914 brake upgrade questions Options

[Mister T]

Hello to those of you in 914 land. This is my first post here so let me give you all a little back story. I'm 31 years old and have been wrenching for 16 years now. While I'm not a professional mechanic (tried it for 3 months and hated it), I eat sleep and breathe cars. My ride at present is a 98 1.8T Passat, AKA. Black Betty (as seen on Passatworld.com)

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Anyway, I've recently taken on the task of trying to sell my brother's 914.

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Myself
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My Girlfriend

I have some experience working on it (I tore the entire drivetrain and rear suspension out). However there are some issues that I need to work out before trying to sell it. the most pressing matter in my mind are the brakes, or lack thereof. I don't know if you can see. However the width and diameter of the tires are overwhelming the capabilities of the stock system. After some searching I think I'm going to do the 320I caliper upgrade. What I'm wondering is whether or not to keep the stock 17mm master cylinder or go to the 19mm master cylinder. There seem to be some differing opinions on the net so I would like to see if I can get some feedback from people who've tried it.

[PeeGreen 914]

Before you do anything call Eric Shea at http://www.pmbperformance.com

He is very helpful and will save you from spending money on stuff you don't want to. I could tell you more but I am confident that once you talk with Eric you will be lead down the right path and be very happy. (IMG:style_emoticons/default/beerchug.gif)

[craig downs]

(IMG:style_emoticons/default/agree.gif)
Talk to Eric he will tell you everything you need to know.


BTW (IMG:style_emoticons/default/welcome.png)

[Michael N]

Don't do the BMW 320i "upgrade" because it really isn't. I made the mistake of doing it on my wife's '74 2.0 and overheated the brakes on the backroads. It is not a great "upgrade" when you dive into a corner and realize your brakes are cooked and not going to slow you down. It is easy to overheat them with a larger pad and no cooling.

[Mister T]

Before you do anything call Eric Shea at http://www.pmbperformance.com

He is very helpful and will save you from spending money on stuff you don't want to. I could tell you more but I am confident that once you talk with Eric you will be lead down the right path and be very happy. (IMG:style_emoticons/default/beerchug.gif)

Thanks for the tip, I'll check it out.

[davep]

The main reason why the BMW 320i "upgrade" doesn't work well is that the front brakes are limited by the cooling of the brake rotor. Bigger calipers & pads might work well for a couple of times, but once the rotor is overheated, it will be worse than the stock brake. The real upgrade is to get vented rotors for the front first, then worry about better calipers.

[Cap'n Krusty]

In this case, your wheel and tire sizes are NOT "overwhelming" your brakes. What you need to do, and I'm sure Eric will tell you this, is make sure everything in your stock braking system is as it should be. What are the symptoms that cause you to believe you need to "upgrade" (a terribly misused word!) your brakes? Are the rubber brake hoses in good shape? If not, replace them with new ones. (Rubber, NOT that SS braided teflon cr*p.) Flush the system of all the old fluid, and belld out all the air. Set the venting clearance on the rear calipers to .004", as it's supposed to be. When this is done, or if you need help with technical issues, report back ..........

The Cap'n

[SirAndy]

Here's a good article on the subject:

http://www.914world.com/bbs2/index.php?showtopic=55559

(IMG:style_emoticons/default/bye1.gif) Andy

PS: (IMG:style_emoticons/default/welcome.png)

[Mister T]

What are the symptoms that cause you to believe you need to "upgrade" (a terribly misused word!) your brakes?
The Cap'n

From the aforementioned forum brake writeup:

The other time you may need a brake upgrade is when you fit flares and wider tires. In this case, what may happen is that you find you can't lock the tires with the stock brakes. In this case, you actually need to re-engineer the ratio of master cylinder to brake caliper pistons, as you need more force at the caliper for the maximum force your leg can deliver to the pedal. A smaller master cylinder, or larger caliper pistons (the total area is important, so four small pistons per caliper may be much larger than two large pistons per caliper) will be what you need. You may also need vented rotors, as you'll be generating a lot more braking force, and thus more heat, so you need bigger rotors to eliminate that heat.

[SirAndy]

What are the symptoms that cause you to believe you need to "upgrade" (a terribly misused word!) your brakes?
The Cap'n

From the aforementioned forum brake writeup:

I think what the The Cap'n is hinting at is the fact that you're not running huge sticky tires and your stock braking system might just need a overhaul.

You'd be surprised how well the stock brakes can work if maintained well ...
(IMG:style_emoticons/default/shades.gif) Andy

[PeeGreen 914]

And the heat is the part that will kill the BMW brakes. They just get way too hot because they don't have the vented rotors. The piston on the BMW is as big as a 911 caliper (I think).

[markb]

What are the symptoms that cause you to believe you need to "upgrade" (a terribly misused word!) your brakes?
The Cap'n

From the aforementioned forum brake writeup:

I think what the The Cap'n is hinting at is the fact that you're not running huge sticky tires and your stock braking system might just need a overhaul.

