Technical Q&A with Lennard Zinn – That hideous sound
Screeeeeetch!Dear Lennard,I have a brand new Santa Cruz Blur equipped with Avid Juicy 7 discs. After a few rides in dry weather where the brakes performed flawlessly and silently, I rode the bike in the rain. I almost had to abandon braking altogether and just drag my feet to stop as the squealing sound was so loud it was shaking out my fillings. Since then, even in dry weather, the brakes continue to squeal on and off, and frankly I am afraid to use them in the wet again. The brakes are properly installed and bled. Did I not break them in long enough (three rides of easy road riding with
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By Lennard Zinn
I have a brand new Santa Cruz Blur equipped with Avid Juicy 7 discs. After a few rides in dry weather where the brakes performed flawlessly and silently, I rode the bike in the rain. I almost had to abandon braking altogether and just drag my feet to stop as the squealing sound was so loud it was shaking out my fillings. Since then, even in dry weather, the brakes continue to squeal on and off, and frankly I am afraid to use them in the wet again. The brakes are properly installed and bled.
Did I not break them in long enough (three rides of easy road riding with no hard braking)? Is this normal for Avids?
No, it is not normal for Avids, as I have Juicy 7s on one of my bikes and I have never encountered that problem. But here is what Avid has to say about it.
LennardAnswer from Avid
While this is not normal for our disc brakes it can happen, although it almost always goes away once things have dried out. We have experienced noise from different soil types too. I am not sure where this rider lives but that may be a factor too. I would clean the rotor with alcohol. If he continues to have issues he should contact our dealer service group 1-800-346-2928.
I have recently read an article on this very topic from Delphi, the huge supplier of automotive parts, including brake systems. This is relevant insomuch as even a company with massive resources struggles with brake squeal and in some respects they have fewer variables to deal with. Car brake systems are made for a dedicated car or series of cars. They know what wheels, mounting brackets and hardware that will be used.On mountain bikes we have very little control over what hubs and frames will be used and what any given combination may result in.
Currently all disc brakes suffer from squealing at some time or another, caused by many variables. We are working on a compound that will run quieter in the wet unfortunately one of the trade offs is that it does not last as long.
Every carbon frame I see advertised says it’s made from “high-modulus” carbon. One even says it uses “super-high-modulus” carbon. What does “modulus” mean? What does the industry do with all the low-modulus carbon?
JackAnswer from Easton
Your question on modulus in composites, the answer applies to materials in general. Modulus (or more specifically Young’s Modulus) is the term used to describe a material’s ability to deform under the application of load. If a material deforms very little, the Modulus is thought, in a relative sense, to be high. Aluminum has a modulus of 10msi, Titanium’s modulus is 15msi and Steel is 30msi. As you can see aluminum is 1/3rd as stiff as steel so this is why aluminum frames have to be built using large diameter tubing to be competitive with the stiffness of steel frames. This is the only way to get the stiffness you need to make a nice riding bike using aluminum tubes.In composites, the term modulus holds the same meaning. The modulus is a relative indication of the stiffness of the particular fiber or component. This is an often-misused term in the context of your question. Sometimes manufactures will use a very small amount of high modulus fibers mixed in with the standard modulus fibers and call the unit a high modulus unit.In carbon fiber, there are numerous different moduli available as follows: Type Modulus (msi)
Standard (S) -32 to 34Intermediate (IM) – 42 to 44High (HM) – 50 to 62Very High (VHM) – 100 to 130
The trade-off between the different modulus is the toughness and price. The higher you go in modulus the more brittle the material becomes. It is rarely justifiable to use 100 percent Intermediate or High modulus material in sporting goods, especially bicycle frames and components. Bicycle components benefit from longer fatigue life and greater toughness. We can design for stiffness by engineering larger diameter tubes and optimized orientation of the fibers, i.e. what we call the laminate schedule. The final result being a high performance affordable composite structural component. Finally, directly to your question, the industry in general uses approximately 95 percent standard modulus fiber, 4 percent intermediate and 1 percent high to very high modulus fibers.
Vice President- Bicycle Products
Making the switch
I am debating on changing my 2005 Campagnolo Chorus (double) crankset for the FSA Carbon Team pro (double). The question relates to Q-factor. While I believe the arms themselves have about the same profile, will using the FSAs with an ISIS bottom bracket put my feet wider apart? I don’t want this and don’t want to goof up a knee. I’ve been riding the Campy cranksets for about 10 years.
Well, you have to get the right length ISIS spindle for that crank. They come in 108mm, 113mm, and 118mm, before they get really long for the DH crowd. Should be no problem to get the same Q-factor.
