Front Tyre

Curious to know who runs a 90/90 tyre on a Commando front. I have a new Avon RR and it does seem a bit skinny.
Comments from those who actually run one?

I am sure you will get other comments from those who actually comply with experience of running the tyre on a Commando, but anyway:

Assuming RR is Road Rider and not Road Runner......I have ridden the tyres but not on a Commando, it won't look quite so skinny with air in.

I have a 19" in race compound on my Suzuki GT500 race bike, which is a similar weight to my Rickman, on a WM2 rim, and have had them in 18"on my Fury/Bandit framed Yamaha on a WM3 rim. My Rickman Norton which is a little lighter than a Commando runs a 90/90, 18" front, on a WM3 rim. Although my preferred race tyre is Heidenau or Avon (AM26 front, race compound Road Rider) my road choice on 19" or 18", would be 90/90 Road Rider.

90/90 19" is close to the 3.60 front on a WM2 that early Commandos were delivered with. The 4.10 was an economy measure at Norton, not an intended performance upgrade. People will individually prefer a 90/90 or a 100/90 on WM2 or WM3 rims (or even WM4!).

You won't know which you prefer until you try, I wouldn't use anything other than a 90/90 by choice, far better turning than 100 or 110 front tyres. Most of the classic racers on Nortons in 500, 750 or 900 class that I have seen in Europe run the 90/90 size front, either Avon, Continental and a few like me, Heidenau.

I run a 90/90 by preference and this is the tendency for Norton owners in my area. The 90/90 seems to turn in better, making the bike seem to handle better. I have run both 100/90 and 90/90 but only use 90/90 now. I note that I also run a 19in rear rim. Best.

Onder said:

Curious to know who runs a 90/90 tyre on a Commando front. I have a new Avon RR and it does seem a bit skinny.
Comments from those who actually run one?

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What are you matching it up to on the rear?

The problem IMO with the 90/90 is the section, not the width, it is a very low profile. So it might not suit your choice of rear. And IMHO they just look ‘wrong’ (I said IMHO… not looking for an argument here) !

The 90/90 has a diameter of 25.5”

The recommended (by Avon) 100/90 is 26.4”

That’s a big difference.

If you want narrow without the low profile, the 3.25 19 is a better choice with a 26.1” diameter.

I run a 100 / 90 / 19 front on the Commando with a 4.00 / 18 rear. I like the bigger contact patch of the 100 (even if that’s just psychological) and this combo gives the same diameters front and rear.

On two other bikes I run the 3.25 / 19 with the 4.00 / 18 and, honestly, that set up seems just as good.

I might try a 3.25 /19 on the Commando one day, but thus far I’ve been loath to tamper with what works !

I have run the 90/90 front for years. It is a lot quicker stearing . It works well for my riding BUT it can feel nervous at speed . i would not recommend it if you do a lot of interstate riding.

I have 90/90 19 on the front and 100/90 19 roadriders on the back of my 750 commando
The handling and road holding are impeccable

I run 90/90 front for last decade, quicker steering than the 100/90's I used before and no running out of tyre before stopping.

Onder said:

Curious to know who runs a 90/90 tyre on a Commando front. I have a new Avon RR and it does seem a bit skinny.
Comments from those who actually run one?

Click to expand...

90/90 is acceptable on a rim width 1.85(WM2) and belongs on a 2.15(WM3)
100/90 is acceptable on a rim width 2.15(WM3) and belongs on a rim width 2.50

According to this: http://www.britishcycle.com/Manuals/Wheel_rim_tyre_sizes.pdf

Assuming you have WM2 front and rear Avon 90/90 is acceptable front and rear and 100/90 is not acceptable even though many, including me, use it on the rear.

Interesting information on V rating vs H rating on the 100/90-19 series Front tire.

I run a 100 / 90 / 19 front on the Commando with a 4.00 / 18 rear. I like the bigger contact patch of the 100 (even if that’s just psychological) and this combo gives the same diameters front and rear.

On two other bikes I run the 3.25 / 19 with the 4.00 / 18 and, honestly, that set up seems just as good.



OK, all those running 90-90 have disc brakes?
Second question: FE, does the 400-18 have a longer life than the 100-90?
My old Avon Speedmassa 400-18 lasts forever on my big Enfield. Is this just
a factor of the square profile?

IMHO when you put tires on rims smaller than the tires were designed for you are punished in two ways. 1) PITA getting them on. 2) Tire wear due to them not being shaped as designed once on and inflated. Also, I wonder if an Avon 100/90 properly inflated actually has more contact area than a 90/90 properly inflated since the 100/90 will be rounder than designed.

