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Left Side Tire Wear - TADT


BlueRidgeBoy

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BlueRidgeBoy

At the risk of beating a dead horse I'de like to pose a question to our friends in the UK, Australia and others who drive on the left side of the road. It is well known that our much-loved bikes wear their tires, or tyres if you prefer, on the left side. Most feel that this is due to the road's crown (for drainage). If this is true then those who drive on the left should experience wear on the right side of the tires. What is your experience in the left-driving world?

 

My theory: I think it is due to a combination of road crown and uneven loading. The single sided swing arm makes the bike heavier on the right side which means we have to lean the bike to the left to balance it. If my theory is true then driving on the left with a right-side swing arm should cancel out (to some extent) and give more even wear. Based on this I try to load the left case heavier when traveling.

 

Any thoughts appreciated.

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Joe Frickin' Friday
At the risk of beating a dead horse I'de like to pose a question to our friends in the UK, Australia and others who drive on the left side of the road. It is well known that our much-loved bikes wear their tires, or tyres if you prefer, on the left side. Most feel that this is due to the road's crown (for drainage). If this is true then those who drive on the left should experience wear on the right side of the tires. What is your experience in the left-driving world?

 

My theory: I think it is due to a combination of road crown and uneven loading. The single sided swing arm makes the bike heavier on the right side which means we have to lean the bike to the left to balance it. If my theory is true then driving on the left with a right-side swing arm should cancel out (to some extent) and give more even wear. Based on this I try to load the left case heavier when traveling.

 

Any thoughts appreciated.

 

From discussion here before, the root cause isn't particularly the single-sided swingarm; if this was the case, then all BMW oilheads would suffer the same PTTR and asymmetric tire wear. Note also that for all the oilheads, the weight of the driveline is canceled somewhat by the weight of the left-mounted exhaust pipe. But PTTR seems to be unique to the RT, which has a large and very asymmetric fuel tank, most of the fuel being kept on the far right side of the bike.

 

The RT's PTTR issue is, I believe, related to its fuel tank. Asymmetric tire wear exists on bikes that don't PTTR, and comes down to either a bias in how the rider navigates through left/right turns, or something about the roadway itself.

 

Is it roadway crown? I don't think so. Road crown angles are very small. A civil/highway engineer will be able to say for sure, but I suspect it's in the neighborhood of 1-2 degrees from horizontal - which means that's the angle away from horizontal at which you'd expect the flat/wear to develop on your tires. On a tire with a side-to-side radius of curvature of maybe 3 inches, we're talking about an offset, from dead center, of maybe a tenth of an inch; you'd be hard pressed to see that.

 

Is it rider bias? Two ways this could occur.

 

One is for the rider to push harder in left turns than in right turns. Plausible, since (when riding on the right side of the road) you're more likely to be able to see through a left turn (and therefore ride more aggressively) than through a right turn.

 

The other is the fact that since we stick to the right side of the road, statistically speaking, any left turn we make is likely to be longer than any right turn we make. If the rider rides equally aggressively through left and right turns, the left side of his tire will cover more miles than the right side, and hence will wear more.

 

On sweepers, left and right turns aren't much different; whether going left or right, the lengths don't differ by a large percent, and the rider can see pretty much equally well through both. But in tight twisties (Deal's Gap, Cherohala, etc.), you'd expect the effects of turn length difference to be more pronounced. My own experience bears this out: when I came back from the first El Paseo in '03, the tread was gone on the left side of my front tire, but there was still tread on the centerline.

 

Searched web on "road crown angle" and came up with this site, which agrees with my road crown and left-right path length assessments above. They had nothing to say about my sight-line bias theory, though I still think that's got something to do with it.

 

(is the horse dead yet? crazy.gif)

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quacker944

Yes , in some respects it is a dead horse - mine is - my 04 rt pttr so badly that I'm going to trade it for something else next week. It's a shame, I really love the bike. Last weekend I straight edged the tires and checked the alignment very closely I also gave the bike one last ride to try and change my own mind - to no avail. I have to hang off the left hand side so much [body at 40 deg] to make the bike go in a straight line its nuts - also I find that the muscles in my left forearm and neck tense on a long ride causing stiffness - you know I have to induce 12ft lbs of torque in the right bar [pulling] or 15ft lbs left pushing to over come the pull to the right. Removing the spacer in the rear drive helped but really Is it too mush to ask that BMW build a bike that doesn't act like a nascar?? If I take my hands off the bars at 70mph the bike veers to the right immediately and suddenly, unbelievable. I bought the bike new - so the really big question is what shall I replace it with? A GS or an MV910r?

