BMW G650XChallenge FRONT SUSPENSION

[Rider of the North]

This is one of the things that i am going to do over the winter,just a "pita" to try to get an answer from Twalcom.

[MotardParisien]

Originally Posted by Rider of the North

Twalcom in Italy offers the Ohlins TTX cartridge for the 800 GS and also for the HP2.
Correct me if i am wrong,as far as i know the fork on the HP 2 and the X Challenge are the same.
Ergo that should work.

Are these forks exactly the same (travel, preload, etc...)? If there are, I just have to steal Santa Claus for the 1500$

[Colebatch]

Originally Posted by MotardParisien

Are you trying to say to me that nothing can be done for this fork but changing the springs/oil??

correct. Thats why we have a whole thread here about changing the forks :)

[Colebatch]

Originally Posted by MotardParisien

Are these forks exactly the same (travel, preload, etc...)? If there are, I just have to steal Santa Claus for the 1500$

Be careful ... HP2 forks are also crap. They have better stanchions (same size) ... but thats about it. Anyone who races HP2s changes them either for better Marzocchis or does a full WP transplant.

PS guys, dont get confused between HP2 the motorcycle (crap forks) and HP2 the name of an ADVrider who did a successful marzocchi shiver transplant (good forks) onto his Xchallenge

[pampaX]

here I go again, the WP of my Ktm300 have the same size on upper and lower triple clamps as well as overall length. I'm unsure about size of axle. Would this be a suitable possibility?

[MotardParisien]

Originally Posted by Colebatch

Be careful ... HP2 forks are also crap. They have better stanchions (same size) ... but thats about it. Anyone who races HP2s changes them either for better Marzocchis or does a full WP transplant.

PS guys, dont get confused between HP2 the motorcycle (crap forks) and HP2 the name of an ADVrider who did a successful marzocchi shiver transplant (good forks) onto his Xchallenge

Ok...

Twalcom sells Marzocchi shiver cartridge, but for the HP2 fork, so, if I understand, it's not sure it will fit on mine...

[Colebatch]

Originally Posted by pampaX

here I go again, the WP of my Ktm300 have the same size on upper and lower triple clamps as well as overall length. I'm unsure about size of axle. Would this be a suitable possibility?

I didnt answer because I dont know the answer .... But if you need answers from people who dont know, then I will throw something out there. No guarantees. Thats my disclaimer

I dont know much about WP forks apart from the 48mm ones. So the WP forks you have have 54mm upper clamp diameter and 57mm lower? Sounds like 43mm forks ... I think thats the sizes of the old WP 43mm forks.

If yes, thats a third of the fitting issues sorted. The forks fit the bike.

You also have to figure out how to make the forks attach to the wheel. You wont be able to use the BMW axle clamps ... which screw onto 45mm tubes. So thats a problem.

Then you have to figure out how to make the brake disc and caliper fit the forks and wheel. This is the biggest problem.

I think the reason you got no responses is that probably no-one has tried using those forks on this bike - so no-one knows 100% what you are going to have to do to make it work. You should have a talk to LukasM ... he is lord of WP forks and fork fittings and brackets and will know what is possible.

Sounds like a major job to work out how to attach the wheel and brakes to me. You might be able to use your KTM axle clamps, wheel, and brakes, but you probably have to get a custom axle and spacers made up. The BMW and KTM triple clamps have the forks spaced differently, so your KTM axle and spacers will be too short to use with the BMW triple clamps. As soon as you change the wheel spacers, you will then have to custom make a caliper mount. Because the caliper will be too far away from the centre of the wheel with wider BMW triple clamps.

You should also check the offset of the KTM axle clamps, compared with the BMW offset. You dont want much difference there.

Can you confirm the exact upper clamp size on your forks in mm (54?), the lower clamp size in mm (57?), and slider tube size, in mm? (43?)

[LukasM]

If they are 54mm on top and 57mm on the bottom they will be 4357MXMA forks aka 43mm USDs. They should have a 20mm axle and 95mm caliper bolt spacing, so the same as the later WPs. Obviously not as plush or strong as the newer stuff but they can be made to work pretty good.

