Valkyrie

It seems that ever since I adjusted my brake pedal (lowered it a bit so I could have more leg room... it was a bit high anyway) a few months ago, my brakes seem to be a little less firm then they used to. If I step on them, the car will stop, and if I mash on them, the car will stop...quickly. I just want more pedal resistance, as it's more confidence-enspiring than having the pedal be a little soft.

I wonder, would adjusting the pedal mean I need to bleed the brakes? I did use cheap brake fluid (Advance Auto stuff), but I don't see how that would make a difference until the fluid starts boiling. I did make the brakes pretty hot while test driving it, since I made them drag a bit, though... but I think that happened after I noticed it was already a little soft.

Also, the pedal is a lot firmer when the car is off, because of the booster. It's about the amount of firmness I want, but without the effort of manual brakes of course...

Also, the pads are Hawk HPS (at least the rears are, the front ones don't have any visible markings), so I don't think they would lead to less pedal feel.

It might just be my imagination, and it might be just how it used to be (with me just being crazy), but I'd just rather have a stiff pedal, so does anyone have any ideas on how to do that?

They're crappo one-pot brakes by the way (although I think they have full-sized front rotors since it's an S5...).

Also, the master cylinder is brand spanking new (replaced it around the time I put my engine back in).


(btw, I've heard that the soft lines for the single-piston brakes will work for the four-piston upgrade, in place of the soft and hard line combination, since they're longer... can anyone confirm this?)

Maybe stainless braided lines would help?

SureShot

You probably already know this, but just in case..

Spongy pedal = air in the lines or possibly a bad hose.
Sinking pedal = leak in the system - usually a worn out master cylinder.
Erratic pedal feel = Bad vacuum booster or vac line to the booster.
Rhythmic bump in the pedal = warped rotors.
One brake grabs, but drags & dosen't release = bad caliper or bad hose.

Want to feel what great brakes are like? - Test drive an RX-8..

Valkyrie

I know, they have massive rotors...hehe (there's one parked next to me in my apartment complex... he gave me props too )

I plan on test driving the crap out of one at Zoom Zoom Live.

I wouldn't really call it spongy... and it doesn't sink, either. It's just too soft for my tastes.

I figure I'll have it bled somewhere just in case though, and maybe get some Ford Motorcraft high-performance fluid...

ericgrau

iTrader: (1)

A friend of mine tried bleeding his brakes, but he couldn't get all the bubbles out after hours of trying (he got a lot of air out though). Make sure you do the brakes in order, according to the Haynes manual, or just pay someone to do it. The Haynes manual recommends having a shop do a brake flush, because supposedly it's cheap with their equipment but hard to properly do yourself. A flush seems like a better option b/c most people almost never change their brake fluid. If I remember correctly it should be done every 3 years, regardless of mileage. Otherwise water will build up and no amount of bleeding will help you. Rotary Performance (www.rx7.com) says Ford Motorcraft brake fluid is great stuff and cheap. They carry it.

Valkyrie

I bled the brakes when I installed the new master cylinder, of course...

I think I'll get some lines from Mazdatrix (20 bucks less than the other places), and bleed them myself whenever I have the time to install them (which will be whenever I go home)...

vaughnc

The only way to 1 man bleed the brakes and clutch is with aftermarket speedbleeder bleeder screws. Forget the other methods, you'll end up sucking air back into the lines via the threads around the bleeder screws.

http://store.summitracing.com/partde...RUS%2D639550&N
http://store.summitracing.com/partde...RUS%2D639570&N

Qnty 1 - RUS-639550 SPEED BLEEDER 8MM X 1.0 PAIR
Qnty 2 - RUS-639570 SPEED BLEEDER 7MM X 1.0 PAIR

Valkyrie

Well, when I said I bled the brakes, I meant that I pumped the pedal while an experienced mechanic friend of the family worked the bleeders

(if they weren't bled right, the pedal wouldn't be so firm when the car is off... I think the squishy-ness is at least partly do the old rubber brake hoses... I wouldn't be surprised if they were the originals.

Twofer

Are these the same for Single pot brakes?

