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How do you measure a rear axle on a bike?

Author

Emma Payne

Published Mar 17, 2026

How do you measure a rear axle on a bike?

For a front thru-axle, this is measured from the inside to inside of your fork. For a rear thru-axle, this is measured from the inside to inside of your frame at the drop-outs. The O.L.D. measurement is listed for many thru-axles, but isn't necessary if you know the overall length.

Consequently, what is a thru axle on a bicycle?

With a through axle, there is simply a hole on either side, instead of a slot. You remove the axle entirely out the side of the hub in order to remove the wheel. Typically, through axles are much thicker axles. The thicker axle is stronger and stiffer.

Also Know, how do you measure a rear end width? How to Measure Rear End Width

Locate the axle flanges on either side of the rear axle. The flange is the platform on which the wheels are mounted and bolted to the axle.
Using a measuring tape, measure from one flange to the other. To ensure an accurate measurement, always measure from end to end where the wheels bolt on to the axle.

Then, what size are bike axle nuts?

Bicycle Industry Threads

Nominal Thread Size	Example of Bicycle Uses
9mm x 26 tpi	Front hubs, Campagnolo®
3/8 inch x 24 tpi	Some solid axle bike, including coaster brake
3/8 inch x 26 tpi	Solid rear axle
10mm x 1mm	Most quick release rear axles, derailleur mounting bolts, brake lever adjusting barrels

How is differential size measured?

Measure the ring gear diameter. The ring gear is the largest gear inside the differential housing and normally faces the driver's-side rear wheel. Using a tape measure or machinist's ruler, measure the ring gear diameter. This identifies the differential -- a Ford 9-inch or GM 7.5-inch -- for example.

Are all bike hubs the same size?

Bike hubs at a glance:

Rear hub width varies widely, but the most common sizes are 130mm for road and 135mm for MTB. There are two main hub types, front and rear.

How is rear dropout spacing measured?

Up to previous page. Frame spacing is the inside distance between the two fork ends (drop outs), where the wheel fits in. This can easily be measured just by removing the wheel and holding a ruler up to the space where the wheel came out.

How do I know my freehub size?

Measure along the top of the spline, not in the valley between the splines. these measurements are from the portion of the splines that are machined to a larger diameter, Not from the inner flange area of the freehub.

How does a bicycle rear hub work?

A freewheel (or freehub depending) is a ratchet and pawl system. Halfway through, the direction reverses and the ratchet turns clockwise, engaging the pawl which drives the axle and the bike forward. That's pedaling backward (coasting works the same) and forward on a freewheel bike. Part names.

Are Joytech hubs any good?

Novatec hubs feature on a heck of a lot of new bikes, you just don't know about it. They are one of the biggest hub manufacturers in the world. Bottom line is they are what you'd expect, not the best hubs in the world but not junk either. You can find parts but from odd sources like eBay and direct from China.

Do bike hubs make a difference?

Hubs that are "louder" usually have more engagement points. This means your drivetrain picks up faster, so less energy is lost. Hubs that have sealed cartridge bearings or needle bearings usually never need to be replaced, they're far stronger and stay cleaner.

Is 15mm thru axle better than QR?

You decide. 15mm QR is much easier to change wheel than Qr and that is the biggest advantage. In 120 mm fork It makes no difference that I can tell on the trails I ride. I can tell the difference, as I have both but you soon adapt to the QR feel.

What is 12mm thru axle?

The frame shown below is a road disc model that uses a 142x12mm hub specification. From this specification we know 142mm is the hub width (or frame spacing) and 12mm is the diameter of the axle. Total Thru Axle length from the seat to the end of the threads.

Can you convert QR to thru axle?

You can convert to thru-axle hubs to QR (and vica versa) BUT ONLY if the hubs are convertible to start with - hubs such as Hope evo/pro hubs for example.

Should you grease through an axle?

Dont grease your thru axle. You want the wheel spinning on the bearings, not the bearings spinning on the axle. All the manufactures Ive talked to have said this. Also, the axle is anodized aluminum, you dont need to grease it to protect from corrosion.

Are thru axles better?

With a thicker axle bolted directly onto the bike, strength and stability are greatly improved. The end result is a stiffer front end and the elimination of brake rub. Plus, by adding a camming mechanism (like the QR lever) you can still remove your wheel quickly. Thru axles are safer and improve bike performance.

How does a bike axle work?

The axle provides the method of attachment onto the bike (to the frame for the rear, or fork for the front). Axle designs vary greatly depending on the type of hub, but the most common are either a solid axle set up, where bolts are threaded onto each end of the axle, fixing the wheel into the bike.

Can I convert quick release to thru axle?

Some hubs can convert from quick release skewer to 10mm bolt on through axle. This makes a noticeable improvement in rear wheel stiffness and feel of the traction limits.

How do you measure the size of a nut?

Place the end of a measuring tape on one of the flat sides of the nut's outer perimeter. Stretch the tape measure across the nut's diameter to the flat-side directly across from the one your pulling from. If the nut is metric, count the number of lines on the tape measure to find the measurement.

What size pedal wrench do I need?

Pedal wrench flats are typically 15mm in size. 9/16" (~14.3mm) is somewhat common on older pedals. 17mm and other sizes have been used, but you aren't very likely to encounter them. (A "cone wrench" is thinner and shorter than a pedal wrench, and unable to provide appropriate durability or leverage for use on pedals.

What is nominal thread size?

Threads are designated or named by the external thread major diameter and a pitch measurement. Thread sizes are given in nominal sizes, not in the actual measurement. The exact measurement is slightly below the named or nominal size. For example, a 6mm bolt may measure 5.8mm or 5.9mm, but it is called 6mm bolt.

What size are BMX wheel nuts?

The socket wrench, extension and 17mm socket are something you're going to need in that tool box of yours. Although female axles are becoming more common, the trusty 14mm male axle with the 17mm nuts are still the most common.

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