35, 40 and 45 mm offset triples to fit GS 1000's with 43 mm cartridge forks

[John Kat]

I've upgraded a couple of my bikes to 43 mm cartridge forks sourced from a 1200 Bandit for my 1100 Kat, from a GSXR 1100 K for my XR 41 replica and from an R6 for my "Mocca Racer" replica.
The triples came from GSXR 1100 K's for the first two while I went for an R6 triple on the latter.
The issue with the GSXR triples is that they have only a 35 mm offset.
This offset creates more trail compared to the OEM triple that measures approximately 51.5 mm.
Using a 17" wheel partially compensates for that as you will see below:

GS 1000 with 19" wheel OEM spec: Rake 27°, Trail 116 mm
Same with 17" wheel : Rake 27°, Trail 96 mm
Same with GSXR triple (35 mm offset) and 17" wheel: Rake 27°, Trail 113.7 mm
This is not bad compared to OEM but nowhere near modern bike standards.
With the R6 triple (40 mm offset) and the same rake the trail goes down to 108.1 mm
Last but not least using Vstrom DL 1000 triples ( thanks @chuck78) that has a 45 mm offset you get 102.5 mm of trail.
The good news is that all these triples have the same center to center spacing of the fork legs at 205 mm so that you can use complete front ends from eitheir a 1200 Bandit, a GSXR 11K, an R6 or even a Vstrom DL 1000.
You will however have to modify the lockstops for all of these triples and the bearings for the R6.
I haven't used the Vstrom triples yet so I'll keep you posted.

The formula to calculate the trail is:
T=R/tan alpha-D/sin alpha

T: Trail
R: radius of the front wheel
D: triple offset
Alpha : 63° ( 90-27)
All dimensions in mm

Note that I have kept the rake identical for all examples i.e. keeping the bike level despite the the fork changes to make the comparaisons worthwhile.

[Nessism]

Yeah but how are you "...keeping the bike level...?" Aren't most of those modern bike forks shorter than the original forks?

[John Kat]

Yeah but how are you "...keeping the bike level...?" Aren't most of those modern bike forks shorter than the original forks?

You are right but dropping the front end decreases the rake and thus the trail.
One can typically gain 1° of rake by lifting the rear by 1/2 inch and lowering the front by the same amount.
Anyway here are a few measurements I took:
GS 1000: 775 mm
GS 1100 Kat: 800 mm
GSXR 1100 K: 740 mm
Bandit 1200: 775 mm
R6: 753 mm

Also on our older bikes the springs are typically weaker and the static sag is greater than what the measurements above seem to imply.

[mmattockx]

Last but not least using Vstrom DL 1000 triples ( thanks @chuck78) that has a 45 mm offset you get 102.5 mm of trail.
The good news is that all these triples have the same center to center spacing of the fork legs at 205 mm so that you can use complete front ends from eitheir a 1200 Bandit, a GSXR 11K, an R6 or even a Vstrom DL 1000.

This is the first I have heard of using the V-Strom front end on a GS. Does anyone have info on how GSXR or Katana wheels fit in the V-Strom forks? What about brake calipers?

Yeah but how are you "...keeping the bike level...?" Aren't most of those modern bike forks shorter than the original forks?

The Bandit and GSXR1100 forks are long enough, the DL1000 is a tall bike with lots of suspension travel so I suspect those forks will be long enough as well. I don't know about the R6 forks.


Mark

[John Kat]

IMG_0755.jpg

This is the first I have heard of using the V-Strom front end on a GS. Does anyone have info on how GSXR or Katana wheels fit in the V-Strom forks? What about brake calipers?




The Bandit and GSXR1100 forks are long enough, the DL1000 is a tall bike with lots of suspension travel so I suspect those forks will be long enough as well. I don't know about the R6 forks.


Mark

It's quite easy in fact to get the GS 1000 wheels in a GSXR / Bandit RSU fork.
Here's how it's done: https://www.thegsresources.com/_foru...t-wheels/page4
I don't recommend the GSXR 11K forks in a GS 1000 as they are the shortest at 740 mm.
Go for the Bandit 1200 at 775 mm.
I've used them for my 1100 Kat.
And here with the calipers in place:

https://www.thegsresources.com/_forum/showthread.php?206668-A-modern-fork-upgrade-for-17-18-and-19-quot-wheels/page3

Here's a picture of the Vstrom triple

[mmattockx]

It's quite easy in fact to get the GS 1000 wheels in a GSXR / Bandit RSU fork.

