Suspension and Brake Upgrade Time

Why? When the fronts lock up you lose steering control. I'd think you'd want the backs to lock first if they're not locking at the same time...

 

I can see how it would with the higher coefficient of friction of .58-.60 for the XP8 and .6+ for the XP9, though Carbotech says their XP series is "Not recommended as a daily-driving street pad due to possible elevated levels of dust and noise."

 

Are you running the XP-8's, -9's or -10's?

 

Info from Eric Dahl of Girodisc I got via email regarding Brembo brake bias:

The issue you describe is exactly my concern with the Brembo kit. The front piston area is increased over OE just enough to create too much front torque given the DS1100 pad. Using the R4-S pad in the rear is a very good choice. I do not recommend using a more aggressive pad in the rear as this would likely give rise to NVH** and heat problems for the rear rotor. These concerns were brought up at Brembo, but the decision was made on a business case model not to change the rear.

In using the OE rear, the only solution to get closer to proper balance for the system is to lessen the front braking torque. This is a shame as you have paid for the brake kit as an upgrade, and it then requires "downgrading". I would suggest trying the Hawk HPS pad in the front and keeping the Porterfield rears. The HPS is less aggressive than the Ferodo over its entire temp curve. An issue that might come up here is that the front rotor has run on the Ferodo, and bedding the hawk in could bring vibrations and squeal until fully bedded. Sorry I don't have an easier solution.

We are very close to releasing the Girodisc front brake kit and 2-pc OE replacement rear for the 308 rear. We are using a dirt sealed Wilwood caliper with piston sizing closer to OE with a 310mm rotor. Our kit will also fit in the 16" wheels, which will broaden our customer base. A race kit with larger rotors and AP racing calipers will follow for all four wheels.

(**note: NVH = Noise, Vibration, Harshness. A catch all term in auto design and manufacturing for squeaks, rattles and anything that is annoying to the driver.)

 

Here's friction coefficient numbers for different pads:


Ferodo DS1100: friction number .45
Ferodo DS2500: friction number .48 to .5
Ferodo DS3000: friction number .62
Carbotech Panther Plus: number .55
Carbotech XP8: friction number .58 to .6
Carbotech XP9: friction number .6+
Porterfield R4S: .4
Porterfield R4: .5
EBC Greenstuff: .46

The Ferrodo DS1100's are what come standard on the Brembo GT kit

After my last track day, I know I definitely have too much front brake bias, especially with the new suspension components. It was too easy to lock the fronts when braking downhill (end of the chicane at Barber). Without putting in a proportioning valve, I need to adjust bias by using a harder pad in the front and/or a rougher pad in the rear. Since I had Porterfield R4S pads on all four corners before putting on the Brembo kit, and they're still on the rear, the fronts have a higher friction than the rears now. My first change is going to be putting R4S pads on the fronts also, following the suggestion from Eric Dahl, and putting EBC Greenstuff on the rears (Ferrodo DS2500 would also be a logical choice). By the way, the pads on the Brembo GT kit are Ferrari 360 pads (same shape and specs) so they're simple to order from most any high-end pad manufacturer.

For a mostly street car, Eric suggested that I probably wouldn't be happy with a >.5 pad on the rears, since they can squeal and even if they don't, when you put on the brakes they can sound like you're using sandpaper on your rotors. He also mentioned that if driving a full track day, you'd likely cook the factory rear rotors with them. He likes the R4-S pads a LOT.

 

That's interesting, since you're using the same pad composition on both front and rear.

It was likely only my inside front also that locked, considering the forces on the car at that point on the track. I was just trying to stay alive and I'm not sure I'm experienced enough to know whether it was one or both anyway since it was probably for less than a second.

 

I suggest you contact Tristram at Excelsor for the anti-roll bars and shocks if that's what you're going to be doing. He's a FCA sponsor (see www.fca-se.com/sponsors/tristram/) and offers a deal to members.

I got the ES rack mount bushings from T. Rutlands -- call Brian there at 800-233-7820. For my 308QV he send me 8 of #108244R. He had both regular rubber and the ES urethane bushings in stock.

 

It's about 300 miles after the final assembly, and I just had the ride-height reset back up a bit... it had settled down more than a half inch from where we initially put it. It got down to the point where I couldn't even straddle a normal speedbump without rubbing the body seams in the middle of the car!

 

I've been travelling some, so I hadn't had time to bed the new brake pad combination and test it out even though they'd been changed a couple of weeks ago, but this afternoon was great weather and I took the car for a workout on some little used roads.

Now that it's bedded and cycled, I can say that the new brake pad combination (Porterfield R4-S pads on the front Brembo GT setup, and EBC Greenstuff on the stock rear calipers) seems IDEAL for my car and driving style. It makes the brakes feel much more predictable than with the pad combination I had initially installed; in fact, it has pedal feel similar to the stock system (with stainless lines) I'd gotten used to, and is WONDERFULLY predictable as far as modulation and feel pre-lockup... while being VERY STRONG.

And of course now that I'm not longer uncomfortable with the new brakes, I have been able to more fully exercise the updated suspension. I didn't know it was possible to love and enjoy this car more than I already did, BUT I DO!

 

Uh, yeah, you bet!!