Archive | Bottom brackets

Why Square Taper Bottom Brackets?

Square taper bottom brackets may seem like anachronisms dating from the last century, and yet they remain the best option for metal cranks. Here is why our Rene Herse cranks use square tapers and will continue to do so in the future.

Modern bottom brackets have larger spindles, so they can use thinner walls. The result is a lighter bottom bracket – but the larger spindle requires more material on the crank.

No problem on a carbon crank (above), which needs to be large anyhow, because carbon is very light, but also bulky. Just don’t try to replicate the massive shape of a carbon crank in aluminum: It will get very heavy.

Our Rene Herse cranks are so incredibly light – just 490 grams for the 42/24 shown above – because they use only as much material as necessary. We’ve optimized the shape using Finite Element Analysis to remove all material that isn’t needed, but keeping aluminum where it’s needed for strength. The photo above shows that there is just enough material to fit a slender square taper spindle. Imagine how much material we’d have to add to make room for a massive spindle!

The light weight doesn’t come at the expense of durability or safety: Our cranks pass the most stringent EN ‘Racing Bike’ test for fatigue resistance. Few other aluminum cranks are as light and as strong.

There is another benefit of square tapers: The taper reforms itself every time you install the crank. You can remove and install the cranks dozens (or hundreds) of times, yet the square tapers will not develop play. And even if a crank comes loose by accident because the crank bolt wasn’t tightened enough, you can usually reform the taper: Tighten the crank bolt as much as you can, then ride the bike for 5 miles, retighten the bolt, etc. Do this five times, and the taper will usually be fine, unless it’s really been damaged beyond repair.

The smaller spindle of a square taper has another advantage: It leaves more room for the bearings. Above is an SKF bottom bracket that I cut open after years of use. The large ball in the center shows the size of the balls used in the SKF bottom bracket. On the right is a typical, much smaller, ball from a modern bottom bracket.

Bike makers now work around that problem with new standards that use bigger bottom bracket shells. For carbon frames, this works fine, since you have a lot of material in the BB region anyhow. A steel frame built to a ‘modern’ BB standard will be quite heavy, as the oversize bottom bracket shell adds a lot of material. Bottom bracket shells are the heaviest part of a metal frame, so keeping them as small as possible is useful for keeping the frame weight down.

And then there is the issue of the ever-changing standards, because none work as well as the old square taper. It didn’t come as a surprise when Allied, the US-based maker of high-end carbon frames, decided to return to the BSC/BSA bottom bracket standard. Their web site explains: “After more than a decade of changing bottom bracket standards, we are happily back to BSA. No more creaking, easy to service and just as light as any other bottom bracket standard. Your mechanic will thank you.”

Aren’t there performance advantages with bigger spindles? In theory, the bigger spindles are stiffer. In practice, all spindles are stiff enough. Your frame flexes far more than your bottom bracket spindle. The reason we haven’t done a double-blind test of crank stiffness is simple: It’s so pointless that it isn’t worth the effort. Eddy Merckx used square tapers, and so do the Japanese Keirin track sprinters. If they can’t flex them, neither can you and I! In fact, I’ve raced our square taper cranks in Japan’s toughest gravel race (above) – without any issues.

It’s only for mountain biking with its huge jumps – especially downhill – where the higher impact strength of larger spindles is useful. That is why we don’t recommend Rene Herse cranks for mountain bikes. On the road, cranks don’t fail due to impact, but they fatigue after many miles of use. To resist those forces, we forge our cranks. This aligns the grain structure to make them more resistant to fatigue.

We give a 10-year warranty on our Rene Herse cranks as well as on our SKF bottom brackets. Few makers are prepared to stand behind their products for that long. This illustrates how much confidence we have in our square tapers (and the rest of our cranks and bottom brackets). We’ve spared no expense to make them as good as they could possibly be.

