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Good ratios for 3x drive train

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Good ratios for 3x drive train

Old 07-04-22, 04:09 PM
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Frenzen
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Good ratios for 3x drive train

Hello guys, I think that I have the current 52-47-34 setup on my old 1984 Mikado touring bike with a 7 speed. I was wonder if there are better ratios like 50/40/28T or can be any numbers from early/late 90s?
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Old 07-04-22, 04:43 PM
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My opinion would be largely based on what size your 7 speed freewheel is. It depends on how much stuff you will be touring with and how strong your legs are/ how big a gear you want to push. If I were to assume that your cranks have a pretty standard 74/ 110 bolt pattern, They will fit, and I would suggest something like 24, 36, 46 chain rings. (better to have low gears and not need them, than need them and not have them.) An old favorite saying.
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Old 07-04-22, 05:05 PM
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Originally Posted by Frenzen View Post
Hello guys, I think that I have the current 52-47-34 setup on my old 1984 Mikado touring bike with a 7 speed. I was wonder if there are better ratios like 50/40/28T or can be any numbers from early/late 90s?
Wow, hat off to you for the ability to mash those sort of high ratios.
I damaged my knees riding too high a gear when I was young and now spin in low ratios at a high cadence so as to keep riding for as long as possible, given I no longer drive.
What suits me, a fifties male, who tours heavily laden and often with a trailer likely wouldn’t appeal given what your used to, but I would advocate for you to consider your cartilage and knee ligaments and what pulling big gear inches might be doing to your knees.
You may find this calculator helpful if you’ve not come across it before
https://sheldonbrown.com/gear-calc.html
Good luck
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Old 07-04-22, 05:26 PM
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At the risk of making sense, perhaps you should start with the gear inches or advance you want/need in low, and work from there.
Or, decide what gearing yields the lowest speed at which you can maintain steerage with a comfortable cadence.
Below about 2.5mph (~4kph) it might make sense to walk, so that might be another way to establish the low end.
My 3x7 has 24-36-46 up front, this results in a down shift on the front (e.g. 46 to 36) approximating two gears down on the cluster. This is actually pretty handy in Vermont where gradients can change rather abruptly, and the same grade on dirt can require a gear, or two, lower.
FYI, the lowest gear is a 24: 32 for a ratio of 0.75, that is probably about a 68" advance for one pedal revolution.
Hope this helps.
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Old 07-04-22, 08:59 PM
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The bike is 1984 eh. The cassette was likely 13 to 30 or 32.
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Old 07-04-22, 09:24 PM
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24-36-46
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Old 07-05-22, 04:36 AM
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How heavy of a load do you plan to carry up hills? My rando bike has a 52/42/30 crankset that works well, but that is used on a bike that carries very little weight.

My derailleur touring bikes that carry camping gear up hills, my big ring is 46 and small ring is 24.

I use those crank sizes with cassettes that range from 11 to 32 in back.

Buying individual chainrings can be hard to find and expensive. Another option is to replace the crankset, would likely need a different bottom bracket if the spindle length is wrong.
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Old 07-05-22, 06:03 AM
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Originally Posted by Frenzen View Post
Hello guys, I think that I have the current 52-47-34 setup on my old 1984 Mikado touring bike with a 7 speed. I was wonder if there are better ratios like 50/40/28T or can be any numbers from early/late 90s?
there are very inexpensive triple 44/32/22 cranks available, or 42/32/22 if you want to go that low.
If not, the often mentioned 48/36/26 is a good choice, but you're going to have to see what is available and for square taper bb. Shimano un-24 or thereabouts is a good inexpensive bb that pre covid was readily available and about 25 bucks--but you'll have to get the axle length figured out.

a good bike store can give you ideas on these parts, unless you are thinking of doing this on your own.

also, Recycle Bicycle on DeMaisoneuve might have some used cranks, you might want to call them or ride over and get an estimate on parts and labour for an installation, oretty simple stuff, and I'm sure the front derailleur can be easily moved down and work fine enough (although thats to be confirmed)

you might want to look into the rear hub and see if you can put a 8 speed on, and go up a gear, although that depends on the hub details. I'm not familiar with Mikados from that part of the 80s, so it may be a freewheel, but you might be able to put on a 8 spd freewheel also (again, availibility unknown) and of course, a new shifter for 8, unless its friction.

I recall some of the older Mikados had 40 or 42 spoke wheels.

as with any older bike, you might want to get someone who really works on hubs to check by feel if your hubs feel pretty worn, loose, overly tight etc.
They could be in terrible shape, so just be aware.
I assume this is a 27 inch bike?

overall, just be aware of the climbing costs of replacing this and that on an older bike, might end up being not worth it, unless you can do the work yourself.
Its too bad that ABC closed years ago now, they were always a good recommendation for good work and estimates also.
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Old 07-05-22, 06:10 AM
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re changing a crankset
read up on chainline, and about how far a crankset is supposed to be out from the middle of the frame. The bb axles have different lengths , so you need to combine a crankset with an axle length so that the chainrings are in the same position as the present crankset.

there may be frame considerations , as well as fd also, but an experienced mechanic should be aware of all this stuff and can advise you properly of your options.
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Old 07-05-22, 07:58 AM
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Many years ago, on an 8-speed bike I changed out a 30/42/52 crankset for a 22/32/44. This put the crankshaft centerline way off necessitating a BB change. I was not even aware of different BB spindle lengths at the time. I was lucky that there were no interference issues.

I also recently changed a 9-speed bike from a 30/42/52 to a 26/36/48, and this required no BB change.

You have downtube shifters (not STI)?




Originally Posted by djb View Post
re changing a crankset
read up on chainline, and about how far a crankset is supposed to be out from the middle of the frame. The bb axles have different lengths , so you need to combine a crankset with an axle length so that the chainrings are in the same position as the present crankset.

there may be frame considerations , as well as fd also, but an experienced mechanic should be aware of all this stuff and can advise you properly of your options.
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Old 07-05-22, 02:30 PM
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If it is from 1984, could the rear hub spacing be 126mm?
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