Why/What big brake upgrade?

[thekawaii]

Okay i got 2 questions...... 1) I have Q45 front Brake calipers on my S13. Q45 brake master cylinder has two holes for brake line, and S13 needs 3 lines(2 for front, 1 for rear, later devide to 2 lines). What Brake master cylinder should i get? Will old 300zx (1986~1989) cylinder work? ( I plan to put rear one too.)

2) Will i need brake booster? I read a magazine, lack of brake booster caused bad braking. Just wondering..

3) does it really help you stop better? i mean, how? i can even lock my wheel with stock 240 brakes, do i still need bigger brakes? I don't even have ABS.

I do search all the time, but couldn't solve it myself.

[onosqv]

With a q45, you may be able to get away w/ not upgrading your brake booster - this is more of a problem going to 300zx (twice the # of pistons as q45).

The older 300zx one will work, 15/16 or something. the 17/16 will give you stiffer pedal feel.

It's mostly personal preference, but w/ the stock one, it will feel squishier and the ratio is not completely correct (sends too much pressure to the front calipers). You can check out importnut.net for the correct ratios.

The brake booster giving up seems to be a 50/50 problem - mine's gave up after install, and just another guy around my area also had his give up. I had 15/16 at the time & other guy has stock master cylinder... so it may be wise to have a spare just in case. Only costs like $30-$40 dollars anyway.

It helps you stop better because the ratio/balance (when to put most breaking in front, and how much pressure to apply) than a stock m/c. Of course, this is IF you get the correct m/c for it. I'm sure the 15/16 and 1 1/16 will both work just great w/ a full setup (q45 in front, 300zx in rear). I upgraded to a 1 1/16 master cylinder from http://www.frsport.com after my brake booster went out, already came w/ 3 fittings. You really should sign up for AIM just so you can talk to those guys, they help out a bunch.

300zx brake master cylinder

If the Q45 m/c has a 3 hole w/ a plug... you might be able to do the flare nut fitting thing like shown on importnut.net or a thread somewhere. I remember talking to elwesso & he was telling me that the Q45 m/c is actually "stronger" than the comparable 300zx one.

The point of doing this is so you DON'T lock up the wheels - but that has to do w/ a lot of different factors.

The extreme example is if you get 6 pot calipers in front, stock in back & stock m/c. You WILL lock up the front tires - and that is very very very bad.

Your case is not as extreme, so take this info as you will.

[95lstegman]

also, big brakes aren't about locking the wheels at 40mph or not. it's about being able to stop from 100mph without boiling your brake fluid. then doing it again and again and again. race track or very high-powered street car, get it? otherwise you're just wasting your money and HP (remember, your engine has to spin those bigger rotors). or you could be like many on this board who want a street-legal race car, and just knowing you could stop from 100mph repeatedly without fading is 90% of why you upgraded the brakes.

[cdlong]

With a q45, you may be able to get away w/ not upgrading your brake booster - this is more of a problem going to 300zx (twice the # of pistons as q45).

having twice the pistons doesn't matter, if the pistons in the Q45 and z32 are the same size (i think they are but i'm not sure) it will take the same ammount of fluid. there may be twice as many pistons in the z32 setup but the pistons in the q45 system move twice as far when you apply the front brakes, consuming the same amount of fluid.

[95lstegman]

i'm sure the Z32's pistons are NOT the same size as the Q45's. that would mean the Z32 will apply twice as much pressure, causing roughly twice as much friction, and would require twice as much volume from the m/c. knowing that the Q45 and Z32 master cylinders are very very similar in size, i would guess the Q45 and Z32 have about the same total piston area. the advantage to Z32's would be aluminum calipers dissipate heat better, slightly larger total piston area, less flex (hopefully) from the non-sliding caliper, and 4 pistons to more evenly distribute the pressure accross the pads.

having twice the pistons doesn't matter, if the pistons in the Q45 and z32 are the same size (i think they are but i'm not sure) it will take the same ammount of fluid. there may be twice as many pistons in the z32 setup but the pistons in the q45 system move twice as far when you apply the front brakes, consuming the same amount of fluid.

ummmm . . . NO.

[Bronze MFP]

I'm running the full z32 brake upgrade on my stock 240sx master cylinder and booster. I personally have no problems with it. The pedal feels firm (when the system isn't leaking that is ) and response and feel are fine. I'd upgrade the brakes first, then decide if you need to upgrade the MC or booster. If your MC is in good condition, chances are you'll be happy with it.

[95lstegman]

switching to the Z32 m/c is mostly recommended because with Z32 brakes and stock m/c, the brake pedal will be spongier and have more travel than stock. switching to the Z32 m/c makes it stiff again with less travel.

