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Technical FAQ: Rearward cleat positioning, wheel lifespan and corrosion

  • By Lennard Zinn
  • Published Aug. 14, 2012
The Speedplay cleat extender base plates on my shoes move my cleats back about 14mm from maximum rearward position with standard cleat mounting. You can see that the pedal will be positioned considerably behind the ball of the foot. Photo: Lennard Zinn | VeloNews.com

Editor’s Note: Lennard Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn.

Dear Lennard,
You recently wrote about Speedplay cleat extender base plates allowing for a more rearward placement of your cleats. What is the advantage of moving cleats closer to one’s heels? Is it something you would generally recommend for recreational cyclists?

How would moving cleats backwards impact seat position? What are the procedures for repositioning one’s seat?

If you have previously answered these questions, or if there are good web resources regarding this matter, I would appreciate it you could direct me to them.
— Patrick

Dear Patrick,
I actually have come to believe that the rearward cleat mounting offered by those Speedplay cleat extender base plates and shown in the photo is a good idea for many cyclists. For me personally, the biggest reason I do it is to alleviate Morton’s Neuroma pain between my metatarsals. By moving the contact point with the pedal back, the pressure of pedaling in a stiff-soled shoe is distributed broadly over the sole, rather than concentrated under the metatarsals, as with ball-of-the-foot cleat positioning. It makes a considerable difference for me. On MTB shoes, I am able to use the rear set of mounting holes and slide the cleat-mounting plate as far back as possible, and as long as I have carbon-soled shoes I can pedal hard all day and still be able to walk afterwards without pain. I am committed to avoiding surgery for this, and this is one of many things I do to keep it in check.

For riders with big feet, Andy Pruitt has long recommended moving the cleat back to limit the length of the lever from the heel to the cleat that the calf muscles have to control. And after experimenting with midfoot-cleat mounting on Biomac shoes as well as on some custom D2 shoes with two sets of 3-hole mounts, I think I’m able to generate more power with the pedal further back toward my heel. I like the amount of rearward cleat offset of the Speedplay plates, whereas I find the mid-foot cleat mounting to feel unstable when out of the saddle and to be totally unusable for cyclocross for that reason and for toe clearance with the ground and the front tire. So I’m happy with my MTB-shoe cleat position as far back as allowable without any special drilling, though I have considered machining the two slots in the sole a bit longer toward the back.
― Lennard

Dear Lennard,
I am the original owner of a very lightly used set of first- or second-generation Mavic Cosmic Carbone clinchers. They are 16-hole F/R with polished hubs, purchased in 1999. In their youth they only came out on race day. They have been hanging in wheel bags for the last five years, unused. Total mileage is definitely under 2,000. I weigh 180 pounds and have been easy on equipment.

Are these still OK to ride?  Is the lifespan on a race wheel based on chronological age, miles ridden, or both?  Am I risking life and limb, or worse — Fred status — by riding these in public? If so, any recommendations?
— John

Dear John,
Fatigue life is generally related to the number of stress cycles (miles ridden, in your words), not to its chronological age. I’m sure those wheels are fine to ride.
― Lennard

Dear Lennard
As a convert to tubeless about three years ago, I read about the corrosion issue with real interest, and your response was basically, shit happens. I wanted you to know that, while maybe lame, it might be the only answer why one wheel corrodes and one doesn’t. I also drive a 2010 Ducati MS1200 (in addition to my pedal-powered Seven!), and after the first year one of the aluminum valve stems had corroded so badly — on the inside of the rim and totally out of view — that it let all the air out of the back tire. The rim was fine; it was the part of the stem that sealed against the rim that had totally corroded to a white powder. There isn’t any sealant in those tires and the front was perfect. Who knows why? Some weird electrolysis? Spit from the guy that mounted the tire? Who knows? Another mystery. By the way, I’m running Stan’s with Mavic Ksyriums too (on the Seven J), with no issues yet after three years. Thanks again for the insights.
— Robert

Dear Lennard,
I just read your article on sealant corrosion of aluminum road rims. I too have been a victim of this. I recently purchased a set of Shimano WH 7900 C24 TL wheels, which I’ve been running with Stan’s sealant for three months. Sure enough, when the time came to replace my tires, the clear anodized coating had been eaten through in many places in both the front and rear wheels, and the aluminum is showing signs of corrosion. I’ve also seen some forum photos of others who have experienced this with this particular wheelset. Interestingly, I have a set of WH 7850 SL wheels that I’ve run tubeless with Stan’s sealant for two-plus years without issue. The only difference I can see is that the 7850 wheels have a hard black anodized coating in the rim interior, where the 7900s don’t.

So, the $1200 question: Are these still safe to ride (assuming that I start running them with conventional tires/tubes)? It’d be a real shame if I had to chuck these wheels.
— Dave

Dear Dave,
There’s no way I can answer that question at this distance. Sorry. I don’t know who to suggest to evaluate the safety of your rim — maybe Shimano?

In my experience with getting cranks anodized by different companies I’ve certainly found that different anodized coatings differ in susceptibility to corrosion. I, too, have a set of WH 7850 that I’ve run with Stan’s and Caffélatex for many years now with no corrosion issues.
― Lennard

Dear Lennard,
In reading about the corrosion problem with wheels, two thoughts come to mind:

1. Galvanic corrosion is caused when dissimilar metals are in contact in the presence of an electrolyte. Most valves are brass, which is 0.5 volts different than aluminum on the anodic index. If there is any electrolyte (salty water, sweat, etc.) introduced, there will be electrochemically driven corrosion at that spot. Is it possible that a small amount of sealant is mixing with water to make an electrolyte near the valve hole? Of course, many other contaminants can contribute to the electrolyte, including road salt and sweat. Could the sealant be trapping a small amount of water/electrolyte at the point where the two metals are in contact? This problem could also arise at stainless steel spoke nipples since stainless and aluminum are about 0.4 volts apart.

