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tandem(11 posts)

Sep 30, 2003 11:26 AM
I've got enough parts laying around to build up a tandem. So, what would I be getting into with the ChucksBikes Tsunami frame. I think $385.00 is to good to be true. But maybe it would make a decent entry level tandem. Any thoughts?
re: thoughtscyclopathic
Sep 30, 2003 1:58 PM
beware some road parts won't do for tandem.

Seatposts are 29.6mm, handlebars usually wider (44cm+), MTB cassette/rear der (and you will find out why on first climb). You will need to get tandem cranks. However if you have 2 sets of road cranks (one triple) you could build tandem set all you need to buy is 39T chainring. Sheldon Brown should have some instructions on how to.

Brakes. To my taste road brakes don't have enough power to stop tandem. It is common to run front V/rear disk or at least front/rear V. If you live in mountainous area you'd better off running rear disk (mechanical disks are ~50$). You tend to drag rear brake and on 70mph/10mi downhill it is easy to overheat rim and blow tire.

Most important you'd need new wheels. Tandem wheels usually build with wider 22-24mm rims (Mavic T-520 or Sun CR-18), x4 48-40 (or at least 36 spokes); rear spacing is 145mm, not 130 or 135. However, there's 15$ axle conversion Wheel mfg kit and 10$ longer skewer, available through QBP catalogue at any LBS.

I guess on cheap with 400$ frameset you could get tandem build for 800-1200$, maybe even cheaper. Which is a great deal in tandem world, really.


PS. Chucks frameset is o'k, I had build one. I'd probably replace fork with carbon one though.
What are you trying to accomplish?Spoke Wrench
Sep 30, 2003 2:10 PM
I don't think that your box of old bike parts is going to make a very good tandem. Two things to think about with the Tsunami frame are: How wide is the rear triangle? and How does it take up the slack in the timing chain?

Most tandems today require 145mm rear hubs. Some builders, like Santana, use 160mm hubs. You can take a narrower hub and make it fit with spacers and a longer axle, but it'll still have shallow spoke angles and may not be up to tandem use.

Most modern tandems use an eccentric on the front bottom bracket to take up the chain slack and run the timing chain on the left side. This pretty well makes a real tandem crankset necessary because otherwise you'll have issues with the pedal threads.
re: tandemwily in pacifica
Sep 30, 2003 3:28 PM
I believe Chucks tandem frame has a EBB included and a 145mm rear end. It most likely takes V's or cantis but if not regular road brakes will work fine on tandems. Some of the best/most expensive tandems out there use road brakes over the canti or V's and they have a better feel since they do not use the adapters. I believe his tandem comes with a braze-on for a rear disc as well. This would take care of any overheating issue but I have been riding tandems for a long time and never came close to 70MPh and don't know where to find a 10 mile hill. Beside you would have to get up that hill first.
If you do not live in a hilly area you can use two regular crank sets. With a triple set on the rear you can then use the inside ring as a timing ring to the front set. This means you can get a set of tandem cranks for next to nothing if you don't care about the brand.

Some folks have built up his frames with great success. I have not heard any negatives about the tandems.

Willy in Pacifica
Tandem and disc brakesGeoCyclist
Sep 30, 2003 6:00 PM
If you are going to ride in the mountains, I would strongly recommend doing research on braking systems. Two years ago I looked at upgrading my tandem to disc brakes; as my drum brake was not working very well on steep (15%) hills. I live in Japan, and we have lots of steep hills. I went through two sets of V Brake pads in one riding season, and we don't get on the tandem that often (less than 1000 miles). I have since overhauled my hub brake and it works much better now. We have never hit 70 mph, but I've seen 90 kph with the hub brake on. Yes, it was not a fun experience smoking my V Brakes trying to get the speed down. The majority of bicycle disc brakes are not designed for use on a tandem. As tandem riders need to use a drag brake on steep hills. You can overheat a disc brake and warp the rotor, or overheat the disc brake fluid. Santana has done extensive testing of disc brakes. This information is available on the web.

As mentioned previously, there are some compatibility issues with regards to drive train components. I changed out my MTB front end for Ultegra Road group. This was an expensive exercise as you have to change both the stoker and captains timing rings. If you have access to a whole lot of spare parts you might be able to do this on the cheap. If you want a cheap set of MTB cranks, BB's, and chains for a tandem I could make you a deal!!!

Have fun building your bike!
Tandem and disc brakeswily in pacifica
Sep 30, 2003 8:59 PM
Disc brakes on tandems have been discussed in great deal on the tandem e-mail list I am on. As of now I believe the Avid cable disc is, or should be, tandem rated. Quite a few tandem builders have been putting them on their bikes and for 2004 Cannondale has spec'd thier road tandem with the discs front and rear. I am sure they would not have doen this without Avids approval. With two disc you should be able to get great braking on any hill. Of course there is always the chance of a heat problem but at least it will not effect the presesure in your tire and cause a tire blow-off. And anyone who is hesitant to decend a hill with two discs most likely would not put themselves in that situation without getting enough experience on thier tandem.

