Friday, September 20, 2013

Low gearing on a road bike - Part 2/3: "Choosing a crankset"

In the previous part, I discussed several possible options of lowering the gear ratio on a road bike with STI shifters - a task that seems to be non-trivial, since nearly all road component groups are designed around large-chainring cranksets, such as 53/39T or 50/34T.
I showed that even a compact crankset with a 110mm BCD (bolt circle diameter) and 50/34T chainrings is just not enough. That's because the smallest chainring that can be installed on such cranks is a 34T and there are no road cassettes that will have sprockets larger than 30T or maybe 32T (SRAM). This means that by replacing the cassette and keeping the cranks, we can't achieve a 1:1 gear ratio.
But what to do if we want even lower gears?
Replace the crankset - is the answer. Finding the right one, is the challenge. There are some classic offerings from Herse, Stronglight, TA and Velo Orange but all of these look just too retro for my taste, use square taper bottom brackets and have no ramps and pins to ease shifting with indexed STI shifters. Plus, all these cranks can be quite expensive - somewhere between $385 to $450, without bottom brackets (Velo Orange option is actually cheaper but it's also the most old-school looking).
Rene Herse cranks. (Source: Compass Bicycles Ltd)

TA Specialites Carmina cranks. (Source: Google Images)

Velo Orange Grand Cru 50.4 cranks. (Source: Velo Orange)

White Industries came up with their VBC cranks, which also use a square bottom bracket, lack good ramps and pins and use proprietary chainrings. They look a bit more modern though, but I have no idea how smooth shifting would be. At $350 (for a 46/30T setup without a bottom bracket) they are not the cheapest either.
White Industries VBC cranks. (Source: Google Images)
In my search, I considered several options:

1. Budget option
Use Shimano Tiagra FC-4603 cranks. These come with 50/39/30T rings and cost about $120, but I also found them for only $87 on ebay. Bottom bracket, such as Tiagra 4600, costs about $25. Set of chainring bolts: $8-$15. I would need these, since I would have to remove the 50T entirely and replace the 39T ring with a 46T ring from my current cranks.
TOTAL: $120
Pros and cons? It is cheap but also heavy - Tiagra crankset weighs over 1000g. The biggest problem is that I would be limited to 1:1 ratio with my 12-30T cassette. If I want something lower, I would have to spend much more and replace either chainrings, cassette, rear derailleur or all of these. Is it worth it? Only if you're on a tight budget.
Shimano Tiagra FC-4603 crankset. (Source: Google Images)
2. Still quite inexpensive but lighter
This is essentially the same approach as option 1, but with the Shimano 105 FC-5703 cranks for $217. These cranks are hollow and the weight of the crankset is only about 850g with 50/39/30T rings.
TOTAL: $260
Pros and cons? Yes, it is lighter, looks much better, but it is still only 1:1 ratio. To achieve lower gearing I would either have to replace the 30T chainring with a smaller one or replace the cassette (with e.g. 12-32T) and a rear derailleur. This may quickly all add up to $430. Is it worth it? Depends. It is probably the cheapest option with a good weight-to-performance ratio: relatively lightweight setup, still not too expensive and 1:1 gearing can be easily achieved. But, using triple cranks with 2 chainrings only means that chainline and q-factor suffer a little but other than that, it does look attractive.
Shimano 105 FC-5603 crankset. (Source: Google Images)
3. The best choice out there?
However, within the $300-$400 range, I think I can do better. Sugino OX601D crankset is the smaller cousin of the $500 OX801D cranks. The finish of OX601D is a bit dull and the price is lower, but except that, there seems to be not much difference between these two. These cranks can be ordered with many different chainrings down to 44/30T and they come with 110/74mm BCDs (That's what Sugino calls Compact Plus). This means that theoretically, even smaller rings down to 24T can be installed. Not to mention that the largest ring is aggressively ramped and pinned to help shifting and the bottom bracket is included in price and features outboard cups!
Sugino OX601D crankset. (Source: Google Images)
Since OX601D can be purchased for $330, is it worth paying more for the OX801D? Their reported weights are quite different but after lots of research, I found out that while 920g of OX601D includes the bottom bracket, the 790g of OX801D does not. In fact, I read that the bottom bracket for both cranks weighs about 105g, which would mean that there is only 30g difference in weight between them. Apparently, the more expensive crank has alloy chainring bolts, high polish finish and... a higher price. The rest is about the same as its smaller cousin.

But how about the gear ratios? By purchasing the cranks with 44/30T rings (Unfortunately, there seems to be no way to order them with 44/28T rings.), I am still limited to 1:1 ratio, but future expandability of such system looks much more promising. I found out that I very rarely use the smallest 12T sprocket in my cassette, therefore, reducing the largest chainring to 44T makes sense. By doing this and eventually replacing the small one with a 28T ring, I can still maintain 16T difference between the rings - a maximum allowed for standard road derailleurs. Of course, I am not limited here. With different derailleurs, I can lower the gearing even further to 44/28T +12/32T or maybe 44/26T + 12/32T. This is the beauty of cranks such as OX601D and this is why in comparison, compact road cranks combined with a huge 36T cassette sprocket is a dead-end solution (You can't install a smaller ring than a 34T on compact cranks and there are no road cassettes with sprockets larger than 36T).
TOTAL: $346 (with an extra 28T ring)

Pros and cons? Not cheap, but highly expandable and flexible system. Possible to achieve a truly low gearing with integrated, indexed shifters.


  1. Sorry for commenting on such an old post, but here are some related articles about the effects of pins and ramps that were written around the time of your original post.

    Jan Heine on chainring choice or shifting ramps

    Jan Heine on trouble with STI triples

  2. I read these articles before. Jan's theory is correct but then, there is theory and practice. Yes, you can't expect ramps and pins on Sugino's 44T chainring expect to work well with all possible combinations with all smaller chainrings. But I have tested it in 44/30T and 44/28T setups and both work very well and shift quickly. The only limitation in using chainrings smaller than 30T is that you can't safely use small chainring in combination with smallest cassette sprockets such as 30T+12T or 30T+13T because chain starts rubbing on the inside of the larger 44T chainring. But those are not the gears you would normally use anyway.

    The beauty in Sugino's crankset is in 110/74mm BCDs. It's definitely possible to build any chainring setup you would like, whether you start with factory-supplied 44T or 46T chainrings or choose your own (without ramps and pins).

    Jan's comment about issues with STI triples doesn't really apply here. I'm not using a STI triple crankset. But Jan is correct on suggesting "ultra-compact double" instead :)