Headset wobble under braking HELP!!!

davey1991

I have what i think may be a serious problem, i have a specialized p1 jump bike and for a while now my headset and stem etc etc wobble under braking, i took front end apart and everything seems to be ok the spacers are all fine and the stem fits well, everything is as tight as should be, anyone have any ideas what the problem is i'm worried i may have permanantley fucked my bike anyhelp appriciated.

thanks Davey.

supersonic

Did you preload the bearings?

nicklouse

have you changed the fork?

davey1991

Nope no new forks and ive left everything alone i have a feelingi may have overtightened the top bolt, any more ideas? i'm hoping to get it looked at profesionally this weekend

supersonic

Sounds like you dont know how to work the top bolt - it preloads bearings: this can ONLY be done with the stem bolts undone. Preload, tighten stem bolts.

Park Tools shows you how!

davey1991

no i have stem completely loose, tighten the bolt yet nothign seems to happen, i do know how touse the top bolt, im not that much of a retard, but is there a problem of overtightening the bolt?

supersonic

Basically you keep turning the bolt until the play in the headset is eliminated, but the wheel turns freely. When this is done, align the stem and tighten.

But if the headset is not in the right order, or the stem top cap is not pushing on the stem (ie it is hitting the steerer, or there isnt enough spacers - the stem should be 3-5mm higher than the top of the steerer) then it wont adjust no matter how hard you tighten it.

Much more rarely, but much more serious is damaged headset cups or fork steerer

davey1991

may it have something todo with the star fangled nut? would overtightening cause this sort of damage or is this a really simple fix?

ian_worby

you can overtighten it and crush the bearings However the steering would be very tight.

Unless you need another spacer under the stem, which cause the symptoms you describe if the top caps tightening down to the steerer before it's fully preloaded, giving the impression of being tight/overtight

only other thing i can think of is a flared headtube, but thats unlikely but not impossible

davey1991

thing is steering is completely loose, i only get back and forth movement butit is quite drastic, how much space should i have between top of forks and stem, using spacers?

supersonic

Stem with spacers should be ideally 5mm higher.

davey1991

would having less than 5mm cause a wobble like this? if so i think you may have solved my problem.

davey1991

Thanks, when my new stem and spacers come i hope my problem will be solved, i'll re-post if problems persist. Very helpful guys thanks.

LordBanks

Might sound daft, but its worth looking over the rest of the front end, check you actual forks, the legs, the stancions (opps, spelling police), even you front disc. I once thought i had a loose headset, but it was my front rotor disc that was slightly loose which was causing the rattle.

davey1991

i've checked my whole front end to completely count everything out and it all came down to headset, i know the pain of a loose rotor, thanks for tip though.

davey1991

also this was not a rattle its a wobble, movement of about an inch backwards and forwards at the headset. but i belive i have solved the problem now.