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#224905 - 11/23/08 9:11 am Help with Rim Sizes  
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Hector Catre Offline
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Hi All,

I'm looking to rebuild my wheels and need some help with Rim sizes and appropriate tire sizes.

I'm rebuilding a pair of 60's atlas wheels.

From reading through previous thread, I see that the front and rear should both be 40 spoke 19" WM2 rims.

Now in doing some research, I found the following:
WM1 = 1.60
WM2 = 1.85
WM3 = 2.15
WM4 = 2.5
WM4.5 = 2.75
WM5 = 3.00
WM6 = 3.50
WM9 = 4.25

I measured the outer diameter of my rusted out rear rim and it looks like it's 3". The outer diameter of my rusted out front rim is 2.5"

Is the WM rating the inner mount measurement or the outer rim measurement?

Thanks
H



Last edited by Hector Catre; 11/23/08 9:12 am.

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#224906 - 11/23/08 9:26 am Re: Help with Rim Sizes [Re: Hector Catre]  
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L.A.B. Online content
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Originally Posted By: Hector Catre
Is the WM rating the inner mount measurement or the outer rim measurement?



It's the inner measurement: http://www.central-wheel.co.uk/cwc/english_chrome_rim/english_chrome_rim.html

#224909 - 11/23/08 9:51 am Re: Help with Rim Sizes [Re: L.A.B.]  
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Hector Catre Offline
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so if that's the case should I get a WM3 rim for my atlas rear wheel?


- Triton Project
-- '63 Norton Atlas
-- '56 Triumph Thunderbird 650
- '72 BMW R75/5 Cafe Racer
- '73 Yamaha XS650
- '75 Yamaha XS650
#224912 - 11/23/08 11:03 am Re: Help with Rim Sizes [Re: Hector Catre]  
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Originally Posted By: Hector Catre
Hi All,

I'm looking to rebuild my wheels and need some help with Rim sizes and appropriate tire sizes.

I'm rebuilding a pair of 60's atlas wheels.

From reading through previous thread, I see that the front and rear should both be 40 spoke 19" WM2 rims.



Hello, Hector.
The "wm"-family of rims have some limitations. WM2s are 19" (dia). WM3s and beyond are 18" and below. The "WM" can be said "wide measure"...

As for the rubber: We often get (18") WM3-rims to get a better choice of rubber(the 19" rims give a limited variation). That also effects prices (if its of any concern).

The classic measures for a wm2 tyre is typical Dunlop K81 3.25" (the first '67 Norton Commando's front wheel - 3.50/60 rear), 3.50,3.60,3.70,4.00,4.10. The latter was Norton Commando post '70 models. Simply economic matters (same dim front and rear gave twice as much tyres pr bike hence lower prices).

I have chosen a 19" (WM2) front with a 3.60 Dunlop K81. Rear an 18" (WM3) 4.25 (according to the above mentioned, it is no such 4.25 dim in the "WM2"-family. 4.10 is max).

Hope this is of help.

Good Luck!

regards
jangg


'73 Commando Basket - new aluminium cyl
'93 Ducati 900 SS

"Better lit a light than cursing the darkness"
(Confucius)
#224917 - 11/23/08 12:08 pm Re: Help with Rim Sizes [Re: jangg]  
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Originally Posted By: jangg
The "wm"-family of rims have some limitations. WM2s are 19" (dia). WM3s and beyond are 18" and below.



WM3 rims are still available in 19" diameter (see CWC link above = 19 x 2.15) as far as I know?

#225389 - 11/26/08 4:26 am Re: Help with Rim Sizes [Re: jangg]  
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Stuart Online content
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Hi,

Originally Posted By: jangg
The "wm"-family of rims have some limitations. WM2s are 19" (dia). WM3s and beyond are 18" and below. The "WM" can be said "wide measure"...

As for the rubber: We often get (18") WM3-rims to get a better choice of rubber(the 19" rims give a limited variation). That also effects prices (if its of any concern).

The classic measures for a wm2 tyre is typical Dunlop K81 3.25" (the first '67 Norton Commando's front wheel - 3.50/60 rear), 3.50,3.60,3.70,4.00,4.10. The latter was Norton Commando post '70 models. Simply economic matters (same dim front and rear gave twice as much tyres pr bike hence lower prices).

I have chosen a 19" (WM2) front with a 3.60 Dunlop K81. Rear an 18" (WM3) 4.25 (according to the above mentioned, it is no such 4.25 dim in the "WM2"-family. 4.10 is max).

'Fraid this is confusing to the point of nearly being completely wrong. frown

1. 'WM' one of a number of wheel rim cross-sectional profiles; afaik, it's obsolete and you don't get new rims in that profile today. Otoh, the 'decimal' numbers are to a slightly different cross-sectional profile known as 'MT' and, for our purposes, they can replace an old WM-profile rim.

