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Old 12-06-2017, 03:04 AM   #1
stiligFox
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Default Brakes help

Hello all! Having some brake issues that I would like to finally get fixed as I'm tired of having so many scares!

I had the pads and rotors replaced recently, but I don't know what brand my mechanic used. My other mechanic said that they are very hard rubber pads, but about 90% of them are left. I want to replace them because my braking distance is atrocious; it's about half of that of my 1997 S90 or even my dads 1990 F150! I can stop about 4 car lengths shorter in any other car, and it surprised even my Mom who's driven 240s/740s/960s for the last 25 years...

Anyway my mechanic keeps telling me they are fine but I know they can be better. The rotors are warped the heck and back now even though they are new, because the pads are so hard. My mechanic won't turn them as he says the new style rotors are too thin, but I feel like I should probably just replace them as well. I'm also thinking about putting on iPD stainless steel brake lines since A) the original lines are likely old by now and b) the IPD lines are cheaper than getting new Volvo ones!

The other issue I've begun to notice is that when I first start driving, I'll put the car in reverse to leave the house, and I feel a sharp pulsing in the brake pedal for a few yards; it feels sort of like chest congestion in the brake line. While I'm driving every now and then there will also be a soft thud in the brake system. Any idea what these might be? Could it be the ABS sensors getting old?

My main question for the moment I guess is; what brake rotors and pads do you all recommend for good quick stopping power? I'm not doing any racing, but are slotted rotors of any particular help?

Thanks for the advice guys!!
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Old 12-06-2017, 07:32 AM   #2
DET17
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I think your 92 likely has the same front brakes as mine. When I first resto-modded mine, I converted all 4 corners to Zimmerman rotors and a "medium aggressive" pad, like a PB Metal master or similar. I have just removed that front setup and upgraded to 302mm front rotors and later 850 calipers. One of the key improvements I discovered (via the web, not yet experience) is the AKEBONO pads (spelling suspect, not much coffee yet). The reviews on these are excellent; search and you'll see what I mean.

All that said, the early 9 series brakes leave a lot to be desired. Mine have always had normal function, but never impressed me; I'm expecting better performance with the upgrade. The 95+ vehicles in the 9 series family got a braking upgrade, which is claimed to significantly help (details in my build thread).

Since your vehicle is basically stock, I'd get new rotors (my Zimmermans are available) but the key thing will be the improved pads. Beyond that, you're going to spend much more $$ trying to improve the system. Are you sure your brake booster (servo) is working properly?
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Old 12-06-2017, 08:22 AM   #3
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double post, sorry

Last edited by Janspeed; 12-06-2017 at 08:40 AM..
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Old 12-06-2017, 08:22 AM   #4
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Your post does not mention what car. i assume it is the '92 965 in the sig.?
A car from 1992 is old... and it is a good idea to do a complete overhaul on the brake system because all parts will be old.

Brake pads are never made of rubber... any pad that's available for streetuse should work OK. (Racing pads might need to warm up to perform properly, they are not very suitable for streetuse)
And new rotors will not warp easily , specially not it the brakes perform badly (= not able to put heat in the rotors! Rotors warp because of excessive heat and temperature shocks)
New rotors should be installed on clean rustfree boltflanges. Any rust on those can cause the brakes to feel like they are warped. (attention to detail matters)
On a 900 (and 700) it can also be the case that the mushroom bushings in the lower control arms are shot. Very common problem on these cars. Also the cause of weird movement in the front suspention when driving backwards. These can also be the cause of brake judder and making the brakes feel like the rotors have warped when in fact they are not.

about ABS sensors: they do not wear, they either work (= produce an electric signal) or they don't.
however, It sometimes does happen that corrosion on the ABS tooth rings or debris on the tip of the ABS sensor cause bad signals = problems for the ABS.
It's a good idea to clean the toothrings and sensor ends to ensure proper functioning. The (only!) sensor for both rear brakes is in the rear diff cover.

don't fixate on the pads and rotors. (unless they are obviously totally worn out but that's easy to see). Slotted rotors will not increase the brake performance at all. They are there for cooling and expelling gasses coming from hot pads. Not needed on any road car. The stock brakes should be able to provide plenty of stopping power.

Instead make sure the entire brake system itself is functioning 100% (your post suggests that there is something seriously wrong, a well sorted stock 900 should be able to brake really hard.)

