Commando High Speed Stability

It's interesting to have two MkIII's to compare against each other. My Fastback, completely re built and everything in tip top shape feels somewhat light in the front end at speeds over 70mph. It has been fitted with an 18" alloy rear wheel and 19" up front.

My MkIII Roadster has steel wheels 19" front and rear and is rock solid in the front end all the way up and beyond 100mph.

Both bikes are running 4.10 Dunlop TT100"s front and rear. I suspect the smaller rear wheel on the Fastback has something to do with the high speed feel difference between the two. Sounds unlikely perhaps but I'm going to swap it for a 19" alloy rear and see what if anything changes. I'm also fitting 3.60 TT100's to the front of both bikes because I don't believe Norton should have ever gone fat at the front which they did in 72.. Steering will be extra precise and impeccable running the 3.60's up front.

I'm thinking I'll get the Candy Apple Roadster repainted black with gold pin striping and rear and front fenders (custom from CNW) painted the same, along with black handlebars. With Corbin seat it will look very special. Black, chrome and shiny alloy.

Nothing like having fun projects to work on and think about.

Phil

phil yates said:

My MkIII Roadster has steel wheels 19" front and rear and is rock solid in the front end all the way up and beyond 100mph.

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So, to sum up, your Mk3 runs like a dream, and you are going to change tyres because something must be wrong. ???
And a great colour scheme in excellent condition is going to be overpainted like a Velocette.
(sorry all those black-n-gold owners already out there - including me, I have tank n sidecovers in that scheme !)


Is it April 1st ??

Phil, Bike may/June 73


For your perusal.

Rohan said:

And a great colour scheme in excellent condition is going to be overpainted like a Velocette.
(sorry all those black-n-gold owners already out there - including me, I have tank n sidecovers in that scheme !)
Is it April 1st ??

Click to expand...

Every day is April 1st now.

I never did see the attraction of painting bikes to look like a mobile wake.
Candy apple red looks like a 100 mph standing still, hip then, hip now. 8)

Rohan said:

phil yates said:

My MkIII Roadster has steel wheels 19" front and rear and is rock solid in the front end all the way up and beyond 100mph.

Click to expand...

So, to sum up, your Mk3 runs like a dream, and you are going to change tyres because something must be wrong. ???
And a great colour scheme in excellent condition is going to be overpainted like a Velocette.
(sorry all those black-n-gold owners already out there - including me, I have tank n sidecovers in that scheme !)


Is it April 1st ??

Click to expand...

Rohan
Read my post again, properly. Then you can ask me some questions if you want to.

Phil

Time Warp said:

Rohan said:

And a great colour scheme in excellent condition is going to be overpainted like a Velocette.
(sorry all those black-n-gold owners already out there - including me, I have tank n sidecovers in that scheme !)
Is it April 1st ??

Click to expand...

Every day is April 1st now.

I never did see the attraction of painting bikes to look like a mobile wake.
Candy apple red looks like a 100 mph standing still, hip then, hip now. 8)

Click to expand...

I've already got a red one Time.
Just looking to do something different. I always liked the black Roadsters with gold pin striping. Matter of choice totally. I like Vincents too. Why would anyone else care what colour I choose? Might not change it at all but guards are going to be painted so now is the time to decide what colour I fancy. Maybe the next super charged one can be Candle Apple. Haven't decided on that one either.

Phil

Phil

My two glass tanks were pumped by age and ethynol black metal tank ,early Tupperware ,old oil tank and side panel painted black still not a patch on BRG but it was a laugh getting the gear.


There's the workshop dog waiting for a chase.

Even a touch of gravel there for the hobot man!
What's the point of having motorbikes if you can't spent a fortune on them, just ask L.A.B man he's an animal at that!
And hobot , and many more!
Happy days!

The combination of rake and trail together determine the way the bike steers. If the back of the bike is slightly lower that affects the steering. So softer spring on the back changes the way the bike handles as you gas it. Skinny tyres tend to make the bike more nimble. Probably your best option for the commando is the proven pair of 19 inch wheels fitted with the standard skinny tyres, unless you can find an easy way to alter the rake and the fork offset (trail). Then you get into uncharted waters. The changes which can alter the handling are very subtle.

