Rear track confusion?????

[Gloucesternige]

Hi all, Nigel here from the UK.

I am trying to find out the hub to hub dimension for the GT350 vs the Mustang GT. I am asking as I have heard the GT350R brake kit for the GT widens the rear track by "about" 1/4 inch per side, so I assume the R has a wider track?

So, I started looking around and found specs on a few websites which seem to claim the rear track on a GT is actually wider than a GT350?? It seems the common dimension given is 64.9" for the GT and 63.7" for the R? (Car and Driver).

I realise that "track" can be measured in different ways, ie:- Hub to hub or tire center to tire center so this could explain the situation? So.. can anyone tell me for sure the exact extra width we get from the GT350R brake kit or the hub to hub on the GT350 R please. I assume all the suspension components, like subframe, arms etc are the same on the GT and R, with the extra width coming from the Aluminum parking brake bracket?

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[JAJ]

Hi all, Nigel here from the UK.

I am trying to find out the hub to hub dimension for the GT350 vs the Mustang GT. I am asking as I have heard the GT350R brake kit for the GT widens the rear track by "about" 1/4 inch per side, so I assume the R has a wider track?

So, I started looking around and found specs on a few websites which seem to claim the rear track on a GT is actually wider than a GT350?? It seems the common dimension given is 64.9" for the GT and 63.7" for the R? (Car and Driver).

I realise that "track" can be measured in different ways, ie:- Hub to hub or tire center to tire center so this could explain the situation? So.. can anyone tell me for sure the exact extra width we get from the GT350R brake kit or the hub to hub on the GT350 R please. I assume all the suspension components, like subframe, arms etc are the same on the GT and R, with the extra width coming from the Aluminum parking brake bracket?

This might actually be quite simple... the 2020 Mustang spec sheet from Ford shows the GT variants with 65.1 inch rear track and the GT350/GT350R with 63.7. Based on this, I'd surmise that the "track" is measured from the centerline of the tires, not the hubs. The R has wider rear rims by 1/2" and the rear wheel offset is 1/4" less putting the tire centerlines in the same place for both rims. The GT500 has different rear track measurements depending on CFTP or not - presumably the two different rims have different tire centerlines.

So, the simple answer to your question is to take the stated track width, add back the wheel offset on each side and that'll give you the width from face to face on the rear rotors.

Also, the various bits underneath - control arms, bushings, etc - on a GT350 are not the same as the GT. The differences are subtle, but important. Things like the shocks and springs are slightly different on the GT350, so while the parts look the same, mounting holes and so on can be in different locations.

 

[Gloucesternige]

This might actually be quite simple... the 2020 Mustang spec sheet from Ford shows the GT variants with 65.1 inch rear track and the GT350/GT350R with 63.7. Based on this, I'd surmise that the "track" is measured from the centerline of the tires, not the hubs. The R has wider rear rims by 1/2" and the rear wheel offset is 1/4" less putting the tire centerlines in the same place for both rims. The GT500 has different rear track measurements depending on CFTP or not - presumably the two different rims have different tire centerlines.

So, the simple answer to your question is to take the stated track width, add back the wheel offset on each side and that'll give you the width from face to face on the rear rotors.

Also, the various bits underneath - control arms, bushings, etc - on a GT350 are not the same as the GT. The differences are subtle, but important. Things like the shocks and springs are slightly different on the GT350, so while the parts look the same, mounting holes and so on can be in different locations.

Thanks for your reply.
I did exactly as you suggested today and took the centre of each wheel and calculated from there and ended up with the same hub to hub distance on GT and GT350?? We know that is wrong because the GT 350 has a different offset to the GT which is why the GT350R brake kit gives poke on a GT aftermarket wheel??
So, let’s forget the hub to hub dimension thing… you said the R wheel has a 1/4” different offset than the GT? I thought it was 10mm in the aftermarket??
Are you sure the subframe and lower and upper control arms are different on a GT vs R?
Interesting that they dropped the parking brake shoes on the GT500??

 

[JAJ]

Well, I can't explain it. It's a surprise to me that installing GT350R rear brakes changes the position of the rear wheel mounting face. It makes no sense to me that they'd change it. For instance, the rear upper control arm (camber link) is a piece of either forged or cast iron. Ford's not going to make a whole new one of those for the GT350, although they might put in a different bushing material. So, if that arm's the same, then the lower arm has to be the same. If the upper and lower arms are the same, then the knuckle (that connects with both) has to be the same, and so on. The things that were different on the GT350 and that affected the lower control arm were things like the counter-wound rear springs - the spring seats are reversed side-to-side on the GT350, and back in 2016, the GT had both springs wound the same way. The lower arms look the same on both vehicles but they're not interchangeable.

Where there might be some confusion on aftermarket rims is on the offset and brake clearance issues. The OEM GT350/R rear brakes are big. They need room to clear the rim, and many aftermarket rims don't have space inside the barrel. So, a spacer gets the job done, but now you've got a rim that pokes. I wouldn't be surprised if OEM Ford Mustang GT rims won't clear the rear GT350 brake setup. Thing is, people who run rims from companies like Apex have no problems with brake clearance, and Apex 19x11 ET52 rims work fine on GT's and GT350's with no spacer and no rubbing problems.

As for the GT500 rear brake setup, it's interesting. It has an electric parking brake, and I'm very glad I don't have one. Nothing wrong with it in particular, but if you want to change parts around, it makes it a lot more challenging when one part only works one way.

 

[Gloucesternige]

The GT 500 has an electric parking brake!! WTF??
AFAIK the GT350 parts are all the same, though I wasn’t aware they had counter wound springs. My ‘17 GT has both springs wound clockwise.
I believe the extra 6mm per side comes from the additional plate for the shoe type parking brake compared to the all in one horrible single piston thing in the GT.

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