Mini Wheel Tub

 

The following "How To" contains information on how I performed a Mini-Tub to a 85 Mustang GT. 

Overview of the modification

To do the Mini-Tub you must remove the spring, shock and quad shock brackets from the frame rail. This will give you around 5 to 6 inches of space once removed. You will need to switch to a coil-over shock setup and after market lower control arms to eliminate wheel hop. Just pulling the shocks and installing the coil-over kit will not cure the wheel hop problem in Mustangs. The bushing on the lower control arm are oval shaped and with the axle movement under heavy acceleration, flexes causing the wheel hop. There are several lower control arms on the market that will work for this modification. You will also have to modify your exhaust system. This will require a new tail pipe from the muffler back or dumps.

Below are pictures of the spring and shock mounts that must be removed. The must be cut or ground off the frame rail.


Here is the Quad shock mount that must be removed. These can easily be unbolted from the frame rail.

You will also need to remove half the factory wheel well to make room for the larger tires. The pictures below
show the area that needs to be removed.

You will need to remove the red area using a grinder, plasma cutter or a cutting torch leaving about an 1 to 2 inches of metal from the inner side wall. The purpose of leaving this lip is to give you a better source to weld the new larger wheel tub to. You will then need to purchase wheel tubs which Summit or Jegs sell or fabricate your own from sheet metal and weld them in (blue area). You can see from the above picture how much space you will gain for larger tires. Once the modification is down I will be able to stuff 12" tires under the rear without any worries.

 

 

The following drawings shows how and where the coil over kit will reside.

 

Here are pictures of the space above the axle housing that the coil-over kit top bar will be welded in at.

Parts Needed:

Tools Needed:

 

Preparation:

 

 

 

Let's get started with the Coil Overs!

  1. Measure the distance above the rear axle housing between the frame rails as close the rear spare tire well as possible and cut the wooden dowel rod to that length. NOTE: The frame rail is not squared so you will want to make the wooden dowel rod the widest measurement and angle as needed to butt the frame rail tightly.

  2. Test fit the dowel rod in place. Make sure the rod is as far up to the top of the frame rail as possible and as close to the spare tire well as possible. The purpose of using the wooden rod is that this part is crucial and the wooden rod only cost a couple of bucks to replace instead of 30 for the metal cross member bar.
       

  3. Once the rod is correct use it as a template for the metal cross member and cut it to this size and end shape.
  4. Tack weld the bar in place very lightly. Just enough to hold it in place you will be removing it later.
  5. Next take the coil over housing brackets and position them as far apart as possible on the rear housing but between the frame rails. The ideal spot is about 1 1/2" inward of the frame rail. This allows space up top for the shock and it's hardware. The flat adjustment side of the rear coil over brackets must be vertically square with the axle vertical center line. Once you have your location, tack weld the brackets to the housing.
  6. Next hook up the L-shaped coil over mounts to the axle housing mounts leaving at least one bolt hole between the two connecting bolts.
  7. Install your shock onto the mounts and open shock fully. S&W shocks call for a maximum of 11 3/4" shock height at vehicle ride height. To figure out you're setting if using other shocks, fully open the shock and then push it back in 1/4 inch. This is the max installed height of the shock.
  8. Once you have your maximum installed height measurement, determine the location of the upper shock/coil over mounts. If the shock does not reach the to cross member bar move the shocks up on the adjustment brackets that are tack welded to the axle housing. If it is too long move it down on the adjustment bracket.
  9. Once you have determine the location of the upper  mounts tack weld the mounts to the cross member bar.
  10. Double check everything making sure everything is aligned and that you are satisfied with the placement of the coil over shocks.
  11. Remove the cross member bar by grinding the light tack welds you installed it with and fully weld the coil over mounts to the cross member.
  12. Reinstall the cross member bar and tack lightly in place. Double check everything making sure everything is aligned and that you are satisfied with the placement of the coil over shocks.
  13. Remove the shocks and finish welding the upper cross member bar  to the frame rail.
  14. Finish welding the axle mounting brackets to the axle housing. Weld 1" spots at a time alternating brackets and axle sides to avoid the axle tubes from warping.
  15. Remove the stock springs and install the coil over shocks and springs in place.

 




Pictures of the Coil-Over Setup

 

 

Hacking out the old wheel wells!

 

  1. First locate the frame rail path on the floor of the truck. It's easily identified by the spot welds running along that area. You want to trace the outside frame path on the trunk floor with a permanent marker. Make sure you trace to the outside edge of the frame rail leaving the pinch lip on the frame.
  2. Next mark the existing wheel well 1 inch from the side inner sheet metal of the car.
  3. Next crank up your nerve and cut out the area with a sawsall. You will need several blades to cut all this.
  4. Once the area has been cut out clean up your cuts and remove all old excess shock and spring mount brackets.
  5. Next bend the pinch weld lip on the frame rail over the side and hammer tightly to the frame rail. It's best to tack weld along this bend to the frame rail to keep the metal against the frame rail.


 

Installing the new wheel wells!

If you have purchased a wheel tub kit follow the instruction provided with the kit. To fabricate your own follow the direction below.

Here are pictures of my 85 with Competition Engineering steel wheel tubs. These came as a kit in 4 pieces. It incorporates a Pittsburgh lock to attach the Side panels to the wheel tub for a nice finished edge.

Fabricating your own Wheel Tubs

  1. Measure the distance from the side inner wheel well lip and the frame rail edge and add 3/4 inches to that measurement. This is the wheel well width measurement. Write it down.
  2. Next take the piece of cardboard and place it against the inner side wheel well lip and mark the height of the existing wheel well that is left and add an inch 1/2 to it. This is your wheel well height measurement. Mark it down as well.
  3. Trace the shape of the wheel well diameter on the cardboard. Cut this out and make a template out of it. Be precise as possible. This is your inner wheel well template. Put this aside.
  4. Next take a tape measure and measure around the outside diameter of the remaining wheel well from the rear trunk floor to the front floor pan adding 4inches to the total measurement. This will give you your wheel well length measurement.
  5. Using the cardboard template transfer this to the metal you will be using to make your wheel well tubs. You will want to add 1 1/2 inches to the bottom of the template for mounting reasons. You know have your  wheel well sides.
  6. Tack weld these in place vertically. Use the small 6" level for this.
  7. Next cut out your top metal and bend a 1 1/2" 90* bend at the rear end of the metal.
  8. Pop Rivet the metal into place at the bend butting the rear floor and wheel well area leaving about 3/4" over the inner pieces you tacked into place but over far enough to lay on top of the existing wheel well.
  9. Slowly roll the metal around the wheel well diameter until you get to the bottom. It may be necessary to pop rivet along the way here and there to hold the piece in place and straight.
  10. Once you get to the floor board at the back seat mark the metal at the point you wish to cut off so that you have a long enough piece to reach the floor board but also so you have enough to bend a 1 1/2" 90* lip to mount to the floor board.
  11. Attach the floor board end and make all last minute checks to ensure it's where you want it.
  12. Next cut and bend 1 or 2" tabs on the edge of the top wheel well metal towards the inner edge near the half moon inner sides you installed and bend them over the edge pop riveting every 3rd tab.
  13. Again make sure everything is aligned and either weld in place or continue pop riveting the wheel wells in.
  14. Clean up welds and sheet metal area.
  15. Finally use automotive seam sealant to seal the edges of the new wheel wells.

 

Here are pictures of an 86 Mustang with the completed mini tubs in place. These wheel tubs were custom fabricated from a sheet of steel.