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My bike has a very mild pull to the right. With no hands, I can keep the bike running straight by sliding my butt slightly left.

My tires seem to wear just a little more on one side.

 

I just read in Rider magazine that they hear this complaint on all brands of bikes.

 

Could the pull to the right, tire cupping etc be more suspension related such as tweaked telever, or forks or bad shocks?

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quacker944

Something else I forgot to mention - I tried riding the bike on the left side of the road and it still pulled to the right, so road crown is not an answer for me. I have six other bikes none of them pttr or cup front tires. I feel that some 1150rt's don't pttr as badly as others and maybe I'm just very sensitive to the issue of my bike - it is also possible that someone else wouldn't find it a problem. It's just such a shame I really love everything else about this bike just can't deal with the pttr problem and two years is enough...

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ShovelStrokeEd

Has anyone ever had their bike over to a Computrak (sp) center to check frame alignment? I wouldn't suggest a straight edge on the tire sidewalls as a good alignment procedure. Bare wheels would be better. I don't know offhand what degree of dismantling would be needed to drop a plumb bob through the steering head axis and then measure the rear wheel sides projected forward. None of my bikes do much of this so it has never really been an issue for me.

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skinny_tom (aka boney)

Has anyone ever had their bike over to a Computrak (sp) center to check frame alignment?

 

Now that this is officially a PTTR hijack, I'll add my 2-cents.

 

My bike NEVER had PTTR until someone was between the cases putting in new seals and a clutch. Since then, my RT has had a mild case of it. I kid you not, I could set the lock and let go before, but cannot now. This was discovered on last years Un ride, when the cases were separated in the middle of the trip.

 

I wonder, and hopefully will find out soon, if there is enough rotational slack when the bolts connecting the transmission and the engine cases to allow a rotational misalignment between the two. This could theoretically rotate the rear wheel axis enough to put the rear tire in a slightly different track than the front, which could be exasterbated by the suspension, since the rear wheel sits "below" the transmission.

 

To my knowledge, the rear frame and centerstand will always indicate alignment, since they mount to the transmission. I suspect that I will eventually get a laser level, and put a stripe up the front wheel and shim the center stand to get it even, the see what the level shows on the back wheel. I can't think of any other way.

 

I missed a good portion of the PTTR debate and this may have been covered there. Maybe I'm just blowing smoke.

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Blue Beemer Dude
Yes , in some respects it is a dead horse - mine is - my 04 rt pttr so badly that I'm going to trade it for something else next week. It's a shame, I really love the bike.

 

I'm shocked that your bike is this dangerous. Sure, mine has a minor PTTR, but nothing like you describe. Has the dealer looked at it? Have you tried resolution with BMW? Surely something is wrong with the bike for it to act that way. You don't list the model year, if it is or was under warranty when you first reported the problem, you may have some recourse.

 

Good luck.

 

Michael

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Al Navecky Jr

The left side tire wear is NOT just a BMW thing. My Honda SuperHawk did the same thing with Dunlop’s (4 front tires) on it. When first got my 2000 RT (3 years ago) it had PTTR with Bridgestone’s on it and it had more wear on the left side. It seemed to go away with Road Pilots (both PTTR and left side wear) and came back with the Pirelli’s. The Road Pilots did not have as bad left side wear as the Bridgestone’s. Time will tell for the Pirelli’s

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quacker944

Well I'm off to the dealer now to discuss the whole thing - in their defense they have offered to take a look at it for me saying that "NO rt should pttr" - the bike is an 04 model 1150rt - The bike has also stranded me at the side of the road so trust is an issue and I just have a gut feeling they they will never be able to fix it to my liking - however that is just a feeling so I will give them the chance to have a go - I'll be interested to hear what they can do... oh dear I seem to have guided this thread in a different direction than originally intended - my appologies

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thatguitarguy

OK, You're making me paranoid.

