Multi-Question about 130BCD vs 135BCD

[puma]

I just wanted to make sure that there was no difference in chain rings of either the 130mm BCD and the 135mm BCD, except of course the bolt pattern/spacing? Basically, I'm assuming that the spacing between teeth on both Shimano and Campy chain rings is the same, thus the diameter of any given chainring with the same amount of teeth is the same (a Shimano 53-teeth chain ring has the same diameter as that of a Campy 53-teeth chainring). If this is so, then why do some third-party manufacturers of cranksets, such as FSA, offer the same exact cransets with differing BCD chain rings and spiders (FSA's standard is 130BCD, but you can get it in 135BCD, though it's relatively rare)? I assume that compatibilty issues are not the case (an FSA 130BCD chain ring will work fine on a Campy 10 groupo), so is it just incase some one might want to put their Campy chain rings on their FSA cranks and could only do such a thing with the 135BCD spider? And why did FSA choose to make 130BCD chainrings their standard anyway, do more of their customers seem to have Shimano users?

I made a number of assumptions, so if any of them are wrong, don't hesitate to throw it in my face. Thanks, this will clear up a lot of questions that haunt me in my dreams.

 

[puma]

Bump

 

[boudreaux]

I just wanted to make sure that there was no difference in chain rings of either the 130mm BCD and the 135mm BCD, except of course the bolt pattern/spacing? Basically, I'm assuming that the spacing between teeth on both Shimano and Campy chain rings is the same, thus the diameter of any given chainring with the same amount of teeth is the same (a Shimano 53-teeth chain ring has the same diameter as that of a Campy 53-teeth chainring). If this is so, then why do some third-party manufacturers of cranksets, such as FSA, offer the same exact cransets with differing BCD chain rings and spiders (FSA's standard is 130BCD, but you can get it in 135BCD, though it's relatively rare)? I assume that compatibilty issues are not the case (an FSA 130BCD chain ring will work fine on a Campy 10 groupo), so is it just incase some one might want to put their Campy chain rings on their FSA cranks and could only do such a thing with the 135BCD spider? And why did FSA choose to make 130BCD chainrings their standard anyway, do more of their customers seem to have Shimano users?

I made a number of assumptions, so if any of them are wrong, don't hesitate to throw it in my face. Thanks, this will clear up a lot of questions that haunt me in my dreams.

Campy record and now chours cranks use a hidden 5th bolt, resulting a different roll of pin location on the big ring. And, yeah, tooth spacing on all rings is the same, be it 144BCd or 56BCD.

 

[psjackson]

The differing bolt diameter patterns have arisen because of the need to use smaller and smaller chanrings over the years. Pre 1967 the Campag standard was 151BCD and this only facilitated a minimum 43 tooth chainring which was sufficient for climbers in those days. Probably as a result of the drive to introduce steeper and longer climbs at higher speeds in major events, cyclists found they needed to use smaller rings than 43 teeth. Campag then introduced 144BCD which allowed them to use a 41 tooth ring. This satisfied the elite for a number of years but again the drive to fit smaller chainrings arose. Campag currently uses 135BCD to allow a smaller ring (39 teeth rings I think), and then Shimano issued road standard of 130BCD. With the introduction of triple chainrings and compact design we have seen recently the introduction of 110BCD and even 94BCD, used by mountain bikers. Miche have adapted the Campag new standard of 135BCD and 144BCD seems to be the de-facto track standard. I guess you could equate this to Beta vs VHS and Apple vs IBM. Where will the market go from here, who knows? The uptake of compact in Europe might indicate that eventually 110BCD may become predominant, but that is speculation only.

 

[mark higgins]

Basically some of it comes down to marketing, some of it (with compacts)to inner ring size. When I was young all you could get was a 42 inner (Campag). Now most small sizes are in so 34/36 is de rigeur. How did we climb before....