Click on the links below more information:

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SKF Bottom Brackets Back in Stock


Bottom brackets are almost invisible, and you only notice them when something goes wrong. When the bottom bracket in my Firefly started to bind after just a few hundred miles, I put in an SKF, and that was the last I thought about it. When the bike was overhauled, the BB was spinning as smoothly as ever. That is how it should be!

How does the SKF last so much longer than other bottom brackets? SKF is a world leader in bearings, and they’ve applied all their technology to these bottom brackets. The two biggest advantages are larger bearings and better seals.
Let’s look at the bearing size first. SKF runs the bearings directly on the spindle and on the shell of the cartridge (above). That way, there is enough room for large ball bearings that can handle the high torque and low rpm of a rider’s pedaling, which is really tough on bearings. On the driveside (left side above), the SKF bottom bracket uses even stronger roller bearings to handle the extra force of the chain.

Most other bottom brackets use premade bearings (also called ‘cartridge bearings’ or ‘sealed bearings’), usually the 6903 size shown above. Using a premade bearing is much easier, as you don’t have to grind and polish the bearing seats. Instead, you simply press the bearing’s inner race onto the spindle and the outer race into the shell. The problem is that the extra bearing races waste space, and then you no longer have room for properly-sized ball bearings.

Bottom bracket shells were originally designed for cup-and-cone BBs that run the bearings straight on the spindle and the cups. They started with 1/4″ balls (6.35 mm) and sized everything up from there, without wasting a single millimeter. Most bottom bracket shells still are that size, even though cup-and-cone BBs now are rare.
When you use premade bearings, you lose about 1.5 mm on each side, plus a little bit more because the sleeve needs some room inside the BB shell. As a result, the largest balls you can fit are 2.8 mm in diameter, less than half the ‘normal’ size. These small balls have a much lower load rating, and they’ll also wear out faster.
The other big issue is that the premade bearings don’t have good seals. They are sometimes called ‘sealed bearings,’ but those black or red rubber seals are intended only as dust shields for indoor applications. They aren’t waterproof at all. You’ll never see a bearing like that exposed on a car, and yet even high-end bottom brackets put nothing but a rubber shield between your bearings and the gritty outside world.

The SKF bottom brackets have labyrinth seals that really do keep moisture out. Once, I cut open an SKF cartridge that I had used on my Urban Bike for a full year of rainy Seattle commutes, and the grease inside was fresh and clean. These seals are truly high tech, and SKF even patented them, because they were designed specifically for this application.

As a result of all this quality, we can offer these bottom brackets with a 10-year warranty that includes the bearings. (Actually, we limit the warranty to 10 years or 100,000 km, whichever comes first.) For most riders, one of these SKFs will be the last bottom bracket they install in their bike, and it’s certainly been that way for me.

SKF had stopped making these bottom brackets, and for a while they were unavailable. We are glad that we now can offer them again in all sizes, with British, Italian and even French threading, as well as in an ISIS version, as a world-wide exclusive from Compass Cycles. Click here for more information about SKF bottom brackets.

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ISIS Bottom Brackets

BXC-600
When we took over the distribution of SKF bottom brackets, we didn’t have high expectations for the ISIS bottom brackets. We were surprised when they became one of our more popular products. We sell them to customers who haven’t heard of Bicycle Quarterly, supple tires or any of the other things that we usually are associated with.
ISIS was an “open source” standard developed by a few of small makers – including Race Face and Truvativ – to counter Shimano’s proprietary Octalink interface. Shimano discontinued Octalink when the company began to attach the spindle to the right crankarm. Other companies followed suit, leaving ISIS as an orphaned standard.
ISIS made sense in theory, with a splined and tapered interface, but in practice, the large-diameter spindle left too little space for the bearings inside the standard BB shell. Most ISIS bottom brackets last only a few months in hard use.
SKFBB_Exploded
SKF got around this problem by running the bearings directly on the spindle and shell, which allows the use of much larger bearings. The drive-side bearings are roller bearings, which have very high load ratings. In fact, the bearings of SKF’s ISIS bottom brackets are exactly the same as those of their indestructible square taper bottom brackets.
In an odd twist of fate, we ended up with the only reliable ISIS bottom bracket on the planet. Instead of replacing bottom brackets after just a few months of service, riders now can rest assured that our 10-year warranty on SKF bottom brackets includes the bearings. If you have a cherished ISIS crank, these bottom brackets allow you to extend its lifespan for at least another decade. Most likely, this will be the last ISIS bottom bracket you’ll ever have to buy.
I am almost tempted to offer the René Herse cranks with an ISIS splined interface, now that there are reliable ISIS bottom brackets…
Click here for more information on SKF bottom brackets.

