I upgraded my C4 brakes last year to the J55s (13" rotors and slightly bigger calipers). Nice improvement, but still not as good as my more modern BMW daily driver.
Being great friends with Google, I discovered that numerous C3 and C2 owners had experimented with using hydraulic boosters in lieu of either vacuum boosted or non-boosted brakes. The reviews from those who had made the conversion seemed to be quite positive with respect to greater stopping power from the hydraulic boost. Also, you save some space in the engine compartment (over the vacuum booster).

Now, on to the C4. I think mine (and many others) would benefit from the hydraulic boost, but I haven't seen any first hand reports of the conversion. How come? is it because the plumbing is too difficult? Is the PS pump inadequate to boost the brakes and still service the power steering? Is the Feng shui out of phase?

I'd like to hear from anyone who's tried it, or has at least investigated it further.

Thanks!

 

Never investigated a different braking system such as Hydroboost, but I will tell you that most of the stopping is in the pad material themselves. If you just street drive, try some Hawk HPS pads. I have those pads on my 96 and it will stop as good or better than my 540i M coupe.

 

Check out;
http://www.hydratechbraking.com/

They make hydroboost braking systems for all major cars and some trucks, I know they systems for corvette.

8Valve

 

I have the J55 brakes with Raybestos ceramic pads on my car. I don't have any trouble getting the brakes into ABS with the stock vacuum booster. I can't imagine how you could improve on that.

 

Forget the booster idea, get some hawk hp plus pads that will totally transform the braking feel.
Standard pads DO NOT BITE THE DISC ROTORS they have limited metal friction content, you can stand on the brake pedal and barely slow the car even with a good booster all your pedal effort will not make braking better if you have limited friction material in the brake pads.
Even with the standard early c4 single piston callipers these pads and good dot 4 brake fluid would not fade after many laps... my stomach doesn't last as long as the brakes...
The J55 update made brake effort lighter however when i went thru one set of hawk hp plus pads, i put a standard set in while waiting the week for airfreight of new hawk hp plus pads. These made a massive for worse difference, they felt like rubber pads coated with grease i felt i needed an anchor to slow me down.
They went straight in the bin when my hawk hp plus pads arrived.

The only downside is lots of brake dust and decreased rotor life, but friction does the braking so expect 3 sets of pads then new discs.

Never forget if you want brakes that work and inspire confidence go for the hawk hp plus pads you will never go back to standard pads again, if you only want the brakes to slow you and use a car in front to stop you go get cheapo brake pads .....

Do not forget the adjustable intermediate pin between the booster and master cylinder, if this is not adjusted properly that can affect how the booster assist works. However you will have a fair bit of pedal travel if this is wrong, well adjusted brakes just need the smallest amount of pedal travel and effort for great braking .

I can do as many hot laps on a track with the J55 brakes no brake fade powerful stopping power lap after lap after lap after lap, standard type pads may do one or two laps and just turn to powder leaving you with pedal to the floor with all the pad material in power form on the track.

http://www.parts123.com/parts123/yb....Z5Z5Z50000050F

Or street hawk pads more gentle on rotors below.

http://www.parts123.com/parts123/yb....Z5Z5Z50000050F

 

Thanks to all for the replies. Looks like i need to investigate better pads before i spend $600+ on a new braking system.

Thanks for the suggestions on pads. I do autocross, and it sounds like either Hawk or Raybestos will be an improvement.

Stay Tuned!

 

I have a 96 with the J55 brakes; I had a correspondence with Hydratech regarding their product and as to your specific questions, allow me to quote the relevant portions:

" with '90 and newer c4 applications is that the ASR / traction control assembly has to be relocated slightly....The ASR bracket can be carefully bent to raise the package upward...."

"The second issue is that the reverse rotation power steering pump is known to be a bit noisy, though does provide the pressure and volume needed to properly run this type of hydraulic brake assist system"

"this system will fit up through the '96, but the ASR has to be relocated, which is why we only list to the '89"....

"Summary ? yes - the systems are available....suggested primarily for competition use"

 

Thanks very much for the valuable insight!! That's what I was looking for. That clearance issue was one I didn't expect, since all the other research i had done led me to believe that the hydroboost system only solved that problem for others. It's not a show stopper, but I certainly have to weigh it if I decide to proceed. Since I'm considering doing this to a vert, I don't worry about noise from the PS pump- I couldn't hear it over the wind noise, tire noise, etc.

As others have suggested, the brake pads are worth upgrading first, and that's a fairly easy chore!
I'll look at the forum vendors to see who has a decent deal on better brake pads.