MPLSrx7

i just installed ss brake lines but dont know if it made my pedal firmer yet, since one of my calipers needs to be rebuilt.

Valkyrie

I've been thinking and I've noticed a few more things:

If I push the pedal REALLY hard, there is a point at which it becomes completely firm, but by this point, I would be braking so hard that I'd be almost garunteed to lock all four brakes up (unless I was driving with race tires or faded brakes)...

This makes me think that it's the lines, since there's more than likely a point where the lines stop expanding and let the pedal become firm (just like how tires will have sidewall flex up till a certain point, at which the tire will provide much more grip because it won't flex any further. Or, imagine a balloon inside of a cloth sack... it will inflate and the whole deal will become bigger until it's as big as the sack. Or perhaps a bit of stretchy fabric... it will stretch until it reaches a certain point, at which it won't tear, but it will not stretch any more)...

If it was air, or the hydraulics, then it wouldn't be so firm with the booster not working.

SS lines seem to be a bit skinner than the normal rubber ones, and the braided steel acts like the unstrechable cloth sack to surround the teflon (which is DAMN resistant to expansion, for something that's relatively flexible) inner line... so like everyone knows, it resists expansion.

So, after new tires, SS lines will be top priority, at least as expensive mods go.

Let us know how the lines worked after you get your caliper rebuilt...

bwood

Hey, SureShot, you couldn't have said it better. Although I was greatly disappointed with the power, the braking and handling of the rx-8 are the best of any rotary powered car...period!

Black91n/a

One thing you can do to firm up the pedal is to make a brake master cylinder brace. I made one out of a ~4" long piece of 2" square steel tubing, some stubby ~3/8" bolts and a long ~1/2" bolt. Bolt the square tubing to the fender using the short bolts and the long bolt will push against the master cylinder to stop it from moving as much (the firewall flexes). Be sure to pre-load the bolt for maximum effectiveness. Air can be a real bitch to get out, be sure to have the car level(ish) and never let the reservoir get too low, there's nothing worse than pulling air into the brakes. I have heard of a bad booster making the pedal soft and touchy, meaning it was boosting too much.

I just went to 4 pot calipers from the 1 pots and used 1 pot SS lines. They work just fine in place of the stock setup of soft line and hard line. You just have to screw the line into the caliper first, as there's no swivel there.

Valkyrie

That's good to know... as for the MC stopper, I don't think that would be nessicary since it's plenty firm when the car is off.

Seems to me that me thinking that my pedals are soft is for the most part, me just being ****/crazy/wrong... They're reasonable firm, I just want my resistance. I've never actually had the chance to just slam on the brakes. Even stopping at about 70% capacity from 60 MPH (ie, to stop at a yellow light you JUST couldn't drive through) basically means coming to a screeching halt (minus the screeching part), even with single-piston brakes and near-bald all-season (performance) tires...hehe

I'm gonna have a brand new set of BFG G-Force Sports on my car in a few days, though... hehe

What confuses me is that there feels like there is a physical block in the pedal after applying a large amount of pressure (while stopped). But there is no such stopper in the pedal at that point...

Does anyone know if this is normal (ie, just the lines becoming completely firm at a certain point), or if there is in fact something that stops the pedal at a certain point? I think that might be my problem, since I had messed around with the pedal adjustment.

I couldn't seem to adjust the pedals any more in either way without making them drag, or just making them softer...

Perhaps I need to actually put the car on lifts to do this adjusment, to get the absolutely maximum pedal slack out of the brakes? I didn't at the time, which in retrospect seems like it would have been the best idea.

Black91n/a

You need to be careful when adjusting the rod, as if you go too far then the MC piston might not retract fully after a braking event.

The stopper does help, just watch the firewall as someone steps on the pedal, you'll see it move. When I still had my single piston fronts I built the brace and an autocross tech inspector complimented me on my firm brakes, so yes, it helps (even with the car running I felt a difference)

For the pedal becoming hard at a point, it might be you bottoming the MC, which isn't too good. You could always swap to the TII MC, which is of a larger diameter than the NA one (no it's not just a differnece in the brake options, it's actually a TII specific part). It'll displace more fluid for a given distance pushed, and it'll be firmer, as the area increases, so to get the same line pressure you need to apply more force. That'll definetely firm up the pedal.

