750 Triple Tree

Deckard

Deckard

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There has been enough thread discussion of 750 vs. 850 triple trees in the past. As an owner of a '71 750, I never did see anything definitive as to what was the difference was between '71-73 750's. Just that '71's were twitchy at high speeds. Even that may be Urban Legend.
Madass140 and CNW offer custom one's. Madass's looks to be a 68-70 replica, So suspect that is what it is. Neither he or Matt have model specific options for ordering. Don hasn't answered me about whether his is TT is angled (850) or parallel (750).
I suspect both are 850 angled, as that it could be installed on either model. Enough said about putting a 750 TT on a 850 and changing the trail.
850 TT on a 750 will change trail, but just would make it less responsive.
Owning both, I did like the 750 handling better than the 850, all things equal with a better headsteady.

Maybe some clarification by someone knowledgeable would help as far as if there is any real differences between '71 and '72 750's TT.
1973 is a crap shoot, it may be a 850 frame and TT.
 
Deckard said:
As an owner of a '71 750, I never did see anything definitive as to what was the difference was between '71-73 750's.

Maybe some clarification by someone knowledgeable would help as far as if there is any real differences between '71 and '72 750's TT.
1973 is a crap shoot, it may be a 850 frame and TT.
Click to expand...



There's no difference between '71 - '73 750 yokes/trees. They are the same parts (061915 and 061916).
The difference is between 750 and 850 yokes identified by the 'ANG' markings (and different casting numbers) on the underside of the 850 yokes.

*Edit: Lower yoke 061916 is one of those rare occasions where casting and part numbers are identical.
The 750 upper yoke, however, is part 061915, but the casting number is (NM) 061917.
 
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Deckard said:
There has been enough thread discussion of 750 vs. 850 triple trees in the past. As an owner of a '71 750, I never did see anything definitive as to what was the difference was between '71-73 750's. Just that '71's were twitchy at high speeds. Even that may be Urban Legend.
Madass140 and CNW offer custom one's. Madass's looks to be a 68-70 replica, So suspect that is what it is. Neither he or Matt have model specific options for ordering. Don hasn't answered me about whether his is TT is angled (850) or parallel (750).
I suspect both are 850 angled, as that it could be installed on either model. Enough said about putting a 750 TT on a 850 and changing the trail.
850 TT on a 750 will change trail, but just would make it less responsive.
Owning both, I did like the 750 handling better than the 850, all things equal with a better headsteady.

Maybe some clarification by someone knowledgeable would help as far as if there is any real differences between '71 and '72 750's TT.
1973 is a crap shoot, it may be a 850 frame and TT.
Click to expand...
I believe all readily available aftermarket triple trees are parallel bored, not angled / offset.
 
L.A.B. said:
There's no difference between '71 - '73 750 yokes/trees. They are the same parts (061915 and 061916).
The difference is between 750 and 850 yokes identified by the 'ANG' markings (and different casting numbers) on the underside of the 850 yokes.

*Edit: Lower yoke 061916 is one of those rare occasions where casting and part numbers are identical.
The 750 upper yoke, however, is part 061915, but the casting number is (NM) 061917.
Click to expand...
Thanks L.A.B.
As owners of 750's found out, the lower casting had a hole drilled through that number, so all you see is 06 :)
 
Deckard said:
As owners of 750's found out, the lower casting had a hole drilled through that number, so all you see is 06 :)
Click to expand...

Not always. The number (061916) can be in a different location away from the steering damper hole. ;)

750 Triple Tree
 
The handling of the first Commandos was a source of embarassment for Peter Williams. I suggest the trail was then reduced. If your bike does not tip into corners easily as you brake - that is a sign of insufficient trail. The castor effect does not seem to be what many people might think. If you increase the trail and get into a corner too hot, when it becomes time to accelerate again, the bike witll tend to turn more in the direction in whch you want to go, instead of running wide. Reducing the yoke offset, increases the trail. But when you do that, other things come into play - you need a steering damper. Decreasing the wheel size reduces the trail. and decreasing the rake also reduces the trail.
I do not ride bikes which have drum brakes and no steering damper - it is a recipe for disaster.
Increased trail makes the bike more nimble, reduced trail makes it more stable. If you fitted Manx Norton fork yokes to your Commando, the bike would oversteer a lot when you gassed it. But without a steering damper, you would probably crash a lot. The Manx has very steep rake, 19 inch wheels , and the yoke offset is at the minimum achievable for that type of yoke. Getting more trail on a Manx is almost imposiible without frame changes.
 
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Interesting history lesson. I've not seen 750 casting numbers in that position on the lower part of the tree before.

Additional query was set to NYC to find out if their offering is parallel or angled.
 
acotrel said:
The handling of the first Commandos was a source of embarassment for Peter Williams. I suggest the trail was then reduced. If your bike does not tip into corners easily as you brake - that is a sign of insufficient trail. The castor effect does not seem to be what many people might think. If you increase the trail and get into a corner too hot, when it becomes time to accelerate again, the bike witll tend to turn more in the direction in whch you want to go, instead of running wide. Reducing the yoke offset, increases the trail. But when you do that, other things come into play - you need a steering damper. Decreasing the wheel size reduces the trail. and decreasing the rake also reduces the trail.
I do not ride bikes which have drum brakes and no steering damper - it is a recipe for disaster.
Increased trail makes the bike more nimble, reduced trail makes it more stable. If you fitted Manx Norton fork yokes to your Commando, the bike would oversteer a lot when you gassed it. But without a steering damper, you would probably crash a lot. The Manx has very steep rake, 19 inch wheels , and the yoke offset is at the minimum achievable for that type of yoke. Getting more trail on a Manx is almost imposiible without frame changes.
Click to expand...

