jonwvara 

My bad weather Univega Viva Sport has a set of those cheap gumwall-looking Kenda tires on it--I think they're K40s or something? I'm too lazy to look it up. I put them on last spring, and rode it a fair amount through the warm weather without noticing anything amiss. But I just tried riding it on rollers (getting cold here in Vermont), and holy cow! It was like riding a mechanical bull! Or maybe I mean a mechanical cow. Anyway, I checked and found that the back tire has a couple of flat/high spots that are maybe 1/8" from low to high. The wheel itself is round and true.
I've had a similar problem once or twice before when I'd done a sloppy job of mounting the tire, but in those cases letting the air out and pushing the bead down and reinflating solved the problem. In this case, though, that solution hasn't worked. Do I just need a new tire? I've run the same Kendas on other bikes with no problems, but I'd guess that defects are going to be somewhat common when you go for the cheap option.

randyjawa 

Sounds like you might have a folded inner tube. This has happened to me, not because I installed, the tube and tire incorrectly, but because the guy or guyette who owned the bike before me failed to install properly. This might not be too noticeable on a road where area of contact is a bit bigger, but on a round roller, that hard spot, thanks to the folded inner tube would be very noticeable.

Let the air out of the tire and then go all the way around, squeezing the tire at every location. If there appears to be a spot that offers more squeeze resistance, that might be the problem.

Anyway, that is just a though and, for what it is worth, it is possible that you got a bad tire.

StephenH

Some tires fit pretty snug on a rim and that automatically centers them. Some don't, and you can move the tire this way and that when it is deflated or mostly deflated, and wind up with varying off-center effects. Check the rim all around, see if there's a mold line or anything where you can tell if it's equally seated all the way around.

Where I notice this, you can ride all day and never notice, but then hit a good SMOOTH road and coast, and you get the up-and-down.

social suicide

I put about a quarter cup of baby powder in the tire and spin and shake it about(outside job). Then I line the inside of the rim where the bead seats with dish soap. After seating the tire I pump it up slowly until it goes 'Bing' then I let out air to the correct pressure. Sometimes a 65psi tire needs about 100psi before it gets round.

Lascauxcaveman 

I bought four of the those sorta-gumwall Kendas from biketires direct just because they were something like $8 and I figured "Why not get them and get that total up to free-shipping range?" Also, the pale butter sidewall is sort of a cool vintage look, if you're not looking too close. Of the four, two of them were (and are) just fine but the other two developed bulges in them that are very noticeable on smooth pavement anywhere about about 12mph or so; it felt exactly like a folded tube but wasn't. I run them only about 5psi over the recommended max, so I don't think I'm really abusing them, at least not as badly as all my other tires.

Not very confidence inspiring (and even though they haven't flatted yet) I find myself uncharacteristically riding the brakes on steep descents :/ I think I'm going to toss those guys back into the pile of old tires I put on my giveaway/sell bikes.

jonwvara 

Yikes! And I just rode them over the Hurricane Mountain Road in New Hampshire--two miles up with extensive sections of 17% grade, then a matching descent on the other side, including a couple of alarming switchbacks. My forearms still hurt from braking.
I think the problem is with the tire. No matter what I do it's significantly out of round at 75 psi, but it's actually not bad at 60. I guess I'll do my roller rides at that pressure. It will also increase resistance a little, which isn't really a bad thing.
In short, they're cheap and worth what they cost. I've got them on a couple of other bikes, but from now on I'll probably stick with Paselas.

Lascauxcaveman 

That "thumping;" it gets pretty hairy around 40mph, doesn't it?

