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Technical Q&A with Lennard Zinn – Wavy washers, CO2 and acetone

By Lennard Zinn

The Campagnolo 11 will work on a Madone. Just make sure you use the right washers.

The Campagnolo 11 will work on a Madone. Just make sure you use the right washers.

Photo: Campagnolo

Making it work

Dear Lennard,
There appears to very little clarity on how to fit a Super Record 11 speed crankset into a Madone 6.9.

I have both parts and while they appear to offer up without washers and extras I am concerned that I may damage both or either if this is not done correctly.

Dear Mark,
Campagnolo Ultra-Torque or Fulcrum Racing-Torq cranksets will fit right into your Madone bottom bracket shell without cups or retaining clips, but you have to insert a flat washer into each side under the bearings and a second wavy washer under the left bearing.

Are those bearings too tight?

Dear Lennard,
I just installed a set of brand new Shimano Dura-Ace 7850 SL wheels, and it seems to me that either the bearings are adjusted too tightly or there is some source of friction that is preventing the wheels (especially the rear) from rotating as freely as I’d expect.

In (admittedly poorly controlled) comparisons with other bikes’ wheels with the bike, these wheels do not spin as long, and seem to bind a bit as they slow down. I’m wondering if I need to adjust the bearings or if they just need to wear in a bit, or if you can provide any other insight.

Dear Dru,
Shimano assures me that all Shimano hubs come perfectly adjusted from the factory with zero play according to Shimano Quality Control standards. Indeed, that has been my experience. However, this is too tight to use. Wheels need to have extra play in the bearings, so that they just reach zero play at the rim when the quick release is fully tightened.

Bearings may never wear in as well, and significantly reduced bearing life if axles are not readjusted. The optimal set-up is to adjust for the specific QR pressure used by each rider.

So with cone wrenches, loosen your locknut, back out the bearing cone a quarter turn or so, and tighten the locknut against it again until you feel a little play in the axle. Then tighten it into your dropouts with the quick release, and feel for play at the rim. You can repeat this until, at the quick release tightness you use when riding, the play just barely goes away at the rim. This will be your optimal bearing adjustment.

Flying with CO2

Dear Lennard,
I read your great analysis
of CO2 leakage
and have a similar question: Why do the airlines insist you throw away your CO2 cartridges, even when in checked baggage? The aircraft pressurization system only pressurized to a cabin altitude of 6000 to 7000 feet and I’ve never had my cartridges explode at Lake Tahoe.

Dear Michael,
There is no way the cabin’s reduced pressure will cause those cartridges to explode. Even if you flew from sea level and up to 100,000 feet, they would not. In fact, the same goes with deflating the tires on your bike packed in the hold.

Air pressure at sea level is about one bar, which is 14.5psi. So if your tires were at 90psi at your sea level takeoff, the maximum pressure they would go up to from the air pressure change would be 104.5psi, which they should easily be able to take, if they are quality tires in good shape. That is way less than the pressure increase you’d see when leaving them in a hot car. And I would venture to guess that you often leave CO2 cartridges in a hot car and never even think about it, much less actually experience an explosion from it.

That is a totally nonsensical rule by the airlines, especially given that the lifejacket under every single seat has a CO2 cartridge on it to inflate it (by pulling the two tabs as the flight attendant demonstrates).

What’s in that cartridge?

Dear Lennard,
I found the article on why CO2 leaks out of butyl rubber tubes faster than air, very interesting.

However, a while back when searching for refills for my inflator I saw something I almost couldn’t believe, and I just went and checked it again to be sure.

Innovations makes a “big air” refill which is PROPANE, not CO2! Now, besides the obvious of this being really flammable, would there be any other advantages or disadvantages to filling your tubes with this?

Dear Dave,
When I was a kid, I used to wonder about the engine pumps you could get to blow up your spare tire on your car if it went flat. You ever see those? You removed a spark plug, screwed the hose into the spark plug, and started the engine. You stuck the air chuck on the other end of the hose onto your tire valve and blew up your car’s tire with the combustion mixture straight out of your engine cylinder!