[cdlong]

ummmm . . . NO.

ummmm...YES.

so i was wrong about the piston size. whatever. if they were the same size, the fluid consumption would be the same and the torque would be the same given the same pad area and friction level (not the case, but for sake of argument...). got the specs by chance?

the pressure inside the caliper is the same but it is spread over twice the area. the overall force on the rotor is the same for a sliding caliper and a fixed caliper.

say the gap between the pads and the rotor is 1" on each side for both types of calipers (exagerated for simplicity). when you apply the brakes the fixed caliper will push each piston 1" until the pads hit the rotor. the piston in the sliding caliper will push out 2", 1" until the inboard pad hits the rotor, and the another 1" to push the caliper body inboard until the outer pad is pulled against the rotor.

fixed calipers do offer more even distribution of pressure. the weight, heat dissipation and stiffness are all properties of the caliper design and material, not the fact that it is fixed. BMW still uses a single piston sliding caliper in the M3. it's all in the design.

you can think you're right and look down on me because you're an ASE certified mechanic or something, but i bet only one of us worked for a brake design company.

[colies97~240sx]

Wow, this is a case of everyone is right to some extent...

Long story short, sparing technical conversation, if you are only upgrading the front brakes to 300zx or Q45 calipers your stock brake master will provide sufficient support for the calipers. You do not have to upgrade the master. If you are upgrading to 300zx brakes all the way around, you would have to upgrade the master. Upgrading the master is a lot of extra work that isn't needed, but if you want to do it, go for it.

The stock 240 master can handle front 300zx/Q45 calipers with stock 240sx rear calipers. That is how I am running my set up and that's how most people I know run it, I haven't heard of them having any problems and I haven't either.

[cdlong]

Long story short, sparing technical conversation, if you are only upgrading the front brakes to 300zx or Q45 calipers your stock brake master will provide sufficient support for the calipers. You do not have to upgrade the master. If you are upgrading to 300zx brakes all the way around, you would have to upgrade the master. Upgrading the master is a lot of extra work that isn't needed, but if you want to do it, go for it.

The stock 240 master can handle front 300zx/Q45 calipers with stock 240sx rear calipers. That is how I am running my set up and that's how most people I know run it, I haven't heard of them having any problems and I haven't either.

the s14 and z32 rear calipers do have the same size piston, just different sized rotors, so upgrading the rear wouldn't make the pedal any mushier.

[colies97~240sx]

The piston size on the rears might be the same but the z32 rear caliper has one more piston than the 240 rear caliper does. The 240 rear caliper is single piston and the z32 rear caliper is 2 piston. I'm sure having two extra pistons in the rear makes some kind of difference in the ammount of pressure needed from the master but I have no numbers on that. Anyway, that's not here nor there. Here is a great page with LOTS of info about the 300zx upgrade: http://importnut.net/300zxbrakeswap.htm

I also found a thread from a few months back... Interesting read zerothread?id=107864

[nchopp]

Nicole's right - check that 300zx article, got some great info.

[95lstegman]

in reference to cdlong, i said "NO" mostly because with the assumption that the pistons are the same size, only twice in number, it would be a crackpot situation to begin with. that assumption right there just makes 0 sense. you work for a brake company, so why would you think that one car would have twice the piston area when the two brakes are supposed to be fairly equal in power?

and i don't look down on anyone who is not ASE certified. i know lots of ASE certified mechanics who are stupid and lots of uncertified people who could just as easily pass several ASE tests if they wanted to. your statement just didn't make sense to me as an engineer.

[nopaintsls]

Nicole's right - check that 300zx article, got some great info.

I agree!!! Great info!

[cdlong]

did anyone actually read what i posted?

[95lstegman]

did anyone actually read what i posted?

yes, all of them. and did you mean the 300ZX and the S14 have the same total rear piston area, or actually the same size pistons? the 300ZX has two pistons in each rear caliper PLUS the larger rotor.

[cdlong]

both have a 38.1mm diameter piston in the rear.

[95lstegman]

but the 300ZX has two of them, for double the piston area, hence funky braking bias on a proportioning valve designed for 300ZX operating 240SX rears or vice versa. now, this may not matter much since the rears probably get much less fluid anyways.

[cdlong]

but the 300ZX has two of them, for double the piston area, hence funky braking bias on a proportioning valve designed for 300ZX operating 240SX rears or vice versa. now, this may not matter much since the rears probably get much less fluid anyways.

forget it, i quit.

[95lstegman]

on a side note, how do you like your helical ATB? i just noticed you had one. and where did you get it and for how much?