Gearing
 

My venerable '72 MBGR came with 52/40 chainrings & 14/24 FW in back. It was perfectly fine when I lived and rode in Flatland (Illinois) until we moved up into SW WI late in 2013.

Or I should say until I started riding it again earlier this year, after a 12 year hiatus.

There are hills here. Some're HILLS. Even a few HILLS... it't ain't California or Colorado though so my question is:

With 120 OLD geometry in back, and a choice of cogs from 14t to 34t, what's a useful 2nd - 4th combo for recreational rides < 20 miles in length?

I'm a little confused by your post, plus you seem to be missing some information. I don't understand why you want to know just the 2nd-4th combo (presumably you're talking about rear cog positions, right?) when the 1st gear is probably the most important for getting you up and down hills. Also, what relevance is the <20 mile limit...it's the grades that define the gears you need, not the distances. Furthermore, what rear derailleur do you have on there and are you willing to change it? My Motobecane Grand Record had Campy NR derailleurs which could shift a 28 tooth cog maximum (and only with careful wheel placement in the dropouts and careful chain length setting). Additionally, what cranks do you have, and are you willing to change chainrings? Mine had a TA crankset that could take a plethora of different chainring combos. Once we get that info we can help you out some. Also note that you'll need to lay things out on a gear calculator, like this one: Bicycle Gear Calculator

Classic 48/38/28 (or even 26) triple would fix the front. How much do you want to mess with the back? There were uniglide hubs that would fit 120mm, but you would buy yourself a lot more options if you stretch it to 126mm. You could keep the 5 speed at 126mm or jump to 6 speeds on the same uniglide hub. If you jump to 130mm, then you have access to a whole lot of more modern stuff.

My Trek 720 started as a 126mm spec bike, I bump it to 135mm so I could use mountain bike hubs. It is trivially easy to do (for you to hit 126mm or even 130mm). It is a matter of what you want and what you are willing to do. Even Dura Ace had an early 120mm Uniglide hub but you'll have a bear of a time finding it and the rings for it (it uses loose rings and spacers, the last ring screws on top holding everything in place).

I'm thinking you're using a freewheel in a 1972 120 OLD frame.
I'm just finishing a 1961 Holdsworth Cyclone - 120 OLD at the back.

I've managed to fit a SunTour New Winner 13-15-17-19-21-28 in 122mm fairly easily with 52/36 at the front.
With the option of 13-15-17-19-24-32 (I've got the gears).

That should cover most 'a few hills' options.

My main bike is 52/42 + 13-15-17-19-21-24-28 7 speed freewheel and works fine but hills are starting to get difficult.

+1 to what Davester said in post #2. With a 52/40, your gearing will trend toward the high end. If your crankset allows it, changing the chainrings to something like 46/28 and pairing with, for example, a 13-26 6 speed freewheel will give you a nice range and a low of <30 gear inches.

I've read good reviews for IRD freewheels. I have a recently acquired 83' Specialized Expedition that I ordered a 7 speed 13-32 for. Stock gearing is 6 speed 13-30 out back with 28-42-44 in the front, which gives me a low of 25 gear inches. The new freewheel with front chainrings of 24-36-44 will give me a better spread and get me down to 20 gear inches. A little spendy but if it's quality and does what I need, that's a win.

I don't know if 120mm spacing will accommodate this, maybe someone else can weigh in. They do have a 5 speed 13-32 or 13-28.

You could potentially also reduce the size of your inner ring from 40 to something less.

Per this calculator (BikeCalc.com - Bicycle Gear Inches Chart) your current low gear inches is 44.

If you make any changes, you'll need to make sure your derailleurs have the capacity to accommodate those changes. I would think any change of at least 10% would be a noticeable improvement.

You are going to get much stronger and I believe that you will grow into a more reasonable 5 speed FW. How long are the HILLS and how steep and long are the toughest sections. My '78 GJ has a 14-32 6 speed FW and for everyday riding the hills here, 1000ft for every 10miles at 6-10% grades the GJ is over kill. I much prefer closer gears.

I had a grand record with suntour derailleurs. I used a suntour 14-17-21-26-32 freewheel and went half step and granny in front. 46-42-24 in my case. It was fine for touring even.

I have a couple vintage bikes geared for grade. My Tempo uses a classy looking 48/34 compact from Velo Orange upfront. The rear OLD is 120 so I run an ultra-spaced 6spd freewheel with 13-15-17-20-24-28 cogs. Climbs well and no real shifting issues from the Shimano Arabesque shift group.

https://cimg0.ibsrv.net/gimg/bikefor...6469007960.jpg

Thanks all. Useful info there, what I was looking for.

