Tube Sizes

[Mutt Daeng]

I have a hybrid bike with 700x32c tyres. What range of tube sizes can I use?

The reason I am asking is that I just had a puncture and the existing tube was 700x28 and not 700x32 as I was expecting.

[StreetCowboy]

You can use the closest size they have in the shop.

 

The tubes will be marked with a range, and I won't use anything more than 1 size outside the range (i.e. if its marked 28 - 32 I wouldn't put it in a tyre smaller than 25 or larger than 35).  Unless I was out on the road and it was the only tube I or my mates had.

 

I'll need to review my current spare tube, as the new hybrid bike has 28 tyres on it, and can't take anything bigger thanks to the mudguards, while the cyclocross bike that I do my long rides has 35 - 38 mm tyres (I think 35 mm wide 38 mm deep); I think the tubes I have are mostly 28 - 32s, which I believe I could reasonably safely put in a friend's 25 mm tyres if need be.

 

The risks are:

- Tube bigger than tyre, loose tube can be caught under tyre bead and burst shortly after fitting: to reduce this risk, partially inflate the tube before seating the tyre bead on the rim.  Check you can pinch the tyre beads together under the tube before fully inflating it.

- Tube smaller than tyre, tube is stretched and more vulnerable  to puncture by foreign objects: if they are good quality tyres, this should be much less of a problem, particularly if the tyres have some sort of puncture-resistant layer.

 

Since I fitted the Schwalbe marathon 38s I have done over 3,000 km without a puncture. Now I'll probably get one in the lift going downstairs before I even start Saturday's ride. 

 

SC

[Deserted]

28mm is absolutely fine for a 32mm tyre. Have you checked the inner wall of the tyre to check for foreign objects? 

[Mutt Daeng]

16 hours ago, StreetCowboy said:

You can use the closest size they have in the shop.

 

The tubes will be marked with a range, and I won't use anything more than 1 size outside the range (i.e. if its marked 28 - 32 I wouldn't put it in a tyre smaller than 25 or larger than 35).  Unless I was out on the road and it was the only tube I or my mates had.

 

I'll need to review my current spare tube, as the new hybrid bike has 28 tyres on it, and can't take anything bigger thanks to the mudguards, while the cyclocross bike that I do my long rides has 35 - 38 mm tyres (I think 35 mm wide 38 mm deep); I think the tubes I have are mostly 28 - 32s, which I believe I could reasonably safely put in a friend's 25 mm tyres if need be.

 

The risks are:

- Tube bigger than tyre, loose tube can be caught under tyre bead and burst shortly after fitting: to reduce this risk, partially inflate the tube before seating the tyre bead on the rim.  Check you can pinch the tyre beads together under the tube before fully inflating it.

- Tube smaller than tyre, tube is stretched and more vulnerable  to puncture by foreign objects: if they are good quality tyres, this should be much less of a problem, particularly if the tyres have some sort of puncture-resistant layer.

 

Since I fitted the Schwalbe marathon 38s I have done over 3,000 km without a puncture. Now I'll probably get one in the lift going downstairs before I even start Saturday's ride. 

 

SC

Thanks SC. That's exactly the info I was looking for.

I bought a couple of these tubes off Lazada and got a shock when I saw the difference in size (partially inflated) with the existing 28 tube (hence my OP). I then let some of the air out and it's size reduced considerably allowing me to easily fit it onto the rim. I went on my usual morning ride today and it seems to be OK.

[Mutt Daeng]

16 hours ago, Deserted said:

28mm is absolutely fine for a 32mm tyre. Have you checked the inner wall of the tyre to check for foreign objects? 

Yes, I did check the inner wall surface.

Thanks

[StreetCowboy]

9 minutes ago, Mutt Daeng said:

Thanks SC. That's exactly the info I was looking for.

I bought a couple of these tubes off Lazada and got a shock when I saw the difference in size (partially inflated) with the existing 28 tube (hence my OP). I then let some of the air out and it's size reduced considerably allowing me to easily fit it onto the rim. I went on my usual morning ride today and it seems to be OK.

You can easily burst a tube inflating it outside the tyre at quite low pressure.  It's the tyre that resists the pressure, rather than the tube.

[StreetCowboy]

After my boast a few months back, I got my first puncture in a long time; a fairly slow deflation over minutes rather than seconds.

 

We found a small hole in the tyre, so we put a patch on the inside of that.  We patched the tube, but while pumping up to target pressure the valve stem broke free from the tube.  It was a ridiculously long stem (60 mm?), presumably because the chap in the bike shop  thought I needed to compensate for something.  I took offence and said "What do you mean by offering me a valve stem that length?" but it was all that he had in the shop.  He said that they were for aero wheels, but I'm sceptical because people with aero wheels don't ride 35 mm tubes.

 

Anyway, back to the topic of this thread, and my replacement tube into my 35 x 38 mm tyre is a 28 - 32 mm tube, so let's see if that punctures soon because of the stretching.  I intend to put a little blob of patch adhesive into the outside of the hole, to try and seal that as best I can, but I'll probably condemn the tyre soon; it has done over 5,000 km, so it lasted longer than the chain.

 

SC