Uneven wear of front tire

[3ackok]

A lot of good information, thanks! Before I read it, I spent the evening jumping around the bike, trying to take measurements.
First, this is my rear tire. The tire is Avon Storm, and it is 170x60 instead of the factory 180x55. The previous owner told me that narrower size improves handling.

 

[3ackok]

First I decided to check if the bike is twisted around the horizontal fron to back axis. I put it on a center stand and centered the fork by measuring the distance between ends of the handle bar and gas tank keyhole. Than I used a plumb bob to check that both wheels were exactly vertical.

 

[3ackok]

Next I went to check if both wheels ride on the same track. I tried to build a contraption from parallel straightedges, but in the end settled on the string method, recommended by Eric. I wrapped the string around the rear side of the rear tire, had my wife watch it just touch the front side of the rear tire, and measured distance between the string and rim of the front tire, front and back. I repeated the procedure on the other side of the bike. On both sides the distance to the front of the rim was 40mm and to the back of the rim it was 38mm. Kind of doesn't make sense, will have to write it off on lack of precision. It looks like my alignment is correct.



Time to sleep...

 

[RJVB]

First off, I think we know that bike here ... yellow, ceramic-coated headers, I'm pretty sure that the PO was a member on a previous incarnation of this forum!

You've noticed that the rear tyre has asymmetric wear also, I presume? Less severe, or maybe I should say similar wear but without the deformation?

Having said that, I wonder if the way you sit in the saddle could come into play. Even with a relatively svelte rider on a bike with a weight like the Breva, shifting weight around does have some effect: more weight to the right of the bikes COG would require the bike to be leant leftwards to have the combined COG on the vertical, riding straight ahead. That combined with road camber (do you ride many small roads with "sloping shoulders"?) could explain *part* of what we're seeing here, without anything being wrong with the bike. Someone riding behind you (before and after you've changed both tyres) could check your riding position, I presume.

 

[Gary]

There is no bent frames, collapsed wheel bearings here just general wear, and you dont have curvature of the spine. That back tyre is worn flat and must be shite on roundabouts, islands, or what ever you have. You must be feeling it go over the ridge ? The front.............. shagged. As you say they were on at 7500 miles and you've done another 7000. My rear will last 6/6500 miles and it looks like that,(carry 70kg luggage all the time). Front has last 12,000.
Also putting a smaller trye on a given rim changes the tyre wall support. i guess the previous owner was more into saving £$£$£ than cornering.

 

[GrahamNZ]

3ackok

The photo of your rear tyre is very telling because the wear pattern matches the front, plus the usual central flat which comes from a lot of upright riding.

Your bike looks great in yellow etc IMHO. As RJVB points out we've seen the bike here before.

Fitting a narrower rear tyre does make a bike turn in easier but tyres and rims should be a correct match for the tyre to retain its intended profile.

If there is no misalignment problem, the wear you have is probably due to old tyre age, extreme road camber, low tyre pressures, or heavy loads. Since all the bad wear is on the left side I'd rule out hard riding - that would cause wear to both sides unless a lot of track riding was involved.

Load is an interesting one though. Many bikes are sprung for "average weight riders" of 75 - 85kg. That means complete with riding gear! In my case a naked 82kg rises to 90kg so I'm already too heavy to be "average". What that means is that the springs can be too light for the load and when that happens the tyres are called on to flex more than they should with off centre wear being accelerated. Increasing spring preload does not increase spring strength - it is merely a way to set the ride height. To determine if springs are correct for the load the static (bike only) and laden (bike plus load) sag needs to fall within reasonable percentages of total travel available. Japanese bikes tend to be undersprung but Europeon ones are sometimes the opposite. I did once measure the sag on my Breva and from memory the figures were OK but on the soft side of ideal. So if the previous owner and/or you rate as big blokes that could also contribute to the wear you have. If a lot of weight is being catered for I'd run the standard tyres at 36psi front and 42psi rear, which is what I do. Under no circumstances wiould I run less in the front nor less than 40psi rear.

Graham

 

[erix2]

Normal camber wear with above average mileage and little under pressure seems to be the concensus from my contacts now the chassis is proved ok.

Enjoyed the discussion..

Eric B)

 

[3ackok]

RJVB wrote:

First off, I think we know that bike here ... yellow, ceramic-coated headers, I'm pretty sure that the PO was a member on a previous incarnation of this forum!

