Brembo F50 Piston Sizes

[Scooby]

Does anyone know the size of the Brembo pistons on the R32 GTR F50 kit?

Cheers

[djr81]

F50's are 2 x 44 & 2x40.

F40's are 2x44 & 2x38 same as the povvo pack version Nissan fitted standard.

[Scooby]

F50's are 2 x 44 & 2x40.

F40's are 2x44 & 2x38 same as the povvo pack version Nissan fitted standard.

That's what I thought but F50s come in different piston sizes.

[Roy]

F40s and F50s look the same, and are the same. Its just that the piston size is different on the leading pistons. I have never heard of the trailing pitson being anything other then 44mm

[Scooby]

F40s and F50s look the same, and are the same. Its just that the piston size is different on the leading pistons. I have never heard of the trailing pitson being anything other then 44mm

i agree the trailing piston is 44mm but there is variation in the leading piston sizes. AU and BA Falcons with the F50 kit have different piston sizes to change the pedal travel.

as djr said the F40s and Nissan Brembos are the same piston size so there should be no change in pedal travel. there's about a 10% piston area increase between the Nissan Brembos and the F50s with 40x44, which should make a noticeable difference.

Edited April 1, 2008 by Scooby

[Roy]

i agree the trailing piston is 44mm but there is variation in the leading piston sizes. AU and BA Falcons with the F50 kit have different piston sizes to change the pedal travel.

as djr said the F40s and Nissan Brembos are the same piston size so there should be no change in pedal travel. there's about a 10% piston area increase between the Nissan Brembos and the F50s with 40x44, which should make a noticeable difference.

Should ?

[djr81]

Doubt it. The volumetric (big words!) difference between the two callipers is:5550 vs 5309. ie 5%. Even less when you take into account the rears. Less still when you take into account all the other slop in the system eg fire wall deflection, pedal deflection, expanding hoses.....

[Scooby]

Doubt it. The volumetric (big words!) difference between the two callipers is:5550 vs 5309. ie 5%. Even less when you take into account the rears. Less still when you take into account all the other slop in the system eg fire wall deflection, pedal deflection, expanding hoses.....

Hi Roy, yes I reckon it should. Or are you emphasising it WOULD? Anyway it's a moot point as DJR is right, it's 5% or less difference. So much for my calcs.

DJR not sure why the rears factor into diminishing the difference though, if they stay the same? It's still an increase in volume. As for firewall flex etc it's there anyway so the only variable is the volume change.

Do either of you know where I can get a seal kit locally for less than the $400 or so I was quoted by a Brembo agent today?

Cheers

[Roy]

Hi Roy, yes I reckon it should. Or are you emphasising it WOULD? Anyway it's a moot point as DJR is right, it's 5% or less difference. So much for my calcs.

DJR not sure why the rears factor into diminishing the difference though, if they stay the same? It's still an increase in volume. As for firewall flex etc it's there anyway so the only variable is the volume change.

Do either of you know where I can get a seal kit locally for less than the $400 or so I was quoted by a Brembo agent today?

Cheers

I dont think a driver will notice an adverse effect on pedal feel. I think its a matter of getting too carried away with numbers. There is likely to be more difference in the old master cylinder and brake booster then from the change to F50s

What does the $400 include. Dust boots and pressure seals ? If its both then its not out of this world expensive. You may be able to get them for about $350, any cheaper and its because someone is robbing themselves

[djr81]

Hi Roy, yes I reckon it should. Or are you emphasising it WOULD? Anyway it's a moot point as DJR is right, it's 5% or less difference. So much for my calcs.

DJR not sure why the rears factor into diminishing the difference though, if they stay the same? It's still an increase in volume. As for firewall flex etc it's there anyway so the only variable is the volume change.

Cheers

Well because the brake pedal still needs to move the pistons in the rear clipers as well as the front. So you need to factor in the extra 2513mm per calliper.

[Scooby]

Well because the brake pedal still needs to move the pistons in the rear clipers as well as the front. So you need to factor in the extra 2513mm per calliper.

the rears aren't changing, so they remain a constant. the difference in volume is on the front only, so if it's say 5% difference in the new front set up i don't see how the rears affect that. it's still a 5% difference. the volume of the rears doesn't have a different effect on a 5% greater volume front caliper than it does on a 10% greater volume caliper.

Roy the cost of seals in the US is about $45 / caliper.

does anyone have views on ideal brake bias ratios ie front vs rear brake torque factoring in pad, disc and piston size? let's assume pad compounds are not factored in although we know that this can affect the outcome.

[Roy]

does anyone have views on ideal brake bias ratios ie front vs rear brake torque factoring in pad, disc and piston size? let's assume pad compounds are not factored in although we know that this can affect the outcome.

That is a very hard thing to answer. Have you had your car corner weighed? I suggest you throw it on and accept the fact that the first few months/track days will be exploratory until you find the ideal setup. The ratio depends a lot on suspension, ride heights, weight distribution, tyre grip, CoG ... etc etc

[Scooby]

coudn't agree more. i'm just pursuing this:

The most dramatic front-bias impacts are usually brought about by “big brake kits” which are not properly matched to the intended vehicle. Any time that a bigger front rotor is installed, there is a simultaneous need to decrease the effective clamping force of the caliper (installing smaller pistons is the easiest method) to offset the increased torque created by larger rotor effective radius. The objective is to maintain a constant amount of brake corner output (torque) for a given brake line pressure as Figure 6 illustrates. Unfortunately, too many upgrades do not take this factor into account, and those poor cars end up with both bigger rotors and larger pistons which serve to drastically shift the bias even more forward. While rock-solid stable under braking, stopping distances will go up dramatically.

from here:

http://www.stoptech.com/tech_info/wp_brake...rformance.shtml

[Roy]

Sure you can read that. But how do you explain how an R32 GTSt running std calipers spaced out for 324mm, an increase of 44mm with std rotor and caliper at the back, with the same compounds all round wants to lock up rears well before the fronts? Even with a less racey pad out back the car wants to lock up rears?

Answer is the pitch of the car under suspension, an issue because of the soft springs and too low a front ride height. So sure, technically what is being discussed above is true, but there are so many other things going on when trying to stop the car that you can get it wrong when you look at parts in isolation

[djr81]

the rears aren't changing, so they remain a constant. the difference in volume is on the front only, so if it's say 5% difference in the new front set up i don't see how the rears affect that. it's still a 5% difference. the volume of the rears doesn't have a different effect on a 5% greater volume front caliper than it does on a 10% greater volume caliper.

Roy the cost of seals in the US is about $45 / caliper.

does anyone have views on ideal brake bias ratios ie front vs rear brake torque factoring in pad, disc and piston size? let's assume pad compounds are not factored in although we know that this can affect the outcome.

No the rears aren't changing, but they cannot be ignored.

The front volume is (per side) 5300mm2 (For the sake of the argument).

The rear volume is about half that at 2500mm2 (again for the sake of the argument).

So the brake pedal has to displace 7800mm2 of piston area per side prior to any calliper being changed.

If you add 250mm2 of area to the front the brake pedal has to displace 8050mm2 of piston area.

So the difference is then something like 3% as opposed to 4% or whatever the difference is for just the front callipers.

So in terms of pedal travel it is less significant than just looking at the front callipers.

In terms of bias most manufacturers (eg AP, Endless) appear to offer callipers with smaller piston areas & bigger rotors. To keep the bias constant.

[Scooby]

Roy it's probably safe to assume that the Stoptech tests were carried out on cars that were either stock, or well set up.

djr I agree, that does seem to be the trend.

I'm going to pursue this off-line as I think it's worth it, will let you know what I find out.