Brakes, Brakes, Brakes, Experiences with 320i upgrade Options

[solex]

Hello All,

I have recently replaced all of the flexible brake lines, pads and rotors. The MC seems to be realtively new and the calipers all function. After all of this work, I am still unimpressed with the brakes on this car.

I have read the pelican article regarding the front caliper 320i upgrade. The article also suggest that the brakes in the 914-4 are not that good. No matter how hard I try I cannot lock up the fronts.

Anyone who has done this upgrade care to comment? Does it make a significant difference?

Thanks,
Dan

[914GT]

I've got the 320i brakes and replaced the proportioning valve with a 'T' fitting. It's an improvement but I'm not sure it's significant compared to stock brakes that are rebuilt and bled properly. But elimininating the prop. valve does give a more solid pedal.

[TROJANMAN]

i know there is debate on this issue, but i was told with a 19mm MC that locking up the brakes becomes an easier task than with the 17mm.

[Cap'n Krusty]

And why, pray tell, would you want to lock up your brakes? Brakes aren't working at their maximum potential if the wheels aren't turning. What you want is brakes that exert just enough force to NOT lock up the wheels at the limit of tire adhesion. Hey, maybe we could invent a system which senses individual wheel lock up, and modulates the braking pressure to that wheel to prevent it from sliding ................! We could call it "ABS"! The Cap'n

[davep]

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

And you may be doing a lot of praying if you are able to lock em up. You have nearly no car control with locked brakes.

If you really want to lock up your brakes, get really grippy pads and super hard tires. Then you'll be able to lock up at will, have lots of wheelspin on takeoff, can skid to a stop, and won't be able to corner.

[solex]

Cap'n

I was using the phrase "lock up" to convey the fact that the brakes do not seem to stop the car in what I think is a reasonable distance. The fact is, these brakes do not seem any better then the drum units on my long departed beetles.

Perhaps what I need to do is to drive another 914 and see if there is a difference. Anyone in Long Island want to lend a helping hand to determine if there is some were else I need to look (e.g. proportioning valve...)

Thanks,
Dan

[jwalters]

(IMG:http://www.914world.com/bbs2/html/emoticons/dry.gif) Capn--the other day you got pretty hot under the collar for people giving incomplete / and / or bad advice----

Solex--with a PROPERLY operating braking system you WILL be able to lock up the fronts, and with judicious leg power get the rears to lock as well. If you cannot do this, danger is awaiting you--I would not trust your brakes until you root out the problem. The stock system as delivered, coupled with the very good pad compounds available today will give incredible braking performance from your light weight teener. With all the replacements you have done it sounds as if there is still allot of air in the system--this is not good for the obvious--for the non-obvious it drastically reduces your boiling point, which coupled by air in the system will give very dangerous if not catastrophic results--

Get a friend / significant other to help you.

This is a procedure that may take several times to accomplish. Most of the air gets trapped in the proportioning valve. On top of it is the feed line. I have gotten very good results from just loosening this fitting and letting the fluid dribble out on its own accord-i.e. no pressure on the pedal. Let a good amount dribble out, protect your paint--then with it sealed back up. Have your partner pump the brakes a few times again and hold it to the floor with all their might---then starting from pass rear, bleed at least 2 times more than when air no longer escapes, repeat for driver rear, then pass front, then driver front--remember do not let the res get low on fluid!!

Be very careful with this--brakes are the most important item on the car--as I am sure you are aware..

Hopefully all your woes are from air and air alone--good luck and report back any and all findings to pass on to others--J

[jwalters]

QUOTE (davep @ May 16 2005, 11:23 AM)

(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif) And you may be doing a lot of praying if you are able to lock em up. You have nearly no car control with locked brakes. If you really want to lock up your brakes, get really grippy pads and super hard tires. Then you'll be able to lock up at will, have lots of wheelspin on takeoff, can skid to a stop, and won't be able to corner.

Dave--you know the cars do not have ABS--they should lock up under severe braking--did you purposely set up your system so as they will not lock under any circumstances?

[solex]

J,

Thanks for the reply, I have bled the brakes many times recently and the pedal always feels solid, but I will give it another try but this time include the proportioning valve as you have suggested.

Thanks,
Dan

[Brando]

QUOTE (solex @ May 16 2005, 08:25 AM)

Cap'n I was using the phrase "lock up" to convey the fact that the brakes do not seem to stop the car in what I think is a reasonable distance. The fact is, these brakes do not seem any better then the drum units on my long departed beetles. Perhaps what I need to do is to drive another 914 and see if there is a difference. Anyone in Long Island want to lend a helping hand to determine if there is some were else I need to look (e.g. proportioning valve...) Thanks, Dan

I understand what you mean... I just recently put new Zimmerman rotors on front and rear, new PBR Metal Master pads all around. These don't grip nearly as well as the old pads I had.

It does seem unsafe when the car doesn't slow down as quickly as you'd like. Maybe you should try a different brand of pads? New rotors?

[Joe Bob]

I will add my $.02, if I may....you have a 30+ year old car.....not telling what deferred maintenance has been done.

