18" rear wheel???

norton bob said:

I have 2 Nortons both slimlines, The 99 runs old style Avon Speedmaster/SM tyres on 19" slim std Rims ,has raised bars and weighty Craven Panniers. Handles perfectly and turns in well. Grip is a bit suspect on greasy wet roads. The Atlas has Modern tyres on 19 " Alloy rims with a WM3 on the back. Handles like a loaded truck. Would hate to have to change line mid corner. Don't ride it . Son thinks its OK , but as my brother used to ride a very bent 88 and thought it the best handling bike ever , I don't give much weight to others opinions !!.

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A featerbed Norton with 19 inch wheels and the 24.5 degree rake is usually a very precise nice handling bike. I stuffed my Triton by fitting 18 inch wheels front and back to get better rubber. The bike still handled OK, but in corners became neutral and very heavy to ride fast. With the Manx motor in the featherbed frame and 19 inch wheels, the bike oversteers slightly as you accelerate when on a lean. It inspires a lot of well-justified confidence. With the twin motors, the weight is a bit further back, so the bike is not as good to ride fast.

I have 19” rims 2:50 “ Avon roadriders front and rear handles like a dream

acotrel said:

If you don't usually carry a pillion passenger, softening the rear suspension might make a Commando with 19 inch wheels handle better. As you change the trail for any given rake on the steering head, the two handling extremes are self-steering. Lowering the back makes the bike self-steer a bit more in the correct direction as you accelerate through corners. If you raise the back or lower the front, you decrease the trail, and the bike will probably tend to run wide a bit more as you accelerate out of corners, and be more difficult to tip in as you brake for a corner.
When you get the handling right, the bike should tip in easily as you brake for the corner and feel very positive as you accelerate out - on a lean.
As you accelerate, the trail increases and it reduces as you brake. So the bike steers on the throttle and the brakes. If you get into a corner too hot, you have to choose a point at which you have to stop braking and accelerate. What the bike does then, is important for your health.

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Being a bit complicated for me to undestand those technical informations, I do like my Avon 120-80-18, WM3 mounted for the overall look. The Norton 19'' skinny look always promote some regurgitation for me... My next project is to lace Madass hub to a MT3.50 rim and fit a 130-70-18. Is it going to end as fatal crash for me?

Sergio said:

Being a bit complicated for me to undestand those technical informations

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Nobody understands Acotrel's handling opinions, its a unique take.

I run a 100/90-19 0n the front and a 120/90-18 on the rear (BT-45's). Both wheels are the same diameter, and it handles very well.

I had been running a 110/90-18 on the rear, and it did affect how well the bike turned-in in the corners, it was a bit more sluggish.

My $0.02 - FWIW

Some people do not discover there bike does not handle, until they get into a corner too hot. When that happens, it is normal to gently apply the front brake. The bike slows, but as the front goes down the bike tends to run wide faster. As the speed comes off, a point is usually reached where the rider must get back on the gas and ride out of the problem, or run out of road. Some bikes tend to oversteer as the front of the bike comes up. If they do that, the bike usually turns in the correct direction. There are no double lines in the middle of a race track, but on public roads, you can end up riding into the oncoming traffic if your bike does not turn when you gas it in the corner.

Derek Wilson said:

I run a 100/90-19 0n the front and a 120/90-18 on the rear (BT-45's). Both wheels are the same diameter, and it handles very well.

I had been running a 110/90-18 on the rear, and it did affect how well the bike turned-in in the corners, it was a bit more sluggish.

My $0.02 - FWIW

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I run a 4 inch rear tyre on the Seeley and you would not know it was there. But I have changed the fork yokes which drastically altered the steering geometry in a very beneficial way. The whole handling thing is a spectrum. As you decrease the yoke offset, you move your position in the handling spectrum from 'too wrong' to 'too good'. - It is the combination of rake and trail which affects where the self-steering occurs.. If you have very steep rake, changes in yoke offset make bigger differences to the handling.

Fat rear tyres do not necessarily give you more grip. They also change the alignment of the sides of the front and rear tyres, which can make the handling feel stiff.

I bought an Atlas 18" rear wheel and installed it directly onto my Commando. That is when I discovered that the offset is different. Luckily I was able to center the wheel right on the bike by adjusting the spokes. I like the 18 but I'm thinking of going with a WM4 19 shouldered aluminum Acront rim.

Sergio said:

Being a bit complicated for me to undestand those technical informations, I do like my Avon 120-80-18, WM3 mounted for the overall look. The Norton 19'' skinny look always promote some regurgitation for me... My next project is to lace Madass hub to a MT3.50 rim and fit a 130-70-18. Is it going to end as fatal crash for me?

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That is pretty wide. Doubt it would be a fatal crash, bit I do have to ask why so wide? 120 is plenty, and you could lace a WM4.

