330 ->325xi brake swap and rear brake question

after doing some reading and coinciding nicely with a preplanned brake job, I want to do the 330->325 brake swap.
I will be doing this in the front only.

My questions are as follows

1. can I use any 330 brake setup or does it hvae to be from an 330xi

2. in the rears, I wanted to replace the rotors, are they interchangeable among 325's or does the xi use a special rotor?

thanks!

Josh

You are going to need the calipers, carriers, rotors, and pad for the fronts. You will need rear hubs from a 330 in addition to the calipers, carriers, rotors, and pads or else the parking brake won't work anymore. If you don't use or need the parking brake then you just need the same 330 components as the fronts.

330i and xi brakes are the same unlike the 325i and xi.

Oh and you will need 17in or larger wheels to accommodate the larger brakes if you don't already have them.

I'm puzzled what the benefit is? Seems like lots -o- parts and $ to gain what? Not trying to make the OP defend himself obviously he knows the bonus but as this swap is not popular or 325's aren't exactly known having a weak brake system - just wondering. I switch cars all the time driving various company cars etc. I'm always amazed just how good my brakes are compared to other systems, never considered they could be better. In other words, as a DD is there a pay-off? You track guys don't count.

Originally Posted by White_Knuckles

I'm puzzled what the benefit is? Seems like lots -o- parts and $ to gain what? Not trying to make the OP defend himself obviously he knows the bonus but as this swap is not popular or 325's aren't exactly known having a weak brake system - just wondering. I switch cars all the time driving various company cars etc. I'm always amazed just how good my brakes are compared to other systems, never considered they could be better. In other words, as a DD is there a pay-off? You track guys don't count.

No, there isn't. It's just to make them look cool. If you can lock the brakes up, you have more than enough stopping power. A larger rotor can shed heat faster but on the street, that won't matter. If you track, then go for it but if not then I wouldn't bother.

Originally Posted by White_Knuckles

I'm puzzled what the benefit is? Seems like lots -o- parts and $ to gain what? Not trying to make the OP defend himself obviously he knows the bonus but as this swap is not popular or 325's aren't exactly known having a weak brake system - just wondering. I switch cars all the time driving various company cars etc. I'm always amazed just how good my brakes are compared to other systems, never considered they could be better. In other words, as a DD is there a pay-off? You track guys don't count.

Thats a fair question, but I disagree with sam's assessment that their is no DD benefit. I only learned about this swap this morning, so based on what I have been able to ascertain, I have two schools of thought on it.

First, I want to clarify that I only plan on doing this to the front. I need to get new pads and rotors anyways, so I am only paying for new carriers and calipers. I can buy a set from NAPA (for example) for 200 for the pair, so this is only costing me a small amount of money.

Now as to the reasoning:

1. why did BMW put bigger brakes on the 330's? The car is not significantly 'sportier' (not in an xi trim anyways). Its not significantly heavier either. The only reason I can see is because it represents an 'upgrade'. Bigger is better in brakes, that shoudnt be in dispute. What is in dispute is if the 325 brakes are inadequate (they are not), but you could argue that about any number of modifications that people make to their vehicles (whats wrong with the stock clutch, oem tires, oem shifter, etc....)


that brings me to my reason:

2. I do mostly stop and go driving with the occasional rip out in the countryside. I had pretty bad brake fade the last time I did this, which is why I am doing new pads/rotors (regardless). I also am pretty hard on my brakes, when I learned to drive stick, I didnt really cotton to downshifting into stops, so I use my brakes quite a bit to stop the car, so again bigger is always better.

And my last reason, because I am pretty much dead set on turning my base level xi into a car its not. Upgraded to style 44's, gauge cluster rings, lip spoiler, etc... maybe it will get mistaken for a zhp some day

Originally Posted by SamDoe1

No, there isn't. It's just to make them look cool. If you can lock the brakes up, you have more than enough stopping power. A larger rotor can shed heat faster but on the street, that won't matter. If you track, then go for it but if not then I wouldn't bother.

Disagree. It's not because you can break the static friction of your tires that your brakes are adequate. If you modulate your brakes properly you won't lock up the wheels and stop much quicker. This practice causes a lot of energy to be transferred into heat, a place where as you mentioned, larger brakes are useful.

So given the cars are essentially the same weight (330/325 XI's), the larger front only setup would make for less fade when whipping and spurring in the twisty's as well less fade when hard braking under a panic stop. I thought ABS took over modulation under panic situations? Red, do you suggest pedal application or human modulation is applied as normal? Of course we don't generally mash the pedal on but when digging into them, it's normally progressive with slight on/off unless your performing winter techniques such as braking on ice staying out of ABS land.

Bigger sounds better if you can use it. I see guys putting on those "big brake kits" and always thought for the thousands they spend, the street pay-off was iffy?

Originally Posted by jgold47

Thats a fair question, but I disagree with sam's assessment that their is no DD benefit. I only learned about this swap this morning, so based on what I have been able to ascertain, I have two schools of thought on it.

First, I want to clarify that I only plan on doing this to the front. I need to get new pads and rotors anyways, so I am only paying for new carriers and calipers. I can buy a set from NAPA (for example) for 200 for the pair, so this is only costing me a small amount of money.

