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.

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Very Egg-shaped, but still a cohesive object, and it held air for 3 weeks, until I carefully disassembled it.

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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!

Techie Tuesday - Wheels & Wheels of Details

My spare rear wheel arrived at the local Performance Bike Shop - shipped free of charge from the online store - in good shape, but with a 100mm front skewer instead of a 130mm skewer. I walked around the store and picked up a few items, especially, a new pair of gloves, squeezing the spokes to relieve them, and then handed the wheel back to the mechanic to have it trued.

It was in pretty good shape, so I am very happy with the purchase, as the cost was a screaming deal at $118 - about half of $205, plus shipping, from Colorado Cyclist. In their defense, my CC wheels were custom built by hand with DT Swiss's Revolution, 14/17 super-butted spokes, so I expected to pay more for them. The PBS wheels use double butted 14/15 Wheelsmith spokes, which as you will see in the photos, have much more abrupt butts. Spokes with abrupt butts usually fail at the butt, if and when they fail.

As indicated a few posts back, the CC wheel has developed a serious flaw at the SUP weld, so the catalyst for buying the PBS wheel was as a spare I can use to keep riding while my CC wheel gets shipped back for a warranty inspection.

I took a lot of pics to get these, which I think are quite good, and highlight contrasts between these two wheel builds. I went through a lot of trouble to get some good shots of the manufacturer's trade-mark stamp on the spoke heads. Once you know what to look for, this makes identifying the spoke mfg quick and easy.

Without further adieu then...

 

Sorry there are no captions, but BlogSpot's captions currently screw up the HTML so badly that you lose the ability to click on the pics and get full-resolution click-throughs..

Pic #1: Note the prominent "W" stamped on the spoke head for Wheelsmith, the manufacturer. Also, if you look closely you will see the butt area quite distinctly about 30mm out from the spoke head. The transition is done in about 4-5mm.

You might also notice a characteristic of 3-cross spoking - that adjacent spokes are pulling in opposite directions and form an almost unbroken and unbent line from one side of the rim to the other. This arrangement limits stresses on the flange to those pulling along the curve of the flange, nearly eliminating forces pulling away from the flange directly towards the rim. (which is characteristic of radially spoked wheels)

Pic #2: Shows a close-up of the flange and spoke head.

Pic #3: Shows a shot along the drive-side of the wheel, with the halographic Mavic OpenPro decal in focus.

Pic #4: Shows the same shot, but with the Shimano Ultegra 6700 steel freehub body in focus. You can see the butting quite clearly on several of the spokes in this shot.

Pic #5: Shows the DT Swiss head stamp and the very tapered butting. It is very hard to see the butting, it is so gradual. It is easier to feel it, but you can see it somewhat here, and the butting is all over by about 20-25 mm from the head. The same is true on the nipple side, leaving almost the entire length of the Revolution spoke at a very thin 17 gauge.

Pic #6: Shows a close-up of the head stamp and flange.

Wheel Problems - Again

I bought the last Ultegra 6700 - Mavic OpenPro rear wheel Performance Bike Shop had in their warehouse yesterday for a simple reason - I need to send my custom built rear wheel back to Colorado Cyclist for a warranty inspection. It's showing signs of failure at the SUP weld joint, and I have no clue why. None of this stuff is made in heaven, so mfg defects do happen. Mavic is reportedly very good about standing behind their stuff, so I'm hopeful this turns out well.

There's an extra piece of aluminum laid on the inside of the rim, about the size of a wire bread-wrapper tie, for shoring up the weld area. You can see its "shadow" pretty well through the machined, once-smooth braking surface, in the bottom picture.

My hunch is the post-weld rim was bulging out, so the machining to make the braking surface smooth again cut away too much material, making the rim wall too thin. With 32 spokes pulling with 30 lbs of force, there's almost a half-ton of pressure trying to crush the rim - mashing the ends together at the weld.

The danger, aside from outright wheel failure, is the brake grabs at the point of the weld. This will tend to lock the rear wheel on a descent, resulting in a sideways-skid, and causing you to lose control. 
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On paper my 2 rear wheels will be almost identical, but I have heard the Performance wheel uses cheap spokes and nipples, and ships out of true. Good to have a neighbor with a pro wheel-truing setup who owes you favors! As long as it can stand in when I need a spare it's done its job.


If Colorado Cyclists does rebuild the wheel, especially on warranty, I am going to ask them to use DT 14/15 double butted spokes on the drive side. I love my DT Revolution 14/17 super-butted spokes, but they are a bit too flexy on the drive side at my weight and power, and I don't like asymmetrical flexing out back.

I also realized that any serious commitment to training, especially a 2X Century, requires enough spare gear to stick to a training program - and a spare set of wheels is #1 on any such list. As it was I got a killer deal on the Performance wheel, and didn't have to pay shipping as they shipped it to a local store. (tip: if a company has a physical store in your state they are required to collect state sales tax, BUT, they will almost always ship to that store for free if you ask, and most advertise they will do just that. The cost of shipping and tax are usually the same)

I need a new seat, and maybe seatpost too, as my seat just doesn't work for the TT position, and is too old and spongy to make a good 2x Century saddle. I will ride the seat the rest of the winter and keep an eye out for a deal on the Specialized Romin (the spelling has Caesar rolling in his grave, I'm sure), as spongy has a way of getting nice and hard in the cold of winter.

The linked review is pretty thorough, with lots of price and weight info, but I do wish every last reviewer would stop insisting that "The Romin has a cut-out section that runs the length of the saddle..." Clearly, from the picture, anyone can see it does NOT!

I had to make a trip to REI to exchange a pair of Novara Road Gel shorts (the best warm-weather chamois on earth) for a new pair, as the stitching that holds the chamois to the short was coming loose. It's times like these you really love that NQA return policy at REI! While there I looked at the new Shimano 6700 compact crank.

The entire area between the 34T and 50T is covered by a smooth piece of black, ABS plastic, so the chain has nowhere to go but between the gears. Sweet! I am very concerned though about those very, very thin teeth wearing well. The replacement cost of the outer ring is a whopping $277 street! OMFG! Not gear for 2X Century training rides - unless they start using ceramic coatings, as Middleburn has done.

A call has gone out for 2X Century training partners at our bike club. I am going to suggest regular face-2-face get-togethers, maybe with slide shows and such, because there are just so many questions to be answered.