By Lennard Zinn
Rake, trail and the difference between the two
In your November9 Technical Q&A you said that a 44/45mm rake would steer less quicklyand be more stable than a 47mm rake. Is that a typo? I thought shorterrake would tighten up the wheelbase and make the head tube angle feel steeper–yieldingquicker handling and a more “twitchy” feeling bicycle.
Sorry, but the statement is correct and your interpretation about forkrake’s effect is wrong. Indeed, a steeper head angle does make the bikehandle more quickly (reduces fork trail), yes. However, a reduced forkrake makes the bike more stable (increases fork trail). For a full explanation,I go into this in detail in my latest book, “Zinn’sCycling Primer.” That is not to say that less rake won’t make the ridemore jarring and increase the propensity for high-speed shimmy, but thoseare completely different vibration issues unrelated to cornering stability.
I’m wondering about the best and most efficient way to clean a cassettewithout having to remove it from the wheel. I have been using White Lightning’sCleanSafe degreaser on my chain by spraying it on while holding a rag behindthe chain to avoid spraying it on my frame. It seems like this would alsobe a quick way to clean the cassette, but I’ve been reluctant to do sofor fear of the degreaser getting into the freehub’s bearings. Is thisa reasonable concern? If so, if I were to tilt the wheel so that the degreaserwere to drip off the cassette and then hose it off, would this be safer?Do you have any alternative suggestions for cleaning a cassette?
What I can say is that professional team mechanics who clean cogs upin a hurry every day do it with a brush and squirt straight down from thetop with either diesel fuel or a degreaser like Simple Green or the equivalent.They finish off with a brush and soapy water. Below are some other solutions.
Answer from Paul Morningstar, maker of the Morningstar Freehub Buddyfreehub-cleaning tool
The first recommendation I’d suggest is to use a chain lubethat does not attract or hold dirt , turning the cassette into a goopymess. Boiling the chain in a paraffin wax mix is recommended. Without accumulatedgunk jammed in, the cleaning of the cogs is much easier. Using a masterlink, and a piece of wire from the chainring pulling the RD cage allowsfor easier chain removal.Back to Chris’s concerns: The most effective way to clean the cogs without removing the cassette is by using only a brush or stick without any water or solvents. Chris is correct in his worry.If Chris is using a lube that attracts dirt, the only way is to removethe complete mess safely is to remove the cassette. One needs to ask, howclean do I want it? Was it causing shift problems? His worries of contaminatingthe freehub bearings (as well as the wheel bearings) are valid. Any contaminationof the mechanism should be removed as soon as possible. Those tiny bearingslike swimming in clean, light grease and the easiest way of doing thatis to use the Freehub Buddy. Once the new Morningstar dust shield is installedthe job gets very easy during regular axle maintenance. Along with that,he will enjoy long freehub life and faster shifts.
Answer from WheelsManufacturing, maker of cassette cog kits cross-compatible betweenCampagnolo and Shimano
You know Lennard, I have always had the same problem. Thereno perfect solutions. I always end up just pulling the cassette off andgoing at it. Seems like we have lots of chain cleaning solutions but nocassette cleaning.
Overhauling my favorite Looks
I was hoping that you could help me out with overhauling an old pairof Look PP96 – Carbo Pro pedals. These pedals are circa 1990 andI have never overhauled it due to the smooth spinning characteristics andbomb proof design (at least I think so). Finally, one of the spindles seema little loose.
I believe a special plastic tool is required but I’m not sure what itis. If a special tool is required, is it readily available?
Yes, a special plastic splined tool you can clamp in a vise is required,and the internal pedal threads are opposite of the direction of the threadson the respective spindles, so be careful you do not break the tool byturning it the wrong way. A full description of overhauling these pedals(and all road pedals, for that matter), can be found in “Zinnand the Art of Road Bike Maintenance.”
Is there a torque value for the bolts on an ISO bottom bracket adapter?I figure they have to be pretty tight. I am adapting the BB shell of a1981 Schwinn Varsity 10-speed and I don’t want to get wrapped up in torquevalues but I figured it’s got to be somewhat important if thereare tables in the back of your book dedicated to it. The packaging forthe adapters doesn’t list anything regarding torque for the bolts.