Now as to the reasoning:

1. why did BMW put bigger brakes on the 330's? The car is not significantly 'sportier' (not in an xi trim anyways). Its not significantly heavier either. The only reason I can see is because it represents an 'upgrade'. Bigger is better in brakes, that shoudnt be in dispute. What is in dispute is if the 325 brakes are inadequate (they are not), but you could argue that about any number of modifications that people make to their vehicles (whats wrong with the stock clutch, oem tires, oem shifter, etc....)


that brings me to my reason:

2. I do mostly stop and go driving with the occasional rip out in the countryside. I had pretty bad brake fade the last time I did this, which is why I am doing new pads/rotors (regardless). I also am pretty hard on my brakes, when I learned to drive stick, I didnt really cotton to downshifting into stops, so I use my brakes quite a bit to stop the car, so again bigger is always better.

And my last reason, because I am pretty much dead set on turning my base level xi into a car its not. Upgraded to style 44's, gauge cluster rings, lip spoiler, etc... maybe it will get mistaken for a zhp some day

BMWs are German cars. They get driven at their top speed in Germany. A faster car needs bigger brakes plain and simple.

Bigger brakes weigh more also. You need more motor to make the payoff worth it.

If you have or have had brake fade I would *seriously* consider changing brake fluid asap. And get better pads.

See below on this one.

Originally Posted by jgold47

Thats a fair question, but I disagree with sam's assessment that their is no DD benefit. I only learned about this swap this morning, so based on what I have been able to ascertain, I have two schools of thought on it.

First, I want to clarify that I only plan on doing this to the front. I need to get new pads and rotors anyways, so I am only paying for new carriers and calipers. I can buy a set from NAPA (for example) for 200 for the pair, so this is only costing me a small amount of money.

Now as to the reasoning:

1. why did BMW put bigger brakes on the 330's? The car is not significantly 'sportier' (not in an xi trim anyways). Its not significantly heavier either. The only reason I can see is because it represents an 'upgrade'. Bigger is better in brakes, that shoudnt be in dispute. What is in dispute is if the 325 brakes are inadequate (they are not), but you could argue that about any number of modifications that people make to their vehicles (whats wrong with the stock clutch, oem tires, oem shifter, etc....)
Yes, bigger is better and larger brakes will make a difference...but not in daily driving. It's just like putting in SS brake lines and expecting a difference. In race conditions, bigger brakes are better because they shed heat faster. Also, adding weight to the brake rotor/calipers/carriers is unsprung weight which is much worse than sprung weight. I'm not sure what the exact weight difference is but remember to multiply by two for the front and two for the rear. I could, and do, argue that a number of mods that people make to their street cars are pointless. That's why mine is 100% bone stock other than the suspension, something that does actually make a noticeable difference in daily driving. Also, the examples of upgrades that you noted are all upgrades that can and will be obvious and beneficial during daily driving.


that brings me to my reason:

2. I do mostly stop and go driving with the occasional rip out in the countryside. I had pretty bad brake fade the last time I did this, which is why I am doing new pads/rotors (regardless). I also am pretty hard on my brakes, when I learned to drive stick, I didnt really cotton to downshifting into stops, so I use my brakes quite a bit to stop the car, so again bigger is always better.
If you are experiencing fade in normal daily conditions, you need new rotors and pads bad. I think you already know that. With new rotors and pads, even the 325 ones, you won't notice fade in daily driving conditions. Within legal limits at least. Also, I think you might be interpreting brake fade for reduction in pedal pressure due to air and/or moisture in your brake lines. As Kubica said, try to change out your brake fluid for some fresh stuff and see if that helps out. I do the same thing as you, brake and not downshift unless I'm entering a turn. New brake pads/rotors are cheaper than new synchros.

And my last reason, because I am pretty much dead set on turning my base level xi into a car its not. Upgraded to style 44's, gauge cluster rings, lip spoiler, etc... maybe it will get mistaken for a zhp some day
No arguement here, the bigger brakes do look cooler in the rims.

Originally Posted by redbull 325is

Disagree. It's not because you can break the static friction of your tires that your brakes are adequate. If you modulate your brakes properly you won't lock up the wheels and stop much quicker. This practice causes a lot of energy to be transferred into heat, a place where as you mentioned, larger brakes are useful.

I won't disagree with the fact that modulating your brakes will get you a faster stop and will also cause your rotors to heat up much more. BUT how often do you make repeated panic/hard stops from high speed in rapid succession when you drive on the road? If you do it more than two or three times in a row, you are being an idiot and reckless. Also, if you can break the static friction between the tires and the road, that does mean your brakes are adequate and that your tires are then the weak link in the chain. Also, when you are modulating the brakes, you are not using the full clamping force of the brake calipers.

Originally Posted by White_Knuckles

So given the cars are essentially the same weight (330/325 XI's), the larger front only setup would make for less fade when whipping and spurring in the twisty's as well less fade when hard braking under a panic stop. I thought ABS took over modulation under panic situations? Red, do you suggest pedal application or human modulation is applied as normal? Of course we don't generally mash the pedal on but when digging into them, it's normally progressive with slight on/off unless your performing winter techniques such as braking on ice staying out of ABS land.

