I wanna know how i would go about changing the under mounted tire... i just need to know how to lower the extra tire

Usually at some point in time

You have to check & correct drive shaft angles,
the best you can, with shims on the rear spring perches
& possibly lower the trans tail housing mount

You have to check the drive shaft for being straight
& MUST have it balanced

What about Shocks?

Did you add ones with the extra travel as the lift?

Did you try different tire pressures?

Have you narrowed down the exact speed & road
conditions it starts to vibrate?

Are the rear wheel bearings on their way out?

How about installing new motor & trans mounts?

Change all diff fluids & go to full-syn

Install or rotate the tires to different spots

Keep notes & make one change at a time

Is the Suspension Bound up any where & not free
to rotate or move since lifted?

Since the spare is mounted under the rear of the car, Its not easy...you have to assemble the long crank rod out of its two pieces, then feed the rod through the hole in the top of the rear bumper and lock it into the mechanism that holds the tire in place. Once the crank rod is locked in, lower the tire towards the ground. Once the tire is low enough, you can crawl under the car and release the tire from its mount. The hardest part is locking the crank rod into the spare tire mechanism through the hole in the bumper.

Balanced Drive Shaft ?

Rear Wheel Bearings ?

Shocks ?

Tried Tires in different locations

Lower control arms. There are two bushings that are at the frame, if these are gone then it is possible for it to wobble. I would also check the wheel bearing and ball joint. To check these lift the tire off the ground. For the bearing grab the tire top and bottom push it in and out, if there is any movement the bearing is worn. If these are worn enough they to will cause a wobble. For the lower ball joint have someone put a 2 X 4 under the tire and lift as you watch the ball joint. if it moves up and down in the socket it is bad. All these together can cause a significant wobble. The lower control arm mounts to the frame and the lower ball joint is mounted to the lower control arm at the tire and the bearing is the part that holds the tire on.

This can cost thousands of dollars and there are very few parts available. The best way to approach this is to install the tallest tire you can install. Often times you can lower the RPM's enough with this method, where it is like having an extra gear in the transmission. The only other thing you would need to do is to have the speedometer recalibrated. For this get on the internet and type in speedometer shop repairs, and several places will come up. Your stock tire should be a 185 60HR 14, and every tire revolution your vehicle will travel 71.43 inches. If you use a 185 75 14 tire you will travel 78.28 inches per tire revolution, and if you use a 185 85 14 tire you will travel 82.87 inches per revolution. Taller tires will lower your RPM's just like changing the gearing. Check out the URL posted below and you can get info on different tire sizes, and custom select your tires to lower your RPM's. Be sure to check for tire clearance if you increase the height of your tires.

http://www.1010tires.com/tiresizecalculator.asp

The manual has this step in it: "remove the engine mounting bracket lower nut, stud and spacer. Carefully lower the vehicle."

It never said to raise the vehicle, so I think there is an error here.
However, it is an indication that the belt needs to slip under the motor mount.

Recommend you put a floor jack under the engine, prop it up, remove the mount stud, and lower or raise the engine as needed to get the belt out.

If you don't have a floor jack, you can accomplish the same using the car jack on the regular jack point, jacking it up, and then putting some bricks and 2 by 4s under the pan. Then let the car down until the engine touches. Take the nut off the stud and raise or lower the car as needed to open a gap for the belt to pass thru.

OK? If you have more questions, please let me know.

Welcome to FIxYa.com

rear of truck under neath frame

Regards, Lee Davidian

Thank you for using FixYa,com.

It depends on the type of car. It would help a bit to know which type of car it is. And I must say one more thing before beginning this explanation; HAVING A REPAIR MANUAL FOR YOUR CAR IS THE BEST WAY TO KNOW RECOMMENDED PROCEDURES. IT IS THE BEST $20 YOU CAN SPEND FOR YOUR CAR.

Frame- Place jack to frame or a shock/strut mount. If the vehicle is very old and you worry about mounts being weak then do not use the shock or strut mount. If the metal is weak the mount will bend and break off, then you will be asking us for tips about welding. AFTER YOU HAVE JACKED UP THE CAR ENOUGH TO DO WHAT YOU NEED: PUT THE CAR ON A JACKSTAND OR TWO. THE EXTRA STEPS ARE WORTH IT TO GUARANTEE THE CAR WILL NOT FALL ON YOU.

No Frame(Unibody)- Has a few areas where the metal has been bent and stacked to make the style more rigid. you can often find these areas around the sideskirt. You should see a sharp ridge running down the side of the car about 2-4 inches past the sideskirt. That ridge is generally okay to support Gross Vehicle Weight. I have also jacked up a car by using the lower control arm; where it mounts to the car, not the tire--DO NOT USE THE TIRE END OF THE CONTROL ARM, IT WILL RUIN A STRUT UNIT.

is there anything extra i need to know on changing the battery on my 2005 645ci bmw

According to the tech maual, you get at it from underneath...these are the steps....removing the tire may help in having the "extra room".

1. Disconnect the negative battery cable.
2. Raise and support the vehicle safely.
3. Label and disconnect the starter solenoid electrical connector.
4. Remove the mounting bolts from the starter motor, then carefully lower the assembly from the vehicle. To install:
   
5. Install the starter motor assembly complete with any shims that may be used between the engine block and the starter.
6. Install and tighten the starter mounting bolts to 17 ft. lbs.. (23 Nm).
7. Connect the starter solenoid electrical connector.
8. Lower the vehicle and connect the negative battery cable.