wobbly front wheel

on a recent downhill descent i noticed my front wheel starting to wobble a lot - to the point of almost wiping out - had a tough time hanging on.
this happened before on a borrowed bike, but this was a brand new bike.
any thoughts as to why?
i was going about 45 mph
any help is appreciated
thx

 

It's called speed wobble and it happens for a lot of reasons, most related to equipment maintenance or weight balance on the front end of your bike. From a riding standpoint you can try things like changing your grip on the bars or clamping the top tube with your knees to dampen the vibrations, but definitely don't slam the brakes hard, that typically makes it worse.

Try posting your question in the Cycling Equipment forums for information on the causes and cures in terms of bearing adjustments, etc.

Good luck,
-Dave

 

thanks dave
i'll try this next time
i didn't slam on the brakes, just feathered gently until i came to a stop
freaked me out a bit
always amazed me how the pros can fly down the hill at 60mph w/o the wobble
must be my technique
the bike is always well maintained
thanks again

 

Probably not, it happens even with great technique for a lot of reasons. I've had bikes that were rock solid to 45 and went wild at 50 mph and others that never develop speed wobbles up to the top speeds I've managed on them. Something as simple as tire pressure can eliminate or at least change the speed range at which your front end resonates to the point where it's not a problem. But more often than not it's a slightly tight or loose headset or wheel bearing, wheel out of true or something like that that makes a bike more or less prone to wobbles.

-Dave

 

Moved to Equipment.

 

speed wobble has all sorts of sources, case in point; light welded steel frame (853) heavy steel steerer (when did it become popular to call it a 'steer' tube? they're not made from livestock are they?) bonded to heavy carbon fork legs. 40kph speed wobble, using any wheelset/skewers/tires/pressures... moved the rear wheel up in the horizontal drops as far as possible/safe, wobble disappears... possibly an alignment issue but it tracks so well everywhere below that speed that I considered alignment not the issue. just one case but there are many factors... took me a couple of months to find this workaround, not sure if I would call it a solution...

good luck

 

been in this predicament a few times and it's normally descending from a long climb where the air is chilly at higher speeds. I clamp the top tube and loosen my grip to come out of it and has worked every time. it is however a frighting experience