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Brake rotor size vs wheel size upgrade path question


Drivewiththumos

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So I'm back to using the forums again (yay!) and hopefully I'll be able to get out to another even this year. But anyway, this has been a question rolling around in my head for a while. I currently drive a 2014 Mustang GT as my DD but also plan for the near future to use it as my weekend track car (HPDE only for the foreseeable future). So being what it is, I know that it could really benefit from a higher end brake setup, to help pull in all that weight. I currently do not have the factory Brembo setup, just the normal stock rotor/caliper system. Aftermarket pads and rotors work great for pulling up now, but as I add more power to the car and find myself driving better and closer to the limit, I'd rather have something a bit more (just in case). (And yes I realize that traction/handling play just as much if not more into stopping power then the brakes but that's for a different thread) I've found that I can buy/install the same Brembo package that comes standard on the GT500's for a significant brake effectiveness increase, but those up-size rotors won't fit within my current wheels. So I was planning to upgrade to a 20" size wheel to fit that brake setup, but the more I thought about it and read about other racing setups, the more I found that smaller wheels are often used for less rotating mass, inertia, etc. I don't plan (as of right now) to do any competitive racing with this car, but I also don't want to go with an upgrade path that doesn't make sense if there is something else (of comparable price) out there. So does anyone have any thoughts on this?

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There is usually a 4" difference between rotor diameter and minimum required wheel diameter on Mustangs. On my 13" rotors, I use 17" wheels. This link mentions that 14" rotors require 18" wheels. If you're going to run 20" wheels, does that mean you found a 16" rotor kit?

 

http://www.americanmuscle.com/s197-mustang-rotor-guide.html

 

20" tires are typically more expensive and less available than smaller sizes.

 

The 2013-2014 GT500 Brembo kit has 15" rotors; so, you will need 19" wheels. 19" tires are still more expensive and less available than 18" tires, but not as bad as the 20s.

 

The type of brake pads that you use can make a big difference. Note that the entry-level pads (made by any track pad company...Hawk, Carbotech, etc.) that claim that they are "for track day/HPDE use" or "for street and track" are complete junk and will give you poor performance and durability on a 3800 lb car. So, if you are using one of the lower-end pad compounds, you should switch to something like Hawk DTC-60 or Carbotech XP-10, even if you are not driving the car competitively. For a street/track car, this means that you should have a dedicated pad/rotor set for track use and another dedicated pad/rotor set for street use.

 

Also, make sure that you are running brake ducts/hoses to the fronts at a minimum.

 

You might find that, for the relatively small price difference of buying better pads, you can buy a lot of pads compared to a complete brake upgrade (for which pads could be more expensive, anyway). You might want to try this first and see what happens.

 

As the weights for wheels can vary greatly, it's hard to say that "larger diameter wheels are heavy" across the board. Some are lighter than what you currently have, while some are heavier. It basically depends on how much you spend on them.

 

Mark

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None of the good R compound tires are currently made in 20" diameters.

 

19" should work, but tend to be heavy and expensive compared to 18". Actually based on the 2015 Mustang GT PP experience (15" front rotors similar to the later GT500s), there are a few (expensive) 18" wheels that will fit.

 

Vorslag was using the 14" Brembo brakes on the front (also used on BOSS Mustangs) and the GT500 rear brakes allowing good 18" wheel & tire selection. If I had a s197 that I wanted to track, I would be looking hard at their TT3 blog/forum thread.

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Hey thanks for the replies guys. I've found that I am unable to post from work so I've been forgetting to reply now for a few days.

 

I do appreciate the input. I had noticed that at 20" tire selection is quite scarce, but the particular brake upgrade I was thinking about was: http://www.americanmuscle.com/frpp-6piston-brake-kit-0514.html

It uses 15" rotors on the front, and generally was the most bang for the buck that I could find; but I am a little worried about them fitting on my 19" stock rims. The particular rim in question I actually cannot find for the life of me anywhere else, but its the OEM rim that comes with the 'fp8 appearance package' on the '14 GT so besides a hand measurement I'm not sure what size I could look for. I was going then to just upgrade to 20" when my tread life wore out on the OEM Pirelli's but the more I thought about tracking the car the more it started to stick in my head about size ratios to (de)acceleration capability; hence the forum question.

