Help with strange triple trees issue

[Jim]

OK, I've been accused of being a little thick before (and rightly so) so you'll have to excuse me for being a little confused here.... In your first post, you put up two pics... one with the new triple tree that don't fit, and one with the old triple tree that (apparently) does fit. Same bike in both pics. Hell, even has the same red stool in both pics. Your 80SG triple tree looks exactly like my 80SG triple tree. So here's what I don't get.... If that tree fits, ain't nuttin' bent. 'Cause if it was, the original tree wouldn't fit. So, if we take a leap of faith here and say the original one worked, why can't you take the measurements from that? You can measure tube diameter and know if it's 34 or 35mm. You can measure center to center on all three holes and get the dimensions you need. You could even send the old triple tree back with the new and tell 'em "it needs to be this size."
So, bein' thick and all, help me out here... what am I missing?

 

[bikefreak69]

I am mildly retarded sometimes myself,but mainly I am with Jim D on this problem.Why not just use your old clamp since u are only doing the top and not a complete set?

 

[gggGary]

Dunno... I get what he's say'n. He bought a clean looking upgrade top clamp and it doesn't fit. Cognito moto is working with him to try and figure out why it's not right. He is is suggesting they kinda realize their dimensions are wrong and are trying to arrive at WHY they are wrong. ie they used a dimension from an early clamp. I should be able to check an early clamp and report back. I might even be able to find a use for a top clamp with the wrong dimension.........

PS I like what I think is cognito's business model; they design custom parts for many models of bikes that builders want that they can cut on a high end CNC mill and sell at a reasonable price. Their parts catalog is getting to be impressive. This is a process that was not possible at their selling prices even a few years ago. Trying to build up a list of 100's of machining programs for parts for many bikes is going to be a real big project. Errors will creep in now and then.
That they are working with him to get to the root of this discrepancy speaks well for the way they do business. They aren't 100% certain if the problem is their's or maybe it's non stock parts on the OP's bike, we can help get that ironed out?
I have set of their finned exhaust clamps and they are very well made.

 

[Sci85]

gggGary is spot on. I will say the folks over at CM have been very helpful. I love the look of the clamp they designed, the clean look with the hidden hardware, and it fits in with my project perfectly. It really is a beautiful piece. I'm just trying to determine if it was something simple like using an early model for both clamps. Regardless, I'm confident they will correct it and make me a new one. Thanks all.

 

[gggGary]

(note: post edited to correct a math error)
Did some measuring. I upped my game a bit on the measuring set up. that's a machinist's gauge block, pretty straight and accurate.

Still need to confirm some dimensions but these are pretty close. Yeah I'm not pulling apart assembled bikes to check them......
to the nearest .01mm with an inexpensive digital caliper.
1972
offset 59.85mm
fork tube CL to CL 174.91

1973
offset; not checked
fork tube CL to CL 184.95

all 74-83 pretty sure the CL's and offset stays the same on all 74 and up, even through the tube diameter change from 34mm to 35mm in 77
offset 46.72mm
fork tube CL to CL 185.01
The XS750 with 36mm fork tubes. matches these later dimensions as well

We're off tramping to find an abandoned cemetery in the nearby woods.

 

[Jim]

That they are working with him to get to the root of this discrepancy speaks well for the way they do business. They aren't 100% certain if the problem is their's or maybe it's non stock parts on the OP's bike, we can help get that ironed out?

That Cognito is working with Sci85 does speak well for them. And vise versa, Sci85 should be commended for being patient and willing to help Cognito.

I really do get that. All I'm trying to say here is, lets get the part that actually fits his bike dimensioned and get that info back to Cognito so's they can get busy cuttin' the right part. Sending the correct tree would be by far the best bet to ensure it's cut right. Once Sci85 has the correct dimensions, either by his own measurement or Cognito's, he can throw that up here and we can get busy sortin' out what Cognito needs to do in the future. Meantime Sci85 can be further along with his bike. Just seems to me like we're puttin' the cart before the horse here, that's all.

 

[TwoManyXS1Bs]

...Still need to confirm some dimensions but these are pretty close......

Okay, comparing to my XS1B's measurements.

