I removed the Nimbus Airless tire from my front wheel and installed a Panaracer Tour 700 x 42 tire. I had bought 2 Nishiki tubes 35-45 to use with my new tires. Well, I started the tire on the rim and then put in a slightly inflated tube and finished installing the tire. I checked both sides to make sure I wasn't pinching the tube and then used my foot pump to inflate the tire....went to about 20psi and then let the air out of the tube and rolled the tire on the floor a bit. The sidewall says 45 to 75psi so I started pumping the tire up, checked the pressure a couple times along the way and then at about 55psi KABOOM!!!!! the tire blew off the rim and the tube shredded. Seriously, my hearing has still not recovered fully 48 hours later. So, I put in the second tube and carefully inflated it up to about 40psi and stopped there. Too gun shy now to go higher until I learn what happened. I've since installed a new tire and tube on the rear and have both tires at about 45psi. What did I do wrong?

I think you had the tube pinched. No way that can happen otherwise. You might get an explosion like that if you had a carcass rip or something, but you would probably have noticed the tube blistering out of it and it probably wouldn't have blown the bead off the rim.

So work on your inspection technique... it sounds like you did it right, but I still think you missed it.

But now that you're gun-shy... when you get it up to about half pressure, you can do another inspection and look for any place the bead is starting to rise; and you can repeat every 10 psi increase or so until you're confident.

And you can also wear hearing protection just in case.

Sometimes it can be hard to go back and be sure of what happened. FWIW, had the same thing happen to me last week. Loose fitting tire. I was sure I had it on the rim, and probably I did, but must have knocked things out of whack before pumping. I went up to 30, then started to go for 60, and wham! The tire came unseated and the tube spilled out all over -- thankfully without popping. I deflated the tube, remounted the tire, and took more care the second time to ensure the rim was centered within the tire, paying close attention to the bead seat line, and all was good.

Now do this:

You say you have installed a new inner tube and inflated it to about 40 psi. Now that you have done that, examine the tire all the way around on both sides. Most tires have a line running around the circumference near both beads. If both of those lines appear to be equal distance from the rim, you're good-to-go.

I agree with the folks who suggested you have pinched the tube somewhere under the tire bead. When that happens, the internal air pressure tries to blow the tire bead off of the rim. Sometimes it's successful right away, sometimes it takes a while. Checking the distance of the line in the tire from the rim gives you a warning if the air pressure is trying to blow the tire bead upward.

Rim Strips??? Yes / No

Thank you all for your insight. I will carefully inspect the way the tires are seated around the rim and then continue with inflation with hearing protection. I did put on Velo rim tape too. Thanks again!

Q: a:

I was going for rim strips before I read it through. I'd still check them, make sure they are covering the spoke holes, no gaps. Make sure the tires fit too. Not every tire fits tight, but 700c is 700c and is pretty standard. And make sure the tube isn't pinched of course.

To inspect for pinched tube, push tyre sideways away from rim edge. Look down the gap between rim and tyre for pinched tube. Move over 6” and push tyre and inspect. Repeat until you’ve gone around entire circumference. Repeat for other side of tyre.

It’s just like checking oil level in your auto, can’t just eyeball it.

You roll the tire on a deflated tube, allowing it to pinch, then proceeded to pump to max.

OP changed from tubeless to tubed... is a tubeless strip not appropriate for a tube somehow - too thick?

A bad (or missing) rim strip will definitely puncture a tube, but it won't explode the way he described.

Tube was pinched, happens to the best of us lol. When I install tires and tubes I always use Talc/Baby Powder in the tires before I put the tube in, I make sure I roll the tire around real good tilting it as I do to make sure it is covered good, it really helps with pinch flats and the tire will bead easier.

Glenn

I'd never heard of the Nimbus tire so I looked into it -- it's basically a solid tire but with proprietary materials that Specialized claims mitigate the disadvantages of typical "airless tires" (Which have been around for more than a century and have always sucked. See Bicycle Tires and Tubes)

Anyway according to Specialized, the rims can take a standard clincher and tube.

My money's on pinching the tube during installation. I did that quite a few times when I was first learning about bikes before I refined my technique. Also had the surprise tube explosion more than once... that'll drive your laundry bill up LOL.

I aired both tires up to 55psi after I inspected everything....then took it for a ride and all was good, tires feel really smooth and the ride was way softer. Thanks everyone for your help!

What Anklework said. There was no reason to deflate the partially inflated tire after you checked that it was seated properly. Rolling the deflated tire on the floor likely caused the tube to shift, and it caught when you inflated a second time.

Glad you got everything sorted.

I've changed hundreds over the years, but last summer was weird. Twice in one week I did (I thought) everything right, loaded the bike into the truck and walked away. About 30 seconds later--BLAM!!! On two different bikes no less. Both cases were spokes punching through the rim strip. Live and learn. and learn. and learn.

'airless' and 'tubeless' are two Very Different things.

OP had Airless, as in Solid Rubber non-pneumatic tires. Specialized has been putting them stock on their Alibi city/comfort bikes... targeting the low speed, no-maintenance demographic