Proportioning Valve question?

[90turbotsi]

I looked around a bit but got a lot of non informative posts. Simple question, is there a difference between the 2G FWD turbo and 2G AWD turbo brake proportioning valve? So in the case where one swaps GSX calipers up front on a GST would it be smart to do the GSX proportioning valve as well or not needed or the same part? Thanks

 

[92awddsm]

Honestly, I dont know if it is different. I asked the same question 2 yrs ago and no one answered. After I installed my dual piston front calipers, I decided to remove my abs. Well, the only donor car I could find was a 92gs n/t witout abs. I have been using that proportioning valve and brakelines since then with no problems or complaints. Actually, my braking is alot better since I swapped but I also went from abs to non-abs.

 

[90turbotsi]

Thanks for the reply... well in my 1G AWD I upgraded to the dual piston calipers and never a proportioning valve. I dont seem to have any problems with them at all as is.
I am now working on a 2G project, and wanted to do a brake upgrade. The car was sitting for a while and needs some new brake parts so I figured Id do it right/better instead of just making them work for inspection. If I do need this part while the system already needs to be bled then its not a bid deal just dont want to find out that I should have when its all said and done if that makes sense.

 

[Goobdog]

http://www.vfaq.com/mods/BigBrakesInfo.html Scroll down.

 

[90turbotsi]

Thanks however :

95-99 ??? ???

Is all it says for the 2Gs so I really have no idea if they are different or not

thanks tho

 

[Talon ESI-T]

2g FWD and 2g AWD prop valves are different. about 40.00 from satan.

Think about it, since the front has more braking, the rear would need more to keep the proportions correct.

I checked part numbers to be sure.

Terry

 

[Todd TCE]

I'd suspect differences are based on the weight bias of the car as well as any changes in caliper or rotor use. Just having the added weight over the rear end would allow for more brake application.

 

[90turbotsi]

Hmm, the car being a FWD soon to have GSX brakes would it make sense to leave the FWD proportioning valve as it is a FWD and does not the added weight of the rear and such? Or would it be beneficial to run the AWD valve because if so I will order it now to do it with the swap
thanks

 

[Talon ESI-T]

Well my thought was now that you hve a greater percentage of brakign in the front you you would need more in the rear to keep the propation correct. Granted you do not have the 3xx additional pounds and rotating assy there. Is it important, NO could it help, i am sure it could to a small degree.


The GST/GS ect is only 300 some odd pounds lighter and that weight is not all in the rear. The weight factor is not great enough to be factored in IMO.

Terry

 

[90turbotsi]

Ok well I guess I should also factor in I went with the powerslot plus brake upgrade...uses the stock calipers with larger rotors (powerslot bought out the AEM brake division) This means 12.5 inch rotors front and +1.2 inches in the rear I forget stock side on them.

thanks
Jon

 

[jtmcinder]

FWD and AWD prop valves are the same on 2Gs. What matters is whether it is w/ ABS or w/o ABS.

- Jtoby

 

[90turbotsi]

Good deal, thanks for that info. The car has no abs which I kinda like so I guess im set. Hopefully my parts all arrive by the end of the week Hawk pads, Full powerslot plus kit (larger rotors), SS lines and new AWD calipers so the car should stop well... now just to break in my fresh 6 bolt that has 10 miles on it. Kinda hard to drive a car with frozen brakes and no rear pads

thakns again

 

[Talon ESI-T]

FWD and AWD prop valves are the same on 2Gs. What matters is whether it is w/ ABS or w/o ABS.

- Jtoby

Why are there 4 different P/N part numbers? 2wd w/ABS 2wd wo/ABS and 4wd w/ABS 4wd wo/ABS

http://www.trademotion.com/partloca...1350&make=9&model=Talon&year=1997&catalogid=1


The proportioning valve is different and thats proof, if you dont beleive then fien you dont have to.

 

[jtmcinder]

I am having difficulty getting P/Ns from the link you posted. I had no problem looking up the specifications in the shop manual.

- Jtoby

ps. lose the attitude

 

[Talon ESI-T]

No attitude, I just dont see why you wish to debate they are different when the factory sells different ones. I will get some part numbers when the dealer opens....I called a month back and they were not very nice about looking them up. I should have wrote them down. I will get proof.

Edit: just spoke with the dealer and there was a note on the P/N thzats states the different numbers are due to production year. They apparently changed the Prop valves in 98. If you have a 95-97 then the proportioning valves are the same. In 99 they were different. I didnt get part numbers for the 99 series because i am a bit busy at work right now and i didnt want to waste his time anymore.

Makes me wonder what was different in 99, the master i have is from a 99 and the rest of the system is pre 99.

 

[jtmcinder]

Does anyone have a 99 shop manual to look up the split points and reduction ratios? I knew the 97s weren't different from looking it up. I, personally, trust the shop manual over dealers by a factor of ten.

- Jtoby

 

[_Madman_]

I tried to study the subject and couldn't find a good answer, so I decided to bring this thread back in case someone has more info.

I have a good opportunity to make a 2WD to AWD front brake swap. What bugs me is what people who have actually done it think about the results.

How is the bias, do you actually have a better stopping distance or it just feels this way because front tires are digging in because of unbalanced braking power proportions?

I'm thinking about getting 4 slotted Brembo rottors + Ferodo pads

Or maybe I should just go for cross drilled?