You'd be surprised how well the stock brakes can work if maintained well ...
(IMG:style_emoticons/default/shades.gif) Andy

(IMG:style_emoticons/default/agree.gif)

Do what the Cap'n says first & see how the brakes do. If they're not enough, go 5 lug.

[Mister T]

I think what the The Cap'n is hinting at is the fact that you're not running huge sticky tires and your stock braking system might just need a overhaul.

You'd be surprised how well the stock brakes can work if maintained well ...
(IMG:style_emoticons/default/shades.gif) Andy

I'm not sure what qualifies as big sticky tires. However the rim/tire setup is very similar in width and diameter as a Boxster.

[SirAndy]

I'm not sure what qualifies as big sticky tires. However the rim/tire setup is very similar in width and diameter as a Boxster.

Well, it sounds like you already made up your mind and you're not really asking for advice.

In that case, good luck with your BMW "upgrade" ...
(IMG:style_emoticons/default/bye1.gif) Andy

[Mister T]

I'm not sure what qualifies as big sticky tires. However the rim/tire setup is very similar in width and diameter as a Boxster.

Well, it sounds like you already made up your mind and you're not really asking for advice.

In that case, good luck with your BMW "upgrade" ...
(IMG:style_emoticons/default/bye1.gif) Andy

I don't think it's a question of not heeding advice. In fact I called Eric Shea and left him a message. The reason for my line of questioning is that the tech article stated that if the you were running a large tire setup (9in wide 255-45-17) that you may want to consider going with a larger caliper. Now, do you honestly feel that the stock brake system is up to the task of being able to provide sufficient stopping power for a wheel setup that likely has more than twice the contact patch of the OEM wheels. In short, I'm not trying to tell you that you're wrong. However, I don't feel that anyone has fully explained how the stock calipers can provide sufficient stopping power for this particular wheel setup.

[brant]

my 2 cents..

if your tires were too sticky or too wide for your brakes and overwhelming them.. then you would be overheating = boiling the fluid

is fluid boiling your symptom?

my guess is that your not stopping well but your fluid is not overheating
this would be a symptom of needing better pads and rebuilt brakes.
new rubber lines would be helpful (restricted or swollen lines often limit)

another thing that effects the 914's braking ability is the rear venting clearance. This is nearly unique to 914's in that if the rear clearance is too great you will feel like your pedal travel is too great and the overall brake performance feels weak.

don't underestimate pads. I mentioned it above, and am repeating it here. Performance pads are the single biggest improvement you can make to a propper functioning brake system. money much more well spent than a caliper upgrade!

The boxter is a much much heavier car
brakes are all about transfering momentum (increased by mass) into heat energy. If your stock brakes are overheating or boiling the fluid, then you need a rotor upgrade. If your stock brakes are just not stopping the car well or working well... then you need a brake tune up, rebuild, new lines, and PADS....

stock brakes will surprise you in comparison to modern cars when they are working correctly.

[SirAndy]

that if the you were running a large tire setup (9in wide 255-45-17) that you may want to consider going with a larger caliper.

I seriously doubt a 255 street tire will overwhelm a stock braking system that is in good working order.

I've seen plenty of 914s with stock brakes and super sticky 9" GoodYear racing slicks.

Now, if we're talking about gobs of HP, big slicks and 30 minute race track sessions, yepp, i would certainly (and have) do some serious upgrades to the brakes.

Like stated above, it's all about heat and how to get it out of the system.


Can you lock up the tires at all?
(IMG:style_emoticons/default/idea.gif) Andy

[Geezer914]

The BMW 320i does not run vented discs. Is the BMW rotor that much larger than the 914 rotor that it causes the brakes to overheat?

[PRS914-6]

I see brakes as two seperate issues. Does it:

1. Have the capacity to stop your car with reasonable pedal pressure?
2. Does it have the capacity to absorb and dissipate the heat generated for the intended use?

Simply stated if you can easily stop your car and it's casually driven it's probably fine. However, the same brake system may fail miserably on the track. You have to decide what the intended use is before throwing money at brakes. Rotors are ultimately the big "heat sink" and dissipator of heat and should be sized to meet the needs of the usage intended. Of course vented does a much better job getting rid of heat. It would seem that the average 914 can get better performance by simply switching to a more aggressive pad. If you get brake fade from overheated brakes then an upgrade in rotors would be in order. It's pretty easy to determine if an upgrade in brakes is needed.

[wbergtho]

I have the BMW 320i "upgrade" and my brakes work just fine on the street. I have a 19mm master and have had this set up on two seperate stockish HP 914's and have had nothing but good luck. I had a 540HP V-8 car that had Brembo 930 calipers and rotors on all four corners. If you are driving on the street and not endurance racing your car on the track, you will be just fine with the 320i set up. What's more, the 320i calipers are cheaper than the stock calipers. Unless you have an early car, you will have to have a small amount of material machined off the mating surface of each caliper. Go for it! You will invariably hear a zillion different opinions on this site and that's all fine & dandy...but I know for a fact that this set up worked great for two of my 90HP street cars...and I drive the crap out of the brakes.