Uneven wear of front tire

[3ackok]

I know that tires don't wear symmetrically because of road profiles, but i think I have a problem beyond this. My rear tire doesn't look nearly as bad. The previous owner played with fork adjustments. Could they affect the wear pattern? If so, how can I adjust correctly?

 

[londonrob]

Could be?
First i'd check that each fork leg is the same height through the top yoke (triple tree for the colonials) then back off each preload adjuster till it stops, then wind them both down the same number of turns (mines at 8 turns)
Then i'd check the tyre is sat right on the wheel and seated true, all the way round.
After that, go for a ride and see how it feels

 

[3ackok]

How do I check the fork height- with fork loaded, or with bike on a center stand and wheel in the air? There are large and small hex heads on the tops of the fork legs, which ones should I adjust?

 

[GrahamNZ]

Tyre pressure incorrect? Low pressure will soon cause poor wear patterns. 36psi is what Guzzi recommend and that seems fine to me.

Graham

 

[erix2]

Any chance of a couple of pics of the wear m8 ? Difficult to say without seeing it. When I used to ride fast, some tyres (Bridgestones, Dunlops) used to wear in sorta tapered blocks....strange....:S

Eric B)

 

[3ackok]

I checked the preload adjustments- both legs were set to 8.5 turns. Tire pressure was 35 PSI. Will take a picture later.

 

[3ackok]

 

[GrahamNZ]

3ackok

Blimey! IMHO that tyre shouldn't be on the bike. Presumably you ride on the right hand side of the road where road camber tends to cause wear that way but I've never seen such a misformed tyre on a bike.

There has been good advice given here on things like tyre pressures and suspension settings, but here are a few other thoughts:

Have you checked that the front forks are not twisted in the yokes? A bike just falling over can cause the fork legs to twist in the yokes. The way to check for that is to verify that when the handlebars are set to ride straight ahead the front wheel is also running in exactly the same direction. If not then the remedy is easy. Slacken all the pinch bolts in the yokes (triple trees), grip the front wheel between your knees and use your hands to nudge the bars into agreement. Then tighten the pinch bolts again.

Are the front forks and rear suspension moving up and down freely? You mentioned that the previous owner had played with the suspension. I've heard of people putting so much oil in forks that they hardly move at all. Is the rear suspension rising rate linkage siezed? Having the spring preload or damping wildy out of balance can also cause tyre wear issues.

Are both front brake calipers operating correctly? With four pistons in each caliper it's unlikely that all of them are siezed, but one could be, causing unequal braking and a twisting force on the front forks.

Has the bike been in an accident? A good way to verify that is to do a wheel alignment check. Do you know how to do that? If not I'll post how I'd do it using a builder's short spirit level and a pair of long straight edges - or just string lines if straight edges aren't available.

Graham

 

[3ackok]

Graham, thanks a lot for the detailed answer!
I already ordered new tires, but want to know if there is some other issue. I replaced tires on my previous bike, and I don't remember that wear was uneven so badly. Maybe I'm just panicking, and this wear pattern is within norm?
I purchased the bike with these tires at 7500 miles. They were already replacements, and had some wear on them. I have close to 14000 miles now, so the total mileage on the tires is 8000 or so- about 13000km in the better system. I've been lucky not to drop the bike, but previous owner told me that he did it twice, both times on a parking lot with zero speed. The bike has some marks consistent with such accidents. It is repainted, which is always suspicious, at least in a car world, but the guy put a number of upgrades in this bike, and I didn't see any signs that it was painted because of a crash. As far as I can tell, it rides normally. He mentioned that he adjusted the suspension for a stiffer ride, and front adjusters have "6.5" penciled on them. However, according to my check, they were set to manual- recommended 8.5 turns.
I'll check the bike according to your recommendations. Please post the alignment instructions.

 

[RJVB]

That's weird indeed. Notice how this is not wear in a V (or what would be a V), but how the centre and side seem to resist better.

That's a Z6, isn't it? It does look like the sort of thing I had on my Z6s, except that for me it was symmetrical and way less pronounced to the eye — there was very little tread wear on my front. My rear had it too, though much less (possibly less visible because it was also squared off). I wrote it off to some weird way the tyres deform(ed) with age. If so, maybe in your case deformation of the carcass of whatever happened asymmetrically??

You did check there's nothing rubbing the tyre on one side, didn't you? You say your rear doesn't look nearly as bad, but has it worn asymmetrically too?

 

[erix2]

Hi, 3ackok

<<...I've been lucky not to drop the bike, but previous owner told me that he did it twice, both times on a parking lot with zero speed. The bike has some marks consistent with such accidents. It is repainted, which is always suspicious, at least in a car world, but the guy put a number of upgrades in this bike, and I didn't see any signs that it was painted because of a crash. As far as I can tell, it rides normally....>>

The more I read this, the more I`m convinced its a (mis-)allignment problem. Ive seen bikes sold with "car park bumps" that have had twisted/cracked frames/forks/bars and lord knows what else... ...and with a bit more digging they`ve actually been "down the road" maybe more than once.

