unusual tyre wear

I know you say it wasn't a wheel lockup but it ooks like 1 big skid to me...

Something is slowing the tire at the same point while driving  Brake binding up? 
Jack the car up, put it in neutral and spin the tire by hand. I would guess you feel resistance at one point.  Then start eliminating things, like pulling off the drum and spinning the axle again.  I would guess something with that much resistance would show some major signs of wear.  But I'm no expert.
-=theron 

Nope, definitely not a lockup

Google says it could be "spot wear" caused by worn shock, imbalanced wheel, bad tire etc.

Now, since I built the car, it vibrated when you hit 70 so I used to keep things around 65. (I have wide 5's so finding a place with the correct adaptors was always a challenge....) In the last month I've done a lot of highway miles. Since it was i the steering, I assumed it was the front needing balanced but maybe it was this wheel all along.......

I've found an old school tire place with the necessary wide 5 adaptor, so a pair of new tires and a balance this week.....

Interesting. I've never seen an imbalanced wheel cause a single spot of wear.  Normally it would be an alternating pattern of bald spots, as the wheel bounces up and down in the same predictable way each rotation.  But again, I'm not an expert.  Would love to know, when you have confirmation as to what it is.
-=theron

guessing bad tire improperly formed/belt or carcass slipped

Maybe your wife had the car out one day and she spotted this sign:

Today only - All shoes 50% off !!!

Check for damaged rim or mounting surface.....  Doesn't take much...

Certainly looks like a repeating issue

Looks like unbalance to me. If I recall from my apprentice days, a couple of ounces out of balance creates nearly 16 lbs of unbalance pounding the road at 65 mph. I've seen lots of truck tires that looked like this. Usually the entire tread separates when it gets this bad. I think you were lucky that didn't happen. What did your google search say ?

Scuba diving down here in Baja is still a little cool.....70 F  at 46 ft. yet...........Bruce

Ger,

Spot wear is what your tire is showing.  It's almost always caused by an out-of-round condition.  Can be a defect in the tire itself, or the wheel.  A good tire place should be able to figure it out.  Best of luck and please keep the group informed when you solve the mystery.  

Will do !

Thanks for all of the feedback

One last thing, Ger - If you can find a tyre place that offers a "Road Force Wheel Balancer" for all of your wheels, that would be perfect.  Those machines can balance to a finer point than the usual spin balancers and should eliminate any rumble or bounce, even in these light cars.

Good luck!   gn

Oh!  And Mine has rumbled at about 70, too, but I usually run it UP to 78-80 rather than down to 65.   

My guess is it was a manufacturing fault. It seems the belts in the tyre have failed allowing the tyre to go out of round. The more the belts fail, at speed it would create this wear pattern. ??

What tyre manufacture is it Ger?

Looks like Vredestein Sprint to me?

I wonder if you had an air bubble under the cord, that would cause the thumping when you drive along and it would explain the single worn spot.

Ger:  

"Precision Matters", a shop in Maine, USA, has the adapters to allow balancing a wide 5 on a spin-balance machine.  Don't know if around $140 USD or so delivered to Scotland appeals to you, but it's the only source I have for an adapter that's made Hub-Centric over here.  There MUST be someone in the UK that has them, too.

http://www.precisionmatters.bi...alancing-adapter.php

They carry a whole bunch of neat stuff, all of it seemingly expensive (or I'm just a cheap Yankee.....Dunno!)

Good Luck....    gn

Well, finally got around to changing my tyres.........What a difference round wheels make !!!

Car feels smoother, faster even at low speeds. Took it for a blast down the highway. In the past at 60 there was a wee vibe in the steering, by the time 65 was on the clock I had to back off....NOW, 60/70/80.....smooth and stable Its like a different car !! 

I always assumed the vibration was due to imbalanced fronts, I was so wrong, this tyre was obviously flawed from the outset. (I replaced both rears to be sure)

The tyre shop, (who had the spigot for the balance), said it was probably a delamination, maybe due to an old puncture repair.

Lesson learned !

If seen this before, blister/air bubble under the tread.

That tire looks really old and warn. Replace all four if they are out of date.