Tires for my 69 Commando

Old Bloke · Mar 25, 2013

Thank you.
That looks more like the tread radius you'd expect from a modern tyre. Becomes clearer when people start talking about fitting the 100/90 on a wider rim like the WM3, then I guess the tread radius would not be pulled around the tyre like on a WM2 perhaps.

swooshdave · Mar 25, 2013

Old Bloke said:
Thank you.
That looks more like the tread radius you'd expect from a modern tyre. Becomes clearer when people start talking about fitting the 100/90 on a wider rim like the WM3, then I guess the tread radius would not be pulled around the tyre like on a WM2 perhaps.

I have the 100/90 on a WM3 and think it's just right.

worntorn · Mar 25, 2013

bluto said:
Avon does not recommend the 100/90 for WM2/1.85" rims....I did not know this and mounted one, it works OK but the profile is definitely too pinched as pictured below. They do sell the AM26 in 3.25 universal and 90/90 front which they say are OK on a WM2

Most interesting and it is clear that I was far too casual in my recommendation. I have worn out a couple of Avon Roadrider 100/90/19 tyres on the rear WM2 of the Vincent without a problem but that does not make it correct.
Was about to fit two new 100/90/19s to replace worn out Super Venoms of the same size on the front and rear wm2s of the Commando, but this gives me pause for thought.
The interesting thing is that the other size marked on the 100/90/19 Avon Roadrider is 4.10/19. 4.10 /19 is the size of the originally equipped tyres on the wm2s of the MK3 Commando, according to my Norton Riders manual.

So why is this original equipped size no longer suitable for WM2s?
It seems strange that Avon would make a tyre in this exact same size and list it as a replacement for " classic"bikes but make it in such a way that it would not fit the original size rims, which most bikes still carry. This does them out of a very large market, especially if all the other wm2 bikes of the day are added to the 50,000? or so Commandos.

According to the chart, the only tyre suitable for the rear of a standard Commando is the 3.25 x 19, which is a pretty wimpy tyre to put on a bike that came new with a 4.10! The load rating on the 3.25 is very light as well.

Glen

Old Bloke · Mar 26, 2013

swooshdave said:
Old Bloke said:

Thank you.
That looks more like the tread radius you'd expect from a modern tyre. Becomes clearer when people start talking about fitting the 100/90 on a wider rim like the WM3, then I guess the tread radius would not be pulled around the tyre like on a WM2 perhaps.

Click to expand...

I have the 100/90 on a WM3 and think it's just right.

That looks right to me as well, certainly more "normal" than the 100/90s fitted on the WM2.

Old Bloke · Mar 26, 2013

Seems to be no definitive answers, as is the case with lots of the Thorny Norton subjects.

For me, I must, for cost reasons stick with the WM2 rims. Thoughts of fitting a WM3 rim myself crushed by reading the other thorny subject of wheel rebuilds, wheel lacing, offsets, bowed spokes etc (have you read these threads, jeez!) Too hard

Maybe should be brave and try Avons 90/90 front and rear as per Avons recommended fitments, or perhaps a 90/100 rear and try the odd pinched profile. Ho Hum.

bluto · Mar 26, 2013

Old Bloke said:
Seems to be no definitive answers, as is the case with lots of the Thorny Norton subjects.

For me, I must, for cost reasons stick with the WM2 rims. Thoughts of fitting a WM3 rim myself crushed by reading the other thorny subject of wheel rebuilds, wheel lacing, offsets, bowed spokes etc (have you read these threads, jeez!) Too hard

Maybe should be brave and try Avons 90/90 front and rear as per Avons recommended fitments, or perhaps a 90/100 rear and try the odd pinched profile. Ho Hum.

The Avon 90/90 is specified as front only and has less tread depth than the rear or universal tires, but may work fine on the rear in practice....I'm wondering if that would be the case for the Dunlop/Harley D401 90/90-19 I have on the front of my bike, since it is spec'd for very heavy Harleys it might work on the rear of a much lighter bike....but I'll probably lace up a WM3 on the back of my Commando eventually, have built a few bicycle wheels successfully and that experience should help. I'm leery of experimenting with non standard tire installations due to the safety issues.

worntorn · Mar 26, 2013

I called the Avon Tech department this am, the suggestion was to put new rims on the bike, they aren't that expensive. Right!
They really have nothing to recommend for our original rear rims, except the old square unSafety Mileage in 3.50 x 19, and Im not going there, nor should anyone else, unless your bike resides in a museum!

