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Posted by: budman5201 Nov 13 2008, 09:07 PM

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!




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Posted by: Mike Gilbert Nov 13 2008, 10:06 PM

i would try adjusting the rear brake proportional valve(see your repair manual) or just remove it completely with an inline tee....about $15.00 but be carefull on wet roads untill you get it right

Posted by: Eric_Shea Nov 13 2008, 10:26 PM

Sorry Mike, the "remove the proportioning valve" thing is really bad advice that could cost someone their life. The rear brakes lock up on a mountain ridge in the rain and his car can go spinning off the edge like a top... real things can go real wrong, real fast.

The valve is a rear caliper saftey shut-off valve, made to disengage the rear calipers in a panic stop. I wish that brake "T" thing would go away.

Yes Budman, you significantly goofed up your brake bias. You now have 40% more pad material upfront "and" you have Hawk race pads up front (but not on the rear?).

Mike had it right in the first part. You'll want to adjust your shut-off valve but, not before you match the pads in the rear.

If you've yet to adjust your venting clearance your rears may not be working at all.

Sorry Budman... I see this as a problem all around. This is why I don't recommend the BMW calipers as an "upgrade".

The best upgrade for your situation would be to get M-Calipers and vented rotors. This will give you the same pad size you upgraded to now but the "MUCH NEEDED" venting to cool the rotor. Your new calipers will add heat to your solid rotors. You may be able to get by with an AJ Racing venting kit.

You won't want to hear it and, I've said it so many times that I'm a broken record but; my advice is to put the stock fronts back on and get the awesome Hawk pads all around. You will have a MUCH better matched and biased brake system and it will still stop like crazy.

Posted by: ConeDodger Nov 13 2008, 10:38 PM

As much as anyone would hate to admit it , I have to agree with Eric on this... I think anytime you hear yourself about to say the word "upgrade" you should ask yourself if you think you are smarter than a Porsche engineer. In some cases new technology has come along but this is not an upgrade. It would be much better to get the heat out of the rotor than a bigger clamper... Venting - Gud! Cooling - Gud! Better pads - Gud! Bigger calipers without the other three - Not Gud!

Posted by: markb Nov 13 2008, 10:43 PM

Listen to Eric, he knows what he's talking about.

Posted by: jaxdream Nov 13 2008, 11:12 PM

Hi , I was wondering if any of you more experienced guys have tryed using the " proportioning " valve from the 944 ( turbo ?? ) setup which was mounted on the master cylinder BEFORE the line or is the thing I am referencing something else entirely??? I've read all about the pitfalls of the Tee fiting , heck I even got some with the same ideaology as others in the replacing with part , haven't done it yet , probably won't as I understand more of what the 914 prop. valve really does , slick as hell those Germans, looking to do 911 M rear , maybe A front or if I get the courage up to refurb the S set I have , like I stated just curious if the 944 part was a possibility .

Jack

Posted by: budman5201 Nov 13 2008, 11:32 PM

okay so....get hawk pads for the rear, then adjust rear proportioning valve? i love my brakes, just want them a little more in rear. i havent bought hawk pads for the rear yet, but when i do how many turns would i have to turn incrementally each time to slowly get to where i want to in the rear brakes. I turned a half turn then 3/4 turn OUT and still lock the fronts.......guess i am still WAY over biased in the front since i have correct venting (checked perfect) with stock cheap pads in the rear......


i dont do any racing, or plan on it. Just some spirted driving. Mainly looking for emergency stopping power only when i need it. I dont overwork my brakes on a constant basis, just LOVE knowing that they are perfect when i need them.......

This is my STARBUCKS run car or short trip car...no high speed canyon driving....

And wow, i never knew the difference HAWKS pads can make....amazing!

Posted by: budman5201 Nov 13 2008, 11:57 PM

just bought rs-4 s for the rear .....lets see how much better they will do than stock!

Posted by: Dr. Roger Nov 14 2008, 01:06 AM

blue, black, or orange?

