Adventure Supermoto

[Nick V]

Fair point about doing this on a budget, but my other consideration is I don't like the offset rear wheel on principle. And the full conversion is 2 wheels plus a new exhaust as the standard one doesn't have clearance for the wider tyre. Agree that 120 front and 180 rear is a good combo and gives loads of choice.

Ps not doing this for the looks of it, just want the handling, and lower seat height is a bonus as well.

As was mentioned earlier in the thread, nearly all BMW rear wheels are offset to some extent.
But the K-series rear wheels give a great deal less offset - so little, in fact, that you can't see it from the back. By contrast, the offset of R1200S/ST/R/RT wheels on the GS is so obvious that it actually looks a bit scary.

An idea: using R1200R Classic wheels would allow you to do something the alloys wouldn't - a competent wheel repairperson could 'counter' any unwanted offset, merely by adjusting left/right spoke tension to bring the outer rim back into line.

Anyone concerned about offset could theoretically use this approach to get the rear wheel alignment perfect!

 

[Greenman14]

As was mentioned earlier in the thread, nearly all BMW rear wheels are offset to some extent.
But the K-series rear wheels give a great deal less offset - so little, in fact, that you can't see it from the back. By contrast, the offset of R1200S/ST/R/RT wheels on the GS is so obvious that it actually looks a bit scary.

An idea: using R1200R Classic wheels would allow you to do something the alloys wouldn't - a competent wheel repairperson could 'counter' any unwanted offset, merely by adjusting left/right spoke tension to bring the outer rim back into line.

Anyone concerned about offset could theoretically use this approach to get the rear wheel alignment perfect!

So the K series wheels are going to have less of an offset than the R series? Nick's first post on this thread said the R series would have less offset?

 

[Nick V]

So the K series wheels are going to have less of an offset than the R series? Nick's first post on this thread said the R series would have less offset?

My original comments were:

This is definitely the case if you're using a K1200S rear wheel. However, no one has yet been able to tell me by how much the rear needs machining...

If you're using an R-series rear wheel, this shouldn't be the case; IIRC, they all use the same gearbox casing (or at least very minor variations thereof), so the rear wheel should remain in alignment.

And:

With a 5.5in rim, I would stick to a 180/55. If you're using a 6in rim, you can quite happily use up to a 190/50 or 190/55 if you want to - I've had no clearance issues on my GSA, using a 6in K1200S rear wheel with 190/55 tyre.
And: at no point has the centre stand touched the wheel or tyre.

And I see that you're right: my early notes didn't keep up with my later experience.

To clarify: since writing that, I'd built a second GSA 'moto using a set of R1200ST wheels.
My assumption was that since these wheels had come off an R-series and were being re-installed on an R-series, there was no real reason to assume that there would be noticeable offset.
In reality, the opposite was true: the K-series rear on my first conversion tracks more-or-less perfectly, but the ST wheel on my second is offset to the left by at least 10mm.

Why this should be, I don't know. Maybe the engine/gearbox assembly is offset to the right on S/ST/R/RT to compensate for a wider wheel?

 

[red line]

My original comments were:




Why this should be, I don't know. Maybe the engine/gearbox assembly is offset to the right on S/ST/R/RT to compensate for a wider wheel?

i think this is the issue, as there is no way my rear will move 5mm right, as its is about 5mm away from touching the swingarm.

 

[Nick V]

i think this is the issue, as there is no way my rear will move 5mm right, as its is about 5mm away from touching the swingarm.

The strange thing is that with the ST rear wheel on my Camhead, I can't feel any handling nasties that might come from excessive offset.

At wide-open throttle settings, very high speeds (i.e. 170 Km/h+) or a combination of these, the bike tends to start weaving. The weave is quite controlled, with a relatively gentle onset.
At the moment, the rear rim is wearing a 190/50-17 Michelin Pilot Road which is squared-off to the level of the centre tread-wear indicators. So we have two no-nos here - a tyre which is one size too wide for the rim, and with a nearly flat centre profile.

