How much improvement in stopping distance and is there an upgrade for 1LE on the rear also ? Have read several posts about there being several different spindles dependent upon size of wheel, etc. Anyone in the know, please post...thx

Bill E.

 

From my understanding it wasn't that 1LE's stopped that much sooner, but rather that they could do it over, and over again without brake fade.

That is, at least what I've learned in my reading.

 

If you have an 89 with rear discs, I assume you have the PBR's (alum calipers with the so-called 12 inch rotors out back--these are the good brakes), and I also assume that you have the cast iron calipers with 10.5 inch rotors up front. There is only one spindle for the 1LE brakes (alum calipers with dual pistons and the so-called 12 inch rotor), one that you must slightly modify. Check the Spohn site and do a search. You should find plenty of info. Note my sig.

JamesC

 

James,

Just curious, why do you call the rotors "so called"? Are they not 12"?

 

they measure 11.86" if i remember right.

 

Okay, thanks.

 

Huh? So my rear brakes are bigger than my front? Funny....

I got the BW 9bolt w/PBR brakes on my 89 GTA. I"ll have to take a look tomorow, but I didn't think the rear brakes were bigger than the front.

 

yeah, the rear pbr discs are bigger than the fronts unless you've got the 1le package.

 

Big brakes on the rear, marginal effect. Bigs on the front and watch out! Though I did the 1LE swap and highly recommend it, there are other packages out there, which are as good if not better than the 1LE swap--and perhaps cheaper. Check out some of ebmiller's posts for more info on the C4.

JamesC

 

Hahah! Just went out and did a quick visual on the brakes. Yep, the rears are bigger than the front.

Can't beleive I never noticed it before. I do have some grooving on the rear rotors though. So I guess its times for new rotors and pads. Then again, I'm doing all of that this march, along with new flexible brake lines to replace the old rubber. They are getting rather stiff, and last season I was pulling to the right when I initially pressed the brakes.

 

So basically the only difference between my '89 4 wheel disc and the 1LE setup is repeatability (less fade). ???? Not any difference in one time stopping distance ?????

Keep it to this comparison, not an older 3rd gen vs 1LE which obviously would be a major difference, thx for the input.


Bill E.

 

The front brakes are responsible for some 70% of the car's stopping power. As a consequence, bigger rotors and dual piston calipers (vs stock 10.5 rotors and single piston calipers) equal better stopping distance.

JamesC

 

Yes, knew all this but, the numbers I have seen are only about
a 10 ft reduction in stopping distance,
( hoping someone had better numbers)
not exactly a good bang for your buck since one could spend aroud 900-1150 on this mod .

Anyone done this , does it FEEL that much better to justify this expense ?

Bill E.

 

Ten feet? Baloney. Shoot, at 80 mph, Earl's braided steel brake line kits by themselves are said to reduce stopping distance by as much as 18 feet. Couple that distance with top-notch front brakes and you'll be heading for the windshield. I've done the 1LE swap. I'm impressed--so much so that I'm collecting parts for a rear swap as well.

JamesC

 

18 ft with just braided hose, sorry but that is a lot of baloney.
Well maybe if your stockers had 200k and looked like balloons when you stabbed the pedal.



Check out Baer brakes catalog I was just looking at , they list average stopping distances with their sport 12 inch rotors, about 6-12 feet less than stockers.....the great improvement comes in fade and repeatability. Stock numbers are listed in several posts if you search for 1LE. Again I wanted info on 89 up 4 wheel disc versus 1LE. Your 85 probably has some miles on it and didn't have rear disc, so yes you would see a major improvement, see my point

Bill E.

 

My 85 has always been a four-wheel disc car. It now has 1LE fronts with Earl's lines all arround. Good luck.

JamesC

 

OK...now I just happen to have a wee bit of experience ( Ok ...a lot ) with the 10.5" front and 1LE combo. Stock ( and that is the key word ) the only advantage to the 1LE package is fade resistance.

