Source of chainrings?

Lionel Scales said:

I have an Ofmega Vela double chainset on my road bike and want to drop the inner ring from 42 to
39. The bolt circle diameter is 130mm. I can't seem to find any reference to a suitable ring on
the web - can anyone point me in the right direction, please? Many thanks, Lionel

130 is a very common road size, used by Shimano Road chainsets. All the major mail order houses have
them. Look for 130 PCD (Pitch Circle Diameter), BCD is Bolt Centre Distance and is of course less
than PCD. Look at SJS, Settle Cycles etc, etc, etc
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Lionel Scales said:

I have an Ofmega Vela double chainset on my road bike and want to drop the inner ring from 42 to
39. The bolt circle diameter is 130mm. I can't seem to find any reference to a suitable ring on
the web - can anyone point me in the right direction, please?

Assuming 5-arm (5 bolts), www.settlecycles.co.uk/shop is the best supplier I know for suitable TA
and Stronglight rings. Look for 130mm or "Shimano".

PCD is the same thing as BCD.

~PB

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

Quoted message said:

Lionel Scales said:

I have an Ofmega Vela double chainset on my road bike and want to drop the inner ring from 42 to
39. The bolt circle diameter is 130mm. I can't seem to find any reference to a suitable ring on
the web - can anyone point me in the right direction, please? Many thanks, Lionel

130 is a very common road size, used by Shimano Road chainsets. All the major mail order houses
have them. Look for 130 PCD (Pitch Circle

Diameter),

Quoted message said:

BCD is Bolt Centre Distance and is of course less than PCD. Look at SJS, Settle Cycles etc,
etc, etc
--
The Reply & From email addresses are checked rarely. mseries.freeserve.co.ukmseries.freeserve.co.ukOpen ↗

Thanks for the quick reply, but I am confused by PCD and BCD:

What exactly does the Pitch Circle Diameter measure? (On my chainset, the five fixing bolts lie on a
circle which is exactly 130mm in diameter.)

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

Quoted message said:

Lionel Scales said:

I have an Ofmega Vela double chainset on my road bike and want to drop the inner ring from 42 to
39. The bolt circle diameter is 130mm. I can't seem to find any reference to a suitable ring on
the web - can anyone point me in the right direction, please? Many thanks, Lionel

130 is a very common road size, used by Shimano Road chainsets. All the major mail order houses
have them. Look for 130 PCD (Pitch Circle

Diameter),

Quoted message said:

BCD is Bolt Centre Distance and is of course less than PCD. Look at SJS, Settle Cycles etc,
etc, etc
--
The Reply & From email addresses are checked rarely. mseries.freeserve.co.ukmseries.freeserve.co.ukOpen ↗

Thanks for the quick reply, but I am confused by PCD and BCD:

What exactly does the Pitch Circle Diameter measure? (On my chainset, the five fixing bolts lie on a
circle which is exactly 130mm in diameter.)

Lionel Scales said:

What exactly does the Pitch Circle Diameter measure? (On my chainset, the five fixing bolts lie on
a circle which is exactly 130mm in diameter.)

The Pitch Circle is the circle on which the chainring bolt centres lie. PCD is the diameter of this
circle. Why ? Don't know

try this link chickencycles.comchainringsOpen ↗

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The Reply & From email addresses are checked rarely. mseries.freeserve.co.ukmseries.freeserve.co.ukOpen ↗

Lionel Scales said:

What exactly does the Pitch Circle Diameter measure? (On my chainset, the five fixing bolts lie on
a circle which is exactly 130mm in diameter.)

The Pitch Circle is the circle on which the chainring bolt centres lie. PCD is the diameter of this
circle. Why ? Don't know

try this link chickencycles.comchainringsOpen ↗

--
The Reply & From email addresses are checked rarely. mseries.freeserve.co.ukmseries.freeserve.co.ukOpen ↗

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

Quoted message said:

The Pitch Circle is the circle on which the chainring bolt centres lie.

PCD

Quoted message said:

is the diameter of this circle. Why ? Don't know

It was called that in BS 308, Engineering Drawing Practice, so I have always assumed it to be a
standard engineering term.

--
Guy
===

WARNING: may contain traces of irony. Contents may settle after posting.
chapmancentral.demon.co.ukchapmancentral.demon.co.ukOpen ↗

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

Quoted message said:

The Pitch Circle is the circle on which the chainring bolt centres lie.

PCD

Quoted message said:

is the diameter of this circle. Why ? Don't know

It was called that in BS 308, Engineering Drawing Practice, so I have always assumed it to be a
standard engineering term.

--
Guy
===

WARNING: may contain traces of irony. Contents may settle after posting.
chapmancentral.demon.co.ukchapmancentral.demon.co.ukOpen ↗

Just zis Guy said:

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

Quoted message said:

The Pitch Circle is the circle on which the chainring bolt centres
lie. PCD is the diameter of this circle. Why ? Don't know

It was called that in BS 308, Engineering Drawing Practice, so I have always assumed it to be a
standard engineering term.

I googled for the term and I picked up a thread from one of the groups probably rec.bicycles.tech
which implied its a British thing and Sheldon thinks we all should use BCD. Well it is a British
thing and c'est la vie. BTW BCD to me is Binary Coded Decimal.

--
The Reply & From email addresses are checked rarely. mseries.freeserve.co.ukmseries.freeserve.co.ukOpen ↗

Just zis Guy said:

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

Quoted message said:

The Pitch Circle is the circle on which the chainring bolt centres
lie. PCD is the diameter of this circle. Why ? Don't know

It was called that in BS 308, Engineering Drawing Practice, so I have always assumed it to be a
standard engineering term.

I googled for the term and I picked up a thread from one of the groups probably rec.bicycles.tech
which implied its a British thing and Sheldon thinks we all should use BCD. Well it is a British
thing and c'est la vie. BTW BCD to me is Binary Coded Decimal.

--
The Reply & From email addresses are checked rarely. mseries.freeserve.co.ukmseries.freeserve.co.ukOpen ↗

Pete Biggs said:

PCD is the same thing as BCD.

Not according to TA though which is very confusing.

Pete Biggs said:

PCD is the same thing as BCD.

Not according to TA though which is very confusing.

MSeries said:

Quoted message said:

PCD is the same thing as BCD.

Not according to TA though which is very confusing.

I'm not sure about that or what TA say. When I order TA rings described as 135mm PCD, I receive
rings with 135mm BCD.

Technically, "pitch circle diameter" is used incorrectly here but it's a term (some of) the bicycle
industry uses to mean exactly the same thing as bolt circle diameter.

~PB

MSeries said:

Quoted message said:

PCD is the same thing as BCD.

Not according to TA though which is very confusing.

I'm not sure about that or what TA say. When I order TA rings described as 135mm PCD, I receive
rings with 135mm BCD.

Technically, "pitch circle diameter" is used incorrectly here but it's a term (some of) the bicycle
industry uses to mean exactly the same thing as bolt circle diameter.

~PB