Tire Sizing for WM3 18" Rim?

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Tornado

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I have the WM3 18" rear rim from Madass140 on my Commando. Needs a new tire. I've been running the Dunlop K70 (went well as my first tire on the bike, lasting about 7000 miles) and thinking to try the K81. My supplier (Fortnine) shows two sizes for K81, 4.10 and 4.25/85 for 18" wheels. Would either of those work OK on the Commando?
 
I have the WM3 18" rear rim from Madass140 on my Commando. Needs a new tire. I've been running the Dunlop K70 (went well as my first tire on the bike, lasting about 7000 miles) and thinking to try the K81. My supplier (Fortnine) shows two sizes for K81, 4.10 and 4.25/85 for 18" wheels. Would either of those work OK on the Commando?
I run an Avon AM26 4.00 x 18 on a WM3. That tire is 4.6" wide, and I have no issues whatsoever, and would buy again in a hearbeat.

According to the specs, a K81 4.25/85 is 4.37".
 
I went to a Bridgestone Battlax BT-46 Rear Tire 110/90-18, think it comes out to about a 4.25/85-18, i would have ordered a shinko in a 110/90-18 but they were out, and it seemed to me this covid thing was going to make resupply very delayed... so if they have stock, go for it.
 
I posted the chart below in another thread - had put it together to help my selection.
I do know that a max width of 120 is safe - but you'll be running out of swingarm/chain guard clearance going wider
Cheers

Tire Sizing for WM3 18" Rim?
 
BTW - I installed an Avon Roadrider AM26 (mk2) 400/18 and the chart was spot on - max width is 116mm
I have a K81's on front and rear right now, I can hardly wait to burn that rear tire off so I can put Avon Roadrider AM26 or at least the MKII tires on. When that rear is ready to go, the front will get changed too regardless of how much it is worn.
Seems to me that the AM26 or MKII would be a superior tire to the old school K81's.
 
The K81 TT100 is a good tyre, because of their shape the rear squares off in the centre , good for about 2000 miles (depending ;) the front wears square on the side, right side in the UK, I guess left in the US and Europe but mileage much better.
 
Continental Conti Go 4.00x18 on the old chromed Dunlop WM3, not likely to get 7000 miles out of it though.

K81's were never fun riding over rain grooves cut into California highways, so I quit using them, or any tire with a centerline groove in it. May not be an issue anywhere else in the world, but I still wouldn't use them on anything but a show bike.
 
Continental Conti Go 4.00x18 on the old chromed Dunlop WM3, not likely to get 7000 miles out of it though.

K81's were never fun riding over rain grooves cut into California highways, so I quit using them, or any tire with a centerline groove in it. May not be an issue anywhere else in the world, but I still wouldn't use them on anything but a show bike.
Yes I've experienced that on the K70's on short bits of overpasses here in BC. Also ran into it on drive home on the 405 after buying a new Mini Cooper S off a dealer lot in Southern Cali. Felt like a wheel was coming off. Diminished after higher mileage reached and ultimately cured switching to Avons on the Mini. On the Commando, also seemed to go away after fitting new spindle bushes in SA and doing the clamp mod.
 
I posted the chart below in another thread - had put it together to help my selection.
I do know that a max width of 120 is safe - but you'll be running out of swingarm/chain guard clearance going wider
Cheers

View attachment 81361
I had seen this chart but no K81 listed and can't see where a 4.25/85 sits.
 
I have a K81's on front and rear right now, I can hardly wait to burn that rear tire off so I can put Avon Roadrider AM26 or at least the MKII tires on. When that rear is ready to go, the front will get changed too regardless of how much it is worn.
Seems to me that the AM26 or MKII would be a superior tire to the old school K81's.
The MkII is stil AM26 - see photo of my pair below
1628544644990.png
 
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I’ve been looking at Canada’s https://www.fortnine.ca/en/ site.
They might have things shown a little odd there & they may not have all sizes.
But I do note that on Avon’s website they do differentiate between the MKII & AM26.
It will be next year before I have to deal with it, and for my purposes I would try to get what Avon considers as the MKII, sort of their general riding tire vs the race tire.
Tread pattern looks the same to me, perhaps a softer compound on the AM26?

Tire Sizing for WM3 18" Rim?
 
The MK2 is a replacement of the MK1. If you look on Avon’s web site you see the MK1 tyre list is shrinking rapidly, so I assume they’re phasing them out (?).

Don’t fit race tyres unless you’re happy with VERY low mileages !

Lots of good info on the Avon web site if you click on a tyre, then click ‘show available sizes’ they show diameters, rolling radius, widths, recommended rim sizes, tread depths, etc…

 
I’ve been looking at Canada’s https://www.fortnine.ca/en/ site.
They might have things shown a little odd there & they may not have all sizes.
But I do note that on Avon’s website they do differentiate between the MKII & AM26.
It will be next year before I have to deal with it, and for my purposes I would try to get what Avon considers as the MKII, sort of their general riding tire vs the race tire.
Tread pattern looks the same to me, perhaps a softer compound on the AM26?

Tire Sizing for WM3 18" Rim?
Lucky you don't need new Avons this year, as they are backorder all over the country, in our usual sizes. Most dealers don't expect any new shipment before 2022.
What about USA, folks? Any in stock?:rolleyes:
 
Been waiting to hear back from Fortnine on what sizing to order for the WM3. Welp, today's answer is, they do not provide sizing to given wheel rims, just to specific bikes. So I guess I'll just tell them I have '74 Commando 850 with non-original WM3 18" rim ;-)

Looks like I'll just take my best guess and go with the 4.10 tire unless someone has other advice?
 
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