Answer from Truvativ
Thanks for asking this question in regard to our BMX to Euro’adapters (press-in BMX frame being converted to use a threaded BSA BB).
First, a short rant for the greater good: Every competent mechanicshould have a correctly calibrated torque wrench in their tool kit anduse it. The macho mechanic’s statement that “my elbow is my torque wrench”merely shows their ignorance of mechanical systems and the importance oftorque. Torque specifications exist for a reason: they are the simplestmethod of ensuring that the correct tension is produced in a fastener duringassembly. Under- or over-torqued fasteners can lead to many possible failures,some of which can result in serious injury while others merely hurt thepocketbook. Always consult the manufacturer’s torque specifications anduse a torque wrench.
Truvativ’s BMX American-to-Euro adapters allow the conversion of apress-in cup style (American) BMX frame to one that can accept a standardBSA threaded bottom bracket (known as “Euro BB’s” in BMX lingo). Theseadapters consist of pressed-in threaded cups held together axially by threegrade 10.9 M4 bolts. The press fit of the adapters into the frame is primarilyresponsible for retaining the adapters while the three bolts provide additionalbackup retention. The installation torque requirements for these boltsare calculated to prevent the fasteners from loosening during use.
To install the adapters, first press them into the frame using thesame tools you would use to install normal American BMX cups into the frame.Do not attempt to use the bolts to draw, or press, the cups into the frame.During the press operation, make sure the three sets of bolt holes on eachcup line up with other. Next, lightly grease the threads and underneaththe head of each bolt and tighten them to 33- to 36 inch-pounds each (yourquestion answered). I’d recommend tightening each bolt a little at a timeuntil all are tightened to the proper torque. The adapters are now securelyattached to your frame and you are ready to install the threaded BSA BB.
Here is some feedback regarding my recent column on removingbottom bracket cups with stripped splines1. Dear Lennard,
I’ve had the same problem stripping Shimano BB cups, but a very simpleand inexpensive fix exists at most hardware stores. A long bolt, nut andwide washer will hold the BB tool tight. Stick the bolt through the endof the BB tool and out the other side of the BB. Put washer against theshell or other cup and thread nut hand tight. That gives enough “bite”when turning the BB tool. Simply back off the nut as the cup is unscrewedfrom the shell (while retaining some tightness so the tool can ‘bite’).This setup costs under two bucks, not including the Shimano BB tool.
George2. Dear Lennard,
To remove a recalcitrant right hand bottom bracket cup, it’s a loteasier to use a “universal” (friction-activated) fixed cup remover thanto grind or saw it out. Sheldon Brown’s web pages have a tip on how tomake a nifty (and cheap) homemade one.
Dan3. Dear Lennard,
I am writing in reference to the reader with the UN72 bottom bracket problem. My experience with the UN72 has shown that they do incorporate a removable cup as shown in the picture I am attaching.
The picture is of a BB I removed last week under similar circumstances as described in the letter from Jeff. Of interest also is in my experience the cups become destroyed from a worn or low quality tool, something people should be aware of.
You are correct. When I answered that question, I ran out to the shopto see what Shimano square-taper BBs I had where the cartridge separatedfrom the right hand cup, and all I had here were UN73 and UN53 models,since I supply these with my custom cranks and have stacks of them around.The UN73 and UN53 replaced the UN72 and UN52, and perhaps the major difference between the current “3” models and the older “2” models is that the cartridge is no longer separate from the right hand cup on the new ones. Thanks forcorrecting me on that. I was thinking at the time I wrote it that the 73and 72 were the same, and I didn’t double-check. I had that image in mindof exactly the BB in the photo, where its end has rusted inside the rightcup, but I could not recall at the time which model it was.
LennardHere is some feedback from the reader who asked about keeping the front wheel down on a big road bike:
I followed your advice by dropping my elbows to get my back flatter and studying some Tivo’d Tour de France stages to see how the pros climb. Hand position and elbow angle are everything! I find my climbing is a lot better, the front end a lot less squirrelly, and my flats cruising a lot more aerodynamic. Thanks very much.
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.