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Old 05-05-2002, 11:10 AM   #1
romanom
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Default I'll call it, "Mini brake test"

Me and 2 friends performed a little brake test this morning.

I have a friend that works at Teterboro Airport and was able to gain access to a nice flat and large area. Not a runway.

To make it interesting we brought my 2000 BMW 328i with sport package.

Atomsphere Conditions at the time (benefit of being at an airport):

Temp: 54 F , Humdiity 55% , Barometer 30.28in and rising , Wind 6 MPH East, partly cloudy

Surface was perfectly dry and smooth. Surface was concrete.

The vehicles:

2002 Impreza WRX Sportwagon with manual transmission, SSR Competition wheels, 225/45ZR17 Bridgestone Potenza S-03 PP tires, Tein H-Tech springs, rear 20mm anti-roll bar. All else stock, including brakes.

2000 BMW 328i with manual transmission and the sport package, all stock. The tires: 225/45ZR17 Michelin Pilot Sports.

The WRX tires have 650 miles on them, the BMW tires have 7000 miles on them. All pressures where set at the recommended settings as posted on the driver's door jamb.

WRX has 720 miles on the pads, the BMW has 7000 miles on the pads.

Test procedure:

10 consecutive stops from 60MPH (using the car's speedometer, so chances are it wasn't exactly 60MPH). That's all I had the time to do.
Consecutive means the time it took to turn around get back to the start and then 30 second wait.

3 drivers. Myself, worked as a brake engineer and have expierence on well over 100 different vehicles. Driver 2, Ralph, is a "car guy" and knows how to drive. Driver 3, Carmine, good driver but not a "car guy."

All numbers are rounded to nearest whole number, so no 120.5 feet, That would be listed as 121 feet. I do this because of the nature of the test and the measuring equipment. Which consists of 10 cones spaced 15 feet apart and a tape measure.

The BMW's DSC (ESP system) was turned off, so both cars had ABS only working.

For time reasons I was the only driver to do all 10 runs. Ralph and Carmine just did one each in each vehicle 15 minutes after I was done to add subjective data.

The results (all in feet):

-------------------------WRX----------------------BMW-------------------
Run 1.......................121....................... .....117
Run 2.......................121....................... .....116
Run 3.......................121....................... .....116
Run 4.......................123....................... .....117
Run 5.......................125....................... .....117
Run 6.......................125....................... .....119
Run 7.......................128....................... .....121
Run 8.......................133....................... .....121
Run 9.......................133....................... .....121
Run 10.....................133........................ ....121

Take these numbers for what their worth. Please keep in mind the difference in tires and miles on them. And the "test equipment" used. Disclaimer: This is for entertainment purposes only.

Subjective comments:

Me:
The WRX started out quite impressive and the feel didn't go away all that much, but I could really tell that each run required a little bit more pedal travel. Stability is actually quite good, the WRX stopped straight and true each time. And with the Tein springs dive was not to bad. Pedal feel was nice and firm and brakes where easy to modulate. The system does have too much lost travel, especially compared to the BMW. The WRX does have excellent feedback through the brake pedal though. However, it does not compare to the BMW, it has almost no dive under braking. Stability on the BMW is absolutely perfect and pedal feel is spot on. The WRX is well above average, but not quite great.


Ralph:
"The WRX is really nice compared to my Lexus, but once you drive the BMW you can really feel the differences. The WRX pedal feels a little soft in comparison and I need to push more on the pedal. But the car does brake nice and straight."

Carmine:
"The WRX does feel like a real 'Sportwagon' but man it ain't no BMW. The BMW felt like there was no friction or any tolerance in the system. All I have to do if touch the brake pad a little on the BMW and I start stopping. The WRX I have to push to much."


Some important numbers on the BMW:

Curb Weight: 3197lbs , Weight distribution front/rear: 50.5/49.5, brake setup: single piston sliding calipers front and rear with 11.8 inch front rotor and 11.6 rear rotor both ventilated.


Some important numbers on the WRX Sportwagon:

Curb Weight: 3165lbs , Weight distribution front/rear: 58.5/41.5,
brake setup: dual piston sliding caliper up front and single piston sliding caliper in the rear with 11.4 ventilated rotor in front and 10.3 inch solid rear rotor.



Off Topic:

On the way back I let Ralph drive the WRX and Carmine drove it on the way to the airport (about a 20 minute drive):

Comments:

Ralph: "Wow, what a fun car to drive. Great seats and steering. I might get one!"

Carmine: "Love that engine. It is a really fun car to drive"
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Old 05-05-2002, 11:16 AM   #2
GoodFinder
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Default

Very interesting. Thanks for the posting!

GoodFinder
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Old 05-05-2002, 12:02 PM   #3
romanom
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Default

Just want to add some more personal opinions:

I think the WRX actually did quite well compared to the BMW. Yes the BMW trounced the WRX, but the BMW has certain advantages that can be addressed on the WRX.

