Road Bike Racing - 39 versus 42 tooth chainring

Does anyone know when 39 tooth chainrings replaced 42 tooth chainrings as the standard small ring? Is this simply just a fashion thing or do the 39 rings offer a better ratio? I have run a number of combinations on Sheldon Browns gear ratio calculator and cannot decide what the advantages of a smaller ring are except mabe a shorter chain.

The advantages are that a 39T is easier than a 42T for climbing and also lets you spin a bit faster.
Several years ago some of the Euro pros switched to 39T; In a couple of very nountainous stages in Spain there were even a some big name racers using a triple! Yep, it is easier on the knees and it beats walking up a very steep incline as some of the other racers had to
Of course the cycling industry likes to change things now and then so they can sell you something 'new.'

I admit that I'm still rather new to road bikes which is to say that I haven't been around road bikes long enough to know of the trends like I'm familiar with from the MTB world. During the time when the 42T was prevalent as the inner ring, what was the outer ring size? Was it a 53T like today? Or was it a 52T like in today's triples? Or was it something else?

I *think* it happened back in the '80s, when Shimano came out with 8 speed rear ders, about the same time 53 became the number of choice for the big ring.

Weight. With the 39, you can put a smaller (lighter) cluster on the back.
To replace triples, FSA& Campy offer compact drive up front for even greater weight savings while giving you the climbing gears needed.

In reality, if I were not racing I would start with a compact drive crankset to give far more usable gears. How many recreational riders actually use a 53x11 or 53x12 on a regular basis? They would get far more use out of a 50x12 or 28x23.

With the compact crank and a 12-15 cluster, you would have a ultralightweight system that would give you more usable range for the majority of your riding, imo.

I know a 39T replaced a 42T on MY bike last summer :D

I like the compact chainwheel idea, maybe a50T big ring with a 12-23 cassette. I turn a high cadence, and have often wondered who would use a 53T with an 11 unless you are going over the side of a mountain . Would that not be a good time to save your legs?

There's been a few times where I rode a 53x11 in a haul-ass paceline on a flat section of road.

I'm planning on changing my 39 ring for a 42 because i don't like the feeling of over spinning while cycling on the flat. Also i prefer grinding up hills. Just feel the 39 is a little too small for my liking.

I thought I would jump in on this subject. Most component manufacturers switched from a 52 /42 front chainwheel to a 53/39 when 7spd became widely available. I recenlty switched my system from a 53/39 to a FSA 50 /34 with a D/A 10 spd 11/23 cassette and I have had no problems with group rides/crits/road races staying with or racing at the front on all types of courses.

Thanks
Buddy B

Basically the 39 will place less stress on your knees, and that is a good thing, unless you are on the younger side of life and then why would you care.

I have use 52-42s and 53-39s. The 52-42 is good if your terrain is mostly flat and you ride fast. The transistion from 10T diff w/ the 52-42 is smooth, so I only need to click once or twice on the rear. The 53-39 however is harder to use, since you will have to click twice or more since the resistance change is more sudden.

But, I like the 53-39 better, because I ride hilly routes and I can put 12-23T cassettes and still climb steep hills, likewise my shifting(rear) is smoother w/ my tight cassette. On 53-42, I need to put a 12-27 so I can get low enough gears for climbs.

I think Shimano was the prime mover it making 52/39 front c'rings popular. I think you have to stretch it a bit to find a valid logical reason for it. Like, how come they never put an 18t on a road cassette? To be fair, I think one of the reasons they were able to do it was that they improved the performance of their deraileurs to the point where the 12t jump from the i/s to the o/s ring was not a problem. With the older systems you needed a little finesse to handle that kind of jump. Selling new bikes with the 53/39 combo was a nice way to show off the 'superiority' of their stuff. Have you noticed that they use an STI system very similar to Campy's ONLY on their cheapest groupos? (in terms of the way the levers work) Subtle psychology there I think. With their market dominance (particularly in the 90s) 53/39t became the 'standard'. In the 'old' days some of us used a 'half-step ratios' set-up. Based on the rule-of-thumb that 3t in the front is worth 1t on the back you could use say 52/49t on the front. (gave a change as smooootthhh as butter) with a 14-16-18-21-24t at the rear. Do the calculations and you'll find a beautifully evenly spaced set of ratios beginning with a low of 53in to a high of 100in. It did require frequent changes at the front from i/s to o/s and back, but with the close spacing they were smooth, easy and quick and you could become very adept at using just your right hand for both front and rear levers. Honest! But that was a long time ago. With 10 (count 'em) cogs on the back you almost don't need but one chain-ring now.

Have you noticed that they use an STI system very similar to Campy's ONLY on their cheapest groupos? (in terms of the way the levers work) Subtle psychology there I think.

Hmmm... maybe so. Because they have people thinking that Sora and Ergo are similar which is absolutely not true. Sora levers have the thumbshifter positioned way forward on the hoods and it's impossible (for everyone that I've ever met) to reach them from in the drops. You pretty much have to ride the hoods in order to shift. The Ergo shifters are much further back and can be reached by most people from multiple positions including the drops. Sora still retains the main lever as the brake lever which pivots to the side. Some would view this as an advantage while others might disagree stating that it introduces the eventuality of accidently shifting while braking and vice versa. The Ergo's brake levers do not pivot to the side. There is a small side-pivoting lever behind the brake lever which looks like the second levers on higher-level Shimano shifters but actually serves the purpose of the main lever. This lever on Ergos also can move back and forth to provide for on-the-fly reach-adjustment. While Sora shifters look similar to Ergos, they are quite different in both operation and capability.

I have an old schwinn le tour I just picked up from a freind that has 39 52 and I know he hasn't upgraded since freewheels and manual spring clamp water bottle cages were in. (scrub and wax, shiny as new)