2. There is no correlation between rim widths and rim diameters; availability of rim width/diameter combinations is simply determined by the market - e.g. while you can get 19" rims in both 1.85 (WM2) and 2.15 (WM3), because lots of Brit. bikes used 19" WM2 on the front and Tridents and Commandos used WM3 on the rear, but you can also get 17" rims in 1.85, 'cos certainly early Triumph unit 350's and 500's used 17" WM2.

3. While this strays off the original question, there never was any such tyre as a "Dunlop K81 3.25" - all I can think 'jangg' meant is the original 4.10x19 K81 is a similar overall diameter to the commonly-specified 3.25x19 front; however, that K81 is appreciably wider overall, which can make installation between forks designed for the 3.25 difficult or impossible.

4. What is a '3.50/60 rear'? confused

Hth.

Regards,

#225395 - 11/26/08 7:02 am Re: Help with Rim Sizes [Re: Stuart]  
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Originally Posted By: Stuart
Tridents and Commandos used WM3 on the rear,



No standard Commando model had a WM3 rear rim, as far as I'm aware, - even up to the last 850 MkIII model.

#225406 - 11/26/08 10:55 am Re: Help with Rim Sizes [Re: L.A.B.]  
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I bought a pair of Commando hubs and my new wheels are ready to go. I just have to pick them up. I've gone to 2.5 inch wide 19 inch diameter alloy rims with stainless spokes, not to fit wider tyres, which I don't think are available anyway in 19 inch, but to spread the profile and give me a better contact patch at all lean angles. If you look at a 100/90 Avon Roadrider, or any other tyre I can think of, on a standard 2.15 inch rim, the tread sits at such an angle that you'd be grinding the crankcases by the time you used all of the tread. I should have them this weekend so I'll give you a report after I've put a few miles on them.

#225407 - 11/26/08 10:56 am Re: Help with Rim Sizes [Re: Fullauto]  
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Oh, yes, the Commandos did indeed use WM3 rims front and rear. 2.15 inch.

#225457 - 11/26/08 6:39 pm Re: Help with Rim Sizes [Re: Fullauto]  
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Originally Posted By: Fullauto
Oh, yes, the Commandos did indeed use WM3 rims front and rear. 2.15 inch.



Sorry, but I disagree, - check any Commando parts book or manual, = WM2 only.

1968-'69-'70 parts book: = rim: part (NM) 18350 (front & rear) "WM2-19".

1971 book: NM18350 (front & rear) "WM2-19"

1972 book: 061951 "WM2-19" front disc wheel , NM 18350 "WM2-19" (front drum and rear)

1973 book: same as 1972. "WM2-19"

1974 book: 061951 "WM2-19" front, 065730 rear "WM2-19"

1975 book: 061951 front "WM2-19. The rear 066119 only says "Rim" however the workshop manual is more specific "WM2-19" front & rear.

And my own 1975 850 MkIII Commando still has the correct Dunlop MC288 and Dunlop MC289 WM2-19 rims on it.









Last edited by L.A.B.; 11/26/08 7:16 pm.
#225463 - 11/26/08 7:00 pm Re: Help with Rim Sizes [Re: Stuart]  
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Originally Posted By: Stuart
Hi,

3. While this strays off the original question, there never was any such tyre as a "Dunlop K81 3.25" - all I can think 'jangg' meant is the original 4.10x19 K81 is a similar overall diameter to the commonly-specified 3.25x19 front; however, that K81 is appreciably wider overall, which can make installation between forks designed for the 3.25 difficult or impossible.

4. What is a '3.50/60 rear'? confused

Hth.

Regards,


Sorry - regarding "3". - Not 3.25" - from 3.60" (see "K81" below -
the narrow models are the "K70" product line):
555-300X18/K70 3.00x18 Dunlop K70 tyre
555-325X18/K70 3.25x18 Dunlop K70 tyre
555-325X19/K70 3.25x19 Dunlop K70 tyre
555-350X18/K70 3.50x18 Dunlop K70 tyre
555-350X19/K70 3.50x19 Dunlop K70 tyre
555-400X18/K70 4.00x18 Dunlop K70 tyre
555-360X18/K81 3.60x18 Dunlop K81/TT100
555-360X19/K81 3.60x19 Dunlop K81/TT100
555-410X18/K81 4.10x18 Dunlop K81/TT100
555-410X19/K81 4.10x19 Dunlop K81/TT100
555-425X18/K81 4.25x18 Dunlop K81/TT100

Regarding "4".
I meant 3.50" (or 3.60" was mounted stock - one of these dimensions). And you're right: It's out of scope.

Then L.A.B. is right - whatsoever (and I'm sorry getting off track with Commando-talk).

Sorry
jangg


'73 Commando Basket - new aluminium cyl
'93 Ducati 900 SS

"Better lit a light than cursing the darkness"
(Confucius)
#225470 - 11/26/08 7:40 pm Re: Help with Rim Sizes [Re: L.A.B.]  
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Once more a bit "quick-and-easy".

