Fork yokes - simple question

[acotrel]

What were the yoke offsets for the first and second models of Commandos ? The first model was the crasher and the second did not have the problem. I can remember Hobot talking about reverse-steering to get his Commando to tip quickly into corners. I wonder it his bike also under-steered as he accelerated out of corners ?

 

[Matchless]

2 1/4" offset. Same as Domi / Atlas.

Martyn.

 

[dynodave]

all measured from original norton parts not aftermarket repops

7"slimline ?? 7-3/8 slimline & series 1 commando= 2.25" T&B

Series 2A(750)= top2.777" bottom 2.783"

Series 2B is 850/ANG top 2.851" bottom 2.689"

 

[rocketman71]

How about the offset on the N15/G15? I am thinking of changing to 7-3/8" Roadholders on My G12 Matchless so I can use a TLS Norton brake and wheel. I have the wheel and brake, sliders, and axle. I need everything else.

 

[grandpaul]

To understand hobot's thinking process, you must...

...wait...

hobot's thinking processes cannot be understood by the average mortal, unless you ride in THE gravel.

 

[Derek Wilson]

To understand hobot's thinking process, you must...

...wait...

hobot's thinking processes cannot be understood by the average mortal, unless you ride in THE gravel.

There is something to be said about that.... I ride in gravel quite regularly, and at speed too - gravel is an unforgiving mistress that will turn up handling issues that you never knew you that had!!

 

[maylar]

There is something to be said about that.... I ride in gravel quite regularly, and at speed too - gravel is an unforgiving mistress that will turn up handling issues that you never knew you that had!!

Ah, but you'd have to know our beloved Steve Shiver aka hobot. The road to his house is an uphill drive fraught with deer, wild boar and an occasional 3 ft giant turtle. That's THE gravel.

 

[grandpaul]

Ah, but you'd have to know our beloved Steve Shiver aka hobot. The road to his house is an uphill drive fraught with deer, wild boar and an occasional 3 ft giant turtle. That's THE gravel.

Yes, there is a UNIVERSE of difference between "gravel" and "THE gravel"...

 

[Craig]

Acotrel .... you could send a PM to Steve through this forum , no doubt he will give you the info you looking for .....

 

[Derek Wilson]

Ah, but you'd have to know our beloved Steve Shiver aka hobot. The road to his house is an uphill drive fraught with deer, wild boar and an occasional 3 ft giant turtle. That's THE gravel.

Well, you also assume that I do not know of him... and I never claimed to have ridden on THE Gravel.

 

[acotrel]

Then two offsets I am asking about are for the before and after when the early Commandos had their handling problem. What is the difference in the yokes ? I don't believe the frame was changed, but they fixed the problem. So it was probably a change in yoke offset. But I have never known what it was that they did.

 

[acotrel]

Steve Shriver was good hearted but a bit silly. That need to reverse-steer a Commando when tipping into corners has been mentioned by a few guys on this forum.

 

[o0norton0o]

Then two offsets I am asking about are for the before and after when the early Commandos had their handling problem. What is the difference in the yokes ? I don't believe the frame was changed, but they fixed the problem. So it was probably a change in yoke offset. But I have never known what it was that they did.

Here we go again.... The yoke offset was changed (made about 1/2" greater) AND the yoke angle was increased from 27 degrees to 28 degrees. The result was a minor increase in trail of the later model so it added a little bit of stability to the later model and made it a tiny bit heavier steering with a slightly slower response....

Could an average street rider get on the 2 slightly different front end geometry's and tell the difference? Probably not. Could an experienced racer tell the difference? Maybe... but I bet the stock commando is lacking so much other high performance suspension parts that you couldn't push the bike hard enough to find the point where that 5/8ths" of trail made one bike crash when the other bike didn't....

 

[baz]

If you are talking about just the early frame IE the 27° frame of the 750 the offset of the yokes was increased when they went from dommi/atlas's type yokes to commando yokes
The increase in offset (decreases) the trail and vice versa
So the very first commandos had more trail
This changed again with the 850 when it went to a 28° frame rake and yokes that were de raked by 1°

 

[dynodave]

Here we go again.... The yoke offset was changed (made about 1/2" greater) AND the yoke angle was increased from 27 degrees to 28 degrees. The result was a minor increase in trail of the later model so it added a little bit of stability to the later model and made it a tiny bit heavier steering with a slightly slower response....

OP:
What were the yoke offsets for the first and second models of Commandos ?

These are the 3 configurations
1. series 1 commando rolling chassis (68-69-70) used 27 deg (as I said in post #3) 2-1/4" offsert same as featherbed/all late slimline but all UN threads on commando triple trees

2. series 2A commando/ 71,72,73 750 rolling chassis still 27 degree but increased new fork offset and style top2.777" bottom 2.783"

3. series 2B commando / 850 rolling chassis NOW 28 degree and 850/ANG top 2.851" bottom 2.689"

 

[acotrel]

Do any of the Commandos have adjustable hydraulic steering dampers as standard fitting ? That 2-1/4" offset would make it handle like a race bike. It is good, but dangerous without a damper. I cannot remember any 1960s bikes which had adjustable hydraulic steering dampers other than H1 and H2 Kawasakis.. When I first started racing in historic events instead of normal open meetings,, I had a Kawasaki damper fitted to my Triton for a reason. I was ordered to take it off the bike by the scrutineers. That led to a crash which stppped me from racing for a very long time..
I cannot believe that Peter Williams would make a mistake when he specified the steering geometry for the first Commando. Norton were probably too cheapskate to copy the Japanese and fit a decent damper.
If you look at the history - Peter Williams raced Tom Arter's Wagon Wheels which looks very much like a Seeley and there was an association between Tom Arter anc Colin Seeley. All Seeleys have 27 degree rake on the steering head.. With Manx fork yokes, it is almost impossible to reduce the offset to get more trail. So the first Commandos would have had a lot.
Back when my fast friends were racing in the 1960s, some of their Manx Nortons had non-adjustable hydraulic steering dampers, but they were very rare.
You should not need to reverse-steer a Commando to get to tip into a corner. If I was racing one, I would go back to the Manx fork yokes.

 

[acotrel]

Apparently one of the things Joey Dunlop would never discuss was his steering damper - he used to wind it on as he raced.
Friction dampers do not give a progressive response to oscillations which increase in frequency.

 

[acotrel]

If you are talking about just the early frame IE the 27° frame of the 750 the offset of the yokes was increased when they went from dommi/atlas's type yokes to commando yokes
The increase in offset (decreases) the trail and vice versa
So the very first commandos had more trail
This changed again with the 850 when it went to a 28° frame rake and yokes that were de raked by 1°

Thanks very much for that. It is all starting to make some kind of sense to me now.
The Manx 2-1/4" = 55 mm offset, My TZ Yamaha yokes have 53 mm offset and I use them with 18 inch wheels at 27 degree rake on the steering head, and get a lot of over-steer if I accelerate hard when cranked over. The first Commandos probably had 19 inch wheels which would have given them even more trail. If you gassed one hard halfway through a corner, it would also probably over-steer.
In a Yamaha frame with 26 degree rake and 18 inch wheels the TZ yokes give neutral steering.
Modern Australian after-market featherbed frames usually have 26 degree rake instead of 24.5 degree, take 18 inch wheels and use Manx yokes. They handle like Suzukis.
Stability, over-steer and under-steer are three different things. My Seeley is stable, but over-steers. Braking into as corner, it is extremely direct. But I think that without the steering damper, it might wag it's head as it comes out of corners. I think I might be lucky I did not try to ride it without the damper. However the weight distribution might be better than it is with a Commando.