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Brake Options for 15" wheels!

This is a discussion on Brake Options for 15" wheels! within the Focus RS Brakes forums, part of the Focus RS Garage category; i'll take the bullet on this website and make a thread about this. lots of people on here have expressed interest on running 15" wheels ...

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Thread: Brake Options for 15" wheels!

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    Brake Options for 15" wheels!

    i'll take the bullet on this website and make a thread about this. lots of people on here have expressed interest on running 15" wheels with gravel tires. whether you agree or not, whatever thats your own opinion, but here can be a good place to discuss it.

    this is something ive been wanting to do for about a year, but instead i've just been enjoying the car as is. anyways, its been shown in photos that Team O'neil rally has been running 15" wheels on their RS while it was in development. heres some photos as proof.





    now there have been many anecdotal comments on here saying that they had run fiesta ST calipers on OEM RS rotors and they fit under a 15" wheel. the fact is no one has actually given any proof to this, and as far as i am concerned its just heresay. especially considering our rotors themselves are 350mm (13.7") in diameter, i just cant see how a 2" thick caliper is suppose to fit under such a compact wheel.

    a recent rallycross i attended has a lightly, but well prepped focus ST there. the owner was very nice and we were able to chit chat (though not as much as i would like). i notice he was running 15" wheels. i asked what brakes he was running, since i know early ST can run 16" and later ST can run 17", and he said he was running base model focus SE setup

    Untitled by 320iCar, on Flickr

    seeing it in person got me thinking again. i went back looking at all the info i could about this mythical fiesta ST caliper swap, but once again came up dry. no way i was gonna waste money on ordering parts if they dont fit. shame though because keeping the 350mm rotors would be a HUGE plus.

    so i went back and looked at some photos to try and find some reference points to give me an idea on what team oneil ran on their RS. first, i went to our friends Vorshlag and stole one of their photos. pay attention to how high the rotor goes on to the cast section of the steering knuckle, and where the coilover slides into it.

    Untitled by 320iCar, on Flickr

    so i then went to a video from team oneil when they discussed their RS in light detail. no actual concete facts given, but i was able to screen grab when they panned over the brakes. pay attention to the cast steering knuckle/coilover once again...

    Untitled by 320iCar, on Flickr

    you can see just how much smaller the rotor is on this front wheel setup than our stock RS rotors. the smaller rotor is well underneath the line of where the coilover slides into the knuckle. there is no way its the fiesta ST caliper on the 350mm rotor. so then i decided to google a stock focus SE brake setup. size of rotor, and the general design of the caliper seems pretty much exact to what team oneil was running

    Untitled by 320iCar, on Flickr


    so i talked to my good friend at ford, and he searched up some part numbers for me. as long as i get the front calipers, caliper brackets (hangers), rotors and pads, there is no reason it wont be a direct swap. the rear of the RS is known to fit with slight modification to the e-brake cable, which i believe was just trimming it down slightly. NOW, do with this information what you will... some basic things to consider

    - youre downgrading from a 4 piston brembo caliper, to a single piston unit
    - youre downgrading from a 350mm rotor to a 278mm rotor
    - you have much less pad surface on said smaller rotor
    - a stripper model base focus can weigh as low as 2800lbs. our RS are about 3500lbs.
    - it would be wise to buy a premium rotor with aggressive pads that can handle heat
    - just because you get these does NOT mean any 15" wheel will fit. look for motorsport specific wheels which are designed with different barrels

    are these brakes good enough for daily driving in city traffic? absolutely. if you have fun driving in the dirt and dont plan on being crazy competitive at all will these be fine? of course! why not! but for the love of god dont expect anywhere near the performance as our stock setup. dont go doing proper tarmac days. dont do 9/10ths tail of the dragon/mulholland drive rips and expect to come out in one piece. be smart, spend an hour changing the brakes. its so simple on our car it shouldn't be an issue at all if you know you have a certain event coming up.

    please lets keep the discussion civil. i understand lots of you may think this is a stupid idea or borderline dangerous. and hey youre welcome to that opinion. but were all car guys with different goals for our cars. lets all have fun and talk about it!
    BigFatFlip and gmoneyjive like this.

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    JWA
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    Tim mentioned the Fiesta ST brakes in one of his RS prep videos, so it isn’t just rumor. I assumed that meant rotors and calipers, not just calipers.

