Tandem Cycling - OOP and Zipps
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I know this is Merlin's Co-Mo and as always I like to see what others are doing. Especially with similar framed bikes to ours.
So, out of curiosity, any reason why the OOP has the stoker leading. We have never tried this, but maybe should. What could be expected compared to stoker trailing a similar amount.
I like the look of those 808's. Are they something you had built or production stuff. Anyone else running 808's with comments about them other than cost?
05-08-10, 09:16 AM
From an Engineer's perspective, there is absolutely no difference between +90 and -90 OOP. Everything else would be a timing question, but as far as flex and tension on the bike, there is no difference between + and - in phase shift. Those zipps do look pretty awesome. I wonder how careful you need to be with a wheelset like that and a moderate team weight.
05-08-10, 01:50 PM
Zipp is one of my teams sponsors and I can give you their engineers opinion on the 808's and tandems. First off, Zipp will not officially build any tandem wheel and if you use it on a tandem it will void your warranty. If you want to use Zipp hoops you will have to buy them through an authorized Zipp distributor than have them built by a your own wheel builder. The 808 was the wheel that I originally wanted on our tandem as well. The Engineer at Zipp thought that the spoke angle on the 808 was too great and may cause an issue. He suggested that we use the 404 or the 505 for maximum strength.
Having said that I'm still thinking of having at least a rear 808 made up for my tandem. I'm not sure if the engineer was just being conservative or he was taking into account our size and how we race our bikes. I'm following Merlin's experience closely (whether he know's or not ;)) and want to see how his wheels hold up. All of the tandems on our RAAM team are running Zipp 404's and they work predictably great. This will be my second RAAM on my 404's and they have about 9000 miles on them (about 1/3 of them racing miles) so far and are holding up fantastic.
05-08-10, 02:09 PM
What sort of hubs are you guys using? 135mm spacing or tandem 145mm spacing? I *think* I found a way to make a 28 spoke hub work with 142.5 spacing using DT Swiss components, but have not ordered the axle yet. Bearing size/space should interchange based on the data I can find online. I'm sure I can make up the 1.25mm on each side with a shim or just use it as is. I'll follow up with a parts list once I make sure it works and is reliable.
I'm looking at a Reynolds SDV66 wheel for our tandem. I built up a 3x pattern on my race road bike with 24 spokes and so far it hasn't even needed truing after 8k miles. Since my stoker is only 100lbs and combined weight is less than 300 with gear, the spokes should be reliable. I'm not even worried about rim strength. I can't destroy mine.
I've tried searching, but didn't have much luck with actual component build up of wheels. I would try again with some keyword help. Thanks!
05-08-10, 03:57 PM
OOP: I'd like to com up with some theory of why the stoker should be slightly advanced. Truth is the slight OOP was the result of a lack of attention to detail, and an issue with a skipping timing belt (both of which have been corrected after the pic).
Zipps: They are essentially 808's. Specifically they are 520 clincher rims (the rims used for 808's) 24hole front, 28 rear (compared to 16/20 for stock 808's) built on White Industries Tandem Hubs with 145 mm rear spacing, and Sapim spokes.
We bought them from Precision Tandems. It's my understanding that they were built by Dave Walker at Paketa.
Homeyba is correct that Zipp does not reccomend this due to the angle of the spokes to the 145 hub, and it voids the warranty. In talking with the Zipp rep, the concern is that the spoke angle could crack the rim around the spoke holes.
We now have around 3000 miles on the wheels, and overall they've been great. Subjectively they feel fast, and give you that CF "whoosh whoosh" which I think helps as a placebo type effect. They're stiffer than our Rolfs, and the bike corners better with them as a result. We didn't intend to use them as everyday wheels, but they're fun to use, and tend to stay on the bike probably longer than they should after a race.
We recently did have a problem with the rear wheel. We broke two spokes on the same ride. Both non drive side, and both failed right at the Hub. When the first spoke broke, the wheel stayed true. After the next adjacent spoke non drive side broke, the wheel was out of true enough that we had to open the rear brake QR. but the wheel was fine riding the remaining 10 miles home. I think that says something about how strong and stiff the rims are. And close inspection of the rims shows no problems around the spoke holes.
I was concerned with 2 spokes breaking, but I'm thinking the second may have failed from the added stress after the first broke. We've got 200 or so miles on them with the new spokes without incident. If we break another, I'll rebuild the wheel.
Considering a team wieght of 340-350lbs, I think the wheels have performed admirably. If you can live with the reality that you may have to replace a rim at some point not under warranty I would consider them. If you consider them a long term investment that you'll ride everyday for man years, I'm not sure I'd bet on that.
The 808's have me curious again. I'm going to see if they will drill for 40 hole DT hubs and ask if they will handle disc brake forces.
I'm expecting a no on the disc application. But will find out. After that it's a money thing. Plus I'll need some kind of good "story" about faster speeds with minimal efforts like the racers that seem to just float by at warp speed.
Merlin, slipped belt or not, that bike is seriously tough.
If the 808's are not doable for any reason, any suggestions for deep profile rims that are disc worthy on standard hubs? I'm guessing Velocities, but maybe there are more.
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