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Tandem Cycling A bicycle built for two. Want to find out more about this wonderful world of tandems? Check out this forum to talk with other tandem enthusiasts. Captains and stokers welcome!

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Old 01-03-10, 09:28 AM   #1
RacePhase
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All Custom Duratec Big Bang R9

Hi everybody - just wanted to introduce my all custom Duratec Big Bang R9 Tandem. Geometry designed by myself - frame manufatured in Czech. All components selected by myself. Comments are welcome.

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Old 01-03-10, 09:43 AM   #2
Dean V
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Great looking bike!
What is the frame material and distance between the bottom brackets?
Are those a tandem or solo bike wheel?
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Old 01-03-10, 09:55 AM   #3
RacePhase
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Frame Material is Aluminium. The BB distance is 710mm. Those wheels are a mix, trying to combine the best of stability, aerodynamics and durability. Its a 82mm deep 32 hole CF rim, laced to MTB disc brake hubs using DT competition spokes. Spokes are triple crossed on both wheels.
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Old 01-03-10, 10:33 AM   #4
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What did you do to the geometry to tweak what Duratec offers as standard fare (geometry spes attached).

Why disc brakes on what looks to be a racing bike, e.g., dual chain rings tight ratio cassette?

Do you have a second set of wheels? The Planet X wheelset could prove to be a bit of a handful in cross wind conditions, particularly the front... far moreso that the effect they have on a single bike; just something to think about.

A few too many decals for my tastes, but otherwise it looks to be a nice solid package. From all accounts, Duratec makes a solid, well-respected frame so it should serve you well.

What brand / model of tandem were you riding before this one and what made you go with the Duratec?
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File Type: jpg duratec.jpg (82.3 KB, 23 views)

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Old 01-03-10, 01:11 PM   #5
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What I changed was the sizing. The frame is measured in to be a 58/52. The effective top tube length is a bit shorter, and the seat and steering angle is a 73 degrees all over. Basically I wanted the front compartement to be similar to my single ride. The tweaks were just peanuts to spent, so it was no biggie at all. After all, Duratec offers the frame for different riding purposes as shown in the chart. I chose the frame desing which was meant to be a track frame an fitted it to my road purpose as i didnt like the road frames design a lot.
For the brakes I wanted something reliable - I didnt see any diadvantage fitting them. As I have sound experience with CF wheels on singles I didnt love the thought to brake down an tandem with a normal brake caliper. Maybe I am wrong with that - but I wanted to be sure. However, I am aware of the crosswind issues you mention. There is a second set of wheels being not as aero as the ones shown in the pic.
To be honest this is my first Tandem. I went with Duratec due to the pricing and the customizing options. The quality of craftsmanship is almost on Cannondale level. Considered Cannondale and even Calfee as well. But once you go for best value I guess there is none better than that. If it wasnt a Duratec, it might have been a Burley if I had had the opportunity to grab one.
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Old 01-03-10, 08:27 PM   #6
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Not many folks riding Euro tandems! Thanks for posting a photo.
Looks like a well-built machine.
Being a bit of minimalist, the profuse use of decals sort of take away from the actual frame.
Quite a bold step with those wheels for your first tandem . . . watch those crosswinds!
Pedal on TWOgether!
Rudy and Kay/zonatandem
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Old 01-03-10, 09:17 PM   #7
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I think all the decals is a bit of a European thing. I've seen a number of European bikes with the MFG name plastered all over them. My Colnago is the same way... That is a cool looking bike. What does it weigh?
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Old 01-04-10, 12:47 AM   #8
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Those wheels are a mix, trying to combine the best of stability, aerodynamics and durability. Its a 82mm deep 32 hole CF rim, laced to MTB disc brake hubs using DT competition spokes. Spokes are triple crossed on both wheels.
The frame's over-locknut-dimension then is 135 mm? What hubs are these?

The deep rim provides some extra stiffness. With the Planet X rims, how did you decide on 32 spokes, vs. say 28 or 36? Was 36 holes an option? Did you consider the lighter DT Aerolites?

Are the dual discs for mountainous riding, and/or to keep excess heat off the carbon rims?

Is that a Truvativ Touro square taper crank? Is that a tandem crank, or did you have to do some cross-over?
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Old 01-04-10, 01:44 AM   #9
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@zonatandem
The stickers are part of Duratecs customization program. I could choose from different designs. This was the one I liked most. I could have kept it a bit more decent, however I am happy with it.

