98 Outback: single or dual piston calipers?

[latitude xt]

Since my last wildly rewarding posts on this list, following which my
husband bought a $25 MAF on eBay, installed it successfully, and saved
us about $700, our automotive life has only continued to improve.

He had so much fun doing that, I gave him an adult education auto shop
course for Christmas. It's the best kind of course we could have
imagined: 3 hours per week doing hands-on work in a nicely-equipped
garage on your own car or those of fellow students. And where I had
worried that my 49yo husband would be the oldest student by far, he
thinks he may be the youngest!

His next project is replacing the front rotors and pads on the
Outback. He went to the parts store to buy this stuff and was asked if
his front brakes have single or dual piston calipers. How can he
figure this out?

Thanks!

--Emily

 

[1 Lucky Texan]

Since my last wildly rewarding posts on this list, following which my
husband bought a $25 MAF on eBay, installed it successfully, and saved
us about $700, our automotive life has only continued to improve.

He had so much fun doing that, I gave him an adult education auto shop
course for Christmas. It's the best kind of course we could have
imagined: 3 hours per week doing hands-on work in a nicely-equipped
garage on your own car or those of fellow students. And where I had
worried that my 49yo husband would be the oldest student by far, he
thinks he may be the youngest!

His next project is replacing the front rotors and pads on the
Outback. He went to the parts store to buy this stuff and was asked if
his front brakes have single or dual piston calipers. How can he
figure this out?

Thanks!

--Emily

According to this; http://www.cars101.com/outback_archive98-99.html
it's dual piston calipers on the front.

Alternatively, have him ask for both sets and then, after he inspects
the old pads, he will have the correct ones there and can return the
incorrect ones. The parts store should have no trouble refunding him
for unused mechanical parts.

Carl
1 Lucky Texan

 

[S]

Hi Emily!

Since my last wildly rewarding posts on this list, following which my
husband bought a $25 MAF on eBay, installed it successfully, and saved
us about $700, our automotive life has only continued to improve.

He had so much fun doing that, I gave him an adult education auto shop
course for Christmas. It's the best kind of course we could have
imagined: 3 hours per week doing hands-on work in a nicely-equipped
garage on your own car or those of fellow students. And where I had
worried that my 49yo husband would be the oldest student by far, he
thinks he may be the youngest!

His next project is replacing the front rotors and pads on the
Outback. He went to the parts store to buy this stuff and was asked if
his front brakes have single or dual piston calipers. How can he
figure this out?

There's something fundamentally satisfying about doing things
yourself; confidence building kinda.

Good Job!

Mmmmm, the calipers. You can tell by looking at the back of the
caliper; the dual piston ones have a double curvature to them that the
single piston ones don't.

But rather than rely on this, I would suggest that you actually rotate
the caliper away from the rotor, and take a look. You will see either
one large piston, or two smaller ones.

Easiest way:

Jack whichever front wheel happens to be in the sunshine, fit a
jackstand for safety, and remove the wheel. If you look at the caliper
assembly, you will see that it is mounted to a heavy steel
frame/carrier/whatever-ya-call-it, which is in turn bolted to the hub
with two hefty (17mm head) bolts. These are (or should be) really
tight, and rather than mess with them, what you want to do is remove
one (I think the lower one works best, but can't recall for sure; if
one doesn't seem like it's working right, try the other) of the
smaller bolts that hold the caliper body to the frame, and then pivot
the caliper up off of the rotor. The pads will stay with the carrier.
On the inboard side of the caliper you will see one, or two sorta
cup-shaped pieces, surrounded by a rubber boot. These are the pistons
that press the pads together when the brakes are applied Note the
shape of the back of the caliper roughly replicates the piston
arrangement. Next time, you will be able to tell at a glance.

The arrangement of bolts thru sleeves and bushings is what allows the
caliper to "float" as the pads wear. Everything here should be clean
and nice; (not gritty or rusty. a little clean grease is desirable)
the little rubber boots should be intact, and the sleeves should slide
smoothly in their associated bushings. Likewise, the rubber boot
surrounding the piston(s) should be in good shape without any tears or
cracks. There should be at least 1/4 inch of material left on the
pads, and it should be worn evenly across the pad, and from one to
the other. The surface of the rotor should be reasonably smooth, and
not heavily worn down where the pads grip.

Slide the caliper back over the pads, replace the bolt, and put the
wheel back on. This sounds like a lot, but in reality, it probably
takes less time to do it than to tell about it.

Hope this helps.

ByeBye! S.

Steve Jernigan KG0MB
Laboratory Manager
Microelectronics Research
University of Colorado
(719) 262-3101

 

[johninky]

The new pads will be thicker than the ones being replaced. This means
the caliper pistons will need to be compressed to install them. Crack
the bleeder valve and use a large screwdriver to push against the old
pads before removing them. This will force the pistons back into the
bores. I would recommend using OEM brake pads. Just not worth the
few dollars saved using cheap auto part store pads. Might be a good
idea also to replace the rotors if the car has a lot of miles on it.
Rotors held in place by two small screws that almost always are a bear
to remove. Something called an impact screwdriver is your friend
here. It is a screwdriver that you whack with a hammer. If you end
up rounding the heads of the screws that hold the rotor, just drill
the heads off. Screws not really needed as the wheel will hold the
rotor in place when mounted.

 

[Hachiroku $B%O%A%m%/(B]

Since my last wildly rewarding posts on this list, following which my
husband bought a $25 MAF on eBay, installed it successfully, and saved us
about $700, our automotive life has only continued to improve.

He had so much fun doing that, I gave him an adult education auto shop
course for Christmas. It's the best kind of course we could have imagined:
3 hours per week doing hands-on work in a nicely-equipped garage on your
own car or those of fellow students. And where I had worried that my 49yo
husband would be the oldest student by far, he thinks he may be the
youngest!

His next project is replacing the front rotors and pads on the Outback. He
went to the parts store to buy this stuff and was asked if his front
brakes have single or dual piston calipers. How can he figure this out?

Thanks!

--Emily

This is a dual piston:

http://www.ldm-tuning.de/pictures/W353-6726.jpg

A single piston caliper only has one 'puck':

http://bmwe32.masscom.net/sean750/caliper/newBrakeCalipers.jpg



A subaru dealer can probably tell by the VIN which it has, but not always...

 

[bugalugs]

The new pads will be thicker than the ones being replaced. This means
the caliper pistons will need to be compressed to install them. Crack
the bleeder valve and use a large screwdriver to push against the old
pads before removing them.

A note of caution:
If you undo the bleeder valve to make pushing back the pistons easier
make sure you don't let any air into the system otherwise you will get
spongy brakes and have to bleed the whole system.

Not a 'big' problem, just creates a little more stuffing around and a
pain in the posterior.

This will force the pistons back into the