womble

I've just changed my stem. I'm wondering how tight should the RED bolt be? I initially assumed that it should be very tight so as to hold all the headset bits in place, but realised that there is probably only so much pressure I should be putting on the bearings in the headset.

(I'm assuming that it's really the BLUE stem bolts that should be as tight as reasonably possible, and the RED should be applying minimal pressure. Does this make sense?)

Heh, now that I look at the photo, that's one chunky looking stem that I just installed...

Al1943

The "red" top cap bolt is used only to set the load on the headset bearings. The load on the bearings is critical, must not be too tight or too loose. The pinch bolts are tightened last and they maintain the position of the stem. You could even remove the cap bolt after tightening the pinch bolts.

Al

womble

How do you tell how tight/loose to make the cap bolt?

Stacey

Tight enough to remove any wobble & wiggle in the headset bearings, loose enough to allow for free rotation of the bars & fork.

When in doub't consult your LBS.

PS ~ it never hurts to take your wrench a gift... Coffee, beer, some Entenmanns's

womble

Thanks for that.

Yep, this is what I'd prefer to do (and he's a great guy). Only problem being that he's an hour and a half away!

boyet

Just hand tight it or hand pressure. Use short allen keys for tightening, don't use long tools for this. B-coz it will damage or rounded the allen cap and long tools have more torque than the short one. Remember that the treaded aluminum parts are easily lose when overtighten.

Al1943

+1 Good info.

One way to test is to hold the front brake tight and rock the bike forwards and backwards to check for loose play between the fork steer tube and the headset. There shouldn't be any. But it's also easy to get too much load on the bearings. The rotation should be smooth and free, per Stacey above.

Bobby Lex

This web-site will walk you through the process, step-by-step:

https://www.parktool.com/repair/readhowto.asp?id=65

Bob

Steev

Is it me, or are there no spacers under that stem?
If no spacers, you better seek some qualified assistance.

truckin

It's hard to see, but I think there are spacers in there- you can see horizontal-ish lines curving around between the stem and the headset if you look closely.

well biked

Tighten the top cap bolt down enough that when you lock the front wheel and rock the bike as Al1943 says, no play is felt, and yet when you lift the bike by the seatpost with the wheels off the ground and turn the front wheel to one side, it returns to the center on its own when you let go of it. That's a properly adjusted headset-

Stacey

Agreed.

HillRider

I've seen torque specs for the top cap (red) bolt of 4 to 8 inch-pounds. That's just finger tight. You do want it tight enough to assure no play in the headset when the bike is rocked against a set front brake but you don't want to damage the bearings or cause binding.

The blue bolts are usually spec'ed at 6 to 8 N-m or about 50 - 70 inch pounds. That's pretty tight and will require some real force on a typical L-type allen key.

tellyho

Just to belabor the obvious:

Too tight on the top bolt = Handlebar and fork don't turn freely.

Too loose = fork wobbles in head tube. Put brakes on and push, you should get no movement.

This is a very tetchy adjustment, and if you get it wrong either way, it will severely shorten the life of your headset.

womble

Thanks everyone- that pretty much comprehensively answered my question. I confusing play in the fork with play in the headset, but have attributed that to the nature of the moderm suspension forks (there was never even a hint of movement with my old Headshok when locked out).

Yes, there are lots of spacers under the stem. It's a very new bike so I haven't had the steerer tube cut down much whilst I try figure out an optimal height. Part of being a new bike, the headset ran smoothly even with the bolt done up very tightly.