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Front tire cupping


jackflash

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My Z6 front on my R1200RT is cupping significantly. I have been running 36# and my dealer said to up the pressure to 38#.

 

Does cupping really affect handling? I haven't noticed that it does in the twisties but then it may be since it doesn't cup right away. Does anyone else run 38# in the front tire? Sounds like a lot of pressure for a front but I don't quite know everything yet... confused.gif

 

Thanks,

 

JF

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My front on my LT cupped pretty damned bad after only 3000 miles and while handling isn't too bad at highway speeds, at lower speeds I cannot take my hands off the bars for even a moment due to handlebar slap. I do think if I was on a true sport tourer, I'd be really disappointed and a lot more pissed than I am now. It sucks bad enough on my LT and when i mentioned it to my dealer, the first thing they asked me was whether I regularly checked the tire pressure on the bike and let it run low.

Thankfully, I was smart enough to both purchase the firefly tire pressure warning caps AND regularly check the pressure with a good gauge so their "blame it on the rider" tactic fell flat, but it didn't matter, since they aren't going to replace the tire for me.

So, I'm just going to ride it until I can't stand it any longer and then when I replace it, I'll keep the pressure at 38 and see if it helps.

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Ummm--did I say that somewhere in there? I didn't intend it to come out like that. My point was that I'll probably run any tire on the front a couple of pounds higher....but you know, now that you bring it up--I might indeed buy and use the same tire again (Bridgestone Battleaxe), since as I understand it, there's not a whole lotta chioce in tires when it comes to this freakin mothership's rubber.

I don't know that it can be completely blamed on the tire itself, either--anyone else have some input on whether I--and the primary poster of this dilemma-should switch to something other than stock? If so, don't the STs have a bit more choice in the matter than big brother LT?

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I run 39 lbs in the front, 41 in the rear.

 

My last Z6's were toast at 5,000 miles.

 

Aside from the different compounds that make up all the brands, it's all how you ride, road surface, ambient temperatures, and pressure that determine how much mileage you're gonna get. My current Pilot Roads are starting to cup and they are only 3 weeks old. They have 4,000 miles on them, of which 2500 was probably slab riding, done in very hot weather.

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did I say that somewhere in there?
no confused.gif somehow i thought that's what you meant. i had to "prematurely" replace a front tire due to cupping that my dealer said was because I ran it on low tire pressure. in fact i did, because i was lazy. now i'm $150 smarter and less lazy and pretty anal about my tire pressure....but now it doesn't matter?? it's gonna cup anyway? what's the deal??
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ShovelStrokeEd

I have about the same milage and in about the same period on my Pilot Roads, 3K miles in 10 days over last week and 3500 miles in about the same period right before. No sign of cupping yet. This, on my Blackbird where factory recommended pressures are 42/42. I run 37.5/39.5. The rear is starting to show a little squaring since all but about 800 miles of that was slab. I weigh 220 lbs and for this entire time have been carrying about 120 lbs of luggage distributed in 30 lb lumps between side bags, trunk and pillion seat. Speeds have been in the 80 to 140 mph range. BTW, the bulk of that milage was really put on in about 8 days of riding, just covering ground on the weekends.

 

Over the last 10 years or so I have averaged about 4 or 5 sets of tires a year and feel a little qualified to comment on brands. Bridgestones cup the worst, followed by Dunlops, Metzeler and then Michelin. This on a variety of bikes from a RS, to an RT, to a K12RS, to an LT to a VFR, to an R1100S to my current 'bird. Still own 4 of them.

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I attended the tire seminar in Vermont. The bridgestone engineer said that tire cupping is 90% caused by pressure too low. I was getting a little cupping on my pilot roads after 3000 miles. I was running 37lbs. I raised the pressure to 40 lbs. The tire whine was reduced and the cupping is clearing up.

There are lots of variable, solo riding, two-up, luggage etc. We were asking for a formula when the engineer said a good rule of thumb is to read the max pressure reading on the tire and then reduce it 2 lbs. My tires said 42, so I set it for 40.

That seminar was worth my ride to Vermont. Actually the ride was really good too. We covered a little over 2400 miles and did less than 400 on the slab.

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Ummm--did I say that somewhere in there? I didn't intend it to come out like that. My point was that I'll probably run any tire on the front a couple of pounds higher....but you know, now that you bring it up--I might indeed buy and use the same tire again (Bridgestone Battleaxe), since as I understand it, there's not a whole lotta chioce in tires when it comes to this freakin mothership's rubber.

