Friday, April 20, 2012

Techie Tuesday: Mavic Open Pro - How Tough Are They?

It's been a little over 2 months since I crashed in the rain, ruining my custom built Mavic Open Pro wheel, laced with 32 DT Swiss Revolution spokes 2X to a Shimano Ultegra 6700 hub.

No wheel ever built would have withstood sliding 3-4 feet sideways at a 40 degree angle, at 15mph, into a notched utility cover slot. After rebuilding my wheel with a DT Swiss RR454 rim, with Revolution spokes laced 3X, I took a closer look at the OP, and think it stood up to a tremendous amount of damage with some remarkable results.
  1. None of the eyelets pulled through, despite tremendous damage to the rim
  2. The tire did not go flat, nor come off the bead
  3. None of the DT Swiss Revolution spokes broke
  4. None of the alloy nipples were stripped, with all the threading intact
While the advertised weight of the OP is 425 grams, it's measured weight is 440 grams, but even still, the RR465 is 465 grams, so the OPs are very light. I believe the 2012 OPs have lost 5 grams, weighing in at 435 grams now.

I went with the DT Swiss rim because I've had so many problems with SUP welds on my OPs. First, my custom-built Colorado Cyclist rear wheel's braking surface started to buckle right ahead of the SUP weld, and when they rebuilt it (at no charge) they were either vindictive about selecting a new rim, or I had very bad luck.

Without ever riding the replacement wheel, I took to to MadCat here in Sacramento and had Eddy inspect it for usability. As a result of photo consultations, and caliper measurements provided to Mavic, that wheel was rebuilt a 2nd time, again at no charge to me, as Mavic paid for everything. I am extremely happy with the OP wheel Eddy built for me. Even after sticking a heel into the drive-side spokes when I crashed, the spoke did not break, and Eddy charged me $0.87 to fix and true the wheel. Excellent customer service all around!

This front wheel jammed hard into the fork and front brake calipers, leaving some deep gouges on the inside of my fork, but, as you can see, the wheel held together, although just barely at the SUP weld. I think the rim strip was actually holding the SUP joint together, or at least, the small stress of removing it so I could unscrew each and every spoke to check for stripping, broke the SUP weld.
Very Egg-shaped, but still a cohesive object, and it held air for 3 weeks, until I carefully disassembled it.

Enormous stresses borne by this wheel are evident in the tearing of the Maxal aluminum alloy. Serial number front and center for the folks at Mavic, who I hope will have a look at this
Note the seperation of the sidewall from the rim here. About 1" (25mm) of seperation here was the extent of this mode of failure

Mavic's SUP weld plug. It looks like concrete, but I'm sure it's aluminum alloy of some sort. Note the "T-shaped" slot
The other, mating side of the SUP weld, with some kind of plastic alignment plug protruding. Note the massive amount of damage here. Somehow, it did NOT break all the way. Very, very impressive!

 So this brings me to some observations, and conclusions. First, all metal rims are going to have joints, so you can chose between sleeved joints and welded joints. Carbon rims have no joints. Advantage carbon. This does bring up an interesting option though - alloy rims with carbon joints. I'm thinking of something like an inch of ExoGrid structure.

Second, anyone that says DT Revolution spokes are weak, and break easily is lying, and I would encourage you to tell them they're speaking from ignorance if you read this claim, or hear it in person. Demand they show you proof, as I have done here.

Revolution spokes are so elastic they are virtually impossible to break. I bent one around the heel of my shoe, putting a 35mm indentation in it, and it still didn't break, and neither did even one of the spokes on this wheel, in spite of totally destroying the wheel and rim. Beyond that, the 300 stainless that most spokes are made of is so elastic it can stretch to nearly doulble it's original length before failing. Titanium spokes? Yes. Aluminum spokes? Absolutely! Butted stainles steel spokes? Never!

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