 

I just bought my first BMW a month ago, a retired CHP '99 R1100RT and have put 2k miles on it so far and it tracks straighter and more confidently than any road bike I've ever had, but as I look at the front tire it is showing slight cupping wear on the left side. The center is still solid.

 

I live in the mountains of Colorado and my daily commute has some high speed sweepers and some twisties.

 

I'm going to have to maintain this bike myself because I can't afford to own a bike that is addicted to dealer care.

 

Before I do anything more than oil changes and minor care like that, are there some measurements I should make as a baseline to be able to bring the bike back to where it is now in the event of maybe eventually having to split the cases?

 

Are there any adjustments that an owner can make in the way of alignment?

 

I've had bikes that were like the one described that were just a constant wrestling match and that definitely takes away from the fun you are supposed to be having, but this RT is nothing but a pure joy to ride so far and I hoping I can keep it that way.

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My 2 cents

After riding some 30 years I have found that some tires cup and some don't. As for the left side wear, I believe in simple math, it's always further around a turn on the outside. One turn dosn't amount to much, but add up 6 or 7k and it's a lot.

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If this is true then those who drive on the left should experience wear on the right side of the tires. What is your experience in the left-driving world?
I'm still interested in the original question. Do those in the UK or other countries that drive on the opposite side of the road from the US see front tire wear on the opposite as US riders? C'mon... we know you're out there... wink.gif
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Hi. Greetings from Northern Europe - Finland. We drive on the right side and a *very frequent* topic/thread on different bike forums is this same discussion about why do they wear more on the left side... It even looks that some (bikes) experience that - others not.

 

CAD / R1200ST

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If this is true then those who drive on the left should experience wear on the right side of the tires. What is your experience in the left-driving world?
I'm still interested in the original question. Do those in the UK or other countries that drive on the opposite side of the road from the US see front tire wear on the opposite as US riders? C'mon... we know you're out there... wink.gif

 

I have just checked my worn out Contis, the front is slightly more worn on the left edge, but even in the centre.

 

Andy

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realshelby

In my opinion....it has more to do with engine torque reaction than anything else. Revving the engine in nuetral will cause the bike to lean to the right. While riding in a straight line the operator has to lean the bike slightly to the left to compensate for this. I notice my '04 RT leans slightly to the left of center at cruise.

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In my opinion....it has more to do with engine torque reaction than anything else. Revving the engine in nuetral will cause the bike to lean to the right. While riding in a straight line the operator has to lean the bike slightly to the left to compensate for this. I notice my '04 RT leans slightly to the left of center at cruise.

 

One theory... amongst many others...

 

BUT - If and when you hear same complaint from riders of all sorts of bikes (V-Twin, in-line 4 etc...) that theory can't though explain those...

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ShovelStrokeEd

Um, not quite, Shelby. Unless the motor is accelerating or decelerating, there will be no torque reaction into the chassis. At steady state, it is zero.

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Joe Frickin' Friday
In my opinion....it has more to do with engine torque reaction than anything else. Revving the engine in nuetral will cause the bike to lean to the right. While riding in a straight line the operator has to lean the bike slightly to the left to compensate for this. I notice my '04 RT leans slightly to the left of center at cruise.

 

 

What Ed said.

 

Next time you're alone on a road, try this:

 

1. in second gear, accelerate to a good high speed (~6K-7K RPM).

 

2. clutch in, put gearbox in neutral, clutch out.

 

3. hit kill switch.

 

you'll find that even with the engine shut off, you still have to lean left of center just as before.

