from Rookie’s keyboard
Hello, friends
I have a confession to make. I am a square taper BB fanboy. It’s sounds weird I know. But I am 100% certain that most people out there will be better off with a simple square taper bottom brack. And the only real incentive to get something different is crank incompatiblity.
What about Hollowtech? What about Octalink some will say? Well, I’ve presented my opnion on Hollowtech here.
And today, I’ll talk about why SQ TP BBs are superior to Octalink too.
Let’s go.
Square Taper Bottom Bracket
The Positives of SQ TP BBs
Availability
Square taper bottom brackets have been the standard for decades. The market is fully saturated with models ranging from generic units to high-end models with a multi-year warranty.
Serviceable (partially)
The bearings of modern square taper bottom brackets are sealed and therefore not serviceable. When the unit starts to complain, the user is expected to replace the entire cartridge.
However, the square taper bottom brackets found on older bikes from the 70s and 80s are fully serviceable.
If the spindle or the bearings are damaged, they can be replaced.
Older square taper bottom brackets can theoretically be used forever if serviced adequately. They’re also quite cheap.
The downside is that many bike shops do not store them due to the lack of demand.
Supreme Crank Compatibility
A square taper can be used with a great variety of cranks. It’s possible to install a crank from the 70s or one produced last year. The user can also rely on cranks from various brands. There is one exception, however – Campagnolo.
There are two square taper standards – ISO (Campagnolo) and JIS (Shimano, SRAM…etc.).
The JIS system is wider than the ISO. As a result, an ISO crank won’t go far enough on the spindle of a JIS square taper bottom bracket.
Meanwhile, Octalink cranks are limited to comparatively newer models produced by Shimano. If you’re looking for a variety of options Octalink does not fit the bill.
Large Bearings
The bearing of SQ TP BBs are larger and thus more likely to last longer. Of course, the longevity of the bearings is dependent on the quality of manufacturing too.
The Negatives of SQ TP BBs
Rounded Crank Tapers
If a crank arm isn’t secured to the bottom bracket, it can start moving. The friction between the crank which is often made of aluminum (soft metal) against the steel (harder metal) spindle, can smoothen the square edges of the crank and thus make it impossible to secure the crank to the bottom bracket.
Octalink cranks don’t have the same problem because the splines result in multiple connection points. Thus, it’s less likely for the edges to get round.
Potentially Heavier
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 |
Conclusion: SQ TP BBs and Octalink models are very close. However, high-end bottom brackets such as Dura-Ace BB-7700 offer close to 100 grams weight savings.
The Pros of Octalink
Lighter & Stiffer Spindle
The main purpose of Octalink was to save weight and make the spindle stiffer.
How?
During pedaling the bottom bracket spindle experiences a phenomenon known as torsion. Torsion represents the twisting of a unit via external force.
During torsion, most of the stress is on the outer layer/wall of the spindle. For that reason, a pipe is more resistant to torsion than a rod of the same weight and material.
Why? The pipe and the rod contain the same amount of material. However, in the case of the rod, a lot of the 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 influences its resistance to torsion too. 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.
As a result, 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.
A Tight Connection to The Cranks
The splines on the spindle make it harder for the crank arm to get loose. Thus, Octalink bottom brackets are less likely to round the crank’s tapers.
The Negatives of Octalink
Small Bearings
Both Octalink and square taper models are internal bottom brackets and have their bearings within the bottom bracket body. Thus, the larger spindle of Octalink bottom brackets automatically results in the use of smaller bearings.
If the size of the bearings is preserved, the spindle simply won’t fit in the body.
The smaller the bearings, the less durable they are. Hence why Octalink users have complained of the bearings’ longevity for a long time.
Overly recessed Splines
The first version of Octalink bottom brackets was designed primarily for road bikes and has a spindle with relatively short splines.
When the same architecture was used on MTBs, the connection between the crank arm and the bottom bracket began failing.
The issue was addressed by creating Octalink 2 which has longer splines and is, therefore, better for more aggressive riding.
Possible Spline Damage During Installation
A major downside of Octalink is that the splines of the spindle are no longer visible once the crank arm is inserted. This creates the opportunity for inserting the crank improperly (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 loose connection between the cranks and the bottom bracket.
Limited Stock
SQ TP BBs are produced by a great number of companies. Thus, there are plenty of models to choose from in virtually every bike shop.
Octalink, on the other hand, is an exclusive Shimano product. Consequently, the user has to choose between fewer models. For the same reason, spare parts are scarce too.
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.
Limited Crank Compatibility
Octalink cranks are made primarily by two companies – Shimano and Suntour. Thus, your crank choice is slim.
Meanwhile, 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 of square taper bottom brackets because a very light setup can be acquired for cheap. For example, the user 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.
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 = Winner
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 SQ TPs over Octalink models 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.
That said, 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.
Until next time,
Rookie
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