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Old Schwinn Continental, Suburban, Varsity Chainrings

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Old Schwinn Continental, Suburban, Varsity Chainrings

Old 11-03-19, 07:07 PM
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Schwinneffect
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Old Schwinn Continental, Suburban, Varsity Chainrings

I bought a 1975 Schwinn Suburban and took it for a ride today. I was having a blast until I came to a hill and immediately realized that I was either way out of shape, or the bike was geared much too tall. (actually both) I did a little math in my hotel room and calculated the speed in gears assuming a constant 60 RPM cadence at the pedals. The result is a max speed of 18 mph, and a min speed of 7 mph. Hmmm. 7 mph up a steep grade on a 40 lb bike with a 220 lb rider and a 32 lb happy dog--I'm not going to be able to do it unless I really live in the gym. Since I don't know anything I figured I could swap out the front sprockets for smaller ones and take a few links out of the chain, but this may not be so easy.
The larger Schwinn front sprocket is of one piece with the pant leg guard, and bolts to the smaller sprocket. Only the smaller sprocket is driven by the crank pin. My bike has a 52 tooth and 39 tooth sprocket set that must have the standard back in the seventies. A choice of perhaps 32, and 46 would work much better, but I have not found an easy way to accomplish this. Suggestions?

Here is the approximate speed in gears if I did the math right:
Front Cog Back Cog Speed

39 28 7.0

39 24 8.1

39 20 9.7

39 17 11.5

39 14 13.9

52 28 9.3

52 24 10.8

52 20 13.0

52 17 15.3

52 14 18.6

Last edited by Schwinneffect; 11-03-19 at 07:13 PM.
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Old 11-03-19, 07:33 PM
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You could try a triple setup like this one: https://www.wheelandsprocket.com/pro...d-233145-1.htm
I don't know if your front derailleur could handle this. It may or it may not.
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Old 11-03-19, 07:33 PM
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I can't say that I know what the bolt hole circumference of the USA made steel chainrings are, but I don't think you are going to have much luck finding any replacement smaller chainring. You might try to go to a long established bike shop and see if they have any 1 piece double chainrings cranksets lying around that you might be able to take off , if they are any smaller. Otherwise, your best bet, in my opinion, would be to try to change the rear freewheel to a 14-34 5 speed in order to get a lower gear. You would have to get a long cage rear derailleur and add about 4 links to the chain. In the olden days, they used to make a 1piece crank to 3 piece crank conversion kit to fit a US steel bottom bracket shell. I believe that Schwinn used this set up on the approximnate 1974 Sports Tourer road bike. It was a US made frame with a 1 piece bottom bracket shell that had a 3 piece Nervar alloy cotterless crankset. Best of luck in your project.
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Old 11-03-19, 11:18 PM
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Schwinneffect, you should GET the FREEWHEEL (or the entire wheel if you want..) from the FIVE SPEED SUBURBAN.
Why? Because the MODEL J freewheel is significantly better than the MODEL F freewheel. It has a better seal design that Shimano patented in about 1968.
The MODEL J (from the FIVE SPEED SUBURBAN has 32, 26, 21, 17, 14
The Model F (Varsity/Conti. & TenSpeed Suburban)-----has 28, 24, 20, 16, 14
******That big 32 sprocket WILL GIVE YOU THE HILL CLIMBING THAT YOU CURRENTLY LACK*******
-----------You WILL NEED A BETTER rear derailleur than the stock SCHWINN APPROVED Huret Allvit that is original equipment on Vars/Cont/10spSuburban.
THE 5 speed SUBURBAN had a SHIMANO built SCHWINN APPROVED REAR DERAILLEUR (GT-100 for 1970-1973 and GT-120 for 1974-1977)
As you know, the 1970 Collegiate 5 speed and the 1970 Suburban 5 speed were the first Schwinns to have SHIMANO. You can find the same exact FREEWHEELS and REAR DERAILLEURS on the 1970 through 1977 Collegiate 5 speed. 1970 - 1977 Collegiate has 597mm (26") wheels but the freewheel and rear derailleur is exactly the same as on the SUBURBAN 5 speed from 1970 - 1977. IMPORTANT: The 1969 and earlier Collegiate have the French made Model F freewheel and Huret rear derailleur.