I really don't think the weave comes from the excessive offset.

 

[Greenman14]

I see that you're right: my early notes didn't keep up with my later experience.

To clarify: since writing that, I'd built a second GSA 'moto using a set of R1200ST wheels.
My assumption was that since these wheels had come off an R-series and were being re-installed on an R-series, there was no real reason to assume that there would be noticeable offset.
In reality, the opposite was true: the K-series rear on my first conversion tracks more-or-less perfectly, but the ST wheel on my second is offset to the left by at least 10mm.

Why this should be, I don't know. Maybe the engine/gearbox assembly is offset to the right on S/ST/R/RT to compensate for a wider wheel?

Thanks Nick. I just might get around to the conversion this winter, anyway I've decided that sticking with the original back wheel is a no-no. So that's progress.

 

[DING-DONG]

Geez bro you ain't put a 190 on a 5.5" rim ! That will do strange things to the profile and handle oddly, i ran 190 on my bst wheels but the rim is 6" all my other conversions have Been on 5.5" and 180 r12s rims, it never bothered me about the offset, and my bike was not just for show i used and abused it with trips to the ring and all around Europe thrashing the tits off it chasing sport bikes and not once did i notice the offset.

Id put money on it that peeps would not be able to tell the difference, its all in the head, just buy some r12s rims and plug and play.

Keep up the good work its nice to see you lot going against the grain and converting them to moto .

 

[Nick V]

Geez bro you ain't put a 190 on a 5.5" rim ! That will do strange things to the profile and handle oddly.

Er. If you saw that as advice on 'What to do' in this article, I didn't say it...! Promise.
Matter of fact, I quote it as an example of what NOT to do. The only reason that tyre was being used was because I was too mean to splash out on a new tyre just then. I actually put in an explanation of what that configuration will do (and has done) on my Camhead. (I admit that in this context, what I did could be described as a case of 'Do as I say, not as I do'... )

To reiterate for the sake of anyone who's just joined us: DON'T go wider than a 180-profile on a 5.5-inch rear rim. For 6-inch rear rims, you can comfortably go to 190-profile if need be.

Keep up the good work its nice to see you lot going against the grain and converting them to moto .

Ta, my friend.
You too, and thanks for the kind words!

 

[Nick V]

Taking advantage of my shiny new subscription, I thought I'd post a couple of piccies of what's gone on in the world of Nick.

The '10 Camhead (the green bike) is currently up on stands in my workshop. The wheels you see here are being replaced with the front and rear wheels from an '05 K1200S, in the same gold colour as from a big-bang Yamaha R1. The silver 'GS' side panels are being painted the same colour.

The rear Metzeler Racetec K2 on the blue bike wore out, and was replaced with a Pirelli Diablo Corsa SC3.

 

[DrAlf]

Looking good - I've been following your posts with interest Nick. Considering a move from an 1150 SM to a 1200 SM and been reading up. Keep up the good work.

 

[Nick V]

Looking good - I've been following your posts with interest Nick. Considering a move from an 1150 SM to a 1200 SM and been reading up. Keep up the good work.

Good man!

I'm busy working on a comprehensive manual for conversion of a GS/GSA to 'moto. It'll be released via the site as soon as it's ready.

 

[2 wheel humvee]

Blue bike looks really good Nick excellent work

 

[Yonkyo]

Thats a couple of neat conversions

I did the 17" SM conversion on my 1200GS a few years ago. It was a bit of novelty at the time, but i definitely wouldn't say it was an improvement.
the main problem was the reduced lean angle ground clearance, due to 17" front, as i didn't bother to compensate by increasing the ride height.

 

[APE]

Blue bike looks really good Nick excellent work

+1. That's the best looking GS SM conversion I've seen.