Yes, Warren, who sold me the bike was on this forum. He seemed like a very nice guy, I didn't think that he was "economical with truth", but misalignment could have other causes, so I wanted to check it anyway.

You've noticed that the rear tyre has asymmetric wear also, I presume? Less severe, or maybe I should say similar wear but without the deformation?

Rear tire is somewhat asymmetric, but it is not unusual at all. I commute to work, and it is not all twisties. If my front was worn in the same pattern, I wouldn't be concerned at all.

Having said that, I wonder if the way you sit in the saddle could come into play. Even with a relatively svelte rider on a bike with a weight like the Breva, shifting weight around does have some effect: more weight to the right of the bikes COG would require the bike to be leant leftwards to have the combined COG on the vertical, riding straight ahead. That combined with road camber (do you ride many small roads with "sloping shoulders"?) could explain *part* of what we're seeing here, without anything being wrong with the bike. Someone riding behind you (before and after you've changed both tyres) could check your riding position, I presume.

Not sure that sitting sideways is possible, unless trying to compensate for some sort of back pain. Should be noticeable too.

GrahamNZ wrote:

If there is no misalignment problem, the wear you have is probably due to old tyre age, extreme road camber, low tyre pressures, or heavy loads. Since all the bad wear is on the left side I'd rule out hard riding - that would cause wear to both sides unless a lot of track riding was involved.

The tires can't be old. The bike was put on the road in the Feb. 2007, and these tires were installed at some point before June 2008, so they are about a year old.

Load is an interesting one though. Many bikes are sprung for "average weight riders" of 75 - 85kg. That means complete with riding gear! In my case a naked 82kg rises to 90kg so I'm already too heavy to be "average". What that means is that the springs can be too light for the load and when that happens the tyres are called on to flex more than they should with off centre wear being accelerated. Increasing spring preload does not increase spring strength - it is merely a way to set the ride height. To determine if springs are correct for the load the static (bike only) and laden (bike plus load) sag needs to fall within reasonable percentages of total travel available. Japanese bikes tend to be undersprung but Europeon ones are sometimes the opposite. I did once measure the sag on my Breva and from memory the figures were OK but on the soft side of ideal. So if the previous owner and/or you rate as big blokes that could also contribute to the wear you have. If a lot of weight is being catered for I'd run the standard tyres at 36psi front and 42psi rear, which is what I do. Under no circumstances wiould I run less in the front nor less than 40psi rear.

Graham

I have to admit that I'm beyond average, tipping the scales at 105kg The PO is smaller in all dimentions, but he tuned the suspension to be stiff. Bike feels OK to me, definitely not too soft. Road camber is an issue, but the roads I ride are not too bad in this regard.

I haven't yet checked plays in all bearings as you recommended, will do it soon.
The strange thing is that the bike feels normal on the road, straight and curves. Yesterday I tried to let got go the handlebars. They wobble a little, but bike doesn't pull to either side. Maybe I got used to the behavior as the tires slowly wear out, or I'm just not good enough rider to feel the difference.

 

[RJVB]

I'm pretty sure that I'm not sitting perfectly straight in the middle of the bike myself, but tend to slouch to one side. That's what made me think of it.

I'm a bit amazed you say that the bike feels normal. As I said, my front looked basically the same, though much less severe, and symmetric. I discovered it after I'd noticed that the bike would pull to the side. I asked someone (much more experienced than I) else to ride her, and for him she pulled to the other side. Then we looked at the tyre, saw it's deformation, and understood. In your case, I'd expect the bike to pull leftwards, unless you've learnt to compensate while the issue developed. Do you have a chance to ask someone else to ride her for a bit?

 

[Chuck in Indiana]

Still I'd say nothing to worry about. Rear showing the same kind of wear. Riding on a lot of straight high camber roads will do that. Especially chip and seal roads. The tires are just way past the time they should have been changed. Install new tires, keep them properly inflated, don't worry, be happy..:lol:

 

[londonrob]

Yes, after seeing those pics i reckon both those tyres are stuffed.
Lots of upright highway riding will soon put a flat on tyres, you need to get out in the twisties!
If my tyres last longer than a year i definitely haven't been riding enough!

