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Jeff Policky
Jeff Policky, Motorcycle Mechanic
Category: Motorcycle
Satisfied Customers: 2425
Experience:  Yamaha Gold, Suzuki Gold, Honda Bronze, Polaris Bronze, BRP
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I have a 2008 Suzuki VStrom 1000 has 60k on it. The front

Customer Question

I have a 2008 Suzuki VStrom 1000 has 60k on it. The front tire is wearing in strange fashion. getting scalping on edges of tread, second tire to show this problem. Balancing and pressure is good. Suspect front forks?
Submitted: 8 months ago.
Category: Motorcycle
Expert:  RSRBOB replied 8 months ago.

Hi and thank you for your question.

I would like a few additional details on this problem.

First, how many miles are you getting out of a tire before you begin to see the cupping?

Second, what brand of tires are you running that are showing the cupping, what size and are you running matching front and rear tires?

Third, who is installing the tires and what method are they using for balancing?

Lastly, is the cupping equal on both the left and right sides of the tire, and what does the tread look like in the center of the tire when the cupping shows up?

Thanks

RSRBOB

PS, do you drive on the righthand side of the road or the left?

Customer: replied 8 months ago.
Hi, the tire size is F- 110/80R19
R- 150/70R17
Michelin Anakee III
Previous tires were Shinko
On the Shinko tires I noticed it at 10k klm. On the Michelin it was 6k.
I had the glass beads put in this time for balancing.
The wear is just off center and can be felt running a hand over the surface. I tried to take picture but it doesn't show up. It seems to be on both sides. We drive on the right
Expert:  RSRBOB replied 8 months ago.

Thank you for the additional information. I do not suspect it is the forks that are causing you the problem. What air pressure do you try to maintain in the front tire? Do you usually ride solo or two up?

Thanks again,

RSRBOB

Customer: replied 8 months ago.
I keep the pressure at 36 psi
I do very little 2up riding. But do trips so bike is loaded up a bit so I run 40 psi in the back
Expert:  RSRBOB replied 8 months ago.

Thank you for the additional information.

Another question would be do you see any feathering to go along with the cupping? By this I mean thin flaps of rubber on either the leading or trailing edges of the rain groves in the tires? Beyond that, my best suggestion is to bump the tire pressure up to 40 psi in the front. I am basing this opinion on your description of the wear patterns being on both sides of the center of the tire, and it doesn't sound like it is in the center.

Unlike car shocks, that as they get old and tend to fade, can produce some unusual wear patterns, motorcycle forks are not susceptible to that. Keep in mind also that most cars get significantly more miles put on them than motorcycles, so they tend to see problems that we don't on motorcycles just because of the relative low mileage of the average bike vs the average car. If you have not changed your fork oil in awhile, it is a good idea to do that but more so to get the old dirty oil out that has abrasives in it from internal wear, which tends to accelerate wear even more.

I would also suggest checking the rim for trueness. Usually a rim that has a bend in it has other symptoms more obvious than tire wear, but in the interest of being thorough, it is worth a check. Also, along those same lines, I would suggest going through all the fasteners on the front suspension and torquing them to specs. Some of the fasteners are not torqued as tight as one might think. As you do this, you can check a couple of other things as well. First, I would suggest getting the weight off the front end, and loosen the triple clamp bolts on one fork leg, then attempt to spin the fork leg in the clamps. What you are looking for is a smooth rotational feel to spinning them. What you don't want is to feel a tight spot then a loose spot. That would be an indicator that a fork leg is bent and requires straightening or replacing, depending on the severity of the bend. After you check both fork legs for being straight, tighten the top triple clamp bolts, leave the lower clamp bolts loose, and loose the clamp bolts on the bottom of the right fork leg that clamps on the axle. With those fasteners loose, you will get on the bike, hold the front brake tight, and bounce on the front suspension several times. What you are doing here is ensuring the forks are not "pinched" by the axle clamp. You want them to be straight and allowed to find their natural center so there is not a binding action in their movement because they are not parallel. Once you have bounced several times on them with those clamps loose, go through and torque everything to the factory specs. Everything from the axle, clamps, front fender, upper and lower triple clamps, everything.

Lastly make sure your fork rebound isn't set too slow. Typically manufacturer's have the stock setting fairly close to the middle of the adjustment range.

Interestingly enough, Michelin does not recommend the use of dry or liquid balancers/sealers or any other balancing materials. Tires and Tubes into which these have been injected will not be covered under warranty.

You never mentioned who was mounting the tires and what method they were using for balancing. As ironic or inconceivable as it sounds, Michelin recommends hanging the tire from an axle supported by low drag precision bearings and spinning it by hand and seeing where the light spots are. They do not use computer spin balancers. Strange but true. Even on road race bikes that routinely go 180+mph, they balance them like that.

