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Thread: '03 K1200GT: To "B" or not to "B", that is the question

  1. #1
    Registered User txmxrider's Avatar
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    '03 K1200GT: To "B" or not to "B", that is the question

    Sorry, I couldn't resist the pun.

    I'll be looking at a new set of Michelin Pilot Road 3 in the spring and am considering getting the B-rated tire for the rear but I can't find any load rating information about the tire. I have the standard tire on the rear now but always run it at maximum pressure (42 psi) when riding two up and the bags loaded. The standard tire is rated at 805 max pounds at 42 psi. For rough calculations I took 1/2 of the bike's weight: (650/2) 325#, my weight with gear: 170#, my wife's weight with gear: 185 (just a guess because she won't tell me), and about 30# of crap in the saddlebags. All that comes to 710 lbs which is within 11-12% of of the max load rating of the standard tire and I want to have at least a 10% margin for safety (805x.10=724.5). So in my opinion I'm operating at the upper limit of the standard tire. The Michelin website does not provide the load rating for the B tire and the local shop had no information and no tire on hand for me to look at. Fwiw, the standard tire is $167 and the B-rated tire is $224, a significant premium, but probably worth the extra cost in peace-of-mind if nothing else.

    Does anyone here have a PR3 B-rated tire in 180/55-17 and if so, would you do me a favor and provide me with the load rating stamped on the sidewall? Also curious if there is a rule of thumb for the number of pounds of load at which one should upgrade from the std to the B?

    Thanks for your considered response!
    txmxrider
    2004 KTM 300 EXC
    1999 BMW R1100S
    2003 BMW K1200GT

  2. #2
    Ken ken e's Avatar
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    txmx,
    Dont forget about the front tire. All the load transferes up front when brakeing. If you go B, I would change the set.

    Have you tried contacting Michelin customer service?

    I had a set of Bridgestone BT023 B's on the RT. They were much heavier, stearing was slower, mileage was about the same, and harder to mount/remove by hand. I ride mostly solo, with only 1 or 2 trips a year 2-up heavy so I went back to the standard load rating tires. YMMV.
    Ken E.
    2012 R1200RT
    '09 RT, '93 K75, '69 R60US and others long gone....

  3. #3
    Registered User txmxrider's Avatar
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    Quote Originally Posted by Ken E View Post
    txmx,
    Dont forget about the front tire. All the load transferes up front when brakeing. If you go B, I would change the set.

    Have you tried contacting Michelin customer service?

    I had a set of Bridgestone BT023 B's on the RT. They were much heavier, stearing was slower, mileage was about the same, and harder to mount/remove by hand. I ride mostly solo, with only 1 or 2 trips a year 2-up heavy so I went back to the standard load rating tires. YMMV.
    Ken,

    Thanks for the response. According to the local shop only the rear comes with a B load rating, for PR3 anyway. Interesting that Bridgestone has it available front and rear. Fwiw the std PR3 front is rated at 520 lbs max load. I can only speculate what the total weight ratio is front to rear when fully loaded with a passenger, but doing a quick calculation here I see that the standard front is rated about 35% lower than the rear, so I'm going to make a stab at it and say 65/35. That made me rethink my original numbers. If I take a total weigh for the bike of 650#, add me at 170#, wife at 185# and luggage at 30#, the total is 1035#. If I split that 65/35 I come up with approximately 673 lbs of load on the rear and 362 lbs of load on the front. Both numbers are well under the max load rating of the respective tires. Not sure if that is anywhere close to accurate but it was fun calculating! Funny how I never gave this much thought before.

    You have an interesting point about load transfer under braking. My guess is that unless the bike is grossly overloaded weight transfer under braking would be a brief (but serious) consideration relative to all-day loading on the rear. Good suggestion about contacting Michelin customer service. I may do that depending on what data my friends here on the forum provide.
    txmxrider
    2004 KTM 300 EXC
    1999 BMW R1100S
    2003 BMW K1200GT

  4. #4
    Debbie's Servant Lee's Avatar
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    My wife and I both had a 03 K1200RS and never ran the B rated back tire. If we were riding two up on that same bike, I probably would have used the B rated tire.
    Lee 2011 K1300S
    MOA # 30878
    Past BMW Bikes, 2003 K1200RS, 1991 K75S, 1987 K75T, 1984 R100RT

  5. #5
    NC Piedmont Rider ncstephen's Avatar
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    I talked with Michelin about this. The tire load range is the same. It is designed for bikes that have an initial higher weight that it will be carrying all the time. So the sidewalls are stiffer. It was for the rear only. If a tire manufacturer feels the design specs of the bike are such that this will give the best overall performance, why would you disagree?

    Similarly when going to a sportier tire, I ended up with Dunlop Q2s as they are overall a stiffer tire than others in the niche. That was what was recommended for the very same reason. The bike is HEAVY. Will others work that are the standard non "B" version? Yup they will and do just fine. I would think you want the optimal tire for your conditions however. And extra 20 or so bucks for this over 8,000 - 10,000 miles isn't much. Most likely you would not feel much difference. Yet when something extra was needed: cornering forces, a pot hole, a severe rough patch in a turn, I would think you would wish the tires to be inside their design perimeters.

    Then again, if all your riding is unloaded to lightly loaded and solo and you are of average weight, then the non B should be fine. With those stats you aren't approaching the design limits of the bike.

    NCS
    03 K 1200RS (Black is Best)
    03 Honda RC51
    74 Honda CB750 K4

  6. #6
    Registered User txmxrider's Avatar
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    Quote Originally Posted by NCStephen View Post
    I talked with Michelin about this. The tire load range is the same. It is designed for bikes that have an initial higher weight that it will be carrying all the time. So the sidewalls are stiffer. It was for the rear only. If a tire manufacturer feels the design specs of the bike are such that this will give the best overall performance, why would you disagree?

    Similarly when going to a sportier tire, I ended up with Dunlop Q2s as they are overall a stiffer tire than others in the niche. That was what was recommended for the very same reason. The bike is HEAVY. Will others work that are the standard non "B" version? Yup they will and do just fine. I would think you want the optimal tire for your conditions however. And extra 20 or so bucks for this over 8,000 - 10,000 miles isn't much. Most likely you would not feel much difference. Yet when something extra was needed: cornering forces, a pot hole, a severe rough patch in a turn, I would think you would wish the tires to be inside their design perimeters.

    Then again, if all your riding is unloaded to lightly loaded and solo and you are of average weight, then the non B should be fine. With those stats you aren't approaching the design limits of the bike.

    NCS
    NCS,

    Thanks for the info. I agree, it's not that much more money and when amortized over the course of many thousands of miles the extra cost is pretty much inconsequential. Hard to judge how the stiffer sidewall affects cornering but it seems to me it would be better. The tradeoff might be a rougher ride though. Still, when loaded up and hustling through the twisties, it's one less thing to worry about.
    txmxrider
    2004 KTM 300 EXC
    1999 BMW R1100S
    2003 BMW K1200GT

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