Brake rotor replacement

Submitted: Saturday, Apr 21, 2012 at 15:05
ThreadID: 95047 Views:1938 Replies:5 FollowUps:3
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I have a Subaru outback which has developed front brake shudder. It has ABS brakes and I'm wondering if there is any reason why I can't replace the standard ventilated discs on the front with aftermarket slotted and ventilated rotors and leave the stardard disc rotors on the rear as I hope the ABS would compensate for any variance between the front and the rear.
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Reply By: garrycol - Saturday, Apr 21, 2012 at 16:01

Saturday, Apr 21, 2012 at 16:01
I don't see anything wrong with what you are proposing as long the rotors are a direct replacement - ABs will have noting to do with the the replacement though.

AnswerID: 483755

Reply By: member - mazcan - Saturday, Apr 21, 2012 at 16:18

Saturday, Apr 21, 2012 at 16:18
hi peterc18
are you sure the wheel bearings arent loose as this can also cause brake shudder you didnt say how many k's it done
have you looked at the the wear idicator on the disc pads to see if it is past the excepted thickness
as long as the replacements are of the same size and technical standards there shouldnt be any problems with after market parts
dont know where you live but
-brake and clutch australia -in your state should have parts
AnswerID: 483757

Follow Up By: Peter C18 - Saturday, Apr 21, 2012 at 16:36

Saturday, Apr 21, 2012 at 16:36
It has 235000km on it. Thanks for the suggestion it may be wheel bearings as I didn't even consider that so will check it out and yes the pads are due for replacement as they are down to about 2mm thickness. If thats all thats wrong I will be happy as I really don't need to spend too much at the moment.

FollowupID: 759023

Follow Up By: aussiedingo. (River Rina) - Saturday, Apr 21, 2012 at 18:40

Saturday, Apr 21, 2012 at 18:40
G'day Peter, mazcan is correct - it is usually a loose wheel bearing that creates the shudder, tighten them up to the correct setting & you will find it fixes the shudder. hoo roo
"the only thing constant in my life is change"

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Follow Up By: 120scruiser (NSW) - Saturday, Apr 21, 2012 at 19:07

Saturday, Apr 21, 2012 at 19:07
Can't adjust Subaru front wheel bearings as they are a hub type.
They are tightened by the drive shaft bolt.
It is a common thing, brake shudder and many reasons can cause it.
When you fit new rotors ensure the surface where the rotor seats up against the hub is clean otherwise the rotor will not sit flush up against the hub and cause the shudder.
The shudder is called "Disc thickness variation" It can also be caused by brake caliper retention or even sticky pistons and slides in the caliper.
By fitting slotted and drilled rotors to the front and leaving the rear standard will make no difference to your braking. The idea of the slotted and drilled rotors is to let the gasses that develop during braking dissipate. I have slotted and drilled DBA rotors on the front and standard solid rotors on the rear of my 80 series.
The ABS is completely separate and will still work fine.
I used to have a page on my workshop website about brake shudder which was an excellent read but considering I sold the workshop a few years back , well the website was shut down.
Hope this helps
FollowupID: 759050

Reply By: Ross M - Saturday, Apr 21, 2012 at 17:00

Saturday, Apr 21, 2012 at 17:00
G'day Peter
At 235,000 if the discs are the originals then I would be replacing them as they will be worn enough to require machining.
Add the cost of machining and then still having old discs is probably not best value.
Because you will also require new pads the total cost won't be much above the fixup of the old.
With new you get full braking performance restored to the vehicle, particularly handy if you also tow a camper etc
The slotted and vented ones will better handle wet situations but you won't notice any increase in performance.
Your ABS sensor will be attached to the hub so shouldn't have any connection with the brakes themselves.

Ross M
AnswerID: 483761

Reply By: Ron N - Saturday, Apr 21, 2012 at 18:50

Saturday, Apr 21, 2012 at 18:50
Peter - A major problem with virtually all new vehicles, is that, with the drive to keep weight down, this means that most disc brake rotors have been thinned down to the point, where they buckle when you hit floodwaters, and the rotors are hot.

The ventilated rotors are worse for this than the old solid rotors - but most solid rotors are pretty much on the way out, now, and ventilated rotors are fitted to about 95% of vehicles today.

Brake shudder is invariably buckled rotors. There's generaly little benefit in skimming (machining) buckled rotors, as there is so little metal to work with.
Couple that with high labour costs, and generally lowered prices for new rotors, and new rotors are generally the best bet.

The ABS system merely prevents wheel locking under heavy or panic braking. A sensor on each wheel senses when the wheel has stopped turning and releases the brake pressure to that wheel, then reapplies it milliseconds later. This process repeats until the heavy brake pressure is released.

The rotor thickness, type, condition, or amount of wear in your braking system is not measured or compensated by the ABS - the braking system is self-compensating for wear, and only when the brake fluid reaches a low level, will warning lights be activated.

Cheers - Ron.
AnswerID: 483771

Reply By: miandering fiander - Saturday, Apr 21, 2012 at 20:45

Saturday, Apr 21, 2012 at 20:45
A friend of mine in a 150 series T/D Prado suffered front shudder, thought brakes then bearings etc.. Turned out to be loose wheel nuts.
Tightened up and problem gone.
AnswerID: 483789

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