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I have an older touring tandem bike that we use to go on long trips. The gear setup is 3x7. I noticed that we hardly ever use the smallest 3 cogs on the freewheel (of course together with the largest chainwheel). We also struggle on the climbs, so I would like to change the freewheel to help us on the climbs.

The freewheel setup is 13-30. I am thinking or replacing it with something like 16-36 or similar. The problem is that I haven't found a 7-gear freewheel with such a setup. The only freewheel with a better setup that I've found is the Sunrace MFM300 7DV. But the difference seems to be major only on the largest cog (30 vs 34).

This is the current freewheel:

enter image description here

Do you know where I could buy a freewheel with a better setup for climbing than this?

Or would you recommend that I do one of the following?

  1. Change the chainrings - from what I see, I would have to change all 3 of them, as the screws on the smallest chainring would not allow changing it with a smaller one. Seems to involved for my bike repairing skills.
  2. Change the back wheel entirely to support a newer, cassette style type of cogs. One problem is that the back wheel is also fitted with a drum brake on the left side, no idea how to properly re-fit it on a new wheel. Also, I would like to keep as many original parts as posible on the bike.
  3. Changing the wheel's hub to a freehub to support a casette. This has the advantage that the bike will stay with most of its original parts, but would be really involved. Again, might be difficult to impossible to re-fit the drum brake.

Advices welcome, I'm not an expert bike tehnician.

Chainring sizes: 54-48-40.

Current chainrings:

enter image description here

Chainrings' Bolt:

Chainrings bolt

Update a few months later

I thought it would be useful for anyone having a similar question to have an update on this question after following the very good advices that I have received here.

What I ended up doing: I replaced the right side crank and chainrings for a lower overall gear. Unfortunately I couldn't replace just the chainrings, as there was no way to fit smaller ones on the existing crank. I only replaced the right side because this is a tandem and on the left side there's the connecting chain. Finding a complete tandem crankset is difficult and more expensive, but fortunately replacing just the right side of it did the trick. The only difficulty was finding a crank with exactly the same length as before.

I also replaced the chain, as it was very dirty. Unfortunately this led to the replacement of the freewheel, as the new chain was slipping on the old one. I guess it was also worn out.

Although I couldn't avoid an upgrade spiral, I managed to bring down the gear ratios so now we can enjoy more difficult rides.

Indeed, replacing the crankset was quite easy and I might actually do it again if I notice that we need an even lower gearing.

Thank you for the advices!

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  • 1
    Chainring sizes: 54-48-40. Couldn't get a reliable bcd measurement yet.
    – mangafaua
    Aug 16, 2020 at 19:46
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    Looks like the visible bolt is probably 130 BCD. Typically in that case, the innermost chainring has a separate set of bolts only visible from the back side with 74 BCD. If that's the case, you can go much smaller chainrings. I think the limit for 74 BCD is around 24t. But it's possible that you've just got a double crank and the innermost is attached through the same 130 BCD bolt with a spacer, in which case a new crank is needed in order to go smaller than 38t, but you should at least be able to drop from 40 to 38..
    – Andrew
    Aug 16, 2020 at 20:27
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    Aside - you can prolong the life of your components by cleaning the drive train.... more often than you had been. Downside, a tandem has more bits to clean, so there is more work to do, but still less than two separate bikes. Thank you for coming back and updating the post with your results - that is definitely appreciated.
    – Criggie ♦
    Dec 26, 2020 at 13:04
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    @Criggie: Yes, this is one of the lessons learned: clean the components much more often. Too bad I only learned it after some of the original parts have worned out...
    – mangafaua
    Dec 27, 2020 at 7:31
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    @Criggie: I would like an internal hub, but I also like to keep the vintage look of the tandem (it's from the '80s). And yes, there is a third (drum) brake that I would like to keep, no matter what other changes I make to the drivetrain.
    – mangafaua
    Dec 27, 2020 at 7:34

2 Answers 2

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I think in this situation, to avoid an "upgrade spiral", you will be better off changing your chainrings. Chainrings are not overly expensive and probably won't require new derailleurs or shifters.

I have been known to take apart freewheels and change the cogs. I've even re-spaced them or changed the numbers of speeds. But if you want an overall lower gear, you should probably change your chainrings.

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  • Agreed. Changing the chainrings is a better way to move the entire range of gearing. And it's arguably easier than changing a freewheel. There are shops that will customize freewheels, so that might be a possibility.
    – Adam Rice
    Aug 16, 2020 at 16:58
  • Yes, I want an overall lower gear. Chainging cogs on the freewheel looks tempting, but where would I find suitable cogs?
    – mangafaua
    Aug 16, 2020 at 19:48
  • Changing the chainrings sounds also very good, but it just seems to me that right now it would not be possible to fit a smaller chainring than the smallest one already installed. I'll attach a picture of it.
    – mangafaua
    Aug 16, 2020 at 20:06
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    Concur - but a possible problem here is that the smallest chainring is limited by the BCD, so it may require a new spider. Hopefully that slots onto the BB axle, but it might need to replace that too, which could interfere with the timing chain on the other side. Hopefully OP can get a 30 tooth inner chainring on, with the 40 and 54 for a wide range. Given "older tandem" it could be a normal square taper which would be ideal.
    – Criggie ♦
    Aug 16, 2020 at 20:14
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    I'd really prefer not to end up changing the spider or even worse the axle...:~
    – mangafaua
    Aug 16, 2020 at 20:49
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A quick search shows many 14-34 freewheels available. One issue I have with the 34 tooth is they all seem to use the mega-range design. With this design the tooth count jumps from the 28 tooth gear to the 34 tooth. If you look at your current freewheel you can see how each gear is supported by the smaller gear next to it. With the mega-range design the large gear is mostly unsupported. I have seen strong riders bend the gear. The other potential issue is whether your current derailleur will support the large cog. You could install a 14-34 freewheel and if your rear derailleur doesn't have the tooth capacity adjust the high stop screw to eliminate the smallest rear cog or two. You may also need a new chain with enough length to accommodate the extra teeth. This doesn't negate the potential of bending the 34 tooth cog.

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  • That's the thing, I would prefer an even "easier" setup, 16-36 or easier. Even better without the mega-range wheel (since it's a tandem, it is quite likely that we will bend it). But I cannot find any.
    – mangafaua
    Aug 16, 2020 at 13:10
  • It can also be a pain shifting into the 34T sprocket on mega-range. Just when you want to keep pushing hard, you have to back off the power quite a bit and for longer than a normal shift
    – Chris H
    Aug 17, 2020 at 6:33

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