Off-center Front Tire Wear

[markmi]

My 04 RT (6K miles with OEM Macadam 90x) has noticably more wear on the left side (1.5 inches off-center as sitting) and moderate cupping between the tread grooves. Right side has slight cupping. I serviced the tire pressure to 32 psi a few weeks ago and today I serviced it to 39 from 29. I typically ride solo, 60% SoCal mountain twisties at a comfortable pace with little braking.

 

Since I purchased the bike used with 3.5K miles earlier this year, I was concerned the fork might have bumped into something or experienced some other damage under the previous owner.

 

I first searched previous posts on this forum and was surprised to see off-center wear and cupping is quite common. The different theories on the cause is interesting (road crown, left vs right turn distance, right hand weight bias, PTTR, tire pressure, tire type, etc.) but I am not satisfied.

 

Do RT owners just accept this anomaly or is there something that should/could be done to remedy the off-center wear?

 

Is this something the warranty should cover?

 

What percentage of RTs have this issue?

 

Has anyone noticed this on other makes/models?

[ShovelStrokeEd]

First off, if you have been riding with pressures as low as you describe you have found the source of your cupping. I would suggest you check and maintain tire pressure a good bit higher and more often than you are currently checking. Try pressures in the 38 PSI range for solo riding. Many here use even higher pressures but, I think they are doing themselves a disservice in terms of ride quality and only a minute increase in tire life. Their priviledge and right.

 

Motorcycle tires and wheels are a good deal more porous than typical automotive stuff. You can expect to lose a couple of pounds a week even with daily use, more, for reasons unknown to me, if the bike is sitting. Make yourself a ritual and check tire pressure at minimum of once a week. Some of our more anal bretheren check every ride and even adjust for altitude. I won't unless I am spending a prolonged time above 5K feet or making the transition back down.

[dhb]

What Ed said. I've always thought that the slightly greater wear on the left of midline is from the road camber effect--I noticed the opposite effect when riding in New Zealand.

Dave

[tomk99r11]

The road crown can cause left side wear, only makes sense if you ride toward the center of the road. But, a friend who worked in the quality dept of a tire manufacturer said they see increased wear if the tire ply is not exactly to spec. I'm not tire expert, just passing on some info from an informed source. Likely will be pounced upon here if other experts are out there! Agree with Ed, tire pressure is probably the most important factor we can individually control as riders.

[Al Navecky Jr]

Make yourself a ritual and check tire pressure at minimum of once a week. Some of our more anal bretheren check every ride and even adjust for altitude. I won't unless I am spending a prolonged time above 5K feet or making the transition back down.

If you want to be REAL anal about checking tire pressure get a Smartire System. I did and it works GREAT. I had this same problem with my Honda SuperHawk. So I do not think it is just a RT problem.

[Ken H.]

Do RT owners just accept this anomaly or is there something that should/could be done to remedy the off-center wear?

For the most part, accept it, but it can be minimized by better pressure diligence. But ones a tire is gone, it's gone. Do better with your next set.

Is this something the warranty should cover?

No. Tire wear is not a warranty item.

What percentage of RTs have this issue?

TADT.

Has anyone noticed this on other makes/models?

It's not that unusual.

 

Oh and BTW welcome to the board. Enjoy your RT, they truly are a wonderful machine.

[rrrich]

This is a question that quite a few (including myself) have asked. There's a paper on the net somewhere written by a guy who debunks the "road camber" theory pretty well and suggests its a function of lefts always being larger radii turns. Think about that...he's right in the aggregate.

 

My own thoughts have begun to include additional observations about countersteering, our natural right/left tendancies and subliminal fear...to explain this phenomena...which is real. I'm gearing up mentally for a multi paragraph post on it.

 

Ed should have some thoughts about this beyond tire pressure...maybe time to get him back on the road for a few weeks.

 

[dsl]

I've heard the left turn/larger radius theory, but I don't buy it at all. IMHO it boils down to this: Since you should *never* cross the double yellow, your lane is effectively a single lane, one-way road, and I think we can all agree that on a single lane, one-way road, there is no radius difference between lefts and rights.

 

I do agree with road camber being a factor, but believe it is a secondary factor.

