How does one measure wheel diameters?

Alan Holmes said:

My son had the wheels stolen off his bike and I'm trying to find
replacements, if I measure the diam of the brake ring will this help?

Alan

It might, measure from the bottom of the brake block to the middle of the
front fork dropout in millimeters. Multiply by 2, and compare to common
wheel sizes (406, 451, 507, 559, 571, 622 or 630)

Warning! It might be that your son's bike is not a common size. The above
are just the commonest. For a full list see

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

But probably the easiest way is to try some of his friends' bike wheels in
his frame and read the size off the tyre.

Hope this helps

Tom
--
Return address is dead. Real address is at
http://www.happy-penguin.info/address.jpg

Alan Holmes said:

My son had the wheels stolen off his bike and I'm trying to find
replacements, if I measure the diam of the brake ring will this help?

When you say brake ring do you mean the position of the pads on the
rim?

If yes, then measuring that will give you a rough idea of the ERTRO
size of the wheel.

622 mm is 700C
559 mm is 26" mountain bike.

--
Phil Cook looking north over the park to the "Westminster Gasworks"

In article <[email hidden]>

Alan Holmes said:

My son had the wheels stolen off his bike and I'm trying to find
replacements, if I measure the diam of the brake ring will this help?

Brake ring? I guess you mean the braking surface on the side of the
rim. Measuring the distance from the middle of the axle to the middle
of the brake block in millimetres and doubling it will give a fair
approximation of the actual wheel diameter.
The actual tyre diameter is measured where the tyre fits against the
inside of the rim, but the nominal size will be different from that so
you need to check a tyre size chart like the one at the bottom of this
page:
http://www.users.globalnet.co.uk/~pattle/nacc/arc0307.htm
to find the nominal size. The ETRTO number in the first column is the
width and diameter in millimetres in the format ww-ddd. There is
usually a choice of tyre widths to fit a particular rim, so the width
isn't particularly critical, although a very narrow tyre won't work on a
very wide rim and vice-versa.
What sort of bike is it?

"Rob Morley" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

In article <[email hidden]>

Alan Holmes said:

My son had the wheels stolen off his bike and I'm trying to find
replacements, if I measure the diam of the brake ring will this help?

Brake ring? I guess you mean the braking surface on the side of the
rim.

That's right, couldn't think of the right term.

Measuring the distance from the middle of the axle to the middle

Quoted message said:

of the brake block in millimetres and doubling it will give a fair
approximation of the actual wheel diameter.

Can't I do it in inches?

Quoted message said:

The actual tyre diameter is measured where the tyre fits against the
inside of the rim, but the nominal size will be different from that so
you need to check a tyre size chart like the one at the bottom of this
page:
http://www.users.globalnet.co.uk/~pattle/nacc/arc0307.htm
to find the nominal size. The ETRTO number in the first column is the
width and diameter in millimetres in the format ww-ddd. There is
usually a choice of tyre widths to fit a particular rim, so the width
isn't particularly critical, although a very narrow tyre won't work on a
very wide rim and vice-versa.

Quoted message said:

What sort of bike is it?

An Elwick Sovereign folding bike, had a sturmey archer gear.

Alan

Quoted message said:

Alan Holmes said the following on 20/12/2006 16:44:

Quoted message said:

Can't I do it in inches?

No necessarily. A measurement given in inches can have a different
meaning to the apparently equivalent dimension in mm. Again, see the
Sheldon Brown website. Strange things, tyre sizes!

--
Paul Boyd
http://www.paul-boyd.co.uk/

Paul Boyd said:

Alan Holmes said the following on 20/12/2006 16:44:

Quoted message said:

Can't I do it in inches?

Yes but you will need to convert to mm so measure in mm.

Quoted message said:

Not necessarily. A measurement given in inches can have a different
meaning to the apparently equivalent dimension in mm. Again, see the
Sheldon Brown website. Strange things, tyre sizes!

Very. But getting a wheel diameter from a brake isn't going to be an
exact science.