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realshelby

ShovelStrokeEd, I believe there is still torque reaction at steady cruise. While revving the engine in nuetral the reaction you feel is the acceleration of the mass of the crank,flywheel,etc. Once a constant speed is achieved the reaction is less. While at steady speed cruise there is still enough of a reaction to engine/driveline rotation that a slight correction off center is needed to offset this-thus the wear on the left side of tires. My RT is not happy at all without at least one hand on the bars so letting go of them and having to shift weight may not prove much. One of my favorite motorcycles ever was a '78 Honda CX 500. Its engine exhibited many of the same characteristics the RT does, and I remember uneven tire wear on it also. Another example of torque under steady speed/rpm would be a truck pulling a big load up a hill. Especially in years past trucks would have to gear down to the lower gears and pull hills at a few mph. Even at steady speed/rpm they will exhibit a lean to the right. That same reaction would have to be corrected on a bike-by leaning to the left.

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Joe Frickin' Friday
Once a constant speed is achieved the reaction is less.

 

Not just less; at constant RPM, it's zero. If you sum up all the reaction forces/moments through the whole drivetrain, you'll end up with zero - unless the crankshaft is changing speed.

 

Seriously, try cruising in neutral with the engine off, then run the engine with the throttle locked for steady cruise at that same speed. You won't notice any difference in lean angle.

 

Another example of torque under steady speed/rpm would be a truck pulling a big load up a hill. Especially in years past trucks would have to gear down to the lower gears and pull hills at a few mph. Even at steady speed/rpm they will exhibit a lean to the right.

 

The lean to the right in this case is from two things:

 

  • Chassis twist-up due to the transmission of ludicrously large torque from the gearbox to the drive axle. If the RT had a chassis 25 feet long and was trying to transmit a couple thousand pound-feet of torque from the engine to the wheel, you might see its chassis twist up in the same manner - but you'd still cruise down the road with the center of gravity directly over the contact patches.
     
  • Assymetric compression of the drive axle suspension. Apply a large torque (from the driveshaft) to the differential, and the left/right suspension springs have to take on different loads (and therefore displacements) to counter that torque. The effect is very evident in this video of a souped-up Mustang running a 1/4-mile: upon launch, the right side of the rear bumper contacts the ground, while the left side of the bumper still has maybe six inches of clearance.

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ShovelStrokeEd

What Mitch said.

 

Think about this as well, if the torque reaction was leaning the motorcycle to the right, and you shifted body weight to the left to maintain a straight line, you would be back on the center of the tire, not on the left side. Leaning the bike to the left will cause it to describe an arc in that direction, not run straight. If you really look at the wear pattern on the left you will find it is pretty far off the center axis of the tire, not the minute amount it takes to correct for torque reaction.

 

I don't really know the root cause of this, and I imagine there is more than one factor at play. I don't much care either as I seldom run my front tire down to the point where this would become more than an interesting observation rather than a matter of worry.

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realshelby

I also believe there is more than one force acting on this. But I do believe there is a torque reaction at steady speed that aggravates it. I also believe the something in the dynamics of the single sided swingarm are to blame. If the bike was simply leaning one way or another the wear might tend to be smoother with no "cupping". I think there are also some scrubbing forces involved caused by the right side of the frame being "pushed" harder than the left. That could cause the front tire to have a side load on it that other bikes do not have. grin.gif

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Joe Frickin' Friday
I also believe there is more than one force acting on this. But I do believe there is a torque reaction at steady speed that aggravates it.

 

Have you actually tried the coast-down test I described earlier in this thread?

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realshelby

I have not tried nuetral, I have tried pulling in the clutch at 70 or so. By the time I could get to nuetral, it seems it would be hard to compare the slight difference I believe there is when pulling in the clutch. Even pulling in the clutch makes that hard to judge. I do not have a formal education in engineering so I am at a loss to those that do....but if you say there is no torque reaction at a steady rpm why do boats with twin outboards have props that rotate in opposite directions? Or aircraft with twin engines have opposing prop rotation? These machines often operate at a steady cruise. Without opposing prop rotation on either unit they must have trim added to run "level". I think the same effect causes the RT to need a slight lean to the left, a built in trim tab.

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ShovelStrokeEd

Yet other bikes show the same problem, or non-problem in my case. It is not restricted to bikes with a single sided swing arm. My VFR, for example, shows none of this. Nor is it exclusive to shaft drive bikes as I do remember a Triumph I owned way back when did have a tendency to wear the left side of the front tire more than the right.

