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SVT brakes and why I can\'t use them. (All of them!)

Well, last week I installed the SVT front brake conversion. Yesturday I had my first track day with the new brakes. Here's where it gets interesting. Most of you probably aren't familiar with my driving habits at the track. I use every available amount of braking force that I can. Even with stock pads and rotors I was braking as soon as, or a litte later than the porsches and BMWs. (450-400 ft braking mark on the front straight at PIR). With slotted rotors and EBC pads I was braking at about the 350ft mark, which is much deeper than most of the cars. Basically I was destroying my brakes. With a cool down lap and brake ducts my rotors were reaching 537 degrees, and higher (the laser thermoeter would max out!)

That's why I upgraded to SVT Brakes. This is where my problem starts. I can only use about 70 or 80% of there potential before the tail end gets too light, the drums lock up, and I get squirrly. I can now brake at the 250 mark. Much deeper than that and bad things start to happen. Depending upon how I downshift I can hold out to 225 but I'd rather not depend on "perfect" downshifting every time. BTW this is deeper than I've seen any cars in my class brake. "What's the problem then", you ask, well the problem that I know there is more stopping power to be used, I hate that I can't use it! Also even after all this, my brakes weren't even breaking the 300 degree mark!

I am running with no back seat and no spare. I'm sure you're all saying, "well just put those bach in and your be fine!" Well, no! I'm already the slowest car out there in the straights (by a large margin!) I need every little advantage possible.

Just so you know, I can handle as good as, but usually better, than any car out there. Now I can out brake most of them but they are all SOOOO much faster in the straights that it's hard the keep up. I am pulling faster lap times than many of the people in my class, I just want to sqeeze every little bit out so I can finally advance to the next class up! The intermediate class is alway so full and advanced usually has less cars. I've had a few people tell me I should be in advaced, but those were also the people I was passing. I never heard anything like that from the people I couldn't pass!

ANY WAY that's the end of my rant!
 

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Re: SVT brakes and why I can\'t use them. (All of them!)

Manual proportioning valve might be just the ticket no?
 

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Re: SVT brakes and why I can\'t use them. (All of them!)

Are you using the stock pads? We are running the same setup and had a terrible time with the rears locking until the front pads were fully bedded with multiple heat cycles. After that it was fine.

Other possible band-aids:

Adjustable prop valve

Rubber rear brake hoses with braided stainless front hoses, to cushion rear fluid pressure response.

Higher friction front pads.

Lower friction rear shoes.

Lower car more to reduce weight transfer.

Smaller diameter wheels to lower center of gravity for decreased weight transfer.

Experiment with softer and firmer rebound damping on rear shocks.

Move battery to the rear.

Stiffer front springs to prevent rapid pitching of the car when the brakes are applied.
 

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Re: SVT brakes and why I can\'t use them. (All of them!)

All good ideas. I think the Prop valves are the best, and yes, you need two. One for each side.

I'm running with big wilwoods up front, and disk rear, and I haven't had this problem. Dunno why. I think the rears actually need more pressure. That could be one solution, get the SVT rears.
 

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Re: SVT brakes and why I can\'t use them. (All of them!)

I'm running with big wilwoods up front, and disk rear, and I haven't had this problem. Dunno why

I think the main reason may be that the increase in front bias is much greater here with this set up vs. the SVT package. Don't have piston numbers handy, but the rotor dia alone will boost the rate not to mention proper pad selection.

Vehicle dynamics aside (meaning weight, springs and shocks) the use of the drums in the back with the SVT fronts seems counter productive to me. The drums won't release as cleanly and when they get hot won't cool as well. However you are proving that they are worthy of slowing the car!

If this is a budget problem I'd just look for some higher Cf pads for the front to start with. But keep in mind more bite means more heat too. The prop valves are a decent idea, but you'll need two as mentioned unless you wish to Tee them together into and out of one. Plays hell with ABS this way though.

Surprisingly I haven't heard of anyone drilling the drums yet either...Seems maybe in this case the need for 'improvement' is a bit limited?
 

