Old Bike Tire sizing - Noob.

I'm on the road again, after having fractured my foot pedaling
a few years back. Sand/dirt roads, lots of hills, 60 km rides etc. The
fracture never healed completely ...

Using a bike I bought in 1975. I'm having difficulties trying
to figure what the numbers on the tires actually mean
I always bought Pirelli tires made here in Brazil.
These were marked
28 x 1 1/2 x 1 5/8
700 x 42B

But they stopped making them.

I ordered some from the local bike shop, and they fit
perfectly, but seem a little bit narrower. They are some generic make
from Indonesia. Markings:

28 x 1 1/2
40-635

Is there any logic in the numbering at all ?
I thought the ISO numbering would solve this, but all the
tables I download seem to give different numbers for the same tires.
TIA

PS Visited Wiki, Sheldon's and downloaded a table he
http://www.cyclable.com/attachment.php?id_attachment=50

--
Don't be evil - Google 2004
We have a new policy - Google 2012

On 14/10/14 10:22, Shadow wrote:
I'm on the road again, after having fractured my foot pedaling
a few years back. Sand/dirt roads, lots of hills, 60 km rides etc. The
fracture never healed completely ...

Using a bike I bought in 1975. I'm having difficulties trying
to figure what the numbers on the tires actually mean
I always bought Pirelli tires made here in Brazil.
These were marked
28 x 1 1/2 x 1 5/8
700 x 42B

1 1/2 inches is 38.1mm, approximate tyre/rim width. I believe the 1 5/8
indicates the height of the tread, i.e. it is a little higher than it is
wide.

The 42 will be approximate width in mm.

All tyre widths are approximate to some extent, because the actual
inflated width depends on the rim width.

The B gives a clue from Sheldon...

28 x 1 1/2 635 mm English, Dutch, Chinese, Indian Rod-brake roadsters
(Also marked F10, F25, 700 B)

ISO 635mm rim bead seat diameter. This is the critical bit.


But they stopped making them.

I ordered some from the local bike shop, and they fit
perfectly, but seem a little bit narrower. They are some generic make
from Indonesia. Markings:

28 x 1 1/2
40-635

Being marked 28 x 1 1/2 means the diameter and width should be pretty
close, but there is variability between manufacturers.

The 40-635 clearly agrees with the info from Sheldon Brown, and he had
this to say;

http://sheldonbrown.com/tire-sizing.html

" The ISO system uses two numbers; the first is the width of the tire or
rim in millimeters (The actual tire width will vary a bit depending on
the width of the rim. The rim width is the inner width measured between
the flanges as shown in the diagram.)

The second ISO number is the critical one, it is the diameter of the
bead seat of the rim, in mm ("B.S.D."). Generally, if this number
matches, the tire involved will fit onto the rim; if it doesn't match,
the tire won't fit. "


Is there any logic in the numbering at all ?

Seems like it.

I thought the ISO numbering would solve this, but all the
tables I download seem to give different numbers for the same tires.
TIA

PS Visited Wiki, Sheldon's and downloaded a table he
http://www.cyclable.com/attachment.php?id_attachment=50




--
JS

On Tue, 14 Oct 2014 11:12:22 +1100, James
wrote:

On 14/10/14 10:22, Shadow wrote:
I'm on the road again, after having fractured my foot pedaling
a few years back. Sand/dirt roads, lots of hills, 60 km rides etc. The
fracture never healed completely ...

Using a bike I bought in 1975. I'm having difficulties trying
to figure what the numbers on the tires actually mean
I always bought Pirelli tires made here in Brazil.
These were marked
28 x 1 1/2 x 1 5/8
700 x 42B

1 1/2 inches is 38.1mm, approximate tyre/rim width. I believe the 1 5/8
indicates the height of the tread, i.e. it is a little higher than it is
wide.

Hum, according to the Wiki page, 1 5/8" would be the width,
not the height.


http://en.wikipedia.org/wiki/File:Ty...data_01-en.png

The height would be 1 1/2"

The 42 will be approximate width in mm.

All tyre widths are approximate to some extent, because the actual
inflated width depends on the rim width.

