Tyre cupping, feathering problem

[Swindon Andy]

I've  noticed my front tyre is cupped and feathered, whatever the correct term is. I can feel slight unevenness around the centre tread and the side treads have leading edge and trailing edge at different heights. Not noticeable when riding, except maybe some front jitter at very high speed, and I don't feel any suspension problems. Can anyone point to the likely cause amongst ESA, suspension linkage or balancing?
It's Angel GT type A, will replace with the same soon.

[richtea]

Like this?
https://eurokclub.bike/index.php?topic=3569.msg45852#msg45852

[Swindon Andy]

Yes, like that. Also around the centre tread some slight undulations. Little shallow dips. I did get a move on today, there is vibration at the high end. New tyres soon but wondering if there is something else needs attending to.

[farmer]

feathering would give you a bit of vibration at certain speeds, i would do nothing else until i changed that tyre.
damage from vibration wise, i would think build quality should have enough tolerance to cope with a bit of vibration .... of course there's build quality and build quality, but still if that was going to do damage what would an unseen pothole not do...

[Matt]

PR5 on the back of my R1250GS. Seems to be doing something too. It's about ready to be changed tread wise.

[Phmode]

You must have more money than sense Matt. And as for those chicken strips...

[richtea]

PR5 on the back of my R1250GS. Seems to be doing something too. It's about ready to be changed tread wise.

Confused. Isn't that the wear indicator buried deep in the Mariner Trench there?

[Phmode]

Like I said 

[Matt]

Yeah worse on the top, but I'll measure at some stage. Anyway!

[richtea]

Yeah worse on the top, but I'll measure at some stage. Anyway!

Um, the wear indicator does the measuring. It's either worn to the indicator, or it isn't. 
On the other hand, measuring 3/4 of the tyre 'width' is quite tricky. That's definitely an exercise for the reader.

https://www.gov.uk/guidance/mot-inspection-manual-for-motorcycles/5-wheels-tyres-and-suspension

The whole tread width must have at least 1.0mm deep tread if the original tread pattern did not extend beyond 3/4 of the tyre width when new.
The continuous band of 1mm tread depth over 3/4 of the breadth of tread does not have to run parallel to the tyre centre line (see Diagram 1).



Time to get your crayons out.

[Matt]

What I was trying to say was: can't we talk about cupping!

The tyre is starting to square off, stop tyre shaming me! :p

[chriscanning]

Every picture tells a story.....

[richtea]

What I was trying to say was: can't we talk about cupping!

The tyre is starting to square off, stop tyre shaming me! :p

What is it with people wanting to stay on thread? Crazy.

My assumption is that it's to do with the asymmetric load on the tyre (i.e. the drive/stress is mostly in one direction) - you accelerate hard, the tyre deforms slightly causing some areas of the tyre to come in contact with the tarmac which wouldn't normally (or not at that higher pressure/friction).

And the uneveness left to right - I think there were two hypotheses:
- camber (a theory that coud be easily proven/disproven by some US/Euro members telling us their experience - is it the left side that's worn most?)
- and the other can't remember. Rats. 

[chriscanning]

If folk want to stay thread...my money is on a duff tyre, but as most of the world is either on Road Smarts or Mich 5’s.....and the OP is going to buy the same again...

[Matt]

What I was trying to say was: can't we talk about cupping!

The tyre is starting to square off, stop tyre shaming me! :p

What is it with people wanting to stay on thread? Crazy.

My assumption is that it's to do with the asymmetric load on the tyre (i.e. the drive/stress is mostly in one direction) - you accelerate hard, the tyre deforms slightly causing some areas of the tyre to come in contact with the tarmac which wouldn't normally (or not at that higher pressure/friction).

And the uneveness left to right - I think there were two hypotheses:
- camber (a theory that coud be easily proven/disproven by some US/Euro members telling us their experience - is it the left side that's worn most?)
- and the other can't remember. Rats. 

We can also test the left right unevenness next year on the trip when we all spend half the time on the wrong side of the road . Provided we buy new tyres before we go!