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We wanted to present some information on 2015+ Mustang Wheel Hubs, how to identify them and what to look for when you are upgrading your S550-S650 Hubs.
When the S550 was launched in 2014, it came with many changes over the previous S197 Stick Axle Generation. The joke was always the S550 suspension was rocket ship technology over the previous version...because it finally had IRS, something the 1989-1997 T-Bird/Cougars and 1999-2004 Mustang Cobras had. Nothing really really earth shattering, except when you took a bone stock one on a road course and found out how easily it could be driven at the limit.
With the new IRS came new wheel hub bearing assemblies, and 14x1.5mm Wheel Mounting Hardware over the previous 50+ Year run of 1/2"-20 wheel mounting hardware. Initially it was simple, there was one front hub, and one rear hub. We also use these front hubs on the 2005-2014 S197's. These are very common parts, (rear, very well known due to premature failures from lack of pre-load and some end user influenced shortened life spans) most of the aftermarket offers some form of a replacement part. Some of the aftermarket versions are pure and simply, absolute garbage with a name that unfortunately used to be a well known top quality brand.
Upon the release of the GT350 / GT350R the hub situation became a little more complicated. This vehicle line introduced 4 new hubs, making the total 6 different hubs for the recently launched S550. We then quickly determined that there was really only one new hub, and everything else was just different wheel studs. Until we get to 2020, the rear hub is unchanged for all models when you exclude the wheel studs. We build hubs with our own wheel studs so we bulk purchase whichever number is available and priced reasonably.
Ford has a habit of randomly changing prices for unknown reasons. Late last year we scoured the Country for GT350R front hubs because that week/month they were less than a standard Mag-Ride/GT350 Hub. In the past 7 years we have watched the prices with Ford, swing $50.00 week to week, on one hub. More than once have we bought up hubs because they were available only to find the next week they were $40.00/hub less, then a month later that part increases by $70.00. So we stockpile hubs and keep 30+ hubs of varying part numbers in inventory at any one time. We build a lot of hubs and if OEM wheel studs ever become highly valuable, I'm buying a boat like this...
When the Mag-Ride Option appeared in the 2018 Model Year refresh, we saw the GT350 NON-R front hubs make it to the rest of the Mustang line. That was simple enough, we now had a choice of 2 front hubs and still one rear hub for all S550 Mustangs.
2020 brought about the GT500, with a unique rear hub. This hub essentially took the MagRide/GT350 Front Hub Bearing Carrier and used the former rear wheel mounting flange. These are very easily identified by the much larger spline
hole in the center of the hub for the larger axles on the GT500. The hub mounting flange changed from the square bolt pattern to the offset/spread bolt pattern from the front hubs. They do not interchange, they will not bolt up, the axle will not fit through the hole. Below is a side by side of the rear S550 Hub on the left to the GT500 hub on the right.
As you can see in the pictures, the bearing has grown in Diameter about 6mm(0.240") which allows a larger drive axle shaft to be fitted. Interesting key points is the bearing width increased around 4.8mm (0.189") all inboard(toward the differential) which provides a fulcrum load capacity advantage (the wheel has less advantage). The GT500 hub uses the spread bolt pattern from the front hubs, and these flanges are also 1.27mm(0.050") thicker, which allows more structural integrity. The mass of the hubs increased from 3.59kg(7.92#) to 3.93kg(8.66#) so adding about 0.34kg(1.5#) to the rear of the car.
All of this increase in size and mass increase heat and load capacity. All those advantages are great(except you bascially need a GT500 complete rear subframe assembly to get all the other parts to make these hubs work), but the biggest improvement is the rear axle bearing is pre-loaded!!! That rounded lip you see is the wheel flange/drive spline all as one component, that is press formed setting the bearing pre-load. I expect this to virtually eliminate rear hub bearing failures, caused by loss of axle nut torque.
The 2024 Mustang uses the GT500 hubs, so +1 on the S650.
Around March 1st, 2021 Ford quietly changed the front suspension on the S550 with the release of the MACH 1. It is still unclear if these changes carried over to other S550's with Mag-Ride or not. We do not even know if the non-handling pack Mach 1's received this suspension change. We only know this because of a hub debacle we had, with what turned out to be a very, very patient and understanding Customer. I would fire Ford's Marketing Department on the MACH 1, as you will see later.
What we eventually figured out was that Ford redesigned the front Mag-Ride Knuckles, improving the steering geometry(Longer Levers-aka 2020 GT350R/GT500), more material around the front hub/bearing mounting area to further stiffen and strengthen the suspension...and to accommodate a completely different bearing hub assembly. GT350-GT500-Mag-Ride S550 Front hub on the left, MACH 1 Handling Pack(because we have no idea what other models they put these on) on the right.
These hubs share the wheel bolt pattern and not much else. The Mach 1 bearing Diameter is around 92mm(3.627"), down from the previous 97mm(3.823") hub from the previous S550 years but has a 5.7mm wider bearing, placing the fulcrum advantage to the bearing rather than the wheel, just as in the GT500 rear bearing. They have gone to the thinner and lighter near net forged wheel mounting flange design, similar to the rear S550 hubs but it is also unique. The Hubs are lighter, 4.02kg(8.87#) vs. 4.33kg(9.54#)with most of the weight coming out of the wheel flange which is also a spinny part and anytime you can make the spinny parts lighter there is less inertia for accelerating, turning and braking. They drop .62kg(1.37#) from the front in just dead weight.
The bolt pattern of the bearing mounting is also unique, not the same, not close. The mounting flanges are also thicker at 14.86mm(0.585") vs 13.34mm(0.525"). The thicker mounting flange is also due to the larger 14x1.5mm mounting bolts vs. the previous 12x1.5mm bolts to allow for a fastener diameter of thread engagement.
One Point about these bolts, currently they are not available from Ford, clean the old ones and apply some thread locker and torque them to spec. They are not Torque to Yield (TTY). Ford also has no idea what the correct mounting bolt part number for the MACH 1HP/S650 Hub is, the parts system still shows the 12mm bolt which is Part Number W714333-S439(Also not available) The correct 14mm hub mounting bolt part number is W721525-S439. There are 2 currently in the world, which is odd because they are all sold in sets of 4. The only reason we know the correct part number is because Leo@Capaldi Racing was able to research it and provide it to us.
Very beefy construction, because its the front hub directly out of the 2020+ 2WD Ford Explorer, an SUV with 5000+ pound towing capacity. These are designed to be very robust and that's why the mystery suspension from the MACH 1 HP is essentially what will be in the 2024 S650 Mustangs. Why Ford would not advertise that I'll never figure out. "Hey, we are building your car with parts from our future model, you get the best before everyone else"
Close up of the GT350/GT500/Mag-Ride Hubs from 2015-2023* Splined internally.
This is a close up of what we are calling the MACH 1HP/S650 Hub. No splines internally. The PDF below gives links to the hubs we offer for each specific Mustang Model.
We have since discovered since publishing this that it appears AT LEAST 2022 PP1 (Performance Pack Level 1 (Non Mag-Ride) Mustangs also come with the New Mach 1 HP Hubs and Knuckles. We are not sure exactly if its only ECO/GT PP1's or All Models. Our assumption is Base ECO/GT get the conventional knuckle with the single center nut hub, and the PP1/PP2/Mach 1 all received the New Knuckle and Hub.
Tim Hilliard - A Driving Instrutors Worst Nightmare