A Basic Guide to Road Bike Bottom Brackets

A Basic Guide to Road Bike Bottom Brackets

Your bottom bracket isn’t the most exciting part of your road bike, which makes it easy to ignore until something is wrong with it. However, it’s a very important part of your bike, so in this article, we tell you a little more about this essential yet relatively uncelebrated component.

What is a bottom bracket? 

Your bottom bracket connects your cranks to your bike in such a way that they can rotate freely as you pedal and put power into the drivetrain. It is located in the bottom bracket shell which is where your frame’s down tube, seat tube and chain stays all come together. A bottom bracket typically contains bearings that enable the crank’s spindle to rotate. Shell and spindle widths vary depending on the type of bottom bracket. 

What’s the big deal?

If your bottom bracket is working well, you can pedal smoothly with minimal resistance. That means the energy you apply to the pedals gets transferred efficiently to the bike.

Looking back over time, there have probably been as many different bottom bracket designs as there are bike brands; and some bike brands have even been known to come up with their own proprietary bottom bracket designs. 

Modern bottom brackets tend to come in two general types: threaded and press fit. 

Threaded bottom brackets

Threaded bottom brackets can only be used with frames that have a threaded bottom bracket shell. This is because threaded bottom brackets must be screwed into the frame. These bottom bracket’s bearings are typically held in place within cups.

What’s tricky about threaded bottom brackets is that not all threaded bottom brackets are  created equal, which means that different types of threaded bottom brackets can’t just be swapped for other types. 

For example, two common threaded types are Italian or English. Both sides of an Italian standard bottom bracket are right threaded; whereas English standard bottom brackets have opposite threading, like your pedals do. The advantage to the English design is that the drive side does not come loose through the forces of normal pedaling action like it tends to on the Italian version.

The good news about threaded bottom brackets is that they are relatively easy to install and maintain.

Press fit bottom brackets

Also known as threadless bottom brackets, press fit bottom brackets get, well, pressed into your frame’s bottom bracket shell instead of threaded in. They are effectively cartridge bearings pushed into the shell, and their design often allows thicker crank spindles, which some riders experience as stiffer and more efficient.

Some examples include BB90/95, PF86/92 and BB30. BBright and BB386. Special tools may be required to press the bottom bracket cups into your frame during installation and likewise to remove them again should you ever need to do so. 

Square taper bottom brackets

This once very popular type of bottom bracket combines the bearings of the bottom bracket and the crank’s axle together into one removeable part. The cranks affix onto two square tapers on either side of the bottom bracket.
Square taper bottom brackets are effectively a specific kind of threaded bottom bracket. They are frequently found on older, vintage bikes, but are still on some more contemporary bikes. 

What can go wrong 

When your bottom bracket is poorly adjusted, it may develop play or a wobble, causing less efficient transfer of energy from you to your bike. 

Another common problem is that when bearings get contaminated with dirt and water or wear out, there is more friction in turning the cranks, so it feels harder to pedal. Sometimes the bearings actually feel rough when you spin them; other times, you may hear and/or feel a click or two with each pedal stroke, especially under higher loads.

Maintenance 

It is important to maintain your bottom bracket. If you have a threaded bottom bracket, remove it periodically and refresh the anti-seize compound that keeps it from getting permanently stuck in your frame. 

And no matter what type of bottom bracket, check your bearings regularly to keep them running smooth. Loose bearings in some types of bottom brackets can been taken apart and cleaned and re-greased; whereas in cartridge-type bottom brackets, you’ll simply replace the cartridge bearings when they go bad.

You can make your bottom bracket last longer by carefully cleaning your bike. Never spray high pressure water directly at and around your bottom bracket as it will eventually penetrate seals compromise the integrity of the bearings.

Lots of different bottom bracket standards mean there are lots of different tools for installing and removing them. If you don’t have the proper tools and skills, you may need to take your bike to your local shop to help you fix any bottom bracket issues.

How to Set Your Optimum Chainring Position (OCP)

How to Set Your Optimum Chainring Position (OCP)

Switching from using round chainrings to ROTOR’s Q-Rings is easy, but it does require some initial setup followed by a transition period for full adaptation.

Why Q?

Optimum Chainring Position (OCP) is what allows you to vary the rotational position of a Q-Ring, thereby enabling you to adjust it to the precise point where you deliver maximum power during a single pedal rotation.

ROTOR suggests the following initial OCP setups by discipline:

  • Road: Position 3
  • Triathlon and TT: Position 4
  • MTB: Position 3

Because Q-Rings use leg muscles differently than round chainrings, your muscles will need time to adapt to the new, more efficient way of pedalling. Adaptation is a gradual process covering four stages with each stage taking between one day and one week. Most riders will require at least 10 hours of pedalling time to make the full transition.

Stage 1

In stage 1, you will learn to pedal more efficiently. Pedalling may initially feel different, and you may find yourself turning the pedals at a faster or slower rate than your usual cadence. Don’t worry about any initial jerkiness – it will smooth out over time.

Stage 2

You will start to feel more capable and more powerful in stage 2, and your spin will improve on climbs. Many who suffer knee pain will start to notice it less – assuming their OCP is correctly adjusted.

Stage 3 + 4

Stage 3 will bring improved biomechanical efficiency, which produces a smoother pedal stroke due to fuller activation of muscle groups. You will be creating more power than with round chainrings. If you experience no issues during this stage, you have correctly set your OCP and are onto Stage 4 of adaptation. Those encountering issues should read on for further OCP setting instructions.

If you experience the following symptoms, you are arriving at the max chainring diameter too late because your OCP number is too big, and you should reduce your OCP by one setting:

  • You accelerate and sprint easily, but have difficulty maintaining speed.
  • You feel pedalling resistance too late in your pedal stroke and/or you are hyperextending your ankle.
  • You need a lower cadence to be comfortable.
  • Your sit further forward than usual to pedal comfortably.
  • You are comfortable pedalling while standing, but not while seated.
  • You have new pain at the back of your leg behind your knee.

On the other hand, if your OCP is set too low, you will find yourself arriving at the max chainring diameter too soon during your pedal stroke. You should increase your OCP setting by one if you experience the following:

  • You find it easy to maintain a steady speed but have difficulty accelerating and sprinting.
  • You feel pedalling resistance too early in your pedal stroke and/or you are hyperflexing your ankle.
  • You need a higher cadence to be comfortable.
  • You sit further back than usual to pedal comfortably.
  • You are comfortable pedalling while seated, but not while standing.
  • You have a new pain at the front of your knee.

Once you’ve got your OCP correctly adjusted, it’s time for stage 4 and final adaptation, which comes naturally with more cumulative pedalling time using Q-Rings.

A few final setup notes

Different bikes may need different OCPs – don’t assume you will use the same position on each of your bikes.

Adjacent chainrings in multi-ring setups may require different OCP’s.

Road Q-Rings and QXL have five OCP points while MTB Q-Rings have three OCP points.

If you are using a Micro Adjust Spider (MAS), your number of OCP points is effectively doubled because it reduces the angle between OCP points by 2.5 degrees, thereby offering micro adjustments. In this case, you should adjust your OCP in 1/2-step increments.