36er Blowout - HELP

I have a 2007 Nimbus 36. It has an airfoil rim. I bought it secondhand about a month ago, and it was set up with a tubeless tire. After four days of riding, and only about 20 miles, while it was just sitting in my garage, the tire (TA) blew off the rim, breaking the bead. It was inflated to the recommended pressure of 32 PSI. This is not my problem.

Because the bead of the tire was destroyed, I ordered a new Nightrider tire from UDC and a 36" tube from Coker. I received the tube a few days ago and the tire today.

I mounted the tire and tube correctly, checking to make sure that the bead was properly seated all the way around. I inflated it to full pressure, deflated it, and inflated it again to 50 PSI, which I thought would be fine, since the Nightrider is rated to 65.

After five minutes of riding, the tube exploded, blowing the tire off the rim. I could not figure out exactly what caused it, but I think that there is a slight chance that it could have been because of the weld in the rim. The weld creates a small bulge on the inside, which could have caused the bead to slip off at that point.

The tube:

The tape marks where the tube exploded:

The weld:

The weld inside the rim:

Does anyone have any suggestions?

There was a batch of Airfoil rims which were too small (out of rim diameter tolerance), which caused them to blow out with most tires. There were some tires which would work in some cases, but the real problem was faulty manufacturing (or faulty specification).

Some threads on it:

I don’t think that this one was out of a bad batch. Both of those threads say that the defective rims were marked with an “X” near the valve hole. Mine is not.

While the tire may have a PSI rating, the tube, however, may not. I did the same mistake on my 24 when I first got it. The tire said 65psi, so 65psi it went. I rode up a hill and kapow! It was more like a gunshot than a typical kapow. I learned that day to pump the tire where it has a little give when I press on it, not the psi recommendation of the tire. Perhaps you may need to do the same? Also, feel the inside of the rim to make sure that aren’t any snags or anything that could be causing the tube to blow (using a rag or old shirt works wonders for this). If there is, may need to find a way to get it out, or get a new rim. My guess is the tire was on it’s way out, and the tube found a problem. Just so happens to be in the same area. Or you aired up the tube way too much.

I had a similar experience the other day putting on a new nightrider tire/tube on my 36er. I was careful putting it all together and checked to make sure the tube was not pinched at all before inflating, it was about ten minutes before mine exploded while it was sitting on the porch (I was right next to it when it did, my ears were ringing for about an hour). I also saw in the “pictures of your last ride” thread someone ells had a similar experience.

That is frustrating stuff . . . . .I feel your pain.
I also have a non x-branded Airfoil that early on had a tire blow-out problem.
I ended up getting a new nightrider tire and that helped a lot. I never felt that the welded joint had much to do with the problem, though I do recall that the folks that started measuring the airfoil rim diameters found them to be all over the place . . . . bummer because it was such a strong deep dish style rim that could be drilled and lightened and was still rock solid.

Anyway, after the new tire, I’d still describe the fit between tire and rim as a little looser than I like, but its part of the fun that you get with big wheels and tires made to different specifications. I still run a stretched A19 Schwalbe 29er tube that seems to have happily adapted to his new mongo-diameter quite well.

Another local rider (boisei) that had horrible repetitive explosive blow out problems with the nightrider tire on an early Nimbus rim finally eliminated the problem after about 10 blow-outs when he went to the Coker ribbed tire… . . go figure?

tubeless experiment


I had my Airfoil rim for 10 years.
The one time I had blowout was when I was experimenting tubeless(not worth it!). The blowout caused my button-tread tire to warp tiny bit, I ended up replacing the tire and it’s had no problem since.

I’m going to get a new tube and grind down that little nub inside the weld.

We’ll see if this helps…

:thinking: this is what AustinLee did already.

I also believe the rim to be guilty and would try the same fix. Good luck!

I am not convinced that all the small airfoil rims were marked with an X.

I had a airfoil rim on my old 36er (with no X) and can honestly say that my current Coker rim is significantly tighter. If the bead is broken get a new tire and make sure that the bead is even all around the rim.

The bead was broken on the old TA. I got a new Nightrider and seated the bead correctly.

Just waiting for my new tube now…

Go ahead and try a 29er or even a 26" tube. Way cheeper and lighter and you don’t need to wait. Just be careful on initial setup

I forgot to say…

After the initial tubeless blowout, I took it to my bike shop, who successfully installed a 29er tube. Unfortunately, before I even picked it up from the shop, it too blew up. Though, I think this was because of the broken bead on the TA, I am still scared to try again.

When you will be instaling the tire again, try to pour grated chalk onto problematic spots, the tube and the tire. It helps to lubricate them. Also adding a layer of the rim tape could help.

But yeah, griding the weld will definitely help.

I would like to thank everyone here for their wonderful advise!

I grinded down the weld, and I am now successfully running a 29" tube!

Thank you!

Good to hear that it all worked out!