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Technical Q&A with Lennard Zinn - Cranks, seatposts and a touch of solvent

Published: Oct. 18, 2005

Can I just have the new crank?
Dear Lennard,
I have an older Serotta Legend with 9 speed Dura-Ace and I wonderedif I can replace the crank set-up to the new stiffer 10 speed without compatibilityissues as I would like to leave the 9 speed rear end as is. Seems likeI remember Velo doing an article on this subject last year but I have forgottenthe particulars as to efficiency and effectiveness.
GeorgeDear George,
I have done it, and it works fine.
LennardLong legs and lots of climbing
Dear Lennard,
I'm 6 foot 4 with a 36-inch inseam and I prefer to run 180mm cranks. I also ride a lot of mountain passes (I'm lucky enough to have a work assignmentnear Nice, France for the next couple years). I prefer to ride a triple,since I am no longer inclined to ride a low gear of a 39x27 on 175-kilometerdays with 5000 meters of climbing.Is there any option out there for a 180mm crank with either tripleor compact rings?  Preferably with the new integrated BB spindles? The Dura-Ace 180mm is double only and 130mm pattern so compact is not anoption, the Ultegra triple is 175mm and shorter, none of the FSA modelsappear to have 180mm options.  I haven't looked at Campagnolo, butwould prefer to avoid old-school square spindles if at all possible. I've considered using an XT 180mm crankset, since FSA and others make thenecessary rings in a 104/64 pattern, but the chainline of the new integrated-BBXT cranks are fixed at 50mm, which is going to suck on a road bike.Do you have better suggestions for the long femur crowd?  Mightwe expect Shimano to come through with a 180mm Ultegra triple or Dura-Acetriple??
TomDear Tom,
There already is a Dura-Ace triple in 180mm length in both 9-speedand 10-speed versions. For that matter, Shimano makes all of its top-endroad and mountain cranks, namely Dura-Ace double and triple and XTR (tripleof course) in every 2.5mm increment from 165mm to 180mm. That doesn't necessarilymean that you can find them, though. Many distributors, and consequentlythe bike shops, choose to stock only 170 and 175mm in mountain cranks (ifeven that – often it is only 175mm), and an incomplete size run in theroad cranks as well.Shimano’s Service Plus system, however, allows any bike shop to getany of those lengths directly from Shimano. I use this service myself whenI cannot get the Shimano crank length I need for a customer from my regularShimano suppliers.Campagnolo makes up to 180mm size run as well, but only in Record doublealuminum crankarms. It only goes up to 175mm in carbon crankarms or triple(aluminum only, so far) crankarms.
LennardBack to the double
Dear Lennard,
I have a 2004 Trek 2100. It's got a 52/42/30 triple chainring thatI'd like to convert to a 53/39. I have been given conflicting advice onhow easy it will be to do the conversion. One shop told me that I'd neednew bottom brackets, front derailleur, cranks and the whole bit. Anothershop told me I could just get the new chainrings and then adjust the frontderailleur. Can you settle the argument for me by letting me know whatparts I'll have to change in order to do the conversion?
JeffDear Jeff,
To do it right, you would change the bottom bracket, front and rearderailleur, cranks – the whole enchilada. The chain could stay thesame, usually, and the cogs could too, as long as they did not exceed theallowable capacity of the rear derailleur. You should at least change thebottom bracket with the crank to get the right chainline, but it probablywould work acceptably with your old triple derailleurs.
LennardMore seatpost follow-up
Dear Readers,
I have received a ton of mail about carbon fiber seatposts, bikes,solvents, paint removers, etc. this week related to lastweek’s column. I will summarize a lot of them and give some broadanswers.First, paint remover is not paint thinner. Paint thinner, lacquerthinner, etc., is for thinning liquid paint or lacquer. Paint remover,or paint stripper, is for removing fully cured paint. Paint remover isusually gloppy stuff (as opposed to a watery liquid, like paint thinner),so it will stick on the painted surface and slowly soak in over time afterit is smeared on. It soon bubbles the paint, which does not come off asa liquid, but rather as globs and thick soup. This is what Craig Calfeewas talking about when he said that, “about the only common chemical thatwill hurt carbon fiber is paint remover (which attacks the resin betweenthe fibers).”As for Calfee’s statement that, “there are many solvents that will dulla nice paint job,” I have received a lot of questions about Simple Green,the Pedros degreasers, like Oranj Peelz or the green Bio-Cleaner, and othersolvents people use on their carbon bikes and whether they would dull thefinish.First off, in case it is not obvious, that is a paint job covering acarbon-fiber bike, fork, seatpost, handlebar, derailleur plate, or shoesole; it’s just that it is usually transparent. It's a clear coat. However,True Temper, is using an opaque paint on its lightest new forks in orderto not have to put on the top woven layer of carbon. That layer is oftenapplied for just looks under the clear coat since it lacks t the structuralcharacteristics of the less-attractive-but-stronger unidirectional layersunderneath. I imagine that we can expect to see more and more opaque paintjobs on carbon for this reason.Anyway, you know that there are some solvents that dull the finish ofyour painted bike, car or boat. It's no different with the clear coat overyour carbon parts. From personal experience, however, I know that usingchain lube as your chainstay cleaner will not dull it. Otherwise, I imaginethat something like Simple Green, if left on the bike, might, butI suspect that a quick wipe now and then would not. This is strong stuff,though. One SRAM representative told me at Interbike about how bike chainswere prone to cracking after being soaked in Simple Green for extendedperiods. You will have to experiment.Here is what Steve Swenson, Manager of Tech Support and Consumer Servicesfor Trek, LeMond, Klein & Gary Fisher says about it: “We do not recommendthe use of degreasers to clean frames; most are too harsh and will damagethe finish. Bike Lust or Lemon Pledge are recommended to clean frames.”Also, having lots of experience at having to fix up a paint job with,for instance, a fly stuck in it, or a scratch in the clear coat duringassembly of components, that automotive rubbing compound and even TurtleWax can be used to shine up a dull, scratched finish. Finally, ProGoldhad a new cleaner at Interbike specifically formulated for cleaning carbonfiber. I got a bottle of it, and it works beautifully as  a bike cleanerfor any type of frame and components as well.The other question that I got a lot of was whether recommendations thatapply to a carbon seatpost in an aluminum frame also apply to an aluminumseatpost in a carbon frame. The answer is yes, they do, providedthat the inside of the carbon seat tube is carbon and not a metal sleeve.
Lennard

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.