bark_eater 

I'm looking at swapping out the chainrings on my skinny tire, 1989 Centurion Sport DLX, and running a 50-34T compact double. I have all the stuff at hand, and would use an Alevio long cage derailleur that wraps 42T.

So far with the original derailleur and a 14-28t free wheel I have tried:

52-40T (original 130 bcd crank) Spent all the time in the 40T, wanted lower gearing

48-38T Big ring got more use, Felt like there was too much overlap in gearing and I could use a bit more "granny"

Right now I have the 48-36T front with a 14-28 I live on the "Coastal Plain", and it pretty flat, but we have wind to contend with. Presently the gearing gives me a pretty good dual range, big ring to push with, small ring to cruise with. I'm definitely getting close to spinning out on the minor down hills, and I'm not going to say there's too much "granny"

So 50-34T is the next combination to try. But am I crossing over into diminishing returns? The are 2 other wrinkles. I have another bike I would like to but the 48-36T rings on. This other bike will be more of an all rounder for "cruising" and the Centurion will be more exclusively an exercise machine for local 12-30 mile rides. With that in mind, a 14-24T free wheel might be good for keeping cadence and heart rate where I want them.

But..... then have I come full circle?

Ex Pres 

Have you run a gear spacing chart to check out your new choice versus the old ones?
Personally I think it sounds good.

bark_eater 

I've looked at the the numbers a bunch, but I'm not sure how mathematical symmetry works out in the real world. I know that 50-34T is a standard for compact doubles, but with a 6 speed free wheel there only 3 readily available combinations: 14-24, 14-28, and 14-32, So I figure some one has run this set up before. Not a big deal for me to try it out I just need to make sure I always have a comparable bike ready to go before tearing into something that's not broke.

bikemig 

If you need a 34-28 to climb in, then this makes sense. Personally if it were my bike, I'd run 7 on the back to eke out another gear as well.

bark_eater 

I'm kind of digging the SIS on this bike. I run 7 speed friction on other bike's fine, but this has been pretty slick shifting front and back at the same time with one hand. That's "double shifting"?

SJX426 

Nice bike. If you have the room, 7V is nice and would help your range and midrange options.
Have you though about running the right brake cable on the other side of the stem?

https://www.gear-calculator.com/

steelbikeguy

as noted, it's always good to calculate the gears that the 50-34 and any potential freewheel would give you. With these compact gear arrangements, the big compromise is the big jump in gears when you shift between chainrings. For my bikes, this generally requires two shifts in the back to get to the gear you wanted.

The other compromise is the amount of overlap in the gear sizes you get with each chainring. Without much overlap, you have to make a lot of chainring shifts when you are on a slope (or wind) that puts you in a gear close to where the overlap occurs.

I've got one bike set up with a 50-34 and a six speed freewheel. The freewheel is a 13-26, and the gear spacing is slightly greater than I prefer. I'm much more accustomed to a 13-24 six speed. Still, it is pretty good and lets me do hilly rides on a vintage bike.....



I've got another bike with a 50-34, but with a 12-27 eight speed cassette. A bit better gear spacing and slightly higher top gear (I don't know if I've used it or not).

Steve in Peoria

bark_eater 

Yea, I thought about trying to photo shop that out before posting... I did a handle bar swap, the bike came with a 110mm Technomic stem at full extension. I replaced it with a 90mm stem and Narrow Randoneur bars set lower. The PO probably flipped the cable over for more extension and I didnt catch it. I'll probably try a different set of bars before replacing the housing and cables all around.

I've got a 14-24T freewheel in the pile and I think I can get enough chainwrap with the original derailleur to run as is. I'll have to but my math hat on later and recheck.

PS. The gear calculator puts me at a 26T chain wrap, so this would work.

clubman 

I'd just go with a 50/40/30 triple and your 14-24. No shame in having a granny at my age. Compact doubles for 7 speed era bikes are getting rare but triples abound, imo. Lot's of period derailleurs available too if you need more wrap.

rccardr 

50/34 with a 6 speed freewheel works great. I preferred a 13-28 (13-15-17-19-23-28 if I recall correctly) to get a range of about 30 to about 100 gear inches. Should be plenty for the kind of riding you're doing.

