Wheels mfg Bottom Brackets

New 30 mm Bottom Brackets — Now in 7 Bright-Dip Colors You asked, we listened. We’re launching four 30 mm bottom bracket styles in Red, Orange, Pink, Teal, Blue, Purple, and Green. All are CNC-machined from 6061 aluminum and fitted with our stainless-steel ABEC-3 bearings. Styles T47 Internal (30 mm) T47 Outboard (30 mm) PF30 Outboard (30 mm) BSA Threaded (30 mm) MSRP: From $100 to $124 Shop Now

What is GXP? We’ve been getting a lot of questions about GXP, so here’s a quick primer. GXP stands for Giga X Pipe, originally developed by component maker TRUVATIV (acquired by SRAM in 2004). SRAM adopted the standard across many of its cranksets. What makes GXP different? Shimano Hollowtech II and SRAM GXP both use external bottom bracket bearings with a smaller-diameter spindle than 29/30 mm systems. The key difference is spindle diameter: Hollowtech II uses a constant 24 mm spindle across its length. SRAM GXP uses a tapered spindle—24 mm on the drive side to 22 mm on the non-drive side. The taper is on the splined portion of the spindle, not the smooth center section. Different spindles mean different bearings Hollowtech II: 24 × 37 × 7 mm bearings on both sides. GXP: 24 × 37 × 7 mm (drive side) and 22 × 37 × 8 mm (non-drive side). With a constant 24 mm spindle you can often adjust chainline with crank spindle spacers (the spindle slides through both bearings). With GXP, the taper bottoms on the non-drive bearing, so moving the crankset inboard typically requires bottom bracket cup spacers. Bottom line: GXP’s 24 → 22 mm taper is the defining feature. When in doubt, measure—correct spindle and bearing sizing makes all the difference.

Asymmetric Bottom Brackets BB30A/PF30A As if the current crop of bottom bracket standards weren’t confusing enough both shop mechanics and consumers now must contend with even muddier waters in the form of “Asymmetric” bottom bracket shells. Simply defined an asymmetric bottom bracket shell is not identical on both sides of the frame’s center line. Among the companies using these types of shells is Cannondale. In addition to using the BB30 & PF30 standards they now bring us BB30A & PF30A. The new “standards” widen the bottom bracket shells, but unfortunately, it’s not as clear cut due to where they add the extra material. Let’s take a closer look. The dimensions of a BB30a shell are an inner diameter of 42mm and a shell width of 73mm, while the PF30a standard uses the same shell width but an inner diameter of 46mm. This is not quite as straightforward as it seems though. The extra 5mm when compared to a standard 68mm shell gets added just to the non-drive side, giving us a bottom bracket shell (when measured from the centerline of the frame) 34mm drive-side, 39mm non-drive side. The problems happen when you’re trying to use a Shimano or SRAM GXP crank. Non-BB30 cranksets were designed around outboard bearing bottom brackets and their spindle lengths are calculated based off this type of bottom bracket. This is related to a measurement called “Over Bearing Width” (OBW), which is defined as the width of the bearings with dust shields placed over the bearings. For example, the over bearing width of our BB30-OUT/PF30-OUT bottom brackets installed in a traditional 68mm BB30 or PF30 frame would be 90.5mm. The “Over Bearing Width” is directly related to another measurement we can call “Practical Spindle Length” which is the available spindle length when measured between the inside faces of the crankarms, illustrated in the photo below. In the case of a standard Shimano Hollowtech 2 or SRAM GXP spindle this measurement comes out to right around 93mm. Comparing this measurement against our 90.5mm OBW and there is plenty of room to install the crank. Things change when we attempt to install these same cranks using the previously mentioned BB30a/PF30a outboard bottom brackets in a frame with a 73mm shell. In the wider frame shell, our OBW moves out to 95.5mm leaving our “practical spindle length” 2.5mm too short. If the bottom bracket was symmetrical this would be a simple problem to solve, just reduce the OBW by moving the bearings further inboard, but with the asymmetric bottom bracket shell it’s not quite that simple.  While moving the bearings in solves the problem with spindle length it creates problems with chainline and chainring clearance. Since the bottom bracket shell is asymmetric it’s necessary to move the bearings inboard on just the non-drive side as seen in the photo below. By moving the non-drive side bearing further inboard we reduce the OBW to 91mm in a 73mm shell width while preserving chainline and chainring clearance on the drive-side. So, there you have it, a quick primer on the BB30a/PF30a standards. As we mentioned in previous articles, with any bottom bracket questions don’t rely on what it’s called, get the dimensions of the frame shell and spindle length then go from there. Always remember that unless the frame in the stand is a Cannondale you won’t need a Bottom Bracket with an “A” in the description. As of this writing Cannondale is the only manufacturer using the BB30A/PF30A system.

