jonelliotelliot

hi there.
just switched forks.
and now, whenever i use the front brake, i get a pretty bad vibration through the steerer/headtube.

it's 1" threaded straight blade fork. (recessed brake)

• headset is nice and tight, and moves smoothly left and right with minimal resistance.
• wheel seems to be true

what are the things i should be looking for, to eliminate this?


thx.

TimothyH

What kind of brakes and what kind of bike/fork?

In general...

1. Retighten headset just to make sure. Straddle the front wheel, hold the front brake and rock the bike back and forth. If there is any noticeable clunking then the headset is not tight enough. Loosen the bolt until it clunks and then tighten 1/8 turn at a time until the clunking goes away.
2. Clean the rim braking surface and lightly sand the pads.
3. Make sure the brake caliper is tight to the fork and that the bolts holding the pads to the caliper are tight enough.
4. Adjust the pads so that they "toe in" at the front.
5. Make sure the crown race is fully seated onto the fork crown.

That is what I would do.





-Tim-

Leisesturm

What Tim said. And...


Technically both statements cannot be absolutely true at the same time. A 'nice, tight' headset does not move all that smoothly. Of necessity, the ultimate in tightness is sacrificed so that there can be freer action of the bearings or vice versa. It is a compromise. You may have to adjust for just a little bit more 'left/right resistance' than you have at present, to eliminate the vibration.

79pmooney

And - what kind of fork - materials, age, history? This is the worst place on a bike to have a failure, by far! (Trust me, I know. I had a sudden total failure at the bottom of the steerer. I also had a quality steel fork start to shudder while I was riding. Did the final 5 miles on rear brake only, threw the bike on the stand, pulled the wheel and peeled the right fork blade out a foot with no exertion at all! Fork blade was cracked 3/4s around.)

The first fork was aluminum and became famous for sudden catastrophic failures. The second was custom steel where the builder, the plater and myself made decisions that almost ended very badly. I selected a sexy, very light investment cast fork crown with no scalloping. The builder landed some light Columbus SL fork blades. The plater never mentioned that high strength steel MUST be heat treated after nickle plating to drive out the embedded hydrogen molecules (basically gravel in the mortar of a brick house).

jonelliotelliot, this fork may be giving you warning to save your life. Take my advice: honor it. Don't ride it until you know what the cause is. The first failure I mentioned very nearly killed me. It did put me in a coma for a week, made me famous in the Boston cycling community and sold Bell a few hundred helmets. (I lived because I was wearing one.) Put a shadow on 7 years of my life and, cost me my profession and more.

Yes do the things the poster above suggests. But keep my words in mind!

Ben

TimothyH

@79pmooney makes a good point and worth considering.

To my list I would add a check for damaged, cracked fork. I'd probably look the fork over initially, more thoroughly when the wheel is off and very thoroughly when looking at the crown race.


-Tim-

cbrstar

When you changed forks did you remember to change the headset crown race?

jonelliotelliot

thanks for all the replies.
the fork is a colnago precisa straight blade 1" threaded.
brake is a campagnolo chorus
headset is a dura-ace 7410

there is no clunking when i rock the bike back and forth, with brake engaged.

the brake-pads are brand new ... so i'll try sanding them down a bit.
i'll also try toeing them in.
also... i'm not using the original recessed bolt that came with the calliper, since i lost it. --- i know the new one is a little shorter. maybe it needs to grab more threads?

and yes. the crown-race from the original fork has been transferred over.

jonelliotelliot

This is what was causing the vibration. Toed in my pads. Everything is smooth now.