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Old 08-31-2007, 12:54 PM   #1
M.O.Ther
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Default Tech: Harley 18" and 19" Aluminum Rims

I've always liked the look of 18 and 19 inch rear wheels better than 16s. But there's something different and possibly dangerous about the Harley 18 and 19 inch rims from the '70s that I'm not sure most people are aware of. These rims are CM profile rims.

What does that mean? CM is the engineering term for the size and shape of the rim and bead seat. WM is an earlier designation, and it means more than just a width, (WM3 = 2.15" etc.,) but a specific size and shape. Current rims are MT or TL profile, at least in those sizes. The problem with the CM profile is that it's .075" smaller in diameter than the others at the bead seat.

Here's what Dunlop says about it. "Fitment to Harley-Davidson 18-inch and 19-inch CM contour rims may result in slippage or air loss. Harley-Davidson 18-inch and 19-inch CM contour rims are not compatible with Dunlop tires" Harley's recommendation to owners of bikes with CM contour rims is to replace the rims or wheels when the tires wear out. My boss, a Harley dealer since the late '60s (in a family owned dealership open since '62) tells me I'm not to even sell tires to guys I know have these rims on their bike, even if they want to mount them themselves. Harley Service Bulletin M-731 dated 6/20/78 deals with this issue.

How to identify these rims: This actually applies to steel rims of the same era as well. The Aluminum rims have a square drop center, a 2.50" bead width, and one of the following numbers stamped in them.

Number Material Size Hub/Brake

43005-70 steel 18" steel spool rear drum
43008-70 aluminum 18" steel spool rear drum
43002-70 steel 19" '64-72 style front drum
43010-70 aluminum 19" '64-72 style front drum
42998-74 aluminum 19" aluminum hub front disc
43018-73 steel 19" aluminum hub front disc

I have also heard of some Lester cast wheels being made to the CM rim profile, however Harley cast wheels are not CM rims.

You can also measure. Measure the circumference of a known good rim (say a WM3 x 18) against one of these and there's almost 1/4" difference at ther bead seat. .075(difference in diameter) x pi = .236".

The problem: If you look at the cross section of a tire bead like a foot, normally the whole bottom of the foot and the back of the heel are in contact with the rim. In the case of a normal tire on a CM profile rim, only the toe and the back of the heel are in contact, and the bottom of the heel is about .037 away from the rim. Less contact means more chance for the tire to slip on the rim. Since these are all tube type tires, the tube moves with the tire and the valve stem rips out of the tube, instant flat tire.

The only tires ever made for CM profile rims were Goodyears, marked "for taper bead base only" and are all at least 25-30 years old by now, not to mention impossible to find.

So it's Harley's, Dunlop's, and probably all the other tire manufacturers recommendation that you don't run these rims with normal tires on your scoot. But some people do and will anyway, including me. In part 2, I'll give you some tips in case you want to ignore the experts' recommendations.
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Last edited by M.O.Ther; 09-03-2007 at 08:15 PM. Reason: clarification
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Old 08-31-2007, 12:56 PM   #2
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Default Tech: Harley 18" and 19" Aluminum Rims 2

Part 2
If you’ve decided to knowingly go against the experts’ recommendations, here are a couple tips to keep in mind.
The bike itself: A seriously high torque motor or really good brakes, combined with a tire that gets good traction might be a combination worthy of second thoughts on these rims
Tire selection: All these rims are .250 at the bead seat. Recommended tires for that size run all the way from 3.25 or 90/90 at the narrowest to 130/90 or 140/80. I’d stay away from the extremes of that. The farther away from the ideal, the more “off” the angle of the tire to the bead seat.
Tire mounting: Use a tire mounting lube that will dry up, like a little dish soap in water. Do not use one that will stay slippery for a long time, like WD-40 or a silicone spray. Make sure the valve stem is perpendicular to the rim and check it often, if it starts to tilt, you’ve got a problem. Go toward the high end on the inflation pressure, remember the bead is being held against the rim with 32 psi, or whatever. It’s not the place to run low pressure for a smoother ride. The tire generally will center itself, but check to see that the tire is true after mounting. It’s a little easier in this case to get a fold of tube stuck under the bead. Consider the use of sheet metal screws through the rim and into the tire bead, but not deep enough to damage the bead cord. It’s an old racer’s trick, and could even give your scoot a little bit of a competition look.
These rims are cool looking, plentiful, and sometimes reasonably priced. A lot of guys run them, and have been getting away with it for years. I just think it’s better to make an informed choice.
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Old 08-31-2007, 01:02 PM   #3
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

Thank you for the information...
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Old 08-31-2007, 05:41 PM   #4
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

Your name came to mind as I saw this. Glad you seen it.
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Thank you for the information...
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Old 08-31-2007, 06:02 PM   #5
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

yes thats good info. i have an ironhead with those wheels in the shop now and i remember they were recalled.

being as that is an old rim, and tire fitment, i have always wondered how that applied to modern radial tires. or if that was a bias ply type issue.

got a best guess?
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Old 08-31-2007, 11:30 PM   #6
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

QUICK! Everyone send me your old alloy Sportster rims before you get killed! M.O., does the smaller diameter also apply to the WM-designated rims?
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Old 09-01-2007, 06:21 AM   #7
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

The smaller diameter does not apply to the WM profile rims, just the CM with the above numbers. I think it was an attempt between Goodyear and Harley-Davidson to make that part of the motorcycle tire market exclusive to themselves.
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Old 09-01-2007, 01:26 PM   #8
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

