|
|
Mar 17, 2018 21:50:52 GMT
|
Have picked up a set of Mercedes Brembo 4 pots for the front of my daily, but not sure how much better braking there will be. Not really au fait with the calculations, anyone any insight?
Standard front brakes consist of 312mm discs, and single piston ATE 57mm floating calipers.
The brakes to replace them are 345mm discs and the calipers are from a W211 E-Class, Brembo 4 pot with 2x 44mm pistons and 2x 40mm, fixed calipers.
Master cylinder is standard but the biggest I can get without spending huge money.
Would anyone be able to give any advice?
Sam
|
|
|
|
|
mk2cossie
Club Retro Rides Member
Posts: 2,953
Club RR Member Number: 77
Member is Online
|
|
|
Rally Design used to have a helpful surface area workout on their website for wilwood brakes. That would be my first option to look at But essentially the current single piston calipers you have are worked out as the surface area of the piston x2
|
|
|
|
Darkspeed
Club Retro Rides Member
Posts: 4,697
Club RR Member Number: 39
|
|
Mar 18, 2018 10:01:04 GMT
|
Difference between the 57 and the 40/44 combination piston areas is 9% the major difference will be the dics and pad area - however if you have increased the m/c diameter then the line pressure will be lower so the braking for a given push on the pedal may not be as effective.
With such a low increase in piston area I would have left the M/C alone.
|
|
|
|
|
|
Mar 18, 2018 12:35:09 GMT
|
sounds like a brembo GT caliper, like Peugeot have used on the 406 V6 coupe (and the 2.2 hdi coupe) the other models use similar discs with also a 57mm piston and a blanket 23.8mm master cylinder on every 406.
the pad area is not significantly different, however caliper rigidity and heat dissipation is greater, so pedal feel should be more consistent.
the main difference in your setup is the extra 15mm leverage
|
|
|
|
ChasR
RR Helper
motivation
Posts: 10,194
Club RR Member Number: 170
|
|
Mar 18, 2018 22:35:43 GMT
|
I asked a thread about this regarding a different, yet strangely similar question. forum.retro-rides.org/thread/179517/exactly-influences-braking-powerAs said, the total piston area accounts for the stopping power. In a sliding single piston caliper the piston will account for two pistons; 2 of the pistons in a 4 pot system opposed their relative pistons. That formula that mk2cossie alludes to is: Applying that to your scenario Mercedes Brembos Average Piston Diameter = 42 Average Piston Radius (r) = 21 TPA = 3.142 x 21 x 21 x 4 TPA= 5541.77mm squared For what's on the car now: Piston Radius = 28.5 TPA= 3.142 x 28.5 x 28.5 x 2 TPA= 5103.52mm squared However, I've had better pedal feel myself with single piston calipers strangely, and on one car a specialist was dead right about it, even with the new owner changing everything only to have the same result. That was for my 944 S2 with braided brake lines on stock Brembos and 944 Turbo on refurbished Brembo Big Blacks from a 928 GTS. A friend with a Nissan S14a noticed a similar thing. BUT, in your case, your TPA means you should be fine with your existing master cylinder, and with the bigger pad and disc should yield better brakes with a similar/improved pedal feel.
|
|
|
|
|
|
Mar 20, 2018 11:02:20 GMT
|
Difference between the 57 and the 40/44 combination piston areas is 9% the major difference will be the dics and pad area - however if you have increased the m/c diameter then the line pressure will be lower so the braking for a given push on the pedal may not be as effective. With such a low increase in piston area I would have left the M/C alone. No, master is standard 23.8 Passat one (With ABS), the only bigger one I could get is an AUdi RS3 item at over 500 quid!
|
|
|
|
|
|
Mar 20, 2018 11:07:36 GMT
|
sounds like a brembo GT caliper, like Peugeot have used on the 406 V6 coupe (and the 2.2 hdi coupe) the other models use similar discs with also a 57mm piston and a blanket 23.8mm master cylinder on every 406. the pad area is not significantly different, however caliper rigidity and heat dissipation is greater, so pedal feel should be more consistent. the main difference in your setup is the extra 15mm leverage welshpug, yes they seem to be similar to those. Came from a W211 E320 CDI Sport, but the same would have come on an R129 500SL. Got them Uber cheap. Brake discs are massive in comparison, 312>345mm and 22mm>28mm thickness. MC Piston is the same size as tha 406, wasn’t sure how to calculate area for effectiveness
|
|
|
|
|
|
Mar 20, 2018 11:15:58 GMT
|
I asked a thread about this regarding a different, yet strangely similar question. forum.retro-rides.org/thread/179517/exactly-influences-braking-powerAs said, the total piston area accounts for the stopping power. In a sliding single piston caliper the piston will account for two pistons; 2 of the pistons in a 4 pot system opposed their relative pistons. That formula that mk2cossie alludes to is: Applying that to your scenario Mercedes Brembos Average Piston Diameter = 42 Average Piston Radius (r) = 21 TPA = 3.142 x 21 x 21 x 4 TPA= 5541.77mm squared For what's on the car now: Piston Radius = 28.5 TPA= 3.142 x 28.5 x 28.5 x 2 TPA= 5103.52mm squared However, I've had better pedal feel myself with single piston calipers strangely, and on one car a specialist was dead right about it, even with the new owner changing everything only to have the same result. That was for my 944 S2 with braided brake lines on stock Brembos and 944 Turbo on refurbished Brembo Big Blacks from a 928 GTS. A friend with a Nissan S14a noticed a similar thing. BUT, in your case, your TPA means you should be fine with your existing master cylinder, and with the bigger pad and disc should yield better brakes with a similar/improved pedal feel. I’m barking up the right tree so ChasR..>? Just checked up the pad sizes, calipers came with brand new OE Brembo items for now, pad area worked out to 8577.68mm and they are square so easy to deal with, however the VW ones are a funny shape (APEC PAD1313) and hard to calculate!
|
|
|
|
ChasR
RR Helper
motivation
Posts: 10,194
Club RR Member Number: 170
|
|
Mar 20, 2018 12:04:52 GMT
|
Simple. Break them down into squares/triangles and work out the area for each sector. Combine them once you have done that. However, this make it look like it is not quite as important as made out: www.driverstechnology.co.uk/brake-pad-area.htmBut, heat can affect these things which is where a larger brake pad can be better. As long as they are similar areas you should still see an improvement in braking. Pad life will be longer with a larger pad too as well as the pads being potentially less susceptible to fade.
|
|
Last Edit: Mar 23, 2018 11:01:01 GMT by ChasR
|
|
ChasR
RR Helper
motivation
Posts: 10,194
Club RR Member Number: 170
|
|
Mar 23, 2018 11:01:20 GMT
|
|
|
|
|
|
|
|
Cheers for that. Should be ok so. If nothing else, they look a damn sight more meaty than what's there already. on my 18" summer wheels at ET40 they clear perfectly and my 17" winter wheels they only need an 8-10mm spacer to clear at ET47.
|
|
|
|
ChasR
RR Helper
motivation
Posts: 10,194
Club RR Member Number: 170
|
|
|
I'd say you're looking at a net gain.
Don't let looks confuse you however; my Escort went from barely stopping to being a crazily strong stopper doing the opposite of you; it was down to piston size, or rather fluid dynamics, despite being on the smallest bore Ford can offer.
|
|
|
|