DionR said

Looking for some input.

I wouldn't say I am at a crossroad, but I will say I am wavering on the S550 rear hub some. I don't like that someone has to source/machine washers and a bolt to set bearing preload. Plus, I guess they is a bit of an issue in the stock application due to losing the preload and roasting the wheel bearings. And I think the GT350/Mach 1 bearing has a better design due to the width of the bearing and both are pre-loaded avoiding the need for a bolt and washers. The only real advantage I see to the S550 rear hub is the bolt pattern is much easier to align with the LBJ bolts.

Of the two pre-loaded bearings, the Mach 1 seems to be the preferred setup. Even the GT350 bolt on hub experienced enough deflection that the speed sensors lost readings and caused issues.



I don't believe I will ever load the front suspension as much as an S550 with a 19x11 wheel, nor do I expect anyone else will. But I am always wondering if the best wouldn't be better.

I don't know where the GT350 bearing came from, but I suspect it is an Explorer application. I know it wasn't designed for the GT350 because it is splined like the rear bearing or like a 4WD/AWD front bearing. Base on OP Mustangs blog post, I believe the Mach 1 front bearing is off a 2020 or 2021+ RWD Explorer. In addition, it appears to be the same front wheel bearing used on all S650 Mustangs, so it should be easily accessible at some point.

Currently the GT350 hub doesn't seem that bad to source, but the Mach 1 hub is proving to be harder right now. Even the late Explorer hub doesn't seem to be easy to source locally, but they have a couple of options on RockAuto so I suspect it is just that they are new enough that the parts stores aren't stocking them. The Mach 1/S650 hub currently appears to be dealership only (PR3Z-1109-B).

Note that the part numbers probably won't match up between a Explorer and a Mustang, but that is due to different length wheel studs, not because the bearing is different. I don't believe it will be an issue for this application whether the Mustang or the Explorer hub is used unless someone starts building CF wheels in 18x9.5 sizes. :D

Then I tripped over this spindle:





Radial X Spindle, Gen 3, 64-70 Mustang/Cougar, FOX, SN95, SLA, Track, set

This one appears to use the GT350 hub, so other's have looked at this as well.

And it uses the S197 brake setup and lists the following as brake options:

• OEM 4 Piston Brembo Calipers (2007-2013 GT500, 2011-2014 Boss 302, 2011-2014 GT PP)
• OEM S550 6 Piston Brembo Calipers (Except GT350, GT500)*
• Brembo FF6 Pista 380x35mm or 355x35mm 2005-2014 Mustang
• Wilwood Aero6 14 x 1.25 or 15 x 1.25, 2005-2014 Mustang
• Brembo XB105 Calipers with both 355x32mm, 380x32mm rotors, 380x34mm, and also 380x35mm
• Brembo XA6 and XA4 Calipers with 380x32mm rotors or 380x35mm
• Brembo XA2.E7 4-piston (E7), 2005-2014 Mustang application 355 x 32 mm rotors
• Wilwood Aero6 with 14×1.25 rotors
• AP Radi-Cal 2005-2014 Mustang kit 372 x 34mm rotor
• Stoptech ST40 or STR40, 355 x 32 Rotors for 2005-2014 Mustang
• Stoptech ST60 or STR60, 355 x 32 or 380 x 32 rotors for 2005-2014 Mustang
• Baer 6R/S Calipers 14×1.25 rotors 2005-2014 Mustang
• Baer 6P Calipers and 14×1.25 rotors 2005-2014 Mustang

This makes me lean pretty hard in the direction of using the Mach 1/Explorer hub and setting it up for the S197 brakes. The other nice thing about the Mach 1 hub is that it is shorter between the back of the mounting flange and the face of the hub so it should make getting the LBJ bolts under it easier.

Any one have any thoughts?

I currently plan to pick up an Explorer hub from NAPA where I can return it after I take some measurements and model it. Plus I plan to try and get the offset distance I need for the S197 caliper to CL of rotor dimension this weekend. Then I will see where it all goes.

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