25/28 Inner Tubes

On Sun, 06 Nov 2005 12:54:16 GMT, "nobody760" <[email hidden]>

Quoted message said:

I cant find the address of where I purchased ten 18/23 tubes on-line a
while back that were a good bargain. Anyone got a recommendation? I
need 25/28 ones this time.

Cheers.

Please be careful when you purchase inner tubes. Be sure they fit your tyre.
For example I use Panaracer Stradius Pro 700C x 26 on Mavic Open Pro rims. So
I expected that a good manufacturer like Michelin would have a tube that would
fit. So I bought some Airstop A2 tubes labelled 25/32-622/635. A 635 tube is
longer than is required for 700C. There is no spare room in my setup so I
can concude Michelin do not have a tyre that fits 700x25.

A worse case, I also use Continental Contact on my commuter. Continental
supply a free inner tube type "28 All". This tube supports tyres from 700C
32-48. Unfortunately I use 700C x 28. Despite the tubes name this does not
fit. Contis own catalogue states this tyre is for 32mm up but they still
supply this 'free' with 28mm tyres. STUPID.

Vittoria Butyl tunes are usually about £2 each when bought in 5 or 11 lots and
can be got from ribble. wiggle etc and probably your lbs.

www.wiggle.co.uk cheapest
www.ribblecycles.co.uk

Ian Blake said:

Please be careful when you purchase inner tubes. Be sure they fit
your tyre. For example I use Panaracer Stradius Pro 700C x 26 on
Mavic Open Pro rims. So I expected that a good manufacturer like
Michelin would have a tube that would fit. So I bought some Airstop
A2 tubes labelled 25/32-622/635. A 635 tube is longer than is
required for 700C. There is no spare room in my setup so I can
concude Michelin do not have a tyre that fits 700x25.

Tubes fit a range of sizes because they expand.

Panaracer tyres are narrower than what it says on the label, but still
perhaps you are inflating too much before fitting?

18-23 tubes also fit 700x25 (including Michelin A1): in fact they're
easier to fit and weigh less. Reliability and air-holding is only
slightly lower.

~PB

Pete Biggs said:

Tubes fit a range of sizes because they expand.

Quoted message said:

Panaracer tyres are narrower than what it says on the label, but still
perhaps you are inflating too much before fitting?

As someone who rides 10000 miles a year some on lightweight tyres I am well
practiced fitting tyres. My friend in the local bike shop, who fits many tyres
every day, is also unable to fit A2s to these tyres. He swapped the unused A2
tubes I had for Vredestein.

Quoted message said:

18-23 tubes also fit 700x25 (including Michelin A1): in fact they're
easier to fit and weigh less. Reliability and air-holding is only
slightly lower.

~PB

The point I was making is the A2 is 635-25/35 is not 622-25 the initial
circumference uninflated is too long. Not too wide, too long. In the wider
tyres there is room to wiggle in a non catastrophic way. In the narrower tyres
where there is no space to wave it can be fitted but kinks up and down
guarenteeing impact punctures almost immediately. The tyre isn't even round!

An undersized tube can be stretched but a overlong tube can not be compressed.
Michelin A1 is for 622 only not for 635 and has the correct circumferance
although personally I prefer not to overstretch a tyre unnecessarily. I like
to think they are specified for a reason.

I am not criticising Michelin in general. Michelin make good quality tubes and
with previous tube ranges this problem did not exist. In the current A2 family
it does.

I am not particular about which tube I use with these tyres I use Vredestein
tubes 18/25 - 622/630. These fitted without any problem. I also use Vittoria
Ultralite 25/28 - 622/630 which fit comfortably. I have used Hutchinson tubes
as well without problems.

Significantly Vittoria and Vredestein are specifying a max circumferance of 630
not 635.

true

ryano said:

true

What is?

--
Tony

"The best way I know of to win an argument is to start by being in the
right."
- Lord Hailsham

Ian Blake said:

The point I was making is the [Michelin] A2 is 635-25/35 is not 622-25

the

Quoted message said:

initial circumference uninflated is too long. Not too wide, too long.

In the wider tyres there is room to wiggle in a non catastrophic way.
In the narrower tyres where there is no space to wave it can be
fitted but kinks up and down guarenteeing impact punctures almost
immediately. The tyre isn't even round!

I don't see how an inner tube can deform a tyre or unseat it. A problem
with the tube may affect its durability or rolling resistance but how can
it put the tyre out of round? Does it not do whatever it has to do to
conform to the tyre?

Quoted message said:

An undersized tube can be stretched but a overlong tube can not be
compressed. Michelin A1 is for 622 only not for 635 and has the
correct circumferance although personally I prefer not to overstretch
a tyre unnecessarily. I like to think they are specified for a
reason.

