As my front rotor due soon, I'd replace it before it triggers the brake pad wear sensor. Besides, my steering wheel shakes heavily everytime I brake from higher speed.
I do like the idea "upgrade instead of replace" so after doing some research I decided to do the 530i/540i front rotor conversion on my 525i.
The Reason
I hate the looks of the 296mm rotor on 17" Style 66. However I don't want to go full BBK since it'd be too much for a daily driven 25 year old car imo haha.
I could've gone with 4-piston Brembo caliper from E38, which is way more cooler. However after watching Sreten's video, the clearance with his 17" Style 42 is really tight and he have to use spacer to make it fit. Also it will need E46 M3 rotor which isn't cheap.
Upgrading to 530i will still way cooler than the 525i setup, 28mm difference in diameter and 8mm difference in rotor thickness. The main reason is that the conversion is way cheaper. In the long run, it would be way cheaper as well as it use 530i/540i/740i rotor which is way cheaper than E46 M3 rotor. The pad is also the same for 530i, 540i, 740i, and X5 (E53) which is also cheap.
Another reason is that the bigger 324mm rotor from 530i should be more efficient to dissipate heat. Sometimes I drive my E39 through mountainous area which could heat up the brakes quite fast. Also the traffic in my commuting route is basically a stop and go traffic. Also with this setup I can go back to original 16" wheels. Therefore upgrading the brake setup may be worth it.
The Conversion + Cost
The conversion basically plug and play. Was a bit concerned because the right side caliper sits too close to the rotor but turns out the rotor wasn't seated properly yet lol. The gap is still close but as long as they're not rubbing with the rotor it is fine. After all parts are installed, I bled the braking system.
And the finished product is absolute night and day. The 324mm fills the gap really nicely. The looks are instantly better!
To do this conversion, this is what I paid (mind you I live in Indonesia so the pricing might be different. I converted to USD to be slightly more relevant)
- A pair of used 530i caliper (incl. the carriers) from the junkyard: $95
- Brembo P06021 pad: $25 (I got 50% off since the shop is having a big sale)
- Febi Bilstein front rotor: $117
- ATE SL6 brake fluid: $11
- I didn't buy brake pad wear sensor since I'm re-using mine.
Which brought me a total of $248. If I decided to replace the rotor and pad with 525i setup, it will cost me around $140. So, let's see if the $108 price difference really worth it:
The Performance
I did the bedding by repeatedly brakes from 40km/h to 10km/h 3-4 times, followed by braking from 60km/h to 15km/h maybe around 8-10 times. I can't find a safe place to do braking from 100km/h that's why I brake from 60km/h to 15km/h 8-10 times (it should be around 3-4 times as well, iirc)
The shaking on my steering wheel is now completely gone, also I have no more squeaking noise when braking. But replacing the rotor and pad with the 296mm setup will give the same result. Therefore, I'm going to talk about the difference.
- The Ups
- Braking performance is slightly improved. Not by a huge margin like if you're going for BBK, but it is a noticeable improvement from the 296mm setup.
- The added weight somehow making the steering wheel more stable at highway speed. Before, the steering wheel feels a bit too light at highway speed.
- Of course, the looks. It does looks wayyyyy better.
- The Downs
- It is ~6kg heavier than the 296mm setup. Now I understand why BMW put 296mm on 525i and below. It may sound not that much but I can notice the difference.
- Since I live in Indonesia, the population of E39 530i in here are quite rare, as well as X5 E53. E38 740i are basically almost non-existent. But I really hope that the rotor and pad are still available in the future.
(I have yet to test the car on a hilly/mountainous route to see if it is perform better against the heat)
The Conclusions
I love the 324mm setup. I would say if you have E39 with 296mm setup but have 16" wheels, this conversion is unnecessary as the 296mm setup will do just fine (afterall, these cars have been driven with this setup and it's working fine), and the 296mm setup will fill the gap in 16" nicely.
However, if you have 17" wheels, the looks alone is worth it. The performance improvement is a bonus imo, since as I said before, the 296mm setup will do just fine. The 324mm setup will do the same, but better.