Feasibilty of Supermoto R12GS?...

[plasmatron]

I'm prone to having blinding flashes of inspiration which lead to expensive impulse purchases and overly ambitious plans, or as my wife calls them "bloody stupid ideas"...

so I suddenly had the idea of taking the spoked wheels that I've already got for the GS and putting either full offroads or dual purpose tires on them for offroad/enduro use, then, getting a set of 1200RT wheels slapping some BT014's in perhaps 120/70 and 170/60 sizes and giving my GS an optional supermoto mode...

as near as I can tell the RT wheels look very similar to the GS's size wise... and whilst the rotors on the RT wheels are 320mm compared to the GS's 305mm, it looks to me like the mouting tabs on the RT's rotors are taller and that the actual mounting location is the same, so assuming they aren't wider or something, they may just accomodate the GS's 305mm rotors just perfectly... then it's only a question of the width of the front wheel hub / spindle being close enough to the GS's and I'm fairly sure the rear is just a straight bolt on, perhaps needing the RT's shorter/longer bolts... it seems that the clearance off the swing arm should allow for the 170 rear, especially since the AC Schnitzer wheels for the GS use a 180 rear...

and there you have it... the 12GS supermoto, perfect for destroying the bumpy, super tight, low grip twisties that are 80% of local riding terrain... probably look pretty cool too IMHO... I know the purists are going to condemn me for all eternity for even suggesting this, but it's a matter of taking the ultimate allrounder and tweaking it for local conditions... and I get to muck about with some spanners...

Question is:

- how to cope with the 2" lower front ride height?

A: bolt a spacer into the top of the stock front shock mounting... not much room I'm sure...
B: Wilburs front shock with added ride height adjuster... perhaps custom length...
C: RT or ST stock front shock
D: ignore it and see how badly the increased rake/trail effects the handling...

 

[Deleted account 211025001]

I know the purists are going to condemn me for all eternity for even suggesting this, but it's a matter of taking the ultimate allrounder and tweaking it for local conditions... and I get to muck about with some spanners...

Question is:

- how to cope with the 2" lower front ride height?

A: bolt a spacer into the top of the stock front shock mounting... not much room I'm sure...
B: Wilburs front shock with added ride height adjuster... perhaps custom length...
C: RT or ST stock front shock
D: ignore it and see how badly the increased rake/trail effects the handling...

I'm obviously not a purist then 'cos I think it sounds a great idea and, if what you say is true about the wheel sizes, not toooooo hard to do.

Re the ride height I think option 'D' makes the most sense inititially and probably ultimatley.
The GS benefits greatly in the handling dept. from whacking up the preload (and thus ride height) to max so the idea of dropping the front, and putting more weight on the front sounds as if it ought to improve things still further. It certainly does no harm to the handling on an SM when going down from 21" wheels to 17" wheels- must be worth a try.

Andres

 

[walti]

The CCM "Dual Sport" changes from 21" to 17" wheels at the front for off road /road use, they make no changes to the suspension to cope with the diameter difference!

So I'd guess that changing from 19" to 17" front would be OK, and that'd only be a 1" change in height (half the diameter change)

Just give it a go... should be a hoot!

 

[TheJoker]

Hmmmmm.... as a previous SuperRetard owner I can't deny that this idea has occurred to me too...

Nooow... The reason a Motocross/Enduro bike gets 17" wheels when converting to a SM is basically two things:
1) Puny motocross brakes won't do it on tarmac
2) You can't get "sticky enough" rubber on 21" and 18" rims (AFAIK)
Therefore it's easiest to change to existing 17" or go to the box of bits and put on double disks and relace the wheel with a 17" rim.

The GS has, as far as I can push it, rubber that's sticky enough to scrape the engine bars on the ground - if I wouldn't have engine bars, I'm quite confident that I could scrape the cylinder heads. It's also got double disk (Brembo derived) brake set-up at the front. So IMFO there's no real need to change the wheel size.

If I'd start modifying my GS to be more SM-like I'd start with shedding weight; removing as much as I could. Maybe:
1) change all lights to light-weight ones
2) remove servo/abs etc and fit "standard brakes"
3) remove all plastics and fit "motocross" kit including lightweight tank
4) remove pillion pegs or even cut down rear subframe
5) Obviously removing screen etc.
6) fit lower bars (done that).
7) Remove heavy side and centerstand and fit a "barely-holds-it-up"-sidestand
8) fit lighter seat
9) etc..?!

