We get calls everyday about wheel fitment on our disc brake kit. These simple measurements should assist you in determining if your wheels with fit on a certain size rotor.

Older drum brake steel wheels have the centers welded behind the face of the wheel mounting flange and wrap around the brake drums. Most 1968 and later wheels have the steel wheel centers weld in front of the mounting flange, allowing clearance for disc brake calipers.

Today's wheels are built to clear disc brake calipers with as much as 2" of room between the back side of the wheel and the face of the caliper. However, some reproduction or drag wheels have clearance issues, because the centers are built flat. It is also important to recognize the smaller inside radius cause by the tire mounting area of the rim and where it is located in relationship to the wheel mounting flange.

It would take pages to explain the relationship the rotor diameter has on the braking force.  To make things as simple as I can, it is basically the relation of the old rotor size vs the new rotor size. 

Example: No change in tire size, going from a 11” rotor to 13” rotor.  The effective radius of the 11” with a 2” pad would be 9” and the 13” rotor with the same pad width would be 11”.  Or 11 ¸ 9 = 1.22 or 22% more efficient.

10.75" rotors 14" or larger rims
11.00" rotors 15" steel rims & all reproduction wheels
11.75" rotors most 15" after market aluminum wheels
12.19" rotors most 16" after market aluminum wheels
12.90" rotors all 17" rims
14.00" rotors all 18" rims

Try to order the largest rotor and caliper combination possible based on you wheel cleanances. I highly recommend using the 11.75" rotor on 15" rims instead of the 10.75" and the Forged or Billet Superlites or the new DynaPro 6 Piston Calipers. These calipers have a 4.75" long brake pad vs 3.96" on a Dynalite Caliper.

Example: 4.75" vs 3.96" = 1.20% or 20% more braking with the same amount of force (pressure).

The bottom line is 10% here, 20% there all adds up to additional braking for the same or little more cost. What is a humans life worth?

To understand more about your brake system read my Brake Article or Frequent Asked Questions

1. With your wheels face down, take a straight edge and lay it on the wheel mounting flange and measure the diameter.

2. From the outside diameter of the straight edge measure the clearance you have for calipers. Allow 2 to 2.25" wide for the height of the caliper body.

Notes:
a. Based on a 1.71" offset hat. Plus or minus calulations for this starting point. The majority of our custom kits use the 1.71" offset hat.
b. Lug mount style calipers.
c. Most Superlite 6 Piston Calipers are used with a 12.90" or larger rotor and 1.88" - 2.00" offset hats. 0.15" - 0.45" clearance with a 2.00" hats