Graeme Bedser

I have an old Cannondale road bike I use as back up and for visiting friends. Now living in a hillier area than before and the gears and my (and friends) aging legs don't handle them too well. So I'm looking for the smart way to upgrade. Currently have downtube shifters, Suntour components, double chainwheel (40/50) and 6 sprocket cassette (15-30). So gear inch range is 36-90. Ideally I'd like to expand that range at both ends.

Is there some reasonable way to do this? I'll take the bike to my local shop but wanted to get some independant expert advice first.

Bikewer

Certainly possible to go to a triple crank, but you will probably have to change bottom brackets as well. Your front DR may or may not be compatible, you may have to go to one with increased capacity. Is your left shifter index or friction? In order to handle the increased chain slack from the "granny", you may require a long-throw rear DR as well.
Depending on the rear dropout width, you may be able to easily go to a seven-speed cassette, but going up to a 32-tooth low-end cog may also necessitate that larger-capacity rear DR.
All doable, of course, but you may be in for more bucks than you reckoned. There's always EBay....

Graeme Bedser

Thanks! Very helpful. At least I won't be too shocked when the LBS gives me a quote. I like your eBay idea.

Bockman

You will run into a problem with the rear triangle being too narrow to accept other cassettes. Unlike a steel bike, you can't tease the stays apart-- it'll just crack.

sydney

Well atually that is the street wisdon, but both Zinn and Sheldon Brown have said that just cramming in a wider 130 hub is a non issue. That is different from trying to spread the stays to a permanent 130 set. Going to a 126 7 speed is a total non issue.

Bockman

a non-issue? hm. interesting. I lived the non-issue last year when I cracked my ancient Campy rim and had to rebuild the rear wheel. The old suntour freewheel hub (which I presume the originator of this thread has, not a cassette hub) is substantially different in width than a cassette hub.

sydney

Well, rather than generalizing, you need to understand OLN(over locknut) hub widths. Both 6 and 7 speed cassette and freewheel widths would generally be be 126. 5 speed and ultra 6 freewheels generally used 120 spacing. Given that OLN can even be different than the 120/126/130 often cited for rear road hubs, it pays to measure.Aslo it's a pretty fair chance he's got a non untra 6 speed freewheel rather than a cassette. You'd be surprised at how many don't know the difference between a freewhel and cassette and use the terms interchangably.

John E

Assuming your crank has a 130mm bolt circle diameter, here' s my vote:

1) replace the 50-40 rings with 48-38
2) replace the 15-30 6-speed with a 13-32 7-speed freewheel
This will raise your top gear by 11 percent (90 to 100 gear-inches) and will lower your bottom ratio by 12 percent, without requiring any changes to your cranks, derailleurs, or rear hub and axle.

Gonzo Bob

Is it indexed shifting? If not or you're OK with switching to friction, you could get an 11-34 megarange 7-speed freewheel. The rear derailer needs to be "alpine" for this to work so it can handle the larger 34t cog and wrap enough chain.

funbun

If you really want low gears check out this Quad Chainring Setup:
https://www.abundantadventures.com/mt_triple.html

I plan to use one of these Quad Chainrings for my recumbent bike I'm building. I figure 20, 30, 46, 52 tooth chainrings would give me 16 to 120+ gear inches on a 26 inch wheel.

4 Chainrings * 6 gear cassette = 24 speed. Not too shabby. If you mod the front derailleur you could have 5 chainrings * 6 gear cassette = 30. Your now in 10 spd cassette territory! Here are better photos of the Quad and Quintuple Chainrings.
https://www.abundantadventures.com/mt_plus.html

Graeme Bedser

Thanks again for all the input. Yep.... you're right I don't know the difference between a cassette and a freewheel and will rectify that gap in my education immediately. And I'll follow up on John E's suggestion - sounds pretty cost effective to me.