1. The BMW uses a very good DOT4 brake fluid whose characteristics is very close to ATE Super Blue. It's just as expensive.

2. The brake pads on the BMW are as aggressive as any of the better street pads. They dust like crazy and wear in no time. I have 31,000 miles on the BMW and have changed pads 3 times, all street driving. The SSR wheels have been on the WRX for 600 miles and there isn't that much dust on them. After 600 miles the BMW wheels would have not a sinlge square milimeter of wheel showing under the dust. You don't know what a dust problem is until you've owned a BMW!


I think with better fluid and some better pads that the WRX would have done much better. It still won't get to the BMW in feel and performance because the BMW has much stiffer components (and significantly more expensive, the booster alone is 4 times more expensive than the type in the WRX) and the BMW just has the better dynamics.
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Old 05-05-2002, 03:07 PM   #4
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Quote:
It still won't get to the BMW in feel and performance because the BMW has much stiffer components
I'm curious how much stainless steel brake lines would help the feel of the pedal. It probably wouldn't feel as stiff as the BMW, but I would imagine it would help.

Buster
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Old 05-05-2002, 03:09 PM   #5
romanom
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Default

Quote:
Originally posted by EvasionOfTruth
[QOUTE]It still won't get to the BMW in feel and performance because the BMW has much stiffer components


I'm curious how much stainless steel brake lines would help the feel of the pedal. It probably wouldn't feel as stiff as the BMW, but I would imagine it would help.

Buster
[/quote]

Oh yeah!!!!

I was refering more the parts you can't really switch out, like the dash, body, etc....
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Old 05-05-2002, 03:14 PM   #6
EvasionOfTruth
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Doh

Buster
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Old 05-05-2002, 03:57 PM   #7
romanom
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I bet that with the 4-pot Subaru system found on cars sold in other markets and good set of aggressive pads and steel lines it will get very close to the BMW in both feel and performance.

Calipers and lines for feel and pads for performance.

BMW has the big advantage of...........CASH to spend.





*I'm still a little surprised by the amount of fade on the WRX..it was more than I expected....12 feet or 144 inches...that's alomost a car length.
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Old 05-05-2002, 05:53 PM   #8
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I can only be thankfull that Subaru are sending these shopping cart brakes to the U.S and not here.

STi 2002 = 326mm x 30mm Standard 12.8"
Evo VI & VII = 320mm x 32mm Standard 12.6"
Nissan GTR = 326mm x 30mm Standard 12.8"
Audi S4 = 320mm x 30mm Standard 12.6"
Toyota Supra = 323mm x 30mm Standard 12.7"

Can anyone see a trend here for turbos !!!!

Steve.
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Old 05-05-2002, 06:02 PM   #9
romanom
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Aw, we Yanks can't drive anyway!



The US tends to get the power, but gets ripped off on the turning and stopping!
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Old 05-05-2002, 07:08 PM   #10
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Quote:
Originally posted by romanom
Aw, we Yanks can't drive anyway!



The US tends to get the power, but gets ripped off on the turning and stopping!
It took a few years here before the message got across to Subaru.

Romanom,
What are your thoughts on increased wheel size rasing the centre of gravity and the shift in load it causes to the front end when braking. Not to mention the brake diameter to wheel diameter ratio. Without doing all the math wouldn't it increase the stopping distance. I see a lot of people increasing wheel size but not always considering the brakes.

Steve
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Old 05-05-2002, 07:33 PM   #11
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How much more does the BMW cost compared to the WRX?
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Old 05-05-2002, 07:34 PM   #12
romanom
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Quote:
Originally posted by DBAsteve


It took a few years here before the message got across to Subaru.

Romanom,
What are your thoughts on increased wheel size rasing the centre of gravity and the shift in load it causes to the front end when braking. Not to mention the brake diameter to wheel diameter ratio. Without doing all the math wouldn't it increase the stopping distance. I see a lot of people increasing wheel size but not always considering the brakes.

Steve
In general yes. Increasing overall diameter will effect braking distances in both added rotational inertia from the extra mass and it's increased distance from the center and the extra circumfrence.

Now what I'm talking about here is changing the overall diameter not just going from a 16" to 17" wheel with a lower profile tire. It is theoretically possible to go plus 1 and have the same rotational interia and mass..I got very close with my 17" package (I still increased it 3% though).

For a real world example, the last Ford program I worked on before leaving the dark side ( ) , a Subaru Outback type wagon with a Passat 4Motion like sedan, on the wagon the marketing people decided that it needed a large sidewall on the tire (from a 225/50 to a 225/55) for the proper SUV like look, this alone added 7 feet on the 60-0MPH stop. And since the wheel stayed the same there was no way to increase brake size!

