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

  • What are your current chainring sizes and bcd? – Andrew Aug 16 at 16:48
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    Chainring sizes: 54-48-40. Couldn't get a reliable bcd measurement yet. – Copil tembel Aug 16 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 at 20:27
  • @Andrew You are probably right, might be 130 BCD. I'll get a better tool to measure it. – Copil tembel Aug 16 at 21:27
  • That seems very high geared if your wheels are normal sizes; especially the chainrings seem big – Chris H Aug 17 at 6:29

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 at 16:58
  • Yes, I want an overall lower gear. Chainging cogs on the freewheel looks tempting, but where would I find suitable cogs? – Copil tembel Aug 16 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. – Copil tembel Aug 16 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 at 20:14
  • I'd really prefer not to end up changing the spider or even worse the axle...:~ – Copil tembel Aug 16 at 20:49

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. – Copil tembel Aug 16 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 at 6:33

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