Why? Because the 1LE package uses the same GM proportioning valve as the 10.5" brake package ( J65?? ). Now GM, ( and most mfg's ) set up the brake balance with a fairly hefty front Bias. This prevents lawsuits... locked front brakes much safer for Grandpa...who never really understood how to trailbrake . However...this does not maximise the braking potential. Maximum braking potential occurs when all four tires are working at 100% of their braking potential.

70% bias to the front on a RWD car is incorrect . It is much more like 60\40. FWD cars may use up to 70% but not a RWD car.

Actually, depending on the car and setup, you can use a surprising amount of rear Bias. As you lower the CG, increase front spring rate or introduce more antidive...you can use more and more rear brake Bias. Front weight transfer is decreased, so that more weight remains on the rear tires under deceleration...thus the brake balance can be adjusted more to the rear.

Back to the stock J65\1LE comparison. The stock J65 will outbrake a 1LE on the street..or in Autocrossing. Remember , GM uses the same proportioning valve on both cars. The J65 combo was built first. Thus it's valving ( which is already front biased more than necessary ) was setup for the 10.5" \ 11.8" . To be continued....

Edit: Spelling

 

Continued.... When GM added the 12" front brakes, this changed the brake balance to be even more biased towards the front. Excessively so. The rear brakes now are not working to their full potential.

Curiously, this is what happens when people upgrade to a " Big Brake " package ( Fronts only ) and increase the size of the front rotors and put in big Caliper ( Like 4 piston or 6 piston ). The result is a huge increase in front braking capability...but no increase in the rear. The fronts will lock so much sooner than the rears, that your stopping distances will actually increase.

Grass Roots Motorsports ( Feb 2004 ) has an excellant article on exactly this problem. It's all about balance. If you increase your front braking efficiency...you must increase the rear by the same amount to keep the brake balance within design parameters.

They modifed a 2001 Audi A4 with different packages. The first was a typical " Big Brake " package. IE: Front's only. Stopping distances were longer than the stock brakes. Various tests were done, with and without ABS, swapping in different components and re-testing. Only when the rear brakes were upgraded to match the efficiency of the fronts, was a significant reduction in stopping distances seen. It's a very, very good article. I'd recommend getting it.

Now in my case, I went from a tried and tested 10.5"\11.8" combo that has served me very well for Hillclimbs, Autocross and Street use. Worked very well....and could haul me down from 120MPH no problem..... once . The problem was of course that the front brakes were too small for the occassional track days.

So I upgraded to a " Big Brake " combo. Wilwood Nascar 12"x1.375" front rotors with 4 Piston SuperliteII calipers. That should fix things...right? Wrong!! I've got so much front brake now that the car's braking distance has gone up dramatically. Even with the adjustable proportioning valve cranked to 100% rear...the rear brakes just aren't doing enough work.

To correct this I will be installing a set of Superlite II's on the raer. I've done the math, and the rear SL's with 1.375" pistons should bring the brake balance back into the proper range. The front SL's have 1.750" pistons.

One thing to remenber about 3rd Gen rear calipers ( PBR ). They have a very small brake pad and a very small piston . This reduces clamping force on the disc. One of the main reason so many people with 3rd Gen's complain about poor rear brakes.

Whewwww...rather longer than I had intended....but I hope I have provided some usefull info.

Edit: Spelling

 

Thanks chickenman great info alot of help, hope the rear mod solve your problem. I believe I will leave well enough alone with my stock 89 4 wheel disc setup.

Bill E.

 

Just to make things clear. If you deleted the stock proportioning valve, and then added an adjustable proportioning valve with a 1LE setup...then you could crank in much more brake Bias to the rears. Then the 1LE package would be a desirable upgrade if you want to do some competition events.

In my experiences the 10.5"\11.8" package has worked very well for me. Granted...everything must be 100% perfect and I spent a lot of time playing with pad materials ( I use Bendix Titanium front and rear )...but for every day use and Autocross they are more than adequate.

However...if you have the money to spend...I would certainly consider something like Spohn's 13" brake kit.....with a suitable upgrade to the rear. Which Steve and Alloy should be coming out with any day now....right guys?