 

IMHO, the primary cause for left side tire wear is that most people simply ride left-hand turns harder than they ride right-hand turns [in right-hand side drive countries, that is]. Why do we have more confidence to push it in left-handers? Very simply, because you have a better line of sight. A given corner will *always* have a better line of sight when taken as a left-hander, than when taken as a right-hander, due to the extra spacing of the opposing lane.

 

Perhaps left-hand corning confidence is also due to the fact that we subconsciously know right-handers tend to have a much greater sand/gravel risk than left-handers. For example, when cages run their wheels off the pavement on right-handers, they kick gravel *towards* the pavement vs left-handers where they kick gravel *away* from the pavement. Also, due to road crowning, sand delivered from rainwater run-off will tend to dish, or pool, *in* right-handers while it will tend to disperses *off* left-handers. 4 out of 5 times, if you see any sand or gravel in a left-hander, it will have had to travel across the opposing lane first (the right-hander).

 

Well that's my $0.02... YMMV.

[Stan Walker]

your lane is effectively a single lane, one-way road, and I think we can all agree that on a single lane, one-way road, there is no radius difference between lefts and rights.

 

No, I don't think we can all agree. I for one don't agree. All you need do is look at any photo of a two lane (one each direction) road shot from above to see that your statement is NOT true.

 

Stan

[PeterD]

The attached drawing illustrates two simplified ways of looking at our overall driving patterns. In the case of the figure eight, regardless of which direction you start out, all your right hand turning will be at a smaller radius than all your left hand turning (try printing out the drawing and tracing it with a pencil, for those who like to follow along). In the case of the square, suppose you live in the middle of one straight section. Suppose half the time you travel the square route clockwise, and the other half counterclockwise. Again your left turn radius will always be larger than your right turn radius. Even though real roads aren't simple like this, the average of all the driving you do should come out the same. Certainly if you consider any given route, if you go end to end in one direction, then come back the same route in the opposite direction, for any given curve along that route the radius when you're taking it as a left turn will always be greater than the radius when you're taking the same curve as a right turn.

 

Since the length of a straight section is the same regardless of which way you're traveling, your bike ends up traveling more total miles turning left than it does turning right. Also of course the average speed in left turns will be higher than the average speed in right turns, but I'm not sure that would make much difference in wear, assuming your lean angle (lateral acceleration) is about the same in both cases. Although drag force does go up with speed, would you get a lot more mileage out of a tire if you averaged say 50 MPH vs. 60 MPH? Still the higher speeds in left turns DO add to the effect of the greater distance.

 

[This is of course assuming a RHD situation; in GB it would be the reverse, same as with road crown.]

 

If PTTD were the major factor, the RTs in GB would presumably still show greater wear on the left side of the tire (sorry, "tyre"). Can any riders from LHD countries comment on this?

[Boffin]

I've just taken a look at the front Avon Azaro on my RT. At 6K miles it is looking about halfway worn with no discernable difference between left or right sides. I check my tyre pressures weekly and run 38 in the front.

 

Cya, Andy

[ShovelStrokeEd]

Jeez, Rich,

No more road. I put over 10K miles on my poor S in the last two months and still have a round trip to Indianapolis scheduled for next week.

[dsl]

Well thanks for the patient response and I do understand the theory. I find this an interesting subject and an intellectual brain teaser and so am more than happy to continue the discussion. I could very well be wrong. If so, please help me understand what I am missing.

In the case of the square, suppose you live in the middle of one straight section. Suppose half the time you travel the square route clockwise, and the other half counterclockwise. Again your left turn radius will always be larger than your right turn radius.

I do agree with this, kind of... If doing a closed, non-crossing loop (circle or square) you will ultimately make the equivalent of 360 additional degrees of turning where the left has a greater radius (four 90 degree turns in your square example). If doing a closed, crossing loop (figure 8), you now limit that to 180 additional degrees of turning where the left-hander does, in fact, have a wider radius. However, if you were to go on a 200 mile loop, with hundreds, if not thousands of turns, the ultimate addition of a mere 360 or 180 degrees of additional distance taken on the left turn is, shall we agree, immaterial. So for the purpose of this discussion, let's go with this example:

...if you go end to end in one direction, then come back the same route in the opposite direction..

For which I drew this illustration (N - North, S - South). On the left is the 2 lane road. Assume we start from the South, head North, then come back to the South.