I don't want the GS wheels, if I were to go to the trouble of working up new forks I want to also get fat 17" radials and big brakes at the same time.


Mark

[John Kat]

I took a closer look at the Vstrom triples and the stem on the lower triple is definitely too long to go on a GS 1000.
While it is possible to shorten it, I'm not sure there would be adequate support left for the top bearing?
In any case the inner diameter of both bearings is 30 mm.
The best solution could be to replace the stem with one from a GS 1000?
I'd appreciate any advice on how to do this?

[mmattockx]

The best solution could be to replace the stem with one from a GS 1000?
I'd appreciate any advice on how to do this?

If the stems are the same OD where they go into the bottom triple you should be able to press the GS stem out of the GS triple and then press it into the V-Strom triple. If not, then you are most likely stuck with making a new stem.


Mark

[Fjbj40]

If the stems are the same OD where they go into the bottom triple you should be able to press the GS stem out of the GS triple and then press it into the V-Strom triple. If not, then you are most likely stuck with making a new stem.


Mark

No need to make a new stem. I pressed the stem out of my 1000 lower, welded it up, had it turned for an interference fit into the bandit lower and it works just fine!

[John Kat]

If the stems are the same OD where they go into the bottom triple you should be able to press the GS stem out of the GS triple and then press it into the V-Strom triple. If not, then you are most likely stuck with making a new stem.


Mark

I pulled the stem out of the lower Vstrom triple and I'm almost sure it can't be reused as the bearing landings are further apart than on the GS 1000.
Furthermore, there is not enough matter left below the top landing to move it downwards...
On top of that I don't see how I could use a GS 1000 stem as the top triples are attached differently between the two bikes.
Maybe that an R6 or GSXR 11K stem would fit (they do but fitted with their own triples) so in the end it could come out cheaper and faster to have a new one made?

[Chuck78]

I wonder if the VSTROM stem is a taller version of the GSXR/Hayabusa stem that I have??? They looked identical, 30mm bearings top and bottom, alloy anodized stem. I'll confirm when I return from being out of town, but the alloy GSXR/Busa stem seemed to be a great height for a GS frame.

I've been meaning to buy a VStrom DL1000 stem to investigate this.

My greater quest was to do minor machining to this GSXR stem in question to fit to a 93+ VMAX 1200. 55mm offset, will work fantastic with an 18" or 19" rear wheel with near stock front ride height and slightly taller rear shocks! Of course you will need some axle adapters turned up as John Kat has shown and has shared engineering drawings of previously...

It is a scarce bearing size, but you can also find a 20mm i.d. bearing for the GS hub, and make custom bearing and axle spacers and run a late 1980's GSXR speedometer drive modified to fit the GS hub interface. This mostly pertains to running wire spoke wheels unless you are running GS1150 rear mags or early GSXR double 3 spoke mags (all options for better performance oriented widths with 18" front and 17 or 18" rear wheels).

[Chuck78]

If the Strom stem is a bit too tall, had you considered shimming underneath the lower bearings 5mm-7mm or so to bring the upper bearing location down lower?


If you can please post a photo of this stem in question with a ruler or tape measure next to it, that would help clear up this question of length that has arisen, and may allow you to simply swap this other almost identical GSXR stem in place to fit.

[Dozer83]

Hopefully I'm not stepping on toes, but from what I think I am reading in this thread, the simple answer to all these questions is.... www.allballsracing.com
They will provide you with any bearing you need to fit just about any complete front end you can imagine to bolt up to your GS. I used them to fit a 1999 Hayabusa front end on my 1985 GS1150. Simply press the bearings on, and bolt the triples to the frame.

[Chuck78]

Bearing conversions are a different matter here, that's a given, a non-issue. The stem height is the issue.

From browsing ebay, it looks like later VStrom 1000's use a steel stem, earlier VStrom models use the aluminum stem that appears VERY similar to the Hayabusa stems I've had in my hands, which seemed identical to the GSXR stems that I have here for retrofit into 93+ VMX12 (V Max 1200) triples.

[Rijko]

answering to an old but interesting thread for the sake
of those interested : Allballsracing sells kits including a
spacer that goes under the lower bearing.

My buddy just installed a standard Bandit 1200 fork
in a GS1000 frame using this kit.