from Rookie’s keyboard,
Hello, friends
If you’ve been reading this site for a while, you probably know that I am a big fan of square taper BBs, especially the old-school models that you can service with a set of cone wrenches.
In this post, I will tell you why Octalink, the successor of square taper BBs went extinct, whereas SQ taper continues to dominate the entry-level and mid-segment.
It’s actually very simple – the improvements that Octalink offers are practically inconsequential.
Sounds harsh, but it’s also true.
The main pros of Octalink BBs are:
- A lighter, stiffer spindle
The main goal of Octalink was to save weight and make the spindle stiffer.
When you are pedaling, the bottom bracket spindle experiences a phenomenon known as torsion or twisting.
During torsion, the main stress is on the outer wall of the spindle. For that reason, a pipe is more resistant to torsion than a rod of the same weight and material.
The pipe and the rod contain the same mass. But a lot of the rod’s material is closer to the center.
In the case of the pipe, all the material is part of its wall. Consequently, the pipe has a greater resistance to torsion thanks to its strategic composition.
The diameter of the pipe also influences its robustness. The greater the diameter, the stronger the pipe becomes.
If two pipes are made of the same material and have a matching wall thickness, the pipe with the greater diameter will be stronger.
Every increase in diameter gives the opportunity to make the pipe thinner without losing strength in comparison to the previous diameter.
The spindles of Octalink bottom brackets are a product of those principles and are therefore lighter and stiffer than square taper spindles.
But here’s the deal – it doesn’t really matter in practice. Good luck feeling that extra stiffness.
– Yoda
- A tighter connection to the cranks
The splines on the spindle make it harder for the crank arm to get loose. For that reason, Octalink bottom brackets are less likely to round the crank’s tapers.
While that’s pretty nice, the truth is that SQ taper cranks are super secure when installed properly.
As you can see, the pros of Octalink BBs are small if not practically meaningless. However, those models do have many downsides too:
1. Small Bearings
The larger spindle of Octalink bottom brackets automatically results in the use of smaller bearings.
If the size of the bearings is any larger, the spindle simply won’t fit in the body.
The smaller the bearings, the less durable they are.
2. Recessed Splines
The first version of Octalink bottom brackets was designed primarily for road bikes and had a spindle with relatively short splines.
When the same architecture was used on MTBs, the connection between the crank arm and the bottom bracket turned out too weak.
The issue was addressed by creating Octalink 2 which has longer splines and is, therefore, better for more aggressive riding.
The splines of Octalink V1 are about 5mm whereas those of Octalink V2 are 9mm.
3. Potential Spline Damage During Installation
A major downside of Octalink is that the spindle’s spline are no longer visible once the crank arm is inserted.
It’s therefore highly possible to insert the crank out of the necessary groove.
If you tighten the bolt when the crank arm isn’t properly fit, the spindle will dig new grooves into the crank and damage it.
This could lead to failed splines and a weak connection between the cranks and the bottom bracket.
3. Very limited offering
Square taper BBs are produced by a great number of companies, and there are plenty of models to choose from.
Octalink, on the other hand, is an exclusive Shimano product.
Note: Do Not Confuse Octalink with Isis
ISIS and Octalink bottom brackets look pretty similar on the outside, but the parts made for them are not interchangeable.
Octalink spindles have 8 splines (hence the name) whereas Isis bottom brackets have nine. Also, the splines of Isis BBs are longer.
4. Limited Crank Compatibility
Octalink cranks are made primarily by two companies – Shimano and Suntour.
Conversely, square taper cranks have been here since the 60s. You can install cranks ranging from retro models made by companies that no longer exist to modern versions.
This is a huge advantage because a very light setup can be acquired for cheap.
You can purchase a new square taper bottom bracket and couple it with a high-end Shimano crank from the 80s that weighs 600 grams or less.
5. An Abandoned System
The Octalink system has been abandoned in favor of the newer Hollowtech generations. Thus, it is highly unlikely that Octalink will gain additional improvements.
Square Taper = Domination
An objective look at the data makes it clear that square taper offers more value for money.
While Octalink is lighter and comes with a reduced chance of rounding the crank arm, the main downsides of the system are too big to justify its implementation.
The benefits of a SQ taper over an Octalink model are:
- Huge variety of bottom brackets and cranks made by multiple brands
- Longer lasting bearings
- The same bottom bracket can be used for a road and an MTB bike
- More convenient crank installation
- Some models weigh as much or slightly more than Octalinks, thus the weight savings offered by Octalink are too slim to matter, especially to recreational riders.
- Octalink has a stiffer spindle, but the spindles of square taper bottom brackets are stiff enough for most people.
Nonetheless, Octalink bottom brackets offer solid performance and can last a long time. If you have a bicycle equipped with one, it makes no sense to replace the unit until needed.
Weight Comparison
The table below compares the weights of square taper bottom brackets and Octalink models.
| Square Taper | Weight | Octalink | Weight |
|---|---|---|---|
| Campagnolo Chorus | 220g | Shimano Dura-Ace BB-7700 | 173g |
| Token Square Taper – ITA | 205g | Shimano Deore LX ES51 | 262g |
| Token Bottom Bracket BSA-68-JIS | 255g | Shimano Dura Ace BB-7710 | 244g |
| Miche Team BSA68 | 255g | Shimano 105 BB-5500 | 250g |
| Stronglight JP 400 | 280g | Shimano ES51 | 262g |
| Shimano BB-UN300 | 267g | ||
| FSA RPM BB-7420AL | 256g | ||
| Miche Primato Pista | 275g | ||
| Miche Primato Evo Light | 204g | ||
| Average: | 246g | Average: | 238g |
The number are close. High-end bottom brackets such as Dura-Ace BB-7700 offer close to 100 grams weight savings, but that isn’t much in the world of recreational cycling.
Until next time,
Rookie
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