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Old 09-10-2005, 07:12 PM   #1
CharT
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Default Legacy GT front brake weights. Yikes!!!

I recently bought some nearly new Legacy GT front brakes to upgrade my WRX. I already have the 290mm solid rear rotors and really liked the improvement. However, my front brakes kept fading at the track with Carbotech Panther XP pads and ATE Super Blue fluid. I don't have any ducting and never got around to removing the dust shields. The Legacy GT front brakes looked like just the ticket for me due to relative low cost and OEM reliability. No pad knockback with the floating caliper design and dust boots on all the pistons, etc.

Anyway, I weighed the parts on my digital bathroom scale and got these numbers:

1 pair, new, Legacy GT front rotors 43.8 lbs (21.9 lbs ea.)
1 pair, new, calipers with stock pads and brakelines 31.8 lbs (15.9 lbs ea.)

1 pair, used, WRX front rotors 28 lbs (14 lbs ea.)
1 pair, used, calipers with Bobcats and stock brakelines 27 lbs (13.5 lbs ea.)

I remember reading somewhere that the stock WRX front rotors were just 14.5 lbs, so there's an addition 7.5 lbs per corner just from the rotors! Does this sound right? I'm worried about negative effects from the increase in rotational and unsprung weight. Does anyone know what a Stoptech BBK rotor weighs? I already know that their aluminum calipers are lighter than stock. I will weigh my stock parts coming off the car later today and post those numbers as well.

After weighing everything, it looks like I added 10.3 lbs to each front wheel with the new and larger rotors/calipers. Good thing my wheels are probably 2-3 pounds lighter than stock!

Edit: Finally done! Added WRX stock weights.
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Last edited by CharT; 09-10-2005 at 11:59 PM.
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Old 09-10-2005, 08:49 PM   #2
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From other members I know who have experience with WRX's (wagons specifically) and track days, you are going to have fade unless you have one of the massive brake kits on there. Talk to Lowball and Egan over on I-club.
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Old 09-11-2005, 12:56 AM   #3
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Thanks for weighing them, I was curious what the differences are. I didn't think they were that much heavier.

A 2-piece rotor designed to be used with the stock LGT caliper would be great. I wonder if anybody makes them or is planning to...would be a hot seller I think.
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Old 09-11-2005, 01:44 AM   #4
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I found these, which claim to take about 6 lbs off the stock rotors. They're real pricey, though.

http://legacygt.com/forums/showthrea...ghlight=rotors
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Old 09-11-2005, 01:57 AM   #5
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Kostamojen,

I agree with you. The Legacy GT front rotors are 22mm larger in diameter and 6mm thicker than my WRX rotors. As you can see from the weights I posted, it's over 7 lbs more material than the WRX rotors. It basically is "one of the massive brake kits" with OEM reliability and a fantastic price.
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Old 09-11-2005, 05:27 AM   #6
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I think stoptech 328x28 rotor weighs in at around 13-14 lbs
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Old 09-11-2005, 02:38 PM   #7
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Wow, you're not kidding...those iON rotors cost an arm and a leg.

Stoptech makes direct replacement 2-piece rotors for some applications, but I don't see Subaru listed. Time to bug the hell out of them, although these won't be cheap either.
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Old 09-11-2005, 10:53 PM   #8
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If your brakes are fading, a increase in weight is a small price to pay

BTW I just got back from a two day PCA event w/ four pots front/two pots rear- DS3000's front/2500 rear, DBA two piece rotors front and all was very good

I do have the following for ducting- first I put in the oe lower plastic pieces (that used to come standard w/ the 02's)- they take some fabbing to fit w/ the 04+'s but not bad. Second I removed the front dust shields, Third I fabbed a setup to run from my fog location to the wheel well. Fourth I fabbed some "deflectors" to go on the control arms to help direct air into the rear of the rotors.

Those have helped no doubt, while the rotors were still running pretty hot- they weren't melting the adhesive on the wheel weights like previous track days.

