Stack height of stems?

[dvs cycles]

Using an already cut carbon steerer Columbus Muscle Fork on my 1987 Pinarello Montello I'm sort of restoring/ updating.
In need the lowest height stem clamp possible to make this work properly.
The Ritchey I would use is 39mm and would leave a gap of 4-5 mm from the top of stem.
FSA has one that is 35mm. How about some other heights so I can choose.
DEDA etc. Can't seem to find any specs for this on most mfg. websites or catalogues so I'm asking anyone here who will take a tape measure to theirs.
Thanks for any info, Don. :beer:

[93legendti]

http://forums.thepaceline.net/showthread.php?t=32533

http://forums.thepaceline.net/showthread.php?t=29174

[Grant McLean]

....oh ya, by the way, you're going to he!! for putting a carbon fork on a classic Pinarello...

There is no such thing as 'updating', it's called ruining...

just sayin' :) :) :)

-g

[dvs cycles]

....oh ya, by the way, you're going to he!! for putting a carbon fork on a classic Pinarello...

There is no such thing as 'updating', it's called ruining...

just sayin' :) :) :)

-g
If we all liked the same thing it would be a very boring vanilla or chocolate world now wouldn't it. :)
I bought this new in 1987 rode it all the time until I got my second Serotta in 1995, and then sold the frame to a friend in need.
If I was going to hang it on the wall and look at it I would restore it as it was right down to the Spumoni paint scheme, but i want to ride it again.
So lighter components, 10 speed, and more modern paint.
What Pinarello would be doing today if steel was the only frame material around. :beer:

[Dave]

Even if you have no spacers under the stem, the total problem is one of finding both the necessary stem clamp height and stem angle to produce the handlebar height that you want. You need to post more info for a complete solution.

I had a similar problem and figured out a not-too-difficult method of increasing the length of a carbon steering tube by 10mm.

[dvs cycles]

Even if you have no spacers under the stem, the total problem is one of finding both the necessary stem clamp height and stem angle to produce the handlebar height that you want. You need to post more info for a complete solution.

I had a similar problem and figured out a not-too-difficult method of increasing the length of a carbon steering tube by 10mm.
I'm not looking for a total solution here just some numbers so I can then look at different stems and choose myself what fits into my parameters of fit.
Very few stems in catalogues or websites list this dimension. :beer:

[93legendti]

Even if you have no spacers under the stem, the total problem is one of finding both the necessary stem clamp height and stem angle to produce the handlebar height that you want. You need to post more info for a complete solution.

I had a similar problem and figured out a not-too-difficult method of increasing the length of a carbon steering tube by 10mm.

What's the method?

[Dave]

What's the method?


Material needed:

1. one package (two tubes) JB weld
2. 1" star nut
3. 6mm bolt long enough to thread deep into the star nut and extend above the top of the extended steerer
4. foam rubber, 1" ID
5. plastic drinking straw or vinyl tubing with ID 6mm or larger
6. 1" copper tube solder coupler with no stop in the middle

A 1” star nut will slip into a 1-1/8” steerer, if the sharp corners are filed down. Do this as uniformly as possible and be sure to reduce the diameter just enough to allow the star nut to slip into the steerer. If the star nut has guide tabs that hang down below the bottom, these should be cut off with a dremel abrasive cutoff tool. Degrease the star nut with acetone or lacquer thinner.

Degrease the inside and top of the steerer with acetone or lacquer thinner.

Sand the inner surface and top of the steerer with 80-120 grit sandpaper to promote adhesion of the epoxy.

Cut a length of plastic tubing long enough to cover most of the threads on the 6mm bolt. Leave enough threads exposed to thread all the way to the bottom the star nut. Apply a small amount of grease to the bottom of the bolt, after it’s screwed into the star nut to prevent adhesion with the epoxy. Leave NO exposed threads at the top of the start nut.

Something light in weight must be used to plug the steerer and prevent the epoxy from running into it. I used a piece of 1” foam rubber. The copper coupling worked pretty well as a cutting tool to cut a cylindrical plug from the foam.

Insert the foam rubber plug just enough to position the top of the star nut a few millimeters below the top of the steerer.

Remove any burrs from the ID of the copper tube coupling and be sure that it will slide over the steerer. Lightly grease or apply automotive paste wax to the inside of the coupling, leaving almost no visible grease, to prevent bonding of the epoxy to the coupling. Slid the coupling over the steerer to the desired length of extension. A piece of masking tape around the bottom of the coupling might be a good idea to keep the coupling from sliding down. Also be sure that the steerer is approximately plumb, or the epoxy won’t be level along the top.