I've acquired two 'used' Suntour freewheels (English-thread) over the last couple of weeks. One's 14/17/20/24/28, the other's 14/18/23/30/34. My original Maeda Perfect's 14/16/18/21/24. Also acquired a Park chainwhip in preparation for attempting to take the cogs off these things, assuming the inner hubs are all splined the same.

Alternative is simply to make a request to PastorBobinNH for a 'rebuilt' FW to my specs should those cogs prove reluctant to come unthreaded.

Gear-inches is a new concept to me. It'll take me awhile to get my head wrapped around the specifics and how they apply to my needs but even at 74+ I'm a fairly fast learner.

As for the hills... one I found not far from home Strava measures as .70 mile start to finish with an elevation change of 252', ~ 1:15 grade or just shy of 7%.

May not be the steepest but it's a long, uphill, winding run that's a challenge to do without a stop for a minute half-way up with the 24t big I've had on the bike since... forever.

Late last week I received the 28t FW, got it mounted and a short ride in on Saturday morning. For that, Strava clocked it at 5.0 miles, 289' total elevation change. Steepest section @ 100' rise is ~ .7 mile long right at the end. The 28t makes a big difference in both feel at the pedals as well as confidence in my ability to keep cranking. (I don't mind standing to mash up short stretches but with vehicular traffic around I'm more comfortable staying seated so I can take side glances in my rear view mirror fairly often.)

I have the 34t FW cleaned up and will be doing a trial fit this evening; it just arrived yesterday. Last week I found a 'donor' '79 Fuji S-10 fitted with a nice Suntour V-GT LUXE so I bought the whole 'rescue' package. DR cleaned up quite nicely, with a new & longer chain the 28t works great and I've been told that DR should work with a 34t too so time will tell.

Bike's got a Stronglight crankset, chainwheels. I'm reluctant to put too much more money into changing anything yet this year as our riding season's growing rather shortish. Too I'm not real clear on what the BB can accommodate as far as a complete change of crankset were I to decide to move to Something Different. If I can get to where I can spin up these hills by simply changing a rear cog or three my needs will have been satisfied for now.

With a 52/40 upfront, your freewheels would be a tough choice for me. If I could dedicate this bike to mostly solo riding with the occasional 7% grade, I’d definitely go with the 14-34 freewheel. The problem I’d have is I still do a lot of spirited group riding with my vintage steel and that 18-23 jump is a doozie. I’d have to get a whole lot better at double-shifting.

That jumped out at you too eh?

The 14/34 mounted easily last night. Before I got things sorted the DR cage was impacting the large cog, something to be avoided obviously. Took some time adjusting the V-GT's stops to keep chain out of spokes and on small cog but it's all right now. Hoping to do that hill I spoke of later today once it's a little warmer and not foggy anymore, see what difference another ten teeth makes on the climb.

With PastorBobinNH's help I may go with a 32t large, see if the big 18/23 spread can be shaved a bit with a part out of his collections.

Obvious why 6 or more cogs in back have become 'normal' compared to that era, isn't it. Were I interested in doing more with this bike I'd probably be better off buying something already fitted with a wider gear range than wasting time & spending money on changing things that still work well enough to enjoy.

Again, thanks all for your comments and insights.

Assuming a (very common) 130mm BCD (or 128 for Nervar), your spider can accommodate 38T, reducing your lower-gear ratios by 5 percent. Good start.
Most derailleurs are good for 26T, so now you are at 38/26 instead of your current 40/24, and your low gear ratio has dropped by more than 12 percent, which is quite noticeable.
As indicated earlier in the thread, a short-cage Campag. NR rear derailleur may be able to handle 28 teeth in back -- definitely not true with my Bianchi frame. The best 2x6 I could devise for it was 46-38 / 13-15-17-20-23-26, which makes hills noticeably easier than the 50-42/14-16-18-20-23-26 I had run for almost four decades prior. A very popular 1.5-step 2x5 setup back in the day was 52-40 / 14-17-20-24-28, which is a very standard, easily obtained freewheel combination. You already have the ringset for that.

You mentioned gear-inches, which I find a very convenient way to describe bicycle gear ratios with wheel sizes, i.e., overall cadence and climbing effort. For years, manufacturers had settled on a 52/14 high gear ratio, which works out to 100.3 gear-inches with 27" wheels. Then one can simply regard all other gear-inch calculations of percentages of nominal top (100%) gear. Personally, I find a top gear in the mid-90s to be perfectly adequate, and have no desire to waste valuable ring-sprocket combinations on anything higher than that. I strive for about a 6 or 7 percent ratiometric progression between gears and decide whether I want half-step or, more commonly for me, 1.5-step. The double-shifts are a non-issue, because most of the time you just shift up two steps (one freewheel/cassette cog at a time), unless fine-tuning for optimal cruising on a steady grade.

