What are the counter-intuitive surprises an amateur bike mechanic encounters, after pedals and cables?

Question

Pedals

It's pretty obvious that one of the two pedals needs be tightened counterclockwise, but which one?

A brief reflection on the right pedal's sense of rotation (while pedaling forward) with respect to the crank would suggest that it is the pedal that needs to be tightened counterclockwise (so that it continues to be tightened further while pedaling).

It turns out that that's exactly wrong. Due to precession, it is the left pedal that needs to be tightened counterclockwise.

Barrel Adjusters

Likewise, with little thought and knowledge, a novice dabbling with bike mechanics, especially to fine tune derailleurs while riding, might be tempted to tighten a (brake or derailleur) cable by turning its barrel adjuster(s) clockwise.

Again, that's exactly wrong. Bowden cables are formed by a cable sheathed in a cable housing. The barrel adjusters neither tighten nor release the cable housing. They increase or decrease its length, and they affect the cable only indirectly—tightening the cable when the cable housing's length increases.

Hence to tighten, say, a derailleur cable to get it to a larger sprocket or chainring, it is necessary to release the barrel adjuster, which increases the length of the cable housing.

What are the counter-intuitive surprises an amateur bike mechanic encounters, after pedals and cables?

Clarification

The question I meant to ask is precisely the one asked here, but clearly—and despite the two examples provided for pedals and for barrel adjusters—I used particularly poor wording that made the question so generic to be useless for learning with any depth.

Answer 1

• More grease is not always better. Attracts excessive dirt and stuff.
• Well-greased bearings don’t spin smoothly by hand. Lots of amateur mechanics under-lubricate or use too thin of a lubricant because their bearings don’t spin as well as one would expect.
• The bearing adjustment on Shimano SPD pedals, as detailed in this question: Which Shimano pedals have reverse threaded bearing adjustments?
• The bearing sleeve on SPD pedals. The right pedal's is reverse threaded.
• Adjusting spoke nipples can be counterintuitive depending on which angle one is observing the nipple from.
• Torque requirements can be surprisingly low. Bike bolts often are used to tighten a clamp of some sort and therefore feel mushy when tightening, lacking the “hard stop” felt when tightening traditional joint layouts with solid components.
• Dimensional tolerances are much tighter than intuition would suggest. Mechanics are often tempted to do things like hammer components into place or grind things to fit. Please don’t, unless you really, really know what you are doing.
• Clamps such as stems, seat clamps, brake levers, etc. can be counterintuitive. One might reason that the clamp is only tight when the gap disappears. Of course, the gap is the only reason why the clamp can actually tighten, so overtightening may occur.
• Tighter is not always better for handlebar-mounted controls such as brakes and shifters. You want their clamps to be loose enough to rotate in a crash so you don’t damage them.
• Carbon fiber composites are not as fragile as cycling rhetoric would have one believe.
• The fastening method of Shimano Hollowtech 2 cranks (bar the latest M9100 ones) can be counterintuitive. Overtightening of the preload bolt is common because of people thinking it helps hold the crank arm on. This is also true of other similar systems that use pinch bolts and a preload cap.

Answer 2

Anyone tinkering with bikes needs to be aware of the perverse variety of standards (how many bottom bracket standards are there now?); that multiple actual sizes can be indicated by the same nominal size (26" tires can refer to an unreasonable number of actual sizes); that the same actual size can be indicated by more than one nominal size (rims measuring 622 mm at the bead seat diameter are variously referred to as 700C, 29", or 28", depending on whether you're talking about a road bike, mountain bike, or Dutch bike); or that the nominal size doesn't equal the actual size (a 1" quill stem is called that because it fits in a steerer tube with a 1" outer diameter; the stem itself does not have a 1" diameter).

Answer 3

In my experience, BSA and T47 cups are counterintuitive, and it is the right side cups that are left threaded, I.e. opposite to the case for pedals.

Note that the original question was more broad, and was later edited to focus on left hand threads. Cleat rotation (for those riders who need it) doesn’t involve this, but it can appear to operate counterintuitively. For clarity, if isn’t enough float to accommodate your natural foot position (usually to point slightly away from the cranks), you need to rotate your road cleats. This can be counterintuitive at first because you are looking at there cleat from what’s normally the bottom. I initially found that I was rotating the cleat opposite the direction I wanted. It has helped me to just imagine the crankarms being there when I adjust my cleat rotation.

