What would be a reasonable upper and lower limit guideline for 17x2.75 tubes?

[SneakyDingo]

How much range in tube sizes can you have before you start running into problems? e.g. if I have a 17x2.75 will it be fine to use that in a 17x2.5? 17x3? What about a 18x2.5? I've wondered this about the tubes since SomeGuyRides had his 3 flats and I went down the rabbit hole of looking at tube data.

In bicycles you can usually go up one size, down one size, same ERTO (rim size) and you're usually good. I'm assuming it's probably about the same, but I want to double check in case I decide to go 17x2.5 / 17x3 Shinko 244's with 17x2.75 tubes in both.

 

[dmonkey]

The OE tubes are good for 2.50 - 3.0 in wide tires based on the numbers on them. IMO you should only be running tubes that are recommended for your tire size, they're not very expensive. It's also a good practice, though not necessary, to replace your tubes with your tires when replacing based on wear. I keep the old tubes as spares.

70 mm ~= 2.76 in
80 mm ~= 3.15 in

Some other things for avoiding flats are maintaining proper tire pressure, you can upgrade to heavier duty inner tubes (I am running "Double Tough Inner Tubes"), eliminating debris and contamination when changing a tire or tube (this is where many people run into issues changing tubes away from home, they'll throw a new tube in a tire and also pack some gravel in there), addressing the cause of the previous flat (if you had a puncture in the tire and tube, even with a tubed tire you should plug the tire carcass), and you can use baby powder or corn starch when installing the tube which reduces friction but is controversial because once the tire's been submerged in water it can all gunk up together. Some folks on this forum are big fans of the tire slime sealant. Personally I think it's great in an emergency, but I wouldn't put it in the tube preemptively because it's an extra half pound of unsprung weight per tube, and it's goop that can throw off the balance of your tire which is very pronounced on this small of a bike.

 

[AZ7000']

but I wouldn't put it in the tube preemptively because it's an extra half pound of unsprung weight per tube, and it's goop that can throw off the balance of your tire which is very pronounced on this small of a bike.

If I miss the podium by 0.4 seconds I’ll take the slime out but prefer not changing tires/tubes ever…. Aren’t the double tough tubes heavier? And I hardly consider this bike small, weighs more then the 2 crf450x’s, and the 2 and 4 stroke 250 full size dirt bikes in the garage.
The good news is we can do whatever we want With our own bikes!!

As far as the original question I used the original tubes in my 3.0 tires

 

[SneakyDingo]

Apart from weight, I saw some mention of the thicker tubes starting to heat up at what is probably close to the maximum speed of the CT125, but not much else. Do the thicker tubes really make a difference?

I've seen people using slime but my experience with that is only ok; I use tubeless bicycle tubes and given that experience, that'd be one of those moments I turn up at the dealer for a tire change looking embarrassed with cash AND a case of beer to apologize. Nice beer, not Fosters.

While the obvious answer is run the right size (for installation and general use reasons), this seems a little more important when using two different sizes and designing a repair kit.

 

[dmonkey]

I don't care so much about acceleration and top speed from the weight as I do about ride quality. The heavy duty tubes are heavier, but it's balanced weight and the bike is sensitive to that at speed. I've ridden from Moab back to Denver with a slimed front tube in a ~30lb heavier 125cc bike (with cargo though) and it was a very noticeable difference compared to the ride there, good enough to get home but next time I'd rather just patch the tube, especially since like @SneakyDingo suggested, it's a pain to clean the slime out of the wheel next time you change tubes.
Not sure on the weight difference of the Double Toughs, but I'll be at my parts storage later this week and can let y'all know.
Size is relative, it's a "mini moto", "midweight" bikes are usually 400lb+, so it's a lightweight too. Certainly heavy for a 125cc though.

The heavy duty tubes do supposedly run hotter but I don't worry about it on this bike since people don't worry about it on TW200s or even DRZs. If you pick up a screw or a nail I'd expect it to go through any kind of tube, but the thicker tubes are less prone to pinch flats, less prone to being punctured by spoons (important if you don't have a lot of tire changing experience, they do really make a big difference here), and they're much easier to patch than the thin tubes - some of which are made of materials that a patch won't even properly bond to so you need to replace them for any puncture.
The OE tubes do take patches, and they're sized appropriately that you could fit them in a 2.50-17 front or a 3.0-17 rear. If I were running that tire combo and didn't want to carry two spares on a trip I'd just bring an OEM one. P/N: 42712-K2E-T02 (replaces 42712-K2E-T01)

 

[dmonkey]

For reference here are the tube weights including the valve nuts and caps that they come with. The back of the cap that comes with the Double Tough tubes is also a valve core remover which is nifty.

OEM IRC tube: 12.58 oz
Double Tough Inner Tube TR-6 2.75-3.00x17: 18.62 oz
So the Double Toughs are about 6.04 oz heavier each.

 

[m in sc]

unless you're racing, the heavy duty tubes are fine, Ive run them in some street bikes with zero ill effects.

 

[SneakyDingo]

For reference here are the tube weights including the valve nuts and caps that they come with. The back of the cap that comes with the Double Tough tubes is also a valve core remover which is nifty.

OEM IRC tube: 12.58 oz
Double Tough Inner Tube TR-6 2.75-3.00x17: 18.62 oz
So the Double Toughs are about 6.04 oz heavier each.

Thanks for following up on this request