@ Homeyba
Didn’t weight the bike yet – will do the next couple of days. Gonna post the weight here then.

@Ritterview
Right, the dropout space is 135mm. The hubs are American Classic MTB disc brake hubs. The time I purchased the rims they were available at 32 holes max. However, there was the opportunity to get any holecount drilled into a new rim. This is no option anymore as far as I know, due to a change in distribution. As we are a rather light team I decided to go with the 32 holed rim. As you said, the deep rim adds some extra stiffness, just as the hubs do, having high flanges. I considered lighter spokes as well, but returned to conventional one due to the fact that Aerolites are not available at the length needed for the wheel. DT offers as service to provide spokes in non stock sizes for a certain price – I just didn’t want to spend that much extra money for the wheels.
For the discs – both of the considerations you mentioned fell into scope. As we live in a mountainous area I didn’t love the thought to stop the bike with just two conventional brake calipers. Additionally this keeps the stress away from the rims braking surface.
The crank is a Truvativ Elita Tandem crankset. It has no square taper, but is a “bolt through” GXP bottom braket.
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Old 01-04-10, 12:13 PM   #10
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TandemGeek, do deep rim wheels affect a tandem in a crosswind more than a single? I have never ridden them, but had thought that the extra mass and wheelbase of a tandem would make it less of a problem. I am interested to know as I was thinking of getting them for our bike at some stage.
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Old 01-04-10, 12:31 PM   #11
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Deep dish wheels have the same affect on handling in a crosswind no matter if you are on a single or tandem. If there is a chance of a strong crosswind, the front aero wheel comes off. The rear one dosn't matter too much.
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Old 01-04-10, 01:29 PM   #12
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My admittedly subjective perception is that deep dish wheels are easier to deal with on the tandem because the longer wheelbase and and greater weight tend to mitigate the effect of crosswinds.

To me riding my single with Zipp 404's in a crosswind is about comparable to riding the Tandem with 808's.

Only time, its felt sketchy at all was doing a TT with aerobars (that were slipping) and the 808's in a very strong crosswind.
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Old 01-04-10, 06:22 PM   #13
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TandemGeek, do deep rim wheels affect a tandem in a crosswind more than a single?
It's all relative and proportional.

The tandem's weight and wheelbase do tend to mitigate some of the wind on wheel issues, but just as you find with single bikes the size of the rider(s) and the amount wheel surface area comes into play as well. Moreover, a steady crosswind isn't nearly as bad as gusty winds since the latter will usually bring stoker lag into effect.

For example, in a steady crosswind you simply settle into a slight lean towards the wind with a little countersteer and deal with it. However, in gusty conditions front wheel buffeting by the wind will upset the steering and that front wheel shimmy will ripple back and influence the stoker's movements in response to the unintended steering inputs as well as additional steering inputs caused by the captain caught in the middle making corrections to both... and so it goes so long as the front wheel is being influenced by wind gusts.

So, my cautionary note spoke more to the gusty wind conditions and that stoker lag effect. If a captain has had to deal with a wobbly stoker or has a very experienced stoker who know hows to keep their weight centered, then it's even less of an issue. Hence, someone like Merlin & his beloved may not be as bothered as a lighter weight team with a less experienced captain and/or stoker.

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Old 01-11-10, 02:15 PM   #14
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Promised to post the weight here: Its about 15.3 kg as pictured. Wish I could have got lighter by 1 kg, but there is very little weight saving potential left. Nevertheless the bike should be reliable in the first spot.
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Old 01-12-10, 09:45 AM   #15
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Promised to post the weight here: Its about 15.3 kg as pictured. Wish I could have got lighter by 1 kg, but there is very little weight saving potential left.
15.3 kilogram = 33.73 pound
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Old 01-12-10, 11:07 AM   #16
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That is a great looking bike and the weight is attractive. Has that bike been set up for you and your stoker? The stoker stem does looks short. Of course you will be very aero
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Old 01-12-10, 01:12 PM   #17
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Well, a sort of. From the geometrical point of view I tried to adapt the measures of our singles with some little tweaks, which has worked out well. The saddles are not mounted in their final positions in the picture. The captains saddle will be scooped forward a bit, resulting in a less radical look. But we will be very aero anyway, yes ;O).
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