As a 14-year-old, I remember being pretty frightened about this on a hot drive on a dirt road in an overloaded station wagon in Idaho. Given that we’d already blown a tire from the heat and pressure, driving on a spare tire full of the gas/air combustion mixture straight out of one of our cylinders did not seem like a good idea to me. But, I’m still here to tell the story, so there must be something I don’t understand about this. And I would guess the same goes for putting propane into a tire. I don’t know the answer, but I’ve used Big Air many times without problems, as have many of my friends.

Along similar lines, I just got some StayFill cartridges, which are supposed to never leak out of a tire. On this FAQ page, StayFill says, “STAYFILL is a proprietary gas blend that keeps bike tires inflated for over a year. The actual gas mixture is a trade secret. But we can tell you that STAYFILL’s molecules are 2-3 times larger than CO2 or air molecules. STAYFILL’s larger molecules do not pass through tire walls like CO2 or air molecules.”

So we won’t get to know what’s in that cartridge, but given the propane contents in Big Air, perhaps we are looking at a similar thing.

Carbon and acetone

Dear Lennard,
Regarding acetone use for cleaning glue off of carbon rims,acetone should be used with great caution on carbon fiber reinforced polymer (CFRP) components, since it can dissolve the epoxy matrix.

While cursory contact will normally be fine, soaking CFRP in acetone will damage the epoxy and possible lead to failure. Any damaged components should not be cleaned with acetone, since the liquid solvent could enter cracks or scratches in the clear coat (or holes leading to the inside of components!) and slowly plasticize the epoxy from within. Acetone should always be washed off with plenty of clean water.

Although less effective than some other methods, acetone digestion of epoxy matrix is a fairly common method of determining the volume fraction of CFRP laminates. Methanol is a much more appropriate solvent for cleaning reinforced epoxies.

Dear Tobias,
Actually, I have looked into this a lot in the past and would not have recommended it without having done so. Here are some responses to your assertion from three people who know more about carbon composites than I could ever hope to.

An answer from Calfee

That’s utter nonsense. Epoxies are rated in two standard tests: boiling in water and boiling in acetone. The rating calls out the amount of water or acetone absorbed. Epoxy does not dissolve in acetone. Acetone is a great solvent for uncured epoxy. But once it’s cured, acetone doesn’t hurt it.

The only problem with acetone as it relates to bikes is that it will dull paint and clear coats. Most bicycle parts are coated, sometimes with a satin or flat finish that looks like nude carbon. Acetone will change the glossiness (or lack thereof) and make you think it’s doing something to the epoxy. Alcohol is the strongest solvent you can use that will not affect paint.

We offer frames in a nude finish and offer to strip all coatings off other carbon frames. Then we treat it with a UV filtering protectant (303 Protectant). Acetone cleans off this Scotch-guard-like treatment and it would need to be re-done.

That’s more than you need to know about acetone!
Craig Calfee
Calfee Design

An answer from ADA

We’ve never had any problem with acetone, and it can only hurt the foam inside. No it does not dissolve our carbon matrix.
Cees Beers
Founder and president, ADA Wheels

An answer from Hed

I’m more of a wheel expert than a resin expert, but here is our experience: We have never soaked wheels in acetone but we have used it as a cleaner for 20 years and have never had a problem with resin degrading. I’m not worried about our use for two reasons: cleaning is a “cursory contact” and acetone is pretty volatile. A rag soaked in acetone only stays wet for about 30 seconds before the acetone completely evaporates. Second, acetone is fairly harmless. You can get it on your skin and not worry (though it does dry your hands out very quickly and very effectively), and vapors are not a problem in a decently ventilated area.

Methanol can cause blindness and death in relatively low doses and can be absorbed through the skin. I don’t dispute that soaking a carbon wheel in acetone might degrade the resin, but since we don’t soak the wheels, we’ll continue to use it.
Andy Tetmeyer
Hed Design

Technical writer Lennard Zinn is a frame builder (www.zinncycles.com), a former U.S. national team rider and author of numerous books on bikes and bike maintenance including the pair of successful maintenance guides “Zinn and the Art of Mountain Bike Maintenance” – now available also on DVD, 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.”

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 directly to Zinn. Zinn’s column appears here each Tuesday.