Billet Big Drop Spindles

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  • $2250.00

More in production - available late Summer 2024. You may place your order now to secure your set from this production run if you wish. 


We are extremely proud to be able to offer our customers our Billet Big Spindle (patent pending).  Offering a 2" drop, verifiable geometry improvements as well as a significant reduction in bump steer over the factory spindle.  3 years of engineering, CAD design and testing have produced a spindle that fits inside a 17" wheel and allows the wheel to clear the upper ball joint and steering arm.  This means you can fit up to 2" of rim and tire further inboard.  No flares required to fit up to a 10.5" rim and a 315 tire up front with only rolled fender lips.

CNC machined, Tig welded, heat treated & powder coated right here in the USA, this spindle is a major upgrade to the original Mustang spindles.  Think about it.  The original cars were designed for bias ply tires that didn't grip very well.  Now, we are using modern radial tires with lots more grip.  The early spindles are prone to breaking under harsh driving conditions with sticky tires.  If you are serious about road racing, open tracking, building a corner carving restomod or pro-touring street machine, you should upgrade your early spindles.

Tire size possibilities - measured on cars with SOT coilover and rolled fender lips:

1965-66 Mustang
1967-68 Mustang
1969-73 Mustang
17x9.5" with 6.25" backspacing & 275/40/17 tires

18x9.5" with 6.25" backspacing & 275/35/18 tires
17x10" with 6.30" backspacing & 295/40/17 tires

18x10" with 6.30" backspacing & 295/35/18 tires
17x10.5" with 6.80" backspacing & 315/35/17 tires

18x10.5" with 6.80" backspacing & 315/30/18 tires

The above chart is a guide only.  We recommend keeping the overall tire diameter around 25.5".  Due to the wide variances in early Mustang tolerances and alignment positioning, you should measure your particular car carefully and order wheels to suit.   

This kit includes:

  • 1 Pair of billet, heavy duty 2" drop spindles.  
  • Machine gray powder coated for long lasting corrosion protection.
  • Adjustable steering stops that are compatible with the stop on the SOT Strut Rod bracket.

Fitment requirements:
Naturally we have only tested these spindles with our own components.  There are an enormous amount of manufacturers in our market, it would be impossible for us to verify every combination.  Below is what we DO know is required:

  • 17" or larger wheels if you want to run wide wheels and clear the upper ball joint.  You may choose to use 15" wheels, you won't clear the upper ball joint but you will gain back more shock compression travel and gain the strength and geometry improvements.
  • SOT coilover system.  May fit other suspensions, suitability is the customers responsibility.
  • Removal of stock outer spring tower cover and use of SOT coilover shaft mounted bump stops.  Why?  If using a deep wheel/tire the stock bump stop and outer spring tower cover will have to be removed to provide clearance.  
  • 1" longer steering linkage per side.  Why?  The spindle steering arm is shorter to fit inside the wheel and 1" further outboard than stock.  We have designed and machined longer billet tie rod sleeves for factory based steering linkage with 11/16-18 RH/LH threads (part # SOT-TIERODSLEEVE-LONG).  If using a Unisteer rack, we can supply longer inner tie rod ends. Fitting other manufacturers steering solutions would be the customers responsibility.
  • Tested to work with SOT 13" and 14" brake systems with leading/forward edge caliper mount.  Why?  The upper ball joint is now much lower than the stock height spindle.  Mounting a large caliper on the trailing edge with a deep offset hat can cause interference with the UCA at steering lock.  We redesigned the caliper mounting brackets of our popular 13" and 14" brakes to move the caliper to the leading (forward) edge.  If you have these systems with the trailing/rearward edge mounting position you will need to change to the leading edge brackets (part # SOT-13-14X125BRKT-LEADING) and use our longer brake hoses (part # SOT-DROPHOSES).  May fit with other manufacturers brake systems, suitability is the customers responsibility.
  • Uses 1970-73 Mustang bearing pin size, use SET12 & SET13 bearings and 13/16-20 spindle nut/keyed washer kit.  Bearings and spindle nut kit are included in SOT brake systems.
  • Uses 1970-73 Mustang outer tie rod ends.  Use Moog ES387R for stock steering & our 1" longer Billet Tie Rod Sleeves. If using a Unisteer rack use outer tie rod end 8021330 for 70-73 Mustang and 1" longer inner tie rods available from SOT.  No room for lowered bump steer kits if using deep 17"/18" wheels.  Not necessarily required as we have corrected as much of the bump steer as possible.

tional Components:

  • Set of big inner and outer Timken bearings and races.*
  • Timken inner dust seals.*
  • Spindle nut kit - keyed washers, nuts, nut retainers, cotter pins and dust caps.*
  • Dust caps - replace those smashed in ones!*
  • Outer Tie Rods.

*Included with new SOT brake system

  If you are purchasing these spindles with one of our brake system you do not need the bearings/seals etc. shown above as these will be included (unless you want spares).

Our design criteria for this project were:

  1. Fit a 17" or larger wheel above the upper ball joint and around the steering arm.
  2. Improve upon the original spindle geometry.
  3. Utilize as many of our existing coilover and brake components as possible.

We achieved number 1 and 2 but to get things absolutely perfect we had to change a few minor components in number 3.  These items pertain to our front coilover system and front 13" and 14" brake systems.  The changes we had to make are:

1965-66 Mustangs
  • Front brake brackets - we had to switch the caliper from being mounted on the trailing/rearward edge of the spindle to the leading/forward edge of the brake rotor (part # SOT-13-14X125BRKT-LEADING).
  • Front brake hoses - the new position of the caliper will require longer brake flex hoses (part # SOT-DROPHOSES).
  • New upper coilover mounting bracket (part # SOT-6566CODROPUMOUNT).

1967-73 Mustangs

  • Front brake brackets - we had to switch the caliper from being mounted on the trailing/rearward edge of the spindle to the leading/forward edge of the brake rotor (part #SOT-13-14X125BRKT-LEADING).
  • Front brake hoses - the new position of the caliper will require longer brake flex hoses (part # SOT-DROPHOSES).

If you currently own one of our front coilover systems and/or 13"/14" brake systems you will need the above components to adapt them to work with the Billet Big Spindles.

Don't let this happen to you:


Think about this for a second. We are building cars with very capable suspensions using modern, sticky radial tires on 50+ year old spindles. I doubt the Ford engineers could ever dream of the loads we would be putting through spindles designed for skinny bias ply tires. This is not the knob on your radio were talking about. If this part fails its going to ruin your day.

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Watch this YouTube video to learn more about these Drop Spindles:

In this video Shaun from SOT gives a brief overview of some of the early Mustang spindles and their differences.

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