Logan's Gen 3 Coupe-R Build

[Logan]

I really like the idea of not running spacers, but I do like the look of the CF5 better. Decisions, decisions...

Question: When you drilled your hubs for the ARP wheel studs did you also have to drill out the rears?

I also really like the CF5. I ran that face-style on my Mustang for the past 3 years and absolutely loved them. Classic 5-spoke look, simple yet elegant, easy to clean... On the other hand I also like the look of the F14s, but it pretty much came down to available sizes that made that decision for me. SDC profile and 12" to 13" widths available in the F14, previously with as low as +6 offset, but now with UDC profile they go as low as -50 offset which is nice. I would not hesitate to use a spacer with CF5s or SDC-profile F14s if needed.

As for the hubs, remember the rear hubs (if you go with IRS) are already M14x1.5 studs as they are S550 Mustang spec. FFR would have you replace the beefy M14 rear studs to match their 1/2" studs in the SN95 front hubs... but I prefer to keep the larger of the two. Especially since it's standard issue on many (most) performance cars today. Better clamp load, higher yield strength, handles frequent torque cycles better, etc. To achieve this, you only need to ream out the front SN95 hubs to roughly the size of the rear hubs holes. There's science behind knurl diameter, material displacement, and so on. But long story short, I have done the science and have confirmed results. Buy a 0.612" diameter reamer from McMaster Carr, and within 5 minutes at the drill press you're ready to press in a 0.625" knurl-diameter M14-stud of any length you desire. The reamer is $50, and has little other use besides this, but very much worth it to do it right. Cuts the hub material like butter. Do NOT take a regular twist drill to your hubs!

[Snowman]

I also really like the CF5. I ran that face-style on my Mustang for the past 3 years and absolutely loved them. Classic 5-spoke look, simple yet elegant, easy to clean... On the other hand I also like the look of the F14s, but it pretty much came down to available sizes that made that decision for me. SDC profile and 12" to 13" widths available in the F14, previously with as low as +6 offset, but now with UDC profile they go as low as -50 offset which is nice. I would not hesitate to use a spacer with CF5s or SDC-profile F14s if needed.

As for the hubs, remember the rear hubs (if you go with IRS) are already M14x1.5 studs as they are S550 Mustang spec. FFR would have you replace the beefy M14 rear studs to match their 1/2" studs in the SN95 front hubs... but I prefer to keep the larger of the two. Especially since it's standard issue on many (most) performance cars today. Better clamp load, higher yield strength, handles frequent torque cycles better, etc. To achieve this, you only need to ream out the front SN95 hubs to roughly the size of the rear hubs holes. There's science behind knurl diameter, material displacement, and so on. But long story short, I have done the science and have confirmed results. Buy a 0.612" diameter reamer from McMaster Carr, and within 5 minutes at the drill press you're ready to press in a 0.625" knurl-diameter M14-stud of any length you desire. The reamer is $50, and has little other use besides this, but very much worth it to do it right. Cuts the hub material like butter. Do NOT take a regular twist drill to your hubs!

Thanks for the heads up on the reamer and confirming only the front hubs would need to be reamed out! ARP actually recommends a 39/64 drill bit for their longer S550 wheel studs. The reamer seems like it would be easier to keep the holes centered up.

Still haven't made up my mind yet, I like the sounds of keeping things simple without using spacers on the new F14 profile, but I prefer the look of the CF5. They both look great honestly so i really don't think there is a wrong decision, lol. Ultimately I think I'll let the price of either path guide me. Those ARP studs are NOT cheap! I guess I need to ask Forgestar for quotes and see where that takes me. Plenty of time to get that figured out.

[Logan]

ARP actually recommends a 39/64 drill bit for their longer S550 wheel studs. The reamer seems like it would be easier to keep the holes centered up.

39/64” would leave just over 2 thousandths more material in the holes than the 0.612” reamer I used. Either of those sizes will work just fine, as there is a small allowable range for spline press-fitments. I prefer a reamer to a twist drill because it leaves a perfectly round hole with parallel sides, perpendicular to faces, etc. Machinists use reamers to clean up and perfect the rough hole made by a twist drill. I’m sure you could find a 39/64” reamer too actually.

