Cotter pin style rear axle bolt - Honda CBR250R Forum : Honda CBR 250 Forums
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post #1 of 5 Old 04-06-2016, 09:52 AM Thread Starter
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Cotter pin style rear axle bolt

Has anyone drilled the axle and put a "cotter pin type" rear axle bolt instead of the stock of one? I would love to know the size and thread pitch of the stock bolt. If you have a link to an online store or link to the bolt needed would be even more awesome.
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post #2 of 5 Old 04-06-2016, 10:05 AM
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Not to sound like an ass. Why? Are you racing ect?

Take care & ride safe.

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post #3 of 5 Old 04-06-2016, 01:10 PM
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This thread doesn't belong in the General Discussion forum, so it was moved to the Parts & Accessories forum.

As for the OP's question, a drilled axle bolt and castle nut, unless it's required for racing*, isn't needed for normal street use as long as the stock nut and bolt are properly tightened (FYI: the torque spec is 65 ft. lbs.).

* in which case you wouldn't use a cotter pin, but rather stainless steel safety wire. A castle nut could be had from a source like Fastenal... then just drill the end of the stock axle bolt in the correct location.

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post #4 of 5 Old 04-06-2016, 02:06 PM
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I've done it to allow for much quicker tire changes for racing. You can use the stock rear castle nut from a Ninja EX250 - same size and thread pitch. I believe its 16MM, 1.25 thread (but do some research before relying on my memory). I drilled the axle bolt after tightening the new castle nut to spec and marking the openings in the castle nut. Now I use a pin instead of having to safety wire it each time I change the tire.

But as with others, I don't recommend this for a street bike - track/race only.

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post #5 of 5 Old 04-19-2019, 06:06 PM
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All depends if you want to take the red pill or the blue pill ... There is a very sound reason to use a castle nut for both street or track. That reason is if you want to swap the axle insert direction to come in from the LHS.

The stock direction of the rear axle is to come in from the RHS with the nut on the LHS (looking from behind, rear to front of bike). BUT that massive muffler is also on the right and in the way, you cannot remove the axle without also removing the muffler. No biggie, but mildy annoying, but why make more work for yourself to change a tyre / rotor / clean brakes, etc.

However there is seemingly a simple fix ... just reverse the direction of the axle to come in from the LHS and have the nut on the RHS you can remove the axle very easily. No fuss and from a wheel turning perspective no difference. So you would think that Honda would have thought of that ... AND THEY DID!

The reason Honda design the axle to come in from the right is that looking from the RHS of the bike when the wheel rotates as the bike moves forward, the wheel rotates clockwise. There is some drag from the wheel via the wheel bearings onto the axle. This causes the axle to push clockwise onto the nut. And clockwise is righty tighty! And guess what ... anti clockwise is ... lefty loosey. So if you swap and install the axle from the LHS you are putting forces onto the axle that are trying to loosen it! And before you think I am making this ******************** up.

Let's look at the two ways most manufacturers try and 'resolve' this 'problem' rather than just relying on torquing to spec / she'll be right / we won't get sued method.

1. Swap the thread direction. As per say the Fast Frank quick change kit that swaps the direction of the axle on my R6, you move to a LH thread. Then lefty is tighty and righty is loosey. This method is quite painful as you need to remember the thread has swapped and that if anyone else works on the bike that they are aware too.
2. The simplez solution use a castle nut and pin. Manufacturers that have their axle going in from the LHS typically do this as per say the Kawasaki Ninja 250r etc.

Now just to be clear if you insert the axle in from the left and torque it correctly on the stock nut it shouldn't be an issue. I have ridden like that for years before the above slowly dawned on me. But if you want piece of mind ... well now you know a solution or two!

Gunna link to another thread on the forum where someone commented when a workshop installed the axle from the LHS.
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