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SKF Bottom Brackets after 5 Years

SKF_urban_bike
It’s been five years since Compass Bicycles started selling SKF bottom brackets, and three years since we became the world’s exclusive distributor. At that point, we extended the warranty to 10 years, since we had great confidence in the quality of these bottom brackets. They have patented labyrinth seals, and their oversize bearings run directly on the spindle and shell. There was no reason to doubt the claim of the SKF engineers: These bottom brackets should last 100,000 km of rainy riding. Since most of us don’t ride in the rain all the time, they should last even longer in real life.
bb_SKFBB_seal_ph
Now the first bottom brackets that we’ve installed are half-way through their minimum expected lifespan. I am happy to report that they have proven as reliable as we had hoped. Both on our own bikes and on most customers’ machines, they simply do their job. Mark and I installed ours four years ago, and then forgot about them. They still spin as smoothly as they did on the day we installed them.
Out of several thousand bottom brackets sold, we’ve had fewer than a dozen warranty returns. Some were due to grit getting trapped in the outer seals. The seals did their job, and the contamination never reached the bearings, but the grit could be felt when turning the bottom bracket spindles by hand. While this isn’t a defect, we replaced the units for new ones.
bb_SKFBRC
There were three fluke failures, with the most bizarre coming from the rider who overhauled his bike, reassembled it, and the next morning, he found both cranks lying on the ground next to the bike. The spindle had broken on both sides! Since this was an ISIS “Mountain” bottom bracket, we replaced it with the “Freeride” version, which has a smaller hole in the spindle, and thus much stronger spindle. Considering the huge loads a bottom bracket undergoes, this rate of warranty returns is extremely small. It confirms that the confidence we placed in these bottom brackets has not been misplaced. We look forward to the next five years of selling and riding with these bottom brackets.
SKF bottom brackets are available with JIS and ISO tapers, as well as for ISIS cranks. They come in BSC, Italian and French threading. Click here for more information.
 

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SKF Bottom Brackets with French Threads

Singer1985full
Many wonderful bikes have been made in France in past decades. Not just the great machines from small constructeurs like René Herse and Alex Singer (above), but also more common bikes like the Peugeot PX-10, the nicer Gitanes and many others. High-end French bikes often used relatively lightweight tubing and a geometry with relatively low trail, which made them perform and handle very well.
The only “problem” with many French bikes is that they use metric threads and dimensions. Even though the world has adopted the metric system (with the exception of one rather large country), the bike industry has standardized on British units for most components.
This means that finding parts for French bikes can be difficult. For stems, the difference is small (22.2 vs. 22.0 mm). You can lightly sand a modern stem, and it will fit into the steerer tube. Seatposts and derailleurs don’t wear out quickly, and used parts can do the job. That leaves bottom brackets as a major problem. The days when Campagnolo, Shimano, Edco and many other companies made high-quality French-threaded bottom brackets are long gone.
bb_SKFBRC
To alleviate this situation, we now offer SKF bottom brackets with French threading. There is a small upcharge, because they are made in very small production runs. Like all SKF bottom brackets, the French versions carry a 10-year warranty that includes the bearings. All square-taper spindle lengths are in stock now in British, Italian and French threading. Click here for more information.

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Bottom Brackets Demystified

SKFBAS-600
Replacing a square taper bottom brackets can seem a bit daunting. What threading do I need? How long should the spindle be? Which taper? It’s really quite simple, and here is how to figure it out.