I agree you can’t go wrong with either the CF5 or the F14. Looks like the UDC profile is about $280 more per set of four ($70 per wheel) compared to the SDC profile, for a given size. UDC is only available in 19” diameter, while F14 SDC and CF5 are both available in 18” if that influences your decision at all?

The ARP 100-7733 studs are about $60 per pack of 5 (There are cheaper options for extended studs, such as Dorman, but not the same strength as ARP). You would only need extended studs if you planned to use a slip-on spacer between 0-1” thick. If you need more than 1” of spacer, you’d be better off using standard length studs and a bolt-on spacer. For track or racing use, a slip-on spacer is preferred to a bolt-on. However, a wheel with the proper offset which requires no spacer is naturally the best method if possible.

[Shakey]

39/64” would leave just over 2 thousandths more material in the holes than the 0.612” reamer I used. Either of those sizes will work just fine, as there is a small allowable range for spline press-fitments. I prefer a reamer to a twist drill because it leaves a perfectly round hole with parallel sides, perpendicular to faces, etc. Machinists use reamers to clean up and perfect the rough hole made by a twist drill. I’m sure you could find a 39/64” reamer too actually.

I agree you can’t go wrong with either the CF5 or the F14. Looks like the UDC profile is about $280 more per set of four ($70 per wheel) compared to the SDC profile, for a given size. UDC is only available in 19” diameter, while F14 SDC and CF5 are both available in 18” if that influences your decision at all?

The ARP 100-7733 studs are about $60 per pack of 5 (There are cheaper options for extended studs, such as Dorman, but not the same strength as ARP). You would only need extended studs if you planned to use a slip-on spacer between 0-1” thick. If you need more than 1” of spacer, you’d be better off using standard length studs and a bolt-on spacer. For track or racing use, a slip-on spacer is preferred to a bolt-on. However, a wheel with the proper offset which requires no spacer is naturally the best method if possible.

Any idea if the Forgestar F14 UDC in a 19in would fit? I'd guess a 325/30r19 tire. I agree it would be great to get a F14 on there with a 315+ width tire and no wheel spacer.

V/R

Shakey

[Logan]

Any idea if the Forgestar F14 UDC in a 19in would fit? I'd guess a 325/30r19 tire. I agree it would be great to get a F14 on there with a 315+ width tire and no wheel spacer.

V/R

Shakey

The wheel itself is just a 19” x 11” or 12” (however wide you choose). Between the SDC profile and UDC profile, you can now get the offset you want built into the wheel so no spacers are required. Even for FFRs where we need low or negative offsets, that’s where the UDC profile comes in.

It’s the tires that are critical for total fitment. Average 18” tire options are 25.5” diameter for 315/30, and 25.9” diameter for 335/30. Moving up to 19” wheels, tires from 315/30 to 325/30 to 345/30 are 26.5” to 27.2” in diameter. So a total of 0.6” to 1.3” taller in diameter, and half of that in radius. The first point of contact with large tires is the short angled square tube of the Coupe chassis behind the seats. Set the wheel offset such that the tire has good clearance to this tube and you should never have any problems. I still really wish they would offer the UDC wheel in 18” as I prefer the tire options there.

[Shakey]

The wheel itself is just a 19” x 11” or 12” (however wide you choose). Between the SDC profile and UDC profile, you can now get the offset you want built into the wheel so no spacers are required. Even for FFRs where we need low or negative offsets, that’s where the UDC profile comes in.

It’s the tires that are critical for total fitment. Average 18” tire options are 25.5” diameter for 315/30, and 25.9” diameter for 335/30. Moving up to 19” wheels, tires from 315/30 to 325/30 to 345/30 are 26.5” to 27.2” in diameter. So a total of 0.6” to 1.3” taller in diameter, and half of that in radius. The first point of contact with large tires is the short angled square tube of the Coupe chassis behind the seats. Set the wheel offset such that the tire has good clearance to this tube and you should never have any problems. I still really wish they would offer the UDC wheel in 18” as I prefer the tire options there.

Thanks for the info. That's good gouge on the angled square tube on the drivers side. I agree that a 325/30r19 is only 1/2 in or so larger than what FFR recommends for the coupe so it should be able to fit in there. I would like to see forgestar expand their lineup because I like a lot of their other designs too but the offsets are soo limiting. If I had my way, I would get a forgestar CF5V in a UDC 18x12 rim with a -25 offset. I guess I'll have to start writing letters to their president.

V/R

Shakey