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Old 06-26-2013, 12:56 PM   #1
DRONE OP
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120/70-R19 on a GS rim - Yay or Nay?

The new Metzeler Karoo 3 front tire is available in the standard size for a 2-1/2" GS rim which is of course a 110/90-R19. But it's also available in a 120/70-R19 designed for the 3" rims used on the new water-cooled GS.




Note that in the above pic--which appears to be an "official" photo from Metzeler--that looks like they got a 120/70 on the watercooled GS 3" rim.

From the Metzeler website--
Innovative belt structure, with a single ply of steel cords wrapped at 0 around a radial carcass. Patented technology by Metzeler for both front and rear high performance tyres. Steel features a higher stiffness than the traditional textile material used and also reduces tyre weight. A steel belted radial reduces the dynamic deformation of the tyre under centrifugal forces giving the tyre excellent high-speed stability. Steel is an excellent conductor, therefore providing a more uniform heat distribution which allows higher mileage and wear characteristics are more uniform.
If I can get the 120/70 to hold its bead on my hack, it would give me a little wider footprint and about 4mm more clearance between the tire and the mudguard.

But the big question is if it will hold the bead. I'm not worried about it in the dirt--it'll slip before it'll bust the bead. But on pavement when I'm putting lots of lateral force on the tire carcass (lateral force that we know moto tires are not designed to handle) I'm wondering if squeezing it down onto a too narrow rim will cause the bead to break resulting in a sudden loss of air pressure. Or am I gonna be OK?

Yay or Nay?
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Old 06-26-2013, 05:14 PM   #2
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Given that you've got a BMW front wheel which is more or less a safety bead and a SOB to mount tires on if you can get one on it will be fine.DB


http://www.advrider.com/forums/showthread.php?t=481088

From Snowbum the most verbose sidecarist in the country http://bmwmotorcycletech.info/section6.htm Don't be intimidated you just need to read the last rim stuff.
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Old 06-26-2013, 07:53 PM   #3
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Dave, you continue to amaze. I don't know how you keep all these factoids in your head and accessible! You're like Crater Lake. You look shallow, but you are very very deep.

Not being an old-time motorhead, I've never heard of a safety bead before. But I can attest that I've broken the bead on my rig once in the past--it was on a very twisty road in moderate temps that I ran at moderate (25-35mph) speed with a moderate load (no camping gear or passenger). The tire remained in place, however, no nasty crash, and I was able to pull over and air up like nothing had happened. Kind of a mystery why it happened really. But I guess that safety bead kept the tire in place.

Any other voters?
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Old 06-27-2013, 04:45 AM   #4
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I would try it in a NY minute but Karoo's are not known for mileage but since this is the new Karoo probably designed for the water boxer, it's hopefully better.
My experience comes from mounting my own tires GS wheels are a pain compared to anything else.DB

In an effort to piss everyone off you'd have done better asking this question on a straight GS forum, there's not allot of info here regarding such things. I could start a rant here but won't.DB
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davebig screwed with this post 06-27-2013 at 06:23 AM
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Old 06-27-2013, 08:32 AM   #5
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Quote:
Originally Posted by davebig View Post
I would try it in a NY minute but Karoo's are not known for mileage but since this is the new Karoo probably designed for the water boxer, it's hopefully better.
My experience comes from mounting my own tires GS wheels are a pain compared to anything else.DB

In an effort to piss everyone off you'd have done better asking this question on a straight GS forum, there's not allot of info here regarding such things. I could start a rant here but won't.DB
I don't think they understand about lateral forces on the sidewall in a fast left-hand sweeper.
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Old 06-27-2013, 07:07 PM   #6
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Quote:
Originally Posted by DRONE View Post
I don't think they understand about lateral forces on the sidewall in a fast left-hand sweeper.
Come on Drone that can't be a real concern, you may have too much information to be a sidecarist, At what point does caution become neurosis ?
a little Twain :“A man cannot be uncomfortable without his own approval.” ~ Mark Twain
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davebig screwed with this post 06-27-2013 at 07:15 PM
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Old 07-01-2013, 08:22 AM   #7
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Spoke to a guy this weekend who pointed out that the 120 is actually NOT shorter than the 110. I said, "What do you mean? Here's the spec's!" He said, "Yes, those specs say the 120 is shorter but that's when the 120 is mounted on the 3" rim it was designed for, and the 110 is mounted on the 2.5" rim. When you squeeze the 120 down onto the 2.5" rim that will cause the carcass to bulge out more."

Hmmmm. That actually makes sense!
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Old 07-02-2013, 05:52 PM   #8
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Not sure if I should call someone or just be very concerned.

I very much enjoy the tire debate but usually the sides (issues) are better defined...
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Old 07-04-2013, 06:16 PM   #9
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One more reminder ! You were'nt going to be a Uralista, if your really concerned about front traction and tire loads finish the dog damn rig ! You have a compromised front end, build a leading link and run a tire the same size as the rear, get a sway bar and redisribute the load. How much longer do you plan on riding ? You could just be getting started, sell the Guzzi start another rig keep it light, use LL forks get a swaybar take a chance, Whatever happened to the interesting adventurer Drone that the Queen Bee married ??????
No really I'm not beating up on you, why not get a LL fund started, they are stronger and you can get as much tire as you want.By now you know allot more about this whole sidecar adv and that they are all fairly compromised vehicles.DB
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