Cycling Forum: Triple ring to a compact?

I struggled with this question this summer when I purchased a new bike.  It really depends on the terrain you ride in and how good a climber you are.  I started paying attention to exactally what gear I was in and how did it releate to a compact.  For me it was ok to go to the compact.  I'm very happy with it.  However, if I lived in a mountains I would probably need the triple.

I don't know what your biggest cog is, but let's assume it's a 27 because that's the biggest cog you can get in Ultegra.  The small ring on your triple is probably a 30 (although your could go as low as a 24).  The small ring on the compact will be a 34.  With these assumptions, your low gear with the triple is about 30 inches and with the compact it's 34 inches.  That's not all that much.  The compact might work for you.

 Remember that the top gear on the compact will be lower than the triple because the big ring is a 50 instead of a 52 or 53.  If the small cog is a 12, your top gear would go from about 119 inches to 112.

One of the things that I love about cycling is every bike is a work in progress.  There's always something to change, limited only by budget.

Paul

I don't like Shimano STI front indexing myself because of problems like the one you are having.  Whether it would be cost effective to convert to something else is debatable, but you might want to at least consider Shimano bar-end shifters.  The front shifter is friction, which is exactly what a person needs in front.  The rear indexes perfectly.  I have a touring bike set up with these and like them a lot.

 Generally, I guess I prefer Shimano to Campagnolo, but Ergopower front shifting is clearly better in this area.

 Paul

CTS: Compact Cranks: The Real Story  Thursday, October 05, 2006

- by: Adam Mills, M.S.Ed., Carmichael Training Systems: Senior Coach
Years ago, as mountain bikes gained popularity, some road riders began envying the three-chainring cranks on the offroad bikes. “Triples” were soon available for road bikes, but they came at a price: they were heavy and required different front and rear derailleurs, a different bottom bracket, and a new shifter. Now there’s a new option for road riders, the compact crank. Is it just another way to get you to spend more cash at the bike shop, or are these cranks worth their weight in gold? Well, let’s go through the “W’s” and find out.
What are they?

At first glance, compact cranks look just like a normal crank set. They come in normal crank arm lengths (170, 172.5, 175 mm) and they are mounted on standard bottom brackets. However, upon closer examination you’ll see some slight, but crucial, differences. Most important, compacts have smaller chainrings. A traditional crank set will typically sports a 53x39 tooth setup. Your standard compacts run a 50x34, rings that are too small to fit on a traditional crank. Beyond providing you with a different range of gearing options, the smaller rings and bolt pattern make the compact cranks lighter than traditional cranks.

The wonder of the compact crank is that they can be installed on your normal bottom bracket, and you don’t have to change your shifter or rear derailleur. Depending on the gearing you use, you may need to replace your front derailleur, but of all the parts on a bicycle, it’s fortunately one of the less expensive ones. If you decide to make the switch, visit your local shop so you get the right equipment and professional installation.
Why use them?

The next question is, “Why on earth would I ever need these things?” That’s an excellent question and I’ll discuss the practical applications for the compact cranks later in this article. For now, let us focus on why compact cranks make a difference. In an era of science and biomechanics, we understand a lot more about the advantages of conserving energy so you have something in the tank for race-deciding efforts, sprinting for “city limits” signs, or just riding up that next hill hard. Pedaling economy would be an obvious place to make gains.

Studies have shown that while optimal cadence is highly individual, staying in your optimal cadence range (say, 90-95 rpm) as much as possible saves energy. The compact crank helps a rider stay within this range easier by decreasing the difference in gear size between each cog on the cassette. The end result is that you can spend more time within your optimal cadence range and stay fresher longer.
When to use them?

This is a cause of concern to many riders, and rightly so. Some people inaccurately view compact cranks as an inconspicuous way for weaker riders to use smaller gears. Of course, the growing use of compact cranks in the professional peloton should dispel that notion. Compacts do not have a “bail out” gear (a super-easy gear for spinning up hills), but simply provide a way to get the gear you want, more often. Climbing is probably the best application for compact cranks. Here, being able to keep your cadence in your optimal range will have a magnified effect on your fatigue level and should help you stay fresh and strong.
It’s important to realize that although compact cranks have smaller chainrings, they don’t put you at a disadvantage when it comes to going fast downhill or on flat ground. Some riders have the idea that you’re more likely to spin out a compact crank and that you won’t be able to make the high speed efforts needed in many group ride and race situations. However, being that most of us are mere mortals and unable to ride along at a 30+ mph pace on flat roads, even with a tailwind, I present this chart…
700c wheel
at 90 rpm  53-39 Rings
12-25 Cogs  50-34 Rings
11-23 Cogs
Highest Gear  31.3 MPH  32.3 MPH
Lowest Gear  11.1 MPH  10.5 MPH

I’ve picked the 12-25 for the “traditional” crank set from what racers and my local bike shop have been buying the most of recently. It seems that riders have been using the extra gear afforded from riding a 10-speed drivetrain to simply add a 25 to a 12-23 cassette. The reason for this is simple. If you rarely spin out a 53x12, why would you need an 11 cog for everyday riding. However, when training, that 23 can sometimes get awfully big, in which case a 25 looks very tempting. Many “traditionalists” will tell you’ll constantly be spun out with a 50 in the front because, “it just ain’t enough gear.” PART 2 FOLLOWS;

Thanks, I am printing up the post to read and research.  I have to bring my bike to the LBS for a tuning and I will ask about the compact. 

 For the past 2 months I have been working on my cadence and I shoot at the 95 to 100 rpm range, this is were when I am on hills that the front derailers lack of smoothness effects me.  The index shift is great when I reach the crest and shift up, it is so smooth and effortless.  This has improved my riding more than the lighter bike.  I believe also my riding has improved beyond the need for that triple ring as my confidence in my abilities has increased.

 Thanks again.

I switched at the end of last year to a compact setup. I built a new Jamis Zenith Pro and went with a 50-36 up front and a SRAM 11-26 in the rear. I previously had the standard triple setup on my Specialized Roubaix. I did get into racing Cat 5 this year at the age of 44.  I am located in Mass and we have plenty of hills. The only times I could use a 34 up front would be climbing some of the local mountain roads.  Overall I am very happy with the setup as I have used it for road races and criteriums. I feel the compact setup gives me a nice range of gearing while losing the triple and the weight that comes with it.

When I was bike shopping last year, I thought I wanted a conventional.  It had been a long time since I rode (my old Miyata 912 from the late 80's had a 42/52 front and a 13-21 7-speed rear freewheel (note I said 'freewheel' and not 'cassette')).  I figured a 39/53 would work for me.  Well, the bike I ended up getting (Cannondale Six13 R5000) had a compact on it (36/50) w/ a 12-25 10-spd.  It worked well, and I was glad that I went w/ the compact.  I ended up swapping out the 12-25 for a 12-23 10-spd and have found that, coupled w/ the 36-50 front rings, work very well for me.  I try to keep my cadence in the 85-90 range, and having what amounts to an 8-gear straight block (w/ 2 extra climbing gears) really helps.  I just found that 17-19 jump (w/o the 18 in there) was too much of a gap.  My current gearing works out to be almost a perfect cross-over pattern.  Also, I don't think I would have been happy w/ a 34-50 front setup.