~PB (reply from uk.rec.cycling x-posted to rec.bicycles.tech)

Ian Blake said:

As someone who rides 10000 miles a year some on lightweight tyres I
am well practiced fitting tyres. My friend in the local bike shop,
who fits many tyres every day, is also unable to fit A2s to these
tyres. He swapped the unused A2 tubes I had for Vredestein.

What is the actual width of your Panaracer "26"? If less than 25mm then
the A2 is not supposed to be for it.

BTW, the Vredestein Race tubes I've used have had too-small and round
reinforcement pads around the valve. End result, with about three tubes,
was small holes either side of the pad, just caused by abrasion or stress.
The butyl isn't of the most flexible type either.

~PB

Pete Biggs said:

I don't see how an inner tube can deform a tyre or unseat it. A problem
with the tube may affect its durability or rolling resistance but how can
it put the tyre out of round? Does it not do whatever it has to do to
conform to the tyre?

Not if it's doubled up somewhere. That'll give you a really bad
out-of-round spot (out of round as in whole-wheel round, not casing shape)
plus a good opportunity to push the tyre off the rim if you inflate it to
the right pressure.

Jasper

Jasper Janssen said:

Quoted message said:

I don't see how an inner tube can deform a tyre or unseat it. A
problem with the tube may affect its durability or rolling
resistance but how can it put the tyre out of round? Does it not
do whatever it has to do to conform to the tyre?

Quoted message said:

Not if it's doubled up somewhere. That'll give you a really bad
out-of-round spot (out of round as in whole-wheel round, not casing
shape) plus a good opportunity to push the tyre off the rim if you
inflate it to the right pressure.

I've used too large a tube (700c) in a 22" child's tire by folding it
and had no trouble. The same goes for a MTB fat tire in which a road
tube is too long but small in cross section. Neither of these
mismatches caused problems in use. Of course the folds aren't good
for the tube and the uneven distribution makes wheel balance worse
than usual, but even that caused no problems.

Unless the tube gets caught under the bead of the tire (the usual
cause for static blow-offs) so that it doesn't seat correctly, I don't
see how an oversized tube would push the tire off the rim.

Have you tried this?

Jobst Brandt

Quoted message said:

Jasper Janssen said:

Not if it's doubled up somewhere. That'll give you a really bad
out-of-round spot (out of round as in whole-wheel round, not casing
shape) plus a good opportunity to push the tyre off the rim if you
inflate it to the right pressure.

I've used too large a tube (700c) in a 22" child's tire by folding it
and had no trouble. The same goes for a MTB fat tire in which a road
tube is too long but small in cross section. Neither of these
mismatches caused problems in use. Of course the folds aren't good
for the tube and the uneven distribution makes wheel balance worse
than usual, but even that caused no problems.

Unless the tube gets caught under the bead of the tire (the usual
cause for static blow-offs) so that it doesn't seat correctly, I don't
see how an oversized tube would push the tire off the rim.

Have you tried this?

Not so much tried as 'been bitten by it'. I can't explain it either, but
several times a tube that was slightly too long ended up with a short
folded section (3-7 cm I'd say), and it resulted in a bad 'bump' at that
spot. One possible explanation is that I may have been less than diligent
about getting the bead properly seated, and that part of it was still in
the rim well thus allowing the tyre to bulge at the opposite end. Usually
when you inflate a tyre it'll pop into alignment naturally, but maybe
somehow the doubled up section interferes with that. These were all 622/37
tyres, incidentally, with tubes either of the 622/35-45 region or the
28-35 region, if I got the wrong one.

I just don't know how it works.

Jasper

Pete Biggs said:

What is the actual width of your Panaracer "26"? If less than 25mm then
the A2 is not supposed to be for it.

I have to point out again that 635-25 is too long for a close fitting 622-25.
As I have already explained width has little to do with the problem
encountered. I compared my last remaining A2 against the Vittoria tube. The
width is about the same but the Vittoria (630-25) that fits is shorter.

Probably a more important factor than width of the tyre is how high it stands
over the rim. A tall tire will have more room for a overlength tube. As you
point out Panaracer Stradius Pro are not large volume tyres so I encountered
the problem.

Jasper Janssen said:

On Mon, 07 Nov 2005 17:21:37 GMT, [email hidden]

Quoted message said:

Jasper Janssen said:

Not if it's doubled up somewhere. That'll give you a really bad
out-of-round spot (out of round as in whole-wheel round, not casing
shape) plus a good opportunity to push the tyre off the rim if you
inflate it to the right pressure.

I've used too large a tube (700c) in a 22" child's tire by folding it
and had no trouble. The same goes for a MTB fat tire in which a road
tube is too long but small in cross section. Neither of these
mismatches caused problems in use. Of course the folds aren't good
for the tube and the uneven distribution makes wheel balance worse
than usual, but even that caused no problems.

Unless the tube gets caught under the bead of the tire (the usual
cause for static blow-offs) so that it doesn't seat correctly, I
don't see how an oversized tube would push the tire off the rim.

Have you tried this?