 

[Bendy toy]

The 2nd picture in post #93 shows a well tucked in exhaust can. It looks almost enough to take a full size side case. I know cases dont really suit an SM conversion but just saying,

 

[Dellis]

I really don't see what is going to be achieved by fitting a pair of 17" wheels. If you're after better handling/more grip that suggests you want to get round corners quicker and by fitting a pair of 17" wheels you're reducing ground clearance which was the limiting factor with my 12GSA and further reducing clearance would slow you down In fact my standard 1200 GS had better cornering clearance than my 12 GSA despite the fact that the GSA had more static clearance to start with but the softer suspension on the GSA compressed more readily reducing the cornering clearance.

Just my tuppence worth.

Dave

 

[Nick V]

Thats a couple of neat conversions

I did the 17" SM conversion on my 1200GS a few years ago. It was a bit of novelty at the time, but i definitely wouldn't say it was an improvement.
the main problem was the reduced lean angle ground clearance, due to 17" front, as i didn't bother to compensate by increasing the ride height.

Fangs mate. I would stress to anyone thinking of doing this that you've got to invest some time fiddling with the suspension settings. Both my bikes have ESA, and being limited to what the factory presets allow has limited the amount of fiddling I can do.
Playing with tyre profiles also yields dividends.

+1. That's the best looking GS SM conversion I've seen.

Ta! Much appreciated!

I really don't see what is going to be achieved by fitting a pair of 17" wheels. If you're after better handling/more grip that suggests you want to get round corners quicker and by fitting a pair of 17" wheels you're reducing ground clearance which was the limiting factor with my 12GSA and further reducing clearance would slow you down In fact my standard 1200 GS had better cornering clearance than my 12 GSA despite the fact that the GSA had more static clearance to start with but the softer suspension on the GSA compressed more readily reducing the cornering clearance.

Just my tuppence worth.

Dave

What's achievable depends on what you, personally, are after. For me, the biggest tangible benefit was quicker steering.
See above, but one thing that made a difference in terms of ground clearance was using a 190/55-17 on the rear. The taller profile does help.

 

[Nick V]

The comments about a 'tucked-in' exhaust can struck a note as well.
Some people (including me) find that if an aftermarket can is high-mounted and the bike is equipped with 'downward-offset' LED rear indicators, the left rear indicator can be damaged by exhaust gas heat.
The way to solve this is to remove the rear seat mounting panel, exposing the wiring underneath. From there, swap the left and right indicators around, mounting them using longer bolts and rubber tap washers. The left will now be offset upward, out of the way of exhaust gas.

(And for the technically curious: if your bike has RDC, and you've always wondered where the radio receiver for the pressure sensors is, you'll find it while you're there. )

 

[Nick V]

The refurbished 'turbine' wheels for the green bike came back a couple of days ago. So much for having them back before Christmas - but better late than never!

Note the close-up of the front wheel. This is not from an R1200S as per the blue bike - both these wheels previously did duty on my 2005 K1200S streetfighter. Modifications to the wheel and axle and a new axle spacer were required, but it was well worth it.

Tyres are 120/70-17 Pirelli Dragon Supercorsa Pro, and 190/55-17 Pirelli Diablo Supercorsa.

 

[ROC]

The S rear rim that SHOULD have joined it's front cousin and found it's way onto my '09 had quite a history, too...
Both rims went to a fellow in Boksburg who had a canary-yellow '09 GSA he wanted to 'Moto. The guy played around for a bit before doing the conversion with R1200ST rims instead. The rear was then returned, and installed on another bike which was sold. The front came to me, and joined the K1200S rear rim I already had on the bike...

The K rim complements the S front rim perfectly. If you're REALLY in the mood to niggle, you can tell it turns the 'wrong' way, but I'm not really fussed at all.

I thought the wheel was designed to rotate one way, the arrow mark on your rear wheel will now point to the rear, do you not think from a design/strength point of view that it is unwise to change this?