Don't dispair, single piston brakes aren't that bad, the RX-8 uses them and it's got great brakes. I used my single pot brakes at the track a bunch and they were more than enough.

ROTARYROCKET7

I see that you put two quantities for the Rear. Cant you just replace the top bleeders on the rear calipers? or is it better to just do both on each caliper.

Thanks

Jason NYC

ROTARYROCKET7

^^ are those the right sizes, i kept checking and they kept spitting out 7mm x 1.0 for front and rear. I have 87 gxl.

ROTARYROCKET7

Just checked russells site and its the same for front and rear.

86-92 RX-7 685600 Disc Disc 4 639570 639570

ROTARYROCKET7

I really want to order them, so can someone just let me know that that its the same size for front and rear. I have 4 pistons up front and discs in the rear for my 87 gxl.

Are they the same for single, 4 piston and floating calipers ?

Thanks

Jason NYC

Black91n/a

No, the lines are different front to back, the lines are also different between 4 piston and single piston front calipers, BUT you can use single piston front lines with 4 piston front calipers. I know I've done it and it works just fine. They probably just sell them all together in one package, so that might be why there's the same number, they're not really available seperately?

If you want good lines for less, get them from Corksport, or Mazdatrix.

Stanis

iTrader: (2)

I am in the same boat as the first poster. My brakes feel very soft, but I can still stop. I replaced the rubber lines with SS lines and it firmed them up a little, but they are still too soft. If I was to hop in our saturn and press the brakes with equal pressue/pedal distance I would have put everyone through the windshield. I have bled as good as I could have and went through almost two bottles of brake fluid (the big quart sized bottles) and didn't have much of an improvement.


Here is one for you, why when bleeding the front left brakes, the resulting pedal is on the floor, but when bleeding the back, the resulting pedal feel is full height?

On a side note, I do get a firmer pedal after decelerating in gear over the distance of a few hundred yards.

alexdimen

iTrader: (13)

I wish i knew what to tell you. I've had the same problem with my 4-lug brakes forever. I get decent braking, but my MC bottoms out before lock-up. The pedal is very sensitive too... then bottoms out half way to the floor.

what i've done:

pads
MC w/ new tokico unit
booster with low mile unit, tested for air-tight and pushrod travel on car
adjusted booster pushrod clearance as manual instructs
bled quarts of fluid through lines
greased calipers


i'm going to try a set of SS lines next... still have the original rubber lines

When you decelerate in gear you pull alot of vacuum. Maybe you should try a new/rebuilt/low mile booster. Black dragon automotive has good deals on them.

Valkyrie

Actually I bled my brakes and they're reasonably firm now.

The MC doesn't bottom out until WAAAAAAY after locking the tires up (and coming to a slamming hault), so your pedal is either way out of adjustment or you have some ungodly tires.

Also, the reason that bleeding the rear feels different than bleeding the front is probably because of the bias valve. It shouldn't take more than one bottle to fully flush a brake system, if everything is in good condition and assuming you don't screw up and let air into the system (ie, running out of fluid in the MC).

ROTARYROCKET7

um, your information was very good, i have learned something new. I was kinda referring to the speedbleeder sizes between the first and rear brakes calipers. I have SS mazdatrix lines on my car and they are very nice!.

I just want to make sure that if i order 2 sets of SpeedBleeders from Summit racing, the 7mm x 1.0. SOmeone posted two sizes, 7 and 8mm x 1.

Thanks guys

alexdimen

iTrader: (13)

^unless some rubber component is expanding or there is gas (air) compressing in the lines

oh, and my first post was in response to fossil_484

Stanis

iTrader: (2)

Here is a strange one, I went for a drive today and had firmer brakes than usual. Nothing has changed except for the time of day that I drive. Sheesh, a mind of their own I tell you.

Thanks for the info on the bias valve. I didn't know if something was wrong or not. The reason I used so much fluid is because I was expecting a firmer pedal after bleeding thinking I still had just that slight little bit of air somewhere in the system, but I guess not. I get lock up way before my pedal is on the floor so I'm ok there I suppose.