That said, these two situations tend to be more limited in applicability. For most cyclists, the float available in your pedal system is usually enough, so most people may not need to rotate cleats. BB work is not something everyone does, in part because of the infrequent need to actually remove the BB. In my case, not all my bikes are BSA or T47 either, and I also decided to use two different BB manufacturers with different tools.

The late Jobst Brandt confirmed these two cases with an explanation of what causes precession of the right hand BB cups. I don't understand the explanation. He also adds that freewheel cones are another example where left hand threads are used.

On barrel adjusters, I somewhat agree with Michael’s comment on the main answer. I find the system intuitive. However, it took some time before I knew what the system was actually doing. I think people with average mechanical aptitude probably will be in the same boat. The same was true for me with rear derailleur adjustment, as there are several moving parts there.

Answer 4

In some Campagnolo chainsets, the central screw for tightening the hirth joint that connects the two halves of the crank spindle is left-handed, quoting the manual:

Warning: the titanium central screw FC-SR008 mounted exclusively on the Ultra-Torque Super Record 12v crankset, with titanium semiaxles, has a left-hand thread (to tighten, turn anti-clockwise, to loosen, turn clockwise).

Answer 5

As usual, Calvin Jones @ Park Tool says it best:

The direction of wrap is also important. We want the direction of handlebar wrap to match the direction of load as the hands rotate on the bars. Under load and stress, it's common for riders on the drops to rotate their wrists outward. Consequently, we want to match their left side with a counter-clockwise wrap from the rider's point of view.

He continues:

But on top this reverses. On top when we're riding, especially up the hill, people tend to twist their wrists back. [So we want the direction of wraps on the tops to be] the opposite of the direction on the drops.

Answer 6

I would say the one thing that's counter intuitive is that sometimes loosening things can be a good idea.

A couple of examples I can think of are things like the adjuster bolts for v-brakes and cantilever brakes, to even out the sides. Sometimes when trying to adjust them it's better to loosen them completely and start from scratch rather than tighten them to the point where one side is in almost as far as it will go.

Same goes for things like barrel adjusters for brake and gear cables .once you've tightened them too much it's time to reset to zero and readjust (or just replace) the cable.

Answer 7

There is the minimal size of the largest cog on the cassette, and maximal size of the smallest cog (as follows from here). Intuitively one would think that the largest cog can only be too large. But as the derailleur glides in a diagonal line as it shifts up and down, the cogs must increase in size following some expected progression.

This is important because there are cassettes on the market that start from 12, 13 or 14 teeth cog, or end at 25. But in the specs of the derailleur is clearly written, for instance: smallest cog 11 to 12 while largest cog 32 to 36. Good to know before ordering that cassette that goes from 14 to 25 like this one, that otherwise looks so optimal for your life style.

Answer 8

Shimano hubs, or any other cup and cone hubs are notoriously hard to service. They are very easy to take apart and clean, but getting correct retainer nut tension right is almost black magic. Too loose, they will loosen on a ride, and you can either bend or break the axle. Too tight, cups and cones will be scratched and destroyed, and hubs will have too much drag. Shimano does not state any torque value, or a tip on that.

Answer 9

Not all Schrader valves are the same diameter.

Valves that feature the rubber protection at the bottom (as pictured) usually have this protection layer in addition to the standard diameter. Such a valve may not pass through the hole that is only as wide as to pass the Schrader valve without protection layer. Both drilling wider hole and removing the layer are problematic.

This may only cost you the price of one-two tubes if you are in your garage, but may create lots of problems if that non-fitting tube is that you took for a spare into wilderness.

I have never seen any labeling on the tube box that would show it may not fit some rims. You need to look into the photo or check visually. If the valve has this protection layer, or if the base of the valve is not seen, and you are not sure, do not buy.

Answer 10

Bottom brackets, like pedals, have a side that threads opposite.

Answer 11

Chain skipping

A worn chainring looks fine to the untrained eye.

A worn cassette looks okay too, mostly because we see the unworn sillhouetted biggest cog easier than any other cog.

Conversely a worn jockey wheel is probably perfectly functional.

An elongated chain looks totally normal from a distance.

Dirt can be invisible even when packed up enough in a cassette to stop the chain from seating well into the smallest cogs. This leads to more skipping but only in high gears AND when soft-pedalling.