I have been trying to find a bike shop or anywhere that still sells M9 nut which holds on the wheel hub next to the back wheel cassette for the cassette on my back wheel. I have a Vintage Sears Free Spirit Danish bike which has the old 3/8th" or 9mm size.

So far, all the bike shops just say they can not help but no additional help at all despite me asking. I hope someone can help on here please.

Stock photo of bike
enter image description here

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    Hi Sandy, could you perhaps add a photo of the casette or if possible the part you're looking for (even better)? Could you describe the function of said part? This might make it easier to answer your question. Thank you Feb 22, 2020 at 10:36
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    Go to a hardware store and purchase a 3/8" nut. (Be sure to get the right thread, of course.) Any decent hardware store (in the US) should have this in stock. Feb 23, 2020 at 19:29
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    As @DanielRHicks said, you can buy the nut you need at a hardware store. Just 1 thing to note: look at the nut on the other side of your wheel. One side of the nut may have a rough/serrated face. This would be to prevent the nut from loosening over time. If this is the case, I would suggest also purchasing a tooth lock washer at the hardware store. (Look up some pictures on Google.) The tooth lock washer will help prevent the nut from loosening.
    – sam
    Feb 23, 2020 at 21:16
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    Note that 9mm is not the same as 3/8 inch. They are close, but the thread is different. If you are buying both the bolt and the nut to go through a hole they may be interchangeable. If you are buying a nut to go on an existing thread they are probably not. The standard pitch for 3/8 is 16 threads per inch, which is 1.5875 mm, much coarser than standard M9. The fine pitch is 24 threads per inch, close to but coarser than 1.0mm pitch. Feb 24, 2020 at 14:47
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    Thank you for all the help. I have rung and messaged so many places and the actual shops say we do not stock but if you come in we will see if we have anything in our bits box . So will be visiting as many as I can before I am lucky . If not I suppose a whole new wheel for £30 just because of a nut and the bike is only maybe worth £50 at the moment . Fingers crossed . Mar 4, 2020 at 9:04

2 Answers 2


It's not M9. M9 is never used on rears. When 3/8" axle hardware sizes are expressed in metric, they're called 9.5mm.

What you have is almost certainly 3/8"x26tpi. If you don't have a caliper and thread pitch gauge, carefully taking the measurements from the axle with a ruler works too. There is some nonzero chance it's M10x1, but not likely.

A single 3/8"x26tpi locknut is something probably easiest attained by pulling off a dead wheel or hub. It's one of and maybe the most common sizes in the world. If you're squirreling through random axle hardware, distinguishing between 3/8x24 if all you're measuring is the nut with a thread pitch gauge is impractical, so again, measure the axle.


From your photo, I'm guessing its a locknut, and you have a photo of the one from the other side.

The "come dig in our parts-bin" suggestion is great - any shop that helps you like this is worthy of your business. Take the whole wheel with you for testing.

Second option is to purchase a complete replacement rear axle. Admittedly its a lot more than you need or want, but spares are good. A whole axle set will likely look like this. Locknuts are labelled below.

enter image description here

ASIDE Given your bike is now down two locknuts, the wheel bearings will likely be quite loose. To set the bearing preload (tightness) correctly can be fiddly but is completely achievable. The only special tool needed is a cone spanner to fit your cones. If you have problems with this check back with a fresh question. (I can't find a pre-existing question on "how to adjust wheel bearings")

As for finding/identifying a good LBS; generally speaking, bike shops fall into one of two categories.

  1. Those that feel sparse or "empty" , tend to have lots of clothing, and very few bikes. These seem to focus on only selling the latest-and-greatest and won't be able to help you with a vintage bike. And they're expensive.

  2. The LBS, or Local Bike Shop. May be hard to find because they're not necessarily high-street stores. Will often feel as cluttered as Grandad's shed. Also often have a whiff of oil and rubber, and will have a LOT of bikes on display... often so many that they flow outside. This is the kind of store you want.

How to find a LBS? Ask around - anyone who's a committed cyclist in your area will likely have some advise. Neighbours and coworkers are good examples.

  • Thank you so much for all your help. So a new axle with the more available sizes if any replacements are needed in the future would be okay using same wheel ? Thank you. Mar 6, 2020 at 10:13
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    The axle in your image is apparently a quick-release hollow axle. The bike in OP's image almost certainly uses regular nutted axles. Aug 2, 2020 at 15:21
  • @DanielRHicks fair point - it was intended to show the purpose of the locknut.
    – Criggie
    Aug 2, 2020 at 22:27

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