The B gives a clue from Sheldon...

28 x 1 1/2 635 mm English, Dutch, Chinese, Indian Rod-brake roadsters
(Also marked F10, F25, 700 B)

ISO 635mm rim bead seat diameter. This is the critical bit.


But they stopped making them.

I ordered some from the local bike shop, and they fit
perfectly, but seem a little bit narrower. They are some generic make
from Indonesia. Markings:

28 x 1 1/2
40-635

Being marked 28 x 1 1/2 means the diameter and width should be pretty
close, but there is variability between manufacturers.

The 40-635 clearly agrees with the info from Sheldon Brown, and he had
this to say;

http://sheldonbrown.com/tire-sizing.html

" The ISO system uses two numbers; the first is the width of the tire or
rim in millimeters (The actual tire width will vary a bit depending on
the width of the rim. The rim width is the inner width measured between
the flanges as shown in the diagram.)

The second ISO number is the critical one, it is the diameter of the
bead seat of the rim, in mm ("B.S.D."). Generally, if this number
matches, the tire involved will fit onto the rim; if it doesn't match,
the tire won't fit. "


Is there any logic in the numbering at all ?

Seems like it.

I thought the ISO numbering would solve this, but all the
tables I download seem to give different numbers for the same tires.
TIA

PS Visited Wiki, Sheldon's and downloaded a table he
http://www.cyclable.com/attachment.php?id_attachment=50

OK, I think I got it.

http://sheldonbrown.com/rim-sizing.html

Both tires fit because they have the same "bead seat of the
rim" diameter. And also the same "height" (1 1/2"). But the generic
ones are 1/4'' narrower than the Pirelli ones (1 3/8" vs 1 5/8"), so
probably not so good on the dirt roads I ride on. But they only cost
50 dollars for 4 of them, so I suppose I can't complain. Done just
over 1000 km, no sign of wear yet.
But the ISO system is lacking. A very "high" tire would have
the same measurements as a "low" one, and might not fit the frame.
TY
--
Don't be evil - Google 2004
We have a new policy - Google 2012

On Monday, October 13, 2014 4:22:47 PM UTC-7, Shadow wrote:
I'm on the road again, after having fractured my foot pedaling

a few years back. Sand/dirt roads, lots of hills, 60 km rides etc. The

fracture never healed completely ...



Using a bike I bought in 1975. I'm having difficulties trying

to figure what the numbers on the tires actually mean

I always bought Pirelli tires made here in Brazil.

These were marked

28 x 1 1/2 x 1 5/8

700 x 42B



But they stopped making them.



I ordered some from the local bike shop, and they fit

perfectly, but seem a little bit narrower. They are some generic make

from Indonesia. Markings:



28 x 1 1/2

40-635



Is there any logic in the numbering at all ?

I thought the ISO numbering would solve this, but all the

tables I download seem to give different numbers for the same tires.

TIA



PS Visited Wiki, Sheldon's and downloaded a table he

http://www.cyclable.com/attachment.php?id_attachment=50


There is only one ISO number in all of those designations -- the 40-635. All he others are traditional/French or fractional numbers. The 700 42B would (if I'm not mistaken) equate to a 635 ISO diameter (700B) and 42mm width.. So, yes, it looks like you got a slightly narrower tire - a 40mm width. Who knows what happened to the 42-635 if there ever was one.

-- Jay Beattie.



--

On Tue, 14 Oct 2014 11:12:22 +1100, James
wrote:

On 14/10/14 10:22, Shadow wrote:
I'm on the road again, after having fractured my foot pedaling
a few years back. Sand/dirt roads, lots of hills, 60 km rides etc. The
fracture never healed completely ...

Using a bike I bought in 1975. I'm having difficulties trying
to figure what the numbers on the tires actually mean
I always bought Pirelli tires made here in Brazil.
These were marked
28 x 1 1/2 x 1 5/8
700 x 42B

1 1/2 inches is 38.1mm, approximate tyre/rim width. I believe the 1 5/8
indicates the height of the tread, i.e. it is a little higher than it is
wide.

