I need a BMXpert

[RatRodDad]

I found a BMX bike the other day that the owner was throwing away (see picture below).

I began pulling parts off of it today and I have a couple of questions that hopefully someone who knows about BMX bikes can answer for me.

First, the Mongoose had a nice aluminum neck on it that I may try to use on my RRBBO cruiser. My question there is do cruisers and BMX bikes have the same diameter neck tubes?

The tube on my front forks for my RRBBO bike is rusty inside since it sat outside with no neck in it, so at first pass the neck from the BMX bike wouldn't slip down in the tube. It may just be the rust keeping it from going into the neck, or the two bikes may use different size fork tubes, so hopefully someone will know for sure if it should work or not.

The other question I had is on front sprockets. In looking at ones on Ebay it looks like a BMX bike uses a 3/32" chain like a road bike or multispeed bike, versus my cruiser using a 1/8" chain. So I'm wondering if I will run into problems using a 3/32" tooth sprocket with an 1/8" chain. Will it wear funny, slip, mess up the 1/8" chain, etc.

So if anyone knows the answers please let me know. And thanks for the help.

 

[socal_jack]

Not really a bmx expert but have used a bunch of the bmx stuff on cruisers to learn some stuff. The newer BMX stuff has for the most part gone to 1 1/8" steerer tube diameter. The old-mid school 1"steerer can be either 22.2 or 21.1mm inside diameter like alot of the old cruisers. So it could be the rust or the RBBO bike has the 21.1 and the bmx has 22,2.
The same goes for the headsets, the top nut can have either diameter. Sometime you'll find a headset top nut 21.1 but the inside of the fork is acutally 22.2.

As far as the front chainring, some of the bmx equipment will work with either chain size, no way to tell ahead of time unless the seller knows, usually it will state that on ebay if the seller knows.

 

[RatRodDad]

Thanks, SJ.

I guess I just need to clean up the rust on my cruise fork and see if it fits. I will need to do that sooner or later anyway so I might as well get busy and get it done.

And since I have the BMX sprocket I guess I can try it on one of my cruisers. I just didn't want to trash the chain by doing that.

Or my other option is to find a cheap 1/8" sprocket on Ebay - which is probably the safest bet.

Thanks again for the input.

 

[Markm]

that sprocket should work...just pull it out and roll it across the chain while its still on the other bike to check. also, try your buildoff bikes stem in the mongoose and see how it fits......

 

[RatRodDad]

Thanks, Markm. I think I have an extra 1/8" chain around here somewhere, so I can lay that around the sprocket and see how it fits.

Unfortunately my RRBBO bike didn't have a neck or handlebars with it - which is why the inside of the fork tube is so rusty.

Since you mentioned it, though, I can always try the BMX neck on my Caloi cruiser since I think it has a standard cruiser type fork on it. That will let me know if it should fit the Huffy fork.

 

[Markm]

sometimes its real close...

 

[RatRodDad]

Okay, this was strange. I remembered that Steve gave me a Huffy fork a while back so I found that and tried the BMX neck on it. It wouldn't fit that fork either.

Then I noticed while I was holding the neck that the bottom piece - the piece that tightens up inside the fork tube, felt a little larger than the neck tube. So I unscrewed that piece and took it off and wa la, the neck tube itself fit in the fork tube with no problem.

So the neck tube will fit inside the fork tube as long as I either find a smaller diameter bottom piece - or maybe even grind that one down a little where it will fit.

So it looks like I will be able to use that neck afterall.

I also took the extra cruiser chain I had and tried laying it over the BMX sprocket. It would probably work okay, but it does have a little side to side play since the links are a little wider than the teeth on the sprocket. So I will have to decide whether to use it or to find a 1/8" sprocket.

 

[Markm]

cool

 

[socal_jack]

Yep, like I was saying I've seen mixed pieces on the older stuff, definitely need to experiment and not let anything hang you up like that expander piece. Mever saw the combo you had but doesn't surprise me.

 

[RatRodDad]

The stem is basically a polished square aluminum block with the bolts on the front so the handlebars sit out front.

I just liked the clean look of it - plus it didn't stick forward very much.

So it will probably go on my RRBBO cruiser - assuming I can find some BMX type handlebars that I like to go with it.

Here's a couple of shots of it.