27 votes

Is it bad for the bike to pedal backwards?

There are a couple of things you should consider: Your bike isn't going to care. You aren't going to loosen pedals or cranks spinning in reverse, because you're not applying any load, so there is no ...
  • 11.9k
25 votes
Accepted

Plastic ring on new Shimano crankset, toss or keep?

I haven't seen one of those before, but it looks as though it could stop the chain dropping between the bottom bracket shell (the bike frame) and the crankset if you ever drop the chain off the inside ...
  • 23.1k
24 votes

Stuck pedal, I've tried everything

I think your pedal is a lost cause. Even if you did get it off in the current condition, reinstalling and later removal will make later-you hate current-you. I would disassemble the pedal from the ...
  • 108k
23 votes
Accepted

Group of Bikes: Is 3x1 an option?

I don't think you can make a 3x1 setup work. In order to have the chain change gears, there needs to be a mechanism to take up the slack in the chain. In a normal dual-derailer setup, the rear ...
  • 18.7k
21 votes
Accepted

Why does a loose pedal destroy the crank threads?

Once loose, the pedal spindle will describe a cone as the crank rotates. This concentrates force at certain points in the crank threads, leading to damage. Top image shows the pedal spindle in the ...
19 votes
Accepted

Should square taper cranks be greased before installation?

I started getting seriously into bike work circa 2002 and was lucky enough to come across Jobst Brandt's view of the topic around that time. Since then, most of which time I've spent working as a ...
17 votes

Does the saddle height need to be changed when the crank length changes?

Saddle height for new bike setup purposes should always be set relative to the pedal, not the BB center or any other reference point. So yes, crank length makes a difference. Using the ground or BB ...
15 votes

Would variable crank arm length be beneficial to a rider?

The system you propose is just a third way to change gear, in a mechanically very complicated way. Any benefit that could be obtained by lengthening the cranks can already be obtained by moving to an ...
15 votes
Accepted

What type of crank fitting is this?

The bottom bracket spindle is for cottered crank. The bottom bracket looks like threaded one, so it is likely that it can be replaced with square taper or external cup bottom bracket. To tell which ...
  • 20.9k
15 votes
Accepted

Broken bottom bracket?

The bottom bracket is not damaged, the left hand crank arm is. You have a 'two piece' crank where the right side crank is permanently attached to a steel axle, and the left hand crank clamps onto the ...
14 votes
Accepted

What tool do I need for this bolt that holds the crank arm on this stationary bike?

That nut was put in the wrong way around. This is what the nut looks like: The hex end is what you should tighten with a approriate socket. This is what it should look like when installed correctly: ...
  • 3,275
13 votes

What are the advantages and disadvantages of the different chainset designs?

144mm: supported chainsets such as 52/42 with relatively narrow range freewheels 130mm: allowed a range such as 52/39, as freewheel (then cassette) range expanded 74mm: necessary to add a smaller ring,...
  • 4,110
13 votes

Crank-arm fell off *after lube*

Your crank arm is toast. In my experience, if a square taper ever gets loose while riding, even once, it's done. Retightening the bolts buys you a few miles at best but it'll loosen up again before ...
  • 11.9k
13 votes

Does crank length affect the number of gears a bicycle needs?

Not really. You might want different gears, but probably not fewer. Shorter crankarms give you less mechanical advantage—they're functionally equivalent to being in a higher gear. So you might want a ...
  • 25.6k
12 votes

39-53t chainring on full suspension bike

The Giant Reign is a long travel 'enduro' bike that is designed to be ridden down steep technical trails, not pedalled down road/fire trail. It's most likely that changing to a 39-53 will not work as ...
  • 17.7k
12 votes

Fuji bolt fell out please help!

The crank appears to be a cottered crank and hence the missing part is a cotter pin. See the article by Sheldon Brown about cottered cranks https://www.sheldonbrown.com/cotters.html These parts can be ...
11 votes

What if both wheels were powered by pedalling?

Many two wheel drive mountain bikes exist. Here's one article advertising a new one: There’s been no shortage of attempts to build a workable two wheel drive bicycle over the years, but this latest ...
  • 23.1k
11 votes
Accepted

What are the advantages and disadvantages of the different chainset designs?

I'm not an engineer or a historian, so I'm going to go off my memory and, where I can find it, companies' stated rationale for making a change. Bolt circle diameter The larger the BCD, the bigger the ...
  • 22.9k
11 votes

Stuck pedal, I've tried everything

I would try removing the crank and clamping the pedal in a bench vise. With the pedal pointed downward and held very firmly in the vise, you’d then try to turn the crank clockwise. Otherwise, the ...
  • 775
11 votes
Accepted

Are the chainrings supposed to have irregular sized teeth?

Yes, modern chainrings have teeth that vary from each other. They are formed that way to enhance shifting between the different chainrings. Older chainrings from a couple of decades ago had teeth ...
  • 4,199
11 votes

Removing a pedal that has skipped a thread

The most likely cause of what happened is the pedal was installed with insufficient torque. This can allow movement in the threads that degrades the crank threads, which are aluminum in most cases and ...
10 votes

What is "crank preload"

I added a definition of preload to the terminology index under the bearings page, as this is a term that is frequently referred to but not clearly defined. Consider your crankset. Preload is how tight ...
  • 22.9k
10 votes
Accepted

Crank fell off square taper BB. Should I replace bottom bracket

Without seeing any pictures, I think you'll likely want to replace both, but you can figure it out easily enough. Usually, the bottom bracket will be fine after a crank improperly coming loose. The ...
  • 11.9k
10 votes
Accepted

Do crank arm pullers vary in sizes or there is just one size?

The main distinction is whether the puller is for square taper (and Powerspline) versus Octalink/ISIS. Among square taper crank pullers, there are some older ones made with nutted spindles in mind ...
10 votes

Would variable crank arm length be beneficial to a rider?

The research on subject (source: Wilson & Papadopoulos: Bicycling Science, MIT Press 2004) shows that crank length has very little effect on pedaling efficiency or or maximum power output. There ...
  • 20.9k
10 votes

Shorter crankset on road bike

There is little research on the impact of crank length on power output in cycling. There are some lab studies, and they seem to show that even for crank lengths significantly shorter or longer than ...
  • 22.9k
10 votes
Accepted

How to keep square taper cranks tight?

You are undertightening the crank bolts on initial installation. 44Nm or 33 ft-lb work well as generic values for square taper cranks. A basic large beam-type torque wrench works well for crank bolts. ...
10 votes
Accepted

Do forged alloy crank arms suffer from age-related fatigue?

Aluminum has no fatigue limit and thus it is impossible to make an aluminum bike part that won't fail with enough use. Fatigue accumulates with load, not time. Good forged cranks with designs that ...
9 votes
Accepted

I have a broken my drive side crankarm - what do I need to do?

Yes, you need to replace the crank arm, if tightening the bolt does not make it 100% solid again. No doubt the crank arm had been loose for days, and had you tightened it earlier you might have "...
9 votes
Accepted

One crank arm won't come off

You must use a Crank Arm Puller tool: Park Tools Crank Arm Puller Here's how to use it: Video
  • 572

Only top scored, non community-wiki answers of a minimum length are eligible