firming up the brake pedal

[Hypr5]

Hey guys,

It is my understanding that the e34 540 has a stronger braking system than the e34 525 and 535.

Would swapping brake boosters with a 540 give me a better / firmer pedal feel? Would it be a direct bolt on?

The brakes feel plenty strong, I just don't like how much I have to push them down since I've had the 17" wheels installed. Much less pedal travel with the stock rims!

Thanks :)

[BigKriss]

id say if it's the stock brakes then don't worry. Checking the on-line ETK, the master clyinder out of the 540i is different than the 525i. but i don't know how easily upgradable, what pedal feel differences you get andand if it's worth it.

regards

kristian

[shogun]

I have to push them down since I've had the 17" wheels installed. Much less pedal travel with the stock rims!

That I do not understand. The brake system has no relation to the rims directly and the system is an enclosed system.
So if you changed only the rims and did not touch the brakes/calipers etc., then all should be the same.
Did you check the brake oil level?
Did you bleed the system?

[Hypr5]

It's the whole thing with rotational mass. The same reason the car accelerates quite a bit slower with the rims. Since they are heavier than stock, they take more to start and stop.

I was super confused when I first got my rims and experienced weaker feeling brakes and slower acceleration. When I asked on various forums that was the answer I got, but in much more detail.

[Tiger]

Start with flushing old brake fluid with new Valvoline Syhthetic Dot 4 brake fluid

[Hypr5]

Start with flushing old brake fluid with new Valvoline Syhthetic Dot 4 brake fluid

I did a fluid flush although another wasn't due yet, it didn't help me any. Like I said, it's nothing with the condition of the brakes. When I put the 15s back on, the brakes go right back to their old feeling. Its just the added weight of these crazy 17s.

[632 Regal]

You will notice a bigger difference if you throw a bowling ball in the trunk.


Its just the added weight of these crazy 17s.

[Hypr5]

You will notice a bigger difference if you throw a bowling ball in the trunk.

If you were close by I would love for you to come drive my car with the different rims. In all my cars, acceleration and braking power were lost when larger rims were added. I'm sure I'm not the only one who has experienced this.

Heres my thread when I first got the wheels...
http://bimmerforums.com/forum/showthread.php?t=209261&highlight=wheels

[bahnstormer]

i can attest to 17's hurting breaking performance
even with my pagid sport pads it feels like my 90535ia
with 16's stops shorter....
but i do need to bleed my system, so we'll see

[Blitzkrieg Bob]

The larger diameter wheels impact both the low end acceleration and the braking.

The larger wheels act much the same way as changing the final drive to a lower ratio, reducing some of the low end, but you’ll get it back with better mid to high end.

Brakes feel weaker also because of the larger diameter. Just think of the force required to break free a frozen nut with a short bar verses a longer one. Thus the larger wheels require more force from the brakes to stop the car.

[bahnstormer]

basic physics =]

but the line



The larger wheels act much the same way as changing the final drive to a lower ratio,


is only true if u change the overall diameter...usually u get bigger wheels, thinner tire (lower aspect ration) to maintain the overall diameter

[grave77]

I think overcoming the rims change u need to install the 850i front disks and caliper system or the M5 ones, I think most of the guys here will agree about this point. M5 disks or 850 are larger and thicker to it will be like braking farther than before and can adapt to the bigger wheels. 540 brakes are different from the 535i and 525i especially the rear disks ( they r vented type of disks ) check at Bruno’s http://www.bmwe34.net brake upgrades.