Thursday, October 18, 2012

Bike Friday Family Tandem

After buying a tandem trailer, we used that in conjunction with the child trailer for one summer, with each parent pulling one of the trailers. At the time our children were 5 and 2. As our son turned 3, he started to be jealous watching his sister pedal, so we occasionally let them switch places. He couldn't really turn the pedals on the trailer bike all the way around, but he seemed to enjoy it anyway. However, it became clear that soon enough neither of our kids would fit in the trailer very well and that we needed a long term solution. We could have probably got another tandem trailer eventually, but at some point I started doing research on tandems. Sheldon Brown wrote a great article about tandems and kids. There were two primary features I was looking for in a tandem:
  • The rear seat had to go low enough for a 5 year old.
  • It had to be easily transportable.
In retrospect, the transportable aspect has been less of an issue than I expected because most of the family bike rides we do are from home anyway. My research has turned up a number of very interesting options:
  • Bike Friday. A maker of folding and travel bikes that has several tandem models.
  • Brown Cycles. I particularly like the "child in front" bikes they make, a feature I'm sure my kids would want if they knew it existed.
  • Co-Motion's PeriScope line. In particular, the PeriScope Trident Convertible is something I wish I had sometimes, but it's a serious investment. 
  • Circe Helios. It looks like a great bike, but they are in the UK, so getting one in the US would probably require expensive shipping.
  • Build your own. If I had the welding equipment and expertise, I would totally build one of these.

Of all these options, Bike Friday's tandems end up being one of the least expensive, starting at $1500. That's still a lot, so I started looking at used ones. Having watched several Bike Friday tandems auctioned on eBay, I have concluded that any opportunity to buy one of these for under $1000 is a good deal. I ended up paying somewhere between $1200 and $1300 for a bike that originally retailed for around $1800, but shipping costs brought it close to $1500.

This is what the bike looked like I first got it in 2010. The long stem on the rear handlebar was originally on the front, but I needed it in the back to get the handlebars closer to the rear seat. The rear seat is in its lowest possible position in this picture, which is low enough to fit an average 4-year-old, with one exception: the crank length. This bike has standard 170 mm cranks, while the typical lengths on children's bikes are 135 mm for 16 inch bikes and 145 mm for 20 inch bikes. We tried one short ride and it became clear that the adult length cranks were not going to work. There are two solutions out there. One is the "KidBack", which is essentially an additional bottom bracket and cranks that attach on the seat tube. It's designed more for full size tandems, though so the second (and less expensive but still pricey at $90) option was what I did: the Ride2 crank shortener. This device attaches to the crankarms through the pedal threads, and provides 4 alternate mounting locations. From my fairly inexact measurements, they subtract 25, 35, 45, and 55 mm of crank length, giving lengths from 115 to 145 mm on this 175 mm crank. The downside of crank shorteners like this is they increase the space between the pedals (sometimes referred to as Q-factorby an inch or so, which might make it harder for small legs to pedal.

My bike came with SRAM's DualDrive system, which pairs an internally geared 3-speed hub with a 7-speed derailleur (newer models are 8 speed, but my bike is over 10 years old). For tandems, this makes it possible to put the drive chain and timing chain on the same side of the bike.

This gearing system actually makes it possible to use a less expensive solution for short cranks, which I hadn't considered at the time I bought the crank shorteners. BMX products maker Sinz makes a crankset for square taper bottom brackets that comes in a huge range of sizes from 125 to 180 mm. They retail for around $60, but I've sometimes seen them available for less. They have a 110 mm bolt circle diameter, which fits a large range of road chainrings these days, including the ones on this bike, and they allow for the installation of two chainrings. I've read that the spacing of the chainrings on Sinz cranks will put them too far apart to work properly with front derailleurs, but this is not a problem for the DualDrive system.

Had I bought the bike directly from Bike Friday, they would have customized the size to fit me exactly. By buying used, I had to figure out how to make it fit. One problem that became clear after a couple of rides that the handlebars were too low and too close. I found this stem which seems to fit me well, and is adjustable, making it fairly easy to modify the setup to suit another rider.

At one point I decided to get a pump and a traingle cargo pack for tools for this bike. As it turns out, neither fit without modifications. The Park frame pump, which is adjustable to a wide range of frame sizes, was a quarter inch tool long at its shortest setting for the pump peg on this frame (I hope newer versions of this bike have fixed that). I eventually was able to modify the pump to fit. Likewise, the triangle pack was a little too tall for the frame, so it took some modification on a sewing machine to take the lowest 1 inch off.

Below is the bike in its current setup. Note that my kids have got taller in the last 2 years, so the rear seat is higher. I have moved the rear water bottle cage to the handlebar. My kids found it was a long reach down to the top tube of the frame, especially with the horizontal orientation of the bottle. I've also added the luggage rack and bar ends. Even for a 10 mile ride (most of our rides with the kids are in the 10-20 mile range), I need to be able to change hand positions. I may eventually try to install a drop handlebar, which is what I would have got if I had ordered a new one of these custom.

As noted in my last entry about the tandem trailer, I think I should have bought one of these earlier and never bothered with the tandem trailer. This is a much more significant investment, so it's not for everyone, but if you want to do bike rides as a family, I think the Bike Friday tandems are an ideal solution for kids who aren't yet big enough to keep up on long rides. This is also a good option for larger families because you could theoretically pull a child trailer behind one of these (up to 3 children per parent!). I do have a friend who has pulled a child trailer behind a tandem trailer, but I've been soured on tandem trailers enough that I don't think I'd recommend that to anyone.


  1. Hello,
    We are a french family, willing to buy a tandem bike friday.
    We've just found one used model , the same as yours. It is 20 years old! Is is separable only into two pieces (however new models are separable into 3 pieces.) We didn't see it yet, that 's the reason why we have some question you may be able to answer, because you have the same model :
    - When you divide it into two part, is it small anough to be carried into the plane as two normal lugages?
    - The whells : are they 20 inchs or 18 inchs?
    - What's its weight?
    - Is there an independant pedal system for the stocker?
    Many thanks!

    1. I just noticed your comment, so sorry about the delay in responding. The wheels are 20 inches. I have not tried to fit the tandem into luggage, but I think it could be possible if the wheels are removed. I have taken the bike apart to transport in a car, but I usually don't need to remove the wheels for that. The weight is about 50 pounds, which is relatively heavy for a tandem.