Road Bike, Cycling Forums banner
1 - 20 of 26 Posts

·
Registered
Joined
·
349 Posts
Discussion Starter · #1 ·
This vertical line, which isn't visible unless you point a flashlight at it and can't be felt with a fingernail, bothers me a bit. Is it possible it might be cracked / weakened? Or is it some kind of weld join?

 

·
Registered
Joined
·
233 Posts
Maybe remove the top cap, and have look to see if the carbon fiber is cracked from that angle?

Edit: sorry, you did mention the steerer tube is aluminum. Definitely need caffeine. Still, worth a look?
 

·
Registered
Joined
·
11,474 Posts
It's amazing to me you didn't remove the spacers and the stem before taking that picture. I hope you weren't planning to ride that fork after someone on the internet typed "not to worry, just a scratch."

Whatever it is, I'd not ride that fork. Aluminum can progress from an imperfection to complete failure in a matter of weeks and sometimes just days. And steerer failure can be deadly, believe me.
 

·
Registered
Joined
·
349 Posts
Discussion Starter · #4 · (Edited)
I was in a hurry before leaving for work, just wanted some quick first impressions. This bike isn't hitting the road before May, so I will definitely take a better look at the whole steerer.
 

·
Registered
Joined
·
11,474 Posts
This bike isn't hitting the road before May, so I will definitely take a better look at the whole steerer.
OK, makes sense. It's worrisome that you can't feel that line. Were it a scratch, you'd feel it because material is gouged out in a scratch. A crack can have both surfaces on either side of it completely flush with one another.

What's odd is the location and direction of the mark. The highest stress on steerers by far is the area just below the lowest spacer, and steerer cracks generally run circumferential. When you pull the stem, check (by feel) if there's a slight burr on the lower inside edge of the steerer clamp that matches the location of the mark. If there is, it could be an installation scratch so slight you can't feel it. Could be--I'm not saying it is!
 

·
Registered
Joined
·
942 Posts
Also looks like the top bolt has been torqued to a much higher value than the bottom bolt. Usually when torqued properly, the upper and lower gap that shows the bolt threads are equally wide.
 

·
Registered
Joined
·
349 Posts
Discussion Starter · #8 ·
Also looks like the top bolt has been torqued to a much higher value than the bottom bolt. Usually when torqued properly, the upper and lower gap that shows the bolt threads are equally wide.
Both torqued to 5Nm by me (only thing that I did as my LBS didn't perfectly align my stem after last maintenance) . Maybe the expander plug was overtorqued and bulged the steerer at the location of the bottom bolt, explaining the difference?

As for the grease, there is some but imo not enough.

I'll take it to the shop tonight, doesn't look good the more I think about it.
 

·
'brifter' is f'ing stupid
Joined
·
15,563 Posts
Both torqued to 5Nm by me (only thing that I did as my LBS didn't perfectly align my stem after last maintenance) . Maybe the expander plug was overtorqued and bulged the steerer at the location of the bottom bolt, explaining the difference?

As for the grease, there is some but imo not enough.

I'll take it to the shop tonight, doesn't look good the more I think about it.
You still think that steerer is aluminum?
 

·
Registered
Joined
·
349 Posts
Discussion Starter · #10 ·
You still think that steerer is aluminum?
I'm not so sure anymore! I thought it was because Cannondale advertises the Synapse as having carbon fork and the Synapse Hi-mod has having a FULL carbon fork... That being said it looks an awful lot like some carbon matrix under a bright light!

Anyways turns out it was a false alarm. Every Synapse in the shop had the exact same line on the steerer. So it's some kind of joint or a line between two carbon sheets.

A valid point was raised tho about the top and bottom bolt not looking like they have been torqued the same. The bottom bolt is at the location of the expander, while the top one has a part of the stem clamping on nothing (Cannondale, in their manual, states that 2-3 mm of void should be left between the top of the steerer and the top cap). So I guess that explains in part how much every screw is screwed. Just to make sure I would not deform the tube, I torked the bottom bolt to 5Nm and the top one to 4.5Nm. It doesn't sit perfectly straight but it's better and the tension difference must be negligible enough not to have any ill effect.
 

·
Registered
Joined
·
4,493 Posts
Here's how to test whether that's a legitimate crack.

Remove the fork an mount it in a bike stand, vise, whatever, so the steerer is horizontal.

The suspect crack should be facing the floor. Place a piece of invisible scotch tape over the crack.

Now flow a little colored fluid like Liquid Wrench so it puddles in the trough of the steerer on top of the suspected crack. Try to prevent it from flowing over the end of the steerer.

Let the setup sit for an hour. Without removing the assembly, take a peak to see if the scotch tape has captured some of the fluid if it flowed through the crack.

This method worked for me; it proved my headtube was cracked.
 

Attachments

·
Registered
Joined
·
5,374 Posts
With that difference in gap, I would put a spacer under the top cap to get that top bolt away from the top of the fork. I cannot believe that the top of the carbon tube is deflecting that much to reduce the dia of the steer tube without a failure.
 

·
Registered
Joined
·
349 Posts
Discussion Starter · #13 ·
With that difference in gap, I would put a spacer under the top cap to get that top bolt away from the top of the fork. I cannot believe that the top of the carbon tube is deflecting that much to reduce the dia of the steer tube without a failure.
Maybe it's not the tube itself that's deflecting, might just be something with the steerer itself. The idea of putting a spacer on top of it sounds fine but Cannondale explicitly advises against it as it's supposed to prevent proper functioning of the expander and top cap
 

·
Registered
Joined
·
11,474 Posts
I must be missing something--when did this steerer change from alloy to carbon? Old man here, it's easy for me to misread stuff now.
 

·
Registered
Joined
·
349 Posts
Discussion Starter · #15 ·
I must be missing something--when did this steerer change from alloy to carbon? Old man here, it's easy for me to misread stuff now.
Honestly I just don't know what material it really is. Always tough it was alu but by the look of it it might be carbon.
 

·
Registered
Joined
·
349 Posts
Discussion Starter · #18 ·
Anything wrong with having a small imprint of the edges of the stem on the steerer? (see horizontal line slightly below middle of steerer - it follows exactly the clamp pattern of the stem)


Can't be much worse than what carbon paste does on a seatpost, right?
 

·
Registered
Joined
·
349 Posts
Discussion Starter · #20 ·
Also looks like the top bolt has been torqued to a much higher value than the bottom bolt. Usually when torqued properly, the upper and lower gap that shows the bolt threads are equally wide.
Well, tried to flip my stem today to see if it was caused by the stem itself. Even with the stem flipped, the spacing is still wider at the bottom. I'm puzzled... Might be caused by the expansion plug?
Inspected the steerer, it's super straight, no bulging or anything wrong.
 
1 - 20 of 26 Posts
Top