The radius of a 18 and 19 can't be that much different, all the pics seem to show that Fastback MK111 as a tail dragger, maybe the shocks are the problem length or the loaded sag setting (low spring rate)

That Roman Purple might be just the colour for my fastback even though the paint on it is new.

acotrel said:

The combination of rake and trail together determine the way the bike steers. If the back of the bike is slightly lower that affects the steering. So softer spring on the back changes the way the bike handles as you gas it. Skinny tyres tend to make the bike more nimble. Probably your best option for the commando is the proven pair of 19 inch wheels fitted with the standard skinny tyres, unless you can find an easy way to alter the rake and the fork offset (trail). Then you get into uncharted waters. The changes which can alter the handling are very subtle.

Click to expand...

Thanks acotrel
It's hard to describe the difference between both bikes. Maybe a lot of folk wouldn't even notice it but I do. The Fastback steers beautifully and is perfectly stable, but up over 70mph the steering is just a little on the sensitive side. The Roadster is identical but it feels more at home above 70mph than does the Fastback. I've ridden enough Commandos to know exactly how they should feel. Tyre size 4.10 rear and 3.60 front are for two reasons, well three I guess. Firstly, CNW's custom guard will not allow a 4.10 front tyre. Secondly, I prefer the super precise steering of such. Thirdly, I don't like (never did) the look of the "fat" 4.10 up front. The Commando started out with a 3.25 front tyre then ended up in 72 switching to a 4.10. Matt from CNW and I have discussed this very issue and we think we know the reasons for this. Nothing to do with improved handling.

It's an expensive exercise to change to a 19" rear alloy wheel, but I'll sell the 18". I still have to deck the Roadster out with alloy wheels too. That's after two FCR carbi's, worked Fullauto head etc. Corbin seat alone I think from memory was over $400.

But acotrel, this is nothing compared to racing costs, as you well know.

Phil

Time Warp said:

The radius of a 18 and 19 can't be that much different, all the pics seem to show that Fastback MK111 as a tail dragger, maybe the shocks are the problem length or the loaded sag setting (low spring rate)

That Roman Purple might be just the colour for my fastback even though the paint on it is new.

Click to expand...

The radius difference between an 18 and 19 does not require a mathematical genius to work out Time. I'll give you extended time on this one. But I'll give you marks for observation. I see the lower tail too but I think it is the wheel difference as it looks the same when riderless. I'll bet a 19" rear changes the high speed handling, or steering more to the point. I could swap one with the other bike but I want a rear 19" on the fastback regardless. I never did like the idea of modifying wheel sizes.

A colour for you? Definitely pink ole buddy!

Phil

auldblue said:

Phil

My two glass tanks were pumped by age and ethynol black metal tank ,early Tupperware ,old oil tank and side panel painted black still not a patch on BRG but it was a laugh getting the gear.

There's the workshop dog waiting for a chase.

Even a touch of gravel there for the hobot man!
What's the point of having motorbikes if you can't spent a fortune on them, just ask L.A.B man he's an animal at that!
And hobot , and many more!
Happy days!

Click to expand...

I love BRG auldblue but have had four of them. Time for different things for me.

Phil

About most important thing to sense of nice secure ride/handling is condition of tyres and the www is full of tales of frustrated riders grinning after new tire fitted in 19" or 18" mixed and matched don't hardly matter to the thoughtless speeding even to the too soon fouling of big ole lugging MkIII cruisers. Too soft a headsteady can aggravate steady as she goes sense. A real investigator would switch wheels from one MK3 to the other to see what happens to make sense of it. When Peel was able to hit over 130 routinely I got a bit scared of the unknown pressing faster coming down Mt. slopes so asked racers and land speeders what to expect and was told no one has yet found out how fast a Commando can goes before it gets upset with plain speed on somewhat rough windy conditions. 70 mph is loafing easy speed to even a Mk***.

hobot said:

About most important thing to sense of nice secure ride/handling is condition of tyres and the www is full of tales of frustrated riders grinning after new tire fitted in 19" or 18" mixed and matched don't hardly matter to the thoughtless speeding even to the too soon fouling of big ole lugging MkIII cruisers. Too soft a headsteady can aggravate steady as she goes sense. A real investigator would switch wheels from one MK3 to the other to see what happens to make sense of it. When Peel was able to hit over 130 routinely I got a bit scared of the unknown pressing faster coming down Mt. slopes so asked racers and land speeders what to expect and was told no one has yet found out how fast a Commando can goes before it gets upset with plain speed on somewhat rough windy conditions. 70 mph is loafing easy speed to even a Mk***.

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hobot
I could investigate but prefer expensive changes. I like 19" rear regardless. 70mph is not fast but 110mph approx is tops.

Phil

I think black looks good.
Mittagong branch Norton office preparing for additions.

Phil

phil yates said:

auldblue said:

Phil

I love BRG auldblue but have had four of them. Time for different things for me.

Phil

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Click to expand...

Check ur tyre pressures , have you,!

auldblue said:

phil yates said:

auldblue said:

Phil

I love BRG auldblue but have had four of them. Time for different things for me.

Phil

Click to expand...

Click to expand...

Check ur tyre pressures , have you,!

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32psi rear
28psi front

Same for Roadster.

Phil

Or maybe Canary Yellow?
Vivian Neve included.

Phil

A quick bit of math shows the trail decreasing about 1/8" for every 1/2" decrease in rear wheel rolling radius. A 1/4" drop of the front forks to increase the trail helped plant the front end of the BSA B50MX when flat-tracking, so I can see where that could be felt at speed on the tarmac.

hobot said:

A real investigator would switch wheels from one MK3 to the other to see what happens to make sense of it.

Click to expand...

Yeah, Phil; listen to Steve! You have the perfect troubleshooting tool in front of you, and yet, you'd rather throw money at it. What's with you, man? I'll PM my Paypal account to you. Send me your extra cash, and I'll get back to you with my findings.

Nathan

Nater_Potater said:

A quick bit of math shows the trail decreasing about 1/8" for every 1/2" decrease in rear wheel rolling radius. A 1/4" drop of the front forks to increase the trail helped plant the front end of the BSA B50MX when flat-tracking, so I can see where that could be felt at speed on the tarmac.

hobot said:

A real investigator would switch wheels from one MK3 to the other to see what happens to make sense of it.

Click to expand...

Yeah, Phil; listen to Steve! You have the perfect troubleshooting tool in front of you, and yet, you'd rather throw money at it. What's with you, man? I'll PM my Paypal account to you. Send me your extra cash, and I'll get back to you with my findings.

Nathan

Click to expand...

I have learnt in the past, that what you don't spend of your money on Nortons, women will spend it for you on anything BUT Nortons. It is a race to the bottom.

In any case, why bother? I want a 19" rear wheel regardless. Fitting 3.60 front tyres to both bikes will be most interesting. With already knife edge steering, I can imagine how the 3.60 up front will feel. 4.10's removed will become spare rears, no wastage here at Mittagong Norton.

hobot mentions something about too soft a head steady. Nothing up there much adjustable beyond ensuring no slop in bearings. But I guess could be pinched up a tad to see if any difference. So Roadster handles best of the two, but slop in the gear change needs attention as primary case bush appears worn. Roadster clutch action is typical "spring release" in feel whereas Fastback is lighter and more progressive, same with front brake. These variations make for a lot of fun working to equal one with the other. The great thing with having two Commandos is that down time on either does not leave you without a Norton to ride. I couldn't go a week without a ride on a Commando. Life would be miserable indeed. The up and coming super charger project will be a whole new world again and I have already spoken to Jim Comstock about this. Jim is building a strong billet engine and plans to work on an upgraded transmission as well. The result will be very interesting with regards to blowing the engine. The downside will be the requirement to renovate every room in the house. One new Norton equals one new room renovation in the ratio of 1:3 money wise. One super charger equals one whole house, I am told!

Nortons are a very expensive past time. The upgrade addiction is shockingly expensive.

Phil