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Technical Q&A with Lennard Zinn – Fight flats, lose speed?

  • By VeloNews.com
  • Published Dec. 2, 2008
  • Updated Nov. 17, 2009 at 11:23 AM EDT

By Lennard Zinn

Some tires generate more resistance than others.

Photo:

Dear Lennard,
I’m a 39-year-old, 175 lb., 150-200 miles-per-week recreational rider who frequently rides long charity rides and occasionally races. I recently switched to Specialized Armadillo Elite tires to avoid a rash of flats I’d been having, and they’ve worked wonders (no flats at all since the switch.) I had most recently been riding Schwalbe Stelvios, and Michelin Lithions prior to them.

I’ve always been a front of the pack rider in our local group, however, since the switch, I’ve struggled to keep pace with riders I usually pull, and have lost about 1.5 mph in solo riding. The Armadillos weigh about 340g vs. 235g for the Stelvios … can 105g x 2 really make that much difference? I live in Myrtle Beach, South Carolina, which can be very windy but completely flat (our biggest hill is a 65-foot bridge over the Intracoastal Waterway,) so I’ve never really counted grams before.
Ryan

Dear Ryan,
I think you are feeling a rolling resistance difference as much as a weight difference. And no, I don’t think weight alone accounts for the difference you noticed.

The fat, stiff aramid (i.e., Kevlar) threads comprising your Armadillo casing are very tough, accounting for the remarkable durability of that tire. But that casing also absorbs a lot of energy as it rolls, compared to a supple casing of thin, flexible fibers that can move and conform to the micro-contours of the road surface.
Lennard

Dear Lennard,
Could you shed a little light on the BB-86 press fit bottom brackets?

Giant Bicycles is at least one manufacturer that is using them for 2009.
I guess it provides some of the benefits of BB30 but utilizes existing external BB type cranksets? There isn’t much information out there that I can find.
Raton

Dear Raton,
Yes, BB86, often confused with “BB90,” uses existing integrated-spindle/external-bearing cranksets on a press-in bearing system. BB30 is often perceived as a Cannondale and Specialized system and may account as much as anything for a host of BB83/BB86/BB90/BB92/BB94/BB95 “standards” now in circulation by bicycle manufacturers who don’t necessarily want to adopt the system of their competitors.

Here is a quick guide to a number of these new standards:

BB30, or 30 X 68 and 30 X 73mm bottom brackets, come in either 68mm or 73mm shell widths for road or mountain bikes. The spindle diameter is 30mm, and the 41mm-diameter bearings press straight into the BB shell and are held in place by snaprings. In addition to Cannondale (who named the system) and Specialized (which doesn’t call its system BB30), FSA and SRAM (TruVativ) make BB30 cranksets; Shimano does not, and Campagnolo makes press-in adaptor cups to fit its Ultra-Torque (and Fulcrum Racing-Torq) cranks to a BB30 shell.

Scott and Shimano came up with BB83/BB86, often called the “Shimano system,” but not by Shimano. It accepts a standard 24 X 90mm road or 24 X 95mm MTB crank spindle. The shell is 86.5mm wide with a 41mm ID. The bearing has a 37mm OD and is pressed into a nylon insert with a 41mm OD that presses into the frame . Each insert’s shoulder is 1.75mm wide, creating the 90mm width and hence the BB90 name. Shimano, FSA and SRAM offer BBs to fit this shell; Campagnolo makes press-in adaptor cups to fit its Ultra-Torque (and Fulcrum Racing-Torq) cranks to BB83/BB86 shells.

BB92 is the MTB version of the BB83/BB86 with a 91.5mm wide shell for MTB triple cranks. Again, the 3.5mm of the two shoulders add width to 95mm.

BB90 is Trek’s Campy- (and Shimano-, SRAM-, FSA-) compatible Madone system. The BB shell is 90mm wide by 37mm ID. The 37mm OD bearings (the same bearings as inside an external-bearing cup) insert directly into the carbon frame and accept integrated-spindle cranks.

BB95 is the MTB version of BB90 with a 95mm wide shell on the new Trek Top Fuel and Fuel EX carbon.

Wilier’s new system has a 94mm wide BB into which a Campagnolo Ultra-Torque (or Fulcrum Racing-Torq) crankset fits directly without cups or retaining clip.

Lennard

Aluminum post, carbon frame
Dear Lennard,
I know one is supposed to lube aluminum seatposts in aluminum frames and not lube carbon fiber posts in carbon fiber frames. I have an aluminum post (Thomson) in a carbon fiber frame (’09 Orbea Orca) should I lube or not and, if yes, with what?
Rich

Dear Rich,
Unless you already have some carbon-mounting paste or spray, just lubricate it with any grease and stick it in. You don’t want to not lube it, because it can freeze in there otherwise. Mark its height, and if it slips, then you should use carbon-mounting paste or spray.
Lennard

SpokePrep vs. Loctite?
Dear Lennard,
I was wondering if Loctite can be used in place of SpokePrep in wheel building and repair. They are similar products in that they are both anaerobic thread sealants and although I don’t have any info about the shear rating of SpokePrep, it would seem that there should be flavors of Loctite appropriate for wheel building. Also, SpokePrep is quite expensive and it only comes in the lifetime supply size, whereas Loctite is relatively inexpensive, it comes in usable quantities and it has uses other than wheel building.

Personally I have used both blue and green penetrating grade Loctite in a little wheel repair. Basically I had several spokes on my rear wheel that refused to stay tight; I was having to retrue my wheel every 5 or 10 miles and while it was great truing practice it was also annoying. I didn’t have easy access to SpokePrep so I resorted to what I could pick up at the nearby auto parts store.

I used the blue Loctite on the chronically loose spokes and I used the green penetrating grade Loctite on the rest of the spokes as a preventative. For now, at least, the wheel seems to be more or less bombproof. I trust that I haven’t done serious harm to my wheel, but I was wondering if you might have some insight into or experience with this.
Perry

An answer from DT:

First, SpokePrep is a Wheelsmith product, so I will comment on DT Swiss Spoke Freeze. Spoke Freeze, which was developed by DT Swiss and Loctite, is an anaerobic adhesive, which sets up under the hermetic contact of the spoke and nipple. It can be used in one of two ways:

1. Without a lubricant. The nipple will be firmly (permanently) fixed.

2. With a lubricant such as oil. The nipple is still fixed, but can be forcefully turned.

Spoke Freeze is sold in 10ml bottles and will last approximately 350 spokes. It sounds like Perry’s wheel has bigger problems and that any locking compound at this point is just a band aid. Chronically loose spokes could be an indicator of uneven or too low spoke tension. Perhaps a damaged rim that has to be pulled unevenly in order to be true?
Dave Agapito
DT Swiss Inc.


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.

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