It's not easy to stop a 3100 lb car!
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Old 09-12-2005, 02:18 AM   #9
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Did you also measure the weight of just the calipers, or the weight of the lines and pads separately?
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Old 09-12-2005, 03:04 AM   #10
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Sorry, don't have separate weights. The front brakelines from the Legacy GT look identical to the ones from the WRX, so they pretty much cancel out. My bathroom scale isn't very accurate at such low weights anyway. The Legacy pads might be about half a pound more than the WRX pads; just a guess.

Last edited by CharT; 09-12-2005 at 03:11 AM.
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Old 09-12-2005, 03:09 AM   #11
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BigSky,

I can't wait to try these brakes at the track. Now, I have to decide what pads I want to use. Since I only have one set of 17" wheels to fit over the brakes, I'm stuck with summer street tires instead of R-compounds. I've been mostly a Carbotech fan, so I don't know much about other pads. I'm guessing the XP series are too agressive for anything other than R-compounds. The Bobcats are more of a street/autox pad. That leaves the Panther Plus. I just hope I don't regret not going to the XPs!

What tires did you run and are those Ferodo(?) pads you also use for the street or swapped in just for the track?
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Old 09-12-2005, 05:48 AM   #12
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I've run Panther XPs with street tires (Toyo T1-S) and they were fine.

As for your bathroom scale technique, try weighing yourself with the parts and without the parts, and then subtract. That way you're using the scale in its "optimum" range, rather than trying to read 5# on a 300# scale.

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Old 09-12-2005, 10:26 AM   #13
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I'm on street tires (S02's)- I swap the 3000's up front for track and run 2500's on the street.

I know of several guys also that have also run the XP's w/ street tires- no problems.
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Old 09-12-2005, 03:35 PM   #14
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Pat,

That's a good technique. I thought I'd minimize error by weighing two parts and dividing by two. I can just see myself doing step aerobics with a rotor under each arm, stepping on and off the scale to get multiple measurements!

I'm a little worried about front bias if I go to XP in front, which have a mu of something like .60 and Bobcats in the back with a mu of .45. The Panther Plus is around .55 or so. I'm starting to think I may need to swap pads on all four corners for the track. This is turning into a bit of a hassle. If there's a lower mu track pad with high operating temps, that might be more ideal for my setup in front.

Last edited by CharT; 09-12-2005 at 03:42 PM.
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Old 09-12-2005, 05:39 PM   #15
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CharT,
The PantherPlus are the pads to have for track and some street duty.

As for the unsprung weight bit, you won't notice it really unless the car is absolutely tweaked to the max. I ran a well-prepared STX car and did not notice a significant drop in performance due to the brakes going from stock to the LGT setup. (Mine was the test car.)

I did notice some rotational inertia increases and thus the car didn't feel quite as quick. But it would definitely stop time and again without fading issues. And that was on the stock pads as nothing else had been developed for the LGT's brakes at that time.

For simply wanting to get rid of heat and decrease fading by a significant amount, the adding of mass is the easiest way to get it. To add mass AND increase heat dissipation ability...well that costs the big bucks just like lightweight wheels.

-Biggly
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Old 09-13-2005, 11:04 AM   #16
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Hey, remember that you want weight on your rotors!

You get greater heat capacity by having more iron in your rotors. More iron means more weight. The only exception would be the hat section - this is where you can reduce weight without sacrificing heat capability. (That's where the two piece rotors have an advantage.)

All else equal, two rotors of equal weight will have the same heat capacity. Your quick weighing merely verifies that the Legacy GT rotors are indeed higher heat capacity than stock WRX rotors.
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Old 09-13-2005, 11:53 AM   #17
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It's the heavy iron caliper and lack of aftermarket pads that make the kit questionable - otherwise it is a great upgrade. A fixed caliper would have been nice too
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Old 09-13-2005, 12:11 PM   #18
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Quote:
Originally Posted by infantsam
It's the heavy iron caliper and lack of aftermarket pads that make the kit questionable - otherwise it is a great upgrade. A fixed caliper would have been nice too
Questionable if one's only goal is to minimize weight yes.

It's about the same price as the 4pots (I believe) for one of these kits yet it has a much larger fade resistance. The 4pots are really more about pedal feel and brake modulation.

OEM quality stuff that's more heavy duty. It's tough, will last a long time, and isn't going to be something bizarre if a mechanic has to do something on the vehicle.