 

I am naturally open to suggestions. The link I posted was just what I found that gave a complete upgrade for a fair price. Obviously it still isn't racing brakes, but I'm nowhere near racing the car yet. Turbo, you mention running 13" rotors? Would you mind telling or messaging me what you use, as a reference? Or if you have any good suggestions? Smike I see what you did with yours and might have to break that down later to see if it works for me. I don't mind getting my hands dirty, but my tools for DIY work are a bit limited and this car is my DD so I can't really spend a couple of days working on it. My plan for the brakes was to get a complete system and just have a shop install it in one day. Also your mentioning the rear diff overheating was new to me; I'll have to keep that in mind for later.

 

Turbo back to what you were saying about the pads, I currently have a set of HP+ pads that I have just for the track. Though they squealed like a banshee, I had absolutely no brake fade on them at Daytona last year. But then again it was Daytona (cooler track for brakes I think given all the straights??) and the ambient was only about 60F with me maybe only driving 3/10's... I did use them with the stock rotors the first time, but plan on buying a set of rotors to go with them in the future. Any word on the street Powerstop rotors? That setup with good Dot4 fluid per each event will probably suit me just fine for now as I work through the DE's. But with how complicated all the setups can be I thought it best to start planning upgrade paths for the future; again hence the post.

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A quick Google search turned up this link: http://www.mustangheaven.com/2013/new-2014-mustang-gt-fp8-appearance-package-photos/

 

Are those your wheels? I can't tell from here if they will fit or not. Note that Brembos (and others) typically stick out past the mounting face of the rotors, which will cause the wheel spokes to hit the calipers. If your wheels don't have a tall enough pad on the back side (this has nothing to do with backspacing or offset), then you will need thicker wheel spacers, and longer wheel studs, and it's just a downhill mess from there.

 

The American Muscle link that you posted has a list of wheels that will work with the Brembos; is your wheel part number one of them?

 

On my 2004 GT (note that it is approximately 3250 lbs on track), I'm just using the 2000 Cobra R front calipers with 13" rotors and SN95 Cobra rear calipers with 11.65" rotors. These clear 17" wheels all day long, as long as I stick to the ones with taller pads to clear the bigger Brembos (1995 Cobra R, 1998 Cobra, 2000 Cobra R, and 2003-2004 Cobra). I don't bother with using the blingy cross-slotted, zinc-washed, blah blah blah rotors. I use stock-style, normal-looking rotors, although they were made in either US or Canada (which are getting harder to find at parts stores). I bought 10 front rotors several years ago, made by Bendix in Canada, for $29 each on clearance.

 

For what it's worth, the CTSCC S197 Mustangs use 18" wheels; so, it is entirely possible for you to find a set of brakes to fit with this wheel size in order to have better tire availability. But, note that the CTSCC cars use high-dollar calipers from Alcon and others; you don't need to go that crazy.

 

If you're only driving at 3/10 around Daytona, then you might not notice their shortcomings. As you get faster and/or drive at more brake-heavy tracks, you will find that you need better pads (such as the Carbotech or Hawk pads I mentioned previously).

 

I admittedly use pretty cheap brake fluid (Valvoline synthetic in the blue/white bottle at the parts store for $8/quart), although I completely flush the system prior to every track weekend (note that this is a track-only car). I will usually bleed all 4 calipers on Saturday evenings to keep an eye on things. While the fluid in the stock rear brakes (when I had them) would come out gray (maybe cooked, maybe something deteriorating inside), the fluid in the front Brembos looked clean. The fluid in the Cobra rear calipers looks as clean as the front.

 

Mark

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Thanks again for the input. Yes those are my wheels. But like I said, I have never managed to find the part number itself for the wheels. I tried an image search for all of the wheels listed on the brake kit I posted but I don't think its any of them. So I guess I'll just have to go measure the ID myself and see if I can find some evidence as to what the package I listed needs or go find another set of brakes that will work. I admit I haven't looked that hard, but as I said this isn't an immediate upgrade I'm looking at. Any suggestions where to look I would appreciate. You sold me pretty good on the tire size at 18" or smaller though; I hadn't really thought that much about tire availability or cost as time goes on. So thank you everyone for your input. I think I have a slightly better view on the direction I want to go, I just need to keep looking I guess for either a smaller brake setup to fit 'smaller' 18" wheels down the road or find a kit that will fit my 19's and keep those tire availability permitting.

Thanks again.

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