 

When viewed as a two lane road, optically, and relatively, I do agree that it appears that every left turn has wider radius than every right turn, however, I argue that is nothing more than an optical illusion. My point is that, since you *never* get to travel in the opposing lane, the opposing lane is *totally* irrelevant and, just for a minute here, let's pretend it does not exist.

 

On the right half of my illustration, I've merely taken the return Southbound lane, flipped it 180 degrees and put it at the top of the Northbound lane. This is how *your lane* would appear as you ride the full round trip. Perhaps I am missing something, but I simply don't see any *distance* difference between left-handers and right-handers when *viewed* as a single lane, one-way road.

 

Where the opposing lane does become very relevant, is in improving the line of sight on left-handers, and with a better line of sight comes more rider confidence, more corning speed and more left side tire stress.

So... what am I missing?

[Green RT]

Front tire wear problems seem clearly related to the Pulls To The Right phenomenon.

 

Evidence:

Previous bikes did not PTTR and did not have uneven tire wear.

A year or two ago, I pulled the rear wheel shim on current bike.

Since then the PTTR is lessened (almost gone).

And tire wear is more even.

[upflying]

Again a question for physics professors: Is there a possiblity that engine torque has an affect on the PTTR and uneven tire wear problem?

You can feel the torque twisting bike slightly while revving the engine while stopped. BMW's are somewhat unique because the rotation of the engine is longitudinal to the direction of travel (I hope that is the right word). Most motorcycles seem to have a transverse engine where the rotation of the crankshaft is 90 degrees or perpindicular to the travel of the motorcycle. (again I hope I am using the right words)

It could be associated with something called a P-factor in aviation. While operating a single engine, propeller driven aircraft at high power settings and slow speed, pilots are trained to apply lots of opposite rudder to overcome the P-factor effect. Most of it comes from the prop but some of the effect is caused by engine torque. Small single engine aircraft usually have an opposed flat four or six cylinder engine, similar to BMW's flat twin.

I'm not a power boater but I heard boats also need to be trimmed to overcome this effect as well. This could also be why boats turn better in one direction rather than the other.

Could the affect of engine torque in the flat twin design create a slight correction in steering that results in uneven tire wear and PTTR?

Feel free to tell me I am wrong.

[Cali Kid]

This article makes lots of sense give it a read.

It's amazing the amount of assumption, speculation and conclusions drawn from anecdotal evidence. I suppose that is all it will be until I do my own research.

 

Common Motorcycle Tire Wear Patterns

[Zip]

I had similar cupping on that same OEM front tire.

 

I have since switched to ME 880's front and rear, and had minimal cupping on the first front tire (replaced last week). I also bumped up air in front and rear, and now run 38 psi front, solo.

[PeterD]

dsl (BTW, if you would fill in your profile and/or add a sig to your posts, we could address you more politely with your real name),

 

I see two things in your discussion that may be tripping you up. First, you say "since you *never* get to travel in the opposing lane, the opposing lane is *totally* irrelevant". That's not true in our example, as of course unless you return home traveling entirely on the wrong side of the double yellow, you do indeed travel in the opposing lane. Your assumption of never using the opposite lane would be true if we had roads that were all one-way, in which case the USA RHD rule would not apply and we wouldn't have the left side tire wear.

 

Second, in your illustration of the two lanes placed end-to-end (which I agree is a perfectly valid way to illustrate the situation), there is indeed a difference in radius between any given right hand turn and its corresponding left hand turn in the return segment.

 

Could I suggest the following method to realize this. Suppose you list all the turns in the example route for the northbound direction, and give them numbers. Then put them all into two columns, Left and Right, according to which way they present themselves for the northbound direction. For each curve, also list its turning radius (admittedly not a simple number, but I think you see the validity). Now make a new list but for the same trip in the southbound direction, however keep the same numbers identifying each curve. I hope we agree that each curve will appear in the two lists on opposite columns, that is curve #311 will be, say, in the Right column for the Northbound trip and in the Left column for the Southbound trip. Now think about what the turning radiuses will look like in each column. For every given turn in the Right column of the N trip, there will be the same turn entered into the Left column of the S trip, and vice versa. And for each pair of entries, the SAME curve's left column entry will be a larger radius (and therefore a larger distance to get through it) than its right column entry. Finally, add all the distances (or radii) in the N & S left columns, and then add up all the N & S right columns. If you do this with an imaginary trip of perhaps 5 or 6 turns of arbitrary radius (but always the left radius must be larger than the right radius for any given curve), you will see that the total in the Left column is indeed higher than in the Right column.