I will probably put the 100/90/19s I have here on the WM2 rims and run them, there was no problem doing this on the Vincent wm2 rear.
One other thorny issue is the weight rating. I have an old 100/90/19 Roadrunner here, it is rated at 567 lbs. The new Roadrider in the same size loses sixty pounds of carrying capacity,the rating is only 507.
I figure the bike with tools and all fuel and oil weighs right close to 500 lbs. I weighed myself yesterday with gear on, that was 263. My passenger with gear is about 170( delicate question), two full panniers are around 50 pounds, top box is generally around 40 when full. This adds up to 1,023 pounds fully laden. I am guessing at least 65 % of that weight is on the rear wheel, so none of these tire sizes is up to the job.

So to really be within spec or close to spec when touring with a passenger, a WM4 rear wheel and 120/80/18 or 120/90/18 tire is needed. Fortunately I tend to ride the Commando solo, so this won't be needed for now, but the old Vincent is going to get a WM4 x18 rim and the bigger tire.

Glen

Matchless · Mar 26, 2013

I feel that I should point out that the original tyres your bike was fitted with are still available. That is a 3.00 19" Speedmaster & a 3.50 19" Grand Prix. The front tyre is available direct from Avon but the rears are made in small batches (by Avon) for Vintage Tyres in England. Even some people at Avon didn't know this! I bought a pair for my 650ss a couple of years ago. They are also made in race compound.
Martyn.

worntorn · Mar 26, 2013

My riders manual for the mk 3 Commando lists the Dunlop 4.10 x 19 front and rear as the supplied tyres when new, fitted to WM2 rims.
Perhaps the older Commandos came with a 3.50 x 19 rear?

Glen

Old Bloke · Mar 26, 2013

Bluto
Yes, I see theres no 90/90 rear its a 3.25-19 in universal, I remember you said that earlier.

Matchless
More options thank you.

Worntorn
New rims plus labour for a skilled person(should you find one) to fit them, yeah cheap option.
I can see some logic now for the forum post that said fit a 100/90 on the rear, then if you get a WM3 rim later it will fit that.
I am only about 160lbs plus gear, and only solo, so the weights not so much an issue.
meh, will sleep on it....

Peter

Snorton74 · Mar 26, 2013

100/90-19 Front, 120/90-18 Rear, with BT-45 Bridgestones.

worntorn · Mar 26, 2013

looks nice, what are the rim widths?

Glen

Snorton74 · Mar 26, 2013

2.15 Front WM-3, 2.75 Rear WM-4.5

DogT · Mar 26, 2013

My 'First edition May 1968' of the Riders Handbook lists 'Front: 3-00 by 19 in. ribbed WM2 wheel rim' and 'Rear: 3-50 by 19 in. GP WM2 wheel rim'.

I too found an Avon Speedmaster MKII ribbed in 3.00-19 and I got it from Walridge sometime after he told me it wasn't available, maybe back in 08 or so. But I'm using a 4.10H19 Roadrunner for the rear, my understanding it is really the same as the 3.50-19, but I'm not sure of that and it was not what I really wanted. It does look a bit thick on the rim.

Possm is the tyre-meister.

It depends on if you want original style or newer performance and then the front mudguard comes into the issue, at least for 68-70.

Dave
69S

cmessenk · Mar 26, 2013

Snorton74 said:
100/90-19 Front, 120/90-18 Rear, with BT-45 Bridgestones.

I'm curious what are the advantages / disadvantages of having a 19" front and an 18" rear??

Matt Spencer · Mar 26, 2013

Fatter tyre aft , for same rolling diameter . The extra width gets a little better side clearance , to reduce dragging ( of expensive parts on pavement, leant over ).

Also the extra Traction from the extra Rubber , enables extra Corner Speed , baggadge , load & cushion . Probly why Christianson likes 16s .

worntorn · Mar 26, 2013

Snorton74 said:
2.15 Front, 2.75 Rear.[/quote

That'll do it!
Snort, would you mind measuring the width of the 120 for me? I would like to see if I can fit one on the touring bike. You have good weight carrying capacity with that tire.

Glen

kirkemon · Mar 26, 2013

I really like the Dunlap GT501 on my W650

Snorton74 · Mar 26, 2013

worntorn said:
Snorton74 said:

2.15 Front, 2.75 Rear.[/quote

That'll do it!
Snort, would you mind measuring the width of the 120 for me? I would like to see if I can fit one on the touring bike. You have good weight carrying capacity with that tire.

Glen

Click to expand...

4-3/8 inches +or- I hope your wife doesn't see that better weight carrying capacity part. Ha

worntorn · Mar 26, 2013

Thanks, that will just fit.
I should be safe on the weight capacity thing, my wife doesn't log on to this forum....

Tires for my 69 Commando

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