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9-3 Sedan, Cabrio ('04+)/Combi & 9-3X Workshop 9-3 SportSedan, Convertible ('04+)/Combi & 9-3X , 2003 - 2012 Technical Forum

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  #1  
Old 10th April 2009
SchneiderIS SchneiderIS is offline
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Default Rear brakes wore out before fronts...

I have 44,000Km on my 9.3 and the rear brakes are down to 15% while the fronts are still at 90%. Most of my miles are freeway with little city traffic so I expected my brakes to last much longer but the real question is why the rears wore out so much faster than the fronts. In my opinion there is something very wrong here.

Does anyone have any similar experience or know of brake issues?
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  #2  
Old 10th April 2009
Dex4 Dex4 is offline
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I take it you've owned the car its entire life?
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  #3  
Old 10th April 2009
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greekfragma greekfragma is offline
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nothing to worry about mate......its common on our cars to change the rears two to 3 times faster than fronts.
all people that know Saabs characteristics will tell you that this is normal and its the way the 9-3 is designed.

I am also wondering why this occurs and I cant find a logical explanation so far.

maybe its customised to perform better with the harder setting on the rears.
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  #4  
Old 10th April 2009
SchneiderIS SchneiderIS is offline
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Quote:
Originally Posted by Dex4
I take it you've owned the car its entire life?
I have and I am not hard on the brakes.
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  #5  
Old 10th April 2009
SchneiderIS SchneiderIS is offline
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Quote:
Originally Posted by greekfragma
nothing to worry about mate......its common on our cars to change the rears two to 3 times faster than fronts.
all people that know Saabs characteristics will tell you that this is normal and its the way the 9-3 is designed.

I am also wondering why this occurs and I cant find a logical explanation so far.

maybe its customised to perform better with the harder setting on the rears.
I would say it is very odd though given that all other cars use the fronts considerably more than the rears. That is why you often find front brakes sized larger than the rears. Even the shop manager thought it strange and is looking into it.

I was quoted $700CND just for the rears. That is more (not by mch) than the Bremo's on my old Merc ML500.
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  #6  
Old 10th April 2009
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PRD2BDF PRD2BDF is offline
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Ah, don't worry about it. I had to replace my rear brake pads at 44K too.

My theory is that they used ceramics up front and organic out back plus a more even brake distribution causes the rears to go out faster. Typical brake force distribution is about 70/30 (front/rear) and I think the Saab is at least 55/45, it never dives under hard braking...
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Old 10th April 2009
SchneiderIS SchneiderIS is offline
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Quote:
Originally Posted by PRD2BDF
Ah, don't worry about it. I had to replace my rear brake pads at 44K too.

My theory is that they used ceramics up front and organic out back plus a more even brake distribution causes the rears to go out faster. Typical brake force distribution is about 70/30 (front/rear) and I think the Saab is at least 55/45, it never dives under hard braking...
The specs say nothing about Ceramics being used out front. If they were using ceramics they would have been touting it like mad since it is a higher end brake technology. What the spec's do show is that the rear pads have half the surface are of the front. That would indicate a greater expectation of front to rear braking.

Of note, are you saying 44K "miles"? I am talking about 44K "kilometers". With 1.6Km per mile that is quite a bit less mileage.
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Old 10th April 2009
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I have organics front and rear. The rear wear considerably faster than the front.
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  #9  
Old 10th April 2009
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can someone confirm that the rears have less material on them or if they are made with less density?
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  #10  
Old 10th April 2009
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toplessFC3Sman toplessFC3Sman is offline
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Quote:
Originally Posted by PRD2BDF
Ah, don't worry about it. I had to replace my rear brake pads at 44K too.

My theory is that they used ceramics up front and organic out back plus a more even brake distribution causes the rears to go out faster. Typical brake force distribution is about 70/30 (front/rear) and I think the Saab is at least 55/45, it never dives under hard braking...
How much the car dives under a given amount of braking has nothing to do with the brake bias, its almost completely dependent on the suspension stiffness and geometry (and slightly on the tire type and pressure).
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  #11  
Old 10th April 2009
Paul_Amaranth Paul_Amaranth is offline
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Wow, you got 44K? I had to replace them around 27K. For no reason other than I've never had another vehicle with the screw in piston design for the rear calipers (and I've never had another vehicle go through rear pads so quickly), I'm going to lay the blame on that. I have no evidence, but I suspect they do not retract as far as regular calipers and the reduced clearance leads to faster wear.

After I get my car out of storage next month I'll have to shoot the temps with an IR thermometer after a mile or so run without braking. All the disks should be within a couple degrees unless something is dragging. Even 15-20 degrees more in the back would be significant, especially if it's similar on both rear disks.
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  #12  
Old 10th April 2009
SchneiderIS SchneiderIS is offline
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Quote:
Originally Posted by Paul_Amaranth
Wow, you got 44K? I had to replace them around 27K. For no reason other than I've never had another vehicle with the screw in piston design for the rear calipers (and I've never had another vehicle go through rear pads so quickly), I'm going to lay the blame on that. I have no evidence, but I suspect they do not retract as far as regular calipers and the reduced clearance leads to faster wear.

