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Bikexchange logo, link to Home                    Ask the Mechanic
Autumn 1997                  Autumn 96 | Winter 97 | Spring/Summer 97

What's the best way to lube your freewheel? Stuck in gear and need expert advice? Ask Andy the Mechanic (a.k.a. Andy Wallen), the proprietor of Wheelcraft Bicycles of Wheeling, West Virginia. We welcome your questions. The squeaky wheel gets the grease! E-mail to ibike@bikexchange.com, subject "ask the mechanic." Andy will e-mail your answer and we will post it afterward.

Read the Ask the Mechanic Disclaimer.

Autumn 1997 Questions...

Dear Andy,

The alloy rims on my mountain bike are quite dirty and have a lot of brake pad residue.

What is the best way to remove the brake crud from the rim? Is it advisable to use an abrasive, like a wire brush to rough up the rim for better stopping power?

What type of brake pads do you recommend for all riding conditions, including wet? The brakes are Shimano cantilevers.

Thanx for any advice you can give.

Most Sincerely,

Mark Westlund

Dear Mark,

You should keep your rims and brake pads clean for optimum performance. Pads should be scuffed up with medium sandpaper once in a while, and cleaned with a mild degreaser frequently. We have good luck here with Kool Stop grey pads for all purpose riding, although they don't last as long as the black ones. Clean your rims with Windex and use a Scotch Brite pad to remove built up crud. Don't use anything much grittier because you will accelerate the wear on your rims. Some folks use acetone, but I don't like to use harsh chemicals, and if it gets on your tires you may have a problem. Be aware that rims have a finite lifetime, and it is even more finite when you ride in mud and such. A worn through rim will peel apart on you, usually during a hairy descent, causing a blowout and ensuing lack of control. Please replace them before this happens (at least every 2 years).

Andy

Dear Andy,

I am having a problem with my chain and gears on my mountain bike. When I am cranking up a hill using my 22t chainring and my chain and gears get wet and muddy, as often happens this time of year, my chain constantly gets pulled (from beneath as it rolls of the 22t chainring) up between my 32t chainring and my frame's chainstay. This causes my gears to lock up as well as damages my chain, chainring, and frame. I have several ideas about why this is happening:

1) Worn, stretched, or bent chain;
2) Chain is too loose;
3) Bottom bracket spindle is too short (causing chainrings to be too close
to frame).

I have a Schwinn s(9five).3 frame, Shimano LX derailleurs, and a Sugino crankset.

I have never seen anyone else have this problem. Have you ever come across
this problem before? If so, any suggestions.

John D'Amico

Dear John,

You are experiencing chainsuck, a malady for which there is no known cure. Don't ride in the mud!! The best thing to do to minimize this problem is to frequently change chains--use a good one (KMC ss91) and use a suitable mud resistant lube (Finish Line xc lube ). A stainless steel chainring helps a lot--and a larger one seems to work better. Back in the days before compact drive we didn't have this problem very often. Consider muscling up and using a 24-tooth granny. Some customers report that using a bullet brothers chain tensioner all but eliminates this problem. Good luck.

Andy

Dear Andy,

I printed out a gear chart from here:

http://www.panix.com/~jbarrm/cycal/cycal.30f.html

After painstakingly counting those teeth (did I start on the one my finger is holding or the next one? I had to verbally repeat which one aloud over and over again).

I  understand gear inches is:
GearInches = (ChainRing / FreeWheel) * Wheel Diameter
Why do we use this unit of measure for gearing vs. simply the number of inches propelled forward in one revolution of the crank in that gear?

Cheers,
Johnny K. in DC
Check out John's
DC Area Cycling website

Dear Johnny K.,

"Gear inches" is one of those terms in cyclery that has no rational, logical, or technical relevance to anything other than to give us some means of comparing gear combinations. How this formula ever got to be the industry standard is beyond me. Why do we spend hours in high school diagramming sentences? Why are busses yellow, and even more important, why do cycleweenies adore anything in "judyyellow?" You see, the universe is loaded with unanswered questions, and this is a classic. My theories on this are:

1) Back in the 60's some wiener who lucked into a job with bicycling magazine needed to do something profound besides extolling the virtues of the "safety lever." Hand held calculators were just becoming available, so he bought one and started counting teeth instead of riding bikes, setting a lasting trend in bicycle R&D.

2) It's a French thing, like the presta valve conspiracy.

Andy

Dear Andy,

I know little about the bike lingo, but here it goes. I have a problem with my crank area, I think. Every time I make a rotation with the peddles I get a knock down in that area. I've taken all that apart, cleaned and re-greased the bearings and the thing the peddles attach to, I also made sure all was secure and tight. I know if the bottom circle/nut is loose it will make a noise similar to the one I feel and hear. I'm wondering could it be the back rim or peddles. The bike is an older Schwinn, late 80's early 90's road bike. I think it's a Schwinn World Sport. If you got any ideas it would be great to hear from you. Thanks for your time.

Chip Houze

Dear Chip,

Your problem could be almost anything. I suspect that the taper in one of your crank arms is worn from being ridden loose. This would involve a new crankset. It's also possible that,if you have a cup and cone bottom bracket, the spindle or cups are worn. I would also consider trying a new rear wheel and pedals.

Andy


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