Threading

The bottom bracket screws into your frame. If your frame was made in the last 15 years, the threading is most likely British (also called BSC or BSA). It’s easy to check: British threading uses left-hand threads on the drive side.

Older Italian frames and some Italianate North American frames used Italian threading. Those use right-hand threads throughout. French frames before about 1985 often used French threading, which also has right-hand threads on both sides.

Key rule for threading: If the drive-side has left-hand threads, it’s British. If both sides have right-hand threads, then it depends on whether your frame is French or Italian. (If your frame is Swiss, then you may have the rare Swiss threading, which also has left-hand threads on the right side.)

You cannot easily convert your frame to a different threading, so make sure you get this right.

chainline

Chainline

The chainline is the centerline of the chainrings in relation to the centerline of the bike (above). For a double, it’s measured in the middle between the two rings, for a triple on the middle ring. On the rear, the chainline is measured in the middle of the freewheel/cassette.

For most of the 20th century, the chainline on road bikes used to measure 43.5 mm. These days, it’s a bit wider, usually around 45 mm. This ensures that different cranks, cassettes, and frames are compatible.

The chainline isn’t set in stone. Sometimes, makers fudge by a millimeter or two. Triple cranks often use a slightly wider chainline. Some bikes with bowed chainstays to clear extra-wide tires also need to move the cranks outward a bit. However, this means that you will be “cross-chaining” when riding in the big ring and on the larger cogs of the rear cassette. The more severe angle of your chain increases drivetrain wear and noise. It also can lead to poor shifting. This is one of the reason why manufacturers have gone away from triples and prefer compact doubles.

Spindle Length

Since your chainline is constant, your bottom bracket spindle length depends only on your cranks, not your frame (with the exceptions noted above). Depending on the crank design, the spindle length can vary.

Here two examples: A 2007 Campagnolo Record double cranks uses a 103 mm spindle. A TA “Pro 5 vis” uses a 118 mm spindle. Both result in the same chainline of 43.5 mm. How can this be? The Campagnolo crank has curved arms that move the spindle sockets inward. The straight arms of the TA cranks require a longer bottom bracket spindle.

The best way to find out which spindle length you need is by looking up the specs. (The alternative is trial and error…)

Spindle length and the resulting chainline have some leeway. If you are within 2-3 mm of the “correct” 43.5 mm or 45 mm, you are doing quite well. So if you really “need” a 118 mm spindle, but only can find a 121 mm, that isn’t a big deal. It just moves your chainline outward 1.5 mm. (The difference is split between both sides.) A slightly shorter spindle usually is OK as well, but check your clearances before deciding to move your cranks inward. Do you have enough room not only for the crankarms, but also for the chainrings (see drawing above)?

Symmetric spindle?

On racing bikes with relatively large “small” chainrings, you need extra clearance on the driveside, so the small chainring doesn’t hit the chainstays. With a triple, you need even more, because you have the small chainring bolted to the inside of the crank.

To accommodate this, many older bottom brackets have asymmetric spindles. The right side is a few millimeters longer than the left side. This lowered the tread (Q factor) by a few millimeters compared to a symmetric spindle, but it also meant that you sat a little lopsided on your bike. The asymmetry is small compared to the length of your legs, and few riders ever notice this.

Today, most bottom brackets today have symmetric spindles. You can use a small spacer under the right-side cup to create an asymmetric bottom bracket. SKF bottom brackets are designed to be symmetric, but we offer spacers that allow moving the spindle a bit to one side.

Taper

We’ve determined which threading and which spindle length we need. There is one more thing to consider: the taper of the spindle ends determines which crank fits onto your bottom bracket. There are two common tapers:

  • JIS: The old French standard, copied by the Japanese. Most Japanese cranks (but not all) and most older French cranks use this taper. René Herse cranks (new and old) use this taper.
  • ISO: Campagnolo and many European makers, as well as a few high-end Japanese cranks, use this standard.

