Brake Caliper Identification 2012 Legacy

[colinmi]

Hello, I am new here and am looking to jump right in. We have a nice pair of ruby red 2012 Subarus in our driveway, a Legacy and an Outback. Both are 2.5i Limiteds with CVT and black leather. Things are good.

 

I like to work on my own cars and my wife likes extended warrantees. We're covered for a while yet but at least I can get away with doing the brakes myself. My experience over the past decades has mostly been with Mercedes and a little Toyota pickup. I am relatively new to Subaru but always found them interesting.

 

This morning I was looking at the brakes on my Legacy planning on replacing the rotors and pads sometime soon. My question is what is the easiest way to tell which brakes I have on my car? Dealer parts websites list brake parts for both "16" and "17" based on the wheel size. My wheels are 17" but these brakes could still be the ones for 16" wheels. The rear rotors are non-vented. I guess vented rears come with GTs and 3.6Rs. Is there a marking on the front caliper or rotor that would tell me for sure if it is 16 or 17?

The part prices for the 16 and 17 fronts and vented and non vented rears are all the same --but I think I'd have to swap calipers and carriers as well as rotors and pads. I don't think I'm ready to do that just yet as what is there now works just fine for my use right now.

Edited December 31, 2016 by colinmi

[1 Lucky Texan]

I may not be able to help much with the ID issue, but I'm jumping in to suggest you keep the rotors if possible. If they are in OK condition and above the minimum thickness stamped on them, keep them.

 

Of course, if they are untrustworthy slabs of rust, that's a different issue. Subaru OEM rotors are fine quality.

[colinmi]

Thanks for the response.  The rotors still do look pretty good yet and I was just getting a look at them so I know what to get when they do need replacing.  I would most likely stick with factory rotors.  They do seem to be good and are attractively priced.  When I do replace them I was thinking of possibly upgrading from 16s to 17s and to vented in the rear, both with factory parts.  Having to replace calipers and brackets also to do that will probably dissuade me from doing that too soon.  Right now my mot immediate question is how to tell if my front brakes are the ones for the 16" or 17" wheels.  The Tokico  front caliper is stamped with a 12 and WF (or E).  The rear is stamped 21W.  Do these markings indicate size or just some kind of production number?

[colinmi]

Here is a picture of the front caliper.

Edited January 1, 2017 by colinmi

[idosubaru]

Stop I'm or email or call online parts dealsrt and ask them to look it up by VIN number.

 

Look up pics or in auto parts store or in Subaru dealer andncompare the twonpads and note the differences.

 

Replacing rotors is pointless. The rears routinely last the life of the vehicle, like literally 300,000 miles without blinking.

 

Fronts don't need replcing until they vibrate while braking. That shouldn't happen if your slides and clips are well maintained.

 

Replacing clips and slide grease is far more preventative than replacing rotors. That's one area, at least with Subarus, where what people typically do and reality make absolutely no sense at all.

 

As long as your current brakes lock up the wheels and activate ABS then bigger brakes aren't going to offer any improvement except aesthetics , or if you're racing.

[1 Lucky Texan]

^^^ true, best braking upgrade is to run stickier tires. But some folks don't want to trade-away treadlife for that.

 

do you tow or run with max load in the car? race or bomb down mountain roads? those 'could' be issues requiring a fresh look at braking gear.

[idosubaru]

^^^ true, best braking upgrade is to run stickier tires. But some folks don't want to trade-away treadlife for that..

 

gotcha - but the stock brakes lock up the wheels and activate ABS, bigger brakes can't "lock them up more" on an average daily driver right?

[Numbchux]

+1 on VIN lookup. If you want to PM me the last 8 digits of your VIN, I can give you the OE part numbers.

 

 

gotcha - but the stock brakes lock up the wheels and activate ABS, bigger brakes can't "lock them up more" on an average daily driver right?

 

This is not really true. While you are correct, the coefficient of friction of the tires to the road is a relatively fixed variable, and if you can overcome that, you cannot apply any more force to them.

 

 

However, in practice, it's not quite that simple. Larger rotors mean that the speed that the rotor friction surface passes the pads is higher, also the larger rotor gives a longer lever arm against the rotational force of the wheel (friction point is further away from the fulcrum). These 2 factors give more control below that limit of locking up the tire. So while the theoretical maximum amount of force is fixed, the driver can better utilize the area underneath that point.

 

I upgraded from a 160mm front rotor to a 180mm on my mountain bike a couple years ago. Same caliper, same pads. Just rotor and caliper bracket. The difference was huge! 

 

 

The extra mass of the larger rotors also means that they have more thermal mass, meaning it takes more energy to overheat. This is why vehicles with a higher cargo capacity have larger rotors (Outback vs Legacy). Ditto with vented rotors vs solid. Most people won't overheat the stock stuff on the road, but if you're towing or hauling, it's possible.

 

The extra mass is a double-edged sword in itself. Extra mass means more rotational inertia, which means it takes more force to get them to change speed. Meaning more power to accelerate (this will hurt your city fuel mileage). But it also means that they are harder to stop abruptly (like a lock-up). It's also more unsprung mass, which makes the suspension slightly less effective, but that's pretty minor.

 

 

 

I have a theory that a braking upgraded can also help keep the tires in the area of the friction curve above the kinetic friction variable (2 objects can apply more force just before they start sliding, i.e. static friction), and thereby utilize the existing tires better. But I've never come up with a way to truly test that actually isolates other factors....

 

 

 

Brake upgrades also offer a factor of braking "feel". Which sounds superficial, but if the brakes feel stronger, that gives the driver more confidence in them, which is a very real factor. Master cylinder bore is the perfect example of this, on paper a larger bore master gives you less leverage over the calipers, which seems like you would have less braking force. But in practice, the extra force required on the pedal is pretty minor, and the reduced pedal travel shortens the time from when your brain decides to brake, and force actually being applied, which is an excellent feeling.

Edited January 2, 2017 by Numbchux

[idosubaru]

Copy, I see.

So with light duty driving it's not going to matter - the brakes easily lock and jam the car in place.  In a high speed, steep grade/momentum situation with emergency braking maybe bigger ones grab quicker?

 

Some clear daily driver numbers would be nice to see when bumping up the rotor size. 

[colinmi]

Thank you for the responses.  Right now the brakes are very good but I may appreciate some larger ones sometime in the future.  Brake components will eventually need to be replaced with use and age so if the upgraded parts are the same price as the existing configuration, there's not much of a downside to getting them besides losing the option of mounting 16" wheels.  This is the way I'm thinking.  The car has about 73k on it and I am planning ahead.

 

I have not spoken to a dealer on the phone yet but a few dealers that list online use the VIN in the website search show both the 16 and 17 options as well as vented and unvented for the rear.  They are showing what will fit rather than what actually came on the car.