Campy 11 BCD?

[Dr Luxurious]

What's the BDC for 52/36 for this style crank?
Apparently googling skills aren't up to par

[slambers3]

Originally Posted by Dr Luxurious

What's the BDC for 52/36 for this style crank?
Apparently googling skills aren't up to par

110 but one of the bolt arms has a slightly longer tab so you can’t use a regular off the shelf ring without modification

[Mark McM]

Originally Posted by slambers3

110 but one of the bolt arms has a slightly longer tab so you can’t use a regular off the shelf ring without modification

Specifically, 4 of the chainring bolts are at a 110mm BCD, and the "hidden" bolt (which attaches the chainrings to the back of the crank arm) is at a 112mm BCD. Some people have elongated the bolt hole in standard 110mm BCD chainrings to fit onto Campagnolo cranks.

Before they adopted the 110mm/112mm BCD, Campagnolo made some non-hidden bolt compact cranks which used the standard of 5 bolts all at 110mm BCD. However, all Campagnolo 5 arm cranks with a hidden 5th bolt have used the 110mm/112mm BCD. Why did they do this? It made no functional or performance difference. It didn't save money for either Campagnolo or the cunsumer. It made no aesthetic difference (the bolt at the non-standard BCD is hidden, afterall). It wasn't better for the environment. The only possible conclusion is that they wanted to be jerks.

[Dr Luxurious]

OK, now how do I get that damn 5th bolt out

[Hindmost]

135mm

There is a little plastic tab in the bolt center. Pry/break it out.

[oldpotatoe]

Originally Posted by Mark McM

Specifically, 4 of the chainring bolts are at a 110mm BCD, and the "hidden" bolt (which attaches the chainrings to the back of the crank arm) is at a 112mm BCD. Some people have elongated the bolt hole in standard 110mm BCD chainrings to fit onto Campagnolo cranks.

Before they adopted the 110mm/112mm BCD, Campagnolo made some non-hidden bolt compact cranks which used the standard of 5 bolts all at 110mm BCD. However, all Campagnolo 5 arm cranks with a hidden 5th bolt have used the 110mm/112mm BCD. Why did they do this? It made no functional or performance difference. It didn't save money for either Campagnolo or the cunsumer. It made no aesthetic difference (the bolt at the non-standard BCD is hidden, afterall). It wasn't better for the environment. The only possible conclusion is that they wanted to be jerks.

Except for the 135mm full sized Campagnolo cranks. Like the one pictured...doh!

I guess, like shimano has been jerks for the tons of proprietary crank BCDs, on a TON of their MTB cranks and first in the industry 4 arm cranks. Even some shimano chainrings that didn't even fit onto shimano cranks...yup, jerks.

[Mark McM]

Originally Posted by oldpotatoe

I guess, like shimano has been jerks for the tons of proprietary crank BCDs, on a TON of their MTB cranks and first in the industry 4 arm cranks. Even some shimano chainrings that didn't even fit onto shimano cranks...yup, jerks.

.
The difference here is that the each Shimano BCD had a functional difference, whereas the Campagnolo 110mm/112mm BCD has no functional difference at all. Zero. Zilch. Nada. Maybe some might feel that the functional difference in Shimano's BCDs wasn't enough to warrant creating new BCDs, but there's no justification at all for the 110mm/112mm BCD.

And speaking of comparing the proliferation of BCDs between Shimano and Campagnolo, let's take a look at Sheldon Brown's BCD crib sheet. This lists the BCDs used by different manufacturers over the years. Campagnolo has had little involvement in MTB cranks, but over the last 30 years or so Campagnolo has used 9 different BCDs for their road double cranks (145mm, 135mm, 123mm, 121mm, 112mm 4 arm, 110mm/112mm 5 arm, 110mm, 96mm, 88mm).while Shimano has used only 3 different BCDs on double road cranks (130mm, 110mm 5 arm, 110mm 4 arm). But getting back to MTB for a moment, triple MTB cranks need more BCDs than double cranks, yet Shimano has used only 10 BCDs for their MTB triple cranks, which is only 1 more than Campagnolo has used for their road double cranks.

Out of al the BCDs on the Sheldon Brown cribsheet, there is only on that uses 2 different BCDs for the same chainring - the Campagnolo 110mm/112mm. This was done for no useful purpose whatsoever - it only exist to be jerks.

[Hindmost]

"...it only exist to be jerks."

Well, it does ensure paired rings are correctly indexed.