 

[3ackok]

RJVB,
Unfortunately I don't have an experienced rider nearby. Change in handling is hard to detect, when it happens so slowly and gradually. I tried to pay more attention to it as I rode today, it seems that the bike is wavering a bit on a certain lean angle, but I don't exactly remember how it felt last summer. Generally, I am not a big believer in measurements by the seat of the pants, a margin of error is just too great.
Chuck in Indiana,
I think that I'll do just this- replace the tires and ride. I checked alignment and bearing plays, so I can be reasonably sure that the bike is in a good shape.
londonrob,
I'd love to get out in twisties, but my winter riding was strictly to work and back- it was way too cold for pleasure rides!

 

[GrahamNZ]

3ackok

My Breva's steering is rock solid when I release the 'bars, even when decelerating. Just like a quality bike should perform.

No matter who you are, nothing transforms a bike more than fitting new tyres - in a matched pair of course. Wear creeps up on us and only the sudden transformation brought by new tyres reminds us of that.

Here in a land of corners, and rain all year, fitting new tyres as soon as the wear indicators are reached on either tyre is life saving. Cheaper than crash repairs too.

All that connects us to the road are tyres. Treat them as if your life depended on them - which it does.

Graham

 

[Gazdok]

This high wear on the same side on front and rear and completely to the edges without leaving any chicken strip looks to me like either racetrack use with predominantly fast left bends or, this being Italy, roundabouts taken at very good speed.
But whatever the cause the tyres are ready for the bin.
3ackok did you notice that the 170/60 actually handles better than a 180/55 tyre?

 

[3ackok]

Gazdok wrote:

3ackok did you notice that the 170/60 actually handles better than a 180/55 tyre?

I bought the bike with 170/60, couldn't compare to 180.
I installed new Dunlop Roadsmarts, but was out of town and haven't had a chance to ride. In any case, I don't believe that it is possible fro anyone to objectively compare handling of a new tire with the old one when it was new last year.

 

[3ackok]

3ackok

Have you done the fork twisting check I described?
Road camber does wear the tyres unevenly, especially the front.

I measured direction of the front wheel when I checked alignment, and it looked fine. Last fall I changed the fork oil, and this had to eliminate any misalignment. Actually, thinking about fork twisting, I don't exactly understand what you have in mind. I don't know what could be twisted there.
I will try to re check wheel alignment with your procedure. Maybe I didn't do it right.

 

[GrahamNZ]

3ackok

Agreed that removing and refitting the fork legs is certain to remove any twisting resulting from a topple over.

What is fork twisting? It's when the fork legs become forceably out of parallel when the legs move slightly and differently where they're held by the triple clamps and wheel axle. It's very common when a bike has been on its side, even without hitting anything, and is the firt thing to check after a fall. Easy to fix, as I outlined. If left twisted you can be applying constant steering pressure to run straight and the front tyre will be subjected to a scrubbing action on one side. if you look at the lower triple clamp on older bikes and those on the latest and best, you'll find that the older ones usually had only a single pinch screw per leg and the latest and best will have two and often three screws. That's to ensure greater resistance to twisting. Axle diameter too tells the same tale. Larger is better, and the more rigidly it's clamped to the forks the better.

Of course a fall can result in bits getting bent rather than just twisted. Fork stancions are a favourite, but sometimes they can be straightened using a press. A bent axle is also possible, as is a bent steering stem in an extreme event, but then frame distortion is also likely. Some manufacturers ensure that the fork stanchions will bend before the frame is damaged. Stanchions are easily replaced........

 

[3ackok]

Thanks, now I understand. The whole steering system seems pretty rigid, I didn't realize it could be twisted that way. I don't think that I have bent parts- I would probably encountered some difficulties when removing and replacing the forks, but everything went out and in very smoothly.
Yesterday I tried to see if the bike tends to turn when riding without holding the handlebars. The results were inconclusive because direction of travel was affected by body positioning, I'm confident that there is no major pull to a side.
My tires are approaching 8000 miles (13000km), so the problem is not severe, and any misalignment would be minor and therefore more difficult to find.
Interesting that my V-Rod also has uneven tire wear, but it is more pronounced on the rear tire, while on Breva the front one is the worst.

 

[GrahamNZ]

Interesting that my V-Rod also has uneven tire wear, but it is more pronounced on the rear tire, while on Breva the front one is the worst.

Very different steering geometry and probably weight distribution too. Suspension characteristics and tyre pressures affect tyre wear patterns too.

Riding on a lot of straight roads and roads with a lot of camber from the crown to the sides can be a major cause of uneven wear.