" I think I've read some threads or replies, that some install an 18" rear wheel on a Commando? Just curious, how it would affect the handling? "

T. C. favoured a 16 , in the days of the 5.10 - 16 Avon roadrunner .

Wider shoulder'd keep the pipes slightly ore favourably regarding grinding . Better rear brakeing two up touring .
If it works.
Better wear with the more rubber .

These guys dunno what a Contact Patch really is these days .



hats a Pirelli Licorice at 3 p.s.i. , thereabouts . You can see why it might not be to hot on Tarmac .
Was the Gun soft track tyre , around 1970 .

An Eighteen .



More Rubber'll go aft ( 4.25 0 with a 4.10 fwd . Rather'n the earlier P. R. 3.00 or 3 . 60 front .




It'll hook up better with better traction , in the quater mile .

I just finished putting an 18 inch WM3 Atlas rim with a 110/90x18 Avon tire on a 1974 850. The rim edge was exactly flat to the hub on the drive side and the tire ended up being exactly centered to the back bone of the frame when using a string down the center. There was about 3/8 inch clearance to the chain guard from the tire edge.

Okay I'll run the 4.00-18 on the WM3 rim at the rear and the 100/90-19 on the WM2 rim up front. Both should have the same 26.4" diameter.

Looks like we are at: 1. looks 2. handling and 3. tyre life not necessarily in that order.
I put a Avon RR 110-90-18" WM3 on my Rickman. As far as I can tell it handles about the same
and wears out just as fast as the 4.10 TT100 on before. So when that is shot it will be 100-90 RR
and Ill get to put the chain guard back on! I guess that is a tick in the "looks" department. Fatter
tyre looks a bit much for me anyway.

My personal experience:

I run a Bridgestone BT-46 120/90-18 on mine. The BT-46 has a dual rubber compound (harder center, softer sides) and is well suited to the type of riding I do here in SW Ontario - way too many straight sections of road…

The 120/90-18 is the same diameter as the 100/90-19 that I have on the front - and is the same diameter as the 4.10-19’s that the bike was originally fitted with - so the original geometry of the bike is maintained. As a result, the bike more readily “steers” into corners than it did when I was running the smaller diameter 110/90-18 on the rear

Tread life is very good, and I typically get between 5-6000 miles out of a rear tire.

My $0.02 CAD…

Derek Wilson said:

My personal experience:

I run a Bridgestone BT-46 120/90-18 on mine. The BT-46 has a dual rubber compound (harder center, softer sides) and is well suited to the type of riding I do here in SW Ontario - way too many straight sections of road…

The 120/90-18 is the same diameter as the 100/90-19 that I have on the front - and is the same diameter as the 4.10-19’s that the bike was originally fitted with - so the original geometry of the bike is maintained. As a result, the bike more readily “steers” into corners than it did when I was running the smaller diameter 110/90-18 on the rear

Tread life is very good, and I typically get between 5-6000 miles out of a rear tire.

My $0.02 CAD…

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Hi Derek,

I’ve just put the same rear and 90/90 18” on front . What pressures do you run ?
txs
TBW

I have experimented with this a little. With only the the rear 18" it does slow the steering (more like a chopper as mentioned). With 18" front and rear I find it a touch more marvelous than 19" f&r. I find 18" great for our two lane backroads but a little bit to sensitive for E-way.
This is with Avon tires AM-24 20 and 21. (72 commando)

TBW said:

Hi Derek,

I’ve just put the same rear and 90/90 18” on front . What pressures do you run ?
txs
TBW

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I run 26 psi in the front and 28 in the rear

norton bob said:

I have 2 Nortons both slimlines, The 99 runs old style Avon Speedmaster/SM tyres on 19" slim std Rims ,has raised bars and weighty Craven Panniers. Handles perfectly and turns in well. Grip is a bit suspect on greasy wet roads. The Atlas has Modern tyres on 19 " Alloy rims with a WM3 on the back. Handles like a loaded truck. Would hate to have to change line mid corner. Don't ride it . Son thinks its OK , but as my brother used to ride a very bent 88 and thought it the best handling bike ever , I don't give much weight to others opinions !!.

Click to expand...

If you increase the trail on your motorcycle, the only effect you are likely to notice is might not need to counter-steer to tip into corners. Most guys do not gas their bike really hard when they are halfway around a corner. I have read about bikes shaking their head as they accelerate down a straight, if the trail is increased. But I have never experienced it. Fitting softer rear springs might have more effect on the trail than fitting a smaller diameter rear tyre.
My Seeley 850 has about 106mm of trail with a rake of 70 degrees. My rear springs allow about 75mm of dip at the rear of the bike. I can just flip it into a corner while braking, then accelerate from a third of the way in, right around the corner. Nobody can beat that. It frightens me even thinking about it. The speed are extreme right around the corner. But you must brake into the corner then accelerate to get the back of the bike to go down, or the bike won't steer in the right direction. It always goes in the direction of lean. If you don't have enough trail, it goes in the other direction and runs wide. It also tends to stand up and turn the wrong way as you brake. It all happens at high speed, but you get used to it.