 

I think in your illustration you can't "see any difference" because the way you've drawn the curves they are not constant width, and the outside corners are exaggerated. Draw a series of left and right turns in a city environment, where the right turns are short and sharp, and the left turns cross a very wide boulevard, and the differences will be much easier to see.

 

HTH

 

BTW, I don't discount the "drive harder in left turns due to better sight distance" theory. I'm sure that adds to the effect a bit. But unless we're talking rear wheel torque or front wheel braking (neither of which should apply to this dicussion of left side wear of the front tire if we are riding reaonably skillfully and not using our front brake in the turns), the only way "riding harder" applies is based on increased lateral force, which, unless you move your body substantially off-center, means increased lean angle. I don't argue that this may be true to some degree, but in my experience I lean the bike about as much when turning right as when turning left. Since the radius is smaller the speed is lower (a = v^2 / r) for a given lean angle. But the lateral force on the tire is about the same in either direction.

[PeterD]

Rick,

 

Great article, though I'd still like to hear evidence from UK riders that they have a wear pattern on the right side of the front tire. So far we have one report here of even wear...

[PeterD]

Will,

 

I've heard this before that pulling the shim reduces or eliminates PTTR. I have seen that BMW's spec for front/rear tracking (wheel centerline offset) is many millimeters (I forget the exact number but it was at least 3 mm). That shim is perhaps one skinny mm thick. I just don't see how it could have that big an effect.

 

Have you tried putting the shim back in to see if the effect returns? I've nearly eliminated PTTR on my bike by carrying about 20 lbs of tools, spares, and gear in my left system case, which I keep there all the time. I still have the shim in place.

 

The article Rick points us to points out that on straight roads neither the slight road crown nor the PTTR would cause your front tire to contact at an angle of 20 degrees or so, which is the angle of the exaggerated wear flat on the tires I've seen with it. I think the article's arguments are strong, and that in the USA we MUST be putting more miles on the bike when leaned 20 degrees to the left than we do when leaned 20 degrees to the right.

[Husker Red]

I don't think it has anything to do with BMW. Here's the front tire of my Honda VTX. There was discussion on the VTX board about it too, and lots of folks on different makes and models experienced it.

 

Also, possibly of note - since the left hand turns are of larger diameter, I usually make them faster than right handers thereby scuffing more rubber off.

 

[PeterD]

Bob,

 

As to causing uneven tire wear, I think Rick's article's point that nothing you do on straight roadway could cause wear to the 20+ degree slopes on the sides of your front tire, which are not even touching the ground, is valid.

 

As to whether engine torque could cause PTTR, basically I would say not possible under steady state conditions (constant speed). No matter how the engine is mounted, the forces between the road and the tire are only determined by the way you are riding (i.e., control inputs to change direction or speed) and aerodynamics. The engine torque is resisted by an equal and opposite torque on the swingarm bearings. The reason you feel it when reving the engine is that that is not a steady state situation, but rather the bike is exerting a torque on the rotating parts of the engine (crankshaft) to cause it to accelerate (increase its rotational speed). You feel the torque until you let off the throttle to avoid overspeeding the engine. If you put the bike on a dyno (or uphill on the road) and held the throttle open with a steady engine speed (i.e., against a load), you will no longer feel the torque twisting the bike under you. Try this by opening and closing the throttle on a steep uphill road at low speed; the only change should be the forward thrust of the tire patch pushing back against the ground. Make sure you are in a high enough gear that the engine will not change speed too fast between throttle open and throttle closed, so you eliminate the crankshaft inertial effect.

 

The situation with boats and airplanes is entirely different because they interact with the medium around them (water or air) by means of a rotating prop as you state. The drive torque is entirely resisted by the medium and therefore causes an equal and opposite torque on the vehicle. Our driveshaft torque is resisted by the drive housing that is part of the vehicle itself (unless your swingarm bearings let go entirely!).

[rrrich]

Its GOT to be a number of factors (btw thanks for the Honda pic cause that helps with the PTTR argument).