After I get my car out of storage next month I'll have to shoot the temps with an IR thermometer after a mile or so run without braking. All the disks should be within a couple degrees unless something is dragging. Even 15-20 degrees more in the back would be significant, especially if it's similar on both rear disks.
It would be very interesting to hear what you find out. 27K is definitely not right. Heck, I don't think 44K is right for the size of car and the type of miles I am doing.
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  #13  
Old 10th April 2009
SchneiderIS SchneiderIS is offline
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Quote:
Originally Posted by greekfragma
can someone confirm that the rears have less material on them or if they are made with less density?
Don't know about thickness or density of the pad but the manual shows the surface area as half.

My theory is if the rears were designed to engage more than the fronts the surface area would be greater than the front.
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  #14  
Old 10th April 2009
Stage1 Stage1 is offline
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Quote:
Originally Posted by SchneiderIS
Don't know about thickness or density of the pad but the manual shows the surface area as half.

My theory is if the rears were designed to engage more than the fronts the surface area would be greater than the front.

You guys must be professional stunt/racecar drivers I have 104,000 on the same set of rotors and pads since Oct 2003! This includes time on the Autobahn, Autostrasse, and Autostrade and quite a few curvey scenic roads where I didn't see much.

Mine are wearing pretty much even.
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  #15  
Old 10th April 2009
Paul_Amaranth Paul_Amaranth is offline
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Basic physics makes the fronts do more of the braking effort. When you brake, the forward momentum gives you a slight rotation over the front axis unloading the rear wheels. The proportioning valve is there to make sure the rears don't lock up, which they would if they had the same braking capacity as the front. Suspension tuning may affect body roll, but you can't change the basic physics. The fronts do 60-70% of the work.

Every other vehicle I have ever owned, I've had to change the fronts twice for every change on the back. Saab is the only vehicle I know of where this is backwards. Everyone I've talked to, including dealer service reps, tells me this is normal. It might also be cheap OEM parts. (Saab doesn't make brake pads, you know, they're probably sourced out of China) I'll have to wait for the next change to see.

I almost starting calling up the Saab customer service chain, but figured it would be faster to just change out the pads..
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Old 10th April 2009
CMerriman CMerriman is offline
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I think it might have something to do with the quality of factory pads.

I replaced my rear pads this time last spring, with name-brand ceramics. Just by looking at thm now, they look like they are still brand new. And strangely enough, I still have not had to change the front pads, and I've owned the car since Sept 2006, and have racked up 32k miles.

The car has 60k mile on it, and I don't think the fronts have ever been changed
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  #17  
Old 11th April 2009
ak1551 ak1551 is offline
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I noticed that when I changed the rear pads on my 06 that the Rear disk was not vented. solid disks run hotter which causes them to wear faster. I don't know if the front disks are vented or not.

On my GLI I had the same problem and it was due to solid rear disks that were always hotter than the vented front disks. The brake bias on the GLI was definitely toward the rear. I loved kicking the rear end out with the rear brakes. I haven't had time to mess around w/ the 9-3 yet.
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  #18  
Old 11th April 2009
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Quote:
Originally Posted by SchneiderIS
The specs say nothing about Ceramics being used out front. If they were using ceramics they would have been touting it like mad since it is a higher end brake technology. What the spec's do show is that the rear pads have half the surface are of the front. That would indicate a greater expectation of front to rear braking.

Of note, are you saying 44K "miles"? I am talking about 44K "kilometers". With 1.6Km per mile that is quite a bit less mileage.
Ceramic rotors and pads, yeah, they'd brag about that, but not just ceramic pads, lots of people use ceramic pads, or some form of ceramic compound on their pads. Fairly common.
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  #19  
Old 11th April 2009
loplop loplop is offline
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My old Lexus IS300 wore rear pads before the fronts... We also had one other vehicle that wore rear pads faster... Can't recall if it was the Land Rover Disco II or our FJ Cruiser, as both are gone now (and we never got around to replacing them).

Although the rears are doing less braking, the calipers/pads are much smaller. So it is entirely conceivable that the rear, even if it is only providing 30% of braking, could wear out first.

Also, the compound differences mentioned above could make a difference.

Our '08 Aero has vented rears, and in looking up pad replacements, I see the '08s all share rear pads. Did Saab start putting on ventilated rears to alleviate customer concerns?

Paul: Your idea is a good one. I could test this with my RC Car IR temp gauge I now use for cooking... I have no idea where I'd b able to drive 1 mile without braking at all, tho!

What's the big deal in replacing pads at 30-45k? Pads are between $50-75, depending upon what you buy. Even if you can't (or don't want to) DIY, any good mechanic can do this in an hour. The braking performance of the car is good, and $150 every 2-3 years seems it's worth it to get that performance.
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  #20  
Old 11th April 2009
SchneiderIS SchneiderIS is offline
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Quote:
Originally Posted by Stage1
You guys must be professional stunt/racecar drivers I have 104,000 on the same set of rotors and pads since Oct 2003! This includes time on the Autobahn, Autostrasse, and Autostrade and quite a few curvey scenic roads where I didn't see much.

Mine are wearing pretty much even.
Thanks, that is what I was expecting for performance out of mine. I really am convinced that there is a problem here.
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