ISO and JIS are very similar – the angle of the taper is the same, but the ISO spindle ends are a little slimmer. In a pinch, you sometimes can use a JIS spindle with an ISO crank. To compensate for the wider JIS taper, select a spindle that is about 1-2 mm shorter. The other way around doesn’t always work: A slim ISO taper can extend all the way through the larger hole of a JIS crank, so you cannot tighten the crank.

To summarize: When you specify your bottom bracket, you need to know:

  • The threading of your frame: BSC, Italian, French (or Swiss).
  • The taper of your cranks: JIS or ISO.
  • The length of your spindle in millimeters, depending on the type of crank you use.

With those three factors, you can order your bottom bracket and be confident that it fits. For further information, check out Rene Herse Cycles Bottom Bracket Compatibility Chart (pdf file).

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Silver Cups for SKF Bottom Brackets


More than three years after their introduction in North America, the SKF bottom brackets have lived up to their promise as the most reliable bottom bracket on the market. Many have been ridden for tens of thousands of miles in all kinds of weather. Each bottom bracket carries a 10-year warranty that includes the bearings, yet we have received fewer than a handful of warranty returns. This truly is a component you can install and forget.
The only concern some riders have had is a color issue: The models with the JIS taper are equipped with a left-side cup that is anodized red, which can clash with some paint colors. (I like the contrast on my dark blue Urban Bike shown above.) The right-side cup is part of the BB assembly and always finished in silver.

Fortunately, we have been able to obtain a small quantity of black and silver cups. When you buy an SKF bottom bracket, we will substitute the red cup for black or silver upon request. There is an upcharge for this ($ 7 for black, $ 10 for silver). We also offer replacement cups ($ 12 for red, $ 15 for black, $ 18 for silver).

We want you to be as happy with the appearance of your bottom bracket as you will be with its function.

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To grease or not to grease?


Should one grease the tapers of bottom bracket spindles before installing the cranks? Few topics spur as much controversy among bike mechanics as this question.
In the old days, Campagnolo not only recommended mounting the cranks dry, they even suggested degreasing the tapers. The concern was that grease might facilitate the crank slide up further and further on the tapers. And since many of us learned about bicycles when Campagnolo was the undisputed king of components, the word from Vicenza was treated as gospel.
More recently, I worked for Race Face as a technical writer and translator, and  their engineers disagreed. They advised: “Grease the tapers, but make sure you only tighten the bolts once, then leave them alone.” Their tests had shown that a “dry” spindle/crank interface did not result in a consistent press-fit between the parts.
As we developed the new René Herse cranks, we discussed this topic without coming to a conclusion. In the mean time, our engineer mounted the first test cranks without grease, and found that they had unacceptable levels of runout of the chainrings – the chainrings didn’t run as true as we would have liked. (“Unacceptable” means that the runout was visible even if it did not affect the function or performance.) When the runout changed each time he mounted the cranks, we realized that the cranks were not seating uniformly on the taper.
What exactly was happening? Imagine the crank and spindle surfaces as tectonic plates that slide past each other as the crank bolts are tightened. If you grease the interface, they will slide smoothly until you stop turning the bolt when it is tight. If the interface is “dry,” the crank catches on the spindle. This builds up tension, which then is released in an “earthquake.” Even with the same torque, the crank will sit differently, depending on whether the tension has been released or not, before you stop turning the bolt. With grease, the crank’s position was more uniform, as the crank slid smoothly onto the spindle.
What about the crank arms “migrating” further and further onto the spindle each time you mount the cranks? To test this, we mounted a René Herse crank, tightened it to 25 Nm (the recommended value), then took it off, mounted it with 30 Nm … we repeated this 5 times, increasing the torque by 5 Nm each time until we reached 50 Nm. The goal was to find out when the crank would be destroyed. To our surprise, the crank did not move any further onto the spindle. We could not destroy the cranks in this way. A 1990s Campagnolo C-Record crank that we tested for comparison slid further and further onto the crank. We stopped the experiment early to avoid breaking the classic Campagnolo crank.
The difference between the two cranks appears to be that the new René Herse cranks have a forged taper. This makes that part of the crank assembly much stronger. The C-Record crank appears to have a machined taper. Every time the crank gets mounted on the spindle, the aluminum moves – in fact, mounting the crank acts in the same way as a forging process. It is likely that this process would stop eventually, but I’d rather not experiment with a classic crank.
So for our René Herse cranks, we recommend that you lightly grease the crank spindle. Also grease the treads of the bolts, but not the underside of the bolt head. (The underside of the bolt head should interlock with the crank, so it doesn’t come loose.) Then tighten the bolts to 25 Nm. That is it. If you like, you can check after your first ride that the bolts are tight. Thereafter, leave them alone.
Crank bolts can loosen over time, but that does not mean that you should re-tighten them. Instead, remove your cranks every couple of years and inspect them for cracks. (You should do this with all cranks, no matter the brand.) Then put them back on, and enjoy them some more. Treated like this, quality cranks will last most riders for many decades.