 

[QUOTE]Originally posted by Chickenman35
[B]Just to make things clear. If you deleted the stock proportioning valve, and then added an adjustable proportioning valve with a 1LE setup...then you could crank in much more brake Bias to the rears. Then the 1LE package would be a desirable upgrade if you want to do some competition events.

No competion for me, so that said would the 1LE front mod with adjustable valve do me any good on the street ? thx for the info

Bill E.

 

It sounds like a guy might get a little extra out of his stock brakes with an adjustable proportioning valve ?

Bill E.

 

Yep... you'll be surprised how well the 10.5"\11.8" combo can work. IMHO,.... no competition use...save your coin. 10.5"\11.8" combo more than adequate for the street.

 

I've been looking at brake upgrades as part of my winter front/rear suspension rebuild project. I have owned this car for 10 years, and been unimpressed with the brakes since the day I bought it. The brakes fade like crazy even during a single high speed stop. Stopping distances I measured last fall as a baseline were 60-0 in 199 ft for the first stop, and 213 ft for the second stop. Toyota Camrys and minivans make my GTA look like I'm Fred Flintstone dragging my feet to stop or something.

I have already decided upon installing an adjustable prop valve; I have a Wilwood unit in the garage to be installed after the front end goes back together. I have been on the fence about whether to upgrade the front brakes now while I have the spindles off and they're easy to mod, or to install the adjustable prop valve alone and get another set of data first to see exactly what improvement there is to be had. This car sees daily driver duty during the warmer months, so I can't go too nuts with the rear brake bias since it has to be controllable on wet roads. I've already verified that the rear brakes aren't working well (see https://www.thirdgen.org/techbb2/sho...ar+brakes+lock ). If I do another test with just the adjustable prop valve installed, I'll post the results.

 

I thought you couldn't run an adjustable proportioning valve with the stock prop valve in place?

 

Thanks for the info Chickenman35 I don,t have tons of cash and I would have been really bummed out if I spent what money I do have on somethings that didnt help out much in day to day driving.

 

In 1989 the 4 wheel disc brake system cosisted of 11.65" rear rotors with PBR aluminum calipers and 10.5" front rotors with delco moraine calipers. While the 1LE had 11.65" rotors in back and larger 11.86" front rotors with PBR dual piston calipers. I belive the main advantage of them was they were capable of repeated hard use with less fade.

 

You can't....you ditch the stock proportioning valve entirely.

 

why can't you just gut it?

 

Brake pad MFG makes a big difference. I've really been impressed with Bendix Titanium. Raybestos were absolute garbage. Car would not stop.

In the wet you can actually use MORE rear Bias than in the dry. Why? Because you get lees front weight transfer in the wet. Car will not decelerate as fast.

That's one reason why race cars have the brake bias adjustment inside the car where the driver can reach it. In the wet you can normally crank some more Bias to the rear...over and above the optimum setting for dry.

 

Do a search on this....already been answered. Search for my name. I went into detail why you can't. In short...it just won't work.

Gotta hit the sack now...work at 5:00AM Yuck!!

 

Here ya go found it quick...read down to my replies.

https://www.thirdgen.org/techbb2/sho...hreadid=213653

And here:

https://www.thirdgen.org/techbb2/sho...hreadid=214136

Bad, bad things will happen if you gut the stock Prop valve and try to use it.

 

Please don't take this as a flame, Chicken, you do know your stuff, but I disagree with you here. The 1LE system does indeed call for a different prop/combo valve than the stock J65 system. I had to switch mine out during my swap. I'll use my '88 Iroc as the example. My stock valve was P/N 14089497 and I had to switch to P/N 14089496. I also had to swap out my J65 stock master to the J50 master, P/N 18014286, which is what all the cars from '89 and up used. J65 and 1LE DID use the same prop in '89, but for '90-92, they are different.