P.S.
The main reason why I do the swap is because all 4 rotors are warped real bad and I do use them heavily.

 

[turboglenn]

Your front brakes are 70% of your stopping force. Having more bias to the front helps since those tires see the most traction. If you bias too much to the rear you're just going to be locking them up on hard braking. Just keep the stock valve or buy a real adjustable proprtioning valve so you can dial it in to your preference. That's what i'm going to do when i put GSX brakes on mine this summer.

 

[_Madman_]

Yea, but if I'm correct then having more bias in front can actually increase your stopping distance compared to stock. Especially at high speeds, and adjusting must be real P.I.T.A.? Especially if you accidentally hit the spot where tail slides faster then the rest of the chassis...

 

[ACM]

Stock brake bias has a preponderance of front bias - this is a detriment to ultimate braking, but a fig leaf to compromised suspension. That is to say, it is safe for all conceivable situations an incompetent driver will encounter with a stock car.

Can you improve upon that ? Certainly.

So long as you change the car's dynamics first. Define your new dynamics and a brake setup can be determined.

Brakes are easy physics - brake setup is not.

Thanks,
Charles

 

[_Madman_]

Stock brake bias has a preponderance of front bias - this is a detriment to ultimate braking, but a fig leaf to compromised suspension. That is to say, it is safe for all conceivable situations an incompetent driver will encounter with a stock car.

Can you improve upon that ? Certainly.

So long as you change the car's dynamics first. Define your new dynamics and a brake setup can be determined.

Brakes are easy physics - brake setup is not.

Thanks,
Charles

That bias thing is exactly what I'm afraid of. Basically, stock car is front biased as is. Now, if I swap front brakes for meaner GSX brakes I will get even more front biased car, won't I?

And I'm afraid that all I'll get from the swap will be that my front tires will be locking up every single time I come near brakes. And, as far as I understand, that means I will actually get longer stopping distances because I wont be using all 4 tires as close to max as I can use them now.

That might be especially true because of the lighter GST rear end compared to GSX.

I really want to hear the results from someone who has done the swap.

 

[Todd TCE]

There's no easy answer here. Without knowing what you have now...how will you ever be able to determine cause and effect? What is the stock bias now? If you don't know that answer or how to calculate it (even using my on line page) then you shouldn't be messin' with it is how I read it.

Once you know what you have now then calculate the change you'll get. What happened to the data when you changed the numbers?

And while larger this or that can be important so to is line pressure. Prop valves are all about line pressure, nothing more. If you make a change that requires more line pressure up front the same will apply to the rear- you only have one mc. So....if it's up then it must be better in the rear too? Not so fast. If it's up too much, too soon it hits the knee point and stops elevating- fixed pressure. (dont' understand? that's ok research is what it's about- it can lead to your "over biased" front brakes but not from hard parts, from line pressure)

*And the chance of your front tires locking up all the time are about slim to none, however you are on the right track.

 

[_Madman_]

Well, the toughest part is that I don't have a garage and data to calculate all those things, so basically I would like to hear your advise on following:

Is it better to
1) Just swap all rotors to Brembo slotted and put on new set of pads.

2) Do a front brake kit swap, get all 4 AWD Brembo slotted rotors and new set of pads and deal with bias issues later if they crop up.

Again, I do use brakes hard and they warp like crazy on all cars I drive.

 

[Todd TCE]

Well, the toughest part is that I don't have a garage and data to calculate all those things, so basically I would like to hear your advise on following:

True. Making a lot of that very difficult to really evaluate before going and swapping parts!

Is it better to
1) Just swap all rotors to Brembo slotted and put on new set of pads.

Changing a rotor won't make your car stop any better. A rotor is a rotor when it comes to oem replacements. With very few exceptions. The OD is the same, the width is the same. The math is the same. Putting new pads on the existing ones or even inexpensive blanks will net nearly the same result. The value is in the pad not the rotor.

2) Do a front brake kit swap, get all 4 AWD Brembo slotted rotors and new set of pads and deal with bias issues later if they crop up.

A front kit swap from other AWD applications is common as I've read for years. Will it move bias to the front too much? You'll need to run the numbers and see. Can you get it back in check? I think you could with some improvements to the rear pads. Will you notice all of this? Probably not. Unless you plan to run track days in which case you'll burn it all up anyhow.

Again, I do use brakes hard and they warp like crazy on all cars I drive.

Poor choice of pad compounds combined with perhaps questionable driving habits produce this problem more than anything. Pads with ample Cf and temperature range need to work in conjunction with proper cooling after use. Come down a curvy road at speed, on an off the brakes then stop at the light for 3min with you foot on the brake pedal...that's not a brake problem thats a driver problem.

 

[_Madman_]

I know that main factor for breaking force is tire grip, and I don't expect that by changing rotors I will be able to stop faster.

But all rotors are warped, so I have to change them.

If I stick with Brembo I at least have a hope that they wont warp as easily, that they cool better and have better friction at high temperatures. They might have higher heat capacity as well.

If I swap front brakes I will get even more higher heat capacity on front wheels where the main work is done and that might prevent excessive warping in future.

And actually bigger rotors might decrease the stopping distance on track when you have to brake for the turn after 120mph straight, or after bunch of turns which will warm your rotors up real good.

But I haven't been pushing the car on track a lot so I can only guess if it's worth it. The additional rotating mass on front wheels is not a bonus as well when it comes to acceleration.