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SKF Bottom Brackets: World Exclusive


Compass Bicycles is proud to be the sole distributor of SKF bottom brackets world-wide. Svenska Kugellagerfabriken (SKF) has been the leader in bearing technology since 1907. Today, SKF is the largest bearing manufacturer in the world, and their bearings are used in Formula 1 racecars and other high-end applications.
SKF’s ball bearings have been used on many of the best bicycles. Campagnolo’s famous ball bearings were made by SKF. Starting in the 1940s, Alex Singer and René Herse equipped their custom-made bottom brackets with pressed-in SKF cartridge bearings, because they were the best available.

When SKF decided to make bottom brackets, using the highest-quality bearings was a given. Bearings run smoothly only if they are kept clean and well-lubricated, so the company developed and patented custom seals that keep the grease in and contamination out. SKF designed the bottom brackets as completely integrated units. By running the balls and rollers directly on the spindle and shell, the design saves valuable space, allowing the use of larger bearings for greater strength and durability.
Why is this such a big deal? Many other high-end bottom brackets use standard bearings pressed onto the spindle and into the shell. There is only so much space inside a bicycle’s bottom bracket shell, so the ball bearings have to be much smaller (usually 2.8 mm diameter vs. 4.5 mm on the SKF). And many expensive bottom brackets don’t use any seals, relying on the dust seals of the bearings to keep them clean. These dust seals aren’t designed to keep out water… and they don’t. As a result, riders who ride through rain and snow have to replace their bearings annually.
SKF wanted to design a bottom bracket with a maintenance-free life expectancy of 10 years or 100,000 km (65,000 miles) under harsh conditions, so they had to address these concerns. They also made all parts from stainless steel or aluminum, so corrosion is not an issue.


With such an excellent product, SKF did not anticipate the difficulty of selling their bottom brackets. Without their own access to bicycle shops, the company relied on a variety of distributors world-wide, who often buried the bottom brackets deep in their catalogues. Without adequate promotion, sales lagged behind their targets.
When we heard that SKF might stop selling their bottom brackets, we offered to distribute the bottom brackets for the company. SKF bottom brackets will remain available directly from Compass Bicycles and through our network of quality bicycle shops. We are committed to keeping all available sizes in stock at all times. Below, you see our latest shipment from Germany as it arrived…

To reflect the superior quality of SKF bottom brackets, we have extended the warranty to 10 years or 100,000 km (65,000 miles), whichever comes first. This warranty includes the bearings. (We are unaware of any other maker of bottom brackets whose warranty includes the bearings.) We are confident that these are the best bottom brackets ever made, and we are proud to make them available to cyclists world-wide.

We now offer the Park BBT-18 installation tool, because it is important to use the correct tool when installing these bottom brackets. We aren’t making money on the tools (we sell them at a discount), because we want you to be happy with your SKF bottom brackets!

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