[bsjd00]

Or is there really no difference?

[SRT]

Only slightly is my guess

[stressdoc]

I would bet that a 330 stops a weensy bit quicker, even though it is 200 lbs heavier. The magazine tests are posting some excellent stopping distances for the 330, have not seen a comparo yet. Something you guys that are doing the 'meets' need to do -- has anyone done a little dragging & braking at the E90 tea parties yet?

[akhbhaat]

No. The tires are what stop the car, not the brakes. Obviously this also means that sport package cars will outbrake the non-sport models...at least so long as they're both running factory spec tires.

Both the 325 and 330 have brakes that are far more than capable of exceeding whatever sort of traction the tires will give you. It is possible (if not likely) that the 330's larger pads and rotors experience slightly less fade under repeated use (friction load is distributed over a larger surface area), but fade should be of no issue under normal conditions on the street. The pads used in both cars are not suitable for track use, anyway.

[bsjd00]

I'm confused - why is the 330 actually heavier?

[akhbhaat]

Originally Posted by bsjd00

I'm confused - why is the 330 actually heavier?

Power seats, larger/heavier wheels and brakes, heavier transmission, etc.

[visor]

Agree with akhbhaat.

Originally Posted by stressdoc

I would bet that a 330 stops a weensy bit quicker, even though it is 200 lbs heavier. ...

It's only 100 lbs heavier, SP vs. SP.

[IDENTITY_MOTORSPORTS]

Originally Posted by akhbhaat

No. The tires are what stop the car, not the brakes. Obviously this also means that sport package cars will outbrake the non-sport models...at least so long as they're both running factory spec tires.

this is the craziest thing i have ever heard. It is defiantely a combonation of both. So I should just buy better tires and forget the brembo big brake kit? yea right. sorry if this comes off a little rude.

[visor]

Originally Posted by IDENTITY_MOTORSPORTS

this is the craziest thing i have ever heard. It is defiantely a combonation of both. So I should just buy better tires and forget the brembo big brake kit? yea right. sorry if this comes off a little rude. please carry on....

I think what he means is that the E90 brakes are already quite large (12-13 inches, IIRC), that for street use, the tires would be the limiting factor.

If you check out tirerack.com's tire testings, you'll see that on the same car/brakes (they use E46's and e90's), different tires have different braking distances.

[ChineseGuy]

Originally Posted by IDENTITY_MOTORSPORTS

this is the craziest thing i have ever heard. It is defiantely a combonation of both. So I should just buy better tires and forget the brembo big brake kit? yea right. sorry if this comes off a little rude. please carry on....

How is it crazy?

Um...i assume your tires are all worned out, no traction at all...ur BREMBO BIG BRAKES lock all your wheels, do u still think the car will stop? yea right. sorry if this comes off a lil rude too.

[IDENTITY_MOTORSPORTS]

if your comparing 2 cars with the same brakes then the tires would of course be the factor. But, i did say it is a combination of both, not that you can stop without tread. What was stated was:

Posted by akhbhaat
No. The tires are what stop the car, not the brakes

I guess i took that literally. i am sorry.

[BMW F22]

I would have to agree that tires do make a difference. If you try to stop a car with very little treads, it would take you more distance to stop the car. I recent changed the tires on my camry and it 's not only smoother, drive better, but also stops quicker as well.

[lux.sh]

Originally Posted by akhbhaat

No. The tires are what stop the car, not the brakes.

So can I take the whole brake assembly off and save some weight?
I have new tires.. so the car should stop just fine.

[akhbhaat]

Originally Posted by IDENTITY_MOTORSPORTS

this is the craziest thing i have ever heard. It is defiantely a combonation of both. So I should just buy better tires and forget the brembo big brake kit? yea right. sorry if this comes off a little rude.

Again: all the brakes do is reduce (or attempt to reduce - if your pads overheat, they'll just glaze over and rub against the rotor like ice on ice) the rotational speed of the wheel hub. It's mainly up to the tires to do the rest. Without traction, applying the brakes will just lock the wheels and the car will slide. Oh, it'll still stop, alright - more than likely after hitting a tree, a guard rail, or another car.

