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My Schwalbe Marathon plus tour 26'' x 2.0 has a sideways bulge (both rear and front). In between the 2 tyres and tube there is a anti puncture strip.

The rim seems not to be the problem.

I think the strip is the cause of the tyre's sideways movement. The tyre is already tight/difficult to mount. With the strip mounting is even harder.

Will such a bulge / sideways movement eventually (i.e. in the long term) cause damage (e.g. by bending) the rim, hub, axel, or bearings ?

I am interested in the consequences of this sideways movement not how to fix it.


Update

The bulge is not pronounced. It is at a single spot. I see it when looking down on the tyre (bicycle is flipped over and resting on saddle). When spinning the wheel the tyre suddenly moves right then left (wobble). This happens over 10degrees arc.

I cannot determine the tyre pressure. I've pumped the tyre hard - my guess 3bar. I used soapy water between the rim and tyre.

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    A tire not mounted straight does not cause much lateral force on the rim. I think we need more info on the nature of the ‘bulge’ and how pronounced it is – Argenti Apparatus Jan 1 at 17:41
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    Where is the bulge located (all around or ? ). Is the tyre pressure correct? – Carel Jan 1 at 18:17
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    This most commonly occurs near the valve, where the extra thickness of the tube causes it to get caught under the tire bead. – Daniel R Hicks Jan 1 at 19:19
  • Marathons are a pig to fit on the rim. Did you do anything to try and "stretch" them ? That may have caused tyre damage by tearing the bead making a weak spot. – Criggie Jan 1 at 20:55
  • On re-reading you describe it as "right then left" (of the centerline I assume). Is the rim true? That is - does it run in a flat circle or does the rim move left and right as well? Have you checked for broken spokes? – Criggie Jan 1 at 21:02
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I can't say 100%, and full caution etc that if it's bulging that has to do with casing failure/damage or installation error then you should stop riding it, but it sounds like it's probably distortion caused by imperfections at the casing seam. Marathons, for everything nice about them, are a little notorious for this. Schwalbe will generally warranty particularly bad ones, which if you can feel it clearly while riding I would say these are. At times I've seen a lot of them that needed to be sent back for reasons much like you describe, suggesting a QC step getting missed or a machine not working right or the like. As the incidence of the problem has seemed high during certain time periods, it doesn't strike me as unusual to have two tires with it, and in fact that both tires have the issue suggests it's the seam rather than casing damage.

You can usually confirm that it's happening at the seam by examining the tire to see the look of the fabric layer under the rubber, or inside if you have the tire off, then following around to where you see that pattern disrupted, stacked double for a small bit, etc.

I've speculated that the kind of left-to-right diagonal distortion you describe is caused by something along the lines of the cuts of material not being square or the seams not putting them in a square orientation.

Riding the tires like this won't typically hurt anything except perhaps your enjoyment and steering control. It won't affect the tube, rim, hub, etc. Also, the distortion by itself from messy seams usually doesn't imply any inability of the casing to constrain the tube. If you're using rim brakes then you'd want to make sure the distortion isn't causing rub between the tire and pads or brake arms. And you also want to make sure the bulge isn't causing that spot to get close enough to the frame/fork to cause rubbing or clearance too tight to allow for some debris build up.

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Incomplete answer:

A bulge in the sidewall is potentially a sign of a weakness, where something allows that point to stretch under pressure. A weakness could lead to a blowout or a sudden peeling off the rim.

A bulge can also rub on things - rim brakes are likely to rub most, but even if you have hub-brakes then the next candidates are chain/seat stays, or kickstands. Again rubbing leads to slower harder rides, and eventually sidewall blowouts.

If its an installation error, then there are a lot of causes:

  • could be tube caught under the bead, and inflation lifts it a bit
  • a bead may have failed to seat in the rim right because of damage or obstruction from the rim tape
  • If your tubes are too long for the rim, then the excess material could fold and cause bulges and failure to seat the bead.

None of this explains the "left-then-right" description in the original question. More info needed please.

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A small uneveness in the line of the tire is usually not a problem, and I've never managed to mount a tire without such a small uneveness. As long as the bead is solidly seated within the rim all around the tire, you are fine.

That said, if you are riding the Marathon Plus, you probably won't need an anti-puncture strip. Unless the road conditions in your area are significantly worse than mine, it's simply not worth the hassle. From my experience, you don't have to expect punctures more frequent than once every 10000km with that tire; I've only once managed to find a piece of glass that was large enough to cut through my Marathon Plus. So, if the uneveness is really due to the anti-puncture strip, you may want to try without it.

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