Pendergast

When looking through specifications I've noticed some bikes(Specialized Diverge, Sequoia) that have 110BCD cranksets with a 32t small ring. I haven't seen them and am wondering how they're managing to squeeze a chain ring that small on there.

Pendergast

Guess I haven't been keeping up with the current stuff. FSA lists a 110BCD crankset with even a 30t small ring.

FSA Omega MegaExo - Full Speed Ahead

Bostic

Praxis is offering a 48/32 Micro Compact as well. I was wondering the same thing. If a 34 or certain 33 tooth chain rings are the minimum, how is a 32 or 30 fitting? Is the BCD similar to the Sugino Compact plus with 110/74 BCD with the rings mounted on the inside?

redlude97

Its 4 hole, you can move the teeth a hair closer to the bolts compared to 5 bolt configurations

Bostic

Thanks, that makes more sense. The Praxis website doesn't show the Alba or Zayante with a four bolt as of now. I'll probably still get a Sugino as it offers more options with the extra 74mm BCD for the inner ring.

CliffordK

Why would that make a difference, or does it rely on the teeth being a multiple of 4 (32), and thus aligning with the arms?

joejack951

I believe FSA's 30T inner rings are relying on a 90mm BCD as used on this crankset: FSA SL-k light Adventure Modular BB386EVO - FULL SPEED AHEAD

Pulling the teeth closer to 4 bolts by relying on a tooth count being a multiple of 4 doesn't work for 30T.

Gotta love the 'simplicity' of double cranks and now the proliferation of new BCDs and crank styles to overcome the inherent limitations of only having two chainrings, while still not addressing the lack of range. Triples FTW, as always

CliffordK

So, not really 110 BCD?

Bostic

I'll probably get one of the 46/30 options when they are available for my Volagi Liscio. A bucket list item I really want to do is the Mauna Kea climb from beach to summit. I did Haleakala back in 2012 with a triple and low of 30x27. Mauna Kea is 3000 more feet though and has the horribly steep dirt section as well.

joejack951

I can see how you can make a 4 bolt 110mm BCD 32T ring, but not a 30T.

KonaRider125

Wick works makes a 41/33 chainring set available for most common crank options including 110 Bcd.

https://wickwerks.com/products/cyclo...41-33-110-bcd/

baobao

For a road bike, why would anyone even consider 46/30? What do the professionals in Tour de France use in mountain stages?

redlude97

what does what a pro that puts down twice the power a normal cyclist does have to do with it?

baobao

redlude97, i'm sorry you took offense in my questions, and mistook them to be cynical;nevertheless, my questions are not answered.

Bostic

Depending on your location and how much climbing you do, a 48/32 or 46/30 can be more efficient than a 50/34 with regards to terrain and how many rollers there are and staying in the big ring. If you are fast and strong than it's all a moot point, but I'm sure most of the people taking the time to read this thread are more interested in the advantages of lower gearing.

AlexCyclistRoch

Your post defies mathematics, as well as logic. 110BCD means "bolt circle diameter", the key word here being "circle". Whether that circle is defined by 3,4,5,6 or however many points, it is still a circle of the diameter mentioned. In fact, if anything, a 5 bolt would have a slight advantage over a 4 bolt, due to the slightly smaller amount of metal needed around each of the bolt holes to handle the torque. You could probably tweak just a bit more with a 6 bolt pattern, in fact...

PepeM

Because that gearing works for them? You can still go over 30mph+ at a normal cadence with a 46 ring, so it's not like you're losing much at the top end and it might allow you to stay on the big ring for most of your riding. Meanwhile, the 30 ring will allow you to climb steep grades without having to grind it out at uncomfortable cadences.

As for your other question, 39/53 most of the time.

CliffordK

For Campy 144 cranks, one has to barely file down the spider to get the chain to sit right on 41T chainrings. I filed it down at an angle at the bolt surface.

I wonder if some 110 cranks also need a slight modification to get the 33T rings to work. And if 32's are available, they would also likely need the spider to be carved up a bit.

Oh, it looks like Sheldon Brown also sells the 33T rings as singles.

110 mm BCD Mountain and Compact Road Bicycle Chainrings (Chainwheels) from Harris Cyclery

ThermionicScott 

33T was always possible for 110 BCD cranks, it's just not common.

For the smallest chainring sizes, it sounds like FSA has been developing rings where the bolts go *through* some of the teeth: TPE16: FSA gets Modular with new cranks for MTB, Gravel, and Road, plus steel Comet 1x chainrings - Bikerumor

I'm skeptical of 30T on a 110 BCD, though. I wonder if they use a smaller BCD for the 46/30 combo, and neglected to mention that on their page.

joejack951

Check the link I posted to their adventure crankset. If offers a 30T inner ring and uses a 90mm BCD. Either FSA neglected to mention the smaller BCD or they don't really offer those rings on that crank. It is geometrically impossible to do a 110mm BCD 30T ring. Even aligning the bolt holes with the teeth (using 5 bolts) doesn't create enough space to make it work, unless they are using tiny bolts.

Cyclist0108

Protracted 16-18% grade, and more-so if it is on loose gravel (try standing up on such a hill), loaded touring bike, orthopedic injuries and limitations, etc. Basically it is an alternate to a triple.

In the case of a 46/30T, you only lose one gear at the top vs. a 50/34T. (50/12 = 46/11 ± 0.01).


cf: https://www.bikeforums.net/fifty-plus...road-bike.html

B. Carfree

There's always this option: https://www.compasscycle.com/shop/co...-double-crank/

Get as small as you need.

Drew Eckhardt 

Lots. With mere mortals unlikely to tolerate low cadences better than professional riders we need gears half the size at 50% less power.

This ignores the fact that pros are too big to compete at 7% body fat, while 74% of American adult men are over-weight and 36% obese.

A 5'9" guy like Alberto Contador who races at 137 pounds is considered overweight at 169, and obese at 203.

Riding a 15 pound bike at the UCI minimum weight with 4 pounds of water/shoes/gear makes combined weights of 156 pounds when racing-fit, 188 over-weight, and 222 pounds obese; calling for 21% and 42% increases in gearing to maintain the same cadence.

Climbing a moderate 8% mountain like l'Alpe d'Huez where pros use 39x23, at half the power 5'9" guys who look like POW survivors should be riding gears like 30x36, the barely over-weight 26x36, and obese 22x36.

Those of us with 10% grades should use 20% smaller granny rings when going all-out.

Obviously things like all day endurance rides in the mountains and loaded touring call for even lower gears.

Drew Eckhardt 

Eddy Merckx dominated the classics with a 52x13 big gear which falls between 46x11 and 46x12.

joejack951

But but but... you can't buy a road bike with those gears so that can't be right