Modern disc brakes with multi-piston calipers are capable of applying far more stopping power than the average tire could even hope of utilizing. This is why we have ABS - the computer rapidly and continually applies and reapplies brake pressure so as to slow the car as quickly as possible without overwhelming the tires. Better (grippier) tires can increase the amount of load the tires can take before the ABS is forced to intervene. Hence, shorter stopping distances.

Obviously, there's still a good reason to have a larger brake package - much better fade properties under repeated hard use, for one. The 330's brakes (with a more suitable pad) are certainly more track worthy than the 325 brakes in stock form...but they're not worth much on the street. Of course, larger discs and such are also heavier, which increases the amount of rotational mass that the brakes themselves have to work against, and so on and so forth...it's a vicious cycle.

By the way, big brake kits are a total waste of money when used in conjunction with street tires. Far more stopping power than you'll ever be able to use. A set of OEM-sized slotted rotors and fade-resistant pads (ceramic, even) will fit the bill for street use and even moderate track use.

[akhbhaat]

Originally Posted by visor

I think what he means is that the E90 brakes are already quite large (12-13 inches, IIRC), that for street use, the tires would be the limiting factor.

If you check out tirerack.com's tire testings, you'll see that on the same car/brakes (they use E46's and e90's), different tires have different braking distances.

Exactly. I can't think of a single modern road car that doesn't have enough raw braking power to overwhelm the tires and lock the wheels.

[lux.sh]

Originally Posted by akhbhaat

By the way, big brake kits are a total waste of money when used in conjunction with street tires. Far more stopping power than you'll ever be able to use. A set of OEM-sized slotted rotors and fade-resistant pads (ceramic, even) will fit the bill for street use and even moderate track use.

You are so wrong. "experts" told me BBKs are for looks!! they look awesome!

[E90Fleet]

What some of you are forgetting is that the pads used in the 325i and 330i are the same

The 330i only has the larger discs to increase its heat capacity due to it being a heavier car

[ChineseGuy]

Originally Posted by IDENTITY_MOTORSPORTS

if your comparing 2 cars with the same brakes then the tires would of course be the factor. But, i did say it is a combination of both, not that you can stop without tread. What was stated was:

Posted by akhbhaat
No. The tires are what stop the car, not the brakes

I guess i took that literally. i am sorry.

I was just trying to be sarcastic, meant no offense.

[IDENTITY_MOTORSPORTS]

No prob, just having fun conversing

[stressdoc]

USA specs

3417 330
-3285 325
132 lbs.

Transmission, wheels, power seats, stereo, few engine parts.
I wish the sunroof was optional; that could be another significant weight savings where it really helps. Ditto for the heavy runflats. I guess I am a CSL freak at heart.

Regardless, as per E90fleet's comment, the bigger rotors enhance cooling/fade resistance; if the 330 stops quicker it would be a result of the bigger tires.

[db17k]

what are you guys it's definatly a combination of both, but better brakes do matter.

[gr8sho]

Originally Posted by db17k

what are you guys it's definatly a combination of both, but better brakes do matter.

This has been a very hotly debated topic on several car BBs I've been on. One thing to note about the 330's brakes is that by being larger, there is more rotational mass and therefore the engine needs to work harder to overcome this.
As someone astutely pointed out, the ability of the tires to grip the road surface is what makes the car stop, and since the brakes can lock the wheels with enough pressure on the pedal, you can exceed the maximum power of the brakes. Stopping the car once from 70MPH will give you a measure of the car's braking capability, but do that 10 times in a row and you might notice that the brakes start to fade (assuming you haven't boiled the brake fluid).
So, if you were to "track" your E90, I suspect the 330 should outperform the 325 from purely a braking perspective assuming both cars use the same brake pad compound because the larger brakes are able to dissipate heat better and thus are able to stop the car better during repeated hard braking.