-Biggly
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Old 09-13-2005, 12:22 PM   #19
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Quote:
Originally Posted by DrBiggly
Questionable if one's only goal is to minimize weight yes.

It's about the same price as the 4pots (I believe) for one of these kits yet it has a much larger fade resistance. The 4pots are really more about pedal feel and brake modulation.

OEM quality stuff that's more heavy duty. It's tough, will last a long time, and isn't going to be something bizarre if a mechanic has to do something on the vehicle.

-Biggly

Agreed..fade resistance is definitely increased

Whats the cost compared to the Brembo STi kit?? Nets you aluminum fixed calipers and SS lines also. Fits the other requirements as well.
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Old 09-13-2005, 12:33 PM   #20
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Orson,

You make great points. What's interesting to me is that all of the lightweight two-piece replacement rotors for the LGT are thinner than stock! The LGT OEM rotors are 30mm thick while the two-piece aftermarket rotors are 28mm. I guess the aftermarket rotors are directionally vaned, which help with cooling. Losing 2mm of rotor thickness reduces weight, but I wonder what the net effect on overall heat capacity is when you take into account the directional vanes.

On a side note, has anyone that did this upgrade noticed an increase in initial pedal travel? The piston sizes are the same as before, so I should have the same pedal feel and travel except more brake torque. I definitely notice the increased brake torque as pedal effort is much reduce, but seems like I have more initial travel before the brakes start to grab. Could there be some air in the lines? Or the difference between OEM LGT brake pads and the WRX Carbotech Bobcats I used to run?
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Old 09-13-2005, 12:35 PM   #21
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Quote:
Originally Posted by infantsam
It's the heavy iron caliper and lack of aftermarket pads that make the kit questionable - otherwise it is a great upgrade. A fixed caliper would have been nice too
Actually, I get my choice of the full line-up of Carbotech pads. There are a few other manufacturers that make LGT pads, but I don't really pay much attention to those. For street/autox you can use Bobcats, for street/track you can use Panther Plus, for track there's Panther XP, etc.
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Old 09-13-2005, 12:52 PM   #22
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Quote:
Originally Posted by CharT
Orson,

You make great points. What's interesting to me is that all of the lightweight two-piece replacement rotors for the LGT are thinner than stock! The LGT OEM rotors are 30mm thick while the two-piece aftermarket rotors are 28mm. I guess the aftermarket rotors are directionally vaned, which help with cooling. Losing 2mm of rotor thickness reduces weight, but I wonder what the net effect on overall heat capacity is when you take into account the directional vanes.

On a side note, has anyone that did this upgrade noticed an increase in initial pedal travel? The piston sizes are the same as before, so I should have the same pedal feel and travel except more brake torque. I definitely notice the increased brake torque as pedal effort is much reduce, but seems like I have more initial travel before the brakes start to grab. Could there be some air in the lines? Or the difference between OEM LGT brake pads and the WRX Carbotech Bobcats I used to run?
I'd rebleed first to rule that out

Perhaps the Bobcats are less 'grabby'

Or there is more compliance in the floating caliper than the WRX setup
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Old 09-13-2005, 01:40 PM   #23
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My track pad setup was always track duty pads in the fronts only, street pads (Mintex 1155s) in the rear. I guess technically I was giving up some braking performance and monkeying with the f/r bias of the system, but it worked just fine and the rears never seemed to get worked enough to require better pads.

Pat
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Old 09-14-2005, 01:16 AM   #24
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I'm curious, does the LGT come with upgraded bearings? CharT mentioned no pad knockback issues with his setup, but what about the much higher heat capacity of the LGT rotors on a WRX turning the bearing grease into hot margarine or milk (on track days of course)?

This is an extreme example, but I find it striking that Gary Sheehan can waste the stock bearings in one race (stock rotors) but with 2-piece aluminum hat rotors the bearings last a season.
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Old 09-14-2005, 02:11 AM   #25
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A higher heat capacity doesn't mean higher temperatures. The rotor will be able to absorb more heat before the temperature of the rotor increases. Actually, that's what heat capacity is. It's the amount of thermal energy that can be absorbed before there is an increase in temperature.
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