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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Suspension | Brakes | Chassis > will lower weight brake rotor improve the ride?



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      07-27-2012, 09:18 AM   #1
n55PR
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will lower weight brake rotor improve the ride?

Roads a really crappy were I live. I know that moving from RFT to Miro 18" with Michelin PSS tires improved the ride quite a bit, partly because of the weight reduction. I also changed OEM shocks for Koni FSD and the ride got noticeably better.

I am considering replacing the stock brake rotors on my e90 for lighter 2 piece floating front rotors.

I constantly drive over rought asphalt, concrete roads with uneven joints, recessed manholes, badly patched roads, etc. Ocassionaly I get lucky and find a section fo smooth road surface

Will the reduction 3-4 lbs of unsprung weight from the brake rotors make a difference in the way the car rides in harsh roads?

Last edited by n55PR; 07-27-2012 at 12:29 PM.
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      07-27-2012, 10:44 AM   #2
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Quote:
Originally Posted by Antonio Llona View Post
Roads a really crappy were I live. I know that moving from RFT to Miro 18" with Michelin PSS tires and improved the ride quite a bit, partly because of the weight reduction. I also changed OEM shocks for Koni FSD and the ride got noticeably better.

I am considering replacing the stock brake rotors on my e90 for lighter 2 piece floating front rotors.

I constantly drive over rought asphalt, concrete roads with uneven joints, recessed manholes, badly patched roads, etc. Ocassionaly I get lucky and find a section fo smooth road surface

Will the reduction 3-4 lbs of unsprung weight from the brake rotors make a difference in the way the car rides in harsh roads?
No.

You may even compromise braking performance if you don't get quality rotors. It is not worth it.

If you want to minimize ride harshness you need to take a look at your suspension. You can also downsize your wheels to 17" and get meatier tires.

Why did you get M-sport if you drive on crappy roads and want a comfy ride? It sounds like you need an X3.
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      07-27-2012, 11:12 AM   #3
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touche!

Got a good deal on the M-Sport, and I do go to the track a few times a year. I kept my Nissan daily beater SUV, but still looking for minor upgrades to improve ride quality on the 335.

want to hear feedback on shaving 3 pounds of unsprung weight in each wheel....I guess ride quality should not be an issue in the "backcountry"
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      07-27-2012, 11:57 AM   #4
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Assuming you don't compromise the integrity of any part, reducing unsprung weight is always good.

Going to rotors with aluminum hats like the Z4 rotor is good. BBK with lighter calipers are good.

How much do you want to spend is the question???
Lighter is better but how light is light enough?
I don't know.
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      07-27-2012, 12:11 PM   #5
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thanks

I was considering the Z4 rotors, good bang for the $ in my view....or RB 2 piece rotors.......but will I notice a any improvement in the ride quality?
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      07-27-2012, 12:14 PM   #6
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Quote:
Originally Posted by Antonio Llona View Post
touche!

Got a good deal on the M-Sport, and I do go to the track a few times a year. I kept my Nissan daily beater SUV, but still looking for minor upgrades to improve ride quality on the 335.

want to hear feedback on shaving 3 pounds of unsprung weight in each wheel....I guess ride quality should not be an issue in the "backcountry"

chill out bud

You got a nice machine!

3 lbs will not make any difference. Your question is related to chasis' characteristics to absorb and distribute road surface impacts. This is a complex formula with multiple variables!

Decrease in unsprung weight will improve handling, fuel consumption, braking etc...but not damping. You need to decrease weight at least 10lbs per corner to feel the handling/braking difference.

I would put those funds to better use. Most likely you would need to change dampers/springs to improve damping on rough surface. You could look into getting softer tires first and have a separate set of wheels for track use. This could be your best value option. Hope this helps!
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      07-27-2012, 03:12 PM   #7
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I put the RB 2 piece rotors on my 325. No change in ride quality at all.
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      07-27-2012, 07:31 PM   #8
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Thanks for the feedback!
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      07-28-2012, 03:29 PM   #9
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At 3-4 lbs per corner there will be a difference, but is it likely not a difference an average driver can feel on street cars with rubber bushings and soft spring rates. Any unsprung wight removed is a good thing and your springs and struts/shocks will thank you for it as their job of controling the moving masses just got easier. I would say, in my experience, most of us should be able to feel a ~10 lb of unsprung weight reduction per corner, vehicle will ride better and handle bumps easier.

A good test would be to install wheels and tires that are 10 lbs lighter per corner and go for a spin, borrow a buddy's if you have to!
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      07-28-2012, 09:27 PM   #10
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Good suggestion Harold,
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      07-28-2012, 10:15 PM   #11
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Quote:
Originally Posted by Sleepy330i View Post
Decrease in unsprung weight will improve handling, fuel consumption, braking etc...but not damping. You need to decrease weight at least 10lbs per corner to feel the handling/braking difference.
Now we're movin'. Yup, will have effect. Significant but nope, prob not enough for your concern, not near.

OP, you've sport suspension, yes? Can't expect less than firm....

Try M arms, M bushings; M sways; camber plates. Hot damn she gonna ride good!
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