1973 Norton Commando 750 rear tire

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MLW9110

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My 1973 Commando 750 has Avon Roadrider Mk II 100/90-19 tires on the front and rear. The rear tire has a date code of 4212 so I want to replace it. The rider's manual specifies a 4.10-19 tire but there won't be clearance to the chain guard with a tire wider than the 100/90-19 (3.5-19).

I'd put a new Avon the same as what's on now if I could find one.

Anyone know where I can get tha Avon? What might be a good substitute?

Mike-Bremerton, WA
 
https://www.motosport.com/ has the front 100/90-19 in stock - all the rears are out of stock. You might ask them for an arrival date. Amazon normally has a stock but they are out.

Are you sure you got the date code right? I think that means the 42nd week of 2012 and AFAIK the MKII were introduced in 2019. I may be wrong on both because the AVON pages that announced them seem to be gone as well as their date decoder page.
 
The date code is correct. The rear tire isn't a MKII.

The MKII on the front has rotation arrows for both front and rear use.
 
Another suggestion is to see if a 325x19 Avon Roadrider is available if so fit it to the front and put the 100/90x19 you
have on the rear, you will find your bike will corner nicer with this combination.
 
possm said:
Another suggestion is to see if a 325x19 Avon Roadrider is available if so fit it to the front and put the 100/90x19 you
have on the rear, you will find your bike will corner nicer with this combination.
Click to expand...
Good idea, but 3.25-19 are out too. However 90/90-19 are available at Motosport so a new front and move the current to the rear is a good option.
 
MLW9110 said:
My 1973 Commando 750 has Avon Roadrider Mk II 100/90-19 tires on the front and rear. The rear tire has a date code of 4212 so I want to replace it. The rider's manual specifies a 4.10-19 tire but there won't be clearance to the chain guard with a tire wider than the 100/90-19 (3.5-19).

I'd put a new Avon the same as what's on now if I could find one.

Anyone know where I can get tha Avon? What might be a good substitute?

Mike-Bremerton,
Click to expand...
​




MLW9110 said:
My 1973 Commando 750 has Avon Roadrider Mk II 100/90-19 tires on the front and rear. The rear tire has a date code of 4212 so I want to replace it. The rider's manual specifies a 4.10-19 tire but there won't be clearance to the chain guard with a tire wider than the 100/90-19 (3.5-19).

I'd put a new Avon the same as what's on now if I could find one.

Anyone know where I can get tha Avon? What might be a good substitute?

Mike-Bremerton, WA
Click to expand...
Try J&P cycles
I’m






 
Last edited:
MLW9110 said:
My 1973 Commando 750 has Avon Roadrider Mk II 100/90-19 tires on the front and rear. The rear tire has a date code of 4212 so I want to replace it. The rider's manual specifies a 4.10-19 tire but there won't be clearance to the chain guard with a tire wider than the 100/90-19 (3.5-19).

I'd put a new Avon the same as what's on now if I could find one.

Anyone know where I can get tha Avon? What might be a good substitute?

Mike-Bremerton, WA
Click to expand...
BTW, the bike probably came with Dunlop 4.10-19 TT100 tires. 4.10-19 is usually considered the equivalent of 100/90-19

Considering widths:
80mm = 3.15"
90mm = 3.54"
100mm = 3.94"
110mm = 4.33"

3.25 - 19 is between 80/90-19 and 90/90-19
3.5 - 19 close to 90/90-19
4.10-19 is between 100/90-19 and 110/90-19

IMHO, if using Avon RoadRider MKII either 90/90-19 front and 100/90-19 rear or 100/90-19 front and rear

Some use 110/90-19 on the rear. They are only .2" wider on each side than 100/90-19.
 
That's a really helpful summary. Thank you, will come back to it when mine are due.

Am I right that there are no Avon Roadrider 19" rears, just a front turned around for the opposite tread direction?
 
Mart UK said:
That's a really helpful summary. Thank you, will come back to it when mine are due.

Am I right that there are no Avon Roadrider 19" rears, just a front turned around for the opposite tread direction?
Click to expand...
Yes, the dedicated rears are gone. Now we live with 2/3 tread depth repurposed fronts. 🤬
 
Mart UK said:
That's a really helpful summary. Thank you, will come back to it when mine are due.

Am I right that there are no Avon Roadrider 19" rears, just a front turned around for the opposite tread direction?
Click to expand...
Almost. The universals have more tread than a dedicated front, and less than a dedicated rear (2/3s ish as concours said) with the accompanying reduced mileage.
 
Last edited:
That seems the same on my Dunlop 4.10 TT100s. Same tyre with direction swapped round. The rear is nearly done at 4,000 miles, the front looks nearly new. I have 19" front and 18" rear Roadriders on my CB750K6 which are a dedicated front/rear set and are wearing more closely together. That said, looks like they'll both need changing around 6k miles. Softer rubber, but a nice tyre.
 
Mart UK said:
That's a really helpful summary. Thank you, will come back to it when mine are due.

Am I right that there are no Avon Roadrider 19" rears, just a front turned around for the opposite tread direction?
Click to expand...
No, they have front, rear, and front/rear.
 
3.25 - 19 is between 80/90-19 and 90/90-19

Greg if you look at Avon's website the 325x19 RR2 has the same width as a 90/90x19 but has a higher profile there for "fills the guard better"
I am running said combo on my Mk3
 
possm said:
3.25 - 19 is between 80/90-19 and 90/90-19

Greg if you look at Avon's website the 325x19 RR2 has the same width as a 90/90x19 but has a higher profile there for "fills the guard better"
I am running said combo on my Mk3
Click to expand...
Many sites say different things but unless I did the math wrong, I am right based on standard tire sizing. They also say:

1973 Norton Commando 750 rear tire


So, their 90/90-19 is really a 99/90-19 (3.9" wide)? Then they say the width is 3.9" which agrees with 99mm. So the 90/90-19 is 99 wide or 3.9" wide and the 3.25-19 is 98 or 3.9" wide. Funny that they are wider than a 3.5-10 and almost as wide as 4.00-199

Neither of those fit the tire sizing standards!

By the same token their 100/90-19 are 109 wide?

I'm in the hospital so I can't go measure.

Dunlop K70 specs (still not matching the standard tire sizing but closer):

1973 Norton Commando 750 rear tire
 

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Agreed Greg, I spent 15 years as a rep in the motorcycle tyre trade, I found tyre sizing could vary over 10% between manufacturers!
 
I'm enjoying the comments here and adding the tire size comparisons to what I know. Of all the possible sizes that might work I can't find a tire suitable for the rear wheel. All the tires that come up in my searches are out of stock.
 
Another possibility is a 410x19 TT100 on the rear and if available in your country a 100/90x19 TT100GP for the front, the 100/90x19 is slightly narrower than the 410 and Being a GP compound is slightly stickier [Not recommended for the rear of a road bike]
 
possm said:
Another possibility is a 410x19 TT100 on the rear and if available in your country a 100/90x19 TT100GP for the front, the 100/90x19 is slightly narrower than the 410 and Being a GP compound is slightly stickier [Not recommended for the rear of a road bike]
Click to expand...
I'm going to have to find the max width dimension. I need to make sure the clearance to the chain guard will be sufficient.
 


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