My old 26 inch MTB had quick release skewers, but my upgraded 29er has thru axles – I was wondering, what’s the difference between a Quick Release and Thru Axle?

Both quick release skewers and thru axles are metal rods that keep bicycle wheels in place. Skewers use a camming mechanism to secure the wheel to u-shaped fork dropouts. Thru axles thread through the wheel hub and circular dropout holes. Thru axles work better to keep wheels attached to the bike.

The end of the quick release skewer era?

In 1927, Italian bike racer Tullio Campagnolo  (Link to Wikipedia) got frustrated when having to remove his wheel during races. Back then, you had to flip your wheel around to change gears since each side had a single sprocket. Unbolting and reinstalling the wheel was a pain.

Tulio eventually came up with the quick release skewer mechanism which makes wheel removal a snap. This device dominated the industry for over 80 years. With the advent of downhill mountain biking, however, the QR skewer revealed a weakness: it could not stand up to punishing downhill courses.

So bike inventors got back to work and invented the thru axle.

Thru axles takes the industry by storm

When downhillers starting popping out wheels and snapping skewers, they knew the QR was a problem. So instead of u-shaped dropouts, they designed dropouts with holes and beefed up the axle. The thru axle threads directly through the fork holes and the wheel hub. This makes it nearly impossible for the wheel to detach.

If you’re shopping for thru axles, I recommend getting a name brand. I struggled with an off brand axle coming loose. DT Swiss sells a rear 142mm by 12mm that has worked great. You can read more reviews and check the price with this AMAZON link – DT Swiss Rear Thru Axle

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. It’s no wonder that the QR skewer is quickly disappearing from competition level MTBs.

What do you mean by “eliminates brake rub”?

When you stand to pedal you often rock your bike side to side. This puts a lot of pressure on the fork and it can flex a bit. This movement can even cause the rim or disc rotor to rub on the brake pads.

You might not think this is a big deal, but pro riders want to eliminate any amount of drag. On long epic rides, you don’t need anything holding you back on that long climb home either.

Are thru axles better than QR skewers?

I used QR skewers for years and never had a problem. Still, I fully understand the thru axle advantage. If I was a downhiller, or big jumper, I’d go with thru axle for sure.

Upper end bikes are pretty much all outfitted with thru axle these days, so I guess I’m good with it. Safer is always good. I do notice the stiffer front end improves handling as well.

How do QR skewers work?

The QR skewer works by using a camming mechanism to clamp the wheel down. This basically compresses the fork enough to hold the wheel in place. For most normal trail riding, the QR works just fine.

If you’ve bent your QR axle, you should seriously consider replacing it. Wheel bearings can wear-out prematurely which will ruin the wheel hubs. Also your axle holds the wheel in place, just be safe and replace. Amazon sells QR axles, I found some that are highly rated and priced great. Here’s a link – DEERU MTB SKEWER QR AXLES

The QR skewer rod slides through the wheel hub and the mechanism is designed for u-shaped fork dropouts. The skewer has a closing lever on one end and an adjuster nut on the other end. When the wheel is in place, the closing the lever generates enough compression to keep the wheel locked in place.

When you close the lever, you should have to apply enough force that it leaves an impression on the skin of your palm. Tension is changed by adjusting the cap on the end opposite from the lever.

How do thru axles work?

Thru axles also insert through the hub, but instead of u-shaped dropouts the fork has holes. On one side, the fork hole has an integrated nut. When you insert the thru axle, you have to screw it into the integrated nut. This means the axle is “bolted” directly to the frame.

Thru axles can also close with a lever, and the same rule applies: close with enough force to leave an impression in the palm. You can also rotate the integrated nut to adjust tightness. By pushing on the axle, you can move the nut out to a position that allows for hand adjustment.

If I have QR skewer wheels, can I upgrade to thru axles?

For wheels that come with skewers, swapping out for thru axles is possible – sort of. Traditional u-shaped forks do not have an integrated nut. There are some retrofit kits out there, but I’m not sure it’s worth it.

One attractive option is a thru bolt axle. This is kind of a hybrid between skewer and thru axle. The thru bolt is beefier, but it still has an adjustment bolt cap like the traditional skewer.

Still, it can be challenging to find the right fit. You have to consider fork spacing and axle diameter. Getting these both of these spot on isn’t easy. But before you get rid of the skewer equipped wheels, see if your local shop can help you out.

Thru axles and thru bolts eliminate slippage

In some cases, wheels can slip out of the dropouts. With thru axles this problem is solved since the axle essentially gets screwed into the frame. Plus, there’s no possible way for vertical movement of the hub when using thru axles.

A subject that is HIGHLY connected – yes literally connected to axles is the wheel hubs. My article on How to Adapt an Old Wheel Hub to Newer Boost Hubs explains even more about mountain bike wheels, axles and hubs.

If you retrofit a traditional wheel retention system with a thru bolt, most say that wheel slippage is eliminated. If I had a bike I loved, I would try the thru bolt fix before going out and buying a new frame.

Bike Rack Issues – How do you Transport your Bike?

One major issue with thru axles is car bike racks. If you have a rack that clamps onto u-shaped dropouts, you’re going to have problems with the closed circular thru axle dropouts. If there’s one thing I love about the bike industry it’s the innovation. And sure enough, thru axle adaptors have been developed for your rack.

Thru axle diameter difference for front and rear

When you go to buy thru axle equipped wheels, you might encounter a few options about axle diameter. It looks like the standard has become 15mm for front wheels and 12mm for the rear. The larger front axle diameter illustrates the stress placed there due to steering which increases torsion forces.

For comparison sake, QR skewers are usually 5mm in diameter. Also, first generation thru axles measured 10mm.

Safety factor looms even larger

It’s logical to assume that a u-shaped dropout is more dangerous than completely encircling the axle. There’s more to the story though. I came across this road bike article, that explains that with disc brakes, the rotational forces on the hub are amplified.

This means that wheels can literally rotate out of open mouthed dropouts. So even if you check your skewers before rides, a long ride with heavy breaking might end up with a wheel ejection. Thankfully, I’ve never seen this happen, but the reasoning adds weight to the case for using thru axles.

Don’t want to give up your current frame?

Some riders might have an old frame that they absolutely love, but you also want the benefit of thru axles. My advice would be to upgrade your front shock to one that is thru axle compatible. On the rear end you could go with a thru bolt.

Lose the lever

If you want a super sleek look, you can get thru axles without the cam lever. It’s basically a long bolt that can be adjusted with a hex wrench.

Some say this can even reduce wheel theft since you can’t just pop the lever to remove the wheel. I say, lock the frame and the wheel together if you don’t want them to get stolen.

If you ride in tight, rock infested, damp areas then the leverless thru axle is ideal. This minimizes your chances of having the release lever getting knocked around which could loosen the axle. Like I said, it’s sleek.

Final thoughts on QR skewers vs. thru axles

Does the average trail rider need thru axles? Some say it’s just the industry trying to sell more. For the downhill crowd, the component was born out of necessity.

Still, I remember the initial resistance to disc brakes. Now, everybody swears by them. I think thru axles are worth it and make sense for every rider. I like safer bikes!