My first time..

Eurocycleguy

Eurocycleguy

Hero member
Location
Chicagoland-USA
'74 Lav GT
Pranged the Ceriani front end
Fork tubes bent-bad, going to replace them.
Question: How do I determine if the triple clamps are bent?
After I get the new fork tubes-start measuring???
Can the stem and lower clamp be measured without new tubes to determine its condition.
Please be gentle it is my first time (replacing front end bits) (unsuccessful search for this topic, if this topic already exists please direct me thx)
thanks
Larry
 
Fit the new stanchions to the yokes and see if they are parallel.
Also it may be difficult to install the stanchions in the original yokes if they are bent.
 
Grant said:
Fit the new stanchions to the yokes and see if they are parallel.
Also it may be difficult to install the stanchions in the original yokes if they are bent.
Click to expand...

grant's method works perfectly - you just need to know which way to twist the yoke (after heating it up) to get the right result
 
Grant said:
Fit the new stanchions to the yokes and see if they are parallel.
Also it may be difficult to install the stanchions in the original yokes if they are bent.
Click to expand...
Yes I thought having the stanchions installed would provide me a much longer surface to view for divergence.
I had to drive out the stanchions from the lower yoke. I am trying to convince myself that was just because they had been in there for 39 years. :D
 
Laverdaton said:
Take them to an Engineering Company and have them set up on a surface plate they can use a DTI (Dial test indicator) to take corresponding dimensional measurements.

that's what I'd do.......
Click to expand...
OK what would I or they be measuring? What point to what point. The stem and the lock to lock limiter are still on the assembly; so I guess the yoke would have to be inverted with the stem pointed down off the side of the surface plate.
Then just see if the yoke sits squarely on the plate. ???
and or check the stanchion holes to insure they are perfectly perpendicular to the plate? ???
Is this close?
 
I am located about 30 miles from FrameCrafters in Union, Illinois. They specialize in building, modifying and replicating frames for racing, customs and one-offs. Maybe after I get new stanchions I should take the yoke and the specs over to them.
"Watching someone fish doesn't teach me how to fish." but then I don't have all the required kit anyway. :(
 
An engineering company could accurately check your stanchions (the chrome tubes) for complete straightness.
These will likely be bent. There may be resultant damage to the yokes. Again, they should be able to determine if these are distorted too.
If both are badly bent then I would recommend replacement.
It is possible to straighten stanchions but you never know what damage has been done really.
 
If you check them yourself, fit the straight stanchions to each clamp individually and get them right before you try it all together. I have Marzo clamps from a write-off Jota on my SF racer since I straightened them 30 years ago and they are still perfect however many here would probably have it that I ride a ticking bomb. It took 2 days to get them right. It is quite a tricky job with a press and stanchion stubs and due to risks of further damage or weakening (liability), as well as the time involved, you probably won?t get any business to do the job. If your stanchions are stuffed (likely as Cerianis are very strong and don?t take much before they can?t be straightened without kinking) you can at least cut some straight stubs that will fit in your press.
Henry, where did you get the heating bit from? I have always been instructed to do them cold. From my experience they are very flexible. To get it to stay put a millimeter from where it sits, you have to push it way further and it springs back. It makes you realise how much they must flex in use.
It is often only the lower that is bent in a minor bingle but you have to check them both. I fit a straight bar to the upper clamp steering stem to check it against the stanchions.
 
Grant said:
An engineering company could accurately check your stanchions (the chrome tubes) for complete straightness.
These will likely be bent. There may be resultant damage to the yokes. Again, they should be able to determine if these are distorted too.
If both are badly bent then I would recommend replacement.
It is possible to straighten stanchions but you never know what damage has been done really.
Click to expand...
Oh yes the stanchions are BENT, like a Chicago politician.
 
Tippie said:
If you check them yourself, fit the straight stanchions to each clamp individually and get them right before you try it all together. I have Marzo clamps from a write-off Jota on my SF racer since I straightened them 30 years ago and they are still perfect however many here would probably have it that I ride a ticking bomb. It took 2 days to get them right. It is quite a tricky job with a press and stanchion stubs and due to risks of further damage or weakening (liability), as well as the time involved, you probably won?t get any business to do the job. If your stanchions are stuffed (likely as Cerianis are very strong and don?t take much before they can?t be straightened without kinking) you can at least cut some straight stubs that will fit in your press.
Henry, where did you get the heating bit from? I have always been instructed to do them cold. From my experience they are very flexible. To get it to stay put a millimeter from where it sits, you have to push it way further and it springs back. It makes you realise how much they must flex in use.
It is often only the lower that is bent in a minor bingle but you have to check them both. I fit a straight bar to the upper clamp steering stem to check it against the stanchions.
Click to expand...
I am not yet forming a mental image of how to set up this operation. I can see how using cut sections of straight stanchions would be useful to leverage the yoke ears.
Heat would also assist the realignment process; maybe too easily. Would have to be careful as I would during the entire process.
I will think and study more on this obviously.
Wolfgang emailed me and said the yokes are getting scarce.
I do have a Marzo front end on a rolling frame, but I want to keep the GT as original as possible. And I hope to build the rolling frame someday.
thanks Tippie,
Grant
and Henry
 
I may have a full trunk load of those yokes of undetermined origin (old french dealer).
Would need to check.
Might come in handy to you.
Paul
 
Tippie said:
If you check them yourself, fit the straight stanchions to each clamp individually and get them right before you try it all together. I have Marzo clamps from a write-off Jota on my SF racer since I straightened them 30 years ago and they are still perfect however many here would probably have it that I ride a ticking bomb. It took 2 days to get them right. It is quite a tricky job with a press and stanchion stubs and due to risks of further damage or weakening (liability), as well as the time involved, you probably won?t get any business to do the job. If your stanchions are stuffed (likely as Cerianis are very strong and don?t take much before they can?t be straightened without kinking) you can at least cut some straight stubs that will fit in your press.
Henry, where did you get the heating bit from? I have always been instructed to do them cold. From my experience they are very flexible. To get it to stay put a millimeter from where it sits, you have to push it way further and it springs back. It makes you realise how much they must flex in use.
It is often only the lower that is bent in a minor bingle but you have to check them both. I fit a straight bar to the upper clamp steering stem to check it against the stanchions.
Click to expand...

from the same oke who straightened the stanchions and i used the straightened stanchions to bend the bottom yoke straight. it was a guzzi 1000. the same stanchions got straightened again by the same oke about 4 years later. on neither occasion were they very bent. he's an aircraft engineer. i just did what he said - it worked. what more do you want!
 
No worries, Henry. What more could you ask for. My engineers advised to avoid heating the alloy and that worked too. They said it?d work one time only with heat. I am not an engineer, but just like learning.
Larry, there are lots of front end bits on ebay at the moment.
 
Tippie said:
No worries, Henry. What more could you ask for. My engineers advised to avoid heating the alloy and that worked too. They said it?d work one time only with heat. I am not an engineer, but just like learning.
Larry, there are lots of front end bits on ebay at the moment.
Click to expand...

to be honest, i'm not really sure how hot i made it. it wasn't very scientifically done. i just used a gas blow-torch on it untill i thought it was hot enough, bent it straight and left it all to cool down. the bike is still belting around joburg today. it belongs to my engineer friend's cousin. i doubt they've changed the yokes.
 
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