ggbo951a

i have spare tube from my prev-ly stolen bike:
27.5 2.10/2.35 first 650lb.
But my new bike is now 29/2.20. Will old size fit new bike? IT appears not , just to confirm here.

cyccommute 

It will stretch but you might be asking too much of the tube. A 27.5” tire sits on a 584mm bead. A 29er tire sits on a 622mm bead. The difference is 38mm or about 1.5”. That’s a bit too much of a stretch to make the tube fit.

Canker

it will work if you make it. Back during the switch over from 26er to 29ers I had several 26er tubes left that went into 29ers.

Bill Kapaun

I wouldn't presume the tube would stretch evenly enough, even if successfully inflated.
The odds of super thin spots seems too high for my peace of mind.
Take it a step further, and assume you eventually have to patch one of those thin areas and reinflate while out on the road. It might tear next to the patch????

Crankycrank

Since we have differing opinions and it could depend on the thickness of the tube wall (thin wall will stretch more easily) it's probably best to take off a tire, mount 650 tube on the rim and put enough air in it to match the width of the removed tire. Use your judgement to determine if you want to ride with it.

Rick

I have had more flats from tube failures over the years than actual penetration flats. I have to agree with cyccommute in this case. I am currently using Continental 26" Freeride tubes that are rated for 2.3" to 2.7" in my 2" Marathon Supreme tires.

Andrew R Stewart 

Well fitting an undersized tube is an old BMX racing hot rodding trick. Reduces rotating weight and any faster bleed off from stretched tube walls is easily topped off minutes before the starting gate. Besides the walk back from across most all BMX courses is pretty short... incase the tube rips during the race.

I strongly suggest getting the right tube, a good moment to also check out the rest of the tool kit too. I think of it like a Murphy's Law defense. Andy

Iride01 

The worst thing that is likely to happen is that it flats and you have to buy another tube. So either see if you can get some use from this one, or go buy another tube and gift the one you currently have to someone else with that size tire/rim..

You'll have to buy another tube at some point anyway. Besides tubes are inexpensive if you are just getting butyl.

wheelreason

Will it fit? Yes. Would I use it other than in an emergency? No.

veganbikes

Will it sort of work, kinda, possibly, but in an emergency how old is that tube and would you trust it to stretch that much if it is that old and if new, do you really want it to stretch that much probably not.

freeranger

You MIGHT get away with using it. But for the cost of a correctly sized tube and time to install it worth the chance the undersized tube MIGHT cause a flat while out riding?

ggbo951a

Oops it turns out as i just remembered, i have patch kit as well. Did not recall earlier, may be try that one as it seems worth.?
Yestrday went to dicks got confused by all these measurements but eventually figured out only to find they don't have add anything bigger than 27.5 or 700mm for my 29.

Crankycrank

29" is the same as 700c which is actually 622mm diameter. To make things easier, go by the "ISO" rating listed on most tires along with some other measuring systems. ISO gives you in millimeters the diameter and width of the tire. Here is a loooong article explaining everything but not necessary to read the whole thing as it gives comparison charts to the different sizing systems used in the world. So a 29" x 2" would be an ISO of 622mm x approx 50mm.Tire Sizing Systems (sheldonbrown.com)

Canker

Man people are such wimps. Tubes stretch easy and worst case is nothing. It really doesn't matter if you are running a stretched tube or a 29er if you run over something and it pokes a hole in the tube you have a hole in the tube and the air escapes. It would different if we were talking about running a 23mm road tube in a 2.8in tire but this is a minor stretch.

Rick

I don't like flats from defective over stretched tubes. I intentionally purchase the largest width and correct diameter tubes that are available and will fit in my tires.

ggbo951a

i thought 700 is 700mm? considering 2.54mm per inch that came up to 27.5 after crunching.

cyccommute 

Welcome to the confusing world of bicycle tires. 700C is a part of an obsolete French tire sizing system. There was a 700A, B, C, and D. There is also a 650A, B, C, and D size. The 700C uses a 622mm bead diameter with a 39mm tire diameter to make the outside diameter of the tire 700mm. A 700A used a narrower tire on a larger rim to make the outside diameter of the tire 700mm. The system worked the same with the 650 series. A 650B rim is 584mm (and a 33mm tire) to get to an outside diameter of 650mm. A 650C has a diameter of 571mm which used a 39mm tire to get to 650mm.

It’s a stupid way of doing tires and about the only thing you can do to understand it is to memorize the link that Crankycrank gave you.

Crankycrank

Pure coincidence. Read cyccommute's post above and also explained in Sheldon's tire sizing article.

ggbo951a

ok, i patched using patch kit now, see how it holds up, i dont want to 27.5 sizes, feel like throwing away but those are brand new and have at least 4-5. Wonder how I could donate to some places???
I am not bothering with selling, it is just more hassle than to get few bucks.