Thanks, again!
Paul

 

The recommendations to improve the "friction materials" are fine so long as the hydraulics are in A1 condition! If there's issues with either the hydraulics or the "boost" then "friction materials" won't improve squat!

There's more hydra-boost systems out there other than the one mentioned in the thread. They're all not as highly advertised but they're out there. There's even electric boost. If a person had a booster failure or maybe a master cylinder failure there might be reasons to consider a change.

I don't believe any of the available product is "bolt-on" for a C4 - a change would require much thought and research.

 

As another C4 owner with only so-so brakes I've been looking into the whole hydroboost possibility.

Over the years I have swapped, replaced, reconditioned every part of my 86 Vette brakes with little improvement. That includes multiple pad replacements including all the HPS pads mentioned earlier.

The brakes are OK but I have never been able to exercise the ABS on anything other than a wet road or grass. I reckon I'd pull the steering wheel off in my hands before the brakes would lock on a dry road. I've had them double checked by a proffessional brake shop as well as a Vette shop but both say they are normal from experience.

The new hydratech kits add up to around $800 if you include stainless braided hoses which is quite an outlay. However there seems little doubt that those that fit them say they are brilliant.

The cheaper route that seems popular is adapting the 92-95 Chevy Astro van hydroboost units. They can be picked up used for around $80 to $100 complete with the MC from a wrecker or re manufactured from places like Autozone for a little more.

From what I can gather the Astro unit without MC is about 6-1/2" long but needs to fit in the 4" gap that the power booster fills. Otherwise by the time you bolt on the C4 MC you'll be very close to hitting the wheel fender. This may be a problem or it may not? The Astro MC is longer again and I think it best to keep with the proportioning benefits of the original MC.

It seems Mustangs circa 2000 on also use hydroboost units and I see several used ones on Ebay for around $140. They like the later Astro units mount on the firewall at an angle so are generally not recommended.

I've include a couple of links about adapting the Astro unit to various early muscle cars that shows it should'nt be too hard to do the job for a fraction of the new kits.

http://www.carcraft.com/techarticles...boost_salvage/

http://bangshift.com/blog/tech-how-t...-or-truck.html

http://members.shaw.ca/pekpress/HydroboostSwap.html

 

I have HPS on the front of my 85, I believe now that I changed my front tires I could go to HP+. I do not even have the J55 brakes and no anti-locks. With my old Sumitomo's on front I would lock the fronts up all the time, now with new Toyo's I could stand on the brakes from 70-10 pretty hard without locking and stopping hard. Good pads, good bleed, good fluid are the keys from my experience so far. I'd love to go up to J55 brakes, but VBP kit for just under $1000 isnt worth it to me at this point. I'd rather put $1000 into headers/exhaust/engine work. New pads for me in the spring will be HP+ on front and HPS on rear (I do not currently know what is on the rear).

 

Have you checked your vacuum lines?

 

As stated above, the hydraboost stuff adds enough length to the system that they can be trouble to fit up. Also, many of the OE one's angle upwards so even if the length isn't an issue hood height can be. I ran into this years ago retrofitting a GM hydroboost into a C3. After all the work and remote mounting the reservoir the system is awesome!

 

Your experience is exactly what I ran into when first upgrading
my 93 c4 brake to J55.

I stupidly put EBC 'green stuff' pads on because (at that time) they were all that were in stock at summit racing equip which is about 3 miles from my house. Summit didnt carry Hawk then (but does now).

I took the car to a nelson ledge track evnt and I found I got fade from a single 80 to 0 stop into the pits.

I asked the same question, like you, and everyone gave me similar answers to try Hawk.

That said, I took the plunge and did Hawk HP plus.

Hawk HP plus is a step more 'racer' than Hawk HPS pads. Its still not a true race pad.

The change was more than I could ever have expcted. My dreams of 6 piston front brakes and stuf disappeared as
this J55 system is now adequete for my needs.

They bite. You push the pedal and they bite into the rotor, not slide.

I do not notice any unusual increased rotor wear either on my 2 piece baer eradispeed rotors. Nothing unusual there.

Theres 2 downsides:

1. Squeak, when cold. You can expect a squeak at evey stop. This drives some peopl nuts. I consider it a necessary evil. Once warmed up, little noise.

2. Dust like heck. Im always cleaning dust off my wheels. I heard rumor once that if they dont dust, they dont stop. I believe it.


If those 2 downsides bug you, then consder their Hawk HPS product.

They are the best pads you can buy. Their competition is not up to par

I have them at all 4 corners.

I would start there.

I had a bmw 330i with zhp performance pack once. It had an amazing braking system. I believe those cars have a hydraulic booster also, so I can see why you were looking at those systems.