110 vs 130 BCD
 

Can someone help me out? I would like to know what the benefits / disadvantages are for the 110 and 130 chainrings.

I ride a recumbent and I suppose one of the reasons for the 110BCD original equipment is to allow for a very small granny ring. I comes with a 24T ring. Seems that the smallest I can get in the 130BCD is a 30T. Is that the limits of the rationale? or is there something more to be considered.

Is this a double? Typically the BCD for the granny ring is 74 BCD for either standard road (130 BCD) or compact (110 BCD) rings. For instance, my Sugino triple is 110/74 BCD.

Ah yes, I failed to be complete in my 'technical description'.
No, I have a road triple. And the granny gear is a 74BCD; you are correct.
But the question remains; is there a reason for choosing a 110 vs a 130?

110 only goes up to about 50t IIRC
130 goes higher

Your middle ring can be smaller on the 110 BCD crank.

http://sheldonbrown.com/harris/chainrings/110.html
http://sheldonbrown.com/harris/chainrings/130.html

Plenty of 52/53t 110s out there, but none are Biopace, alas:(
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On the largest sized rings, there would be less "ring flex" with the 130's vs 110's.

Not true. 110bcd rings can gotten up to 73 teeth off the shelf:
http://hostelshoppe.com/cgi-bin/read...ory=1155076891
Less expensive Vuelta rings go up to 60 teeth in either bolt pattern:
http://hostelshoppe.com/cgi-bin/read...ory=1016049820
http://hostelshoppe.com/cgi-bin/read...sory=990633343

IMO, no particular advantage to either setup.

Smallest middle ring on a 130 triple is 38.

Only laterally. Forces in the plane of the rings wouldn't flex a 110bcd ring any more than a 130mm one. You've got some problems on your bike if you're loading the rings laterally.

Heard of cross-chaining? It is possible to fold lightweight chainrings.

74mm BCD chainrings seems to go down as low as 24 teeth: http://www.universalcycles.com/shopp...&category=3161

Standard road triples (usually 74/130 BCD) generally come with a 30 tooth inner ring whereas touring/hybrid triples (usually 74/110 BCD) will come with a 26 or 28 tooth inner chainring. There is nothing keeping you from using a 24 tooth inner ring on a road triple other than possible sloppy shifting into the middle ring given that the smallest you could fit on the 130mm BCD is 38 teeth. In order to stay within your front deraillers shifting capacity, you'd then also need to drop the size of the big ring down.

The 130 rings, middle and outer, take a ring range from 38 to 65 tooth. The 110 rings, middle and outer, take a ring range from 33 to 54 tooth. The small 74 BCD rings, on both standard road and road touring triples, take a ring range from 24 to 36 tooth. The 110/74 BCD was common on many early mountain bikes, but is now generally referred to as standard road touring BCD. Mountain bikes went to even smaller granny ring BCD, with a 22 tooth small ring being the most common.

For the 110/74 road touring cranksets, like Sugino, a 26-36-46 chainring setup is common.

And cross-chaining isn't a problem?

Cross-chaining loads the rings laterally and most people seem to do it to some extent.

Never seen it happen. Not once.

Folded a 53 tooth chainring on a tandem in half when I shifted into too low a gear with a short chain. Others have posted about folding rings. It happens. Not often, but it happens.

While you can use a 24 inner ring on a 130/74 crank, the longer arms of the 130 spider can allow the chain to get trapped between the arm and the inner ring on occasion. It's not common but it can happen. Getting the chain out from behind the inner ring is difficult. On a 110/74, the spider is shorter and there's no room for the chain to rest in between the inner ring and the arms.

I have a 48/34/22 mountain bike crank with an 11-34 on my bikes. Plenty of high end and low end.

Thanks for chiming in with the real world experience about a 24 tooth ring on a 130/74 crank. Out of curiosity, have you tried a 26 on the same setup and how did it work?

It's been a while, but I think it came with a 28 or 26. That was never a problem and the issue with the 24 was a rarity. Just be aware that it can happen and it's a bugger to get the chain back out. I have changed the crank since then because I wanted a lower middle gear.