Trainer Tire Bulge Issue
 

Hi,

I recently purchased and went through the horrible struggle of putting the Cycleops trainer tire on my rear tire. I'm using the Cycleops Magus trainer and keep getting a bulge in the sidewall during use. In order to fix this I need to deflate the tire, massage the bulged area back into place, then re-inflate (typically to only 60-80psi). I then get a bulge in another portion of the sidewall.

Anyone have any thoughts as to why this is happening? It has never occurred with a non-trainer tire, the tube being used is, well, used, could that be causing a problem?

tube too big?

Hard to tell without seeing the problem. Two possibilities: 1) uneven seating of the tire bead. 2) Casing failure in the tire itself.

To fix the first, you would re-seat the tire, perhaps using soapy water on the bead to encourage it to move into the proper location. To fix the second problem, replace the tire.

I suspect that you're running with excess roller pressure. The pressure is massaging the tire, and slowly walking it around the rim causing slack areas to form.

This may be compounded by an oil film on the rim, or something else making it slippery.

1- keep tires full to near max pressure
2- adjust roller pressure to the least amount that prevents slippage in normal use at full rpm. This may still allow slippage with sudden acceleration, but that's not a problem since it's not how you actually use the trainer. If the pressure i8s right, the tire will only be slightly depressed at the roller contact point, and you can make it slip if you yank the wheel while holding the flywheel. (but not easily).
3- if all is OK and you've minimized roller pressure, and still have the problem, remove the tire, clean the inside of the rim with acetone, mineral spirits, or 90% isopropyl alcohol. Do the same for the tire's bead area, but using only dish detergent and water, and rinse well.

If you've done all the above, and still have an issue, it might be the tire, but I'd be surprised.

If it's just that tire, it may be a crappy tire. Manufacturing defect. The way you say "horrible struggle" putting the tire on makes me think there is some kind of compatibility issue. 60-80psi seems low, too. Why the need to have a trainer-specific tire? Seems like it's a PITA to install anyway. My trainer's roller is not metal, so it's very gentle on the tires. Does this one have a metal roller, and is the wear you get on it worth the added struggle of switching to this trainer tire which is giving you trouble?

Your tire pressure is way too low for a 23mm tire. Your tire is walking around the rim under the pressure of the roller as FBinNY explains. Inflate to the normal riding pressure or higher.

The force your roller places on the tire is controlled totally by the tire pressure. This means, if your tire is slipping excessively, inflate the tire to a higher pressure so you can get more roller force on the tire.

EDIT: thinking about it more, my previous explanation wasn't quite right. By inflating your tire more, the same amount of deflection from the roller gives you more friction. By using a low tire pressure, you are forced to screw the roller down proportionately more. Thus, to increase the friction to the roller, you want to increase the tire pressure. Lowering it decreases your friction to the roller and forces you to screw the roller down further.

I agree with what is the point of a trainer tire. I just use my old tires saved for this purpose. I stop riding tires a little before the tread is completely gone. They are perfect for the trainer. And cheap. Did I mention cheap. Also because they are fully used, they are stretched and easy to mount.

I have 2 old 23's in my closet for just this reason. I also have a barely used set of 19's that came on my track bike when I bought it. Very sketchy for the road but for a trainer it should be just fine. Current tires on my trainer? End of life for both, so those will be saved as well. Should be good for a few years I would imagine.

I used the original tires that came with my first road bike on the trainer until the casing started separating because of the heat. After running out of old tire stock to use, I got a trainer specific tire. The compound is supposed to be better for the trainer(cannot verify that yet since I've only had it for a few weeks) and it definitely is quieter than an outdoor tire.

IF you don't have a spare tire to put in use on the trainer, a trainer tire isn't a bad purchase.

Just to clarify a few things, I burned through 2 spare tires (they were already pretty used) before getting the trainer tire. I did have the bulge issue fixed, it looks like the Kevlar in the trainer tire was coming apart under the rubber in that particular area, I may have damaged it when I put it on initially.

I returned the trainer tire to my LBS, actually found that it was still under warranty, and had it replaced free of charge (which rocks cause it's a $35 tire). I even paid the $5 to have them put it on the tire and it has been perfect ever since.

If you experience problems again with seating a new tire or bulges, check the rim tape/strip as well. Sometimes that can interfere with seating tight fitting tires. I've solved that problem by using either thinner rim strips or narrower cloth tape -- either leaves a bit more room for the bead.