I don't know that it can be completely blamed on the tire itself, either--anyone else have some input on whether I--and the primary poster of this dilemma-should switch to something other than stock? If so, don't the STs have a bit more choice in the matter than big brother LT?

 

ME880,ME880,ME880,ME880,ME880,ME880 (Metzelers)...See a pattern?

 

Haha, goofin off, but seriously, the Bridgestones are very apt to cupping because of the tread pattern. Run Metzlers, and put pressures at 38-40 front and 44-46 in the rear.

 

No, haha, I'm not a Metzeler employee, but I think the Me880 is the best choice for the mothership thumbsup.gif They'll last longer too clap.gif

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All telever BMWs cup. Tourers seem to cup worse (rt,lt,rs). Some tires are worse than others, but they ALL cup.

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Guzzidave1998

I`ve had my r12rt now for a month now i noticed the front acting weird I`ve been running 37 to 38 psi in the front I would have thought that have been plenty of pressure, Do the make me880`s the right size for the rt confused.gif

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My apologies if my response to you sounded like I was being a smart-ass--when I returned and began reading other responses, I saw mine to you and it struck me as....well, as rude, and I didn't mean it that way so I hope you weren't offended.

And I agree--if it's gonna cup--what's the deal? I wan't lazy at all, stayed on the tire like a fly on a dungheap, and even used the product recommended by the dealer to ensure that I never lost more than 4lbs of tire pressure withoug knowing about it. Even so, they won't replace the cupped tire, so....

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Over the last 10 years or so I have averaged about 4 or 5 sets of tires a year and feel a little qualified to comment on brands. Bridgestones cup the worst, followed by Dunlops, Metzeler and then Michelin.

Ed -

I have never run the Bridgestones, but have found the exact same results as far as the order of manufactures. I get the best mileage from the Pilot Roads, but really miss the Z4's.

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Bridgestones cup the worst, followed by Dunlops, Metzeler and then Michelin.

I'll remember this when I go to purchase tires. I've always been fairly pleased with Dunlop's cornering and lifespan qualities, of course I used them on older Japanese bikes and none of those old scooters were ever ridden hard enough to push the rubber to its limits anyway.

Thanks for the insight, SSE!

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no apology needed. cool.gif

regarding all talk about raising tire pressure:

1. any big difference in the way the bike handles?

2. is this ok if you're taking an all day ride in the summer heat? the 2 lb. below rated max gives you all the cushion you need?

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no apology needed. cool.gif

regarding all talk about raising tire pressure:

1. any big difference in the way the bike handles?

2. is this ok if you're taking an all day ride in the summer heat? the 2 lb. below rated max gives you all the cushion you need?

1- Yep, it will turn in a little quicker, how much quicker depends on where your pressure was before.

2- We asked that same question, he says that's all calculated when the tire was designed. He said a tire will gain about 1 lb per 10 degrees F., except when the tire is too low. A low tire flexes more and generates more heat and increases the pressure more.

Again it was a good seminar. Some people said the Metzler engineer last year said pretty much the same thing.

 

I'm convinced.

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He said a tire will gain about 1 lb per 10 degrees F

that's the ambient temp rising 10 degrees or the tire temp rising 10 degrees? how hot does a tire get anyway after a few hours on the freeway? thanks .

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ShovelStrokeEd

Brian,

You can figure it out for yourself. The air pressure in a closed container varies directly as the change in temperture. The formula looks like this P1*V1/T1=P2*V2/T2 where P is pressure, in any units you wish, V is volume and T is the temperature in degrees Kelvin. You must use Kelvin as the temperature unit. To convert from Fahrenheit to Kelvin, the formula is ((F-32)*5/9)+273.15=K.

 

Using a rule of thumb that a properly inflated tire will gain about 10% in pressure during riding due to a number of factors, chief of which is carcass flex, it is simple enough to determine how much the air temperature within the tire changed.

 

In the above example, a tire that increased in pressure by 10% from a cold inflation pressure of 68 degrees F, which is 293.15 degrees Kelvin would show an increase in internal temperature to 120.77 deg F, or 322.465 degrees Kelvin.

 

The above assumes a rigid container whose volume doesn't change which does not striclty apply to a tire, but, you get the idea.

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The fronts on K1100RS's and ST1100's cup as much as any telelever bike. Low tire pressures on the front is the main culprit. Most premature and abnormal tire wear is caused by under-inflated front and over-inflated rear tire pressue.

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I would tend to agree with one exception and that was the Michelin Macadam 90's supplied on the bike. The Macadams and the Bridgestone 020's were my worst cases so far. I had very little problem with the Pilot Roads or the Avon Azaros I'm running now.

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