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Originally Posted by M.O.Ther View Post
I think it was an attempt between Goodyear and Harley-Davidson to make that part of the motorcycle tire market exclusive to themselves.
I know Schwinn did this, made the rim so that only their tire would fit it. I don't know if they still do..........OG
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Old 09-01-2007, 03:41 PM   #9
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

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I know Schwinn did this, made the rim so that only their tire would fit it. I don't know if they still do..........OG

they did. Those wheels only take a 1 3/4 tire a 1.75 will not fit...
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Old 09-01-2007, 04:07 PM   #10
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

does this cm rim profile apply to mags from that era as well?
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Old 09-01-2007, 04:15 PM   #11
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

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does this cm rim profile apply to mags from that era as well?
No, just the "laced" wheels.
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Old 09-01-2007, 04:21 PM   #12
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

thanks!
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Old 09-03-2007, 05:39 AM   #13
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

M.O.ther: Your post makes specific reference to "Dunlop" and "normal tires"......are they're any tires that would work?
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Old 09-03-2007, 06:24 AM   #14
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

What about the earlier hd alloys?....example, the mid sixties sportster wheels. I'm guessing the same thing. And is there any way to check lesters from the seventies, without taking the tire off and measuring? I have em on my BMW r/90/6.
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Old 09-03-2007, 08:45 AM   #15
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

The earlier HD alloy wheels, like from the '60's Sportsters without the square dropped center, are WM profile rims, it was the standard of the day. It's only the Harley/Goodyear design from the '70's that's CM profile, all square drop center .250 width, laced (wire spoke) 18" and 19" wheels.
As for the Lesters, the only set I ever heard of with the CM profile was for a Sportster. BMW wheels likely would not be CM's. Look for markings on the rims/spokes of cast wheels. After a certain date, (early '80's I think) the govt. made manufacturers put the sizing on the outside of the wheel somewhere readable. New Harley fronts, for instance, say TL 2.15 x 19, the TL being the rim profile and the 2.15 the rim width. (some people will tell you TL is for tubeless, not so. If the rim is for tubeless, it will say "tubeless.")
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Old 09-03-2007, 10:18 AM   #16
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

This is an interesting tech. I have an aluminum 43010-64 and it's stamped WM3x19". It's obviously different from the square drop center version with the -70 part number but I never knew there was a size difference. Indian did something like this with their '49 and later vertical twins. They made the rims a little oversize so that only their own tires would fit.
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Old 09-03-2007, 02:21 PM   #17
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

i just disassembled a 16" wheel to get to the hub, paid 100bucks for SS spokes in the correct length for the drop down 18" rim, i will use it. fuck all that shit.
since you said you use them anyway, do you happen to know which tires work well with those rims? Modern profile tires, tubeless, preferably, i don't care to much for "old sk00l" looks and square tires. thanks a bunch
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Old 09-03-2007, 08:43 PM   #18
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

Thanks for the interesting info,
I put an Avon Speedmaster 3:50 x19 on my 72 Superglide with a steel 19 inch front rim and could not get the tire to seat concentrically. Kept having to fill it up and release the air and try again. Sometimes one side would seat the I would turn it over to find the line on the tire on the other side did not line up with the rim edge. The bike handles like crap anyway so I doubt i will be rolling the tire off the edges of this one. I looked at the chicken strips the other day and the stringers left behind from the tire manufacuuring process weere still prominent outside the tire crown. It obviously isn't getting leaned over much.
Doug
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Old 09-03-2007, 08:43 PM   #19
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

Quote:
Originally Posted by Black Horse View Post
M.O.ther: Your post makes specific reference to "Dunlop" and "normal tires"......are they're any tires that would work?
Quote:
Originally Posted by sebastian.kaiser View Post
i just disassembled a 16" wheel to get to the hub, paid 100bucks for SS spokes in the correct length for the drop down 18" rim, i will use it. fuck all that shit.
since you said you use them anyway, do you happen to know which tires work well with those rims? Modern profile tires, tubeless, preferably, i don't care to much for "old sk00l" looks and square tires. thanks a bunch
The only tires that work "correctly" with these rims are Goodyear tires marked "for taper bead base rim only" on the sidewall. They're almost impossible to find, and even if you do they're all at least 25 years old. I know where there's one NOS set of tires, but the guy who has them will only sell them to someone who is doing a perfect restoration on a bike that won't get ridden and will sit in a museum. Not to mention selling them for big $.

Almost any other tire in the right size (an 18" or 19" between about 3.50 or 90/90 and 4.50 or 130/90) will mount, roll, and work "incorrectly." That is, they won't have as full of a contact with the rim at the bead seat as the tire engineers intended. This can lead to possible slipping on the rim, like the rim turning when the tire isn't.

I can't recommend any brand or style. In fact to be safe I'd recommend not using these rims. That said, I have a Conti SuperTwin (120/90x18) on a 43005-70 on the back of an evo Sportster, and a pair of RWL Dunlops (120/90x18 F11 and 130/90x18 K181) ready for a pair of 43008-70s for another project. In addition to those, I have 4 or 5 more of the aluminum rims stashed away for future projects. The more I think about it though, the more likely I am to sheet metal screw the tires to the rims.

As for your question about Tubeless, even if you could seal up the spoke holes, I'm not sure there wouldn't be a leakage issue at the bead seat with this mismatched rim/tire combo.
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Last edited by M.O.Ther; 09-03-2007 at 08:45 PM. Reason: spelling
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Old 09-04-2007, 05:07 AM   #20
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Default Re: Tech: Harley 18" and 19" Aluminum Rims

Thanks - - appreciate your time/expertise.
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