The 42 will be approximate width in mm.

All tyre widths are approximate to some extent, because the actual
inflated width depends on the rim width.

The B gives a clue from Sheldon...

28 x 1 1/2 635 mm English, Dutch, Chinese, Indian Rod-brake roadsters
(Also marked F10, F25, 700 B)

ISO 635mm rim bead seat diameter. This is the critical bit.


But they stopped making them.

I ordered some from the local bike shop, and they fit
perfectly, but seem a little bit narrower. They are some generic make
from Indonesia. Markings:

28 x 1 1/2
40-635

Being marked 28 x 1 1/2 means the diameter and width should be pretty
close, but there is variability between manufacturers.

The 40-635 clearly agrees with the info from Sheldon Brown, and he had
this to say;

http://sheldonbrown.com/tire-sizing.html

" The ISO system uses two numbers; the first is the width of the tire or
rim in millimeters (The actual tire width will vary a bit depending on
the width of the rim. The rim width is the inner width measured between
the flanges as shown in the diagram.)

The second ISO number is the critical one, it is the diameter of the
bead seat of the rim, in mm ("B.S.D."). Generally, if this number
matches, the tire involved will fit onto the rim; if it doesn't match,
the tire won't fit. "


Is there any logic in the numbering at all ?

Seems like it.

I thought the ISO numbering would solve this, but all the
tables I download seem to give different numbers for the same tires.
TIA

PS Visited Wiki, Sheldon's and downloaded a table he
http://www.cyclable.com/attachment.php?id_attachment=50


Except for a few anomalies like 26 x 1-3/4 and 26 x 1.35 tires that
aren't the same size :-)
--
Cheers,

John B.

On 10/13/2014 6:22 PM, Shadow wrote:
I'm on the road again, after having fractured my foot pedaling
a few years back. Sand/dirt roads, lots of hills, 60 km rides etc. The
fracture never healed completely ...

Using a bike I bought in 1975. I'm having difficulties trying
to figure what the numbers on the tires actually mean
I always bought Pirelli tires made here in Brazil.
These were marked
28 x 1 1/2 x 1 5/8
700 x 42B

But they stopped making them.

I ordered some from the local bike shop, and they fit
perfectly, but seem a little bit narrower. They are some generic make
from Indonesia. Markings:

28 x 1 1/2
40-635

Is there any logic in the numbering at all ?
I thought the ISO numbering would solve this, but all the
tables I download seem to give different numbers for the same tires.
TIA

PS Visited Wiki, Sheldon's and downloaded a table he
http://www.cyclable.com/attachment.php?id_attachment=50


635mm is the definitive number, as you found. It's the
actual bead set diameter and the second-oldest extant tire
size for bicycles. Width selection may vary a bit as in any
tire.

28-inch is vague and covers many sizes including yours,
which is bigger than a 29-inch (!)

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On Tuesday, October 14, 2014 12:22:47 AM UTC+1, Shadow wrote:
I'm on the road again, after having fractured my foot pedaling

a few years back. Sand/dirt roads, lots of hills, 60 km rides etc. The

fracture never healed completely ...



Using a bike I bought in 1975. I'm having difficulties trying

to figure what the numbers on the tires actually mean

I always bought Pirelli tires made here in Brazil.

These were marked

28 x 1 1/2 x 1 5/8

700 x 42B



But they stopped making them.



I ordered some from the local bike shop, and they fit

perfectly, but seem a little bit narrower. They are some generic make

from Indonesia. Markings:



28 x 1 1/2

40-635



Is there any logic in the numbering at all ?

I thought the ISO numbering would solve this, but all the

tables I download seem to give different numbers for the same tires.

TIA



PS Visited Wiki, Sheldon's and downloaded a table he

http://www.cyclable.com/attachment.php?id_attachment=50



--

Don't be evil - Google 2004

We have a new policy - Google 2012

As Muzi says, the operative number is the 635. But you may be able to go wider than 40 or even 42mm. The rolling diameter of your present tyre is somewhere near (635 + (2*40))mm. You can measure it exactly either across the centre of the hub or by rolling it along the floor and working back from the circumference via pi. But it is usually adequate to measure from the tyre to the mudguard or inside top of the fork. That's how much height you have to play with. Subtract some space, say 10-12mm, divide the remainder by two, and this is how much bigger your next tyre can be. Check whether there is space horizontally on each side a bit higher than where your present tyres most closely approaches the fork.

