crank_addict

Mostly a 52t. Its not about the descent but rather how cog ratios stack, whether 5 to 8 useable speeds and when the times having tail / skew winds with 12t >>>>> yeehaw

canklecat

My main concern is finding the right combination of gear steps, shifting quality and low drivetrain friction resistance. Other than that, gearing is gearing. As long as the 60"-80" range I'm in most of the time is in the middle cogs to avoid crosschaining, that's good enough for me.

Supposedly there are fewer friction losses with larger diameter chainrings, cogs and pulley wheels, but I'm not sure I'd notice any slight benefit. And older rear derailleurs limit us to 10 or 11 tooth pulleys. The biggest difference I've found in reducing drivetrain resistance came from replacing the original bushing bearings on the pulley wheels with smoother running sealed bearing pulleys.

And avoiding cross chaining -- I can hear a bit more chain noise as soon as I'm in the two largest and smallest cogs in either chainring. Subjectively it feels less draggy when I'm in the 70" or 80" gear that runs quietest -- usually the middle three of seven cogs.

50/39 with a 13-25 SunRace 7-speed freewheel on the Ironman until recently. Decided I needed a little more help on longer rides with some climbs and/or headwinds, so I just swapped to 50/38 and 13-28 SunRace freewheel. That covers all of our climbs, even with headwinds. We don't have any long continuous climbs so there's enough recovery time on flat and downhill stretches.

The tricky bit was finding gear steps and shifting quality that suited me. The original 52/42 with 13-24 Suntour steps were okay, but shifting was a kludge. Then I tried various combos of those freewheels with 52/42, 52/39 and 52/38, and 50/39 and 50/38. Even if the steps were okay the shifting was still balky. SunRace freewheels shift crisply and run quieter, and the 50/39 or 50/38 cover everything but a few steep downhills with tailwind assist. I'm spun out at 130 rpm and around 40 mph, but that's good enough.

The '93 Trek 5900 has 52/42 Biopace and 14-28 Shimano 7-speed freewheel. Good enough for that bike since it's much lighter than the Ironman. Same top end limitation -- I'm spun out on a few downhills with tailwinds -- but I'm not really trying for KOMs on downhills with those bikes right now. Overall rideability is more important.

The early '90s Univega Via Carisma has the original 30/40/50 triple. It's fairly heavy, around 30 lbs, and with loaded panniers and up to 50 lbs of stuff the original 30T chainring and 28T cog weren't quite enough. So now it has an 11-32 8-speed cassette. Good enough even when my legs are dead. It's an upright ride so wind resistance is the limitation on downhills with the 50T chainring and 11T small cog.

Somewhere around here I have a 58T chainring Amazon mistakenly sent me when I ordered a 50T. I kept both since they were heavily discounted open package sales, costing around $10 or less apiece. I'd kinda like to borrow a friend's single speed and try it with a 21T or so cog just to check the theory that bigger is better in terms of drivetrain friction resistance.

ThermionicScott 

Good point about cross-chaining, @canklecat. I have a pair of 52/42 BioPace chainrings in my collection that are heavily worn on the outer side of the teeth, but fairly clean in the inner side. That tells me the previous owner(s) spent a lot of time cross-chaining to the bigger cogs, and weren't able to use their smaller cogs very much of the time. They probably had a tight freewheel/cassette with too-small cogs at the top end, when they ought to have used a freewheel/cassette with larger cogs across the board.

That's part of the reason I've been downsizing my chainrings -- to make sure the gears I actually use most of the time are in the middle of the cassette. It really does feel and sound smoother to have things lined up.

xroadcharlie

When I got my bike I used 38T chainring (on a 28/38/48 triple) since it meet my needs most of the time, but found I frequently used the smallest rear cog, perhaps cross chaining, So I switched to the 48T as my base ring where I can stay 90% of the time at 52 - 78 gear inches without cross chaining. It may not be an issue on a 7 speed cassette with the middle 38T ring though, But I still prefer the 48T ring.

This comfort bike seems to coast well, But takes a lot of muscle to motivate once I stop. So sometimes I'll drop to my 38T chainring if I need to cross an intersection quickly.

Last ride 76 

Maybe not "currently made" but what does that have to do with it...Ain't we C & V here?

canklecat

Another problem I've found with smaller chainrings is needing a smaller cog to compensate. Some freewheels and cassettes feel a bit grindy or crunchy in the top gear when the smallest cog is 11, 12 or 13 teeth. That's one reason I switched the Trek 5900 back to the 52/42 chainrings and 14-28 freewheel. Every freewheel and cassette I've tried with smaller cogs feels increasingly grindy.

It might be a chain link length issue, but I haven't found a chain that eliminates the grindy feel -- Shimano, KMC or others. It's not something I notice much on actual rides, but with the bikes on a workstand or trainer I can feel and hear it.

Probably just a minor loss of efficiency, like the pulleys I described above. But I don't have any power to spare so I want the drivetrain as efficient as possible. Little tweaks here and there seem to add up to better rides, especially long rides on hot days when I need to conserve as much engine reserve as possible.

