This ain't no LOW JACK!

NDS tension too low, non?

Zipp uses standard Sapim CX-Ray straight pull spokes. There was a "wheel stiffness" article that got posted recently talking about the different ways a wheel can be 'stiff'. Specifically, the difference between spoke-borne lateral stiffness and rim-borne lateral stiffness. Like, a shallow box rim with high spoke count will be technically stiff because of the spokes, but it may still deform significantly at the actual loading point (while you won't measure much if any deflection opposite the loading point, say at the seatstay). Versus a low-spoke-count deep dish carbon wheel where the rim is extremely stiff but spokes aren't contributing much to overall lateral stiffness... so any loading at one point will deflect the rim much more opposite the loading point.

Yes, that's my theory. Unfortunately there was a crash in between the build and the failure that might have contributed, but I had replaced all spokes that showed any visible damage from it.

I think this is an ever increasing problem. Flange spacing ain't what it used to be.

I say 135 O.L.D. for all! Better wheels for roadies and discs are welcome, too.

Most likely! Depending on which Powertap he used, it puts the rear wheel build into a much more unbalanced territory than the stock hub. Remember above I quoted the DS hub spacing of 19.5 for the current 188 rear zipp hub. The current generation powertap G3 has a DS flange spacing of 17.5. That's enough to make a big difference in NDS tension.

For instance, stock zipp 404 Firecrest would have a tension balance of: 59.6% (7.9deg NDS, 4.7deg DS), stock build of 2x NDS, Radial DS
Same rim built into a Powertap G3 would give a balance of: 49.5% (8.5deg NDS, 4.2deg DS), if you keep the radial DS, 2x NDS
Same rim built into a Powertap Pro would give a balance of: 52.7% (7.6deg NDS, 4deg DS), if you keep the radial DS, 2x NDS

Using the stock Zipp hub and lacing pattern, the tension ratio is VERY acceptable. Not so with the powertaps. So although the G3 would have a slightly worse tension ratio than the Pro, it will be a stiffer wheel thanks to the wider bracing angle... marginally less durable because of the more uneven tension perhaps. By my calculation, Stock Zipp would have a lateral stiffness of 8.19kgf per spoke, G3 hub build would be around 7.32, and Pro hub build around 6.98.

You also have the complication that although Cycleops doesn't prohibit building a wheel with this lacing pattern, they recommend going with 2X on both sides for such a build (they DO specifically prohibit doing any less than 2x on the NDS). Build your powertap wheels this way and the tension balance worsens to 46% (6.7kgf/spoke) on the G3 and 47% (6.2kgf/spoke stiffness) on the Pro.

I build all of my PT wheels 2X on both sides, 3X if it's 32H.

Hell has frozen over for me Lol. I was thinking about it last night and realized that I should probably use the same tire with this we'll set if I really want a good comparison to the other wheels I test rode.

http://i164.photobucket.com/albums/u...328_102922.jpg

Decent tire, ouch on the price.

I can't imagine you will be sorry. Truly a great tire. Just don't forget they are asymmetrical and have to be installed a certain way. See the side wall for the indicator arrow. (Forgive me if you already knew that.)

Always a good opportunity to stock up on consumables in the winter when they're cheap. I got a pair of Gatorskins for $74 and a pair of GP4000S for $81 from ProBikeKit in late November.

That's why it's good to have best friends that work at bike shops! I didn't pay any where near close to that

I'm blessed with good roads so I am able to run the Vittoria Open Corsa EVO CX -- picked up 4 this winter for $34 each.

:thumb:

It doesn't matter with road tires.

I did not know that. Thanks for the heads up.

Wait, so it does or does not matter?

It doesn't matter at all. The contact patch for road tires is really small. Tires stick to the ground due to the rubber compound, not the pretty pattern on the sidewalls.

Consider it purely cosmetic.

I imagine Continental put the arrow on to shut up all the people calling/e-mailing to ask which way to install the tire.

I still install the tires with the arrow pointing the "right" way but I'm uptight like that...

But cosmetics are vital to some posters...:innocent:

edit - just getting a funny dig in. I'd follow the arrows too.

Got it. Thanks

Yup lol

Okay, I can go along with that. Can't hurt to follow the manufacturer's recommendation though.

one of my OCD ticks as well.