Making it work: Have a beer, fix your bike

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By Lennard Zinn

Photo: Galen Nathanson

A can of beer always helps to make problems seem less important, butsometimes, it can actually fix bike problems! Aluminum beveragecans are 0.1mm thick and are easy to cut with a knife or a pair of scissors,rendering them quite useful for making minor spacing adjustments on a bike.

Slipping seatpost
A seatpost that gradually slips downward as you ride can be causedby an ovalized seat tube, a sizing difference between the seatpost andseat tube or a tolerance buildup over a number of parts; the latter isparticularly rampant with suspension seatposts in oversized seat tubes.What can you do?

A common “fix” is putting grease mixed with sand or valve-grinding compoundon the seatpost. This often does not work, and it mars the finish of thepost. A more elegant and effective solution is to cut a small shim outof a beer or pop can and put it in between the seatpost and seat tube (orseat-tube sleeve).

Cut out a 1-inch X 3-inch piece of pop can with a pair of scissors,rounding the corners. Hold it lengthwise down along the wall of the seattube (not at the slot) with about half of its length sticking out of thetop. Stick in the (greased) seatpost. If the post won’t go in, make theshim narrower. If it fits sloppily, try a wider strip. Insert the post,assuring that the shim stays in place.

For a late-night bike assembly, if you only have a seatpost a size (0.2mm)too small and want to ride anyway, one wrap of a pop can adds 0.2mm. Makethe shim just long enough that the ends don’t quite meet when wrapped aroundthe post.

Most suspension posts come in only one or two diameters. If you havea 27.2mm suspension post, and your bike takes, for instance, a 30.2mm seatpost,then you need to purchase a 1.5mm-thick shim sleeve that has a 30.2mm O.D.and a 27.2mm I.D. It looks like a short aluminum tube with a lip aroundone end and longitudinal slit down one side. You may find, though, thatthere is enough slop in the fit between the seat tube and the sleeve andbetween the sleeve and the seatpost that the post slowly inches down asyou ride. A small beer-can shim between the sleeve and the post can keepit from sliding down.

Also, if your saddle is slipping in the seatpost clamp, sometimes abeer-can shim can help. It was on a Moxey suspension post, which has twoclamshell pieces that clamp the rails and are squeezed together by a hingedpart closing over them. By slipping some beer-can shims between the hingedtop piece and the two knurled semi-cylindrical clamshell halves it clampsover, the slippage, as well as an annoying creaking sound, disappeared.

Sometimes the head of the seatpost won’t clamp the saddle rails wellif the top piece has gotten too bent on a post with a two-bolt clamp. Onsome seatposts, the top of the clamp wraps over a pair of clamping piecesthat resemble a tube sliced lengthwise that are notched for the seat rails.If the top of the clamp is stretched or bent, it cannot hold these piecestightly enough, and the saddle can slip straight back or rotate (usuallynose down). A couple of beer can ships around the cylindrical clampingpieces can fix that.

There are famous examples of shims being used with great success.

Photo: AFP (file photo)

Handlebars
If your handlebars slip in the stem clamp, that can be dangerous whenyou slam on your brakes. A beer-can shim between the bar and the stem clampwill tighten it up and prevent the bar from twisting. It is not a greatidea to mess too much with worn stems and bars, though, especially superlightones. If the bar and/or the stem has gotten so misshapen that the clampdoes not work well anymore, just use the shims as a temporary fix, andget another stem and bar.

Disc-brake Rotors
If you have disc brakes and a number of wheels, you want to be ableto interchange them without the rotor dragging on the brake pads. Sincethe spacing between pad and rotor is on the order of 0.01-0.015 inch (0.25-0.4mm)and there is often a slight back-end-forth wobble to the rotor to boot,a minor rotor offset will make it drag loudly. What to do?

Crack open a can of beer, of course! Cut rotor shims with a knife usinga template, since they must be quite precise. I use a bolt-on disc hubadapter as a template and screw it down to a block of wood, through oneor two layers of aluminum cut from a can. Then I cut around the inner andouter edges of the adapter. I trace the bolt holes with a scribe and punchthem out with a hole punch.

These shims work great! Once you go to this trouble, there is no adjustingof brakes to be done whatsoever when you switch wheels. Incidentally, onceI got my rotors all in the same spot, I switch wheels with Hayes and Shimanorotors back and forth between bikes with either make of brake without anyproblem.

Disc-brake Calipers
If you are a stickler for quiet brakes, you can also cut out shim washersfor spacing the brake caliper from International Standard brake mountson the frame or fork. The thinnest spacers you will find packed with adisc brake are 0.2mm, but if inserting one moves the brake in too far andremoving it moves it out too far, beer-can washers will move the brakein half as much.

Cogsets that don’t shift well
If you have a cogset with which your rear derailleur works great onsome of the cogs but cannot be adjusted to shift perfectly on all of them,drinking a little beer could help here as well. The spacing between nine-speedcogs is so close that the derailleur has to move very precisely under eachcog or the chain will try to climb to the next one. A thin, judiciouslyplaced spacer between a couple of cogs can completely fix skipping, auto-shiftingand noise that any amount of cable-tension adjustment cannot eliminate.

I have, for instance, an early SRAM 9-speed 11-34 cogset that I measureto be 0.3mm narrower than a Shimano cogset. Similarly, I have a 0.2mm under-width Shimano Dura-Ace cogset from the first round of nine-speed production thatfrustrates proper derailleur adjustment over the full range. If I get thecable tension right on the small cogs with either of these cogsets, whenthe chain is on the second- or third-largest cog, the chain will try toclimb to the next larger cog. This is a bummer when you are trying to getup a hill.

The fix is to cut out spacers from an aluminum can to go between someof the cogs in the center of the cogset. Cut around the inside profileof a cog into the aluminum sheet, and cut the outer circumference 3-4mmbigger. On the Dura-Ace cogset, two beer-can spacers between the 15 and16-tooth cogs completely fixes the problem. On the SRAM cogset, I put inthree pop-can spacers between the14 and 16-tooth cogs, making the cogsetstack thickness the same as a Shimano, and the chain no longer climbs upand skips on steep hills.

While there are some problems too big for a can of beer to fix, it canmake many small ones go away. When I told my 8-year-old niece that I wasgoing to fix her dad’s seatpost with a piece of a beer can, she asked,“Why a beer can? Why can’t you use a beer bottle?”
 

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