Go thu the system and inspect and or replace and rubber line. Look for sweating at joints, pin holes in solid lines where they contact another part.

COMPLETELY purge the fluid and replace with high quality fluid .... I like ATE blue...check caliper specs and use an agressive pad.

I also like speed bleeders.....

[jwalters]

QUOTE (solex @ May 16 2005, 11:30 AM)

J, Thanks for the reply, I have bled the brakes many times recently and the pedal always feels solid, but I will give it another try but this time include the proportioning valve as you have suggested. Thanks, Dan

(IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) Do not be discouraged by the number of times you may have to bleed em--it took over 3 HOURS and two gallons of fluid before I finally got mine straight----if only I bled the prop valve first--now I know--I hope it all works out for you--these things can be a real bitch---

What tire combo are you running? Type and size?? What brand of pads are you running?

[Mueller]

QUOTE (solex @ May 16 2005, 09:30 AM)

J, Thanks for the reply, I have bled the brakes many times recently and the pedal always feels solid, but I will give it another try but this time include the proportioning valve as you have suggested. Thanks, Dan

is your floorboard flexing when you press on the brakes??

if so, this area is known to get weakened due to rust and usage.....

are the pads and rotors in good shape without being glazed over?

good brand pads or did you use the cheapest no-name pad sold at the local autoparts store??

[jwalters]

(IMG:http://www.914world.com/bbs2/html/emoticons/ohmy.gif) And another thing I forgot to mention--the rear caliper venting clearances----extremely important!!! if these are not to spec it will take away some pedal power, albeit a little---make sure they are set up right...J

[jwalters]

Man, mine flexed like a cicus performer---but because the M/C I chose to use would not allow me to weld up a brace on the carrier--I welded in a 1/8th inch steel plate to the inside of the area in question--took it all out--until the rust returns that is--and I am already expecting it-- (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)

[solex]

J, Mueller,

Tires are shit but have decent tread, I have old dunlops and one toyo in the rear they are 165's. I recently replaced:

- the flexible lines with factory units from Pelican
- New Zimmerman rotors all around
- New Metal Masters pads all around
- Adjusted the venting in the rears per specs
- Power bled the system with at least 2 liters of Castrol LMA

I will definitely rebleed tonight.

Thanks guys!
Dan

[jwalters]

(IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif) Even with worn out components you should still be able to get shit tires to slide!! Sounds like it is on the path to recovery- (IMG:http://www.914world.com/bbs2/html/emoticons/beerchug.gif)

[Brando]

QUOTE (solex @ May 16 2005, 08:43 AM)

J, Mueller, Tires are shit but have decent tread, I have old dunlops and one toyo in the rear they are 165's. I recently replaced: - the flexible lines with factory units from Pelican - New Zimmerman rotors all around - New Metal Masters pads all around - Adjusted the venting in the rears per specs - Power bled the system with at least 2 liters of Castrol LMA I will definitely rebleed tonight. Thanks guys! Dan

Solex, I did the same (sans the fluid change and lines [mine are braided SS]) and experience the same thing now.

I'm thinking it just takes a couple-hundred miles for the pads to grip well?

[davep]

QUOTE (jwalters @ May 16 2005, 08:29 AM)

Dave--you know the cars do not have ABS--they should lock up under severe braking--did you purposely set up your system so as they will not lock under any circumstances?

Oh yeah, the only ABS is on my Chevy.
No, I've been upgrading my brakes since the early days. 911S on the front and 914/6 on the rear. Now I have vented rotors on the rear also. However, with brake upgrades come the tire upgrades. Basically you want the tire to have more grip than the brakes. If the brakes exceed the tires, then you get lockup and slide. Everytime I get lockup, say on gravel or sand, I tend to hit something I didn't want to hit. I do like to practice on slippery surfaces just to learn where the breakaway is.

Lets face it, these cars are all about balance. That is how I got the addiction. I pay far more attention to tires and brakes than engine and cosmetics. A ricer I am not.

[jwalters]

QUOTE (davep @ May 16 2005, 12:57 PM)

QUOTE (jwalters @ May 16 2005, 08:29 AM) Dave--you know the cars do not have ABS--they should lock up under severe braking--did you purposely set up your system so as they will not lock under any circumstances? Oh yeah, the only ABS is on my Chevy. No, I've been upgrading my brakes since the early days. 911S on the front and 914/6 on the rear. Now I have vented rotors on the rear also. However, with brake upgrades come the tire upgrades. Basically you want the tire to have more grip than the brakes. If the brakes exceed the tires, then you get lockup and slide. Everytime I get lockup, say on gravel or sand, I tend to hit something I didn't want to hit. I do like to practice on slippery surfaces just to learn where the breakaway is. Lets face it, these cars are all about balance. That is how I got the addiction. I pay far more attention to tires and brakes than engine and cosmetics. A ricer I am not.

(IMG:http://www.914world.com/bbs2/html/emoticons/wink.gif) Sounds really kool dude--hope I get to a point one day and do the same with my teener--J