Gear

Technical Q&A with Lennard Zinn – Fork fit; trimming carbon and more chain wear

Hi Lennard,I have an opportunity to buy a new frame (steel with carbon fiber rearstays) that has a 1-1/8-inch head tube for an integrated head set. A coupleof years ago I bought a 1-inch threadless carbon fiber fork -- with steelsteerer tube -- that I'd like to use rather than having to buy an 1-1/8-inchfork.I have three questions:1. Is there a product (headset or adapter) on the market that fits 1-inch forks to a 1-1/8-inch frame?2. Are there any shims that can be used with a 1-1/8-inch head setto fit 1-inch forks?3. Do you have any other suggestions or do I have to buy a 1-1/8-inch

By Lennard Zinn

Hi Lennard,
I have an opportunity to buy a new frame (steel with carbon fiber rearstays) that has a 1-1/8-inch head tube for an integrated head set. A coupleof years ago I bought a 1-inch threadless carbon fiber fork — with steelsteerer tube — that I’d like to use rather than having to buy an 1-1/8-inchfork.

I have three questions:1. Is there a product (headset or adapter) on the market that fits 1-inch forks to a 1-1/8-inch frame?2. Are there any shims that can be used with a 1-1/8-inch head setto fit 1-inch forks?3. Do you have any other suggestions or do I have to buy a 1-1/8-inch fork?CliffDear Cliff,
You can use a Campagnolo Hiddenset, which can accept either size offork inside an integrated head tube. However, the head tube needs to conformto the specs outlined in the two documents I am posting here.
Hiddensetspec sheet No. 1
Hiddensetspec sheet No. 2
LennardToo much of a good thing?
Dear Lennard,
Is it safe to cut carbon seatposts? I only need a post length of 200mm,most seatposts are 250mm or longer.
Thanks,
BradDear Brad,
As long as you cut it like you would a carbon steering tube, thereis no problem. That means cutting in from the opposite side to meet yourcut rather than going all the way through in one direction, which can delaminatethe outer carbon layer where the hacksaw comes through.
LennardA note on the subject from True Temper:

The Alpha Q Pro seatpost is just as easy to cut as a fork steerer.The thickness and materials are similar. Use a fine tooth hack saw or anabrasive cutoff disc such as is available for the dremel tool.The weight trimmed is 9 grams per inch for the Alpha Q seat post. Cuttingthe size down 50 mm will save about to 18 grams. For you weight freakstrying to save every gram by cutting your post (okay, I’m guilty myself)check out the new Alpha Q Prolite at 130 grams for the 250mm size. TheProlite post is tougher to cut because I’ve added a woven Kevlar/carbonouter layer, which is much more abrasion resistant.
It will cut but it will take just a little more time. The weight savedis 7.5 grams per inch for the Prolite.The seatposts I’ve tested from competitors are in the 9-11 gram perinch range, and cut just as easily as the Alpha Q Pro.
Bert Hull
Product manager, Performance Sports
True Temper Sports, Inc.

Working life?
Dear Lennard,
I have heard that magnesium components have a life of about one year.Is this an old wives tale making these components practical for a professionalracer only? Would the magnesium frames have a similar life? I thought youhad mentioned this in one of your articles but I may be mistaken.
Brad LesterDear Brad,
I can’t imagine that this is true. I have been riding a Deda Mag00stem for two years, and I have umpteen suspension forks with magnesiumlower leg assemblies that I have been abusing for years and show no signsof failing anytime soon.As with anything, if you make it thin enough to weigh very little, yousharply decrease its lifespan, so you have to take that into account. Butthat is not unique to magnesium; it applies to lightweight components madeout of aluminum, titanium, steel and carbon as well.
LennardFeedback on chain replacement:
Dear Lennard,
My experience with chain/cog wear is that if you want to keep usingthat expensive cassette, the chain needs to be replaced when a 12 inchsection stretches to no more than 12 1/16 inches. I’ve used this standardfor over thirty years as a mechanic in the bike industry, and it is backedby numerous written sources.

This margin can even be slightly less on mountain bike drivetrainsused primarily for aggressive riding on steep terrain, because worn largecogs have even less tolerance for new chain than worn small cogs. The chainrides up more easily on large cogs, whereas on small cogs, rear derailleurtension is able to pull the chain roller down between fewer teeth.
DanDear Dan,
I am glad you said this; because that is actually the standard I usefor my own chains and almost never have to replace cogsets. But I said12-1/8” out of gun-shyness about being accused of trying to get peopleto buy more chains. I actually use the Rohloff chain-checker, and as soonas the “A” (for aluminum cogs) side drops into the chain (which is a littleunder 1/16-inch of elongation over 12-inch, by my measurement), I replaceit. Even though I am running it on steel or titanium cogs, I don’t waitfor the “S” (steel cog) side to drop in and indicate it is time to replaceit.
LennardLennard,
I’m writing in response to one of Tuesday’s mailing/responses. I agreewith your book in that a Shimano chain will typically need to be replacedevery 1500-2000 miles as not only a ‘performance enhancer’, but also aspreventative maintenance for the rest of the drivetrain components. However,the gentleman writing in (Tues. 1/21) spoke of his Campagnolo drivetrainwith around 4000 miles on it, and (rightfully) worried about the prospectof spending 64 dollars on a new Campy chain every 1500 miles. The truthis that you can squeeze about 3-4000 miles out of a Campy chain dependingon your riding style (do you mash gears, cross chain, ride in the slop,use XD40 as lube… all bad) because for whatever reason Mr. Campagnolohas figured out a way to make a chain with tighter tolerances and strongerrivets than Shimano’s offering(s). At about double the price of a Dura-Acechain, he (Mr. Campy) knows it too. The 20 dollars spent on a ‘chain checker’tool would be a wise investment for all home mechanics.
Travis


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.