What is a T47? Many might wish it to be a new experimental jet fighter. Instead, it is yet another bottom bracket standard. Launched in 2015 as a cure for the most common complaint of the press-fit systems: the dreaded creaky bottom bracket. In this article we’ll look at some of the characteristics of the T47 system. Think of T47 as a larger version of traditional, and well-loved BSA threaded BB shells. T47 bottom bracket shells actually start life as standard 46mm inner diameter shells and are then threaded to M47x1.0mm. Much like a BSA shell, the right, or drive side, of the shell is left hand thread, and the left side, or non-drive side, of the shell is right hand thread. Inside Tip: If you have a customer with a creaky metal PF30 or 386EVO frame you may be able to run T47 taps through it and install a more secure T47 bottom bracket. T47 is Secure A potential problem with press fit systems is the interface between the frame’s bottom bracket shell and the bottom bracket cups themselves. With metal frames such as steel and aluminum, BB shell tolerances should be held accurately by using cutting tools post welding and fabrication. A reamer and facing tool should create a perfectly round and faced BB shell. However, with carbon BB shells, once the carbon is set you are at the mercy of the layup job. On a carbon frame, you can't use a bottom bracket reamer and facer to precisely set the BB shell bore diameter and trueness. The end result is a carbon BB shell that fails to hold the cups secure in the frame. BB cups that move in a frame are going to make noise. Threaded fasteners have been around for over 2,000 years. They are a proven system of securely holding parts in place. This has been proven with traditional BSA threaded bottom brackets. Having one set of threads as a permanent part of the bottom bracket shell allows for the BB cups to be tightened directly into the frame, preventing any type of movement. No movement of the cups means no creaking. T47 is Adaptable Another advantage of the T47 is it’s adaptability to different crank spindle diameters and frame widths. With larger cups, T47 can accommodate bearings compatible with 30mm spindle cranks, 29mm DUB, 22/24mm GXP and 24mm Shimano crank spindles all while giving you the option of either inboard or outboard bearing configurations. Press-fit systems have evolved over the past few years to include shell inside diameters as small as 37mm. These small diameter press-fit shells are not ideally suited for today's larger diameter cranks. Because each cup independently threads into the frame, T47 cups can be used on any width bottom bracket shell from 68mm to 132mm wide. The determining factors for which T47 bottom bracket cups to use are the width of the shell and the length of the crank spindle. For more information on how to determine the proper T47 bottom bracket for a frame, click HERE. T47 is Stiff The bottom bracket junction comprising the seat tube, down tube and chain stays is a key part of a frame’s stiffness. Bottom bracket shells with smaller inner diameters such as BB86 generally have to resort to wider bottom bracket shells and beefier tubes to achieve what the PF30 (46mm) starting platform can do with smaller diameter tubing. Because a T47 shell starts with a 46mm inside diameter, and has no width restrictions, frame builders have a rather large platform to build up the bottom bracket area of the frame the best way they see fit to achieve their frame's performance goals. T47 is Here to Stay While it has taken a few years for T47 to gain acceptance, we have seen a steady increase in small and custom builders choosing to build frames with it. Especially common on many custom titanium and steel frames, there are also a few brands using aluminum T47 shells in carbon frames (Rodeo Labs, Ibis). The most exciting development is that Trek has begun to build frames with T47 shells. The 2020 Domane frames are built around T47 shells, some of them shipping with Wheels Manufacturing BBs installed.

In 2018, SRAM introduced mountain bike cranksets which use a new technology name DUB™ (Durable Unified Bottom Bracket). Meant to simplify frame BB and crankset compatibility across their product lines, it brought about yet another standard to understand. In 2019, SRAM began rolling out DUB cranksets on their road cranksets. Once the SRAM road cranks went to DUB™, Wheels Manufacturing began producing a full line of DUB™-compatible bottom brackets. There are two key features that directly relate to Wheels Manufacturing bottom brackets. The most significant feature is DUB™ cranksets use a 29mm diameter spindle, and therefore require specific bearings with a 29mm ID. We are currently shipping our DUB™-compatible BBs with Enduro 6806/29 ABEC-3 bearings. These have dimensions of 42mmx29mmx7mm. The bearings are matched to 29mm ID dust seals, and all Wheels Mfg DUB™-compatible bottom brackets include 29mm ID spindle spacers. The second feature is SRAM DUB™ cranks come in only a few spindle length options. No more spindle lengths for use in 68mm or 73mm wide BB shells with internal bearings. In fact, the surface of the spindles are machined so that they will not work in bottom brackets with overall bearing widths less than 79mm. For frames with a BB shell width less than 86mm, you will most likely need to use a DUB™-compatible BB with external bearings.

