Lennard Zinn: tire sealant corrosion, disc brake spoking patterns, and more.
Photo: Courtesy
I’m still being deluged with letters about CO2, and I promised to end it, so now I’m switching to letters about wheels. However, at the bottom, you’ll find one more CO2 letter addressing environmental points, which I think to be important and a duty to bring up.
On November 25 , I passed off a Shimano concern about rim corrosion due to tire sealants in tubeless tires with a quote from NoTubes. Apparently, I was too quick to do so, since I have since gotten these photos of wheel corrosion attributed to sealants. This damage is not covered under warranty.
Photo: courtesy
Shimano’s Devin Walton said, “The issue is the chemical make-up of some sealants. They tend to be very basic and thus quite corrosive to untreated metal. That’s why a person can have pretty positive results with newer wheels, but can experience issues once there are tool marks and other wear that penetrates the anodization. We have recommended against sealants in our wheels and some manufacturers of sealants have also worked on creating more neutral formulations that are less caustic to bare metal for those reasons.”
Photo: courtesy
So, I discussed this with two other sealant makers, one of chopped-fiber sealants and one of latex sealant, and I got the below responses:
Lennard,
There are many sealants trying to be Slime.
The Slime Super Duty is safe for all types of metal rims.
Joe Bowman
National Marketing Director
SLiME/Accessories Marketing, Inc.
Lennard,
The problem is not so frequent as the e-mail seems to suggest, but this might hold some truth as far as ‘first generation’ latex sealants are concerned (you can easily recognize those by the typical ammonia smell). Ammonia is used to stabilize natural latex and, although in a small concentration, it can harm both tires (depending on the rubber formulation) and rims in the long run.
See this link for natural latex and ammonia:
http://www.afet.or.th/english/product/latex/
Tire and wheel compatibility was one of our main concerns defining Caffélatex formula. We only use synthetic latex (much more stable) and we’ve been able to avoid any additive that could damage wheels or tires; we’re 100 percent rim and tire friendly.
Alberto De Gioannini
Founder, Effetto Mariposa
Dear Lennard,
I’m about to lace up a wheel with a disc hub and noticed that Chris King and Shimano disagree as to which spokes should be head/elbow out on the disc side.
Chris King instructions specify:
“The front ISO Disc should be laced 3-or-more-cross with the rotor (left) side pulling spokes (relative to braking direction) heads out/elbows in (when laced 3-cross). The final cross of the pulling spoke must be on the outside so that as braking force is applied, increased pulling spoke tension will pull the crossed spokes towards the center of the hub and away from the caliper. Lace the wheel symmetrically.”
Whereas Shimano’s manual recommends the opposite.
Chris King gives a reason for their decision, but Shimano gives none. Do you know the advantage of lacing a wheel as per Shimano’s instructions? What’s your take on the best way to lace a disc wheel?
Rob
Dear Rob,
I use the method recommended by Shimano, and I can explain that argument. The idea is that you want the pulling spokes coming to the outside of the hub flange (head in, elbow out) so that you have the widest pull angle to the rim.
Pulling spokes on a rear wheel that oppose the drive forces of the chain trail behind as the wheel rotates forward — a pulling spoke at the top of the hub flange would be pointed back, behind the bike.
However, pulling spokes opposing braking forces on a rotor point the opposite direction. Grab the top of the rotor and pull back on it, thus rotating the wheel the opposite direction of travel. This is the braking force direction your pulling spokes need to be opposing. So, a pulling spoke at the top of the hub flange opposing a disc brake points forward, ahead of the bike.
If you want to end up with the Shimano-recommended pattern, you can use the wheelbuilding chapter of Zinn and the Art of Mountain Bike Maintenance to build your wheel. It describes how to lace front and rear disc-brake wheels resulting in the heads of the pulling spokes on the inboard side of the hub flange. Front wheels have pulling spokes opposing the disc brake to the outside of the hub flange on both sides, while rear wheels have the pulling spokes opposing the disc brake to the outside on the left and the pulling spokes opposing the chain tension to the outside on the drive side.
Lennard
On December 23 and January 27, we discussed tubular glue removal from carbon rims using acetone. Here is a clear explanation why it cannot damage a carbon wheel:
Dear Lennard,
I spent a few years in polymer composites research and investigated different polymers throughout my PhD research. Acetone will have no effect on properly formulated and cured epoxy because it’s a cross-linked polymer. Allow me to explain that one.
Polymers begin as monomers, which are individual molecules. Linking monomers together builds long, chain-like molecules, i.e., polymers. Some monomers, however, can still react with other molecules after they’ve become part of a polymer. When this happens, additional molecules link up to the polymer’s sides. When polymers react with each other in this way, they become cross-linked.
Ideally, this would look like a collection of straight strings tying themselves into a net. In reality, it’s much messier and complex, but the idea is the same. The result is a very large tangled molecule that might absorb some solvent, but it can’t dissolve in it. Its shape is too rigid and the molecule is just too heavy.
James
CO2 greenhouse
Dear Lennard,
I’m amazed in the continuing discussion of CO2 canisters that I haven’t seen anybody bring up the environmental costs of canning air, transporting it and then tossing a hunk of metal that will never be recycled into the landfills, or the side of the road in the case of the particularly ignorant cyclist.
Think about it: you take air, which is free and all around us, and use electricity to pump it into metal containers, which had to be mined, smelted, formed, etc. Then you take these canisters and place them in a cardboard box made from trees and you put it in a shipping container and transport it across the ocean where it is unloaded and placed onto diesel trucks to be driven across the country to your bike store.
But it’s not even good air: it’s air that leaks out of your tires even faster. You are surrounded by air, free air, better air. All it takes is a pump and a few minutes of work to get it into your tire, where it holds longer than the CO2.
Cycling, as we all know, holds such a great promise for the environment. CO2 is a dark blot on that green sheen. We all know what the C in CO2 is.
Leave the CO2 to the mountain bike racer who can’t spare the seconds. The rest of you can carry a pump. I love my new Lezyne pressure drive — more reliable and probably lighter than CO2 canisters. It’s an endurance sport folks. Endure a few minutes of pumping.
Rick
Technical writer Lennard Zinn is a frame builder (
a former U.S. national team rider and author of numerous books on bikes and
bike maintenance including the pair of successful maintenance guides
“
“new”>Zinn and the Art of Mountain Bike Maintenance” – now available
also on
“new”>DVD, and “
and the Art of Road Bike Maintenance,” as well as “
and the Art of Triathlon Bikes” and “
Cycling Primer: Maintenance Tips and Skill Building for
Cyclists.”
Zinn’s regular column is devoted to addressing
readers’ technical questions about bikes, their care and feeding and how we
as riders can use them as comfortably and efficiently as possible. Readers
can send brief technical questions
appears here each Tuesday.
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