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Posted by: broomhandle Jun 18 2012, 02:09 PM

19 or 23 bore?

I have a 70 with stock brakes.

I was thinking 23 but unsure if I have to change anything.

I know 19 is a direct fit, just wondering 23.

Any thoughts?

Posted by: 6freak Jun 18 2012, 02:23 PM

why spend the money... car`s not fast enough to require more brakes..if there working proper there all you need ..JMO

Posted by: yeahmag Jun 18 2012, 02:30 PM

Stock brakes = stock MC

Posted by: SirAndy Jun 18 2012, 02:31 PM

You will *not* be happy with stock brakes and a 23mm MC.

The 19mm is the better choice over the 23mm and the stock 17mm would be even better yet.

Posted by: Eric_Shea Jun 18 2012, 02:49 PM

19. I would never put a 23 on stock brakes.

Posted by: broomhandle Jun 18 2012, 03:04 PM

23, 19 and 17 are the same price. Everybody always talks about a 19.

So then 19 vs 17?

It's only 2mm... I would think that much bigger bore would help.

Posted by: a914622 Jun 18 2012, 03:46 PM

Ya but when you talk bores and fluids half again bigger = 4 times the flow rate. So a 1.5 dia will flow 4 times the rate of a 1.0 dia. Go 2mm bigger on a 17mm and the flow rate is noticable.

so i would stay with a 19mm


jcl

Posted by: yeahmag Jun 18 2012, 03:49 PM

You are thinking about this backwards. The smaller bore makes it easier to apply the brakes at the expense of pedal travel. Going up to a 19mm bore will make the brakes "feel harder", but also makes it so you have to push harder to stop. At 23mm with stock brakes you would be hating life and having to push like a formula car to get the thing to stop.

Posted by: SirAndy Jun 18 2012, 03:50 PM

Help with what exactly?

Posted by: yeahmag Jun 18 2012, 03:51 PM

"Help" going through the first stop sign after installing it...

Posted by: mepstein Jun 18 2012, 03:52 PM

Think of a lever. The bigger mc is like having the fulcrum close to you. You move more fluid but it takes more effort. Push the fulcrum away from you and you have more travel but the effort is reduced at your end and multiplied at the far end.

Posted by: Racer Chris Jun 18 2012, 04:12 PM

I would like an 18mm M/C for stock brakes.
The 17mm has a little too much pedal travel and the 19mm has a little too much pedal effort.

Posted by: yeahmag Jun 18 2012, 04:34 PM

Did they ever make one? Reason I ask is I swear mine is marked "18" on the outside.

Posted by: euro911 Jun 18 2012, 04:42 PM

If you can get a 17mm ATE for the same price as a 19mm, I'd jump on it.

Not sure about FTE's quality yet

Posted by: Valy Jun 18 2012, 04:54 PM

17mm is perfect for the stock brakes.
The 19mm requires 25% more leg force to stop like the 17mm stops.

Posted by: mrbubblehead Jun 18 2012, 05:32 PM

its to bad there arnt rebuild kits available....

Posted by: ArtechnikA Jun 18 2012, 05:43 PM

Interesting fact - all MC's are really SAE sizes.
What we call "19mm" is really 3/4"
"17 mm" is 11/16"

And they go up and down in 1/16" imcrements.
Which is why there is no 18mm...

Posted by: markb Jun 18 2012, 05:53 PM

Posted by: yeahmag Jun 18 2012, 05:56 PM

I found another reference to an 18:

http://www.914world.com/bbs2/index.php?showtopic=33154

Posted by: broomhandle Jun 18 2012, 06:31 PM

That makes sense. The brakes feel good. The MS just leaks... Bad.

I remember awhile ago everybody was saying go 19mm and 320 brakes....

But I think a new rebuilt 17 would be just fine. It's a daily driver. But I do like really sensitive brakes.....

Posted by: broomhandle Jun 18 2012, 06:35 PM

And 19/23 were the same price.... 17's are expensive....


I was looking at this uro on eBay

230800350359


I wish I could just get a rebuild kit.....

Posted by: euro911 Jun 18 2012, 08:06 PM

I'd do a search for reviews on the URO's

17mm are expensive. I recently replaced a couple of 17's with 19's and they work fine.

Posted by: JamesM Jun 18 2012, 09:16 PM

19 works but 17 would be best for stock brakes. I have both, 17 mm on an all stock street car, and 19mm on a flared autox car with wider wheels and tires but otherwise stock braking system. Even with the fatter, sticker tires, with the 19mm master its to easy to accidently lock the brakes, You get more range to control with 17mm, that being said, I do like the feel of the 19mm. I imagine 23mm on a stock step would be total crap.

