as if you pull a string between the two legs between the triples it will just graze the stem!
 
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This week I got the caliper brackets back from the machinist.
There is one more pass to be done but here's what it looks like so far:)
The current plan is to fit this fork on my 1100 Kat:cool:

GSXRforkforGS1000002_zpsf79e4fd7.jpg


GSXRforkforGS1000003_zpsbe1070ba.jpg


GSXRforkforGS1000005_zpsd9f5704e.jpg
 
Simple is good. Can the inner dia. be bored to 17mm as well? That would open up even more wheel options.
 
mawg said:
Simple is good. Can the inner dia. be bored to 17mm as well? That would open up even more wheel options.
Click to expand...
Yes, you can go to 17 mm without any problem.
What you have to watch out for is the total width of the wheel at the spindle including the speedo drive.
For instance, if I wanted to fit an 18" GSXR wheel (these luckily came in both 15 and 17 mm diameter) I would have to modify the left hand bushing by deleting all or most of the protuding part making it a little more difficult to assemble as it has to be screwed in the bottom fork stanchion.
GS1000forkupgrade001_zps65dc8135.jpg


GS1000forkupgrade004_zps06f1715f.jpg
 
I made some progress today by fitting my modified GSXR 1100 K front fork on my GS 1000 ST.
The mudguard comes from a GSXR 1100 J I believe and matches the OEM 19" wheel rather well:cool:
To make it easy, I also used the instrument panel from a GSXR:rolleyes:
FourcheGSXR11K001_zps5b0ea1e4.jpg


FourcheGSXR11K006_zps29c8c899.jpg


FourcheGSXR11K002_zpsa5a06f17.jpg
 
Seems like a wasted opportunity to use stock brakes there John... I guess if yours were in good shape & the machining is not expensive then why not. :)
 
Hi Salty, the OEM brakes are obviously not in the same class as what can found on modern bikes today.
On the other hand the calipers that go with the slotted disks that appeared on the 1980 models are a big improvement over the previous generation.
That combined with modern pads that are properly bed-in give you appreciable stopping power at least in my view.
The purpose of the exercise was not to upgrade every part of the GS 1000 but only the front fork as I'm convinced that it's the weakest link on the bike.
Doing so, will also allow me to keep the bike relatively standard:cool:
If the next weakest link is the braking power, I will follow your example and go for the CBR disks and Kawasaki calipers;)
I'm still missing a few parts to complete the set-up but I'm eager to test it on the road, specially that with my extended GSXR fork, I will be able to try different ride heights with the corresponding changes in trail and rake:D
PS: if you'd like to produce the required parts for the GSR community, I'd be glad to provide you my drawings
 
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Why did you extend the forks if you are going to have 3 inches sticking out of the top tree? You do know that is a hazard on a get off.
 
althomas101 said:
Why did you extend the forks if you are going to have 3 inches sticking out of the top tree? You do know that is a hazard on a get off.
Click to expand...
I extended the fork for a previous project when I was using 17" wheels on my GS 1000 XP.
With the 19" wheels, I should be able to do without the fork extensions but I won't take them off until I do a back to back test between the two wheel sizes:cool:
I agree that it's dangerous to have the tubes protude above the triples...but it's even more dangerous to run out off ground clearance:rolleyes:
Here's what the ground clearance looked like with the 17" wheels.
87d6d2b9.jpg
 
I figured you had your reasons, I just wanted to know them. Thanks for the reply, I can see myself upgrading suspension down the road so this is of particular interest to me.
 
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