Posted by: Brett W Nov 14 2008, 08:22 AM

Toss the stock rear calipers and put the stock front calipers on the rear. Then add the T. That setup worked really well with PBR metal master pads all the way around. The fronts would lock up nicely and the rears would lock up shortly after that. Very controllable and predictable. What master are you running?

Posted by: Cap'n Krusty Nov 14 2008, 09:43 AM

But then you have no hand brake, which is not only illegal, but many would call it dumb. The Cap'n

Posted by: Root_Werks Nov 14 2008, 09:43 AM

This is some good reading. I need to go through my brakes (All stock) and this has given me some good tips on what to not even bother with and a couple of good things to do.

Posted by: Eric_Shea Nov 14 2008, 10:24 AM

Couple things in there I would call dumb... especially for a Starbucks car. Sorry Brett.

* Fronts in the back - now you have a 43mm piston where a 33 used to be. Porsche didn't do this until 1984 with the 3.2 Carerra and they installed a P-valve in the 911 for the first time to compensate for this. 911 track guys have complained of squirrely handling when attempting to remove this as well. This is a narrow bodied, solid rotor street car.

* T Fitting - As explained. Saftey feature that prevents the rears from locking. Your statement that the "rears would lock up shortly after that" should scare the living hell out of anyone reading it. If the rears lock in any angle off dead center in a 914 you risk spinning like a top in a mid-engine car.

* Metal Masters - Those are the worst pads I know of. No noise, no dust, no stop.

Since many have made this "upgrade" (cause I guess Pelican isn't about to take that stupid article down anytime soon), I'll offer my recommendations of what I would do if I inherited this misbalanced setup:

1. Start looking for a nice 911T front strut solution and start saving lots of money for a proper rear solution.

**now that I got that outta the way**
2. Ensure that my rear calipers are working properly. Not just the venting clearance, make sure they're operating as many have stuck pistons etc.
3. Get the same pads all around.
4. Make sure the venting clearance is set to .004" not .008"
5. Get a 19mm Master Cylinder. Don't get the Chinese copies just yet because I hear there are problems still.
6. Get a cooling kit from AJ Racing/Alan Johnson Porsche. Very simple and very effective.
7. Finally - if you determine that your rear shut-off valve is coming on too early and shutting down your rears I would then attempt to adjust it.

In Budman's situation I doubt that's the case. I think he'll be in a different place once he gets the proper pads on the back and has them vented and bedded in.

I like the thread because it spells out a LOT of things:

1. BMW Calipers have 40% more pad area and will heat up your solid rotors and cause a mis-bias in the rear. This is not as crucial as it seems in this thread because Budman has good pads up front and old glazed bad pads in the back. Which leads me to my next reason I like this thread...

2. If you "really" want to upgrade your 914 brakes, GET REALLY AWESOME PADS... like our Buddy Budman did. This really goes to show how an awesome pad will make your car stand on it's nose. If you think $100 is too much to pay for pads, especially when you have $25.00 pads waved under your nose all day; think again.

Again gang, our 914's can lock up their brakes again and again and again with little or no fade. That being the case, you don't have a caliper problem. If you're not getting the braking performance you think you should be getting, check your pads and your tires.

Posted by: Solo914 Nov 14 2008, 10:51 AM

Eric,
Since we are on the topic, and you have recommended the exact solution I have but I am still having problems maybe you can help.

I have rebuilt front calipers from you, rears that I have tested and seem to be in good working condition(adjusted), a new 19mm Master Cylinder, SS brake lines and Portfield R4S pads and I still can't lock em up. I have autocrossed and roadraced(specmiata) so I am familiar with brakes and typical bedding procedures but I have tried almost everything, checking for pad glaze, readjusting the rears, standard rebleed then tried bleeding with a vacuum bleeder etc. Could it be the proportioning valve? Could I not have bench bleed the new master cylinder well enough? I have the whole brake system apart right now(5lug swap, redrilled rotors and hubs) so I would like to get this taken care of. Any thoughts.

Kyle

Posted by: Eric_Shea Nov 14 2008, 11:02 AM

I want to clarify this comment.