Corrections. According to Roy Bacon's "Norton Twin Restoration": 1968-71 Commando had 3.00"x19, 3.50"x19, front and rear respectively. As for rims Bacon says - "WM2 in all cases except:
Some early model 7s with 21 in. front wheel had WM1 rim: US variants. Atlas and hybrids for scrambles or off-road had WM3 rim".
He also says a couple of words regarding offsets: "Atlas with WM2 rims: front, offset from face of bearing boss on brake side ro rim edge is 0.276 in., rear is 1.253 in. - Note that if different rim is fitted it alters the dimension by half the change in rim width.

(beware of offsets, since braking hard in 50-60mph can be an issue)..

Many tyre marks were used - Dunlop amongst others was of course a popular one.

Well again - sorry ..

regards
jangg


'73 Commando Basket - new aluminium cyl
'93 Ducati 900 SS

"Better lit a light than cursing the darkness"
(Confucius)
#225552 - 11/27/08 5:18 am Re: Help with Rim Sizes [Re: L.A.B.]  
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Oops. My mistake. You are absolutely correct L.A.B. I don't know what I was thinking.

Last edited by Fullauto; 11/27/08 5:20 am.
#225558 - 11/27/08 6:33 am Re: Help with Rim Sizes [Re: Fullauto]  
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When you are trying to decide which rim diameter and width to go with when buying new rims, a look at current tire manufactures recommendations can be very helpful. The stock WM-2x19 rims, front and rear, is a poor choice when it comes to selecting new tires. If you are building for show rather than go, I suppose WM-2x19, front and rear, is a must. As for a "rider", WM-3x19 or WM-3x18 up front with a WM-4x18 rear is a good setup, IMO.


Last edited by Jim Clausen; 11/27/08 6:36 am.
#225574 - 11/27/08 12:36 pm Re: Help with Rim Sizes [Re: Jim Clausen]  
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There is indeed a wider choice of rubber in 18" sizes.However, 19s with Avon 100/90 Roadriders are a great choice for all round riding. Sticky with good feel. I certainly wouldn't change for the sake of choice.

#226194 - 12/01/08 7:36 am Re: Help with Rim Sizes [Re: Jim Clausen]  
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Hi Jim,

Originally Posted By: Jim Clausen
a look at current tire manufactures recommendations can be very helpful. The stock WM-2x19 rims, front and rear, is a poor choice when it comes to selecting new tires.

Yes and no.

Firstly, you've forgotten that fitting the same-width tyre to a wider rim will give you a physically-wider finished wheel.

For instance, last wheel I had built was a rear one for my '69 Triumph T100. As standard, this bike runs a 4.00x18 tyre and I wanted to go from the standard WM3 (2.15) rim to a WM4 (2.50) rim. Luckily, I took the original wheel to an long-time Triumph dealer who happens to build wheels but doesn't charge a premium. He advised that a 4.00x18 tyre on a WM4 rim would foul the chainguard and possibly the chain. I went with a new WM3 rim and he's right - there isn't much clearance even with the correct rim and tyre.

Secondly, certainly for Avons, there's always been both a 'Recommended Rim' and an 'Alternate Rim' - for, say, a 100/90 tyre, while the 'Recommended Rim' is 2.50 (WM4), the 'Alternate Rim' ranges from 2.15 (WM3) to 2.75 (WM5?)

Hth.

Regards,

#226222 - 12/01/08 2:00 pm Re: Help with Rim Sizes [Re: Stuart]  
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Jim Clausen Offline
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Don't know about Triumphs. I have a 72 Commando with a 120/90-18 rear mounted on a WM4. Clearance is probably somewhat less than 1/4" on both sides. When you go to wider tires rim offset becomes very critical.

The first few years I had this bike I had WM2x19 rims at both ends. Run Avon Super Venom, front and rear. Changing to the WM4x18 rear with Dunlop GT 501s transformed my bike into a pretty fair handler. Not to mention about a 2 times great tire life factor.

I think if you are in need of new rims anyway, there are better choices than the stock WM2X19, IMO.

#226487 - 12/03/08 1:29 pm Re: Help with Rim Sizes [Re: Jim Clausen]  
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It's interesting that Avon's own website states that the Avon AM26 Roadrider is recommended for a 2.5 inch rim (19 inch) while stating that a 2.15 rim is the narrowest recommended rim size for this tyre. Then, if you run Norton Commando into the tyre guide section, it then recommends the same rubber for the standard 1.85 inch rim ???!!!??
I've been through quite a few Roadriders on standard rims and think they are wonderful. My new 2.5 inch x 19 wheels look gorgeous. I'll post photos next week.

#374003 - 05/18/11 6:11 am Re: Help with Rim Sizes [Re: Hector Catre]  
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You sure about that?
I'm looking at the spec sheet I downloaded from Avon. 3.25/19 and 90/90/19 both recommend 2.15 (1.85min, 2.5max.)
You must be looking at the 100/90/19.


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