[Dukehunt]

Progress made today, wheel spacers back from the machine shop, -2mm on brake caliper side, 2mm spacer made for left hand side, brake caliper now mounted and all lines up correctly, centre of wheel is now in the centre of the forks (hopefully that is the centre of the bike)
So in the morning (whilst I am working) I'll get a UHD tube and my D606 fitted up and hopefully by mid afternoon I'll be test riding.

Then the suspension tuning starts, I will go back to standard front and rear (rear is an ohlins) and make the adjustments one at a time.
First weekend away on the 27th-28th Nov to the NSW XMAS bash so will have some tar, easy dirt roads to start the fine tuning with.

[Cruz]

Originally Posted by Rider of the North

Twalcom in Italy offers the Ohlins TTX cartridge for the 800 GS and also for the HP2.
Correct me if i am wrong,as far as i know the fork on the HP 2 and the X Challenge are the same.
Ergo that should work.

I have replies from most suspension shops around the world.

Here is the one from Twalcom.

Hi Cruz,

Apologies for the slow response. The only thing that Bitubo does (or at least lets up import) is a replacement spring setup for the G650X Challenge. It's up now on TwalcomUSA.com


Rob

Robert Werksman
Motorcycle Insight, LLC.
1-412-226-6778

1500 Ellsworth Ave
Suite 107 D
Heidelberg, PA 15106
USA

and this one from bitubo in Italy.

Dear Cruz, I’m sorry, nothing for this bike at the moment.

Regards Giorgia.

[Colebatch]

Originally Posted by Cruz

Hi Cruz,

He calls you "Cruz"?

[Cruz]

No Colebatch, just subbed my name out for online name.

Also had negative responses from Marzocchi Italy and GB, db race suspension, Traxxion Dynamics, YSS.

[Colebatch]

Originally Posted by Cruz

No Colebatch, just subbed my name out for online name.

Also had negative responses from Marzocchi Italy and GB, db race suspension, Traxxion Dynamics, YSS.

Only solution is fork transplants as far as I can see.

In summary - what do we know so far about the front suspension of the XC:

(1) stock forks are crap-a-rooni - one features mild compression damping, and one features mild rebound damping ... neither at full adjustment provide sufficient damping for the bike as a whole. The stock stanchions are also strongly rumoured to be a little on the soft, bendy and overly flexible side.
(2) nothing can be done to the stock forks apart from changing springs and weight of oil - despite many once promising leads.
(3) fortunately Marzocchi 45mm shivers will (sometimes) fit both the stock triple clamps and axle clamps so that transferring them over is relatively painless.
(4) some Marzocchi 45mm shivers need the bottom triple clamp region machined down to 57mm, some dont.
(5) to get compression damping access on transplanted shivers, you will need to drill an access hole in the bottom of the stock axle clamps.

[Cruz]

Originally Posted by Colebatch

Only solution is fork transplants as far as I can see.

IF Marzocchi would sell you replacement cartridges to fit, the cost quoted to me was over $1000 per side, but they indicated that they were not interested for some reason.

Which is why we buy up new or used 45mm Marzocchis on the net to refit the oems or modify them to fit our bikes.

I also tried fitting the complete front end off of a CRF450 Honda and the axle is the correct size and so are the head bearings. You need to either make up a spacer for the top of the steerer or have it shortened by about 2 cm to make it fit. Then mod someing up to mount the dash, headlight and on/off switch. the triple clamps are not as wide either and fouled the frame either side on full turn. Someone with a lathe or cnc machine could easily make these forks fit.

[Colebatch]

Originally Posted by Cruz

IF Marzocchi would sell you replacement cartridges to fit, the cost quoted to me was over $1000 per side, but they indicated that they were not interested for some reason.

Yes ... for that money ($2000), you could have a very well sorted front end with completely different forks - considerably better than 45mm shivers.