Not so much tried as 'been bitten by it'. I can't explain it either,
but several times a tube that was slightly too long ended up with a
short folded section (3-7 cm I'd say), and it resulted in a bad
'bump' at that spot. One possible explanation is that I may have been
less than diligent about getting the bead properly seated, and that
part of it was still in the rim well thus allowing the tyre to bulge
at the opposite end. Usually when you inflate a tyre it'll pop into
alignment naturally, but maybe somehow the doubled up section
interferes with that. These were all 622/37 tyres, incidentally, with
tubes either of the 622/35-45 region or the 28-35 region, if I got
the wrong one.

I just don't know how it works.

Air pressure is normal to the surface of whatever is containing it. What
this has to do with this thread, I have no idea.

--
Phil, Squid-in-Training

Jasper said:

I can't explain it either, but
several times a tube that was slightly too long ended up with a short
folded section (3-7 cm I'd say), and it resulted in a bad 'bump' at that
spot. One possible explanation is that I may have been less than diligent
about getting the bead properly seated, and that part of it was still in
the rim well thus allowing the tyre to bulge at the opposite end. Usually
when you inflate a tyre it'll pop into alignment naturally, but maybe
somehow the doubled up section interferes with that.

I suspect that a bit of the excess tube may have gotten between the
bead of the tire and the rim, preventing it from seating properly in
that area. Having a wider and/or longer tube than appropriate
certainly makes it harder to mount the tire on the rim while making
sure that the tube is all properly stowed inside the tire.

But I've had the same experience as Jobst that once installed the tire
and tube worked fine. There was no detectable problem when riding even
with rather severe mismatches - such as a 700c tube inside one of the
20" tires on my folding bike or in the 26" mountain bike wheels of
other riders.

Pete Biggs said:

I don't see how an inner tube can deform a tyre or unseat it. A problem
with the tube may affect its durability or rolling resistance but how can
it put the tyre out of round? Does it not do whatever it has to do to
conform to the tyre?

Recently I had a very good example of how an inner tube can unseat a
tyre. I'm fairly sure that this is what happened, due to the history of
the tube and tyre. Here's what happened. I'm mad enough to run a fixed
gear "shopping bike" with 700c wheels. I have Vredestein Stila 32mm
tyres on it, which are rated to a maximum pressure of 75psi. These tyres
are a little prone to needing careful seating on the rims IME, so I was
extra careful to seat them, inflate to 20 psi and check the seating
before fully inflating them on first installation. After several months
of regular use with re-inflation to 75psi every 4 to 7 days and no
problems whatsoever, I accidentally inflated them to 95psi (my pump has
number markers every 20psi, and I had a bit of brain fade that day - I
later discovered that the little red marker I had set at 75 had slipped
around the dial by about a 20psi marker, which was how I worked out I
had over-inflated the tyre by that much). I then didn't get more than
half way along my regular two mile trip to the local supermarket before
the tyre in question managed to unseat itself from the rim. Amazingly,
the tube did not burst, and I let some air out, re-seated it and
re-inflated it to 75psi with my mini-pump and carried on without any
further problem. That was some months ago.

The tyre unseated itself over a length of about 8 inches on one side
only, which I would have to say meant that at the time it was unseated
it was out of round. The other (rear) tyre was on a different rim, but
still overinflated by the same amount. I did not have a problem with
that tyre, but it should be noted that the rear rim was somewhat
narrower than the front (hey, its a shopping bike, built for next to
nowt!). I built both wheels myself, and checked them for roundness after
the event. Both were within the 0.5mm spec I built them to, although I
have to admit I did not check rim roundness with the tyre blown off.

Anyway, my conclusion is you can unseat a tyre with an inner tube if you
overinflate it. I'm not going to stop using the tyres in question
though, because other than that incident they have been excellent.

JimP

Jim Price said:

Anyway, my conclusion is you can unseat a tyre with an inner tube if
you overinflate it.

I reckon that's caused by the air pressure being too high for the tyre &
rim (or the way the tyre is fitted) rather than anything to do with the
tube itself. In other words, the same thing will happen with any tube if
you pump it up as hard.

What I don't understand is how a fold in a tube causes any unseating,
assuming it's not trapped under a bead.

~PB

Jim Price said:

I accidentally inflated them to 95psi [20 psi over rating]...
I then didn't get more than
half way along my regular two mile trip to the local supermarket before
the tyre in question managed to unseat itself from the rim. Amazingly,
the tube did not burst, and I let some air out, re-seated it and
re-inflated it to 75psi with my mini-pump and carried on without any
further problem. That was some months ago.

The tyre unseated itself over a length of about 8 inches on one side
only, which I would have to say meant that at the time it was unseated
it was out of round.

Hmmm... more support for the theory espoused in the "time for a cookout
-- we're having crow" thread. I'm beginning to think that Peter Cole had
it right.

--
Dave
dvt at psu dot edu