I have a shaved down drum on my Bilenky tandem but am hoping to have the guys at Sycip braze on a disc tab so I can take it off as well as my rear rim brake. The disc is not designed to be used as a drag brake but I should not have a problem as any team I am on will be considered a light team. Plus my former tandem only had V's front and rear and I manage just fine. It does take some experience to get used to decending with that much wieght and to be able to get it to stop when you need it.

Not sure what the compatibility issue would be to make you change the timing rings when you went to a road setup. The only issue with timing rings is that they need to be the same number of teeth on each ring. On off-road tandems you may want to go with smaller rings to get more clearence otherwise there should not be a reason to change the timing rings.
Tandem and disc brakesGeoCyclist
Oct 1, 2003 3:26 AM
As I mentioned in my earlier message; it all depends on where you ride your bike. As for disc brake use on tandem, I suggest researching the brake you intend to use, not that there are no brakes that will work. Two years ago Santana would only use the Formula disc; as it was the only brake that would pass their hill test. In the past two years I would hope the market had improved technically. The timing gear issue in changing between MTB and Ultegra has to do with the change in BB. Once you change the BB in the back, you have to change to a matching length BB in the front. I went from tapered to splined with the upgrade; therefore, requiring new cranks for the front. I agree there are inexpensive ways to get around some of these issues, but then you get what you pay for! My new drive train works flawlessly, but then I paid $$$ to achieve this. The best advise given in these threads was to buy a used bike that is the right fit for both captain and stoker.

Ride on X2
A caution with the AvidsTWD
Oct 1, 2003 12:10 PM
I haven't heard about whether or not Avid has rated their road disc brakes for tandem use.

What I do know, is that I wouldn't count on the Avid Discs on a long/steep downhill in the mountains on a tandem. They have lots of power, and no fluid to overheat, but they still aren't meant to be used as a drag brake.

I've been running their off-road mechanical discs on my mountain bike (virtually identical to the road version except the amount of cable pull they are desinged for). I've had problems with overheating them and loosing significant braking power on long/steep descents on my single MTB.

I did one particular descent on a 3 mile fire road descent that averaged at least a 20% grade (yes I do know how steep 20%, we dropped over 3,000 feet in 3 miles). The fire road had deep loose gravel, so traction was very minimal and not suitable for hard braking especially in the turns. So, I basically had to drag my Avid discs the whole way down to keep from going out of control.

They got super hot (I have a burn scar on my calf from accidentally brushing my leg on the caliper). I noticed some serious loss of power due to the heat gererated.
I know I've done some descents on my road tandem that would have gererated much more heat than that.

I'm sure they have enough stopping power, but really aren't meant to be used as drag brakes. Avid's road discs come with 160 mm rotors. I would consider using them if could upgrade to a larger rotor size (they have 185 and 203 mm rotors for their MTB discs) but I'm not sure if they make the correct adaptor to run the larger rotors on the road discs. The larger rotors will help dissipate the heat more quicly as well as give you lots more stopping power.

The best setup I have found for my tandem is running a set of Magura HS-66 hydraulic rim brakes and an arai drum brake operated off of a thumb shifter on the bar. The HS-66s have plenty of power, and I can set the drag brake on long descents to keep the speeds in check, without having to tire my hands with holding a lever the whole way down.
A caution with the Avidswily in pacifica
Oct 1, 2003 2:12 PM
Everyone who I have heard from that uses the road Avid discs on their tandem have had to buy the road disc and a separate 203mm rotor for the extra braking surface.

I also believe there is a big difference between riding down a long road downhill and a long off-road downhill. You are applying your discs off-road to keep your bike both under control and to keep it slow. On road you can run one of the disc to scrap off speed then alternate to the other disc to let the first cool down a bit. Plus since you are probabaly going faster on the road the cooling will be more efficent.

I have not heard anything but kudos from anyone using the 203 Avid discs as either a rear brake or as both fornt and rear disc.

Plus, you can always pull over if you are decending a really long downhill to check out the temp and let them cool down if needed.

Most of those that are going to discs, over the drum, are doing so to get rid of a couple of pounds and since they are not to be used as a drag they are being used as the only rear brake. Those that are a bit more conservative will stick with the drum.

Willy in Pacifica
re: Tandem disc brakescyclopathic
Oct 1, 2003 9:15 AM
Geo, the easiest option is to get disk is to get mechanical disk, Hayes or Avids. No problem with fluid overheaing, disks well ventilated/hard to warp. No cable-to-hydro adapters they work fine with road levers. Lotsa power but modulation is there. The ecomomical way to build disk rear wheel is to get 36-hole MTB disk rear hub (XT or Deore) and axle kit /if need 145mm spacing/. Way cheaper then buying tandem rear disk hub or wheel.
Oct 1, 2003 6:40 AM
I have a KHS entry level tandem. It has 26"x2" tires, V-brakes, a triple, rear suspension seatpost, and is pretty heavy. But, it works fine for the wife, kid, and me to putt around on. It only cost around $600, and I'll bet you'll spend far more than that building up one yourself.