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Registered
2004 Sube slushy
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566 Posts
Discussion Starter #1
So do upgraded rotors make a difference over stock? Stock econobox brakes really suck-perhaps the worst aspect of the XT.
 

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2010 dodge caravan auto
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1,748 Posts
slotted and drilled make a differance dont heat up as fast. or get stock and drill them your self.
 

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2004 Sube slushy
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566 Posts
Discussion Starter #3
I guess the master cyl swap would make a better upgrade since the pedal fell like stepping in a dog pile. SS lines might help a little also although I'm dubious about that.
 

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'03 XS MT PSM
2015 Ford Focus ST
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2,371 Posts
master cylinder would probably be the best shot at fixing the pedal feel. Stainless line help, but not a whole lot. Would swapping the master cyl of the Forester with one from a WRX or Legacy disrupt the ABS at all?
 

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Premium Member
98 Forester...what else
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5,714 Posts
You should really look at the other aspects of the braking first, and see what you can do to improve that before going with rotors.

1. Tires - Contrary to popular belief, brakes don't stop you, tires do. If I placed OEM tires on Subed (who's equipped with Brembo STi front brakes and Legacy rear upgrade), and equipped you with a really good set of sticky R compound tires, I think we'd be pretty close on who'd stop first.

2. Stainless lines - Hydraulic lines work on the principle of fluid expansion (simply put), and you have rubber (expandable material) lines leading to your brake calipers. Eliminate the ability for your lines to expand (s.s. lines), and the fluid will be able to compress the piston that much harder.

3. Brake pads - the OEM brake pads are okay for your average driver around town who isn't pushing the performance envelope of their vehicle. If you want better initial bite, you need to get a compound which creates more friction. You also want pads which won't glaze over or overheat and lose their effectiveness.

If you still need rotors after that, I can get you most of the different styles and varieties of rotors on the market. Let me know.
 

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Premium Member
2004 Forester XT MT
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1,433 Posts
There are different elements that can be improved:
Rotor Material = releases heat better, sometimes lighter
Vane Design = increased air flow draws heat away from the face of rotor
Slotted Face = clears the pad surface
Two-Piece = lighter and minimizes heat transfer to hub/wheel

Crossed drilled rotors are mainly bling. They are not a good idea due to the inevitable cracks which initiate at the drilled holes.

Here is a pretty nice example of an awesome one-piece slotted rotor. (You can ignore the crossed drilled one since it's not designed for track use.)

http://www.dba.com.au/DBA4000series_specs.pdf

You can buy them here:
http://subydude.com/osc/product_info.php/products_id/504?osCsid=e5fd49a53273700c17ad28cd30a9d326
 

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The Modfather
2019 Impreza 5dr Sport - Manual
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8,052 Posts
Lots of brake info here:

http://www.scoobymods.com/forums/showthread.php?t=1122

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Cut and past about rotors:

Cross-drilled and Slotted Rotors


Cross-drilled rotors:
Disks that have been drilled through with a non-intersecting pattern of radial holes. The objects are to provide a number of paths to get rid of the boundary layer of out gassed volatiles and incandescent particles of friction material and to increase "bite" through the provision of many leading edges. The advent of carbon metallic friction materials with their increased temperatures and thermal shock characteristics ended the day of the drilled disc in professional racing. They are still seen (mainly as cosmetic items) on motorbikes and some road going sports cars. Typically in original equipment road car applications these holes are cast then finished machined to provide the best possible conditions by which to resist cracking in use. But they will crack eventually under the circumstances described in another section (see Cracking). Properly designed, drilled discs tend to operate cooler than non-drilled ventilated discs of the same design due the higher flow rates through the vents from the supplemental inlets and increased surface area in the hole. That's right, inlets, the flow is into the hole and out through the vent to the OD of the disc. If discs are to be drilled, the external edges of the holes must be chamfered (or, better yet, radiused) and should also be peened.



Slotted:

Shallow, sharp edged but radiused bottom grooves milled into cast iron discs to provide leading edges for bite and a path for the fire band of gases and incandescent friction material to be dissipated through. If the slots fill up with pad material, the system is operating at too high a temperature.

For the track they work. Not as dramatically as the ads will lead you to believe, but they do a good job of keeping the pad surface "clean" when they get really hot and they do a good job of venting gases. Again though, with modern pads neither of the issues mentioned are that severe now a days.


2-Piece rotors

I have seen a lot on 2-piece rotors. Some of the information contained in them is correct some is mythical.

Some definitions.

2-Piece rotor: A brake disc rotor that has a separate hat (cap) usually made from a lightweight metal. There are two types of common 2-piece street rotors. One uses a bolted hat and the other a pinned hat (also known as a "floating rotor" design).
The bolted type is just what it sounds like. Usually an aluminum hat bolted to a cast iron rotor. The only real benefit of this design is weight savings. However, weight savings tend to be only 10-20%, all else being equal, but with a 50-75% price increase.
The pinned type has usually stainless steel pins that attach the aluminum hat to the rotors. This allows the rotor to "float" on the pins. The great advantage of this design is that it allows the rotor to move freely. When the rotor expands and contracts there is much less chance of binding or distortion. As you can imagine this cuts down on warping and uneven wear (DTV). The disadvantage of this design is really high costs and increased NVH.

As far as better heat conduction, not really. It does help a bit, buts it's not enough to make it worth the extra cost. The nice think about the weight savings is you can get a larger rotor with out taking a weight penalty.

- It may help keep your wheel bearings cooler.

My opinion:
2 piece floating (pinned) rotor is worth every penny. This is good technology, yeah they cost a ton but they do the job. They keep the rotor even through out operating temperature range and they keep down DTV problems better than anything I've ever seen. Be sure they're the pinned hat type and not the bolted hat type.

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2004 Sube slushy
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566 Posts
Discussion Starter #8
So I guess then that drilled, slotted, dimple and any aftermkt rotor is no better than stock for normal driving save for the floaters...
 

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1998 Forester "S" lifted. Bog-o-matic
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2,006 Posts
If you just want better pedal feel why not get a brake master cylinder bracket?
 

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2004 Sube slushy
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566 Posts
Discussion Starter #10
Ahh, because I knew diddly about until now...

I'm also looking into the H6 rotor conversion. Anyone done it?
 

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Administrator
2004 Forester XT Premium 4EAT
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29,458 Posts
I've got the H6 rotors in the rear. They balance out most any brake upgrade you do to the fronts, including a BBK. Most recommended!
 

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Premium Member
2004 Forester XT MT
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1,433 Posts
Jeffn said:
So I guess then that drilled, slotted, dimple and any aftermkt rotor is no better than stock for normal driving save for the floaters...
I suppose.

There have been mixed opinions about the floating type of two piece rotors. Some argue that once the rotor heats up the different materials would create a situation where the rotor will be able to shift and become eccentric.
 

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2004 Sube slushy
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566 Posts
Discussion Starter #13
I guess my original intent came from our adding drilled aftermkt discs to our svx's which are greatly under-rotored from the factor(heaviest Sube built till then-they didn't calculate for the weight) and the stronger aftermkt rotors never had warpage problems liek the factory's.

The XTs frisbees feel warped and wobbly already at 17k and I wonder what the same size aftermkt ones would feel like.
 
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