Wheel alignment check isn`t difficult but you will need a hand, best with two or three !
Its a while since I did it so I hope I havnt missed anything out...:S

You`ll need a straight-edge as long as the bike or a piece of string......roll the bike back and forth a few times and get some-one to sit on it and hold it steady with the bars straight but not holding them.

There is usually something in the way when using a straight edge...ie centrestand so the piece of string might have to be used.

Use the S/E to touch the rear tyre in 2 places, have some-one else hold it there and check the front.....if it touches in two places on both tyres at the same time then you are aligned (you can check it on the other side if you like, it looks really professional :lol: )

EDIT...because of age and Brainfade:S .....
With the front tyre being slimmer than the rear you need support the S/E and measure between the straight-edge and two points on the front tyre while making sure the S/E is on the rear tyre

A piece of string needs to be sighted along its length from front contact point to the rear contact point and should touch/measure in the same 4 places as above.

If the person sat on the bike checks that the bars are pointing dead ahead without moving them at the same time.

......if not aligned then you know some-ones been..ahem...economical with the truth maybe.

This should narrow it down a bit and I hope it helps..

Eric B)

 

[RJVB]

The problem here is that the rear tyre is so much wider than the front...

 

[erix2]

Ahhh...I knew there was summat....:laugh:

Easily overcome with a bit of common sense eh, RJ ?

Eric B)

 

[YBFAST]

Wow... thats a lota wear!

For what its worth... ride style/location can have an affect too.
IMHO We all tend to attack the twistys pretty evenly, but in a city environment (sharp 90's for turns) we tend to attack the wider radius left turns through the intersection harder and faster than a slow right turn of tight radius when leaving an intersection.
A great indicator we are spending too much time in the city
??? anyone have similar wear? My metzlers wore unevenly but not that bad

 

[RJVB]

Well, but I fear it's typically the sort of thing that's easily said (contrived) than done ...

I've been thinking of using a laser compass (pointer), but in the end I think I'd go for something involving 2 (large) L profiles coz you can be sure everything is aligned only with 2x2 simultaneous contact points

 

[erix2]

<<.....Well, but I fear it's typically the sort of thing that's easily said (contrived) than done ... .....>>

Haha....if you call taking 2 measurements from the supported straight-edge to the front tyre with a 6 inch steel rule easier said than done.......:S

If its an alignment problem, looking at the tyre, I think the error will be fairly obvious without resorting to thou`s at this stage.

Hope this helps,

Eric B)

 

[john zibell]

3ackok wrote:

This is not an uncommon pattern with older (mid 90s) BMW oil heads. It is caused from a mis-alignment of the rear wheel, that is being offset too much. You are applying pressure on the left bar to go straight.

Have your dealer check that the swing arm is properly centered.

BTW, the BMW folks blamed road crown for this pattern, but bikes in OZ, NZ, and the UK all had the same pattern of left side wear.

 

[GrahamNZ]

3ackok
Wheel alignment post coming. Just need a couple of pics.
With problems like yours it's always good to check that the basics are OK first. If they are then if it was my bike I'd change the fork oil and then fit the new tyres.
Graham

 

[Chuck in Indiana]

I've seen worse. My Centauro used to eat fronts much like that. Many variables involved, including the tire manufacturer, road surface, crown of the roads normally traveled, front and rear alignment. I wouldn't be too concerned with this yet. It's not necessarily something *wrong* with the bike.

 

[GrahamNZ]

John makes a valid point to check the swinging arm pivot for play.
From time to time this is how I do that:
With the bike on the centrestand, have a helper apply the rear brake to lock the wheel to the swinging arm in case there's any play in those sometimes troublesome CARC axle bearings which can confuse things.
Hold the wheel firmly front and rear and attempt to twist is back and forth in the horizontal plane. There should be no tangible play at all. If there is, then do the check for CARC axle bearing play as described here in the past. If that is OK then the swinging arm pivot needs preload adjustment. That involves a bit of dismantling to reach the adjuster under the left sideplate.

Any play in the swinging arm pivot or the CARC axle bearings can be felt while riding as an "uneasiness" when you initiate banking for a bend. It was exactly that which caused me to check things and that's when I discovered that the CARC axle bearings were dozy. And that was in a CARC which had been replaced under the early recall.

Play in the steering head bearings should also be checked for. Bike on cenrestand, rock the forks back and forth and have a helper feel for play where the fork top yoke (triple clamp) meets the steering head of the frame. Play and notching in the bearings can be felt as a knocking as you pass over bumps and when you start to apply the front brakes.

3ackok
If the wear was both sides of the tyre it could be telling that the fork springs are too light for the weight they carry and that the compression damping is also too light. Increasing spring preload does not make the springs firmer by the way, it merely alters the ride height. On a Breva the only way to alter the fork damping is to use heavier oil, which some of us do.

What Chuck says I really can't agree with completely in that I would be very concerned if a front tyre on my bike wore like yours unless I rode huge distances mainly on straight roads with a lot of cross camber. And if that was the case I'd certainly not ride in the rain on that tyre.

I'll start a new thread in the Tech forum about checking wheel alignment.

Graham