A while ago I was trying to figure out if the set of GT500 all season tires I use for fall and early spring would fit my new GT350. They're 265/40x19 and 285/40x19 on genuine Ford 2013/14 GT500 base (silver) rims. All four tires are on 19x9.5 front rims.
It turns out they almost fit, but the GT500 front rims need a spacer to clear the brakes - about 15mm or so. The good thing about 15mm spacers is that they're truly hub-centric. The bad thing is, they need longer studs. What's also good about 15mm spacers is that you get pretty much the stock offset - ET44 becomes ET29 and the stock GT350 rim is ET30.
The other thing I was trying to figure out was how to run a square set of 11" rear rims on the car when my MPSC2 tires (in "R" sizes) come. It turns out that a stock GT350 11" rear rim with a 1.5" spacer behind it is dimensionally the same as a stock GT350R front rim. 19x11 ET24.
So, how do you make all this work? Well, the Motorcraft HUB-299 is the OEM replacement front wheel hub for a GT350R. The CF rims are thick at the mounting point and the R front hub comes with studs that are about 40mm longer than the stock GT350 front studs. The R hub with the long studs gives you the option to use 2013/14 GT500 rims, rear GT350 rims as front rims and if you get a 25mm spacer, you can run the N4SM 19x11 ET 50 rims square as well. And if someone ever blows out a set of R CF rims on EBay, you can install a set of HUB-308's on the back and run the CF's all around!
Today, I swapped out my stock GT350 hubs with a pair of HUB-299's. If you have the right tools, it takes about half an hour to change each one. The process is simple - put the car up in the air. I have a lift, but stands will work fine, so long as both front tires are off the ground so you can rotate the steering wheel to improve access to the bolt heads.
Take the front tires off and remove the brake rotors. To keep the calipers under control, I bought the long m14x2 bolts described in another post on this forum and they make it pretty simple. Remove the upper T60 caliper bolt and replace it with a long bolt screwed in about 5 turns, then remove the lower T60 bolt, slide the caliper out and lift off the rotor. Also, take off the wheel speed sensor so it's out of the way of the wrenches you'll be using on the hub retainer bolts. It's on the back of knuckle about half way between the two front hub mounting bolts. You'll need a 7mm socket. Don't forget to put it back when you're done. I used a pair of cheap pry-bars (grey square shafts, black square handles - they're everywhere) back-to-back to pry my brake pads apart just a fraction so they're easy to slide over the rotors later.
Swapping the actual hubs is pretty easy, although each of the four retainer bolts comes off easiest with a slightly different tool. If you've got a 3/8 drive socket set with a long flex handle, a torque wrench good to 100ft-lbs and an 18mm crow-foot wrench (socket), you'll get them swapped pretty quickly. An 18mm box wrench and an 18mm flex-head ratcheting box wrench are very helpful too, but not essential. Position the steering wheel to improve access and use new bolts and torque to 98 ft-lbs. I was amazed at how accessible the bolt heads were - usually these kinds of bolts are buried behind a forest of obstructions, but not these ones! Also, as I said earlier, don't forget to reinstall the wheel speed sensor.
I put on a set of H&R 15mm hub-centric spacers and mounted up the GT500 rims and tires. I used GM OEM open end wheel nuts pn 9595174 and torqued them to 145 ft-lbs. The Michelin AS/3's drive really well and they're quieter than the MPSS's. Not surprising, really. I've got a set of new-take-off 2014 GT500 Performance Pack rims that might look better on my black GT350 than the silver base rims - I'll give them a try next weekend. My other decision point comes up when I get my MPSC2's - will I mount them on a regular front-rear GT350 rim set (I have a set) or on 4 rear rims (yep, got them too)? Time will tell - stay tuned.
It turns out they almost fit, but the GT500 front rims need a spacer to clear the brakes - about 15mm or so. The good thing about 15mm spacers is that they're truly hub-centric. The bad thing is, they need longer studs. What's also good about 15mm spacers is that you get pretty much the stock offset - ET44 becomes ET29 and the stock GT350 rim is ET30.
The other thing I was trying to figure out was how to run a square set of 11" rear rims on the car when my MPSC2 tires (in "R" sizes) come. It turns out that a stock GT350 11" rear rim with a 1.5" spacer behind it is dimensionally the same as a stock GT350R front rim. 19x11 ET24.
So, how do you make all this work? Well, the Motorcraft HUB-299 is the OEM replacement front wheel hub for a GT350R. The CF rims are thick at the mounting point and the R front hub comes with studs that are about 40mm longer than the stock GT350 front studs. The R hub with the long studs gives you the option to use 2013/14 GT500 rims, rear GT350 rims as front rims and if you get a 25mm spacer, you can run the N4SM 19x11 ET 50 rims square as well. And if someone ever blows out a set of R CF rims on EBay, you can install a set of HUB-308's on the back and run the CF's all around!
Today, I swapped out my stock GT350 hubs with a pair of HUB-299's. If you have the right tools, it takes about half an hour to change each one. The process is simple - put the car up in the air. I have a lift, but stands will work fine, so long as both front tires are off the ground so you can rotate the steering wheel to improve access to the bolt heads.
Take the front tires off and remove the brake rotors. To keep the calipers under control, I bought the long m14x2 bolts described in another post on this forum and they make it pretty simple. Remove the upper T60 caliper bolt and replace it with a long bolt screwed in about 5 turns, then remove the lower T60 bolt, slide the caliper out and lift off the rotor. Also, take off the wheel speed sensor so it's out of the way of the wrenches you'll be using on the hub retainer bolts. It's on the back of knuckle about half way between the two front hub mounting bolts. You'll need a 7mm socket. Don't forget to put it back when you're done. I used a pair of cheap pry-bars (grey square shafts, black square handles - they're everywhere) back-to-back to pry my brake pads apart just a fraction so they're easy to slide over the rotors later.
Swapping the actual hubs is pretty easy, although each of the four retainer bolts comes off easiest with a slightly different tool. If you've got a 3/8 drive socket set with a long flex handle, a torque wrench good to 100ft-lbs and an 18mm crow-foot wrench (socket), you'll get them swapped pretty quickly. An 18mm box wrench and an 18mm flex-head ratcheting box wrench are very helpful too, but not essential. Position the steering wheel to improve access and use new bolts and torque to 98 ft-lbs. I was amazed at how accessible the bolt heads were - usually these kinds of bolts are buried behind a forest of obstructions, but not these ones! Also, as I said earlier, don't forget to reinstall the wheel speed sensor.
I put on a set of H&R 15mm hub-centric spacers and mounted up the GT500 rims and tires. I used GM OEM open end wheel nuts pn 9595174 and torqued them to 145 ft-lbs. The Michelin AS/3's drive really well and they're quieter than the MPSS's. Not surprising, really. I've got a set of new-take-off 2014 GT500 Performance Pack rims that might look better on my black GT350 than the silver base rims - I'll give them a try next weekend. My other decision point comes up when I get my MPSC2's - will I mount them on a regular front-rear GT350 rim set (I have a set) or on 4 rear rims (yep, got them too)? Time will tell - stay tuned.
Anyway I don't own an 18mm 3/8" socket (only 1/2" drive) nor do I own an 18mm crows foot. While I do own an 18mm ratcheting box wrench it's not a flex head. I was able to get the hubs off, replace the 1/2" for 14mm wheel studs, and get it all back together. Then of course I couldn't torque them properly so I got them Just Tight Enough. 