The numbers you are looking at from Tom's post (406, 451, 507, 559,
571, 622 or 630) are the bead seat diameters for the common wheel
sizes. Given that the bead seat of the rim is pretty close to where
the brakes are you should end up with what size wheel you need when
you compare with the wheel sizes.

20 x 1.5-20 x 2.125 406 mm Most BMX, folders, some recumbents
20 x 1 3/8 451 mm Juvenile lightweights
24 x 1.5-24 x 2.125 507 mm Juvenile mountain bikes
26 x 1.00 through 2.3 559 mm Most Mountain bikes
650 C 571 mm Road bikes for smaller riders
700C 622 mm Modern road bikes
27 x anything 630 mm Older road bikes.
--
Phil Cook looking north over the park to the "Westminster Gasworks"

In article <[email hidden]>

Alan Holmes said:

"Rob Morley" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

In article <[email hidden]>

Alan Holmes said:

My son had the wheels stolen off his bike and I'm trying to find
replacements, if I measure the diam of the brake ring will this help?

Brake ring? I guess you mean the braking surface on the side of the
rim.

That's right, couldn't think of the right term.

Measuring the distance from the middle of the axle to the middle

Quoted message said:

of the brake block in millimetres and doubling it will give a fair
approximation of the actual wheel diameter.

Can't I do it in inches?

You can measure it in cubits if you want but you'll have to convert it
to millimetres because that's how the ISO/ETRTO size is given in tyre
size tables.

Quoted message said:

Quoted message said:

The actual tyre diameter is measured where the tyre fits against the
inside of the rim, but the nominal size will be different from that so
you need to check a tyre size chart like the one at the bottom of this
page:
http://www.users.globalnet.co.uk/~pattle/nacc/arc0307.htm
to find the nominal size. The ETRTO number in the first column is the
width and diameter in millimetres in the format ww-ddd. There is
usually a choice of tyre widths to fit a particular rim, so the width
isn't particularly critical, although a very narrow tyre won't work on a
very wide rim and vice-versa.

Quoted message said:

What sort of bike is it?

An Elwick Sovereign folding bike, had a sturmey archer gear.

If it's from the mid 80s or later it's probably 20 x 1.75, but ISTR
Elswick did some 24" wheel bikes as well, and an older 20" wheel could
be 20 x 1 3/8".

"Rob Morley" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

In article <[email hidden]>

Alan Holmes said:

"Rob Morley" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

In article <[email hidden]>
Alan Holmes <[email hidden]> wrote:
>
> My son had the wheels stolen off his bike and I'm trying to find
> replacements, if I measure the diam of the brake ring will this help?
>
Brake ring? I guess you mean the braking surface on the side of the
rim.

That's right, couldn't think of the right term.

Measuring the distance from the middle of the axle to the middle

Quoted message said:

of the brake block in millimetres and doubling it will give a fair
approximation of the actual wheel diameter.

Can't I do it in inches?

You can measure it in cubits if you want but you'll have to convert it
to millimetres because that's how the ISO/ETRTO size is given in tyre
size tables.

Quoted message said:

Quoted message said:

The actual tyre diameter is measured where the tyre fits against the
inside of the rim, but the nominal size will be different from that so
you need to check a tyre size chart like the one at the bottom of this
page:
http://www.users.globalnet.co.uk/~pattle/nacc/arc0307.htm
to find the nominal size. The ETRTO number in the first column is the
width and diameter in millimetres in the format ww-ddd. There is
usually a choice of tyre widths to fit a particular rim, so the width
isn't particularly critical, although a very narrow tyre won't work on
a
very wide rim and vice-versa.

Quoted message said:

What sort of bike is it?

An Elwick Sovereign folding bike, had a sturmey archer gear.

If it's from the mid 80s or later it's probably 20 x 1.75, but ISTR
Elswick did some 24" wheel bikes as well, and an older 20" wheel could
be 20 x 1 3/8".

Thanks, when the weather warms up I'll go into the garage and check the
size.

Alan