The reason for fitting the fattest tyres possible is that the fatter the tyre, the lower the pressure you can run it at without damaging it, and the higher your comfort on the bike.

In any event, try running your present tyres at the lowest permitted inflation pressure and see if it doesn't improve your comfort.

Andre Jute

On Tue, 14 Oct 2014 08:19:10 -0700 (PDT), Andre Jute
wrote:

I always bought Pirelli tires made here in Brazil.
These were marked
28 x 1 1/2 x 1 5/8
700 x 42B
But they stopped making them.
I ordered some from the local bike shop, and they fit
perfectly, but seem a little bit narrower. They are some generic make
from Indonesia. Markings:
28 x 1 1/2
40-635

As Muzi says, the operative number is the 635. But you may be able to go wider than 40 or even 42mm. The rolling diameter of your present tyre is somewhere near (635 + (2*40))mm. You can measure it exactly either across the centre of the hub or by rolling it along the floor and working back from the circumference via pi. But it is usually adequate to measure from the tyre to the mudguard or inside top of the fork. That's how much height you have to play with. Subtract some space, say 10-12mm, divide the remainder by two, and this is how much bigger your next tyre can be. Check whether there is space horizontally on each side a bit higher than where your present tyres most closely approaches the fork.

You forget I live in Brazil. I spent months looking for tires,
until I found a small shop that ordered them for me. They probably
"fell off the back of a ship" on it's way to America, it was a
cash-only no-receipt deal.

The reason for fitting the fattest tyres possible is that the fatter the tyre, the lower the pressure you can run it at without damaging it, and the higher your comfort on the bike.

Yes, I know. I prefer even the original marginally wider
Pirelli tires. But beggars can't be choosers. It would cost a fortune
to import them.

In any event, try running your present tyres at the lowest permitted inflation pressure and see if it doesn't improve your comfort.

I'll have to grow a callus on my bum. Or use a pillow.
Whatever.

TY for your thoughts
[]'s
--
Don't be evil - Google 2004
We have a new policy - Google 2012

On Tue, 14 Oct 2014 18:29:16 +0700, John B. Slocomb
wrote:

On Tue, 14 Oct 2014 11:12:22 +1100, James
wrote:

On 14/10/14 10:22, Shadow wrote:
I'm on the road again, after having fractured my foot pedaling
a few years back. Sand/dirt roads, lots of hills, 60 km rides etc. The
fracture never healed completely ...

Using a bike I bought in 1975. I'm having difficulties trying
to figure what the numbers on the tires actually mean
I always bought Pirelli tires made here in Brazil.
These were marked
28 x 1 1/2 x 1 5/8
700 x 42B

1 1/2 inches is 38.1mm, approximate tyre/rim width. I believe the 1 5/8
indicates the height of the tread, i.e. it is a little higher than it is
wide.

The 42 will be approximate width in mm.

All tyre widths are approximate to some extent, because the actual
inflated width depends on the rim width.

The B gives a clue from Sheldon...

28 x 1 1/2 635 mm English, Dutch, Chinese, Indian Rod-brake roadsters
(Also marked F10, F25, 700 B)

ISO 635mm rim bead seat diameter. This is the critical bit.


But they stopped making them.

I ordered some from the local bike shop, and they fit
perfectly, but seem a little bit narrower. They are some generic make
from Indonesia. Markings:

28 x 1 1/2
40-635

Being marked 28 x 1 1/2 means the diameter and width should be pretty
close, but there is variability between manufacturers.

The 40-635 clearly agrees with the info from Sheldon Brown, and he had
this to say;

http://sheldonbrown.com/tire-sizing.html

" The ISO system uses two numbers; the first is the width of the tire or
rim in millimeters (The actual tire width will vary a bit depending on
the width of the rim. The rim width is the inner width measured between
the flanges as shown in the diagram.)