I haven't a clue why Norton used WM2 rim front and rear. It certainly wasn't what others I know about were doing and AFAIK, not what Dunlop was recommending.

marshg246 said:

IMHO when you put tires on rims smaller than the tires were designed for you are punished in two ways. 1) PITA getting them on. 2) Tire wear due to them not being shaped as designed once on and inflated. Also, I wonder if an Avon 100/90 properly inflated actually has more contact area than a 90/90 properly inflated since the 100/90 will be rounder than designed.

I haven't a clue why Norton used WM2 rim front and rear. It certainly wasn't what others I know about were doing and AFAIK, not what Dunlop was recommending.

Click to expand...

Greg, don’t forget that some people mount their 100 / 90s on the correct rim…

Onder said:

I run a 100 / 90 / 19 front on the Commando with a 4.00 / 18 rear. I like the bigger contact patch of the 100 (even if that’s just psychological) and this combo gives the same diameters front and rear.

On two other bikes I run the 3.25 / 19 with the 4.00 / 18 and, honestly, that set up seems just as good.



OK, all those running 90-90 have disc brakes?
Second question: FE, does the 400-18 have a longer life than the 100-90?
My old Avon Speedmassa 400-18 lasts forever on my big Enfield. Is this just
a factor of the square profile?

Click to expand...

Front tyres have less tread depth than rear. Universal tyres designed for front or rear have something in between.

The 100/90 is a universal tyre and has 5.6mm tread depth.

The 4.00 / 18 is a rear tyre and has 7.5mm tread depth.

The 4.00 therefore has 34% deeper tread… that’s 34% more mileage.

Scroll down on this page, Avon put LOTS of info on their site about their tyres:

Fast Eddie said:

Greg, don’t forget that some people mount their 100 / 90s on the correct rim…

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No doubt, but I bet more put them on WM2 since that's what the bike came with.

Of course, if you have the correct rim for the tire there is no issue. Said better: I wonder if an Avon 100/90 on a WM2 rim and properly inflated actually has more contact area than a 90/90 on a WM2 rim and properly inflated since the 100/90 will be rounder than designed.

marshg246 said:

Said better: I wonder if an Avon 100/90 on a WM2 rim and properly inflated actually has more contact area than a 90/90 on a WM2 rim and properly inflated since the 100/90 will be rounder than designed.

Click to expand...

Good question. I know we’re not tyre scientists and this is perhaps rather crude, but…

I’ve just mounted a new front 100 /90 on my 2.5 rim.

If you post some shots of one on the stock rim, showing the profile as best you can, I’ll try and match the shots and perhaps we can see what the difference looks like?

Drive on a dusty road a bit then on to smooth pavement. Look at the amount of tyre contact I am always amazed how little it is. I am willing to bet that the big front tyre has about the same contact as the smaller for normal driving. What I wonder about is the contact patch under heavy braking.

Onder said:

Drive on a dusty road a bit then on to smooth pavement. Look at the amount of tyre contact I am always amazed how little it is. I am willing to bet that the big front tyre has about the same contact as the smaller for normal driving. What I wonder about is the contact patch under heavy braking.

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Indeed.

Its the contact patch under heavy braking and whilst at lean that matters most.

When I looked at the radius of the profiles (with my totally uneducated eye) my conclusion was / is that the 100 /90, on the correct rim, provides for a worthwhile increase in contact at lean.

Even if I’m wrong, it’s worth it just for the placebo effect !

Yesterday I was out and about on the 74 mk2. New TT100 fore and aft. At lean you will, due to the design profile of the tyre, get more contact patch than straight up. They felt fine but truthfully unless the road surface is new and smooth I doubt I could tell the difference between the Dunlop and the Avon RR.
Certainly have noted FE's point about the tread depth. And yes, TT100 tyre life is about the same as a fly in summertime.

Fast Eddie said:

Good question. I know we’re not tyre scientists and this is perhaps rather crude, but…

I’ve just mounted a new front 100 /90 on my 2.5 rim.

If you post some shots of one on the stock rim, showing the profile as best you can, I’ll try and match the shots and perhaps we can see what the difference looks like?

Click to expand...

I'll see what I can do on pictures. Not sure which I have that I can get to right now. I know I have 90/90 on WM2.

Thought experiment - look at your 100/90 on 2.5" rims. Now imagine the beads 0.65" closer together. Or consider that 2.5 is 64% of the tire width and 1.85 is 46%. of the wire width. My assumption is that with 100/90 on WM2 the center will wear faster than it should as the contact patch will be narrower.

On the front tyres go on until outdated. One the back they seem like a monthly bill. Warmer temps mean faster wear
as does a heavier rider but noticeable, unless crossing the desert probably rather unlikely.