Mattyb13

I am adjusting the bars and stem height on my new Diverge Comp Carbon. Im wondering if there is a suggested 'tightness' to the main stem bolt on top of the stem. I have a torque wrench set to 5nm for the side stem bolts the front stem bolts. Some have said 'finger and thumb' tight but that is fairly vague? Want to get the main stem bolt to the proper tension so I dont hurt the bearings. Thx.

Karman321

8nm

CliffordK

After you have the bearings adjusted and the stem tightened down, there is no reason to keep tension on the stem bolt.

fietsbob

Top bolt on threadless forks is your headset pre load.. I dont go by numbers there .
the stem bolts grip the steerer tube are on the side of the stem .. you have options..

'Race Tight' is just loose enough to move in a crash to break less stuff, but tight enough to move the front wheel ,
Any other time of normal service..
other wise the spec printed on stems is low enough to not strip out threads in the aluminum.

Mike F

What he said....and if the Diverge has future shock, its pretty much decorative anyway.

Mattyb13

Thanks all. Yeah its a 2017 Diverge Comp Carbon CEN version. No Future Shock. So many conflicting and differing ideas about how tight to have my stem bolts. So here is what I did. I loosened the horizontal stem bolts enough so that I could turn the bars with. I tightened the top stem bolt 'very snug'. After that I torqued down the horizontal stem bolts. Took it for a ride. Seems like its all snug and tight. Thanks for the help all!

Dean V

I do it up tight enough to remove play from the headset and no more. That is a lot less than 5nm.

merlinextraligh

qft.

The point here is that you are not securing the stem; you're setting the preload on the headset bearings. You want it tight enough so there is no play, but loose enough that there is no binding.

The test is turn the handlebars back and forth; if it moves freely, it's not to tight. Lock the front brake, and roll the bike forward, raising the rear wheel off the ground. If there's no play, you're not too loose.

Once the load on the headset is right, tighten the bolts on the stem until snug, not to exceed the torque spec

joejack951

With older loose ball headsets, this always worked fine for me. With modern cartridge bearing headsets, I've found that they require significantly more preload in order to both feel tight and, more importantly, stay tight. My method of setting bearing preload has changed from your process to one where I add preload until I can feel the bearings begin to bind then back off just enough to remove the binding. This has prevented any unwanted looseness in the headset from cropping up after a few hundred or thousand miles as had been occurring. YMMV.

RPK79

As with all things tighten until you hear a crack then back off 1/4 turn.

caloso

Agreed. Once I have the stem bolts tight, I'll back it off 1/8 a turn. It's done its job.

Racing Dan

Yeah, when you do that you preload the bearings. Thats fine, depending on how snug "snug" is. A tip is to loosen it, then grab the front brake and snug the cap bolt, while gently rocking the bike back and forth with the brake on. That seem to settle it all into place. The tighten the stem bolts.

Kimmo

My method of setting headset preload is to first ensure the steerer clamp bolts are snug enough to hold the stem firmly to the steerer while allowing the stem to turn on it (eliminating any potential wiggle from that point), and tighten the preload bolt until rocking is eliminated from the headset, with the front brake locked, weight on the seat, and a hand wrapped around the upper bearing interface to be sure.

Then pick up the bike and tilt it from side to side to ensure you can still ride it no hands.

JohnJ80

Seems the expander inside the steer tube should be tightened to about 8nm (check fork spec). Cap for preload of the headset bearings is 3-4nm (enough to get play out). Stem to steer tube bolts 5nm and same for bolts to the bars. Once stem bolts on steer tube are tight to 5nm, the steer tube cap is immaterial.

j.

Kimmo

That depends entirely on the design of the expander; some work much better than others, and how much the bolt torque translates to force against the inside of the steerer depends on both the angle of the cones and friction in the assembly. The correct torque is basically whatever it takes to stop the expander slipping, and I'd be surprised if you could damage a carbon steerer before stripping the threads in the expander, so that should give you a pretty big window in most cases.

If in doubt, some carbon paste inside the steerer should help.

Dan333SP

Too loose on the top screw and you get an obnoxious juddering feeling from the front of your bike when braking. Too tight and you'll end up with pitted bearings in the headset that have a ratchety feeling when you turn the bars, and can cause the bike to handle in unexpected and dangerous ways when cornering at speed. Just right, and all is well.

Kimmo

And depending on the type of headset, possible frame damage.