Front BMW brakes locking front wheels all the time, why...please guys can i have your advice? Options

[budman5201]

I recently bought new rear calipers, redid the front BMW brakes up front and installed HAWK race pads up front. The braking has significantly improved! YES! but now i have one dilema......The front brakes lock up EASILY and the rears never at all..........I wish i could make all them lock up in emergency situations or at least more Braking in the rear.


Did i just significantly make the front brakes better by installing new race pads and BMW brakes? Can i adjust anything with the stock rear system to get more pressure to the back so i dont lock up the front VERY EASILY???

thanks guys i appreciate your help.....

Stock 1.7 liter GOING SUBARU 2.5 200 hp N/A soon!! Trying to make everything else PERFECT before i get my third Subaru done.....The braking was lacking on my last conversion......

thanks!

[Eric_Shea]

In my 73 (RIP) I had M calipers from a 70 911 up front, and stock 914 in the rear with the T in place of the prop valve. Could this have contributed to my accident in April?

Abso-friggen-lutely.

We all use to spout the wisdom regarding the T on 911 calipers etc. That T fitting story has been prolific on 914 sites for years. For me it initially made a "lot" of sense as your standard 911 weighs in at roughly the same poundage and has no valve BUT; it all hit me when I began to understand the actual dynamics of the valve AND the dynamics of a mid-engine car in a spin:

1. The car - As we know, they are "very" controllable to that breaking point but, once they go beyond they can spin violently with little or no recovery method. Like a top with the weight in the center. The 944/968 design is better with the weight at the ends.

...it is all concentrated in the middle. Like the 944, 968 or 928, this makes for a well-balanced, neutral handling car. However, as opposed to the others, it has a very low polar moment of inertia, which has two significant effects on its handling. It tends to be susceptible to crosswinds, and on slippery surfaces it rotates extremely quickly. - Vic Elford - High Performance Porsche Hand Book - Page 55.

2. The valve - As you know now (me too over the last couple of years) the valve operates as a T basically passing fluid until it should shut itself down. So... the valve doesn't, in any way, inhibit your rear caliper activity as I once thought.

If you were on a wet road with a twisty and you came up on it fast... you went into heavy braking (normal) but your rears decided to lock? Perfect storm and you know what could be the rest of the story.

[anderssj]

...it is all concentrated in the middle. Like the 944, 968 or 928, this makes for a well-balanced, neutral handling car. However, as opposed to the others, it has a very low polar moment of inertia, which has two significant effects on its handling. It tends to be susceptible to crosswinds, and on slippery surfaces it rotates extremely quickly. - Vic Elford - High Performance Porsche Hand Book - Page 55.

Eric, thanks for posting this--it's important . . .

It's easy to forget that the 914's quick "turn-in" also means it can spin in a heart-beat. Its relatively low moment if inertia also makes it easy to over-correct and start a spin in the opposite direction (BTDT (IMG:style_emoticons/default/WTF.gif) )

Basically, the moment of inertia of an object describes how easy it is to change its angular motion about its axis of rotation. Even if a 924/944 had exactly the same mass as a 914, it would require more effort to change the 924/944's angular motion because its mass is distributed further from its axis of rotation. That also means that a 75/76 914 with the big/heavy bumpers has a slightly higher moment of inertia than an earlier car.

Food for thought I guess (IMG:style_emoticons/default/yellowsleep[1].gif)

Thanks again--and sorry for the hi-jack.