2. If you seal a volume of air at room temperature and then cool it, condensation will form. You can prove this to yourself by putting a transparent soda bottle, empty and sealed tight, into a refrigerator. If there are small sealed air pockets between the dried sealant and the rim there will be condensation on the rim at that spot if the rim is cooled. If there are any flaws in the anodizing, or any corrosive element (sweat?) present, it will produce small spots of corrosion here and there, which was described in your article.
— Peter

Dear Peter,
Given the condensation you mention, the fact that the sealants are generally water-soluble, the fact that Hutchinson advises mounting the tires with water, that the O-ring around the valve may not be water-tight, and that when you ride through a puddle, water can get into the center of most rims around the spoke holes and through the rim drain hole, it’s easy to imagine water getting in around the valve stem.

By the way, stainless spokes are standard, but I’ve never heard of stainless nipples. Spoke nipples are generally either chromed brass or aluminum. The rim eyelets may by stainless…
― Lennard

Dear Lennard,
I have dealt with numerous instances of rim corrosion on non-tubeless rims, and I think there is a similar mechanism at work with Lindsey’s Shamal.

The valve-rim area of a wheel must deal with a few unfortunate circumstances. It is foremost an area where two metals of differing galvanic potentials are in very close proximity. And while most of the rim is anodized, helping to prevent both crack propagation and corrosion, the hole drilled in the rim for the valve stem is usually done after this process and, thus, presents an unprotected aluminum surface. It is also one of the gaps that the latex must fill to provide an airtight seal.

The tubed wheels I have seen corrode and crack in this area do so because water and, in winter, salt accumulate on the valve stem before being pushed down the stem into the stem hole through centrifugal force. In this area the liquid acts as a perfect medium for conducting electrons from the aluminum to the brass, corroding the rim. My guess is that the latex (and any water that gets in that area from the outside) is acting in much the same fashion, allowing corrosion between that sliver of exposed aluminum and the valve stem.
— Andrew

Dear Lennard,
Any suggestions on cleaning dried Stan’s out of my D/A Road Tubeless rims? Removing the worn-out tires revealed a mess of the stuff stuck to the rim. I could scrape it with my fingernail and get a most of it, but I’m looking for a faster, more efficient, and more comprehensive method. Any solvent I should or should not try? The rim is aluminum, so I can’t think of any solvents that would be a problem.
— Ben

Dear Ben,
I find that the pink Finish Line bike cleaner and the ProGold Bike Wash both clean up sealant in a jiffy while being very mild solvents with no odor.
― Lennard

Dear Lennard,
I read, with interest, the recent posts about rim corrosion with tubeless wheels, specifically, the question of using abusive chemicals to clean wheels. Having ridden for many years and having dealt with residual glue from sew-ups (tubulars), I realize much of the info out there leads many to turn to the use of chemicals to clean brake surfaces and now residual sealant on clinchers.

Let’s try something new! I’ve found a Mr. Clean Magic Eraser does an awesome job of removing residual grime and pad remnants from braking surfaces as well as sealant from inside the rim, all without introducing a harsh chemical or an abrasive surface that will remove layers of your rim or damage the finish. Plus, you can clean your braking surface regularly without having to worry about damage to your tire’s sidewall.
— Stacey

Dear Stacey,
I love those Mr. Clean Magic Erasers! I do find them to be quite magical. I’ve got to try this with them.
― Lennard

Comment regarding British helmets:
Dear Lennard,
Smooth is often more aero, but not always. Note the turbulator triangles on the downtube of Pinarello TT frames (similar have been used on aircraft wings), dimples on some helmets and wheels, etc. Adding small amounts of turbulence in the boundary layer can decrease the amount of gross turbulence and associated drag behind objects. I agree with your opinion that it’s highly unlikely Sky and Kask haven’t tested those helmets and have data substantiating a reduction in drag.

As for cooling, take a look at the evolution of cooling and fairings for aircraft engines. Early on it was just finned cylinders hanging out in the breeze. NACA (early NASA) cowlings were added around radial engines to reduce drag and improve cooling.  Modern reciprocating engine-powered aircraft have very small air inlets and close cowled engines with baffling that restricts the airflow to a small gap right around each cylinder. This provides the greatest cooling with the least drag. The new prototype Giro road helmets and Specialized’s new aero helmet follow this trend.

It’s only the air passing immediately adjacent to and contacting the scalp that does any cooling.
— Lou

FILED UNDER: Bikes and Tech / Technical FAQ TAGS: /

Lennard Zinn

Lennard Zinn

Our longtime technical writer joined VeloNews in 1987. He is also a framebuilder, a former U.S. National Team rider, and author of many bicycle books, including Zinn and the Art of Mountain Bike Maintenance and Zinn and the Art of Road Bike Maintenance, as well as Zinn and the Art of Triathlon Bikes and Zinn's Cycling Primer: Maintenance Tips and Skill Building for Cyclists. He holds a Bachelor’s degree in physics from Colorado College. Readers can send brief technical questions to Ask LZ.

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