 

1. Road camber (when turning the camber deepens the lean angle)

2. Larger radii on lefts

3. Higher speed due to "margin of error" and sightlines improvement

4. PTTR

5. In my case cross steering and countersteering on lefts

6. Rubber compound conspiresy by large multinational tire companies to induce more front tire purchases.

 

[JATO]

OK----so why is there not the same type of "left side" tire wear on the Rear Wheel if the road chamber causes the problem? --Jay

[Dewayne Harkov]

Yeah,what Will said. Pull the shim, wear will be more "normal". Apologies to all the conspiracy theorists.

[dsl]

Well thanks Peter, you have cleared a lot of the problem up in my mind (seriously).

 

When I said the "opposing lane is irrelevant," I meant you should never cross the double yellow and ride on the LH side of the road.... not that you wouldn't ride home on the Southbound lane. For illustrative purposes, I was just trying to visually remove the *perspective* of the other lane, which I thought only served to optically make the corner radii *appear* different between lefts and rights.

 

No point in numbering/measuring *my* illustration - I am certain the radii will measure the same between left and rights of the two lanes as I simply created one lane, and then, copied it and moved it a few millimeters to the side to create the other lane (in fact, all four lines in the 2 laner are exactly the same). While I believe the illustration certainly seems legitimate, and will mathematically result in equal left/right radii, something deep inside did seem intuitively wrong to me.

 

Draw a series of left and right turns in a city environment, where the right turns are short and sharp, and the left turns cross a very wide boulevard, and the differences will be much easier to see.

This cleared it up for me. I tried creating a 2 laner the same way as above using 90 degree corners, but of course, could not without decreasing the right turn radii and increasing the left turn radii. I agree now that there is a difference in the distance traveled between lefts and rights. Thank you for suggesting that particular illustration.

But unless we're talking rear wheel torque or front wheel braking (neither of which should apply to this discussion of left side wear of the front tire if we are riding reaonably skillfully and not using our front brake in the turns), the only way "riding harder" applies is based on increased lateral force, which, unless you move your body substantially off-center, means increased lean angle.

Even better, you've so aptly described the physics here that I now even better understand what drives *my* tire wear (and I'll agree that I may be somewhat unusual here). You see, my riding style is maximizing lateral Gs in the tight technical twisties around the lower Hudson Valley and, by definition, the tight stuff tends to be heavily forested and riddled with blind corners (foliage is not shaven off the roadside like VT tends to be). Following the "slow-in, fast-out" mentality, it is the left-handers that provide me the earliest exit line of sight, resulting in the heaviest use of throttle/torque through, and out of, corners. In contrast, the right-handers are blind, blind, blind! not to mention the much greater sand/gravel risk I discuss above. As a result, my throttle/torque application through right-handers is much more conservative and frequently only "maintenance" throttle. And to your comments on lean angle and lateral Gs, with which I agree, ... here's what I do (you'll know who I am).

 

So, Peter, you have shown me what was wrong in my assumptions and you have convinced me that left-handers are indeed longer. However, in my particular case, I am reasonably certain that, in terms of tire wear, this is still a distant secondary factor to my riding left-handers harder. YMMV.

 

Thank you sir for you thoughtful insights .

 

Regards,

 

David.

[dsl]

OK----so why is there not the same type of "left side" tire wear on the Rear Wheel if the road chamber causes the problem? --Jay

Well, I initially thought road chamber was second to line of sight... but perhaps now, maybe third behind distance traveled. But whatever... since bikes are single track vehicles, your question applies equally to any of the theories presented.

 

I'd say it is due to the fact that rear tires ultimately wear out in the center well before the sides due to the constant torque applied to it (accelerating/decelerating/even maintaining constant velocity). In contrast, front tires wear out at their sides first since they are so low stressed in the center (pretty much braking only, also why they last a much longer than the rears).

 

So, looking at a center bald rear tire that has covered much less mileage than the front tire, you are less likely to notice wear differences on the relatively deep treads at the sides of the rear.

 

-David

[Jake]

Goodness!

 

Despite the Honda pic above (never let the facts get in the way of a good arguement, I say), everyone in possession of the knowledge of the secret handshake also knows that the left side tire wear (LSTW) comes from the aerodynamic characteristics of the overhead view parallel offset (OVPO) inherent with the R-type cylinder heads.