The second ISO number is the critical one, it is the diameter of the
bead seat of the rim, in mm ("B.S.D."). Generally, if this number
matches, the tire involved will fit onto the rim; if it doesn't match,
the tire won't fit. "


Is there any logic in the numbering at all ?

Seems like it.

I thought the ISO numbering would solve this, but all the
tables I download seem to give different numbers for the same tires.
TIA

PS Visited Wiki, Sheldon's and downloaded a table he
http://www.cyclable.com/attachment.php?id_attachment=50


Except for a few anomalies like 26 x 1-3/4 and 26 x 1.35 tires that
aren't the same size :-)
2 totally different sizing systems
Decimal and fractional
The current decimal sized system measures the rim diameter and tire
cross-section - ie, 2.25X26
The fractional size measures the outer tire diameter and the
cross-section of the tire - ie. 1 3/8 X28

Here in Canada the fractional sizes were very common, while the
americand used the decimal sise, with some non-standards like the
Schwinn s3?.

When mountain bikes arrived is when we started seeing the decimal
sizes become predominent.

Phil W Lee writes:

considered Tue, 14 Oct 2014 20:12:22 -0400 the
perfect time to write:

On Tue, 14 Oct 2014 18:29:16 +0700, John B. Slocomb
wrote:

On Tue, 14 Oct 2014 11:12:22 +1100, James
wrote:

On 14/10/14 10:22, Shadow wrote:
I'm on the road again, after having fractured my foot pedaling
a few years back. Sand/dirt roads, lots of hills, 60 km rides etc. The
fracture never healed completely ...

Using a bike I bought in 1975. I'm having difficulties trying
to figure what the numbers on the tires actually mean
I always bought Pirelli tires made here in Brazil.
These were marked
28 x 1 1/2 x 1 5/8
700 x 42B

1 1/2 inches is 38.1mm, approximate tyre/rim width. I believe the 1 5/8
indicates the height of the tread, i.e. it is a little higher than it is
wide.

The 42 will be approximate width in mm.

All tyre widths are approximate to some extent, because the actual
inflated width depends on the rim width.

The B gives a clue from Sheldon...

28 x 1 1/2 635 mm English, Dutch, Chinese, Indian Rod-brake roadsters
(Also marked F10, F25, 700 B)

ISO 635mm rim bead seat diameter. This is the critical bit.


But they stopped making them.

I ordered some from the local bike shop, and they fit
perfectly, but seem a little bit narrower. They are some generic make
from Indonesia. Markings:

28 x 1 1/2
40-635

Being marked 28 x 1 1/2 means the diameter and width should be pretty
close, but there is variability between manufacturers.

The 40-635 clearly agrees with the info from Sheldon Brown, and he had
this to say;

http://sheldonbrown.com/tire-sizing.html

" The ISO system uses two numbers; the first is the width of the tire or
rim in millimeters (The actual tire width will vary a bit depending on
the width of the rim. The rim width is the inner width measured between
the flanges as shown in the diagram.)

The second ISO number is the critical one, it is the diameter of the
bead seat of the rim, in mm ("B.S.D."). Generally, if this number
matches, the tire involved will fit onto the rim; if it doesn't match,
the tire won't fit. "


Is there any logic in the numbering at all ?

Seems like it.

I thought the ISO numbering would solve this, but all the
tables I download seem to give different numbers for the same tires.
TIA

PS Visited Wiki, Sheldon's and downloaded a table he
http://www.cyclable.com/attachment.php?id_attachment=50


Except for a few anomalies like 26 x 1-3/4 and 26 x 1.35 tires that
aren't the same size :-)
2 totally different sizing systems
Decimal and fractional
The current decimal sized system measures the rim diameter and tire
cross-section - ie, 2.25X26

No it doesn't. 26" is nowhere near to being the same as 559mm (which
is the bead seat diameter of a decimal 26" tyre).

26 inch * 25.4 mm/inch = 660.4 mm.

I guess if you measure rims with a micrometer that's "nowhere near".