Shimano 105 (old) chainrings

[Teamfixed]

Hi all,
I am in the process of putting back together my Alf Webb 531 road bike. I have an old (90's) 105 chainset on it. The BCD measurement is 125mm (I think its an A type). Its got 52/42/30 currently and I want to change it to a 48/38/30 if poss. I am having trouble finding rings to fit and virtually no reference to 125 BCD. Any help appreciated.
Tim

 

[fossyant]

Are you sure it's not 130mm BCD for the outer two rings.

 

[fossyant]

My Dura Ace (1990) and 600 (1986) chainsets are 130mm - OK both double but thought triples used the same outer ! Never heard of 125mm

 

[fossyant]

Just in case you are struggling. Sun race also do a retro double and triple.

https://www.sjscycles.co.uk/chainsets/1725-stronglight-impact-triple-chainset-silver-524232t/

 

[Sharky]

Good write up on BCD's in here
https://www.wolftoothcomponents.com/pages/how-to-measure-bolt-circle-diameter-bcd

 

[IanSmithCSE]

is it this one?

http://velobase.com/ViewComponent.aspx?ID=dbce1783-c844-45db-a791-042a17e04874

 

[Teamfixed]

Ok guys, I think I have been measuring from the wrong points. In the photo the calipers are on 130mm. I thought BCD was from bolt center to bolt center.

130mm

76.4mm

Using the Wolf guide, measuring between adjacent bolts 76.4 is indeed a BCM of 130.
Ian, its similar but mine is Hollowtech.
Now I need to search for some!
Many thanks for your help
Tim

 

[fossyant]

Stronglight do both Dural and Zircal varieties of 130 BCD chain rings. The dural are a little less 'finished' but are fine (I have these on my shimano 600) and the posher Zircal on my Dura Ace

 

[Hugh Manatee]

I have a 38 small ring on my winter bike. It has 130 BCD Ultegra and 38 was the smallest that would fit. Stronglight I think.

 

[Teamfixed]

That's great, I've found stronglight 38 and 48's. Will report back when all done.
Doing the same with a Centaur (currently 39/53) chainset which is also 130mm... I assume Campag are the same measurement method.

 

[Poacher]

That's great, I've found stronglight 38 and 48's. Will report back when all done.
Doing the same with a Centaur (currently 39/53) chainset which is also 130mm... I assume Campag are the same measurement method.

Campag more likely to be 135mm.
Check carefully to avoid disappointment!

 

[Teamfixed]

Campag more likely to be 135mm.
Check carefully to avoid disappointment!

Yes you are correct, just had a look. I had actually already ordered a 130bcd 48 tooth thinking it would fit the campag but I now now it will go on the 105! which is better really as the campag bike gearing can stay as it is...it only ever has to carry a spare tube!

 

[Poacher]

Yes you are correct, just had a look. I had actually already ordered a 130bcd 48 tooth thinking it would fit the campag but I now now it will go on the 105! which is better really as the campag bike gearing can stay as it is...it only ever has to carry a spare tube!

I was going to edit my post to include a link to https://sheldonbrown.com/cribsheet-bcd.html, but couldn't prise Mrs Poacher away from the laptop!
This contains many more obscure sizes compared to Wolf Tooth's, which only seems to include the sizes they sell (surprise!), e.g. nothing about my favourite old obsolete 86mm, but unforgivably, no reference to 74mm, which is almost certainly the size of your current 30 tooth chainring.