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quote:
What's the difference between motocross rims and road bike rims? Are flanged much better than non-flanged? I saw this ad on Craigslist and was wondering if they're worth looking in to.

http://losangeles.craigslist.org/mcy/138681280.html

Thanks,

Tom W.
'70 CL350

Edited by - Tom W. on Mar 03 2006 4:56:22 PM
MX rims are usually hella skinny and huge to boot. on an MX bike a 21" diameter rim is not uncommon at all. Also the trar tire on a dirt bike is usually as skinny if not skinnier than the front tire of a road bike. Finally, MX rims take different spokes, thinner and some a lot less than a road tire would. IF you are considering these rims I would suggest you match them up to your current ones as best you could.

In my opinion flanged is better because the tire stays on the rim when you have a flat. Most modern street spoked rims are flanged.
 

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i think other than sizes, they are the same. i know a bunch of people who have various dirtbike rims laced to street racebikes. now there could be pitch issues and stuff like that but i dont know. as far as what they are, they are the same.

my guess would be if you can find a wm2 18", its be the same as a street bike, but possible with a different drilling depending on hub size.

jc
 

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Tom,
I run dirt bike rims on all my road race bikes. They are fine if you choose the right size. Most dirt bike rims use 36 or 40 holes just like street rims. Dirt rims do come in a lot of 19 and 21" sizes which you wouldn't use on a street bike but their 18" rims are usually available up to WM3 in width...enough for most 500cc and below street bikes.
I run Excel 18" 36 hole WM2 rims on my race bikes....unflanged...the flange they speak of is on the inside (spoke) side of the rim...like original Akront's, British rims etc. Has nothing really to do with how the tire is mounted or retained...the flange is no where close to the bead of the tire. Flanges were a design aspect of alloy wheels back when materials and design made them necessary for strength....the design has carried over mostly out of momentum and the fact that there are still some cheapo spanish and chinese companies turning out crap rims that need the flanges for strength.

One thing about flanges to remember...they are a tad heavier and fill up nicely with garbage. Big hp 350-500cc bikes...I'd still use them. 350cc and below...no need. A good Excel unflanged dirt bike rim will work great.
JohnnyB
 

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quote:
Tom,
I run dirt bike rims on all my road race bikes. They are fine if you choose the right size. Most dirt bike rims use 36 or 40 holes just like street rims. Dirt rims do come in a lot of 19 and 21" sizes which you wouldn't use on a street bike but their 18" rims are usually available up to WM3 in width...enough for most 500cc and below street bikes.
I run Excel 18" 36 hole WM2 rims on my race bikes....unflanged...the flange they speak of is on the inside (spoke) side of the rim...like original Akront's, British rims etc. Has nothing really to do with how the tire is mounted or retained...the flange is no where close to the bead of the tire. Flanges were a design aspect of alloy wheels back when materials and design made them necessary for strength....the design has carried over mostly out of momentum and the fact that there are still some cheapo spanish and chinese companies turning out crap rims that need the flanges for strength.

One thing about flanges to remember...they are a tad heavier and fill up nicely with garbage. Big hp 350-500cc bikes...I'd still use them. 350cc and below...no need. A good Excel unflanged dirt bike rim will work great.
JohnnyB
I stand corrected on all points. Tell me something branson, what is it called when the rim has a (for lack of a better term) flange that keeps the tire on the rim in case of a flat? I'm not talking the internal bead lock blocks but something in the rim itself.

I used to spend lotsa time in the cycle salvage yard in louisiana trying to get mx swingarms to fit older 70's street bikes. Some of those 80's mx'ers have weird spoke configurations. I saw one once that had something like 20 spokes in it, but I think it was an older trials bike.
 

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Geets,
To be honest I've never seen such a flange. I've seen some dirt bike rims with a bead area designed in such a way that you can run screws through it into the tire bead, I've seen the internal bead locks. I'd guess than any flange that extends outward around the bead would make mounting the tire next to impossible. I've heard of what you are talking about but never seen one.

About the fewest spokes I've ever seen on a wheel is 32, seems like there have been a few odd purpose wheels with 28. What can be misleading just looking at various spoke wheels is the different spoking patterns used. Typical of most Japanese bikes is the "cross 2" pattern, some Euro dirt bikes and Brit street bikes used "cross 4" pattern, and I'm sure there are others I haven't seen.

You know...now that I think about it...seems like I remember when bikes makers started touting "safety rims". Look at a mid 60's steel Honda rim...often very little height on the bead flange. I think in the later 60's or early 70's they started making rims with a taller bead flange, and they called these "safety rims" because the tire was less likely to come off the rim in a flat. I bet that's what you thinking of. To anyone under 50 years old the "safety" rims would probably be all they have ever seen.
JohnnyB
 

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Discussion Starter #7
Thanks for the info.

I've got a question about rear wheel spacing. Is the rear rim always centered on the hub? I use to work in a bicycle shop and laced a couple of wheels. On bicycle rear wheels the spokes were different lengths to offset for the cluster (gears).

I guess another way to ask this question, are rear wheel spokes the same length on both sides?

Thanks,
Tom

Tom W.
'70 CL350
 

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Tom...they are on most Japanese bikes. Some Brit, Euro and US bikes used different lengths...mostly bikes with conical rear hubs. The rims weren't really ofset from the hub...but the spokes were a different length because the spoke flanges on the hub were a different OD on left and right.
JohnnyB
 

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