Vibration at speed

I was cruising today and got it up to about 130 and found that the car vibrated at about 120. Once I got over 120 it seemed to settle down. When the vibration is speed specific, does that narrow down the probably causes?
Thanks,

Would it vibrate at the a slower speed but at the same rpm at if you were at 120. And I assume that is KPH?

I was trying to mess with you guys by not saying MPH or KPH. I guess you're more than a match for me!

It's not rpm related. Definitely speed related. I'm guessing a wheel is out of balance. I have found small speed specific vibrations are usually wheel balance, but thought it would be worth asking.

130 miles per hour, in a replica, would be VERY interesting. I hit about 110 mph on the freeway (once). Fast enough for me!
My guess would be wheel balance.
Ron

Probably tire/wheel balance or front wheel bearing adjustment (or both) but could even be a bad shock absorber.

I had a 91 300ZX once and it did the same thing. At about 85mph, it would shake/vibrate. I found out later that one of the steel belts in the tire tread had broken. Some smaller cars have nylon belted tiers and can break if the tire is curbed to hard or it could be due to a poor MFG process. When a belt brakes it is no longer a true circle and when spun at high speed the tire almost wants to get rid of that broken belt if you will. Moreover, the bounce will start at a determined speed and then it will stop when the bounce goes 90* out of phase from when it started. I do not work in a tire shop, nor do I consider myself an expert in any way. I got this explanation when I took my car in for repairs. True or not I got new tires and the bounce went out with the old ones.
DS.

130 In a car that is made for that speed gets a little shaky....A speedster is barely on the ground at that speed.

Ron: Did you find the cause of those not so good vibrations?

There isn't really much of a vibration. I was actually just bored and was fishing for responses to the 130 comment. I was hoping you all would think I meant 130mph and harass me for my foolishness, but Mike was too quick to pick it up. I guess that's because 130mph in a Speedster would not be possible?

Ahhhh crap sorry RON........

Your Speedster doesn't do 130 MPH?

Not yet, but it might soon with the new engine...see new thread in Technical/engines for details....