...to the nearest .01mm with an inexpensive digital caliper.
1972
offset 59.85mm
fork tube CL to CL 191.9

According to the parts manuals, the forktube-cap-retained top crown (top triple) is interchangeable in the 70-72 XS1-XS2 models. This would imply that the fork dims, centers, and offset are identical.

Your pic shows the outer measurement of the XS2 fork tubes at 208.74mm.
Subtract tube diameter, 34mm, to get centers of 174.74.

My XS1B measurements came out with integer millimeters.

71 XS1B
offset 60mm
fork tube CL to CL 174mm

...
1973
offset; not checked
fork tube CL to CL 201.9

The first year of the pinch-clamp top crown.
Your pic shows the outer measurement of the 73 TX650 fork tubes at 218.46mm.
Subtract tube diameter, 34mm, to get centers of 184.46.
Sounds like the TX centers would likely be 184mm, which is 10mm wider than the 70-72 models.

...all 74-83 pretty sure the CL's and offset stays the same on all 74 and up, even through the tube diameter change from 34mm to 35mm in 77
offset 46.72mm
fork tube CL to CL 202.5...

Might want to double check the math...

 

[gggGary]

Thanks for the catch! I'll stand by the offset, but had subtracted 1/2 diameter, instead of full diameter for tube to tube. Spreadsheet and post above corrected.
Would be interesting to have you measure some tube diameters, I consistently find them a bit undersize. 34mm measure 33.9 35mm measure 34.93 I agree that whole mm numbers for the centers make sense but i was reporting what I found. I grabbed about 8 75 up top triples including 1 XS750 and found all had the same centers.

 

[Sci85]

All this is awesome! So, if I read the measurements correctly, so far we have the following approx measurments:

70-72, 34mm forks, uses a 174mm fork to fork on center measurement, offset is 60mm
73 - 34mm forks, 184mm fork to fork on center measurement, offset TBD
74 - 76 34mm forks, and 77+ 35mm forks, 184mm fork to fork on center measurement, 47mm offset

Does the above look good so far? Will need to get an offset for the 73 model.

I'll need to source an extra 35mm top triple to send to Cognito as mine is currently in use now but I think this will help us and them.

Thanks again guys.

 

[gggGary]

I'm doing a bit more measuring, (ready, fire, aim) I can mail a late model top triple directly to them.

 

[Sci85]

Cool gggGary. I'll give them another call today to arrange that and get back to you. Thanks so much for the help!

 

[halfmile]

Are you lowering this bike by moving the tubes up in the trees? Have you taken the tubes completely out, fitted the upper tree then checked the fit of the tubes? I just can`t imagine the mfgr being off that far since they probably make 100`s of these. Good luck, I know it`s frustrating just dealing with unforeseen dilemmas like this.

 

[Sci85]

Are you lowering this bike by moving the tubes up in the trees? Have you taken the tubes completely out, fitted the upper tree then checked the fit of the tubes? I just can`t imagine the mfgr being off that far since they probably make 100`s of these. Good luck, I know it`s frustrating just dealing with unforeseen dilemmas like this.

No lowering the bike. I've fitted and refitted many times and different ways thinking I had something jacked up. My stock triples fit just fine. I've also measured as have others and the measurements do not line up. The Cognito stem offset is around 50mm. Stock is closer to 47mm. They are not far off. From my approximate measurements, they cut the stem offset +3mm which is just enough for the clamp to not sit down over the stem. Fork to fork measurement is good. I was able to force the clamp to sit down on the stem but it took a lot of persuasion on the forks to get it done. Too much to make me feel comfortable. That's ultimately what started all this. I don't think they make or sell that many of these actually. That's the feeling I got from talking with them. So, it could be that others just forced it to work and never gave it any thought. He admitted they may have gotten a bad customer clamp or made a mistake somewhere along the line. Or maybe the cad file was altered at some point incorrectly. Regardless, based on the measurements so far, their cut is definitely off for the 35mm models.

 

[gggGary]

All this is awesome! So, if I read the measurements correctly, so far we have the following approx measurments:

70-72, 34mm forks, uses a 174mm fork to fork on center measurement, offset is 60mm
73 - 34mm forks, 184mm fork to fork on center measurement, offset TBD
74 - 76 34mm forks, and 77+ 35mm forks, 184mm fork to fork on center measurement, 47mm offset

Does the above look good so far? Will need to get an offset for the 73 model.