The rear valve is not a brake bias valve. It is a saftey shut-off valve. You're generally not going to turn it in or out to get more rear brakes. It will simply shut them off sooner or later.

In Chris' case he'll need to get real pads in the back before even attempting this.

Also, Chris, you mentioned the venting was perfect. Keep in mind most manuals are wrong at .008". Set the venting clearance to .004" on your new pads.

Hope that helps.

Posted by: Eric_Shea Nov 14 2008, 11:13 AM

Kyle,

Do you have a firm pedal issue? If so I would look to the shut-off valve and measures to make sure air is out of it.

Regarding the locking - Dave Sprinkle had this same problem and his pads weren't bedded in yet.

For his street car I recommended the Ceramic pads which he eventually thought were "good" (once they bedded) but not great. He ended up not liking them because they were very dusty. I have the same situation on my wife's Mercedes wagon. I "really" liked the ceramics but they are dusty. I think they're the best in-expensive pad solution at around $35.00

Back on target, you should have great pads, I would be concerned that they've yet to bed in as R4-S's are one of the best pads out there. The only other person I heard of with a similar problem was Dave and he reported back as mentioned above.

Regarding the bench bleed and the pedal. You mention bleeding so I mention pedal. I don't think the master cylinder would be an issue. I have a theory on 914 brake bleeding that I want to look into this weekend. If I'm correct and I can come up with a solution this could solve the spongey pedal thing. It involves the shut-off valve.

Work on getting the rears bled and bed in the pads and you should be good to go.

Posted by: Solo914 Nov 14 2008, 11:27 AM

Eric,
I would say that I have a firmer pedal than when I had the old master cylinder and rubber brake lines. I think what it is that I press harder and harder to try to get them lock up and the floor is flexing So that may be the little bit of spongy feel I am getting. So, maybe I should go with one of those mastercylinder reinforcement kits. Also, seeing as I am going to bed these in again, should i do anything to the pads or rotors(hit em with sand paper etc?).

Kyle

Posted by: horizontally-opposed Nov 14 2008, 11:28 AM

Gee, sure am glad I never got around to taking THIS clown's advice...

pete

Posted by: Eric_Shea Nov 14 2008, 11:36 AM

Yup... that was me.

I knew someone was going to dredge up one of those old posts... had to be a pickup truck driving Porsche hat wearing editor type. I used to recommend it but that was before I tore into a couple of them and found out the real answer.

Do as I do... not as I once said!

The reason I used to recommend it was because the 911 never had it. I like engineering "systems" based on what Porsche had offered.

After looking into the feature and understanding the spin dynamics from Mr. Elford's book, I have REALLY become an advocate for keeping the rear shut-off valve.

The main thing I came to understand is, the valve won't be any different from a T. It does not restrict the flow to the rears until it shuts them down.

So, yup... over the years I've learned and now I'm trying to help others learn from my mistakes. (where's my merit badge damnit?)

Posted by: Eric_Shea Nov 14 2008, 11:39 AM

I just ordered one from Uncle Chris Foley. I like his design.

Check the pads, if they seem glazed then you might want to dress them. If not, have at it.

Posted by: horizontally-opposed Nov 14 2008, 11:40 AM

Blah, blah, blah....

Zing-zing-zingahed!

pete

Posted by: Eric_Shea Nov 14 2008, 11:43 AM

Go write something...

Posted by: davesprinkle Nov 14 2008, 11:59 AM

I'm gonna weigh in here with my brake experience. I recently went through my entire braking system -- rebuilt all 4 calipers, new 19mm master cylinder, new lines, new rotors, new pads. Post-rebuild, the braking sucked -- soft pedal and poor decceleration. I'll spare you the interminable details, but the end result was this:
A : You must ensure that all the air is out of your system. This will be less a problem when you are simply replacing the fluid, but if you've evacuated the system of hydraulic fluid (as would be the case if you've rebuilt the caliper, or replaced the mc), you're going to struggle to get all the air out. Conventional wisdom is that the air predominantly gets hung up in the proportioning valve. This may be true, but you shouldn't disregard your front calipers. I recently rebled my system and got air out of the FRONT, not the rear. Bleed, bleed, bleed. Use the McMark long-tube method so you can keep your wife out of the garage and save your marriage. Drive, bleed, drive, bleed. PITA.
B : You must ensure that your new pads are bedded into the rotors. This has a big impact on braking effectiveness and the bedding might not happen readily if you're just cruising around town. Find an empty straight road. Get up to highway speed and then stop as aggressively as you can without locking the wheels. Do this over and over. At the end of this exercise, I could smell my brake pads, but damn they worked better.
C : Pad choice is a big deal. Refer to Eric's recommendations. I'm currently running the PBR organics. I'm pleased. Low dust, good stopping performance.

