Hello all,

I'm currently trying to figure out and better identify what I need and what is being said when I see, "chainring 144bcd". I've seen other figures too. Can someone either explain what the numbers mean or have a link you can provide?

BTW, I have a 50/34 crankset and I want to get something a little lower in gearing. I have a 700c bike and would like something leaning a bit more towards climbing. I don't even know if I can put anything smaller than a 34 tooth ring on. Having a 30t or a 32t would be what I'm more interested in. Even the large one can be down to 48t.

Any help on this is very greatly appreciated and most welcomed.

Thank you,

bcd=bolt circle diameter. The rest of your question depends on your crankset. A typical bcd is 130mm.

Your bicycle uses a compact crank that has a 110 mm bolt circle on a 5 bolt spider, getting a lower gearing may require a change in your rear cassette and possibly to your rear derailleur as a wider range in the rear may warrant a rear derailleur with more capacity.

The compact double limits you to a small chain ring of 33, a cassette change would be more economical.

BCD refers to bolt circle diameter, the bcd on the chainring needs to match the bcd on the crank spider.

I'm sorry but I'm not really following what "bolt circle diameter" is......... Oh OK I found out what it is, BCD

I'm pretty much limited in changing the cassette to something more lower gears. It's a 12-28 and I don't want to start with messing with MB parts. What I have now is pretty close to what I want. If I did want to move in any direction, it would be to getting lower gears. If I had to change crank, cassette, derailleur and who knows what else, I'd just live with what I got. I just thought I could change the rings, or at least think about it.

"specifically that's The older Campag road and also track cranks & chainrings since then..

Better link for BCD: https://sheldonbrown.com/gloss_bo-z.html#bcd

When you run out of low gears, consider standing up to climb.

An even better link for the BCD: https://sheldonbrown.com/cribsheet-bcd.html

As a rule of thumb: shimano/fsa/others are 130mm standard, 110compact. Campagnolo is 135mm, Track/fixie is 144mm.
(unless you work with obsolete stronglite, sachs, scapin, whatever 60-90's oddballs)

Note that high end cranks are still oddballs, like having 5arm 130but those 5arms are not equally spaced so a standard 130 chainring will not fit on all bolts.

I don't think this is quite right as I don't know of any 130 mm BCD crank without evenly spaced bolts. You may be thinking of Campy's top tier compact cranks with their modified 110 mm BCD. They have 4 of the 5 bolts on a standard 110 mm circle and the 5th one offset a couple of mm.