Guys, have you looked into the C4/C5/LS1 upgrades yet? I have a full 1LE Iroc and now the C4 system on my RS with drums out back and the C4s perform great, just like the 1LEs (which they actually are, BTW..). If money and a budget is your concern, definitely look into these upgrades, You will NOT be sorry. You get the same performance of a big name brake system (Baer. SSBC) for less than half the cost. No brainer here guys...

Ed

 

Ok Ed. You've succeeded in cornfusing me AFAIK, the '90-'92 cars used the same proportioning valve whether it was stock or 1LE. Can you point me in the right direction for the proof/PNs because everything I have seen indicates they are the same.

Tim

 

Hey Tim...

They all used the same MASTER, not the props. Master is 18014286 ('89-up).

Props are different. Here we go:

1989 J50 (2nd design) 10136839

1989 J65, 1LE (2nd design) 10136840 <<<<<<<<< SAME

1989 J65 (Exc Y82, 1LE) 10136841

1989 J50 (1st design) 14089495

1989 J65, 1LE (1st design) 14089496 <<<<<<<<<<SAME

1989 J65 (Exc 20th Ann pkg y82, 1LE)(1st design) 14089497

1990 J41, J42 10136839

1990 J65,1LE 10136840 <<<<<<<< DIFFERENT

1990 J65 (Exc 1LE) 10136841 <<<<<<<< DIFFERENT

1991 J41, J42 10136839

1991 J65 10164112

Notes:
J41= Iron rear drums
J42= Alum rear drums
J50= Standard disc/drum
J65= 4 wheel disc
1LE= duh..


My manual only goes thru 1991. All you guys with '88 year cars upgrading to 1LEs need to use P/N 14089496 prop valve, first design.


Ed

 

Is that correct? J65 shown as having both 10136840 and 10136841 Prop valves?

Was this from factory GM parts manual? Not disputing facts, but it is confusing. Same question with 1989 J65, which looks like it could have had four different valves.

[quote]1989 J65, 1LE (2nd design) 10136840 <<<<<<<<< SAME

1989 J65 (Exc Y82, 1LE) 10136841

1989 J65, 1LE (1st design) 14089496 <<<<<<<<<<SAME

1989 J65 (Exc 20th Ann pkg y82, 1LE)(1st design) 14089497[/b]


It looks like GM originally had different valves for the J65 and 1LE option, but superceded them to the same numbers??

From info at 1LE.net:

1408949X were all first revision valves with 1.0mm threads

1013684X were all second revision valves with 1.5mm threads.

Oh how I miss my "daze" as a Nissan partsman. Nothing like pouring over the " Pink sheets" ....lists of superceded parts numbers. Once ordered some Con Rod bolts that got superceded to shock absorbers!!! Try explaining that one to your customer. LOL.

 

Thanks Ed. You've just given me the reason that I need in order to install an adjustable proportioning valve. If I have to replace the proportioning valve then a Wilwood adjustable one is going to get installed. I need more back bias anyhow. Thanks again!

Tim

 

Yep, my GM parts and illustration manual, 1991 version. It's confusing to say the least. I had a hard time just getting the numbers right when I posted all that!

Ed

 

I have copies of the GM Service Parts Manual regarding the brake components and can back up all the numbers Ed posted.

FWIW, my understanding is that "J65" simply refers to 4 wheel disc brakes. Based on that, a plain J65 car would have the smaller 10.5 rotors/cast iron single piston calipers ('88 and earlier models had this at all 4 corners, '89 and up had PBR/11.xx" rears and 10.5"/cast iron up front) — and a J65/1LE car would be 4 wheel disc with the larger rotors/aluminum PBR calipers at all four corners.

The J65/1LE cars used a different prop. valve than a standard J65 car.

There were (2) different master cylinders used - J50 and J65. A J65 MC was used on '89 and earlier standard 4 wheel disc cars. 1LE cars used the J50 MC. Disc/drum cars also used the J50 MC.

Starting in '90, GM dropped the J65 MC and used the J50 MC for all models. The J50 is the standard replacement MC sold at any auto parts store or at a dealership regardless of what your car originally had.

 

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