New frames and cranksets are released every season, and with these changes come new bottom bracket "standards". We once had a particularly frustrated shop mechanic tell us: "Something should be around longer than a week before they start calling it a standard!". While we tend to agree, it’s the reality of the bike industry. One of the most common issues we see is mechanics relying on the names of bottom brackets to identify which bottom bracket is right for a frame, rather than relying on measurements they take. Below we discuss some of the common pitfalls of relying on bottom bracket naming conventions only, and we hopefully clear up the three most common misconceptions about bottom brackets we see.   BB30 & PF30 While BB30 and PF30 frames have been around for a few years now, there are still many misconceptions surrounding them. Strictly speaking both are "press-fit" systems because neither one uses a traditional threaded bottom bracket shell, and they both were originally designed for cranksets with 30mm diameter spindles. However, this is where the similarities end. The BB30 system is a "direct-fit" bearing system where the outer race of the bearing directly contacts the frame. A BB30 bottom bracket simply consists of two 6806 bearings pressed directly into the bottom bracket shell of a frame with a 42mm inside diameter and usually employing 2 retaining clips to set the depth of the bearing. You can learn more about the BB30 bottom bracket technical specifications HERE. A PF30 frame has a shell slightly larger than BB30 (46mm compared to 42mm). The bearings are pressed into cups which are then pressed into the frame. In the case of the PF30 systems the bearing cups rely on flanges to ensure that both cups are pressed the proper depth into the frame. You can learn more about the PF30 bottom bracket technical specifications HERE. Adding to the confusion between the two standards is that many frame manufacturers do not publish the dimensions of their bottom bracket shells. They may publish the crankset shipped with the bike, but that doesn't tell us what shell is in the frame. Cannondale takes it a step further by putting a BB30 sticker on their frames regardless of it has a BB30 or PF30 system! So, it’s always best to rely on measurements. Yes, you may need to remove the crankset to do this, but better than guessing wrong. You can also contact your frame manufacturer who should be able to give the exact BB shell dimensions.   BB86/92, BB90/95 & PF92 BB86/92 and Trek's BB90/95 are often misidentified. While the "30" in BB30/PF30 references the inside diameter of the used, the numbers in BB86/92 and BB90/95 refer to the width of the frame's bottom bracket shell. The BB86/92 bottom bracket system uses a bearing pressed into a cup, which is then pressed into the frame. BB86 and BB92 bottom bracket shells always have an inside diameter of 41mm and a commonly used width of 86.5 or 92mm, but can be found in shells up to 132mm wide. More on the BB86/92 standard can be found HERE. The BB90/95 bottom bracket standard found on various Trek models is like the previously discussed BB30 system in that it is a "direct-fit" system. The frame's bottom bracket shell inner diameter is 37mm. A bearing with an OD of 37mm is pressed directly into the frame. Trek is moving away from the BB90/95 system to what they call PF92, which is the same as a BB92 (41mm ID shell and 92mm width). Again, we recommend taking inner diameter and width measurements on the frame to determine exactly what standard the frame has. More on the Trek BB90/95 standard can be found HERE.    Specialized OSSB OSBB is an acronym for "Oversized Bottom Bracket" used by Specialized. The problem with this term is "How oversized is Oversized?". In comparison to the previously discussed bottom brackets standards, this term gives us no dimensions to work with. OSBB has been used to describe frames with 42mm and 46mm diameters. Specialized frames with a carbon fiber shell construction are usually 46mm inner diameter (Carbon OSBB), and can have a width of 61mm (road), 73mm (mountain) and 83mm (downhill). Frames with aluminum BB shells (Alloy OSBB) have an inside diameter of 42mm and a widths of either 68mm (road) or 84.5mm (mountain). Specialized often simply uses the term OSBB for each frame. If you are trying to fit a bottom bracket in a Specialized, best that you measure the frame, or contact Specialized directly for exact measurements.   As we've detailed here, relying on names and terms to identify bottom brackets can be confusing at the least, and misleading at the worst. Relying on good solid measurements can make navigating the minefield of bottom bracket standards a lot easier. So, one word of advice when trying to identify a frame's bottom bracket standard it would be, always measure the frame, don't assume it is one particular standard.