 

Quite simply (for you non secret handshake knowing riders, and you know who you are), the left turns produce more front end downforce from the leading edge of the left side cylinder head, which creates slightly higher friction levels for the front tire. (some say it is aerodymamic drag, but my own independently funded tests confirm this not to be true. Afterall, no K bike can stay with an R bike in the twisties, given the same-skilled rider at the helm). This downforce is an attractive tread-trade-off (TTO) for the european-styled rider where the drive-on-the-left roads create higher lean angles for left turns. But, and anyone can plainly see, it simply doesn't work as well for the drive-on-the-right styled roads. BMW should really do something about this, but for some reason no one over there seems to be returning my incessant e-mails on the topic. (Maybe I should change my name to something catchy and start a website on this...Hmmmmm)

 

In short, dump the Macadam 90s for some real tires.

[Green RT]

I've heard this before that pulling the shim reduces or eliminates PTTR. I have seen that BMW's spec for front/rear tracking (wheel centerline offset) is many millimeters (I forget the exact number but it was at least 3 mm). That shim is perhaps one skinny mm thick. I just don't see how it could have that big an effect.

 

Have you tried putting the shim back in to see if the effect returns? I've nearly eliminated PTTR on my bike by carrying about 20 lbs of tools, spares, and gear in my left system case, which I keep there all the time. I still have the shim in place.

 

Peter:

 

The shim is 2 mm thick (1.97 actually). And, no I have not done the experiment of putting it back in. I suppose one should run one front tire with the shim, then one without, then one with, then without for a few cycles and compare the worn out tires.

 

Removing the shim shifts the center of mass of the bike by 2 mm. By my calculations, you could accomplish the same shift by carrying 5.4 pounds in the left case. [Assumes the left case mass is 300 mm from centerline and that the bike plus rider is 800 pounds).

 

You note that carrying 20 pounds eliminates PTTR. That seems consistent with removing the shim which only reduced it but did not eliminate it.

[markmi]

Whew! I'm glad we settled that. I think I'll watch my tire pressure more closely.

[markmi]

Since I started this thread, maybe I can end it. The discussion was incredible and the theory of tire wear most definitely advanced. But I have an observation to add...

 

In my original post, I noted I had an slightly under-inflated tire and had some cupping and left of center wear. I increased the pressure to 39 psi and after my ride yesterday, took a look at the light color dust that stuck to the tire after parking it in the garage. In addition to the bike riding nicer, the dust pattern indicated the tire was contacting the ground more on-center.

 

If I had my guess, tire pressure is a major factor in this issue and the OEM recommendation is too low WRT to tire wear. Maybe it has something to do with the tire construction that biases the wear to the left if ridden underinflated.

[PeterD]

Jake,

 

Now that's the best explanation I've heard so far!

[PeterD]

Mark,

 

Maybe sounds like conspiracy theory, but after all our noble attempts at cogent explanations, wouldn't it be a kicker if the mfrs actually made the front tires purposely assymetrical for some reason (perhaps for wear reasons that don't always work the way they're intended)!

[PeterD]

Will,

 

So much for my metric memory. Yeah, 2mm is starting to get somewhere. I just looked up the wheel track alignment in the 1150RT manual (section 46, Frame). The rear rim is supposed to be offset 3.5mm to the right of the front rim, but the tolerance on that 3.5mm value is +/-9mm! Since the shim puts the rear wheel farther to the left side, removing it would make the offset more positive (rear wheel to the right). It would appear the 3.5mm nominal offset is to counteract the weight imbalance caused by the final drive unit and swingarm, but the 9mm tolerance seems ridiculous. If indeed some bikes are way off from the nominal offset, then it would make sense that removing the shim and adding 2mm more positive offset would help.

 

Is it possible that the shims are different thicknesses on different bikes, and they choose shim thickness to adjust the offset? [that might explain why I remember MY shim being just 1mm thick...] Going out on a limb here!

[Green RT]

Is it possible that the shims are different thicknesses on different bikes, and they choose shim thickness to adjust the offset? [that might explain why I remember MY shim being just 1mm thick...] Going out on a limb here!

 

Peter

 

It's possible, but I would be surprised. I suspect your memory. I know if go to the hardware store to buy a nut and don't take the bolt with me or measure it first, I never get the right size. It is always too small or too big. Maybe you have perfect pitch for bolt/nut/shim sizes, but I don't.