More on shimmy
I got a lot of responses this week about shimmy issues, many of which were wondering how to avoid it. Again, I have rarely seen a bike with bad shimmy lose it by changing the fork or the wheels, but it always affects the speed at which it occurs, so those are worth a try; I included a few letters I got about such cases. And, I did forget to mention about pitted headsets and included a letter about that today as well. To avoid shimmy from the get-go, rather than fill this column up on this one issue, you can go here to see what I do to avoid it when building a frame. And below are a few of the other responses I felt I could fit in here.
I just read your Technical Q&A regarding the guy with the guy with the Litespeed that had shimmying issues. A riding buddy of mine had the same shimmy issues with his Litespeed Tuscany last summer, also at 24mph or so. Litespeed gave him a new frame, which did no good and finally, as a last resort, replaced his beefy-looking Real Design fork with a Reynolds and that did the trick. During the whole transaction it was clear to my friend from the comments of the tech guys that he was the umpteenth guy with the shimmy issue on that model. Litespeed was good about solving my friend’s problem but one wonders if a recall of those forks might have been more appropriate.
I have a Litespeed Sabre. I put a Reynolds Ouzo all carbon fork (their top-of-the-line model) and it would shimmy at speeds over 37mph. Obviously, going downhill. The fork broke (Not the fork’s fault. A car ran over it) and I replaced it with another carbon fork with an aluminum steerer tube. Now I can go downhill at up to 50mph and no shimmy. Both forks were 43mm rake.
Re shimmy, I used to have it no-hands at above 30mph, not a big problem. I switched to some lightweight wheels (Neuvation) from conventional 32-hole Open Pro’s and the speed of the no-hands shimmy dropped to the low 20’s. Everything affects the resonant frequency. Like you, I’m tall and ride a big bike, a Spectrum Super Ti with a Wound Up fork. The good news is that neither incidence is severe enough to worry about.
I had that shimmy problem because of a headset. The bearings had dug into the races so the wheel wanted to stay centered. Took all the fun out of any descents until I replaced it.
More on Simple Green
I was flooded with email about chains and Simple Green and related issues this week. I am running two of them. Also, in answer to many of you who asked about this with many chain brands, you can indeed use other master links of the correct width on chains not equipped with them originally.
I used to use Simple Green to clean my Litespeed titanium and Trek OCLV carbon fiber framed bikes, both outfitted with Shimano Dura Ace components. I used Simple Green both in solution with water and in full strength to clean frames and components. Simple Green corroded certain of the Dura-Ace components, and to varying degrees. The worst effect was it severely pitted the chainrings and actually caused the chainrings to delaminate. To a lesser destruction, it discolored the front derailleur cage. Furthermore, these problems occurred from the limited exposure during the time I was manually cleaning the parts, not from long term soaking of parts.
I’m not so sure it’s the Simple Green… I recently broke two chains in two days with not a single drop of Simple Green involved. I rotate two Wippermann (sometimes stainless, sometimes not) 10-speed chains, cleaning them with a citrus degreaser (usually Pedro’s) and lubricating them by immersing the chain in melted paraffin, which I break off after cooling overnight. It lubricates the chain well, and doesn’t attract crud to my chain and the rest of the drive train. I normally swap the chain out about every 200 miles (1 week); if I exceed 200 miles or hear any squeaking before rotating/re-lubing the chain (rarely) I sometimes lube the chain with White Lightening. Using a Wippermann ConneX link makes this relatively easy, since I can take the chain off easily for cleaning. I began experimenting with Wippermann chains after getting extremely poor mileage out of Campy 10-speed chains (I was getting between 1200 and 1500 miles out of Campy chains, if I exceeded that I would get cog wear and chain slip).I am a big rider, 6 foot 4 and 200 pounds, and ride relatively hard with lots of climbing. I have consistently gotten about 1800-2000 miles each out of the Wippermann chains with no appreciable wear on the cogs. I decided to try and get a few more miles out of my collection of 2000-mile chains, and the first chain I took out of retirement (stored for a few months in a box in the garage) broke on the first ride. I tried another with the same results – it also broke the first time out. Luckily I carry a spare ConneX link with me and it saved both rides, but after that I chucked my collection of 2000-mile chains. They were not cleaned with Simple Green or anything else before storage, just put back in the box and on the shelf. I re-lubed them with paraffin before using them again; they weren’t lubed prior to storage.
Technical writer Lennard Zinn is a frame builder (www.zinncycles.com), a former U.S. national team rider and author of several books on bikes and bike maintenance including the pair of successful maintenance guides “ Zinn & the Art of Mountain Bike Maintenance” and “Zinn & the Art of Road Bike Maintenance.”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.