Posted by: budman5201 Nov 14 2008, 03:18 PM

OKay guys I will ring back into here next week when my rear pads are in and i put 100 miles on them......Proportioning valve is STAYING due to safety....catch u guys later THANKYOU FOR YOUR HELP!!....

Posted by: budman5201 Nov 20 2008, 03:16 PM

Pads almost seated, brakes already better! give ya more updates in 80 or so miles

Posted by: Racer Chris Nov 21 2008, 12:09 AM

The reason for matching your pads front to rear is due to the coefficient of friction of the pad material. High performance pads such as Hawk have a much higher c/f than cheap street pads. Using high c/f pads will improve braking immensely as long as the rest of the system is functioning properly. I used stock brake calipers front and rear on my FP race car for years with no stopping problems from up to 120mph. You should not need any enhanced cooling such as the AJ setup unless you track the car. One thing to watch out for with high performance pads is squealing. I have a set of KFP race pads on my street car right now that squeal badly at 30mph or less.
I have to slightly disagree with Eric on the rear pad clearance. IMO .008" is correct and proper per the factory manual. I have always used this with no problems. Some aftermarket manuals specify .040" which is way off. Excessive clearance will lower the brake pedal, not reduce the force applied, except under light braking circumstances. The primary reason for adjusting the venting clearance is so the parking brake will work. There is enough play in the wheel bearing for the rotor to move 8 thou when you set the p-brake. Too little clearance will cause drag and overheat the caliper.

Posted by: Dave_Darling Nov 21 2008, 12:50 AM

Remember, though:

Brakes stop the wheels. Tires stop the car!

If you want to cut down on your stopping distances, get grippier tires!

(That assumes you can lock the brakes by standing on the pedal; if you cannot then your brakes are broken and must be fixed!)

--DD

Posted by: Eric_Shea Nov 21 2008, 10:49 AM

Except he has BMW calipers now with about 40% more pad up front on the same rotor. I agree however, probably not needed for regular street duty even with the BMW calipers.

.008" was the original spec. in the manual but they (Porsche) sent out a TSB revising that number after the manual was printed. All of the Haynes and Clymer folks picked up the .008" as well. Later the factory revised to .004" -or- basically the thickness of a business card vs. two business cards. I doubt there would be much difference as the mechanism in the piston allows for much more travel but, as the pads wear you may eventually have handbrake issues.

.008 - .004. Either one is better than where 80% of them are set right now.

Posted by: ConeDodger Nov 21 2008, 11:19 AM

E,
I would add to your advice that since he has the BMW calipers he should never have his rotors turned. They should be replaced as he needs all the mass he can get. His rotors were engineered with the 914 calipers in mind. They are getting lots more heat to dissipate with the BMW calipers...

As usual, my opinion is of no relevence and I bow to your superior number of wives.

Posted by: Eric_Shea Nov 21 2008, 02:18 PM

I don't know jack but... it sure is fun pretending online.

Posted by: ConeDodger Nov 21 2008, 02:26 PM

Still, I bow to your superior wife count... I am in awe!

Posted by: Phoenix 914-6GT Nov 21 2008, 02:34 PM

Then why did I spend so much money with you if you know nothing?

Eric is the man, heed his words and you too may have many wives of your own

On second thought, I can only handle the one I have

I have talked with Eric over the phone about brake combinations for a few hours and this guy knows what he is talking about. Not only that but he has the goods to get you what you really want and he will try to SAVE you money.

