Who's Had a 29" Tube Blowout When in a Coker Wheel?

I’m considering doing the 29" tube in the coker upgrade, but after having a blowout with a 36" tube at RTL, I’m sort of afraid. Have many people had troubles with the upgrade?

I’ve heard of quite a few people that have had that problem, but your stretching a tube, then putting relatively high pressures in it. It is bound to go really. Why do people do it, are the 36" tubes too heavy for some and affect the handling and performance somehow?

Saving around about 0.5 lbs around the outside of your wheel is a huge difference.

You can definitely feel the difference in weight, its really noticeable but I blew two 29er tubes in one week so I just decided to use the coker tube. Its not worth risking it blowing out on a long ride.

I tried it once and blew two tubes just trying to get it in place, never actually got the chance to ride it.

I had a 29" tube in my 36" wheel (while I had it) with no problems at all.

Went in fine, stayed in fine, never burst. Had it at about 50psi with the Wheel TA tyre.

I totally noticed the difference, enough to make me think about going down a crank size.

Just make sure to get as fat a 29" tube as possible, then it’ll get stretched less. A bit.


I bought Tom’s coker and that tube was in there until a few weeks ago when I got my new wheel, with no problems at all, not even a single puncture. I’ve ridden a couple of thousand miles of mostly cross-country routes in that time. I don’t use a very high pressure though, usually between 25 and 30psi.

I did actually burst that tube while fitting it to my new rim, but I was being lazy and trying to use high pressure to seat the tyre bead - didn’t work, and blew the tyre off the rim. I put another 29er tube in and have had no problems since.

I don’t think it’s unreliable as long as you fit it carefully and don’t pinch the tube - and get a nice wide 29er tube like Tom mentioned. Also, it’s worth stretching the tube first by leaving it pumped up fat (not in the tyre) overnight before fitting.


I have run 29er tubes in my 36 for the last 3 years with no problem. One of them stayed in for well over a year before it finally got a small leak from a thorn. I ride more off-road than on, and I love the lighter weight.

Below are the things you can do to keep from having any problems. Actually, all of these steps should be taken with any tire mounting, it just becomes a little more critical to do it right with the 29er tube in 36” wheel scenario. Next time I change one I will take photos to go with the steps.

  1. Before you put the 29er tube in the tire, air it up to the size of the 36 tire to pre-stretch it. Let it sit for a while that way, or you can help it along by manually stretching it with the air in it. In the valve stem area, stretch the rubber with your fingers to reduce the amount it necks down in that area.

  2. Let most of the air out. Put talcum powder (plain or baby powder) on the entire surface of the tube and dust some in the tire. The powder is really important. It lets the tube slide more easily against the tire and rim surfaces so that the amount of stretch can equalize around the wheel, preventing any thin, overstretched areas.

  3. Put one bead of the tire onto the rim. Let most of the air out of the tube. Put the tube into the tire starting with the valve stem. Once it is in, air the tube up enough so that it can’t wrinkle or fold over. This is important. Also, if the tube appears to be stretched in one area more than another, use your hands to even it up.

  4. Put the second tire bead on the rim starting at the valve stem, and be sure to push the valve stem in and get the tire bead under the tube. Because the 29er tube is thinner, it is much more likely to get pinched under the tire bead than the stock 36 tube. I think this is where most problems arise, and it doesn’t have anything to do with bad tubes, or overstretched rubber. If the tube is caught under the tire bead it will pop when airing it up, or shortly thereafter.

  5. Work the rest of the bead on using tire levers only when needed, and be very sure to squeeze the tire beads together on the side opposite where you are pulling the bead over, so that the beads will drop into the center of the rim and allow the side you are working to fit over the rim. Spring clamps are handy for this.

  6. Air the tire up to the point where it just gets firm, then stop and let the air back out completely. This lets the tube equalize its stretch around the rim, and allows any folds in the rubber to straighten out.

  7. Air the tire up slowly, watching the beads to see that they seat properly. The talc helps them pop into place easier. If it doesn’t seat the first time, let the air out and try again.

This wasn’t meant to be a complete how-to, so I may have left something out. I am no tire authority, and these steps are just what I have accumulated starting with what my Dad taught me 40 years ago and refined while mounting many bike, motorcycle, and unicycle tires over the years.


Well, I’ve got the tube. It’s a higher quality one and it’s currently stretching in my basement. No explosions yet :wink: ! It’s currently quite a bit larger than 36" x 2 1/4 (coker tire), so I think it’s going to work! I’ll keep a 36" tube on me just in case though.

Maybe I’ll put my brand new nightrider tire on while I’m at it… more weight but a better tread.

How about blowing the tube during pre-inflation with a heat gun and then let it cool so the stretch becomes more permanent.

Interesting idea, but I wouldn’t want to try it. This could seriously weaken the rubber in one specific area if it got too hot. The tube would bulge and fail at that point. Maybe putting the whole thing in an oven :roll_eyes: … A really cool oven.

Hey Eric, I rode a 29er tube for quite a long time, when I get home I will probably be installing one again as well. I found them very very reliable and installed two by myself without much issue, then when I went to Uninam, I tried installing one there and I got a flat so I stuck to the 36er tube.

The 36er tube will definitely be more reliable, but the 29er tube is great once you have it installed properly, but you will never know if its in properly until it pops, so it’s always a gamble.

