ACHiPo 

I’m getting ready to start a winter project refurbishing a 70s Japanese touring bike. It currently has 52/40 chainrings in front and 14-30 freewheel in the back. It has a Suntour 7 GT long cage rear derailleur, which can handle (I think) 34 - 38 max freewheel (depending on where I look). I’d like to get to a 1:1 ratio for steep hills. My questions are what the best way to achieve a 1:1 ratio, and what tradeoffs I’ll be making for shift performance? Also, if I add a 3x up front to get the desired granny gear, what freewheel gears, if any, will I need to avoid too much chain slack?

rgvg

I'd swap out the front to a triple, but that's just me.

repechage

With a triple pilot control to avoid bad chain line. Note a gear chart, most often bad chain line combos will be duplicates or near duplicates with other combinations.
small ring, small cog is easy to avoid.
‘the large/large is not good either, up to you if the chain should be long enough to avoid catastrophe.

Sierra

Here's how I set up the gearing on a '76 Schwinn Superior that I made a "tourist" bike from.
Didn't need to go to a triple.

zukahn1 

I would suggest going with nicer 48-36 steel front chain rings and good modern 8 speed chain and leaving the rest alone if a all is good.

Mr. 66

I would be tempted to put an old MTB triple on that, and just leave the rest as is. Your Suntour can handle handle it.

ACHiPo 

Thanks all.

ACHiPo 

This was my primary concern. As long as the Suntour rear derailleur can handle the chain necessary for both the 52 and 14 (should be no problem), and the front can shift from a granny gear to the 40 to the 52 and back, life should be good. It actually may be ok as-is with the 40/34 combo.

abdon 

The nice thing about a triple with a 28t Granny is that you can have a closer ratio on the back and still achieve a 1:1. 13-34 requires big jumps, 13-28 not as big. That makes it easier to find the ideal gear for a given situation.

ACHiPo 

This was my primary concern. As long as the Suntour rear derailleur can handle the chain necessary for both the 52 and 14 (should be no problem), and the front can shift from a granny gear to the 40 to the 52 and back, life should be good. It actually may be ok as-is with the 40/30 combo.

ACHiPo 

If I can find a triple that works with the bottom bracket and has a 26 or 28 granny...

ACHiPo 

Nice looking bike! What rear derailleur is that?

RiddleOfSteel

As others have said, triple is your friend. I use it with 9- and 10-speed cassettes, even ('80s Trek tourers for me). It lets the rear gear set be tighter for all the benefits that tighter ratios bring, while easily providing a 1:1 ratio or sub-1:1 ratio. You get the additional aesthetic benefits of a triple on a tourer as it looks the part. I also like that the 26-28t small ring handles the slow/hard stuff, which allows the big ring to be 52-53t to handle all the downhill speed fun. I enjoy my dessert after eating vegetables. Plus, on 65cm+ frames like I ride, a 53t big ring gives a proportional look, which I appreciate.

You can geek out on the gear ratio calculators, and I have before, but a 52/39/28 up front and 13-28 6- or 7-speed freewheel out back (or very similar) should set you up for a lot of success. 8-speed indexing chain from SRAM or someone will work well.

abdon 

That's not an issue, it is to be expected. Fortunately bottom brackets are cheap and you can upgrade to one with sealed bearings.

ehcoplex 

Did someone mention gear ratio calculators? My personal favorite.

nlerner

I highly recommend this route as (1) 50/34 cranksets are readily available for relatively small money (e.g., this one and this one); (2) you likely could keep the existing bottom bracket; (3) you'll get a nice even gearing range as shown in @Sierra's chart above. Easy peasy.

davester

A more important question is "Are you going to actually do fully loaded touring on this bike?" If so, then you need much lower gearing than 1:1 and will need a crankset that can accommodate very small chainrings (i'm thinking 26T) in addition to having a 32 or 34T cog on the freewheel. This will get you down to close to a 20 inch gear which is what you need for steep grades with a full load. Also, when touring you have zero need for a large front chainring. 52T is frankly ridiculous. Get thee to a good gear calculator and figure out what will work (e.g. Bicycle Gear Calculator).