Don't know how much that would shed, but I'd say quite a bit. I would probably also shed the standard exhaust and fit the ligthest one around. I think I'd keep the engine bars tho and fit more crash bobbins

If I'd change wheels, I'd probably change wheels to lighter wheels rather than to a specified size (they'd probably be 17" tho )

However, I still don't think that the handling and/or riding experience would change that much from a standard GS, so the bang-for-the-buck-factor is quite low on this one - hence I'm keeping mine standard I can't really see how you can get the GS to behave like "stick the tail out and slide sideways around a corner"...

If you do go ahead and fix yours; post pictures!

 

[Deleted account 211025001]

If I'd start modifying my GS to be more SM-like I'd start with shedding weight; removing as much as I could. Maybe:
1) change all lights to light-weight ones
2) remove servo/abs etc and fit "standard brakes"
3) remove all plastics and fit "motocross" kit including lightweight tank
4) remove pillion pegs or even cut down rear subframe
5) Obviously removing screen etc.
6) fit lower bars (done that).
7) Remove heavy side and centerstand and fit a "barely-holds-it-up"-sidestand
8) fit lighter seat
9) etc..?!

; post pictures!

Mmmmm......that'd be just like this one then

http://www.ukgser.com/forums/showthread.php?t=55830&page=2&pp=16

Andres

 

[TheJoker]

Now - *that* is tasty! But I reckon you'd still be better off with, say... a KTM990 SM, or even a "normal" KTM, Husaberg or Husky...

SuperMoto = FUN
SuperMoto = useless

 

[Franky]

I think the reduction in height will affect ground clearance as i've not got a engine bars but the brake pedal then centre stand are the limits of lean for me, if you're lighter than maybe the engine but i doubt it..... I do like the look of the 17" rims though, I reckon you could push the front a hell of alot harder...... do I buy an Akrapovic system or try a 17"conversion on the front..........

 

[GSmonkey]

Something like this maybe??:

 

[Shurv]

You beat me to it.Sounded like a supamoto HP2 would be the best bet

 

[ktmmark]

I have a late 1150 rs wheel ready to fit to my 1200 just had to mod the bearings will try it in the spring

 

[jnrobert]

Like this?

or

 

[plasmatron]

exactly... like the first pic sans oddball body work, those are RT wheels, the bike in the second pic looks to have the AC schnitzer wheels on it...

thanks for the pics and replies... of course you're all right, it'd only be a 1" drop in front ride height (maths was never my strong point... but 2/2=1 sheesh, you'd think I'd have got that one though)... which means that I agree that I could quite comfortably ignore it and just leave the suspension un modified and see how the new geometry effects the handling... it can't be all that detrimental since lowering the front by 1" could be done with the stock wheels by just cranking rear pre-load and setting the front shock to 0 preload clicks like Andres said...

also that fact that others (albeit Boxerdesign... gulp...) have done it means I'm even more confident that it shouldn't need too much modification to pull it off...

now time to find out how much they want for a set of RT wheels...

 

[Warthog]

Question is:

- how to cope with the 2" lower front ride height?

A: bolt a spacer into the top of the stock front shock mounting... not much room I'm sure...
B: Wilburs front shock with added ride height adjuster... perhaps custom length...
C: RT or ST stock front shock
D: ignore it and see how badly the increased rake/trail effects the handling...

If I'm not mistaken, the 1200GS has a 19" diameter front and the RT a 17". So, in actual fact the difference in radius from the hub would only be 1", not 2. This already makes things more manageable. I, too, am cursed with an urge to fettle whatever bike I have, much to the amusement of my friends and dismay of my girlfriend. However, I have previously changed front wheels, and in one case this was to SM a Honda Dominator. This was from a 21" to 17 and all I really needed to do was adjust the headlight which now illuminated about 2 feet ahead of me! A drop in front ride height speeds up the steering, so that your 1200GS should then tip into corners quicker. However, the fatter front tyre also slows down turn-in and steering, and so I think this would go someway to cancelling the ride height change. All in all, I suspect your GS will steer a bit faster than before, but not a ridiculous amount.

And rememer, you may not be able to mount curbs as enthusiastically as before the swap, if you want your bash plate to stay put!