I ride 29er tubes exclusively in my 36. Not only is the weight difference quite noticable, but 29er tubes are $3.99 at performance bike. :slight_smile:

I’ve probably trashed four 29er tubes in my life, but now I get them in cleanly every time. My first few, I talc’d as was mentioned above, but if you get it in with a bit of air in it (so it stays round instead of flattening out around the rim, sneaking under your tire beads), and massage it with your hands until you think that it’s pretty close to evenly stretched all the way around, it should work just fine.

That said, I have had three blowouts of my Nightrider tire: one at 65 PSI, one at 60, and one at 50. I think it’s a problem with the tire, though, and not a consequence of my having used a smaller tube. A 36" tube pushes out on the tire just as much as a 29" tube does, so I don’t see why one tube would cause the tire to have a better chance of blowing off the rim. I could imagine a 29er tube popping inside of the tire, without the bead coming off the rim’s clincher, but … that just doesn’t really happen. I’ve never heard of it, and it’s never happened to me.

The only issue with running 29er tubes is that if you DO get a legitimate flat, you can’t patch the tube. For that reason, I always bring a 36er tube with me as a spare, along with 10-12 patches, so if I get MORE flats, I can patch the 36" tube. It’d be better for me to carry one more 29er tube, so I can still ride a 29" tube after my first flat, but honestly, my only flats have been pinch-flats from me putting the tire on dumbly, or blowouts of my tire (3). I’ve never flatted from riding. I think it took Sam Wakeling something on the e order of 5,000 miles to get his first, true, conventional flat tire from something on the road.

My advice (take it or leave it :)) is to go a 29er tube. Lighter, CHEAPER, and your tire is so flat-proof anyway that chances are you’ll never have to replace it if you get it in right. And if you run 29er tubes, you’ll learn how to get it in without popping it :slight_smile:

It comes down to how much risk you are willing to take for a flat or tube failure during a ride and whether the inconvenience of a ride being interrupted is worth it.

You’re also going to get different responses about experiences from different people because there are a variety of different Coker rims out there. I have one of the first generation Airfoil rims. I honestly believe that it is a little bit larger than other Airfoil rims of the same generation because getting a tire on that rim is difficult. I’ve said more swear words and pinched more tubes putting tires on that rim than any other rim.

I used to use Schwalbe 29er tubes. It worked. It was a ***** to get a 29er tube on that rim and I pinched and ruined a few tubes in the process. But once I got one to work it stayed working. I stopped using the 29er tubes when the risk of a flat during a ride became more than I was willing to bear. I got a flat during a ride. Had to call to get picked up to get back home. Went through my stockpile of 3 or 4 Schwalbe tubes trying to get a new tube on. Some of the tubes had overly thin spots when I inflated them for pre-stretching. One tube even blew out during the pre-stretching procedure. I gave up and went back to the old trusty Coker tube and have used a Coker tube ever since. Never had a flat or an issue with a Coker tube.

If you do use a 29er tube I’d be wary of keeping the same tube in for more than a year. The rubber around the valve stem is overly stressed and likely to fail on you if you leave the same tube in too long.

Weigh your risks. Make your choice.

I don’t know why people aren’t going back to Tubeless kits.

It saves about the same amount of weight, and gives a much nicer, springier ride.

The main issue in the past was the crappy quality of several batches of Coker tyres. It ended up with beads blowing out.

I believe the newer rims and Nightrider tyres should solve some of these issues. In fact, I can’t think of a better combination right now. Tyre’s actually designed to fit the rims.

I’ve just been doing touring on my 36 (with some casual biking friends), using a 29er tube in Nightrider tyre, and I got a puncture. A good old-fasioned thorn-through-the-tyre one. I was enough of a weight-weenie/muppet to not have a spare tube, so I had to try patching it. But the patch worked fine, and the tyre went back on without a problem (with some washing-up liquid and partially inflating the tube before putting on the second bead). I was quite relieved to have it all go so well though - otherwise it would have been a case of finding the nearest to Bad bike shop (it was near a little German village called Bad!). I would recommend having a spare tube (either a 29 or 36 depending on how confident you are) while touring though.


I also run 29er tubes. Scott posted a pretty thorough guide on how to make it work. I’ve had them run for hundreds of miles without problems. Like Chuck, I carry a spare 36er on long, unsupported rides just in case. It is definitely worth the effort to get it to work, both for performance and economically.

So that’s why there was a flat tube in your wheel bag…

Anyway, for several reasons I’m going to wait until I get back from France to do this conversion. I’m also toying with the idea of a tubeless coker depending on the cost. It seems far more reliable, but it’s also costs more than 3.99 :stuck_out_tongue: . Cost isn’t an issue at the moment since I won an extra 36 tube at RTL (most breakdowns and most injuries went to team North American Youth)

Are you guys using the regular cheap 29er tubes or the thicker thorn resistant muni 29er tubes?

I’ve had a 29’er tube in my dave stockton wheel for probably two years now, and I really notice the difference between it and my 36 tube in my rtl nightrider. I’m actually going to go pick up a 29’er tube and follow scott’s excellent instructions for installing them.

I did try to fit a schwalbe tube in my nighrider, but it was old and I wasn’t particularly careful, so I had a blowout during a long ride, which kind of sucked. I’ll be nicer to the wheel this time around.