Posted by: Eric_Shea Nov 21 2008, 02:50 PM

TIP: Sisters. (one mother-in-law)

Jon Von B. Your check is in the mail.

Did you get everything hooked up yet?

Posted by: Phoenix 914-6GT Nov 21 2008, 02:59 PM

Not yet... getting it started though. Just got my car up on stands last night.

Posted by: horizontally-opposed Nov 21 2008, 04:33 PM

Never really thought about this before, but:

1. Get into Porsche brake rebuilding business
2. Acquire more wives

Potential connection? You decide

pete

Posted by: davesprinkle Nov 22 2008, 01:23 PM

Eric, you mentioned the increase in pad area. My understanding is that the fundamental contributor is the increase in piston area. Am I wrong? Can you comment further?

Posted by: budman5201 Nov 22 2008, 02:19 PM

WOO HOO!!! The verdict is in! My brakes are Sweet now. PADS BROKEN In........

Now the only limit are exactly as someone put it, my tires. My tires look brand new, but are obviously very old. Build date 2002. They are hard as heck when i try to bend the tread with my fingernail. NO give. So fresh tires all the way around soon, I bet i'll see even better than my stopping distance i already have...

Current setup. BMW calipers up front, hawk pads. New rubber lines all the way around. NEW calipers in back with Portofield Orange pads (now broken in fully). Patrick motorsports Brake fluid inside lines.

Stops on a dime, rears never lock up during emergency situations. Fronts Lock up easily, but probably a little too easily to once again NEEDED new rubber up front first.
Solution today or next weekend. Sticky nice quality tires.

COOL thanks guys for your help. My first 914 with Killer stopping.

Posted by: Eric_Shea Nov 22 2008, 05:22 PM

Both but, I'd say the pad area is causing the fronts to lock. Front pistons are 48mm which has thrown things off a bit as well which is why I recommend the 19mm MC.

Chris... curious as to why you mismatched the pads. Glad you're stopping better.

Posted by: budman5201 Nov 24 2008, 01:28 AM

i tried my best to find rear Hawks brand for the back, but couldnt locate a reseller so i chose the next best i though...portofields (the oranges is the one they sent me)

Wouldnt a 19mm MC increase my foot pressure needed for the same pressure to the pads?

Posted by: Phoenix 914-6GT Nov 24 2008, 01:31 AM

I'm thinking of doing a Portofield group buy through Eric in the next month or two. Maybe wait until then? Or maybe you want to start it earlier. I will jump on it whenever.

Posted by: Eric_Shea Nov 24 2008, 08:40 AM

It would give you a firmer pedal feel. You now have 48mm pistons up front. It's up to you at this point. I doubt you would notice any pedal effort increase.

Posted by: ericread Nov 24 2008, 08:47 AM

You married your sisters??? I thought you were from Utah, not Kentucky???

Old joke: "If you divorce your wife in Kentucky, are you still brother and sister?"

Eric Read

Posted by: Dave_Darling Nov 24 2008, 09:57 AM

3. ???
4. Profit!!



--DD

Posted by: Eric_Shea Nov 24 2008, 10:48 AM

Sorry Dave... #2 and #4 cancel each other out.

Posted by: westgl Nov 27 2008, 01:27 PM

Hey Eric,

Let me say, I wish I would have read this first!

I want better brakes as I have a new 200hp 200ft lbs torque motor going into my 74' 914

I too read the Pelican article, I had my local parts guy get the BMW front calipers.

I have not picked them up yet and asked him to get the stock 914 front calipers they should be here Monday

I bought the following from Pelican and receive these parts
1. 19mm Master cyl
2. new front & Rear rubber brake lines
3. New rotors Front & Rear
4. New organic Oem style pads front & rear
5. Rebuilt Calipers stock 914 Rear & now fronts at my local parts guy
6. Bought the T BUT will not use it, Ill stay with the valve

What would be your reccomendations.

Thanks in advance.

West

Posted by: Phoenix 914-6GT Nov 27 2008, 01:41 PM

Just because I don't know if Eric is checking in today....