Combine the two tubes of JB Weld in a small container and mix thoroughly. Apply some epoxy to the inside of the steerer, and apply a large amount to the star nut, to fill the area between the two stars. Insert the star nut into the steering tube, making sure that the top of the nut is a few millimeters below the top of the steerer. Carefully place the remainder of the epoxy into the steering tube, filling it to the top of the coupling. It may be difficult to get all of the air out of the epoxy, so watch for air bubbles in the first 30 minutes or so after placing the epoxy. A toothpick will help to work out air bubbles.

Don’t disturb the copper tube coupling for at least 6 hours, or until the next day. Then the coupling can be removed and the top cap bolt unscrewed from the star nut. I used needle nose pliers to grab the plastic tube and remove it. You should then have a solid epoxy extension on top of the original steerer, with a permanently glued-in-place star nut.

There is some chance that your top cap might hit the solid epoxy, depending on the design of the underside of the cap. A little hand relieving with a small dremel tool sanding drum and/or large drill bit might be required to provide clearance.

[dvs cycles]

You DON'T use star nuts on carbon steerer tubes. Period.

[Dave]

You DON'T use star nuts on carbon steerer tubes. Period.

You're right, if the star nut were to be used in the normal manner, where the tips of the star dig into the steering tube. It would damage the steering tube and could result in failure.

I assume your statement refers to my procedure for extending a carbon steering tube? Apparently you don't understand how the star nut is being used. First, it's an undersized 1 inch starnut, not a 1-1/8 inch model. With minor filing it slips into the steering tube with NO contact pressure against the CF material. It's then totally encapsulated in solid epoxy. When the epoxy cures, you've got a solid epoxy plug that serves the same purpose as a common expanding plug, to support the steering tube and provides the M6 threads required for the top cap bolt.

If I had access to a lathe, I'd turn an aluminum plug to make a similar extension, then epoxy it in place.

[dvs cycles]

I wouldn't ride it! New fork is cheaper to me than broken bones or worse.

[Dave]

I wouldn't ride it! New fork is cheaper to me than broken bones or worse.

I wouldn't risk my life either. I'm a mechanical engineer (since 1981) and you're not.

My modified steering tube is a whole lot stronger than the original and no heavier than a fork with a metal compression plug. Keep in mind that 3/4 of the stem is still bearing against the original steering tube, which is now filled with solid epoxy that has a small center hole, barely over 6mm in diameter. I've been riding it for several years down dangerous mountain descents.

[Grant McLean]

You DON'T use star nuts on carbon steerer tubes. Period.

Is this true?

My colnago C40 fork came with a star nut...

-g

[ericson]

Usually but not always. My Cannondale slice fork (actually made by Time)came with star nut installed, and were design to work with a star nut according to the tech documents posted by Cannondale. I think compression plug instead of star nut for carbon steerer is a good rule of thumb, but as with most rules, there are exceptions.

[Blue Jays]

Shoot, a replacement Pinarello steel fork from that era would do the same thing while preserving the look, feel, and flavor of the bike.

[Dave]

Is this true?

My colnago C40 fork came with a star nut...

-g

Yes, it's true. If the fork has a carbon fiber steering tube, a star nut should not be used with it. Some colnago forks have metal steering tubes and a star nut is appropriate to use with those.

[dvs cycles]

I'm a mechanical engineer (since 1981) and you're not.

My modified steering tube is a whole lot stronger than the original and no heavier than a fork with a metal compression plug. Keep in mind that 3/4 of the stem is still bearing against the original steering tube, which is now filled with solid epoxy that has a small center hole, barely over 6mm in diameter. I've been riding it for several years down dangerous mountain descents.
You don't know what my qualifications are! The thread is for info on STEM STACK HEIGHTS. Why don't you post your own thread on unsafe modifications to carbon steerers. I think most people who are in the carbon composite industry would agree with ME. I've been building and racing bikes for over 20 years and I KNOW you don't take chances with carbon.
Do what you want with your own bike but don't suggest this crap to the average bike jock who doesn't have much experience with bike building.
GOOD BYE.

[dvs cycles]

Shoot, a replacement Pinarello steel fork from that era would do the same thing while preserving the look, feel, and flavor of the bike.
I still have the original chromed Columbus fork complete with matching serial # stamped on it. I plan on trying both just for comparison but like I said, I'm updating it just for fun not restoring it for a retro bike. I rode it new and it was good for it's time but todays components are the best. Lighter fork and components vs heavy steel fork and downtubeshifters? I'll take todays stuff.

