vinuneuro

I am looking at picking up a Specialized Diverge Expert. This model is supposed to come with the 50/34 FSA SL-K Light crankset. However at the store and pictures of owners' bikes online I see both 110mm and 130mm cranksets on otherwise identical bikes. On the FSA site and chainreaction the crankset is only shown with the 110mm version so it looks like they switched away from 130mm. Aesthetically I like the 130mm more. From a performance perspective (stiffness) does one have an advantage over the other?

130mm:



110mm:

CliffordK

The big question should be what size of inner ring do you want?

110 BCD: 33T or 34T
130 BCD: 38T or 39T

50T outer is also common with the "compact" cranksets, while 52T or 53T for the 130bcd cranksets, although a variety of rings should be possible. However, modern chainrings are often designed to be run in matched pairs.

Are your "standard" cranks 4 bolt, while the compacts are 5 bolt? There is a much greater selection of rings available with 5 bolt cranksets, although that may well change in a couple of years.

Doge

We have the same with Specialized both 110 and 130 - same arms, different spider. I'm sure this is somewhat mfg dependent but if you have the bolts nearer to the OD of the ring everything else being the same (and it rarely is) it will be stiffer and more direct. So if you are happy with the ring choices go 130. There are more options 5 hole than 4 hole.

Doge

Add - it is likely those 4 bolt rings are hollow and multi part like the Dura-Ace. That may make for great performance but you could see a de-lamination.

Shadowjaxs

I use the FSA SL-K Light 52T 110bcd, I don't think there's any advantage. I was told if you put a 53 chain ring or higher on the 110bcb. The chain ring it would flex.

no1mad 

Moved from Road Cycling.

fietsbob

A 3D outer chainring can be stiffer than one that is Flat ..


Cranksets can be changed by the bike's Owner , to other parts ..

Like: White Ind VBC ROAD CRANKS ? White Industries

Variable bolt circle uses slots rather than Holes to let you build doubles with a wide range of combinations.

vinuneuro

Thanks for the feedback. Found the 4 bolt 110mm SL-K Light in the 2015 Fairwheel crank test. Looks to be a decent performer. No idea how the previous 130mm would have been other than it looks prettier. The gearing on Diverge is spec'd 50/34 so that's fixed. I suppose which version I get is a lottery but the longer I wait the more likely I am to get the 110mm version.

A number of other cranks in this test are 4 bolt including Campy, Dura Ace and Sram so maybe that's direction the industry has moved in. It does look like the 4 bolt design gives the crank arm more material against the rest of the assembly so perhaps it is stiffer.

Road Bike Crank Test - Fairwheel Bikes Blog

Andrew R Stewart 

Back in the day a 110 bolt circle crank would brand one a s a tourist, not a racer. But what do you know, these days racers are going pretty fast (actually faster then back in the day) on their sponsor supplied 110's.

CliffordK said it well. What are your gearing needs, now and in the future? Andy.

Andrew R Stewart 

Don't believe this for a minute EVERYTHING ELSE BEING EQUAL. 5 points of support beat out 4 if they are of the same design. What's really going on is that large changes in design (4 supports of greater material or dimensional use) can get small changes in measured capacity. Then the marketing department takes over and 5 is old school and those who still use them are mere tourists. Andy.

fietsbob

They may have studied the power output at TDC and BDC of the crank and finding it so small it eliminated an arm

to shave off those easy to sell few grams.

woodcraft

If you get 50/34, then you get 110 BCD.

34 ring will not fit on 130 BCD.

vinuneuro

The 2015 Diverge had the same 50/34 gearing and was using the 130mm crankset.

HillRider

No, it didn't. Either the published crank specs were wrong or the chainring count was mistaken. There is absolutely no way to fit a 34T chainring on a 130 cmm bolt circle.

woodcraft

We are talking about (110 vs 130) bolt circle diameter- BCD, measured in mm.

Your pics both show 110 BCD. One w/ 53/39, one with 50/34

That's the whole reason for compact cranks- nothing smaller than 38 tooth will fit the standard crank.

Since the Diverge is designed for off road, etc., it wouldn't make much sense to put the larger chain rings on it anyway.

vinuneuro

You are both right. I mistakenly equated 4 bolt= 110mm and 5 bolt= 130mm. Looks like the previous version of the 50/34 SL-K Light was 5 bolt 110mm and now it is 4 bolt 110mm. The specs are visible on the previous version crankset:

https://www.gambacicli.com/media/cata...o-386-2013.jpg

oldbobcat

And even 38t rings are sketchy on 130 mm cranks. After minimal chain and cog wear, chains skate over the flange that separates the rings. Which is why Shimano, Campagnolo, SRAM, FSA, and Praxis don't make them.

woodcraft

I only said that to be technically correct.

I understand that 38T rings are made, but I've never seen one.

Andrew R Stewart 

No. Andy

wesmamyke

They make 4 bolt 110bcd cranks and chainrings now? Now you're just trying to confuse people on purpose...

vinuneuro

Or I'm just confusing myself. The second picture in the first post shows 110mm BCD written on it and looks like it's 4 bolt. What am I missing..

fietsbob

Recognition things change .. 4 arm is the new trend