Car tires on rear

[chiba13]

Glad to see this thread pop up, some good solutions here.

We (me & my trusted mechanic) put a 195/45R17 on my stock rear K1200RS wheel. It was a real bear to get on, but it seated perfectly fine & haven't had a problem with it in over a year of it being on there. The stability of the rig went way up, but the speedo is off a solid 10% above about 25-30 mph.

I had the opportunity to check the odometer parallax with a GPS this past weekend - at 244 on the bike's tripmeter, the GPS only registered 187 miles! According to my rudimentary math skills that's a 1:1.3 variation. It's somewhat for this reason that I'm thinking of getting Claude's rear wheel adapter, plus one benefit of that is having more choices of tires to run on the rear.

As far as fit went, we tried several tires, 215, 205 & 195. The 195 was the widest that would fit without rubbing the swingarm, muffler or both. My mechanic suggested using the spacer from a K12LT to get a little more clearance from the swingarm, but that didn't necessitate using longer bolts to secure the wheel.

I've been keeping my eye out for an R12CL wheel or even a 5.5" wide 17" diameter BMW wheel - they used the same bolt pattern on several 17" wheels.

PS Claude did an amazing job putting my rig together ... can't thank him enough!!

[Bobmws]

Hey Chiba,
I've hit your original thread on ADVRider when I was first looking for a hack.

I don't think the R12CL wheel is the same pattern, but I could be wrong, not the first time! That would be too easy! Grafik Feat is using a 15" tire on his R12C rim.

I took my rig to the GA Mountain Rally in May, a bit over 1200 miles. Like you , my speedo is a solid 10% optimistic vs the GPS. I also measured my odometer against the mile marker indicators on the interstate, fairly straight line runs. Three 100 mile comparisons show it is reading about 5% high, I registered 105 miles each posted 100 mile stretch. Keep in mind the GPS measures straight line points, that would account for the variance.

Like yours, the tire was a bear to mount. I do have the 5.5" rim and had to use 3 additional 2mm spacers to clear the swingarm, and I used the 5mm longer lug bolts from the R12C. All the BMW K spacers are listed as 2mm thick, I didn't find any variation in different models.

I did find that the tire grew with heat on that trip, and just barely touched the swingarm, enough to leave a shiny spot on the rubber, but not enough to feel a ridge. It was right on the outside corner of the tread, so I hit it very lightly with my air sander to gain clearance. I'll see how this setup works before going with an adapter and car wheel.

[grafikfeat]

45/17? Can you go taller on the tire? That will get you closer on true mileage. You have clearance for a 50 or 60?

I had the opportunity to check the odometer parallax with a GPS this past weekend - at 244 on the bike's tripmeter, the GPS only registered 187 miles! According to my rudimentary math skills that's a 1:1.3 variation. It's somewhat for this reason that I'm thinking of getting Claude's rear wheel adapter, plus one benefit of that is having more choices of tires to run on the rear.

As far as fit went, we tried several tires, 215, 205 & 195. The 195 was the widest that would fit without rubbing the swingarm, muffler or both.

[Bobmws]

45/17? Can you go taller on the tire? That will get you closer on true mileage. You have clearance for a 50 or 60?

The problem is that the swingarm, at least on the K12, has a fairly short radius to the shaft housing. it actually looks like more mateerial was cast in that corner for strength. That is where the corner of the tread hits. There is more room in the center of the swingarm space for a taller tire, but the flat profile of the car tire hits the swingarm corner. I haven't found any narrower 17" tires that might be taller to try. If you look atthe pic in my post #10 in this thread, you can see the clean spot on the corner of the swingarm where the taller tire hit.
I don't have an issue with the speedo readings, my one concern is that the only tire in this size is the Yokohama, and that could be a potential problem if I have to replace it on the road. Push comes to shove I could always remount a bike tire in that situation.

Hey GF, if you get a chance could you measure the bolt pattern on your R12 rear wheel, the distance between the lugs? The K uses a 5th bolt in the center, but I don't think the 4 bolts on the R12C are the same pattern as on the K. I suspect they may even be different from the GS bikes, or we would see them using that wheel for a car tire instead of the adapter to fit a car wheel.

[GTRider]

Do you remember how thick the adaptor is?

What brand/model of wheel are you using? I like the looks of it much better than the wheel I'm running with my adapter!

Thx,

GTRider

[Bobmws]

What brand/model of wheel are you using? I like the looks of it much better than the wheel I'm running with my adapter!

Thx,

GTRider

I think you are referring to Mike Currins wheel, it's from a Mini Cooper, 16".

[grafikfeat]

Hey GF, if you get a chance could you measure the bolt pattern on your R12 rear wheel, the distance between the lugs? The K uses a 5th bolt in the center, but I don't think the 4 bolts on the R12C are the same pattern as on the K. I suspect they may even be different from the GS bikes, or we would see them using that wheel for a car tire instead of the adapter to fit a car wheel.

I know guys do use the 5.5 K/RS wheels... Only issue was a spacer...
I believe they're the same.
Take a look here:

http://www.chromeheads.org/discus/me.../6/438463.html

[Bobmws]

I know guys do use the 5.5 K/RS wheels... Only issue was a spacer...
I believe they're the same.
Take a look here:

http://www.chromeheads.org/discus/me.../6/438463.html

OK, very interesting. What size tire are you running?
I see the cast wheel is listed as 15x4, the same size as used for the car wheel conversions. Since one has to use spacers with the swap to a 17" rim, I wonder is the backspace on the R12C rim will work without spacers on the K?
I already have the 60mm lugs, have to get ahold of a wheel and measure/test fit.
I'd have to guess there is a reason this swap is not being used.

[grafikfeat]

OK, very interesting. What size tire are you running? I'd have to guess there is a reason this swap is not being used.

Why is a personal thing. Perhaps many don't know about the swap or just dont care... Or can't find used and don't want the expense of new... Regardless... Many are happy w/ a 15" rim which is what I'm using.
190/75/15... I was going to try the rim swap for the 17" GS tire market on really bad snow days. I also found out that alloy rims are less forgiving than spoked/tubeless so I jacked the bike up 2" via the rear shock. So now I'll try a more aggressive car tire AND also have room for chains. As I noted earlier I'd rather have more rubber than rim. I really don't like that look of low profile tires on anything. Again. My preference.