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Discussion Starter #7
Re: SVT brakes and why I can\'t use them. (All of them!)

To answer a few questions and clarify a little...

I am using stock pads and have only had the brakes on since the 17th. As for suspension, I have H&R springs with stock dampers. With 30k on the car they are dead. During the off season I'm going to be saving for some Konis or maybe go the Spax route; haven't decided yet. I think this might make a big differnce!

I'm a bit confused how higher friction front pads would help if the rears are locking up because of not enough weight. Perhaps that's only if used in conjunction with the lower friction shoes...

As for the prop valves, could some one explain a little on how I would go about doing this. ie what parts to I need?

I should also add that all this was on R compound tires. I'm a little worried about what the situation would be like on my street tires. (I don't always run the race tires.)

As for those of you with Wilwoods all I have to say is DAMN!

If I'm outbraking almost EVERYONE by atleast 50ft, how much differnce could those possibly make. It seems if they were used as hard as I'm using these...well I just don't see tires being able to keep up!

Thanks for all the input!
 

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Re: SVT brakes and why I can\'t use them. (All of them!)

I also have the Wilwoods as well and my rear end doesent get out of hand under braking. (just ask the poor victims of my 0-100-0 testing at FX03
) I think Todd is probably right with the bias thing, the Wilwood setup is massivly front biased, 12.2" rotors with huge calipers and high cf pads pretty much totally negate the stock drums in the rear.
 

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Re: SVT brakes and why I can\'t use them. (All of them!)

Yup, it feels like you are doing a stoppie!
 

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Re: SVT brakes and why I can\'t use them. (All of them!)

I'm a bit confused how higher friction front pads would help if the rears are locking up because of not enough weight. Perhaps that's only if used in conjunction with the lower friction shoes...
Higher friction pads will give you more stopping power for the same pressure.

Look at it another way, you can achieve the same front stopping power with reduced pedal pressure. That means less rear brake pressure.

--- -----------------

We are running the The SVT front with rear drums because the car started as a front drum / rear disc car without ABS. We went to the SVT fronts for more stopping power. We havenn't figured out how to upgrade to rear discs without buying the whole ABS system. Our Master cylinder has 4 lines coming out and the SVT one we looked at has 2.
 

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Re: SVT brakes and why I can\'t use them. (All of them!)

And...
The proportioning valve, if used, would slow the line pressure down based on the input pressure from the system. The adjustment is spring loaded and when the pressure goes up and up the reduction goes down and down. This way modest pressure applications still get ample rear bias to make the rears work.

The only problem with my pad selection is heat. The enemy. If you go from 120 grit to 80 grit the resistance goes up, so too the heat. Ok for a bit but when you reach saturation they won't recover for you. Here any good aftermarket kit helps by getting you a better mix of parts for what I call heat management.

Got it all now?
 

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Re: SVT brakes and why I can\'t use them. (All of them!)

Todd,

Earlier this week, I drove over to Roy's house and checked out the brake kits he bought from you for his Focus and his Gen 1 Lightning. Both are very impressive.

I'm tempted to buy a set for my Focus but have different project that I may have you quote.
 

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Re: SVT brakes and why I can\'t use them. (All of them!)

that's a GREAT sig Spike...

Never seen dogs referred to by their year
 

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Re: SVT brakes and why I can\'t use them. (All of them!)

Part of the problem is due to the fact that drum brakes work in a progressive matter whereas disc brakes are more linear. So the harder and longer you are on the brake pedal, the more effective the rear brakes become...usually about the point of turn-in or slightly before(enough to upset the car).

Also, the tired, stock shocks and struts will allow more rear to front weight transfer which does not help. If you are really into track events and autocross, I believe that you will be happier with the Koni adjustables.

I hope this helps.

Tony D
 

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Re: SVT brakes and why I can\'t use them. (All of them!)

Thanks, but I'll stay away from 'impressive'...
As a vendor, I understand why you choose to avoid using words like that, especially on a message forum.


If Roy lets me test the Focus at a track, I will definitely post my comments.

blueovalbaboon,
Thank you regarding the sig. BTW, it's all true!
 
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