More pistons or larger pad?

More pistons or larger pad?

Author
Discussion

TheAngryDog

Original Poster:

12,634 posts

224 months

Sunday 8th May 2022
quotequote all
I know it is accepted that a larger pad area is better for braking, but what about a larger pad in a single piston caliper versus a smaller pad in a 4 piston caliper, same size brake discs. Which is better?

GreenV8S

30,862 posts

299 months

Monday 9th May 2022
quotequote all
They've both got pros and cons which will matter more or less in different situations so you can't simply say either is better than the other.

Edited by GreenV8S on Monday 9th May 16:46

Dave Brand

938 posts

283 months

Monday 9th May 2022
quotequote all
Within practical limits pad size is irrelevant to braking effort.

Brake force is the product of clamping force (derived from piston area & system pressure), coefficient of friction & mean radius of the contact area.




Gary C

13,786 posts

194 months

Monday 9th May 2022
quotequote all
If the larger pad is too large for the single piston, then the smaller pad in the multipiston caliper in theory could be better, and vice versa.

but the simple premise is missing so much detail as to be essentially useless,

TheAngryDog

Original Poster:

12,634 posts

224 months

Monday 9th May 2022
quotequote all
Thanks for your replies.

Maybe a bit more info?

Single piston calipers are E60 M5, 374mm disk.
4 piston calipers are G11 7 series, 374mm disk.

E60 M5 pad size - H 79.2mm W 193.2mm.
G11 pad size - H 79.2mm W 124.7mm.

Not sure if that helps?

Gary C

13,786 posts

194 months

Monday 9th May 2022
quotequote all
My personal preference would always to go with opposed piston callipers rather than single piston sliding callipers as they tend to have more even brake wear.

But the M5 system will have been sized to work with a car likely to put more demands on the brakes and its pad length looks like it has been considerably increased spreading the same braking effort over a much larger pad area so I would go for that one.

Your master cylinder would need to be sized to match either calliper set of course.

CrutyRammers

13,735 posts

213 months

Monday 9th May 2022
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And of course, larger pads aren't always better. What's great on the track may never get warm enough on the road, so ends up being worse all the time, despite being more "race car".

GreenV8S

30,862 posts

299 months

Monday 9th May 2022
quotequote all
TheAngryDog said:
Thanks for your replies.

Maybe a bit more info?

Single piston calipers are E60 M5, 374mm disk.
4 piston calipers are G11 7 series, 374mm disk.

E60 M5 pad size - H 79.2mm W 193.2mm.
G11 pad size - H 79.2mm W 124.7mm.

Not sure if that helps?
Are you planning to change the brakes on some vehicle? What problem are you trying to solve?

TheAngryDog

Original Poster:

12,634 posts

224 months

Monday 9th May 2022
quotequote all
GreenV8S said:
Are you planning to change the brakes on some vehicle? What problem are you trying to solve?
Yes, I am planning to add 180bhp to my M5 and the standard brakes are woeful at the best of times.

The g12 374mm calipers bolt straight on and I know someone who runs them and has no issues, my only concern was the pad area that is in contact with the disk.

CarCrazyDad

4,280 posts

50 months

Monday 9th May 2022
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Any time I've seen people upgrading their brakes they always put a multi piston setup on.

I remember older BMWs (the E60 sort of generation) having rubbish brakes.

So I'd bet the newer 4 Piston calipers would be much better, especially if they are a bolt on.

GreenV8S

30,862 posts

299 months

Monday 9th May 2022
quotequote all
TheAngryDog said:
Yes, I am planning to add 180bhp to my M5 and the standard brakes are woeful at the best of times.
Woeful how? Are you overheating them, or suffering poor pedal feel, or excessive pad wear, or what?

Smint

2,362 posts

50 months

Tuesday 10th May 2022
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I'm also in the camp of preferring opposed piston calipers due to the design not requiring the calipers to slide as wear occurs.

It seems odd that something like an M5 doesn't have far more braking potential designed in so it can cope with whatever is asked of it.

Have you gone right through the existing brakes replacing any discs showing any sort of wear ridge, plus the usual servicing of the calipers themselves making sure all is working well, it's surprising i find how even a moderate wear ridge can mean more free travel of the brake pedal before contact is made solidly, ever notice how once you have new discs and pads all round how much less pedal movement is required and far better bite once contact is made.

The trouble with fitting much better front brakes, if they are indeed better, is that you really need to do something about bringing the performance of the rear brakes up by the same percentage, OK the ABS etc sorts out any premature front locking etc, but you ideally want correctly balanced brakes all round.
Before you go down this road it might be worth swapping out any pads that are getting worn (especially if they are OE which tend to be hard if my experience of German cars is anything to go by) and servicing the brakes generally and see what the score is then.
My experience of 4 piston calipers (admittedly not on a flying machine like yours), especially with a pressurised rather than normal vaccum servo assisted system, is that the brakes can be too sharp.