Originally Posted by canklecat

My 1989 Centurion Ironman still has the original 7-speed indexed downtube shifters. I've ridden fast group rides, long casual group rides, solo centuries and snagged some of my personal best times on Strava segments, including a couple of top tens, on that bike.

Yeah, it takes a bit more care in balance to hold a line while shifting. But most riders get the hang of it with practice.

Usually I ride with 13-24 or 13-25 freewheels on solo or fast rides, 13-28 on casual group rides. With the 28 big cog I can usually sit and spin more often. But with only 7 cogs, choices are limited and the more we try to stretch from 13 to 28 or more, the bigger and more awkward the gaps are. Even a 13-25 freewheel can have some slightly awkward gaps between some cogs, compared with a 13-21.

However, if you watch enough films of older grand tour races, including the Greg LeMond era when downtube shifters were still used and the film/video quality was very good, you'll notice that riders shifted less often than they do with brifters, and tended to get out of the saddle more often, if only briefly, to regain or maintain momentum on climbs or breakaways, rather than shifting to maintain a cadence. It can be more tiring, which makes the strength and stamina of those riders more impressive. Not that contemporary riders are any less impressive, but their gains are more in terms of aerobic capacity and ability to maintain a fairly fast cadence, rather than brute strength to grind out 40-60 rpm on climbs in ridiculously steep gearing.

And when riding a bike with downtube shifters and old school gearing, on hilly terrain and mountains it'll often be necessary to stand at least sometimes to climb. When riding alongside folks who aren't using downtube shifters, it's best to leave plenty of room around you in all directions because, for riders who usually sit and spin, they won't be expecting the slight rocking and chugging motion that accompanies standing to climb or maintain momentum. Even when standing to climb with brifters, if you practice you can shift while standing and not miss a beat. That's practically impossible with downtube shifters and I'm not sure I'd trust anyone who tried to shift that way while standing to climb. So when I'm the lone oddball riding an old school bike in a group, I leave enough room to avoid annoying or alarming anyone around me. Often I'll drop to the back on climbs and catch up on the downhills.

But since getting carbon fiber bikes with brifters around 2018, I don't ride the Ironman with downtube shifters quite as often, other than solo or casual group rides. I'll always enjoy the experience of my first road bike, a mid-1970s Motobecane with downtube friction shifters. But it's easier to meld with a fast group and go with the flow using brifters, and in some cases trying to maintain a somewhat faster cadence rather than mashing. Especially on roller coaster terrain with lots of shifting.

Regarding criteriums, the last races I rode were in the 1970s, so everyone used downtube shifters. Most crit courses are pretty flat, so you don't need to shift often anyway. It really shouldn't be an issue unless it's an unusually challenging crit course. Our courses were on big industrial park parking lots, as flat as can be, and I don't recall ever shifting gears after the start. Maybe for a sprint finish, but I usually avoided those after a bad crash in one sprint finish. After that my goal was to finish in the middle of the pack, stay upright and safe and just have fun.