After reading a few threads here and there, I am beginning to wonder why some people use a smaller tube on their tires? For instance, I just read the “Nimbus stealth wheel build” thread. There, he/she used a 29er tube on a 36 inch rim. I read somewhere else someone used a 26er tube on a 29er. Is there any benefit to doing this, or am I missing something? I 'm just currious about this.
It’s common with 36ers because the standard tube weighs an absoloute ton, something like 400g compared to 150g for a 29er tube. Right out at at the rim this much weight will make a serious difference to performance, I’ve heard it compared to going down a crank size. However, getting a 29er on a 36 can be a real pain, very easy to burst it, I bought two tubes for this purpose and wrecked them both.
I run a 29er tube in my coker and it does make a huge difference. When i first started out Bill Manning gave me a few tips after I had ruined 3 or 4 tubes trying to get it to work.
Tip #1 - Over-inflate the hell out of the 29 inch tube until it is much past the 36 inch diameter and let it stretch out over night, (or at least a few hours).
Tip #2 - Deflate the tube until it is just below the diameter needed and be careful not to pinch it on the sidewalls of the rim as you seat the tire.
Tip #3 - As you gradually inflate for the first time, roll the tire around with weight on it to get it to settle properly.
Finally, take your time. Now when I pop a tube it is usually because I am in a hurry. I could never go back to a normal coker tube. This and adjusting my seat angle have been the greatest performance related adjustments I have made to my coker.
Well, the 29" tube that my buddy set up up with blew today. I was actually in my local unicycle shop and the proprieter was mounting it between customers. At a point that luckily I was the only other person in the store … BOOOM!! … it sounded like a shotgun went off. When I pulled it off there was about a 18" gash along one of the seams.
My buddy put in higher quality 29" tubes than I have on hand, but I’m now taking osmudno’s advice as I try to reassemble this thing for a 100k ride next weekend. I wish I had a spare 36" aside from the one in my old wheel, but at least I’ve got that around for a quick swap out if I need it.
Here’s the original thread where putting 29" inners in 36" tyres was first done: Tubeless Coker
There’s not much benefit to using a 26" tube in a 29" wheel that I can see, as pinch flats will be more likely. This isn’t an issue for 36" tyres, as they are so thick (built like car tyres!) that pinch flats are unlikely. It is useful to know that a 26" inner will fit a 29" tyre in emergencies where no 29" inners are available.
I think the idea of using 26" tubes in a 29er is to get a wider tube. I don’t have a 29er but I could tell you that it would be much easyer for me to find a 26"DH tube than a wide 29" tube and if it is between a thick wide slightly to small tube and a thin skinny tube with the right diameter the thicker wider tube should have better pinch resistance.
I have a 700C tube in my 36er. The weight difference is definitely noticeable. I have been using a CCM 700x32 tube for 7 months no problem. Installation was a breeze.
Yep. Plus, most shops will have a 26 x 3 tube (either for DH bikes or for cruiser tires), but not all that many carry 29er tubes. The 29er tubes also cost about 1/3 more than a DH 26er tube.
A year or two ago someone posted a storey of his coker tyre exploding at work, being called in to the police as gun fire and armed cops invading his building. Really quite funny.
The tip to over-inflate and let it sit for at least a few hours is a necessary trick. But even with that trick it can be difficult to get a Coker tire on without pinching the tube. I’ve killed several 29er tubes during the install even when the tubes had been pre-stretched.
I was over at Tom Blackwood’s over the weekend for a ride and we replaced the worn tire with a new tire. I killed two 29er tubes getting the new tire installed. One strike against was not having enough time to pre-stretch the tubes for several hours. We ended up putting in a Coker tube. After struggling with the 29er tubes to try to prevent pinching the install of the Coker tube was very easy.
I’ve stopped using 29er tubes in my Coker because of the difficulty installing them and my lack of trust in their reliability. When replacing Tom’s tire the previous tube was a 29er. I inspected the tube and found small tears around where the rubber is thicker right around the stem. The tube wasn’t leaking because of the tears but I have to wonder how much life the tube had left in it before it would have failed. I just don’t trust the 29er tubes any more.
Before you stopped using 29er tubes (which I believe I will once I can get some backup 36" tubes) did you have a preference on brand? My buddy who put the now-blown 29" tube on was very specific about Schwalbe tubes, but I don’t know that he pre-stretched them.
I’ve always used the Schwalbe tubes. I can’t find 29er tubes with a schrader valve locally so I have to order them on the web. If I’m going to order from the web I might as well order directly from Schwalbe at their web site.
saskatch, is the 700C tube schrader? I can never seem to find schrader ones.
yup, around here basically everything is schrader, I don’t think I have actually ever seen anyone using a presta valved tube, not that I spend much time looking at their valve stems 
I was thinking about this the other day. I once read about touring bicyclists drilling a second valve hole in their rims and running with two tubes. The idea being that a single flat wouldn’t require an immediate repair.
I wonder if this could be done with two 29er tubes in a 36er. Since each tube would only be about 1/2 as full as usual, they might be less likley to rupture.
Of course you lose some of the weight advantage.