So finding a 38T 'ring to fit my Stronglight cranks you suggest might just be possible? Hmmm, I can see the advantage in that once I locate one if the price isn't prohibitive; affects everything in back with one change in front.

I need to get into that a bit more. I agree it's a very convenient way to compare all the variables involved at a glance.

If your bike has Stronglight model 93 cranks, it will go down to a 38T with stock chainrings. Red Clover Components offers a reproduction of the rare, never-catalogued 37T chainring, but they're spendy at $150 a pop. They also sell a 42T triple-izer chainring which would allow you to fit a granny ring, but that would necessitate swapping out your crank spindle from the likely 118 mm to a 125 mm - those are out there, they were stock on the Raleigh Gran(d) Sport(s) that used the model 93 with an alloy chainguard in the outer position, 52T on the inside and spacers and longer bolts to hold the 42T in what would be the granny position. I am assuming you have the correct crank tool for the Stronglights with the 23.35mm threaded section, yes?

For a while in the late 90s I had a PX-10 set up with a 38T inner ring, and had I had a lick of sense I would have kept that rascal.

Yes, for going on maybe 40 years.

What would indicate the model # of my crankset? There's nothing I can find anywhere on any of the components orther than the tooth counts stamped on each ring and the Stronglight brand name cast into each arm.

Interesting bit about Red Clover Components, thanks. I'll get in touch, perhaps with more info they can provide from measurements I take we can come to some conclusions.

If your crank looks like this -

https://velobase.com/CompImages/Cran...CF3249485.jpeg

- with the star shape and a bolt circle diameter of 122 mm and both rings bolt directly onto the ends of the spider arms, then you have a Stronglight 93.

If your crankset looks like this -
https://velobase.com/CompImages/Cran...E13FB3CBC.jpeg
- where the large chainring bolts onto the crank using a 50.4 mm bcd chainring, and the smaller chainring is bolted onto the larger ring with spacers, then you have a model 49, and all sorts of other options are available.

Now, if you were REALLY lucky, you might have a model 99, that looks like this -
https://velobase.com/CompImages/Cran...21D1C3A3B.jpeg

- in which case you have a bolt circle diameter of 86 mm, and can run small chainrings down to a 28T ring - but I suspect we're not that lucky.

If you've got a Stronglight 49 (50.4 bcd) you can get new TA chainrings for it: https://www.veloduo.co.uk/products/n...f53c078e&_ss=r

Edit: TA rings in the link are outer 52-40 + inner 42-26

Here's what it looks like (new TA 52+36 on front + 13-28 New Winner ultra 6 on back):

https://cimg6.ibsrv.net/gimg/bikefor...54d71ed1e0.jpg

My Roberts has 120 mm OLD and I'm not keen on cold setting this frame. I have hills up to 20% and use 3x6 wide range gearing. The freewheel is 13-15-17-20-25-34 Suntour Ultra 6-speed, with the possibility of a 38 if needed. The chainset is Stronglight (Spidel) 106 Tri (55-43-30 (min 28)). Shifting by Simplex (Spidel) Retrofriction. 9-speed chain.

https://cimg8.ibsrv.net/gimg/bikefor...9d04143256.jpg

Stronglight triples are out there. I have a Stronglight triple crank and long spindle I'm considering letting go of next year. Sounds like you're well on your way with just the freewheel change. Enjoy riding the driftless. It's some of the best riding the Midwest has, I think.

I think too, with the right equipment and mindset. It's a challenge for me, having not been riding since about 2011 until last May.

As for my cranks, from what those pics tell me (thanks for posting those!) mine looks most like that 93 -

https://cimg1.ibsrv.net/gimg/bikefor...21983bc989.jpg

- but the 52T's what bolts to the spindle's flange, the 40's carried by the spokes of the 52T.

I'll have to make up some metric circle templates, get an idea of the bolt circle diameters after lunch. Be warm enough to ride soon, maybe I'll save the measuring 'till after dark.

Nice! A printable PDF template, ready-made! (Just be sure you check your printer's X/Y calibration before relying on what it first spits out! That's why SB thought to add those 127mm/5" lines for at left and bottom!) Thanks!

That’s a 50.4bcd model 49d with some funky aftermarket drillium.

Thanks!

And yes, the drillings were done by a friend back in the mid '70's who's job was building aerial mapping cameras.