Took my new Kestrel RT800SL out on my favorite ride yesterday, a 15.2-mile loop with one short, but steep hill about 1/3 the way in. On the downhill side, when I hit 33 mph, (based on the Garmin 500), the front wheel started wobbling violently side-to-side.

I though right then and there that I was going down and started moving to the side of the road thinking it would be better to go sideways into the road cut embankment than go sliding along on the asphalt. Luckily, with judicious application of the rear brake, I was able to slow down and regain control. After that, I kept it under 25 mph for the duration of the loop, (mostly slightly downhill), and returned home safely without incident.

Nothing apparently "wrong" with the front wheel or headset adjustments. This is my second ride since getting the bike back from the shop where I had them check the bike out completely, adjusting everything and asking for the torque of all the bolts to be checked. It is, or was, a pretty decent pro shop. The first test ride the day I picked up the bike, just a short 5-mile ride, was fine. But, I really didn't reach speeds above 30 mph on that test ride.

What would cause this front wheel wobble when hitting speeds higher than about 30 mph? Or, is it just that I'm not used to riding a bike with aggressive geometry? My previous bike was a late 60's vintage Mondia until last year when I purchased a Trek Madone 4.5.

Thanks for any insight you can offer.