As far as the brands of tires go, I don't put much stock in anything a Shinko tire does. Shinkos have 2 purposes in this world as far as I am concerned. 1st, to keep the rim off the asphalt, and 2nd, be a low cost alternative to good tires. The only point of note that I took away from that was the Shinkos lasted longer than the Michelin's. My best explanation for that would be the Shinkos have a lot harder rubber compound that is more resistant to wear. Although it may last longer, hard rubber does not have the grip softer rubber has. That is always a trade off in tires, you can get tires that last a long time, or grip like crazy, but you can't get both in one tire. (they are trying to get closer to that with some of the sport bike dual compound tires)

If you need any of the specs I mentioned, let me know and I can provide those for you.

RSRBOB

Customer: replied 8 months ago.
Thanks for all the info. I have the shop manual so should be able to look up the torque specks. A local mechanic mounted the tires and uses a balancer like you said but I don't think he tried it with the glass beads as they are self balancing.
Expert:  RSRBOB replied 8 months ago.

Probably not. I do agree. Since the idea behind the glass beads is they find the light spot in the tire/wheel combo and are supposed to migrate there to balance the wheel, there is no point. It is either one of two things, you can't spin the wheel fast enough for the beads to do their job, or the beads actually work, and there is no need for any other balancing method. In thinking about this, if it were such a good idea to use beads or any type of migrating balancing media, why isn't it more popular? I am not slamming it, but it is curious why it isn't more popular if it really worked. If you want a realistic comparison, try another Michelin balanced the conventional way and see what happens. If you need further assistance, feel free to ask.

Thanks

RSRBOB

Customer: replied 8 months ago.
Hi, sorry I'm slow responding. I have gone through all your steps to check the forks etc. I believe the rim is true, couldn't detect anything there. It's an alloy rim so hoping it's good. The right fork was very smooth while rotating. The left I'm not sure I thought there might be a very slight resistance as I rotated it. This triggered a thought that a few years ago I had a bit of a crash on a back dirt road that landed the bike (and me) hard on the left side. there was little damage to the bike as I have crash bars but did get scratched up and broken turn signal so this might be the issue. If this is the case where do I go from here?
Also I'm a bit unsure about the rebound setting as there is not much in the manual about setting it up. At my age (63) I'm looking for comfort but don't really want to be adjusting it for riding solo, with gear loaded or two up each time.
Oh I did't see any feathering on the tire.
I hope this answers all your questionsThanks, Eric
Expert:  RSRBOB replied 8 months ago.

Eric,

You did a great job answering all the questions. Do not sweat the time delay in getting back to me with answers. I usually check the list every night no matter what, and if you post a reply, it is always put on the top of my list so I definitely will see it.

Lets start out with the fork. I believe you have good reason to be suspicious of the left fork tube. Since we are suspicious, I would like you to check it out further. The down side to that is we are going to have to remove the fork leg from the triple clamps to be able to inspect it properly.

This will entail removing the front wheel and fender, and unbolting the brake calipers from the lower fork legs. Once you get the fork leg off, take a good close look at the upper fork tube immediately below where it slides into the lower triple clamp. When a fork tube bends, that is going to be the place that it will bend. In extreme cases, you will see a crease in the fork tube just below where it is held by the lower clamp. In less extreme cases, you will need to put a straight edge on the upper fork tube or roll it on a set of V blocks and look for up and down run out. If it is bent but there is no crease, it can be straightened. It will take a hydraulic press to straighten it because to get it straight, you have to bend it the equal amount in the other direction. This is not necessarily a job I would recommend for a novice. The tricky part about is is, you actually have to press it farther than you need it to bend because it always springs back quite a bit. Just illustrate the idea, and use totally arbitrary numbers, lets say you have 1/16" run out in the fork leg. (new they are a perfect zero run out btw). You may have to bend the fork 1/4" past straight in the other direction so when you release the pressure, it actually moved the 1/16" you needed to get it straight again. Unless you are confident you can do this, most good motorcycle shops are well equipped to do this for you. Just for the sake of argument, a new upper fork tube retails for about $317. Forks by Frank is a well known and trusted aftermarket fork tube manufacturer that usually sells their new replacement fork tubes for about half of OEM retail. Replacing the tube presents its own special sets of circumstances that we will hang loose on until we know what direction we need to know.

Check that out and let me know where you are at.

Thanks

RSRBOB

Customer: replied 8 months ago.
I have taken the bike to me dealership and asked them to check it over. I hope they can confirm whether the fork is bent or not.
I'll let you know what their prognoses is as soon as I hear from them.
thanks for all your input on this
Cheers, Eric
Expert:  RSRBOB replied 8 months ago.

You are welcome. Hopefully they will confirm your suspicions.

Thanks,

RSRBOB