Hello all,
I have been having problems with my tubes ballooning out of my rim and exploding on my Unicycle. I have a 27.5” X 3.25” Kris Holm mountain unicycle. In the process of the tube explosions, the edge of my tire stretches so far that it becomes unusable. This has happened to 3 separate tires thus far. All of which have been a different brand of tire.
Below is a history of my problem:
It first happened after I had done some maintenance and replaced a broken spoke like I had done many times before. As I put my unicycle back together and began pumping up my tire, it suddenly expanded out of my rim and exploded. It sounded like a gunshot. That tire was a Duro Crux 27.5” X 3.25” tire.
The second time happened while I was on the trail. I had borrowed a friends spare tire for a muni trip we were on and this time it didn’t explode but my tire still expanded and stretched making it unusable. I had to walk back to the car. This tire was a WTB Ranger 27.5” X 2.8”.
The third time happened after I had a bike shop technician install a new tire for me - thinking the problem would been solved, I went on another ride and it got flat again (it got flat about 24 hours after the new tire installation). But this time It didn’t stretch or explode. This tire was a Teravail Coronado 27.5” X 3.0”. After I got home from my trip I changed my flat tire again for the 4th time in a period of two weeks. I went on another ride with a brand new tube and all was well. I went out of town for a few days and I returned to yet another exploded tire… and by now I was quite frustrated.
I have thoroughly checked for damage on my rim, the rim tape, thorns in my tire and tube, loose and poky spokes, and sharp edges on my rim. I haven’t been able to find ANY problem of my knowledge that could be causing this.
I went to a local bike shop and they weren’t much help. I also haven’t found anything online about my problem.
I am thinking the problem lies somewhere in my rim… but I just don’t know. Does anyone know what could be causing this? Would going tubeless be the solution? Do I need a new rim?
I am at a loss. Any help or solutions for my problem would be much appreciated.
Here are two of my tires that have been stretched to oblivion.
Couple of questions.
What PSI are you putting in the tyre?
How hot is it where you live?
These might have something to do with the reasons why the inner tube/ tyre are exploding off the rim.
I usually have my PSI at 25-35. I’ve ridden with this PSI for years with no problem at all.
Summers are hot, frequently reaching slightly above 100 degrees Fahrenheit. While winters are cold and snowy. Winter and summer air is dry air.
I never ride when temperatures are above 80 degrees. I’ve been riding in cold temperatures as of recent. 20-60 degrees.
I store my unicycle in my basement where the temperature is usually about 60 degrees Fahrenheit.
Hello! Nice picture of the damaged Duro’s sidewall and bead.
Sounds good.
Have you inspected the faulty/leaky tubes, i.e. located where exactly they are losing air?
For exploding tyres: No. In your case I’d expect your tyre to blow off the rim just as likely if it were tubeless.
For flat tubes: Yes, probably. There are pros can cons to it. Your next tyre explosion will be messier with all the sealant.
I believe your rim has an inner width of 50mm – which is rather wide. It’s nice for stability of wide tyres, but unsuited for higher pressure. I’d be prepared for any tyre to go boom again when inflated to more than 2 bar.
(…approximately. You can look up recommendation charts for your rim width.)
If it’s important to you to run your tyre at higher pressure, I’d say you have to consider using a rim of smaller inner width instead, e.g. 40mm or 35mm.
I agree with the comment above.
Going tubeless I don’t think will solve your problem here either.
With tyres of a wide width the maximum PSI is no more then 30psi usually and you are near on over the maximum pressure, the tyre sidewalls will tell what is the maximum pressure for the tyre also rims have a maximum pressure they can take.
I also believe your rim is 50mm internal which is wide but is suited to this width of tyre, personal I wouldn’t go anything under a 2.8.
The rim I believe is tubeless ready, just need to retape with tubeless tape and fit a tubeless valve but I don’t think this is going to solve your problem.
If you want to ride at higher pressure I would also go for a narrower internal width rim.
The heat and fairly high pressure of the tyre might be contributing towards the blow offs. If you checked for any sharp edges on/in the rim etc this is more then likely the cause
Sounds to me a bit like the tire isn’t hooking into the rim flange at all, is that possible? If you ride an all-terrain unicycle, you will probably be in the air pressure range of 0.7 - 1.5 bar. Nothing bangs. It sounds like high air pressure. Attention, the displays of cheap pumps are sometimes not correct at all and tend to show too little air pressure. I once compared it with a precision meter from Topeak and was amazed at how big the error is. Examine the rim flange and mark the area where the tire explodes / pops off. If it’s the same spot over and over again, that would be suspicious. When fitting the tire, after you have pumped slightly, press the tire well again so that it hangs nicely in the rim.
The 55mm Wide Rim is good for the Duro Crux 3.25" , for 2.8" ist it too wide
I have had that problem with a few tires simply because I did not take enough time when mounting to make sure that the tire was positioned correctly on the rim when inflating. The tire needs to have the same embedment in the rim all the way around the tire. I find that I can not install a bike/uni tire as I can a motorcycle or auto tire. Most “normal” tires are self centering, just install and add air they will seat properly. That is not the case with a bicycle type tire. I add just a very little amount air pressure and work around the tire to make sure it is centered. Sometimes that takes a considerable amount of time and fussing with it.
This is a 36er that I did not spend enough time on. I re-installed that same tire on the same rim with a new tube and more care. I have put a few thousand miles on it with no problem.
By process of elimintation, rim does seem like the suspect indeed…
I have heard that this rim is quite hard to get a tire on and off sometimes and that makes damaging the tube during mounting more likely, but the “exploding” part of it doesn’t really match that.
just a thought here, mark the rim where the tire came off during the failure, then if it happens again see if it is in the same place. this way you can narrow it down to find the culprit.
I agree with the previous comments, it’s probably not the rim that’s at fault but the pressure too high. For your setup, I would not recommend inflating above 25psi. For example, for someone who weighs 70kg, 15psi should be sufficient.
Why are you inflating your tire above 25psi? Is it related to your weight (sorry for the direct question, but that’s certainly the most obvious reason)? Can you tell us more about your practice?
Very good points… You really have to take your time with the embedment when replacing tubes, and during your first ride on the new tube keep checking it after first ride you should be all good. It takes me 45 to 60 minutes to do mine everytime and so far never a problem.