[Dave]

You don't know what my qualifications are! The thread is for info on STEM STACK HEIGHTS. Why don't you post your own thread on unsafe modifications to carbon steerers. I think most people who are in the carbon composite industry would agree with ME. I've been building and racing bikes for over 20 years and I KNOW you don't take chances with carbon.
Do what you want with your own bike but don't suggest this crap to the average bike jock who doesn't have much experience with bike building.
GOOD BYE.

Geez, chill out. My response was directed to another poster who asked how the modification was done. Sorry for the thread hijack, but you're the one who started the nasty comments.

At least now we know you're an average bike jock with little bike building experience, after 20 years of riding. Since I'm an engineer with a lot of bike building experience over the last 23 riding seasons, I offered to help with the stem angle problem, but I see that you don't want the help.

[93legendti]

Material needed:

1. one package (two tubes) JB weld
2. 1" star nut
3. 6mm bolt long enough to thread deep into the star nut and extend above the top of the extended steerer
4. foam rubber, 1" ID
5. plastic drinking straw or vinyl tubing with ID 6mm or larger
6. 1" copper tube solder coupler with no stop in the middle

A 1” star nut will slip into a 1-1/8” steerer, if the sharp corners are filed down. Do this as uniformly as possible and be sure to reduce the diameter just enough to allow the star nut to slip into the steerer. If the star nut has guide tabs that hang down below the bottom, these should be cut off with a dremel abrasive cutoff tool. Degrease the star nut with acetone or lacquer thinner.

Degrease the inside and top of the steerer with acetone or lacquer thinner.

Sand the inner surface and top of the steerer with 80-120 grit sandpaper to promote adhesion of the epoxy.

Cut a length of plastic tubing long enough to cover most of the threads on the 6mm bolt. Leave enough threads exposed to thread all the way to the bottom the star nut. Apply a small amount of grease to the bottom of the bolt, after it’s screwed into the star nut to prevent adhesion with the epoxy. Leave NO exposed threads at the top of the start nut.

Something light in weight must be used to plug the steerer and prevent the epoxy from running into it. I used a piece of 1” foam rubber. The copper coupling worked pretty well as a cutting tool to cut a cylindrical plug from the foam.

Insert the foam rubber plug just enough to position the top of the star nut a few millimeters below the top of the steerer.

Remove any burrs from the ID of the copper tube coupling and be sure that it will slide over the steerer. Lightly grease or apply automotive paste wax to the inside of the coupling, leaving almost no visible grease, to prevent bonding of the epoxy to the coupling. Slid the coupling over the steerer to the desired length of extension. A piece of masking tape around the bottom of the coupling might be a good idea to keep the coupling from sliding down. Also be sure that the steerer is approximately plumb, or the epoxy won’t be level along the top.

Combine the two tubes of JB Weld in a small container and mix thoroughly. Apply some epoxy to the inside of the steerer, and apply a large amount to the star nut, to fill the area between the two stars. Insert the star nut into the steering tube, making sure that the top of the nut is a few millimeters below the top of the steerer. Carefully place the remainder of the epoxy into the steering tube, filling it to the top of the coupling. It may be difficult to get all of the air out of the epoxy, so watch for air bubbles in the first 30 minutes or so after placing the epoxy. A toothpick will help to work out air bubbles.

Don’t disturb the copper tube coupling for at least 6 hours, or until the next day. Then the coupling can be removed and the top cap bolt unscrewed from the star nut. I used needle nose pliers to grab the plastic tube and remove it. You should then have a solid epoxy extension on top of the original steerer, with a permanently glued-in-place star nut.

There is some chance that your top cap might hit the solid epoxy, depending on the design of the underside of the cap. A little hand relieving with a small dremel tool sanding drum and/or large drill bit might be required to provide clearance.
Thanks!

[Grant McLean]

If the fork has a carbon fiber steering tube, a star nut should not be used with it.

I think a better generalization is to use the system that it says to use in the fork instructions.
-g

[dvs cycles]

Geez, chill out. My response was directed to another poster who asked how the modification was done. Sorry for the thread hijack, but you're the one who started the nasty comments.

At least now we know you're an average bike jock with little bike building experience, after 20 years of riding. Since I'm an engineer with a lot of bike building experience over the last 23 riding seasons, I offered to help with the stem angle problem, but I see that you don't want the help.
It was you who threw out the first of the condescending comments.
If you want to take this any further please take it to PM so this thread can stay on topic. :fight:

[dvs cycles]

I think a better generalization is to use the system that it says to use in the fork instructions.
-gI totally agree and I think that you will not find any carbon forks that the installation instructions tell you to use a star nut.
Alpha Q had one that involved bonding in some metal sleeve I think but have never dealt with that one myself. In that case there may have been one used but not on carbon directly.