Wheel lockup -- skidmark interpretation

So there'a a road I drive every afternoon, and there's a pattern of skidmarks on that road that is 20+ miles long. And every day, I start to wonder what would make it happen.

The skidmarks begin on one highway, take the same exit as I do onto another highway.

The marks are made by one wheel, locking and releasing.

The marks get closer together on the ramp -- down to a few feet apart -- and are 20-25 feet apart on the highways. At reasonable highway speed, it would be 3 or 4 cycles per second. Each mark is maybe a foot or two long.

So what would cause one wheel to lock and release at 4 hz for 20+ minutes?

Are you sure it is wheel lockup and not a "line erasure"? Sounds like someone removed a dotted line.

If not it could be a trailer with a bearing locking up.

Extreme axle tramp?

Yeah, I think it was a wheel locking up on a trailer.

Some trucks can lift an axle when not needed. Once in a while they droop down a bounce off the road. If the systems not right, they skip along and leave marks like you describe.

JB -- it's a tire. It changes lanes on highway #2, and it is consistently in the right-hand side of the lane, or the ramp. And would a bearing locking up be at regular, not speed-related, distances?

Gearheadotaku -- I like that explanation. Slower speeds mean less energy in the bounce, so closer together on the ramp between the two freeways.

In have seen some of the "sailors" here with faulty trailer brakes under the boats pull them for MILES until they have a blow out...

I also suspect a trailer. With tramp and a semi-locked wheel. Bouncy bouncy bouncy, chirp-chirp-chirp.

Empty trailers often do that. See them all the time.

Especially if it was a 2-axle trailer and only had the issue on one wheel, with the other carrying part of that side's load.

Whew. From the thread title, I thought for a second that someone could look at my underpants and see the future.