You also have the possibility of going to an even larger 1st gear (LOW GEAR) rear sprocket with 34 teeth. Suntour made a bunch of freewheels with 34 teeth in the low gear.
I do know for a fact that the 1971 SCHWINN SPORTS TOURER had a 34, 28, 22, 17, 14 and then front crankwheels of 36 and 54

I do know that the 1971 SCHWINN SUPER SPORT had the 39 and 52 front crankwheels of the VARSITY/SUB-10speed/CONTINENTAL
along with 32, 26, 21, 17, 14 at the rear wheel.

The reason that you generally did not get a rear low gear greater than 28 on most TEN SPEEDS is because most ten speeds featured INFERIOR European Rear Derailleurs WHICH COULD NOT ADEQUATELY SHIFT ANYTHING GREATER THAN 28. Enter SHIMANO and MaedaSUNTOUR and you no longer have the Junky Quality of most all Huret, Simplex, and Campagnolo rear derailleurs of that time. That is not to say that a few models from those manufacturers are adequate if properly set up and adjusted, but they are all significantly inferior in durability and quality to SHIMANO and MaedaSUNTOUR rear derailleurs of that time!

Get rid of the Allvit Schwinn Approved rear derailleur. There is a reason that just about everybody went Japanese (SHIMANO or SUNTOUR) by 1977.
Shimano and SunTour were twice as good and a fraction of the cost. Yes, Kmart 10 speeds of 1972 and many other low priced no-name 10 speeds of early and mid seventies have far better rear derailleurs on them than what nearly all the prestige European brands and what nearly all Schwinn ten speeds had on them.
Shimano's Lark/Skylark/Eagle is better than anything the Europeans had ever built, and those were Shimano's base line models seen on millions of $75 ten speeds.
Yes, the weight in grams of those base model Shimano rear derailleurs of that period are heavier than the European equipment of the period, but no more than 1/4 pound at the most. European rear derailleurs are junk in comparison to anything from SHIMANO or MaedaSUNTOUR during that time period.

You do have many options to change the front crankwheels. I would first go with CHANGING THE FREEWHEEL to give better HILL CLIMBING. Be sure to get rid of the Huret Allvit rear derailleur! It is incredibly simple to install a SHIMANO and get it properly adjusted. You can even keep it all Schwinn if you want by grabbing a used GT-120 Schwinn Approved rear derailleur (original equipment on 1974-1977 Suburban FIVE SPEED and 1974-1977 COLLEGIATE FIVE SPEED. The GT-120 has the High gear and Low gear ADJUSTMENT SCREWS in the typical SHIMANO location, and shifts excellent compared to the Huret Allvit. The GT-120 is supremely durable, as are the earlier GT-100 and the other SHIMANO rear derailleurs.
You might be surprised to know that in about 1977 (see the 1977 Schwinn catalog) that Schwinn offered TEN SPEED models called the SPORTABOUT (just essentially a Varsity with SUNTOUR derailleurs) and RUNABOUT (just a tourist style Varsity with SUNTOUR derailleurs). So if you're wanting to make your bike with all SchwinnApproved stuff, you could go Suntour too.
I would keep the one piece Ashtabula crank because it is extremely durable and super simple to service. You're not going to make a Conti/Varsity/Suburban into a true lightweight so keep the best features, namely the worlds best kickstand and the it takes a beating but keeps on cranking ONE PIECE Ashtabula Crank.
If you do wish to radically change your front crank gearing, you'll likely need to change it to a modern bb adaptation. If you really hunt around though, you will have a number of tripple and double ONE PIECE Crank wheels that might offer you what you might want. The ancient Huret tripple ring set on ASHTABULA as seen on the early-mid sixties Schwinn Superior 15 speed is just one possibility. Cheap inexpensive mountain bikes of the eighties and nineties have One piece ASHTABULA cranks with tripple chain wheels. I don't think you will need anything more than just a FREEWHEEL with the 32 tooth low gear, or else a version with the 34 tooth low gear....................you will need a SHIMANO or SUNTOUR rear derailleur to be able to go with the freewheels having 32 or 34 as the LOW 1st gear.
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Old 11-04-19, 02:47 AM
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SCHWINN had an explanation of gear shifting and comparative GEAR NUMBERS and GEAR CHARTS in their old Lightweight Bicycles SCHWINN OWNER'S MANUAL back in the day.