Posted by: broomhandle Jun 18 2012, 10:43 PM

Damn.... 17's are so expensive for me right now. I can't do 300.

Lame.

So 17's are more because they are not as common?

And I've been reading 19's were on the six'z

I do not want to lock up my wheels every day to work....


F what to do....


Thanks for the info guys!

Posted by: JamesM Jun 18 2012, 10:53 PM

You are not going to be locking up your wheels every day, the 19mm is useable for sure, but under aggressive breaking the 17mm is easier to control.

Autocrossing is the only time i ever lock them with the 19mm and only when i am not paying attention. If you can only afford the 19, get the 19. Having any brakes is better than having no brakes. Who knows you might even prefer the 19 to the 17. You will definitely prefer the 19 over a FAILING 17.

Posted by: broomhandle Jun 18 2012, 11:19 PM

The funny thing is it works perfect. I just have to fill it up once a week. And it's been slowly pooling by my pedals....

Sucks, I love the feel of my brakes now. Fronts were rebuilt by Eric. They stop great. I don't want to have to use more force to stop.... Sucks.

Posted by: Cap'n Krusty Jun 18 2012, 11:52 PM

Why would you EVER put yourself in a position where you had to lock up your brakes? A little situational awareness is called for in your daily driving. A 19mm master cylinder will require MORE pedal pressure, not less, and it will consequently require more effort to lock'em up.

The Cap'n

Posted by: ThePaintedMan Jun 19 2012, 06:19 AM

I have a used 17mm that didn't appear to be leaking when it was removed. I traded to a 19mm when I did the BMW conversion. PM me if interested.

Posted by: dlestep Jun 19 2012, 06:47 AM

I agree. The 17mm master cylinder generates a higher clamp force than the 19mm and the 23mm MC.

Posted by: jmill Jun 19 2012, 10:27 AM

With the same pedal effort, yes. Add more pedal effort on the 19 or 23 and you get the same clamping force. More clamping force doesn't help you once you can lock them up.

I wouldn't go with a 23mm.

Posted by: Eric_Shea Jun 19 2012, 10:32 AM

I generally always recommend 19's now:

1. It gives a slightly firmer pedal which most people like.
2. It will be more effort but, you'll get use to that in an afternoon.
3. They cost much less than the 17's

Posted by: broomhandle Jun 19 2012, 10:41 AM

23mm discussion was dead a long time ago. We are talking about 19 vs 17 and the cost of a 17mm....

I'm unemployed and live in CA. It sucks here....

Posted by: euro911 Jun 19 2012, 05:28 PM

I have a nice semi-used 19mm ATE available. I originally installed it on my '75 in 2008, but the car had been sitting until March of this year, so it actually doesn't have any mileage on it.

A couple of months ago we saw fluid leaking under the car, so I purchased a new one to replace it. Turns out it was only the supply line grommets that were damaged when we installed a new fuel pump and routing new hoses under the tank.

I purchased new grommets from Pelican and it's ready to go to a new home. I'll let it go for $150. shipped if it will help you out

PM me for details ...

Posted by: dlestep Jun 19 2012, 09:22 PM

It's a matter of displaced hydraulic volume, and distributed pounds force per inch squared.

More volume (even a tiny .080 dia change as with the 19mm) requires more pedal
pressure, still with less clamping force of the 17mm. Somewhere is an article showing
something like 1400 lbs (17mm) compared to 1150 lbs (19mm).

For control, one doesn't want to lock the wheels.

The 19mm MC demonstrates less pedal travel, hince a better pedal feel.

Above all of that, the increase in surface area (pad) and caliper piston diameter
demand greater pressure to achieve the same force. But the buy back, from
the increased surface area and the use of better friction materials doesn't
require as much pedal pressure to achieve the desired control today.

One has to change not just the MC, but the caliper and friction material as well,
to experience real gains.

I run PMB's Aluminum Brembos, Porterfield R4-S pads, 911 vented rotors with
a 19mm MC.
When I have to stop quickly, I have to be aware of what is behind me. I fear
being ass-ended because not very many street cars can stop as fast.

Posted by: broomhandle Jun 19 2012, 11:39 PM

I don't know if you guys are reading this thread. But I want a 17mm. But can not afford it. And to put a used on in, not really wanting to do that either.

Guess I'm stuck with a 19mm

Posted by: ThePaintedMan Jun 20 2012, 06:41 AM

Did you not read my post above? I have one.

Posted by: broomhandle Jun 20 2012, 10:39 AM

Yeah but taking a chance on one that maybe works.

Ill send you a PM