rim size advice

Classic Norton Commando Motorcycles.

rim size advice

Postby caspermj » Mon Jun 11, 2007 12:09 pm

Hi gang,

I realise there's been alot of discussion on this but was wondering if there would be any advantage to moving up from the stock WM2/19 to the WM3/19, front and rear while using the 100/90 19 super venom tire? I'm getting the wheels respoked and this is the opportunity to change them. Any adverse effects if there aren't any gains? The bike is a MKIII. Thanks :)
~Roy

'75 MKIII Interstate

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Postby 79x100 » Mon Jun 11, 2007 12:48 pm

It is what Nortons should have done in the first place. You will be staying with the standard tyre sizes but they will sit better on the rim.

I have a copy of an Avon Tyre / Rim fitment chart which lists 2.15" (WM3) as recommended for a 90/90 (3.60) and acceptable for a 100/90 (The OE WM2 is recommended for an 80/90 !)

Recommended rim for the 4.10 or 100/90 is a 2.50"

I have 18" back and front on my Mk111 and am happy with them.

I use a 100/90-18 on a 2.15 on the front and a 110/90-18 on a 2.50 at the rear.
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Postby caspermj » Mon Jun 11, 2007 1:04 pm

Thanks for the quick reply 79x100 :) I guess there would be no interference/fitment problems either. I want to keep the stock size tire front and rear so that's great.
~Roy

'75 MKIII Interstate

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Postby 79x100 » Mon Jun 11, 2007 1:44 pm

Roy,

I can certainly confirm that the rear is not a problem. I have my 19" wheels still and have just measured them. The rim is a 19" 2.15.40 - TR Akront and is fitted with a 100/90V19 AM18 (The one that can go front or back). It measures 102.5 mm wide (or 4.03" if you prefer). This compares with 108mm
suggested by Avon (on a 2.5" rim).

If you're intending to use an AM20 front, they're quite wide for their size (if that makes sense !) Avon give a width of 109mm for the 100/90 fitted to a 2.5 rim (thus 9mm "oversize" ) My 18" 100/90 AM20 on a 2.15 WM3 is 107.5mm accross and comes very close to the mudguard stays (which are non-standard stainless which may not help).

I can imagine that a 19" tyre 107mm wide might be a bit close. I used to have a 90/90-19 on the front but must admit it looked a bit small under that big Mk111 front guard.

The Metzeler ME33 100/90 on a 2.15 on the front of my 750 is only 100mm wide.

What tyres are you running at the moment ? If you have a 100/90 Avon, how much clearance do you have ?

With any luck, there'll be someone else reading this who has the fitment you're thinking of.
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Postby caspermj » Mon Jun 11, 2007 4:55 pm

Haven't got my new tires on yet, but they're the Avon SV 18's that go either front or back. Checked, cracked, worn out flat TT100's on it now :D . No, :wink: I don't drive it that way! I should be fine with the WM3's and AM18's front and rear then. Thanks a bunch for all the measurements. Good to know the differences in sizes vary alot!
~Roy

'75 MKIII Interstate

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Postby Coco » Tue Jun 12, 2007 10:24 am

I went to a WM 3 rim up front with a 100 x 19" tire and an 18" WM 4 rim on the rear with a 120 x 18" tire.

I should have the wheels soon so I'll report back with any fitment issues, but I was told the wider rear should just slide right in with no problems.
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Postby 79x100 » Tue Jun 12, 2007 2:13 pm

Coco, It could be close. What tyres are you intending to use ? As I mentioned above, Avons are wide due to a "tapered" sidewall.

I have a 110/90 18" AM18 on the rear of my Mk111 on a 2.50 and it measures 118mm. It has about 1/8" clearance from the chainguard.

My 750 has a Metzeler ME99 110/90 18" on a similar 2.50 and it is only 108mm at the widest point.

I've been polishing my rims this evening. A quick way to get sore fingers. Mind you, the smell of Solvol autosol, burnished alli and top-fermented ale goes some way to compensate ! :)
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Postby Coco » Tue Jun 12, 2007 2:45 pm

79x100 wrote:Coco, It could be close. What tyres are you intending to use ? As I mentioned above, Avons are wide due to a "tapered" sidewall.

I have a 110/90 18" AM18 on the rear of my Mk111 on a 2.50 and it measures 118mm. It has about 1/8" clearance from the chainguard.

My 750 has a Metzeler ME99 110/90 18" on a similar 2.50 and it is only 108mm at the widest point.

I've been polishing my rims this evening. A quick way to get sore fingers. Mind you, the smell of Solvol autosol, burnished alli and top-fermented ale goes some way to compensate ! :)


I'm using Bridgestone Battlaxe tires. I bought everything from CNW and they assured me it will fit no problem as that is what they use for rim sizes and tires on their rebuilds when using an 18" on the rear. The Bridgestones are narrower than the Avons.
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