Well, with the way you have everything set up you would benefit from better pads. What is your car se up for? Is it more AX/ Track car with some street or the reverse or only a street car?

Porterfelds are a very agressive pad but squeel like a little pig. I will be using those for AX and my Pagid's for the track. If you are running tires smaller than 205s stock brakes with great pads is really all you need.

Oh, and good decision on not using the T.

Posted by: yeahmag Nov 27 2008, 05:53 PM

Does "Alan Johnson Porsche" have a site? I'd love to look at this cooling set up for solid rotors.

-Aaron

Posted by: westgl Nov 27 2008, 06:24 PM

This is my setup,

My car is street car mainly but may want to AX or track

I do have 22mm hollow adjustable sway bar front
& weltmeister 16mm rear 100 lbs springs
Bilstien shocks all around

I want to get the elephant suspension bushings all a round
weld in flex kit incl rear arm kit

2004' Subie 2.5L 50K miles 9" clutch PP, subie headers, with 911 carrera 2in & 2 out muffler

West

Posted by: Eric_Shea Nov 27 2008, 09:56 PM

Aaron,

Hope this works:

http://www.ajusa.com/browse/vehicle/148/PNB/11994?sid=628c24b04f53be2225cad05da8e4c93c

West. I think you have gotten good advice from Jon. Make sure your 914 brakes are working and get some really nice pads, matched front and rear.

If you get very aggressive on the track (meaning you're doing this all the time) you may want to get a vented solution up front. Careful of the slippery slope as DaveP calls it.

Posted by: r_towle Nov 27 2008, 11:00 PM

I am curious why the original poster has not chosen pagid or porterfield pads for both the front and rear.

I would be scatching my head trying to tune the brakes with pads from different companies.

Rich

Posted by: Eric_Shea Nov 28 2008, 01:25 PM

If anyone else has this problem try sourcing early 911 rear pads from 1965-1968. Alfa 105/115 rear pads are the same as well. You will have to drill out one of the pin holes in the pad but, you'd probably have to do that anyway with these pads.

Posted by: budman5201 Nov 28 2008, 01:53 PM

Well i have portofield orange pads in the rear, but i got hawk pads first for the BMW fronts.i had the most trouble trying to find HAWKS for the rear. I didnt know i couldnt find them for the back and this is the first time i heard of the portofields.....Oh well guess i will switch to portofields in the front when i wear them out....

Posted by: Eric_Shea Nov 28 2008, 11:02 PM

Yup... looks like the early 911 ones are hard to find as well.

Posted by: Dr Evil Dec 8 2008, 09:14 PM

After conferring with Eric on this, I wanted to post my experience with the brake T here for posterity. My car was set up with 911 M calipers up front, stockers in the back, and a brake T in place of the prop valve because that was what I heard was the way to do it....same place Eric heard it from no doubt. I had 235 up front and 255 on the rear. On April 27, 08 my rear breaks locked up as I was coming out of a turn and, as confirmed by Eric, majorly contributed to my wrecking the car and injuring one of our members and my friend Chris. The rear definitely broke loose on me because I was breaking coming out of the turn. I had thought that odd, but after reading this thread and talking with Eric it makes more sense how things happened and I will never use a brake T again.

Posted by: Eric_Shea Dec 8 2008, 09:23 PM

If you don't mind... I'm going to try to find the PM I sent back to you. I think it has a lot of relevant info.

Thanks for posting. As stated earlier in this thread. "Real things can go wrong real fast". A little wet weather, a twisty and a locking rear caliper... you know the rest of the story.

Posted by: Eric_Shea Dec 8 2008, 09:33 PM

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.

Posted by: Joe Ricard Dec 9 2008, 06:22 AM

I never heard of Porterfields identified by colors. All I know is R4 Race pad R4S Steet/ AX pad.

I was reading about Carbo Tech the other day. Large selection. Might be worth a set of new pads to try them out. By other racing buddies love them on everything from 2800 pound 400 HP race cars to cute little Miatas.

Posted by: anderssj Dec 9 2008, 11:32 AM

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 )

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

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