Here you go again.

Please tell us all what Commando frame you think Peter Williams designed ?

Stefan Bauer, Bernard Hooper and Bob Trigg would love to know., so they can stop turning in their graves.

ONCE AGAIN please do some research before posting any more fiction
 
So, we've cleared up that all 750 triple trees are the same from 71-73

No reason to debate the history of how the neck angle changed from 63 degrees for 750 to 62 degrees for 850 along with a different triple tree.

What I'd really like to know is what the aftermarket trees are. I forgot NYC's offering.
Since all the three offerings are universal to Commandos, I suspect they are not parallel, but angled (ANG) for 850 frames and capable of fitting to 750. They would just change trail on a 750 if that was the case. Whether a 750 benefits from that is subjective to the rider.
 
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Deckard said:
So, we've cleared up that all 750 triple trees are the same from 71-73

No reason to debate the history of how the neck angle changed from 63 degrees for 750 to 62 degrees for 850 along with a different triple tree.

What I'd really like to know is what the aftermarket trees are. I forgot NYC's offering.
Since all the three offerings are universal to Commandos, I suspect they are not parallel, but angled (ANG) for 850 frames and capable of fitting to 750. They would just change trail on a 750 if that was the case.
Click to expand...
I don't know about NYC yokes
But I'm pretty certain the CNW one's are parallel be it for the 750 or 850 frame ?
 
Deckard said:
So, we've cleared up that all 750 triple trees are the same from 71-73

No reason to debate the history of how the neck angle changed from 63 degrees for 750 to 62 degrees for 850 along with a different triple tree.

What I'd really like to know is what the aftermarket trees are. I forgot NYC's offering.
Since all the three offerings are universal to Commandos, I suspect they are not parallel, but angled (ANG) for 850 frames and capable of fitting to 750. They would just change trail on a 750 if that was the case. Whether a 750 benefits from that is subjective to the rider.
Click to expand...
Like I said already, I’m pretty sure you’re gonna find that the readily available yokes are parallel.

I started a post a while back trying to understand exactly why Norton did what they did, but it wasn’t really resolved.

Remember that rake is actually determined by the steering head angle, not the fork angle, so when you angle yokes like this you create a rather ‘different to the norm’ effect in terms of the relationship between rake and trail.
 
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I really don't want this to become that. I just wanted to determine if there really were differences in 750 yokes.....Done
If I want to go with aftermarket yokes, if they are all made to suit both 750's and 850's and are angled for 850 frames. Which certainly seems to be the case. The evidence supports that.
I know the differences in 750 and 850, I own both. So, if I go aftermarket yokes on my 750, I expect that things will be different, but I'm 52 years on from buying the 750, so everything's different now anyway :cool:

I've queried Kenny and Matt and may have to ask Don again. I'll post responses.
 
From Matt. Thorough as usual:

My triple trees are parallel to the steering neck. So they do not have the negative rake like the stock trees had. Both 750 and 850 trees have a rake.



Yes, it will change both rake and trail when installed.



When the first version of these trees were developed 20 years ago, they were tested in different configurations by AHRMA racers. In other words, both raked and parallel trees were made as demos. The feedback we got was that the parallel trees were better all around and that's why we went in this direction.



That said, different riders will have different feedback so you really cant say that everyone will like it one way or the other.



Matt
 
Deckard said:
If I want to go with aftermarket yokes, if they are all made to suit both 750's and 850's and are angled for 850 frames. Which certainly seems to be the case. The evidence supports that.
Click to expand...
Am I reading correctly? You have evidence that supports that aftermarket yokes are angled?

Please share any sources you have that produce aftermarket angled yokes.
 
Another possible aftermarket source?

www.rgmnorton.co.uk

7 3/8" ALLOY YOKES COMPLETE WITH FASTENINGS FOR COMMANDO 2 13/16" OFFSET (PR)

COMMANDO ALLOY YOKES 050705
www.rgmnorton.co.uk

These use the early 750 style of steering tube with the adjustment sleeve nut through the top yoke.
Pretty sure these are parallel too.

I found standard 850s to be more stable, and less inclined to suffer from the 'Commando Weave', but as I found with my 750, tyre choice also makes quite a difference - possibly a reason for adopting a 4.10 front tyre?
 
When you steepen the rake (that’s the headstock angle) you bring in the fork angle as well, and you therefore close the gap between the imaginary point on the floor taken through the headstock to the imaginary line on the floor taken vertically through the wheel spindle ie you reduce the trail.

But when you change the angle of the forks, via offset yokes, you leave the imaginary headstock point where it is, and move the wheel spindle line backwards, thereby increasing the gap ie increasing the trail.

So even though what you are doing looks almost the same, it’s having the opposite effect.

And it’s creating a different rake / trail relationship that would otherwise be possible.

So, when Norton extended the rake AND offset the yoke, WTF were they doing… and why?

Some believe that the offset yokes were a botch, a cheap way of the factory overcoming rake issues etc.

I believe the opposite, I tend to think that the seemingly contradictory combination of the extended rake and offset yoke was a deliberate move, undertaken with deliberate effects in mind, by people who knew what they were doing.
 
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