Backward Brakes Update

Please scroll down for updates below…..

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As a follow-up to the backwards brakes posting…..

Ted found an interesting thread over at SaabNet that discussed this issue and in that thread, it was stated that the grooves should “attack” the pads (i.e. the outer part of the slot hits the pad first). This statement is coming from Brembo’s website.

Taking a look at the photos I placed on the original post (see above link) that would mean that the front wheel I photographed is correct and the back wheel I photographed is correct. Of the Saab stock photos, the front wheel on the convertible (high contrast photo) is correct but the front wheel close-up is actually fitted incorrectly.

I had a close look at all my wheels this morning and it seems that both of my rear wheels are correct. The curious thing is that I have one correct wheel in the front (LHS as photographed) but the rotor on the RHS is incorrect. What makes this even more curious is that the incorrectly fitted rotor in the Saab stock photo is also a RHS wheel.

Now the issue becomes one of whether or not this is correctable.

i.e. the new front rotors that were installed back in November were ordered as a pair. Did they send a mismatched pair or are they all like this?

I haven’t noticed any problems with my braking at all, but it’ll be interesting to see what the outcome is.

Matt the Fudgepacker – any input you might have on this would be welcome.

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UPDATE II:

The following has been sent off to Saab Aust via their website. I’ll let you all know of any answers that are forthcoming.

Hi Saab Aust,

I have a 1999 9-3 Viggen and my attention has just been drawn to an anomaly with my brake rotors.

As you know, the rotors on the Viggen are slotted rotors. I had my rotors replaced when I purchased the car back in November 2005. I’ve only now had my attention drawn to the fact that the slots in the rotors point different ways on each of the front rotors.

On the LHS the slots are directed so that they ‘attack’ the brake pad, i.e. the outermost point of the slot hits the pad first. On the RHS rotor, this is reversed and the innermost part of the slot hits the pad first.

I have posted pictures and a summary of the issue at the following website, which I invite you to take a look at.

http://www.trollhattansaab.net/archives/2006/09/backwards_brake.html

I’d like to resolve the issue and find out if a) the rotors are, in fact, meant to be oriented in a specific manner (i.e ‘attacking’ the pad or otherwise), and/or b) if the orientation of the rotors, or more specifically the slots in the rotors, is likely to have any detrimental effect on brake performance or wear.

Your assistance with the above would be appreciated.

Steven Wade

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UPDATE III

Just a few hours after my query, a very quick reply from Saab Australia:

Hi Steven

Thank you for contacting Saab Australia.

A couple of points:

Viggen Rotors are not directional.

As the grooves do not connect to the internal venting of the disc they have no real effect on cooling.

Regardless of direction the surface area of pad to rotor will remain the same, and therefore brake force will be consistent.

Hope this helps,

Thanks to Saab Oz for the very quick response.

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11 Comments

  1. Steve,as you have the only Viggen in Tassie and as yet i have not realy had a good look at the brakes on it,and no other stock standard SAAB has slotted rotors,i cannot realy tell whats right or wrong.
    What i can say is that the discs come as a single part numbered pair both front and rear,so if your rears are ok,but one of your fronts is not then it does seem odd.
    Having had a quick look at the Brembo sight it seems that straight vained slots like on your car are non directional and can be fitted on either side.
    Their information seems contradictory though,example.
    The first two vane types are non-directional, and can be used on either side of the vehicle. The curved vane disc, however, is directional. A curved vane disc must be installed with the vanes running back from the inside to outside diameters in the direction of rotation. Please see figure. Orienting the disc in the manner creates a centrifugal pump. The rotation of the disc causes air to be pumped from the center of the disc, through the vanes, and out through the outside diameter of the disc. This greatly enhances the disc’s ability to dissipate heat.

    Additionally, all of Brembo’s slotted discs are directional as well, regardless of the vane geometry. The discs should be installed such that the end of the slot nearest the outer edge of the disc contacts the pad first. Please see figure.

    So a curved vane must run from the centre to the outside in the direction of rotation(which turns it into a centrifugal pump)This is the way i am sure they should be fitted as logic states.
    But the second paragraph contradicts this by saying that the edge of the slot on the outer edge of the disc hits the pad first.(this does work if your brake pads/caliper is rear mounted but does not work for front mounted calipers).
    I will have a chat with some race tech friends of mine and let you know.
    Your brakes are fine though Steve,and obviously swapping the front discs from left to right will solve nothing.

  2. Thanks Matt – a) for the insight, and b) being willing to sign on as ‘fudgepacker’.

    I have some photos I received this morning of some 9-5 ventilated discs that appear to fit the Brembo description above, i.e. curved slots that channel the heat outwards.

  3. Steve,

    I reckon when Steve Eyles ordered these, he simply ordered a “pair”, meaning for use on either ‘axle’. I’ve never seen these sold otherwise, as in a “pair” being for use on either side. I can’t see that they’ve packed the contents of the box wrong, either, meaning that they must be fitted correctly.

    I fitted slotted rotors to BenW’s red sled a while back, but I can’t recall the orientation of the slots. Ask BenW for himself.

    Drew B

  4. DB – yeah, I reckon Steve’s ordered the right thing. The photos I’ve spied of other Viggens seem to indicate that this is a common occurence.

    Given the description on the Brembo site that Matt mentioned, I’m just unsure as to whether Saab are sending out the right thing when people ask for a pair of ventilated rotors. If they’re slanted a certain way for a reason then they should ensure that the pair they send is oriented the right way.

  5. Thinking about this a little further, I can’t see the orientation is that critical anyway, particularly at speed when centrifugal force will disperse water, heat, etc, towards the outside of the rotor anyway. I’d just be interested to see if there was any noticeable difference in pad wear from one side to the other.

    Drew B

  6. After a quick trip onto two parts websites, indeed the brake rotor parts are listed as different for the Viggen — something that I didn’t expect.

    Soooo…. I stand corrected.

    At least I’m no fudgepacker.

  7. The part numbers are different for Viggen discs than standard discs as the part numbers for 95 aero discs are different to standard 95 discs.
    But the part number for the front viggen discs is for a set not individualy.
    And don’t knock fudgepacking till you’ve tried it.

  8. I repeat myself.

    On Viggen that is perfectly normal. Saab made both rotors identical so on the left side of the car it will look a bit strange but on the right side it will look normal. This is all perfectly ok though.

  9. Swade, while you seem to have managed to generate one of the funniest threads so far this year and I hate to bring it to a logical conclusion……I reckon two minutes on the phone to Adrian the genius mechanic will sort this. Will call him in the morning and let you know his take on it.

    Meanwhile, why don’t you all down there in Tassie just get back to the fudge? Not that there’s anything wrong with that……

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