Do you size up your tubes for 25mm tires?

[FastforaSlowGuy]

My new wheels should be coming in this week from Ergott (pics to come), and I plan on running 25 mm Veloflex rubber on them (Pacenti SL23 rims). I have a stash of standard 18-23 mm tubes. Am I risking pinch flats by asking those things to stretch to fill the extra volume?

[exapkib]

I've used 18-23 tubes in 25mm tires (GP4000s) for years--never a problem.

[Aaron O]

+1 - I've used them in 28s. A shop owner told me ages ago that tube sizes were just a way to make shops carry more stock.

[4Rings6Stars]

+1 - I've used them in 28s. A shop owner told me ages ago that tube sizes were just a way to make shops carry more stock.

I will one up A-aron...I used 23mm tubes in my 32mm Paselas for a year of commuting with zero flats. My most recent tube order was for larger tubes since I don't run anything narrower than 28mm these days. They are noticeably larger than the 23mm tubes I previously had so it's not all hype....but I still had no problem using skinny tubes in fat tires.

[FlashUNC]

It's a bladder. It'll just fill the space around it. You'll be fine.

[DRZRM]

Yeah, based on recommendation from my then local shop I used to carry the smallest 26" MTB tubes I could when riding so they would take up less space in my bag (1" tubes for ~2" tires). Never had a problem, though I suspect I may have had blowouts rather than slow leaks when punctured sometimes. Doubt you'll tell a difference with 23mm tubes in 25mm tires, and for the weight weenie in all of us, you'll save a few grams.

[thirdgenbird]

I've heard of guys using 26in tubes in 29in tires. It may not be optimal, but tubes will grow a lot. Try putting air in one without a tire to contain it.

[Kirk Pacenti]

They're rubber, they'll stretch a little bit. ;)

[shovelhd]

I do but that's just me.

[foon]

I will one up A-aron...I used 23mm tubes in my 32mm Paselas for a year of commuting with zero flats. My most recent tube order was for larger tubes since I don't run anything narrower than 28mm these days. They are noticeably larger than the 23mm tubes I previously had so it's not all hype....but I still had no problem using skinny tubes in fat tires.

Same here. I would use the skinny tube in 32mm without a second thought. Not really more flat prone in my experience.

[Kirk Pacenti]

I forgot to mention that I use 26 x 1.25" tubes in all of my 27.5 x 2.3" MTB tires... well, in the ones that aren't tubeless.

[leooooo]

You will be fine. I bought two boxes of 18-23mm tubes on eBay (24 tubes total) for my road bikes.

Having so many tubes, I found no reason to buy separate tubes for my 32mm commuter tires. They have functioned perfectly fine.

[JAGI410]

I use 26x2.3-2.5 tubes in my 26x4.0 bike. There's no reason to upsize for the small differences in road tire sizes.

[RedRider]

Don't forget to use less air pressure in the 25s than you do for 23s. This will vary by tire, your weight and road conditions.

[tuscanyswe]

I will one up A-aron...I used 23mm tubes in my 32mm Paselas for a year of commuting with zero flats. My most recent tube order was for larger tubes since I don't run anything narrower than 28mm these days. They are noticeably larger than the 23mm tubes I previously had so it's not all hype....but I still had no problem using skinny tubes in fat tires.

Ive used 23s in 32mm paselas too but no such luck for me. I wouldent use 23s in anything that big unless i have no other.

[David Tollefson]

I like to shoot for the low end of the tube range in my tire size -- 23-25's for 23mm tires, 28-32's for 28mm tires. Sure, they're a little heavier (but I'm not racing, so I really don't care), but I think I get a bit better flat protection but doing this.

[liray]

"You may be perfectly OK, or may experience several possible problems:

The area near the valve on the tube is the stiffest part, and does not expand as easily as the rest when over-inflated. This may result in a slight depression in the tire near the valve that you will feel on every revolution (especially if you start thinking about it). Not a significant reliability issue, but it can be a comfort issue.
As the tube expands in its width from over-inflation, it expands even more in its overall circumference. The tube can, before it gets "locked in" to the sidewalls of the tire, expand enough that a portion of the tube telescopes on itself, in the short term creating a lump, and in the only slightly longer term creating a stress point that will result in a fairly sudden deflation of the tire.
And obviously, the tube is being placed under more stress than it's designed for, and it's apt to simply fail, especially near the valve.

I wouldn't hesitate to use the (slightly) wrong size tube for a relatively brief period, as an emergency measure, but I wouldn't regard such a repair as trustworthy over the long haul." - http://bicycles.stackexchange.com

Point #3 would probably be your biggest issue, having seen this exact thing happen multiple times at our shop. But again, you might be perfectly fine. Its still not ideal, but you can do it.

[charliedid]

"You may be perfectly OK, or may experience several possible problems:

The area near the valve on the tube is the stiffest part, and does not expand as easily as the rest when over-inflated. This may result in a slight depression in the tire near the valve that you will feel on every revolution (especially if you start thinking about it). Not a significant reliability issue, but it can be a comfort issue.
As the tube expands in its width from over-inflation, it expands even more in its overall circumference. The tube can, before it gets "locked in" to the sidewalls of the tire, expand enough that a portion of the tube telescopes on itself, in the short term creating a lump, and in the only slightly longer term creating a stress point that will result in a fairly sudden deflation of the tire.
And obviously, the tube is being placed under more stress than it's designed for, and it's apt to simply fail, especially near the valve.

I wouldn't hesitate to use the (slightly) wrong size tube for a relatively brief period, as an emergency measure, but I wouldn't regard such a repair as trustworthy over the long haul." - http://bicycles.stackexchange.com

Point #3 would probably be your biggest issue, having seen this exact thing happen multiple times at our shop. But again, you might be perfectly fine. Its still not ideal, but you can do it.

This ^ but I tell customers pushing one size fine but beyond that...This ^

[smead]

This ^ but I tell customers pushing one size fine but beyond that...This ^

++1. A grossly undersized tube will be more prone to fail around the spoke holes if rim tape is marginal and the tube is stretched more. Moreover, a stretched/thin tube is more likely to fail from heat buildup on descents. PeterB and I experienced this first hand on a tandem where we got 7 rear flats in 200 miles using 18-23 tubes all day in a 30 tire after the first flat took care of the 28-32 tube. The last flat was a 40+ MPH blowout on a huge descent :eek: ..... Thankfully it was not the front.