    I’m interested to see what you come up with. I have an RS specifically for Rallycross use. Running the stock class now, but I may move to a class that allows gravel tires at some point.

    Have you contended with the ice mode/brake assist issues, or are you thinking that less capable brakes will help minimize their affect?

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    Couldn’t use the fiesta Rotors, they are 4x108 not 5x108. Maybe Tim O’Neil just mispoke in camera.

    Yeah when I did ice-x I did run into that weird abs issue, but only a few times over 4 days. Since it’s definitelt a symptom of the ABS programming (and lets be honest, ANY brake system regardless of size will lock up on ice). I’ll experiment with it next winter by pulling the abs fuse and see if deactivating it will mess anything up. I’m looking to do time attack on ice as well where if I get a lock up at 120kmh, that could mean some serious damage into ice banks.

    I’ve had my friend price out new calipers and brackets, brand new oem ford after tax are ~$380cad. I’m sure you can get them cheaper in the states getting re-man units or 3rd party replacements. But I’d be more comfortable running true oem new since we’d be asking the most out of that tiny single piston

    Edit: I’ll keep you updated as well for suspension. I’ve already got some raceland coilovers (cheapest coils I could find with camber plates to experiment) and am ordering the generic 30mm strut spacers off of Amazon. Hopefully can get me a bit over stock with stiffer springs and more travel. Only time will tell
    Last edited by 320icar; 09-04-2018 at 11:34 PM.
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    Did you consider contacting Tim O'Neal?
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    JWA
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    Quote Originally Posted by 320icar View Post
    I’ll experiment with it next winter by pulling the abs fuse and see if deactivating it will mess anything up.
    No go on that. Pulling the fuse drops out the rear drive unit so you go FWD. The ABS unit and wheel sensors are so tied into the operation of the AWD that so far we have been unable to find any way to defeat it. The only option left on the table would be to reprogram the ABS controller itself, and I’ve been unable to find anyone who is able to do this. It doesn’t help that the RS uses an ABS controller that’s different than all other Fords.
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    Quote Originally Posted by ethosguy View Post
    Did you consider contacting Tim O'Neal?
    I have contacted them previously. They gave me no help for the brakes. I did ask about their bilstein suspension (as I have a set of bilstein b14’s from my foST) and they said they’re a basic 40mm Motorsport insert they adapted to work. NOT the same as the 40mm monotube Shock that comes with the b14 kit.

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    Quote Originally Posted by JWA View Post
    No go on that. Pulling the fuse drops out the rear drive unit so you go FWD. The ABS unit and wheel sensors are so tied into the operation of the AWD that so far we have been unable to find any way to defeat it. The only option left on the table would be to reprogram the ABS controller itself, and I’ve been unable to find anyone who is able to do this. It doesn’t help that the RS uses an ABS controller that’s different than all other Fords.
    Well shït... good thing I’m not in it to win trophies. I never had that issue on tarmac (maybe I’m just good at threshold braking) and thankfully not on dirt yet. It did happen a few times on ice but thankfully it was controllable.

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    @320icar great post! I think you are going in the right direction. From what little I've learned from doing rallycross/rally school, it's fairly common to downsize on brakes, specially for loose surface driving like on gravel and snow, in the expense of fitting smaller wheels and having more tire sidewall.

    On gravel, you are really just using the brakes for weight transfer and using turn-in to shed most of your speed (hence the need for more and stiffer sidewall). On tarmac, more force can be exerted to the road (via the tires not braking loose), so larger rotors give more surface area to apply braking force and dissipate all the extra heat generated.

    One thing I'm curious about is how switching to smaller front brakes will affect the car's brake biasing. Does anybody know how the brake bias controller works on the RS? Knowing about how the drift stick works, I'm sure there is some form of control to it. Biasing it more rear-ward wouldn't be too bad for gravel since that is pretty common anyway to help on rotation.
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    I'm sure that AP would have suitable calipers and rotors...just be prepared to pay...
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    @Nauli Yeah most euro companies can provide a custom setup. When I go spectate the CRC locally, they blast by with Rotors glowing bright red, and that’s in the snow covered winter stages! I absolutely don’t need any of that performance. I just like having fun off road and in the snow where the foSE brakes will do just fine.

    @bigfatlfip yeah it’s hard to say with the proportioning. I’d take a little more rear bias anyways since I’m way too cheap to buy the drift stick lol
    Last edited by 320icar; 09-10-2018 at 07:54 PM.
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