LittleBlueGT Posted April 18, 2007 Share Posted April 18, 2007 The Front and Rear Legacy Stoptech Kit w/ an upgraded suspension is very close to full lock-up front and rear at the same time. I found this out during bed-in while braking in a slight turn.... If it had been too rear-biased, I would have swapped ends. