Long story short, I have a vibration in my car, feels like the front. It's speed sensitive, but not throttle sensitive, and happens from 50 mph on up, and can be felt in the steering. One of these days, hopefully sooner than later, I'm going to get under there and inspect my bushings and connections. I also want to determine if it's possibly a bent axle, but I don't know how I'd look for such a thing. Any hints?

 

A bent axle would make the car wander as well as next to undrivable. I would lean toward a bent/out of balance wheel.

 

FWIW, the odds of a bent axle are slim. More likely it's an out of balance wheel.

 

A bent axle is likely to be felt at all speeds, too.

 

I don't want to sound like I am piling on, but it sounds like either an alignment issue, wheel & tire balance issue, or both alignment plus wheel & tire balance. Did you run through a pothole (or other road debris) recently?

 

A bent axle (or hub) will also cause a pulsation in the brake pedal when applying brakes.

 

Get your tires balanced.

 

If it feels like the front, then move the front tires to the back. Then if it feels like the back, then it's the tires. If it still feels like the front, then you may have other issues.
I would do the swap first, then balance all the wheels next, then start to think about other bits being out of wack. My money is on a misbalanced rim.

 

I have already swapped the wheels back to front. The car has been balanced, the last time I had tires put on. This did NOT fix the issue, which existed before that. The shudder gets worse on the highway when applying light braking force, but goes away when the braking force is increased. It can't be bent rotors, because the rotors are new, installed them myself. A bent hub could be a possibility, as I've heard tire shops can bend them with the impact guns, and the problem DID get worse after my tires were installed. How can I check for a bent hub so I don't have to spend $500 to replace both front hubs?

 

You can use a dial indicator to check both the rotors and the hub.

 

It's not unheard of to get a new rotor that is out of spec. May make sense to check the mating surfaces. Did the vibration exist before you installed them?
Time to find a MINI friend in CT. Many of we freaks have more than one set, and could let you try a different tire/wheel to eliminate that as an issue.

 

Double-check both the hubs and the new rotors for foreign material on the mating surfaces. It's a good idea to sand off any rust or corrosion on the hub faces before installing new rotors. Also, if the replacement rotors have a coating of some kind on them, make sure it's not too thick on the mating surfaces. Sand it off if this is the case or exchange your parts under warranty. If the problem still exists, use a dial indicator on the hub face to check for runout, then install the rotor along with the retaining bolt and the lug bolts (use washer to make up for the length) and check the runout of the rotor hat face. If there is runout of the hub, the hub itself will need to be replaced along with the bearing and retainer (it's an assembly). There is no actual 'axle' that can be bent here, the axle it actually an integral part of the hub. The drive axle itself does not support the hub, in fact, it's the opposite.

 

For the record, thought someone should actually say it....Our cars dont have axles!

 

heeee! Beat ya to it.

 

Well it's definetly NOT a rotor, because the problem existed when I bought the car in december, months before I changed the rotors out. I will get my hands on a runout gauge tho, and check the hubs. It would be nice if it IS a hub, since they're so easy to swap.

Edit- I can't seem to find a runout gauge on harbor freight. What can I "search for"? I don't know anyone that owns one either.

 

I hope this will help someone in the future, but I was having a speed sensitive vibration in the front end, and went through all of the normal steps.. Balancing, alignment, and pulled the wheel to check runout. What I found was that the set screw that holds the rotor to the hub wasn't properly seated in the recession of the rotor. Long story short, I had to enlarge the tapered hole in the rotor so the head of the bolt would sit down inside enough to be flush with the mounting surface. I guess it's due to maybe a mismatched rotor or something, but if anyone's having a speed sensitive, rythmic front end shake, it's worth checking!