Jixr

I got a new to me bike and the rear wheel has a 'hop' in it.

The best way to describe it is it feels like my tire has a really bad flat spot or a nail in the tire when you ride it. Each rotation has a bump in it.

I pulled the tire and its in good shape, the tube is fine.

I'm going to take it to a shop but could an out of true wheel cause this? I don't know if a improperly dished wheel would make it feel like it has a hop in one area of the bike wheel rotation.

Dsprok

Possible bent axle.

Jixr

I checked that too, from what I could tell, it seemed straight. the bearings could be blown but my cassette tool is on loan so I can't pull it to check.

Ronno6

A rim that is out of true radially can cause this, but if the rim is the culprit, it will be visible with each rotation. Watch the rim at the brake shoe and note if you see any up/down variation with each revolution.
Many flat spots occur at the rim joint.
It would take a sizeable flat spot in the rim to be felt by the rider.
Another possibility is that the tire was not properly seated in the rim all the way around.
Many times the valve is not pushed up into the tire all the way, causing a high spot.
(I know that is not what you described, but, just a thought.)

Jixr

That was my first thought, that the tire was just bad. and to test it I swapped a new tire and tube to the wheel no difference.

Andrew R Stewart 

A bent axle is not the same as a rim which has a high or low point. Since the axle is stationary it's effect is the same all the time. A rim or tire with a high (or low) spot will have this point come round once every revolution. Hence feeling like a "hop".


It should be easy to install the wheel without the tire in the bike and place a strip of masking tape across the stays or blades so the edge of the tape almost grazes the rim. Spin the wheel and look at the tape edge and the rim top edges and see if the tiny gap grows or decreases. (Basically you've made a truing stand). If the rim is consistently round with no high or low points the repeat with the tire and tube mounted and have the tape placed at the top of the tire.


BTW a common tire mounting fail is to have the tube caught under the tire bead edge, lifting that point of the tire higher up. Often at the valve as the tube has a double thick portion where the valve was molded onto the tube. Andy.

rm -rf

Yes, hold the saddle, lift the rear wheel off the ground, and spin the crank. You can see if the edge of the rim wobbles or not. Then sight along the top of the tire--does it look okay? And the tire has a "bead seat line" molded into the tire that should be a consistent distance above the rim edge.

Since you swapped out the tire, that rules out a damaged tire as the cause.

sch

If the hop is felt, and not so much seen, ie nothing obvious when the wheel is rotated with the bike suspended then it
may be an off balance weight, usually the mandatory wheel reflector. I noticed that when I was nite riding for awhile
and put a spoke mounted reflector on the wheels. Really obvious rolling down a smooth street at 10-20 mph, ie
150-200 rpm. When wheel rotation goes beyond that the pulsations begin to smooth out.

_ForceD_

That could be a bad spot in the tire. I had a tire that did. For the longest time I thought it was a problem with the wheel. But then I identified exactly where it was, removed the tire and sure enough you could see a slight flaw in the construction.

Dan

JohnDThompson 

Or even a poorly-seated tire. Watch the rim closely as it passes through the brake pads. If you see the rim "hop," then the problem is in the rim. If you see the tire hop, but not the rim, the problem is the tire. It could be an impending casing failure as ForceD describes, or the bead not fully seated in the rim.

canklecat

Entire wheel, or just the tire? In my case a hop in the tire that had been fine for a year was due to using cloth rim tape that was too wide. I needed 12mm or so wide tape for the recess in the rim, but just used a 22mm wide strip after watching a couple of mechanics do that on YouTube.

I'd installed the cloth rim strip to replace the thin rubber strip that had extruded through the nipple holes, causing stress splits in the tube. That thin rubber rim strip came with the double wall rim last April and made it about six months before failing, taking the tube along. The cloth strip should fix that problem, but I neglected to either buy narrow cloth tape or trim the wider tape to fit inside the rim recess.

Bad idea. The wider rim strip seemed to leave plenty of bare rim between the shoulder and bead, but it wasn't enough room. I tried two or three different tires and got the same hop with each. The coin finally dropped and I trimmed the cloth rim tape -- problem solved, no more tire hop.