- it is smart to change old rubber flex hoses. They can cause all kinds of annoying and potentially dangerous problems. (internal swelling, cracking due to dryrot causing fluid leaks) if in any doubt, change them.
- the front calipers do 70+% of all brake work. So, if you are disappointed about the performance start by checking the front brakes first for quick wins. Make absolutely sure those front calipers are working perfectly. Make sure all pistons can move freeling inside the caliper, that the pads are not stuck on the edges inside the caliper (remove debris/crud/rust), that they can move freely along any slidepins. Here attention to detail matters.
- Brake fluid is hydroscopic, it attracts water. old brake fluid will have captured water in it. This water will easily boil inside the brake fluid. Boiling water turns into compresseable steam... these steam bubbles prevents you from putting proper pedal pressure on the brakes. That's why you need to flush the system with clean new fresh DOT4 brakefluid and make sure to bleed the system perfectly. Start bleeding the rear brakes first en move your way to the front brakes.
(be careful not to snap any bleednipples. Remove rust with a small wirebrush, give all bleednipples a shot of penetrating oil. Give all bleednipples a light tap on the end to shock them lose. only then try to open any of those for bleeding. If you snap one off you have an annoying problem...
- bleeding tips: tap the calipers to shake lose any trapped airbubbles. Then bleed again. If you keep having problems bleeding the system, try jacking the car up at the end where you want to bleed. It could help air to reach the high point (= your bleednipple) easier.
Brake bleeding can be done with a helper but easybleed toolkits are not very expensive and will make it a oneman job.
- With the engine running check if the brake booster is able to hold vacume , check if the oneway valve inside the brakebooster hose still functions like it is supposed to.

If everything is OK after checking/correcting and you still have a soft pedal that does not hold pressure then you might have a worn (internally leaking) master cilinder. Replace... and bleed the entire system again...

finally: in the whole equasion of braking the TIRES also play a crucial role. If the tires are old the rubber compound will have hardened. (check the 4digit production date code on the sidewalls of the tires) Your car can have perfect brakes but if the brake forces can't be transmitted to the road then the car will not perform very well. The tires will lose grip early while braking and ABS will prevent the wheels from locking up by releasing brake pressure (you can hear and feel it in the pedal)... increasing brake distance...
Fresh new grippy tires will reduce your brake distance.
At least make sure you optimise tire grip by using the right tire pressure (when i had my 940 i found 2.5bar/36psi to be optimal on 205/55x16 and for 195/65x15 i used 2.4bar/35psi for optimal grip.

Last edited by Janspeed; 12-06-2017 at 09:50 AM..
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Old 12-07-2017, 05:28 PM   #5
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Thank you for all the advice!! I'll start by checking the things you mentioned. Dad was thinking to check for vacuum too, I'll do that as soon as I get her back from the shop. The only reason I was thinking that the rotors are horribly warped is because when I was driving on a freshly paved stretch of highway here in town, she sailed along so smoothly until I slowly put on the brakes, when I could feel a shudder going through the pedal like a foot massage...

My mechanic just called today and said he's replacing the ball joints to help fix a steering noise issue, could that be related?

I'll definitely check the front brakes out, and try cleaning up those, as well as a brake line flush. Might go ahead and re do the lines because these ARE 25 years old! Then will check the brake booster vacuum and go from there...

I do need new tires as... mine are about 5 or 6 years old and the rubber is definitely hard from sitting in the Texas heat; we're going to replace those too in the next couple months.
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Old 12-09-2017, 12:58 PM   #6
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the metal lines should not need replacing unless Rusty. rubber hose yes. and you can bench bleed the master so you don't have to rebleed the whole system
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Old 12-09-2017, 02:23 PM   #7
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Quote:
Originally Posted by freevolvos View Post
the metal lines should not need replacing unless Rusty. rubber hose yes. and you can bench bleed the master so you don't have to rebleed the whole system
Huh? There's air introduced in the lines when you disconnect them from the MC, you still have to bleed them, but you also have to bench bleed the MC.
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Old 12-15-2017, 04:49 AM   #8
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OY! Got her back and it’s gone from bad to worse...

ABS light comes on, and I can feel all kinds of popping and groaning when coming to a stop. Speedometer is rapidly fluctuating within +/- 5mph of my real speed. The OBD port under the hood isn’t even registering that the ABS computer exists... I’m going to check the rear speed sensor for the speedo and the over voltage relay for the ABS computer.

Any thoughts? What should I clean the ABS sensors with?
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Old 12-15-2017, 09:41 AM   #9
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Who did you take it to?

Only one RWD person in town that would get my business...
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Old 12-15-2017, 11:01 AM   #10
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Quote:
Originally Posted by kzoc View Post
Who did you take it to?

Only one RWD person in town that would get my business...
Took it to Redline - Troll swapped both sway bars, replaced the front ball joints, tightened down a lot of stuff. I took her in for knocking while turning in place but it still does that some; new ball joints really tightened up the steering though! Having him check the brakes was a secondary thing and he said they feel fine while the ABS wasn’t working. Going to give him a call today and see if he had noticed the speedo not working when he was testing stuff.

I only trust Cap-V and Redline around here...
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