Keeping the same overall diameter, but increasing wheel diameter and lowering tire sidewall height:

The reason from a brake stand piont to go to a larger wheel is to fit larger brakes, otherwise it makes no sense. Of course larger wheels with low profile tires help other aspects of the car, like looks and handling.
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Old 05-05-2002, 07:35 PM   #13
romanom
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Quote:
Originally posted by Mach5WRX
How much more does the BMW cost compared to the WRX?

I paid $25,000 for the WRX with all cost included,

the BMW 328i in August of 1999: $39,800!
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Old 05-05-2002, 07:38 PM   #14
romanom
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Quote:
Originally posted by Mach5WRX
How much more does the BMW cost compared to the WRX?

I paid $25,000 for the WRX with all cost included,

the BMW 328i in August of 1999: $39,800!

The base MSRP was $35,500.

The new 2001 and later 330i has 1 inch larger rotors both front and rear than my 328i, not to mention 225bhp compared to my 192bhp. Base MSRP ~$36,000
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Old 05-05-2002, 07:47 PM   #15
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[quote]Originally posted by romanom
[b]

In general yes. Increasing overall diameter will effect braking distances in both added rotational inertia from the extra mass and it's increased distance from the center and the extra circumfrence.

Now what I'm talking about here is changing the overall diameter not just going from a 16" to 17" wheel with a lower profile tire. It is theoretically possible to go plus 1 and have the same rotational interia and mass..I got very close with my 17" package (I still increased it 3% though).

I wasn't having a dig at you !!!
But it may be a good exercise to look at the affect these changes make to the braking performance. Pad fade seems to be on the increase and so does DTV from resin wipe off. Maybe the first question to ask someone with a pad fade problem is " What tires and wheels are you using ? "

Steve.
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Old 05-05-2002, 07:59 PM   #16
romanom
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[quote]Originally posted by DBAsteve
[b]
Quote:
Originally posted by romanom


In general yes. Increasing overall diameter will effect braking distances in both added rotational inertia from the extra mass and it's increased distance from the center and the extra circumfrence.

Now what I'm talking about here is changing the overall diameter not just going from a 16" to 17" wheel with a lower profile tire. It is theoretically possible to go plus 1 and have the same rotational interia and mass..I got very close with my 17" package (I still increased it 3% though).

I wasn't having a dig at you !!!
But it may be a good exercise to look at the affect these changes make to the braking performance. Pad fade seems to be on the increase and so does DTV from resin wipe off. Maybe the first question to ask someone with a pad fade problem is " What tires and wheels are you using ? "

Steve.
I understand what your trying to say, and I agree. I thought about not getting the 17" for that reason. But the WRX was purchased as a year round street car that was also fun to drive, I hope to trade in my 328i and get a M3 in the near future (don't want to drive that in the winter) . The WRX will never see heavy continious braking, I've gotten to many inventations to attend the local traffic court! I did the test mostly for the fun and out of curiousity.


That said though, the non-sport package 328i has 205/55VR16 tires as stock and there isn't any change in brakes with the sport package....and it handled the heat just fine.


As you know it's a combination of so many things, but your premise is correct and it's something people need to think about.

If I was autocrossing and had no intention of increasing my brake size I would have gotten 16X7 SSR Comps with 225 or 215 wide tires. And probably would have undersized the overall diameter, I don't use the speedo when racing. But it's a street car and I like the look!
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Old 05-05-2002, 08:38 PM   #17
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Romanom,
I see you like your beemers...
Just a bit of trivia. I recieved a pair of sample V8 BMW X5 discs a week ago. The O.E front is 355mm 14" diameter by 36mm 1.4" wide. Now thats gotta stop!
But its only a matter of time before someone asks the question.
" Have you got an upgrade ? "

Steve
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Old 05-05-2002, 08:55 PM   #18
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Quote:
Originally posted by DBAsteve
Romanom,
I see you like your beemers...
Just a bit of trivia. I recieved a pair of sample V8 BMW X5 discs a week ago. The O.E front is 355mm 14" diameter by 36mm 1.4" wide. Now thats gotta stop!
But its only a matter of time before someone asks the question.
" Have you got an upgrade ? "

Steve
I've already seen brake kits for the E46 M3...really it already brakes under 155 feet (47 meters) from 70MPH (113KPH)!


Hey I love love BMWs, but I'm also starting to love Subarus. I must admit if it wasn't for the WRX I never would have thought of a Subaru. But now that I have I'm impressed with the whole line of products. And I know that the WRX has made a lot of people look at Subaru. I have a cousin getting a Forester now. I think the Rex has really put Subaru on the map in a big way here in the States.

And Subaru seems a lot more open to it's owners than BMW...when I picked up my WRX they actually gave me an order form for tech manuals....BMW will sue you if you have possesion of one for a new car! They won't even tell you the wheel offset!
It's always, "You BMW should be taken to an authorized BMW service center" so they can charge you $200 to change the A/C filter!
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