Divide the NUMBER OF TEETH on FRONT SPROCKET by the NUMBER OF TEETH on REAR SPROCKET


Multiply that result by 27 (for 27 inch wheel size.......or instead multiply by 26 for 26 inch wheels size..) TO OBTAIN "Gear Number"

Take that "Gear Number" and multiply it by pi (pi =3.14) and YOU GET THE DISTANCE IN INCHES THE BIKE TRAVELS
WITH EACH REVOLUTION OF THE PEDALS
(Obviously, You Divide that by TWELVE to get the DISTANCE IN FEET THE BIKE TRAVELS WITH EACH PEDAL REVOLUTION)

EXAMPLE:
45 tooth front sprocket
15 tooth Rear sprocket

45 divided by 15 = 3

3 x 27" = 81 GEAR

81 x 3.14 = 254 inches or 21 feet travelled with each turn of the pedal crank

----------------------------------------------------
This Simple Method works very well for comparison among different bikes.
I'd recommend using 27" for 700C bicycle wheels since their 622mm BSD is close to the 630mm BSD of 27" WHEELS.
Use 26" for 597mm and 590mm 26 inch wheels.

You'll find that SCHWINN lists the "gear number" range in their old catalogs and literature from exactly this same basis of calculation.

____________________________________________________________________________________________________ _____
____________________________________________________________________________________________________ _____
You must remember that UPON GOING TO A VERY LOW GEAR, and it does not matter if to get that super low gear by having a much
smaller front crank wheel or a much more gigantic rear sprocket, YOU'RE STILL GONNA BE TRAVELING SLOWER,
UNLESS YOU ARE ABLE TO SPIN THE HECK OUT OF THE CRANK.
Your Aim is simply to allow yourself to keep Pedalling to keep the bicycle moving------YOU WILL BE TRAVELING SLOWLY
WHILE GOING UP ANY STEEP HILL, NO MATTER WHAT BICYCLE THAT YOU CHOOSE. Some bicycles if they are geared
for racing on the flat lands, or are all speed gears, with no climbing gears, WILL HAVE YOU WALKING THE BICYCLE UP SAID HILL!
That might not apply to some IRONMAN triathlete that probably can crank an ancient 65 pound single speed cruiser bike up a steep hill, but
for normal humans, if the hill climbing ain't there, they will be walking it up at some point on a very steep hill.
-------------------------------------------------------------------------------------------------------------------
here is where you can get some Speed at Cadence computations that are extremely accurate, just PLUG in the numbers:
BikeCalc.com - Speed at all Cadences for any Gear and Wheel
-----------------------------------------------------------------------------------------------------------------
On Oct 26th, 2019, I rode my Jan 1972 KOOL LEMON Collegiate five speed in the Bikes and Beers ride in Blythewood, South Carolina.
Ride bike, Drink stuff
I am old but I am able to train and ride triathlons which many old farts my age cannot do, so riding a heavy five speed ancient Schwinn is nothing for me on a 15 or 30 mile fun ride even if there are hills. I passed more than a dozen folks that were half my age that were riding very expensive road bikes who had toWALK their bicycles up one hill about two miles from the end. I'm twice their age, at least, and I'm riding a bicycle that at about 40 pounds weighs more than twice the weight of their SPECIALIZED bicycles, and with only 5 speeds, I can make it up the hill without any problem. The point is TO USE YOUR GEARING, BUT DO NOT EXPECT GEARING TO ALWAYS GET YOU UP A STEEP HILL..........there is nothing wrong with having to WALK the bike if you find yourself in an impossible situation. I had a good conversation after the ride with the owner of Columbia SC's CYCLE CENTER, and his lovely beautiful wife. We talked about old vintage
Schwinns and he told me his first bike was a Campus Green Continental, and I told him that I had the Campus Green Varsity fifty years ago and we talked about bike collections and collecting and other things, about how I went back to exclusively riding heavy lightweight Schwinn 5 speeds for fun and exercise.
A bicycle is a bicycle. There is no argument that the expensive bicycles that I passed that their riders couldn't get up the hill on, would probably have made it up the hill if a stronger than average person was riding them. Just like it ain't necessarilly the tennis raquet or the set of golf clubs, because Roger Federer with a raquet from 1899 will still clean any great amateur's clock, and Tiger Woods could be given the worst rusty set of irons from the 1930's and steel shafted persimmon woods from the 1930's and he'd still be able to break par and beat the top collegiate players over four rounds(72 holes).
Gear up however you might need to. The elcheapo old mountain bikes offer tripple ASHTABULA cranks of something like 28/38/48. You would have to set up an acceptable FRONT DERAILEUR that would do the tripple and perhaps it isn't as easy as it seems.
Most any bike shop that wouldn't mind an old Schwinn, can easily change the FREEWHEEL out for you, for very little cost. You got folks on Ebay selling used and new old stock bike parts and you'll likely find SUNTOUR 34-14 freewheels and the Schwinn shimano MODEL J 32-12 freewheel for no more than $20 with probably free shipping.
Don't overthink all this by just calculating like Rainman.
I'm guessing that just the 32 teeth LOWEST gear rear sprocket FREEWHEEL is likely all that you'll need for your Suburban (or the 34 teeth LOWEST one..)
That and a Shimano or SunTour rear derailleur to handle shifting something that large. Remember the ancient GT-100 and GT-120 do and the EAGLE/Skylark etc will easily do 32.
Ride on, have fun whatever you are riding!
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Old 11-04-19, 10:03 AM
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There are still 110mm crank "spider" adapters available, these adapt 110mm chainrings (1, 2 or 3 rings depending on part model) to a 1-piece crank.