 

It occurs to me that some of the disagreement on this topic may be the result of a number of different things causing asymetric tire wear. Maybe on R11s it is tire track, while on Honda's it is something else; and, maybe sometimes it is the way people ride or the roads they choose to ride. It is easy for me to believe that there could be lots of things that cause it.

 

Will

[Beemeroil]

Have you ever considered the fact that most of us dress left and that this can explain this mystery.

[rrrich]

I've always thought genius was the ability to see things that are so obvious that no one else has seen it. Dress left, wear left...dude, you got it!

 

[Martyn]

Rick,

 

Great article, though I'd still like to hear evidence from UK riders that they have a wear pattern on the right side of the front tire. So far we have one report here of even wear...

Based on personal mileage over more than 30 years, & Fleet useage, yes there is a trend for wear on the right side, which I'd always assumed to be a product of camber, but as is often the case the forum has turned up some interesting alternatives.

[STL RT Rider]

Surely someone figured out by now that the wheels are offset to counter-act the torque from the engine.

 

This info comes from my mechanic who is a 20+ yr. Master Tech and runs his own business now servicing Beemers.

 

Think about it. Ever rev at a stoplight? What do you get? Torque to the right. If the wheels were not offset, you wouldn't be able to ride straight down the hwy.

 

Just put my third of set Metz' on the RT and both previous ones wore the same way ... more wear on the left side.

[Frank Cloud]

Interesting, I'm gonna have to give that one some thought.

 

Perhaps, I'll consult the oracle. Bueller? anyone?

[Stan Walker]

Think about it. Ever rev at a stoplight? What do you get? Torque to the right

 

Think about it, rev it up to 7000 rpm at the light and hold it there. What do you get once it's up to 7000 rpm, nothing. Same thing you get going down the highway.

 

Stan

[ShovelStrokeEd]

STL,

'fraid Stan is right on this one.

 

The torque reaction is only there during engine acceleration and is not there during steady state running. If you look for it during riding it is just barely noticable. Reason is, the rotating components cannot accelerate as hard so the chassis reaction is lessened.

[matthew517]

I have the same problem and brought it to Morton's BMW attention when I brought my bike in for service. They said it had to do with the right side of the bike being heavier than the other. I reduced my air to 39 and the bike front tire makes less noise.

[Wade M]

I had the same cupping problem with Bridgestone BattleAx tires which progressed until I felt uncomfortable moving through a left turn at my normal speeds. The tires had approx. 5,000 miles. The front wore as you described. The rear was fine. My tire pressures were okay as well. I found this link and decided to get some Z6s. No problems with them. I know this link does not reference the same tire but the logic would seem to apply.

 

http://www.rattlebars.com/valkfaq/tirewear/

[scatterbrain]

Mark,

You've got the worst of both worlds here - low front tire pressure on a Macadam 90X, the absolute worst-cupping tire I've ever experienced. I ran them on my Yamaha TDM850 and on that bike, I found it took 45 psi in the front to keep it from cupping! Insane! (At that front tire pressure, I wonder how much more punishment my front forks are having to deal with over sharp bumps.) One time I got caught with no tires available near me for my K1100LT and had to run a Dunlop D205 rear and a Macadam 90X front, knowing that down the line that front tire would trash itself and need to be replaced. That time I got about 6k on the front before I ditched it for the D205 front - and that was keeping the pressure up around 38 where Ed said. (by comparison, I would routinely get 11k to 14k miles on those Dunlops on my LT, with the Dunlop still cupping, but not nearly to the extent those 90X's would.)

 

And it wasn't just my experience, either - A good friend of mine had the 90X's on his Ducati 900SS/SP and they cupped something fierce on him as well.

 

I've had the best luck avoiding cupping the front when I've run a more rounded-profile front tire. (The 90X's and Dunlop sport-touring tires are more triangulated, and so really quickened the steering but cupped as described. A more 'rounded' cross-section tire example would be Metzeler MEZ4).

 

Good luck!

[philbytx]

Smarttire is all well and good but IMHO it really isn't a substitute for checking pressures before a ride and using it as an adjunct to checking the tires for wear and any damage.

[johnt650]

I found the Macadam 90's terrible for cupping. My last set was BT-020's and they also cupped badly. I have run the Pilot Roads and they showed virtually no cupping. Could tread pattern have a bearing or is this from carcass construction?