New GP 4000s II has a hop at high speed. Is this normal?
 

I just replaced the rear gp4kii 23 with a 25 purchased from the LBS (performance).

I rode it to work and it seemed ok.

Then I took it into the mountains to pre-ride the tour of Calif stage 7.

This is when I noticed the rear going bump bump bump, increasing as I picked up speed. It's difficult to notice under 30mph.

I stopped and expected to see a sidewall cut or swelling, but it looked normal.

Spinning the wheel, I could see a slight hop, as if the rim were out of radial true, but the rim was straight.

I figured it was unlikely to blow out and continued the rest of the ride but kept speed down just in case.

Today in the garage, I disassembled, checked tube (no patch), checked tire, measured with calipers, and reseated it. It's a bit better but still can slightly feel a high spot with hand when spinning it.

I'm wondering if it's within normal tolerances or if there is some internal defect that could cause a blowout later...

Should I try to return it or do you think it's OK to ride?

Balance the wheel.

I balanced it on my nose.

Problem persists.

Either the tire isn't seated well (and presuming the rim bead isn't damaged)....


Or you have a badly molded tire. They happen, had a Schwalbe One with bad-old hop in it, nothing to do but bin it in my case. Although it depends on how forgiving your retailer is about returning tires.

Rims are new-ish dura ace C24, undamaged and true, and I've reseated it a couple times today with marginal improvement.

I think you're probably right about mold error.

If so, and if Performance won't replace, will the extra material wear so the hop stops?

Performance will replace it.

I'd try a new tire.

Is it a 'hop' or could you describe it as a shimmy?
http://www.bikeforums.net/road-cycli...ii-shimmy.html

I don't understand what this discussion is about. You bought a defective tire. What do you do when you buy defective goods? Whatever your practice is, that is what you should do here. What more could we possibly tell you?

I'm wondering if a slight hop is considered defective or not.

Also wondering if it was dangerous to ride if there was no noticeable bulge or tear.

It's not noticeable at most speeds.

Based on the replies above, I'll just bring it back and hope they don't give me another reject.

Not a shimmy, which is why I didn't post my question there.

It does have me wondering about recent quality control, though.

Some of us don't think the shimmy was a shimmy either.

if i just replaced/remounted a tire i would suspect mounting issues first. IME, there are a number of things having to do with mounting that can create a 'hop' in a tire.

i'd probably remount with a different tire, to help rule out wheel/rim/rim-tape issues.

on clinchers rim strips can easily be misaligned forcing the tire to be seated improperly, this can usually be seen from the side when the tire rotates.

Definitely return it for replacement/refund, if you can.

On two occasions, I've bought defective Conti tires. (Still my favorites.) The first problem was similar to yours - slight bulge in the outer mold/casing. LBS replaced it on the spot (including labor.) Last year, defective sidewall, that I didn't notice until inflated. This time, same LBS required me to purchase a new tire, while they sent the defective one to Conti; a couple of weeks later, LBS called to say that Conti had approved the defect claim, so I was credited the purchase price.

occasionally, tyres that don't seat properly can be 'set' by pumping them up much harder than normal for a few seconds (several) until you hear them snap into place, then let them down a bit. I had to do this recently with a Bontrager tyre

So after futzing with it yesterday, I rode it to work and didn't feel it today.

Perhaps inflating it a few times and reseating it evened things out a bit.