 

For all I know, it could just be the rider. Most of us don't sit with equal pressure on our sit bones. That alone could influence which way the bike pulls and what degree of lean is applied as we go down the road.

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Parrothead

To add insult to injury.........not only does my bike PTTR (slightly), my seat is worn on the left side, go figure! Now I'm going to check if my front left pucks are wearing faster than the right side!

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thatguitarguy

I'm with Mitch on this.

 

A boat prop is rotating against the water with force perpendicular to the direction of travel as is a plane prop rotating against the air the same way.

 

The only things rotating externally on a moving bike are the wheels and they are rotating parallel to the direction of travel. Internal forces not accelerating or deccelerating don't affect things happening outside the engine.

 

The vice versa of this would be the effort it takes to walk to the front or rear of a plane or ship at steady cruise. If you walk to the front of the plane you are traveling faster than the plane, say more than 500 mph, but the effort is the same as walking down the street.

 

Terry

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realshelby

I am not comparing the props to the bike wheels-but the props to the crankshaft. I do think the rotation of the crankshaft does effect "things happening outside the engine".

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I am not comparing the props to the bike wheels-but the props to the crankshaft. I do think the rotation of the crankshaft does effect "things happening outside the engine".

 

Rotation on its own cannot affect anything, only the increase or decrease in the speed of rotation. It all boils down to Newton's laws of motion - An obect in motion will continue in motion in unless an outside force acts upon it - To every action there is an equal and opposite reaction. To get the torque reaction, you must have an action. A mass rotating at constant speed has no action - it will continue in motion until something acts upon it.

 

At a constant engine speed - no matter how obtained - there is no torque reaction.

As Scottie would say "Ye cannae change the laws of physics Jim"

 

Now, twisting the crank by turning will effect a certain amount of gyroscopic precession on the bike tongue.gif

 

Andy

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ShovelStrokeEd

Now that I think about it, there probably is a little force put into the chassis. Not by the rotational inertia of the crankshaft but by the action of the ring and pinion gears. Of necessity, the bike must generate a forward thrust at the drive wheel to overcome rolling resistance and aerodynamic force. The ring and pinion gear will translate that thrust into the rear drive housing which is prevented from rotating by a strut that is part of the paralever system. That strut, in turn, either pulls on the chassis (early bikes) or pushes against it (hex heads). The forces involved may be small but they are there. I doubt this is the cause of anything much as the chassis/engine combination is pretty rigid.

 

Again, look at the wear pattern, the area of highest wear corresponds to a pretty good lean angle. Far more than one would need to counter PTTR.

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But force/power is being applied even at a constant throttle setting and there has to be a reaction. Most of the force is transmitted through the gears to the rear wheel and the main effect is to propel the bike forward (and of course power is being supplied even at a steady speed and with the throttle in a fixed position.) Does 100% of this power go to the rear wheel and no other (engine generated) forces act on the bike beyond that?

 

(Edit: Looks like Ed was responding to my post even as I was typing it.)

 

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And I always thought it was because I put my wallet in my left rear pocket causing me to lean slightly to the right grin.gifgrin.gifgrin.gifgrin.gifgrin.gifgrin.gif

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And I always thought it was because I put my wallet in my left rear pocket causing me to lean slightly to the right grin.gifgrin.gifgrin.gifgrin.gifgrin.gifgrin.gif

 

Well there you have it. I am moving my wallet tomorrow. I just knew there had to be a simple expanation. clap.gifclap.gifclap.gif All this techno mumbo jumbo couldn't have possibly been correct.

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Whell I must say I'm breathing a sigh of relief on one hand. I recently purchased a 99rt with a rebuilt title, when I purchased the bike the tires were both worn badly on the left with severe cupping on the front, and PTTR was aparent on the initial test ride. I immediatley mounted new rubber and straight eged the tires the bike appeared straight. but still PTTR, My Dealership was no help stating that "the swingarm was upsetting the weight balance get used to it". So I'm thinking I got a great deal on a bike with a rebuilt title and a tweaked frame. Then I read this thread and realize there is hope, It seems to me that the rt that developed PTTR after a case splitting may be on to something. Come on guys I know there are some certified BMW wrences out there reading this Give us the answer.CN.

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