I'll need to source an extra 35mm top triple to send to Cognito as mine is currently in use now but I think this will help us and them.

Thanks again guys.

I've done a bunch of measuring.
these are my late model dimensions.

CL TO CL fork tubes 184.88
offset fork tubes to stem 46.88

some of the measuring and the math (go for it 2M!)

couple shots show the caliper returns to to 0 +.01mm between measurements.



Round them off to 185mm and 47mm ?? for us old school guys rounding up .12mm = about .005"
I measured and sorted to use straight and true used original parts, tightened the clamps on the triples, set at each end of the fork tubes. Tubes were checked for straight by spinning on the lathe.

72 73 dimensions,

The measuring wasn't as rigorous on these early pieces, but I think it gives you the idea, my measuring of 70 and 71 bikes shows agreement with 2m's statement that 70-72 are the same size.
so;
10mm increase in tube cl - cl, in 73
the offset change from 60 to 47mm came with the 447 chassis in 74
then an increase in fork tube diameter from 34 to 35mm in 77

Compared the 12" digital calipers to some 1 2 3 blocks.

note caliper set to read "

So this is the short version of fitment.
rounding to nearest mm

fork tubes center to center
1970-1972 175mm
1973 on 185mm

offset fork tube center to steering stem center
1970 -1973 60mm
1974 on 47mm

fork tube diameter
1970 to 1976 34mm
1977 on 35mm

stem length grew about 1/2" in 74 also. not 100% on the year this changed.
Add to this the changes in instrument and ignition lock mounts, probably not your worry but the short version is there were a LOT of different top triples and at least 4 different lower triples used.

 

[Sci85]

Sweet. Thanks gggGary! I measure, not super precise, the billet clamp at 50mm offset so as surmised, they are off 3mm. Should be a simple fix. I'll pass along your measurements to them.

 

[TwoManyXS1Bs]

...Would be interesting to have you measure some tube diameters, I consistently find them a bit undersize...

... a bit more measuring, (ready, fire, aim)...

Ready, Fire, Aim! That must've been where my head was at back then. Not sure whut happened, maybe I measured my spare XS1B stem, and rounded for convenience, can't remember.

Since that time, I acquired a larger 300mm caliper, with longer jaws. And, this time I'll take better measurements of the forks, as installed, on my 2 xs1bs.

XS1B-1 is my earlier '71, extended/chromed fork tubes.
XS1B-2 is my later '71, stock front end, forks were cleaned/polished to remove some rust stains.

Bike-- Inner- Outer- Ltube Rtube Centers
XS1B-1 140.98 208.89 33.93 33.88 174.94
XS1B-2 140.55 208.44 33.87 33.89 174.50

What a mess, huh? I guess that the guys who couldn't cut it in the engine department were transferred to "Steering components manufacturing".

Anyhoo, grinding those numbers puts the nominal fork tube centers closer to 175mm, in agreement with your measurements. So, here's a rev 2 bottom bracket pic...

And, a note on using the ID jaws of calipers. Take a known good micrometer, and dial in an opening. I'm using 0.700" here since it converts to a better metric value (17.78mm) without dangling microns. Measure the micrometer's opening, see if it's off.

One of my other caliper's ID jaws are off about 0.003" (0.07mm)...

 

[TwoManyXS1Bs]

Ready for more?


Looking at gggGary's XS2, and my XS1Bs centers:
174.93mm, 174.94mm, 174.50mm

Looking at gggGary's 73-on centers:
184.88mm, 184.35mm

(Hoo-boy, our metric friends gonna love this)

Maybe it would be better to call these fork centers:
70-72 ==> 6-7/8" (174.63mm)
73-on ==> 7-1/4" (184.15mm)

I'll just hide behind this guy for awhile...

 

[gggGary]

Looks good Bill,

get em bored out, the assembly line is waiting!
There's some interesting stories about Japanese manufacturing, and job lot shops back in the day.
Seen some pics of guys turning out parts in open air shops located under bridges and such.
A history of Honda is great reading, then W. Edwards Deming and Japan. https://en.wikipedia.org/wiki/W._Edwards_Deming