That would be a UG freewheel, of course. PastorBob could probably set you up....

bark_eater 

I'm running a Shimano RSX 110bcd road triple with 2 110bdc rings right now. This bike is sort of a place holder for a schwinn Tempo that will be a 7 speed compact double. The bike I'm stealing the present chainrings for is a lightweight Koga Miyata sort of in the same weight class as a Miyata 1000. I tried this bike out as a loaded tourer last year and it was too light of a frame, so the Koga is getting sport tourified and the Centurion is getting more sportified as an exercise machine. And I need to keep one of these bikes road ready as I pick away at all the other numerous concurrent projects. And I'm rambling.....

clubman 

I had an RSX road triple on my '97 Lemond but it was too 'compact' for fast rides so I went to the RX100 50/40/30 and found it filled the gap. Different animal. I've still got the RX100 if you have any interest.

ljsense

I'm curious how you guys are running a 50/34 compact crank with a 6-speed freewheel and finding a chain that works well on both ends.

The 50/34 cranks I'm familiar with all came out in the 10-speed cassette era or later and want a narrow chain. Are they producing 110 bcd chainrings for thick 6/7 speed chains?

A long time ago I tried running a 7-speed chain with 10-speed cranks, and it was a nightmare.

stardognine

I’m running a 48-38-28 Sakae FX up front, with a 6-speed Suntour Perfect, I think it’s 14-32t, with 1st gen XC derailleurs. I’ve been using the Suntour Power Thumbies it came with, but I’m itchin’ to try some XT M732 thumbies I’ve been carrying awhile. Those are 7-speed, but I’m thinkin’ they might play along. 🤔😎

fietsbob

In my lighter youth day My hill climb bike was a 52-36. 13-28t freewheel 6 speed..

Pars 

I have a 50/34 Campy Centaur compact on a Trek with a 13-24 freewheel. I run an 8 speed KMC X8.93 chain (crank is 10 speed) and it works great.
I don't use the 34 much in flat Illinois though. R der is a std. cage Cyclone and it wraps just fine.

bark_eater 

My crank is an RSX triple off of a 7 or 8 speed bike. I put 2 Sugino Aluminum chain-rings on it. As I remember the original steel shaped, ramped and pinned chain-rings used washers with the chain bolts. I didnt have to use these with the thicker rings, but then again I am shifting the front with a friction shifter. I bet you could use washers to shim out a 9-11 speed double to get an 8 speed chain to work. Shimming a triple would be a lot fussier.

Miele Man

I have a nice double crankset with drilled 34-50 rings, in my spare parts box. I had it on one of my bikes with iirc 7-speed cluster and liked it a lot. I only replace it when I put a complete Shimano 600EX Arabesque groups set on it.

The 34 ring was quite handy for riding trails where there were sudden changes in the gradient of the trail - fairly flat then a turn and a steep grade.

On another one of my bikes I switched to a 30-42-52 triple crankset and bought an inexpensive (but not bottom of the line) rear derailleur. I have downtube shifters on that bike and there's no problem shifting the longer cage derailleur. I was lucky in that my original bottom bracket was long enough to fit the triple onto.

If it gets to where I can't ride my 42-52 chainring bikes up hills without severe effort I'll put that 34-50 crankset of one of them.

Cheers

ridethecliche

If you're friction shifting it doesn't matter. Just get a more modern cassette as well. You could go 8/9/10 speed just fine.

dddd

That's what I'm running on my everyday-rider Pro-Tour. The crankset is old 110mm Mighty and the freewheel is UG 13-28t.

No complaints, but the wide chainring ratio gap has me often throwing the bar-end shifter 2 cogs at a time to maintain cadence.

Sunrace makes a 13-28t 7s freewheel, but I would have to re-space my axle and my frame is only 123mm wide.

hermanchauw

Any combo is good if you choose it, not arbitrarily chosen by some manufacturer.

I am using 26-38 front, 11-40 rear. 17.6-93.3 gear inch. The 38 chainring gives 25.7-93.3 gear inch. I can do everything with it from climbing to cruising. Haven't used the 26 chainring yet.

nomadmax 

You have to shim the chainrings (only one) on modern cranks to allow for the wider chain.

https://wheelsmfg.com/products/crank...g-spacers.html

bikemig 

There are lots of "vintage" compact cranks. One of the earliest (if not the earliest) 110bcd cranks is the sugino mighty tour. Triples for a long time were 110/74 bcd and you can run those as a compact double. They came on mountain bikes, touring bikes, etc. There are a lot of them out there and the higher end ones are very high quality.

DorkDisk

Currently running a 11sp GSX crankset 46/30 on a 8sp 11-28 cassette with an 8sp chain. Normally I would use a 9sp chain for this but it is working well. GSX does have a wider chainline and q if you're sensitive to that.

bark_eater 

Did a 25 mile ride the other day with the present gearing and my gear inch range was primarily within 72 to 44". I'll head over to nearest hill next and see how I do. I might be in a dont fixit if it aint broke place already.