Jixr

UPDATE

Took the wheel in, mechanic said the hub needed adjusted, no big deal. $20 later hub adjustment and slight true, good to go.

Got the wheel, put it back on the bike, and the problem still exist. I've swapped tires, I've swapped tubes, and I can't figure it out.

The rim looks to be true but as soon as I put a tire on it the hop comes back.




attached video. I don't understand whats going on to cause this.

rm -rf

The rim looks good in the video. And since you've changed out tire and tube, it's not a defective tire problem.

Bead not seated evenly
Your tire's bead hasn't popped into place on one part of the wheel, it's sunk down too far from the hook at the top of the rim edge. You can see the tire dip down, toward the axle. (actually, it's hard to see--is the bead seat line dipping down into the rim, or going way above it?)

When I change tires, I inflate part way, then hold the wheel by the axle and spin it by pulling with a finger to get it rotating. I can sight along the top of the rim with a strong light and watch the bead seat line, that molded line in the tire. If it dips down or moves up, the bead isn't set evenly.

It appears to be the opposite problem that this Park Tool example shows, which has it's tire bead too high, almost off the rim.

rm -rf

Hmmm, why doesn't the tire bead seat correctly, with two different tires.

First of all, is the bead line dipping into the rim, or moving away from the rim (like the Park Tool example)?

I don't have any good ideas. Here's a few questions:

Is the rim tape evenly applied, and there's a big enough gap between the edge of the tape and the "hook" at the top edge of the rim?

Did the same tire (or a different tire) work previously, or is this all new?

What tires are they, and what size?

How much air pressure are you using?


~~~~~~~~~~~~
In the past, I've sometimes had to work with new tires, kind of pulling the last bit of the bead "out", by pulling with fingers from the opposite side, to pull on the bead. But I haven't had to do that very often with road bike tires that use higher pressures.

If the bead is pushed too far out, that's often right at the valve, where the extra thickness of the tube gets under the edge of the tire bead. To avoid this, I always push on the valve, through the rim, until it bottoms out on the inside of the tire before pumping up.

Jixr

I trimmed some of the rim tape to make it narrower, used lots of soap and its not seated more evenly now. Seems some areas of the tire isn't really going up into the bead as it should be.

Still not perfect, but That was definitely the problem. I think I have it good enough, gonna go ride it around the block to see if it feels evened out.

I'm guessing its something with the rim,

Bike: 2015 Fairdale Weekender Drop
Tire: Contenntal contact 38c
rims: unbranded
PSI: 80 ( tires say max 85, was thinking about pushing 100-110 to see if I can help snap the bead in.
( all stock parts on the bike )

I bought the bike used at a local police auction.

SBinNYC

The wheel was moving too fast in the movie to figure out what was happening by examining frame by frame. However, there's a blemish on the tire at the high spot @ 19.633 second mark (that's 1 frame from the end). The blemish may have been caused by the tire rubbing against one of the stays. It could also be caused by cut cords in the casing. Look on the other side of the blemish. If the sidewall is more flexible than nearby area, a damaged tire is a possibility.

It's unfortunate that tire and rim are same color. Otherwise, I could have checked for badly seated tire bead in rim - the usual culprit.

For further diagnosis: mark the high spot and take a picture of it that clearly shows the bead and rim. Also, take off the tire and take a picture of the rim interior where the tire is at the same high spot. Between the two, the answer should become clear.

FBinNY 

I didn't read every post, so I'm sorry if I'm repeating anything.

Any repair of the problem starts with knowing where it is, ie. the rim, tire, or seating of the tire on the rim.

Start by spinning the wheel while using the brake shoes as a reference to see if the rim rises and falls as it goes past.

If the rim doesn't have a hop, odds are that it's a simple tire mounting/seating problem, since tires that are defective this way are rare. So, go back to pinning the wheel, slowly this time and watch the molded reference line with respect to the rim. Do this on both sides, and also look at the top of the tire.

If the reference line is even to the rim, yet the tire still hops at the top, stop at at the high (or low) spot and examine that area of the tire for any cuts, lumps or bumps. Good reference line, yet bumpy tire, means replace the tire.