Can I use a 68mm bottom bracket in a 73mm shell?

Multiple spacers are included in order to fit both sizes meaning if you see a BB for sale that says 68/73 it means it will fit both but it includes a couple spacers in the box to make it fit the 68, those spacers (or fewer of them) are not needed if the shell is 73mm wide.

Can you put a 68mm bottom bracket in a 73mm shell?

Is it ok to use a 68mm external (hollowtech II) BB in a 73mm shell? Yep, but ignore the advice above and use one spacer.

Are all bottom bracket shells the same diameter?

Generally, your replacement cranks may have the same or smaller spindle diameter, and the same or longer spindle length than the system your bottom bracket is designed around. For example, a BB30/PF30 bottom bracket has the narrowest shell width of any of the standards, whilst being designed for large 30mm spindles.

How do I know what size bottom bracket I need?

To find out the size of bottom bracket needed, measure the inside of the bottom bracket shell in your frame, it will be 73mm, 70mm or 68mm. Some older frames may have Italian threaded bottom brackets, instead of the more modern English.

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.

What is 68mm bottom bracket?

The width of a BB30 bottom bracket is 68mm or 73mm. On road bikes, it's always 68mm. With mountain bikes, 68mm is most common too, but sometimes the wider version with 73mm width can be found. The diameter of the bottom bracket is 41.96mm, and the bottom bracket bearings are always pressed into the frame separately.

Are bottom brackets interchangeable?

Threaded bottom brackets shells have been made over time in various thread standards that are not interchangeable. The common threaded bottom bracket uses cups or adaptors with the thread specification of 1.37″ x 24 threads per inch (approximately 34.8mm diameter).

Does bottom bracket spindle length matter?

The critical thing is your spindle length: as long as you can set up the correct chainline you will be good to go. But, again, best never to mix standards if you can at all avoid it. If you are looking to replace a cottered crank setup with a square taper setup, then look no further than a cartridge bottom bracket.

How is bottom bracket shell width measured?

Measure the inner diameter on the side of the bracket's shell.

1. If the inner shell diameter is 1.37 inches (35 mm), you have an English bracket. ...
2. On a BMX bike, this measurement will typically be either 19 mm or 22 mm.
3. This measurement will be the same on both sides; don't bother checking the width on each side.

How many spacers does a 73mm BB have?

For 73mm Shimano HTII bottom brackets

If your bottom bracket shell is 73mm wide, you only need one 2.5mm spacer fitted to the drive side.

How do I determine bottom bracket spindle length?

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.

How do I know what size crankset to buy?

Crank length is measured from the centre of the bottom bracket axle to the centre of the pedal axle. If you're not sure what length the cranks on your bike are, the quickest way of finding out is typically to just look at the backside of your cranks, just below the pedal axle.

What length spindle do I need?

If you have a Mid or a Spanish BB on your BMX Freestyle bike, you need the 5 5/8″ spindle. If you have an American BB on almost any style of frame, you need the 5 5/8″ spindle. If you are using the Outboard BB and the Spline Drive Sprocket, and you BB shell measures 68mm wide, you need the 5 5/8″ Spindle.

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.

Is hollowtech better than square taper?

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

How do I know if my crankset is compatible?

In most cases three-and two-piece cranksets are compatible with the same bottom brackets so long as the axle is the same diameter. They are commonly used in conjunction with the mid-style bottom bracket standard. One-piece: This is where the axle and crank arms are a single piece of steel.

Can I put any crankset on my bike?

Cranksets are not always interchangeable. Every crank is designed to work with a specific bottom bracket. Even if the cranks use the same interface (octalink, square taper, or hollow tech), switching them between bike brands or even models of the same brand is hard.

What is the difference between English and Italian bottom bracket?

The key difference is in how the two thread into the bottom bracket shell. Like pedals, one side of a BSA standard bottom bracket shell is reverse (left) threaded, while both sides of an Italian standard bottom bracket shell are regularly (right) threaded.

Are bicycle bottom brackets universal?

Whichever type you choose – or are obliged to stick with – make sure you choose the correct width to fit your BB shell. These are generally 68 or 73mm wide on MTBs, or 68/70mm on road bikes although again this is not such a consideration with press-fit BBs (of which, more below).

What does the 90 in BB90 refer to?

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.

What is the difference between BB30 and BSA?

BSA is English standard and have screw thread inside the hole ,usually use in shimano,while BB30 is Italian standard and don't have screw thread, usually use in CP.

What's the difference between 170mm and 175mm cranks?

Macdermid found that riders reached their peak power nearly 1 second quicker on 170mm cranks than they did on 175mm cranks. That means shorter cranks give riders better acceleration, which can make a difference when passing other riders or trying to clean an obstacle.

Will shorter cranks help my knees?

Pain is relieved. Just by installing shorter crank arms, without any other adjustment, the knee at maximum flexion is lowered by 7.5 mm. That difference provides approximately 3° to 4° of relief.

Are shorter cranks better?

Going to a shorter crank will allow you to ride at a lower back angle which minimizes frontal surface area improving aerodynamics. It can be frustrating to know that there are many available crank options that would work for an athlete.