Bigger sounds better if you can use it. I see guys putting on those "big brake kits" and always thought for the thousands they spend, the street pay-off was iffy?

The brakes won't be any different during panic stops unless you are performing them repeatedly in rapid succession. They also won't be any different unless you are tracking the car. On the road, you should never be seeing speeds and subsequent repeated rapid deceleration that cause brake fade. If you are tracking then it's a different story. Again, when your tires lock up it'll be up to the ABS and the adhesion of your tires to the road that will make you stop better/faster unless you are experienced and aware enough to modulate the brakes yourself. Under panic situations, the ABS will take over. The average person is not aware enough to modulate the brakes while under pressure. Remember though that the main function of ABS is not to make you stop faster but to help you maintain control and to enable avoidance during stopping. IMO, most people who install big brake kits are doing it mostly for the looks.

FWIW, I don't really have any personal investment in whether or not you install the 330 brakes. It's your car and your money, I'm just laying out the facts and my opinions.

Originally Posted by Kubica

BMWs are German cars. They get driven at their top speed in Germany. A faster car needs bigger brakes plain and simple.

Bigger brakes weigh more also. You need more motor to make the payoff worth it.

If you have or have had brake fade I would *seriously* consider changing brake fluid asap. And get better pads.

If I decide to do this I will weigh both setups for comparison. I can't imagine the weight difference is that great.

I have had some serious brake fade driving in the mountains (oh **** brake fade). This was more-hey, I am not slowing as quickly as I usually do fade. I have no clue what pads I have on now, so that's a no brainer....fluid probably needs to be flushed as well. I haven't done it in the year I have had the car.

Any recommendations for pads? Did I see to stay away from ceramic??

Also, how often do you need to change your ebrake shoes? As needed or regularly scheduled...

I'd say "as needed" for installing replacement E-shoes. Unless, some moron drove with the hand-brake set for miles!

Yeah, they don't wear, just scuff 'em up. Pads are tricky, I'll say nothing as you probably would ignore old-school, dust lovers (like me).

Originally Posted by jgold47

If I decide to do this I will weigh both setups for comparison. I can't imagine the weight difference is that great.

I have had some serious brake fade driving in the mountains (oh **** brake fade). This was more-hey, I am not slowing as quickly as I usually do fade. I have no clue what pads I have on now, so that's a no brainer....fluid probably needs to be flushed as well. I haven't done it in the year I have had the car.

Any recommendations for pads? Did I see to stay away from ceramic??

Also, how often do you need to change your ebrake shoes? As needed or regularly scheduled...

If you experienced fade, you need to change the fluid. Performance Friction z-comps are my favorite. Check out bimmerworld for those. PF has brake fluid out now too. ATE superblue fluid is much cheaper though.

Originally Posted by jgold47

Any recommendations for pads? Did I see to stay away from ceramic??

Also, how often do you need to change your ebrake shoes? As needed or regularly scheduled...

I'm going to go OEM on my change. I can clean off some dust for the bite they give.

Ebrake shoes should be changed as needed. Try to adjust it first before you change them out. This reminds me that I still need to do this...

Originally Posted by SamDoe1

I'm going to go OEM on my change. I can clean off some dust for the bite they give.

Ebrake shoes should be changed as needed. Try to adjust it first before you change them out. This reminds me that I still need to do this...

Sammy- dont buy more OE pads. I'll send you a link to get the z-comps cheaper than OE. If you don't like them, I'll buy them from you. OE rotors are a good choice though.

I believe 330 brakes do tend to last longer. I got nearly 100k on my old 330i's brakes.

Originally Posted by Kubica

Sammy- dont buy more OE pads. I'll send you a link to get the z-comps cheaper than OE. If you don't like them, I'll buy them from you. OE rotors are a good choice though.

I think you already sent me that link...but send it again just to make sure I'm looking at the right one. When you sent it before, they were much more expensive than the OE ones. When I say OE, I don't mean ones from the dealer, I mean the Textar (OEM manufacturer, but you already knew that) ones from Pelican that go for ~$60 a pair for the fronts. For the rotors, I bought a full set of the OEM BMW Performance rotors front and back when they were on that huge sale last year. That offer was FAR too good to pass up on. They are currently in a box in my basement...I can just hear them pleading to go on the car...

Better pads, better rotors, better lines, and better fluid. you brakes will be much more than adequate...

I did this swap- no dramas.

I have thought about doing this upgrade, but the 330i rotors are 20 lbs each - 5 extra lbs of unsprung weight.
Unsprung wt would jump from about 75 to 80 lbs and make the 325xi feel slower.
While the 325xi can use the 330i and xi calipers on front and rear, this upgrade increases unsprung weight a lot and hurts handling in the end.

Yes, in theory a slight decrease in acceleration, but increase in stopping power and safety. Just like adding wider tires.

If you need bigger brakes, you probably already know it. Not necessary for a casually driven car. If you are glazing or burning up front pads at the track or want the extra weight transfer for autox, it's a no brainer.

There are lighter rotors available too.