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

[John Kat]

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
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

[Dogma]

Very interesting. What work is required on the triple clamps?

[John Kat]

Very interesting. What work is required on the triple clamps?

The triple clamps I use come from the GSXR 1100 K ( 1989) that drop right in!
The lock stops have to be added
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.

[GregT]

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.

[slayer61]

The triple clamps I use come from the GSXR 1100 K ( 1989) that drop right in!
The lock stops have to be added
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.

I am watching this thread closely! I have a similar swap in mind. In an attempt to upgrade me ES with "period improvements" 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]

How long are they John?

[John Kat]

How long are they John?

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.

[Shin-Ken 1074]

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.

[salty_monk]

Thanks

[Fjbj40]

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.

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

[John Kat]

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.

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

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
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!

[John Kat]

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

[mawg]

Simple is good. Can the inner dia. be bored to 17mm as well? That would open up even more wheel options.

[John Kat]

Simple is good. Can the inner dia. be bored to 17mm as well? That would open up even more wheel options.

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.

[John Kat]

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
To make it easy, I also used the instrument panel from a GSXR