Velognome 

Had the same problem, the tire was not seated properly. The solution was to over-inflate the tire and grab the afflicted areas with this park tool



And rock/twist and pull; deflate. inflate and repeat until the tire is seated. A smooth jawed bench vice will work too, but a pair of lock jaw pliers will damage the casing.

peter_d

Seems like poor quality control on the 27" gumwall Kendas, I've had two, one of them was fine the other continually blew off the rim at only 60psi and on a hooked rim yet. The wire bead on one side turned out to be too big in circumference.

jonwvara 

Whoa! I want one of those! Even if it doesn't solve my current problem--and I doubt that it would--it would be a fun tool to own.

jonwvara 

My heart was thumping so loudly I couldn't have heard it. Anyway, 40 would have been sure death on that road, at least for me. I doubt that I hit 20 the whole way down. Several of the guys I rode with walked down the steepest bits.

miamijim

Sounds like broken cords. I over inflated a brand spanking new cheap gum wall tire and heard the cords tears as I inflated it. $10 down the toilet.

16Victor

Heck, I just glued up some Conti Giro's (tubular) and I experience something similar on rollers. I thought it was my heartbeat but I'm not smooth enough to take my own pulse when riding rollers yet. That wheelset will be replaced soon with a set that has Conti Sprinters. I may learn the difference between a 'value' tire and a solid mid-range performer.

North Coast Joe

I tried a pair of cheap tires on my last rebuild. They did last for about 500 miles before the chords in the back tire tore open just above the wire bead. When I put a set of "name brand" tires on to replace them, I couldn't believe how smoothly the bike rolled down the road! No more "bucking bronco"...sweet!

Velognome 

Broken cords make the tire swell too, looks very obvious when riding, no?

miamijim

Not always. Sometimes it's a lateral kink that makes the wheel look out of true when it isn't.

auchencrow

Ding ding ding!
I don't consider 80 psi as over-inflation though.
I had been using these tires on my flip-bikes uneventfully, but then, after blowing several brand new tires successively, I switched to Paselas.
(Of course this drove up the cost of rehabbing a bike, so I pretty much stopped flipping bikes at that point.)

My advice to anyone observing broken cords in a tire is to remove it immediately - and then run a box-knife through it so that no one will trash pick it and do a face-plant on it.

Velognome 

Broken cords? Perhaps.....

But an un-seated tire makes high/low spots in pairs, opposite each other. The OP writes "a couple" & "high / low spots" which reads more likely an unseated tire.........unless of course the tie experience 2 areas of broken cords while being "not over inflated". Well, that's what I think anyway....plus you get to buy the cool tire tool in the process of diagnosing the ailment

jonwvara 

It's not broken cords. I've had that happen before (on one of these same Kendas, in fact) and it's not that. I guess it might be a seating problem, but I've tried a couple of times to get it to seat properly, and have gotten the same out-of-round result every time. Plus the tire is mounted on an old non-hooked-bead araya rim, so I would think it should seat easily. I have always run tires on that type of rim at about 75 psi with no problems, so that's how I've been pressurizing this one. But if I reduce the pressure to 60, the tire gets acceptably round. To me, that argues for some sort of manufacturing defect in the tire. But who knows? Is it worth spending this much time agonizing over a $9 tire?

Velognome 

^ had the same problem with 27" Kendas on Araya hoops. My LBS turned me on to the Park Tool to seat the tire. Required about 130lbs of air and a lot of tugging and rocking but it works. Tug and pull on the low spots. I've done the same with a bench vice, clamp the pressurized tire and rock and pull. It's a little awkward but it gets the job done. Good luck with it.

auchencrow

Not cheap at that price. After witnessing half a dozen of these tires with the treads either bulging-out/ blowing-out, I do not trust them. It was not a matter of being improperly seated - these were failures right through the body plies.

Lascauxcaveman 

I agree. With two of the four I bought showing visible bulges beginning at about 100 miles, even cheap as they are, they weren't a good deal. I would only recommend them only for people who want to ride slowly and carefully, and at a significantly lower pressure than the stated 90psi maximum.

miamijim

NO.

A tire can be improperly seated in one area. All tires have a mold line around the inside circumference by the bead....spin the wheel and eye up this line with the rim. Other tire marks aren't necessarily even so don't look at them.

noglider 

I have managed to seat defective tires like that, but it takes a lot of patience, and all for a tire so crappy that they shouldn't be selling it. My wife just bought a used bike, a very nice bike, but she has a Kenda front tire with this problem. I told her she needs a new tire. It's one of the unfunnest bike repair jobs.