Tioga offered several models including triples, which I have used.

One that I find in stock currently is this one:

https://www.bmxguru.com/collections/...m-red-usa-made

Note that the above spider has the tabs machined on both sides, for use as a double-ring setup.

Schwinn had bikes with 32-tooth freewheels back around 1970, using long-cage Allvit/Schwinn derailers that work fine with older-style, wide, bushing chain.
Here's one that "went under the knife" and had a Shimano derailer installed for some reason, perhaps because the chain was replaced with bushingless, narrower chain, or because the original derailer became bent. Works fine, and is likely more forgiving of sloppy shifting on the rider's part.
I tend to think of these low-end Shimano derailers as nearly all-metal copies of Simplex derailers, which they were.

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Old 11-04-19, 03:36 PM
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Vintage Schwinn rocks as usual with a wealth of good info! I discovered that my bike has the GT120 rear derailleur already. Perhaps the bike already has the 32 tooth rear sprocket as well. I did not count the teeth. I just assumed that my bike matched the specs in the 1975 Schwinn catalog.
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Old 11-04-19, 03:52 PM
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The spider approach seems like the ideal solution. I'm pretty sure that neither the front nor rear derailleurs would like the triple front chain ring much. When the rear and front derailleurs are on the largest sprockets as it sits now, the rear GT120 derailleur is really stretched out. I think if I put smaller front sprockets on the spider, and keep the difference in the number of teeth to 12 or fewer, it will work. I don't think a 28, and 50 front double combination would work, but a 34 and 45 double probably would if I can find the sprockets in the correct width. It seems like a lot of the single sprockets out there are for 1/8 chain. I definitely prefer to keep the original crank and derailleurs if possible. I am aware that gearing has its limits, since there is little point in a gearing that gives a 1 mph ground speed at a 60 rpm cadence--might as well just walk...
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