medgrill

I was just wondering if i was the only one that when i open it up a little maybe 90 that when i hit the brakes to slow down the brakes just fell like their vibrating. I can feel it threw the petal has any one else experience this. Just want to know what it is if its normaland what i can do about it. Thanks for the help.

Vapour Trails

Typically that is warped rotors. If could also happen if the wheels are not torqued evenly or maybe if they are unbalanced.

stangNV

mine did that about 3-4 months after i got the car...im not really sure what it is, i thought it was the rotor getting hot but if you get a deifnite answer that is correct i would like to know

GidyupGo

Warped rotors is the correct answer, if you don't have something that has come loose.

Getaway

Sounds like warped rotors. Have a reputable brake specialist turn the rotors (essentially grinding them straight again). However, it's possible that they are beyond repair. Know that once warping has begun, it'll only continue getting worse. Turning the rotors is a patch fix and may be done several times, but replacement is the only true repair.

Advise:
Don't use the "emergency hand brake" as a "parking brake" while the rotors are still hot from driving. It'll warp the rotors as they cool unevenly. Parking brakes are the devil.

F1Fan

Hi medgrill,


The folks who are saying your rotors are warped are most likely wrong, your rotors are probably not "warped." You can confirm this by simply pulling off one wheel and using a stack of washers to shim up a couple of lug nuts and screwing on a couple of lug nuts to hold the rotorfirmly onaxle hub. Using a dial gauge or even a simple fixed pointer set the pointer so it just touches the rotor and then rotate the rotor using the studs. Watch the rotor and pointerto see of the pointer is being moved out of place. If the rotors are really warped you shouldsee the rotors movingyourpointer and them pulling away from the pointer. If you set up your test and measurecarefully you canget some real data.

Chances are your rotors are vibratingdue to pad material building up unevenlyaround the rotors. What you are getting is an oscillation caused by the slight high spot and change in friction as the brake pads grip and slip over and over due to pad build up in that location. As this progresses it gets worse and worse over a very short time and the rotors will become hardened in those spots. Just throw them out, they cannot be reused even if you turn them aggressively as the hard spots will remain in the rotor material.Try this,go and look carefully at the surface of the rotors. Do you see any bluish discoloredareas all around the rotor surface? They usually appear as evenly spaced blue tinged spotsabout 1"-2" across andusually evenly spread around the rotor right in the center of the pad area. This is very common on stock GT front brakes. My ownrotors also developed heat checks in the blue hot spots which was not a happy thing to see on a street (some times track and canyon) driven car.

There is something about the stock pad compound and the stock rotors that causes this to happen.Many people myself included haveexperienced this problem andFord usually just says this is a service item and that you get to pay for the new parts. Of course the second time you bring the same problem to them and they act like it is the first time they have ever seen this on an S197 they will act dumbfounded and tell you that you get to pay them again. My suggestion is to avoid the problem all together andbreak this expensive cycle. Toss the rotorsif they are showing the blue spots as they havebeen hardened and will just do the same thing in rather short order. Do NOT buy another set of Ford rotors! Buy quality replacements from third parties, Stoptech, Brake Pros, Baer etc. all sell higher quality rotors.

I also suggest that you buysome good brake pads from Ferodo DS2500, Hawk HPS pads,EBC Yellow 'R' Compound Pads or the like. The DS2500 pads are near race padsand as such need some heat to work well but once up to temp are some of the best pads available that can still be used on a street car. The Hawk HPS pads are a very good street pad with minimal dusting, no squeaks and stop well from cold and even have a decentmax operating temp so they can reach well into the sporty driving heat range. EBC Yellow'R' compound pads are much like the HPA pads butand havea higher heat range they work well in. I also suggest replacement of your front rotors with a quality one piece rotor and the installation of Goodridge stainless steelbrake lines and a complete fluid flush using ATE Gold/200 or My favorite Motul RBF600 racing brake fluid.

Of course this problem is largely caused by heat and using the brakes outside the MOT of the padmaterial. To combat this I suggest you install some way to cool the brakes. Spindle mounted brake ducts are the best solution if you plan to drive the car hard or on a road course.Look into kits from Quantum Motorsports, V8 Power, Kenny Brown, Steeda, Agent 47 etc. allhave parts and kits that will solve the heat issues you have.

HTH!
<<EDITED forclarity>>

GidyupGo

Don't listen to him. ^^^^ More than likely it's the rotors warped due to excessive heat buildup at speeds of 90 mph.

F1Fan

Hi GidyupGo,

This is not meant to slam or embarras you but ignorance is bliss no? Go and do some research on brake "warpage" and you will learn you don't know what you are talkling about. there are several good books about high performance brake systems but you probably won't take the time to invest in actually learning about them so let's try something possibly more your style. Try googling "brake pad materialtransfer" or "brake rotor warpage" and then come back and tell us what you've learned.

LOL 90MPH? You have to be kidding, 90MPH is NOTHING even for stock sized brakes if you have good brake components in place and a way to cool and shed the heat from repeated braking at higher speeds. Many people with our cars are traveling well in excess of 140MPH on some of the bigger tracks here in California and they do it on stock size brakes with stock calipers. Of course they have upgraded to race pads, racing brake fluid, SS brake lines, spindle mounted brake ducts with hose to a nose mounted duct and always take as many cool down laps as possible and park in gear and/or chock the wheels at rest.

Hope This Helps!

GidyupGo

You don't know what you are talking about. I suggest you try to simplify the trouble shooting before bringing out the big guns and all that mumbo jumbo. Read this article and learn something. Never too old to learn. 90 MPH is indeed enough speed to roast a stock settup like ours. What planet are you from? Oh, I know....California. Enough said.
http://autos.yahoo.com/maintain/repa...ques003_3.html

F1Fan

Hi medgrill,

Obviously Gidyupgo didn't even read and understand the article he linked to. The page he refers to as some sort of authority suggests doing exactly as I suggested you do, measure the rotors. It also mentions the same blue spots and rotor hardness problems that extend deep intothe rotor material itself. Where the page fails is in understanding the root causes of the vibration which is caused by TV or uneven depositing of pad material around the rotor surface.

I suggest that before you waste your money at the dealership or at some other shop trying to turn the rotors and installaing more stock parts which obviously were inadequate for your use that you go to the StopTech website and read their white papers about Thickness Variationof pad material depositson rotors. This is the heart of the vibrations you are experiencing. You can try the cheaper route but it will be money down the drain.

Here are some of the most clearly written and easy to understand docs on brakes you will find any where on the internet. Read them andsee for yourself: StopTech White Paper Link

HTH!