Poll: Brake upgrades..what kind of ratio?, F=big/R= big or F=big/R=little or ??? Options

[Mueller]

okay...for a factory 914 /4, the front calipers (piston area wise) are 1.61 larger than the rear....(42mm and 33mm)

for early 911's (up to '84), the fronts are 1.6 larger
from '84 to '89, the fronts are only 1.3 times larger than the rears....then the ratios vary from 1.4 to 1.7 until the arrival of the 1st Twin-turbo, that car has calipers that have piston areas 2X the size of the rears !!!!!

I'm just wondering what combo people have successfully ran.....it's interesting to note that the standard Boxster front calipers if bolted to the front of a 911, the Boxster piston area is only 1.05 larger than the standard 911 fronts.....seems like a darn near equal swap, except for the bigger pads you get with the Boxster calipers (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

[bd1308]

um...stock? I'm gonna wait till my rears rust and reak off (IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif)

[SirAndy]

QUOTE (Mueller @ Feb 3 2005, 05:27 PM)

I'm just wondering what combo people have successfully ran

'84/'85 carrera on all 4 corners ... the fronts in the front and the rears in the rear ...

(IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) Andy

[d914]

944 turbo front
carrera rears

[Mueller]

QUOTE (SirAndy @ Feb 3 2005, 06:58 PM)

QUOTE (Mueller @ Feb 3 2005, 05:27 PM) I'm just wondering what combo people have successfully ran '84/'85 carrera on all 4 corners ... the fronts in the front and the rears in the rear ... (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) Andy

so you have option 4.....

i'm trying to figure out what I am going to do for rear calipers.....I've got 4 calipers that are 6% larger than the Boxster front calipers....

I was thinking that I could modify the rears so that only one piston per side was used, but I don't know if the rear calipers would ever work even with an adjustable prop. valve?

[SirAndy]

QUOTE (Mueller @ Feb 3 2005, 06:04 PM)

I don't know if the rear calipers would ever work even with an adjustable prop. valve?

don't know about the one piston thing but i can tell you that, unless you change your complete braking system, a adjusteable prop-valve is wasted money. you'll end up running it full open anyways. that's why i used a "T" instead ...

(IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif) Andy

[Eric_Shea]

S-Caliper
M-Caliper
T-Fitting

I just went off the hp rating the factory had with the 76 930 (240) and installed that system. I'm planning on my 2.5 S engine to be close to that. (220-240 range)

[JmuRiz]

Front - 4 piston Brembo monoblocks
Rear - Stock with 914/6 rotors
Replaced the prop valve with a 'T'

[bondo]

I have the second option, but I can't tell you how it works because my car is still a pile of parts. I will be using it with a 19mm master cylinder and a tee in place of the prop valve.

[don9146]

I have 964 front calipers clamping cross-drilled and slotted rotors in the front, stock calipers in the rear, a 19mm master cylinder, and the brake line "T" replacing the proportioning valve. Balance and feel are excellent with no fade on open track day events.

[fiid]

Friction is a function of normal force, not of surface area.... so it is just the piston size that matters, not the pad area. ( http://www.school-for-champions.com/scienc...ce/friction.htm )

I would be a little careful about using the 911 ratios as too much of a data point since their weight distibution is probably a little different (wrong) compared to the 914. The MR2, Elise, Europa, Esprit, X1/9, Ferarri 360 (engine is a little heavy here) might be more interesting though.....

It seems like it is possible to correcly balance everything up to and including A calipers on the front with the stock 914 rears - which is what I am doing. If I were you - I'd probably just go to M calipers....

Don't forget - the other way to increase braking is to reduce weight..... Perhaps some fibreglass decklids would help :-)

Mueller: Sorry for abrubtly ending the phone call - I'll call you back today sometime... I had to do a demo for the board.

[ArtechnikA]

'S' calipers front, widened 914.6 calipers rear.

[v82go]

Front= M (911)
Rear=stock (redrilled/5lug)
Prop. valve replaced witha "T"

[bondo]

QUOTE (fiid @ Feb 16 2005, 10:25 AM)

Friction is a function of normal force, not of surface area.... so it is just the piston size that matters, not the pad area.

I bet pad area affects heat accumulation to some degree. It also definitely affects wear rate. One thing that is certainly a factor is rotor diameter.

That page mentions that surface area comes into play when material deformation occurs. I wonder if pads deform enough? It'd be interesting to do some experiments in a real world situation.. do some repeated hard braking, then cut away half the pad area and do it again (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

[fiid]

(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif) I think you hit the nail on the head.

Pad area would effect wear rate, and I bet it has some thermal effects too - like felxing you mentioned.

If you assume that the braking force originates (on average) from the center of the pad, then a bigger pad and larger radius rotor whould also move the braking force further out, giving it a greater mechanical advantage (of course - larger tire radius would lose you this battle from the other end)....

[fiid]

felxing is the combination of felching and flexing, which happens when you get small animals caught in your brakes.

(IMG:http://www.914world.com/bbs2/html/emoticons/chairfall.gif)

[anthony]

QUOTE (Mueller @ Feb 3 2005, 06:27 PM)

okay...for a factory 914 /4, the front calipers (piston area wise) are 1.61 larger than the rear....(42mm and 33mm)

Does this ratio take into account the proportioning valve? It must change the "ratio" in the stock system. Most people, when they add 911 front brakes, remove the proportioning valve to make the rear brakes work more.

[1973914]

Boxster Monoblocks up front/Vented rotors
Carrera M (Wide) Rear/Vented rotors
T in place of rear slave cylinder

Monoblocks have light weight with minimal flex. Think of the S calipers but stronger. No prop valve (although i may add one just in case). This of course for 5 lug, but they fit under the 15's. (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

[bondo]

QUOTE (fiid @ Feb 16 2005, 11:13 AM)

(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif) I think you hit the nail on the head. Pad area would effect wear rate, and I bet it has some thermal effects too - like felxing you mentioned. If you assume that the braking force originates (on average) from the center of the pad, then a bigger pad and larger radius rotor whould also move the braking force further out, giving it a greater mechanical advantage (of course - larger tire radius would lose you this battle from the other end)....

Now that I think about it, pad area and heat MUST be very related. If friction is the same for a smaller pad (or nearly the same), the amount of heat energy must also be the same, because dynamic friction is simply the conversion of mechanical energy to heat. So that same amount of heat would be concentrated on a smaller pad area and overheating it sooner.

I guess the same thing would apply to clutches. Too bad our bellhousings are so darn small.

[ArtechnikA]

QUOTE (anthony @ Feb 16 2005, 01:17 PM)

Most people, when they add 911 front brakes, remove the proportioning valve to make the rear brakes work more.

in my case, i removed the proportioning valve because after changing the caliper piston ratios, it was no longer needed.

QUOTE

Too bad our bellhousings are so darn small.

go have a look at a Tilton or F1 clutch :-)