HTupolev

Whatever works for the bike and rider and use case.

53T is the most majestic chainring size, but not always the best.

ThermionicScott 

You're probably feeling the chordal action: 2.2.1 Chordal Action If we weren't trying to make bicycles go faster and faster without adding more and more weight, we'd probably be happy with top cogs of 15 or 16 teeth. In industry, they know better than to use 9 or 10 tooth sprockets for high-speed applications!

canklecat

Yup, sounds like what I was trying to describe. Thanks!

BTW, it also seemed to vary with some drivetrains. Long cage rear derailleurs seemed to minimize the effect on a couple of my bikes, at least with the few gearing combinations I tried.

nomadmax 

On my dedicated road bikes:

34/48 chainrings, 12-30 cassettes (10 speed).

You can lose a lot more time going up a climb with the wrong gear than you can going down in the wrong gear.

bikemig 

Absolutely. If you have a stash of 7 speed 12-28 freewheels , I'd love to trade for one! I think though they were pretty uncommon back in the day.

seypat

This thing was included with a bike/parts I bought in the past year. Dude used it for TTs.

seypat

12-28 7 speed is da bomb! 2 tooth jumps to the 21. Hard to beat when paired with a 52/42/30. It's not so much the range, as the shift patterns. You can ride all areas of the range with a minimal amount of shifting. A change in rings is about 3 or 4 sprockets. You can ride all day long over varying terrain on 2-3 sprockets if you choose.

thinktubes 

I used 53T for years. Since I live in (flat) Illlinois, I would rarely need anything higher than 100 gi. The 14/13/12 teeth on my cassettes were clean as a bean. A 53T looks cool IMO.

With the 48T, I use the whole Cassette, only spinning out on hills occasionally.

For some reason, the 48T seems to provide easier options when there is a headwind. Not sure what's behind this, but I really like it in the spring when there is a constant wind off of Lake Michigan.

Last ride 76 

It's the 28 end I can't do. They end with numbers like 21, 23, and the biggie- 24... These are vintage freewheels, from the days when we were all younger, and probably like me, a good bit stronger, capable of dancing on the pedals. I love the old corn-cobs, but only use mine when I go to Cape Cod, and ride along the ocean. Wish I could oblige. But that would mean that, as a young man, I would have understood how "time" worked.

bikemig 

Hah, you and me both. I have my share of corn cobs as well. There was a time when I couldn't imagine ever needing a cog larger than a 23 or a 24 except on a loaded touring bike, . Central Iowa is reputed to be flat (and it certainly isn't terribly hilly) but I have no problem finding rides with 10 percent grades so those corn cobs aren't getting much use.

Edit: Bernard Hinault wrote (likely ghost wrote) a book called Road Racing Technique and Training. There is a lovely passage in the book where he claims that no one would ever need more gearing than a campy triple and a corn cob because with that you could climb up a wall. Yeah right, he could no doubt with that gearing but I know I couldn't.

nomadmax 

Another advantage with the 48T is you can stay in the big ring for rolling/momentum hills and skip the front shift.

SurferRosa

52 on most, but I seldom use the small rear cog.

I put a 50 on the bike with the 39t small ring, so its Nuovo Record rear derailleur could take up the chain slack and shift more easily. I have to use the small rear cog with it or I spin out.

bwilli88 

My gravel/mtb has a 52x42x34 but it is going to be changed to a 48x42x30 soon. My other bikes have 49x46x32 on my Pro-tour, 48x45 on my Zunow, and 46x34 on my Fuji.

Kabuki12

I have 53 on most of my vintage road bikes. I rarely change front rings with either a 26 or 28 rear cog. There are a couple of hills that require a front ring change , but mostly able to keep going with the big ring. Joe joesvintageroadbikes.wordpress

Fahrenheit531 

To this point I've always run the stock 52 big and 42, 40, or 39 small, but I've been thinking lately of going to 50 or even 48 on the big ring as I almost never use the two smallest cogs on the big ring.

This thread has given me the nudge I need. Thanks!

...Now it's off to C&V Sales for a WTB 130BCD chainring post.

ThermionicScott 

I know SunTour and a few other brands made 7-speed freewheels with 12T top cogs, but that was so close to the time cassettes took over that they probably didn't make them in the same numbers as other freewheels.

Or, maybe those little 12T cogs wore out fast and the freewheels all got thrown away.

If you must, I know that DNP makes an 11-28 7-speed freewheel. The e-bike crowd has created enough demand for freewheels (not cassettes) with 11T cogs that companies still make them in a variety of speeds.

bikemig 

There are posts on BF panning DNP freewheels but I may have to find out for myself if they are that problematic!

jlaw

On my two most-ridden bikes I'm at 39T large ring (10 spd) on one and 42T (9 spd) on the other.

With a large cog of 32T in the back this allows me to stay on the big ring most of the time in rolling terrain - only downshift to the granny ring for the steep grades.

bargo68 

How about IRD?

Cassettes / Freewheels ? Interloc Racing Design / IRD