Nederlands | English | Deutsch

Project Sports

Questions and answers about sports

Are Shimano Hollowtech II bottom bracket spacers unique?

5 min read

Asked by: Courtney Scott

Are bottom bracket spacers necessary?

Much like GXP, you don’t need to add any spacers to the bottom bracket if you have a 73mm shell, but you will need to add a 4.5mm spacer to the right-hand side of the crank axle, unless you’re using a chain guide, in which case a 2mm spacer is required instead, along with a 2.5mm spacer on the right-hand side of the

Do Shimano cranks need spacers?

Mountain bike crank spindles are for 73mm frames, so they need spaces for 68mm frames. Shimano road crank spindles are for 68mm frames. A BSA (normal British threaded) bottom bracket, doesn’t need any spacers, you just thread the cups on and then put the cranks in.

What size is a Shimano Hollowtech II bottom bracket?

24mm Diameter Axle And Bearings



The diameter of the Bottom Bracket axle and bearings was of primary importance for the development because the Bottom Bracket axle area is tied to such key elements as stiffness, strength, weight and rotating performance.

How do you fit a hollowtech 2 bottom bracket?

Quote from video: Place the required o rings on the spindle. Next apply lubricant to the thread in the frame of the bank. Slide the bottom bracket into the frame and thread it into place in a counterclockwise.

How many spacers should a crankset have?

If your BB shell width is 68mm wide then you need three 2.5mm spacers to properly align your BB/crank and get a proper chainline (two on the left side and one on the right). If your BB shell is 73mm wide you need one 2.5mm spacer (on the right) to properly align your BB/crank.

How do you use bottom bracket spacers?

Quote from video: All you do is you put one spacer. On the chambering side on the drive.

What is a 68 73 bottom bracket?

The 68mm and 73mm dimension measure the width of the bottom bracket on the frame of the bike with no BB installed, simply the width of the shell. Most road bikes that use a threaded bottom bracket measure 68mm wide and most cross country/trail mountain bikes measure 73mm.

How many spacers does a GXP bottom bracket have?

two spacers

Each GXP bottom bracket comes with two spacers. For SRAM the following rule applies: 68mm bottom brackets need one spacer left and right, 73mm bottom brackets don’t need any spacers.

How do you install a Shimano bottom bracket?

Quote from video: The chain around the bottom bracket shell then push the drive side axle through the bottom bracket push. The non-drive side crank on to the axle perpendicular to the drive side crank push.

Which is better square taper or hollowtech?

Hollowtech is a bit stiffer and easier to take apart, but square taper will last much longer.

When did hollowtech 2 come out?

Shimano’s Hollowtech II cranks, unveiled in 2003, essentially ushered in the current era of crank design by integrating the axle into the design of the crank. From that point on, the weight, stiffness and reliability of cranks improved, plus, they were easier to install and service.

How many miles should a bottom bracket last?

As for a bottom bracket, on the low end, maybe 5000 miles. The basic Shimano one most people use (UN51/55/similar) can reasonably expect 10k+ miles. But sometimes you get unlucky and get a bottom bracket that lasts maybe 500 miles.

What is a dub crankset?

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.

How do you tighten a dub bottom bracket?

Quote from video: Use a two millimeter hex wrench to tighten the bolt until the adjuster edges touch.

How do you measure chain lines?

Quote from video: Here I measure from the outside face take the number I go from the outside face of the small ring I take that number add the two together divide. It in two that gives me the middle.

Is the bottom bracket sleeve needed?

It really depends on the design of your frame. If there is a hole in the BB shell where the seat tube is, it’s possible for water/moisture to get in the bottom bracket shell and cause problems with you bearings. Most carbon frames do not have any holes in the BB shell so it’s not needed.

How many spacers does a GXP bottom bracket have?

two spacers

Each GXP bottom bracket comes with two spacers. For SRAM the following rule applies: 68mm bottom brackets need one spacer left and right, 73mm bottom brackets don’t need any spacers.

What is a 68 73 bottom bracket?

The 68mm and 73mm dimension measure the width of the bottom bracket on the frame of the bike with no BB installed, simply the width of the shell. Most road bikes that use a threaded bottom bracket measure 68mm wide and most cross country/trail mountain bikes measure 73mm.

Why is bottom bracket important?

The bottom bracket is a critical component to every drive train. Connecting the left and right cranks, this is one of those important elements on the bike that directly effects power transfer between the rider’s legs and the bike’s drivetrain.

Does changing bottom bracket make a difference?

(Click here to read BikeRadar’s complete guide to bottom brackets.) According to Friction Facts’ latest report: “No statistically significant difference exists showing a general advantage or disadvantage of a standard type under similar loading conditions.

How long does a bottom bracket last?

They are still in use and come stock on many bicycles, especially lower end ones. These bottom bracket units can actually be pretty sturdy and can last for years or decades and the user pretty tosses in a new one when it seizes up in a rainstorm.