ACHiPo 

Thanks!

ACHiPo 

No to fully loaded touring. Yes to ~2 mile grocery runs down then back up a 5% - ~10% grade with a few pounds of food. And relaxed gravel riding unloaded.

abdon 

Honestly for that 40/34 gives you about 31 gear inches on 27" wheels and should be enough for low gearing. I would push over the humps pedaling off the saddle.

You can have your cake and eat it too with a standard (old school standard) triple running it as a double. The smallest middle chainring you can run there is 33t which will give you the 1:1 ratio, and then just take out the small ring. Because you are not running it as a triple the current bottom bracket could work. Could being the key word.

Sierra

I have in my notes that both derailleurs are Suntour Cyclone, but the rear doesn't look like a Cyclone.
The bike is presently in storage so I can't look at it right now to check.
There is some sort of "click" in the r. der. that I've been meaning to investigate.
If I can't fix it easily I'll just replace the derailleur with a decent mountain bike r. der.

79pmooney

That would drive me nuts. The hill starts out gradual so I drop a gear at a time to the 24. 38" so still work and the bike is moving nicely. But it gets a hair too much and I have to drop another 10 cog teeth! Now I am just moseying, taking the slow route. Doing that huge shift up to the next gear as the road levels out a touch? Not happening. I value my speed uphill. Speed = energy I've got. Money in the bank. Squandering it never sat right with me.

I would far rather have a 50-38-26 triple and swap that 34 for a 28. Or 50-38-24 X 13-26. (Portland, OR has some real, fast descents. I like a big gear simply to steady the bike if I need to. (Plus - getting that to-die-for tailwind and not having the gear to do it justice is passing up one of life's treasures.)

Edit: Dropping the freewheel to a much smaller 28 of 26 means you will almost certainly be able to run a triple and hit every combo without damage. I never, ever set bikes up so big-big isn't perfectly rideable. I rarely do it except when I've crested a hill in the big hill la-la land mental state and pulled back that left hand shifter. Done it more than a few times. That it doesn't cost me more than a few cents of chain wear instead of: twisted derailleur, perhaps broken spokes, damaged chainstay paint. perhaps gouged chainstay, probably twisted or broken derailleur hanger, possibly broken dropout ... well, I'll take the expense, $$s and weight ... for those two extra links any day.

Small-small and slack chain? I try it on the stand. Does it work? (Not is it quiet or pretty.) If the chain runs and nothing bad beyond sound effects happens, fine. Can go on my bikes anytime. And I sometimes use that noisy small-small with the derailleur arm folded all the way back and not quite pulling out that half inch of droop between the idler derailleur pulley and the chainring. Usually going up that long, hard hill when, for the next half mile, the hill levels out. I could make these tired legs and wobbly brain go two double shifts or I can just throw the lever forward and pretend I don't hear the racket. Hill resumes and "oh yeah! All I have to do is haul back that one lever, the easiest shift on the bike."

I've run that exact scenario I'm describing on many SunTour derailleurs. 7GTs starting with the cheap steel one, V-GT and V-GT Luxe, Cyclone GTs and several of the newer ones. Probably a few others. I started racing on V-GT Luxe, a 13-21 freewheel and 52-42-28 crankset. Didn't use the inner chainring in races. Screwed the limit screw down to make the bike a double for the bigger races. Next year I got a real race bike. Much nicer but the drivetrain didn't get me there any faster. (The rest of the bike sure did but that's another thread!)

Sierra

Different riding style.
It's not a go fast bike and I'm not a go fast rider.
The OP is also not asking about a go fast bike.

abdon 

Yeah, but it would only drive you nuts for the small portion of the two mile trips the OP intends to trek this bike on. If that's it I would just pedal off the saddle for those bumps and call it a day. Occasional off the saddle pushing is good for the soul.

On touring triple my favorite combo is 48/38/28 with an 8-speed 11-28 butt. The 11-28 keeps ratios close enough and the incline determines whether I'm shifting up and down from the big or middle ring.

ACHiPo 

No problem. Thanks.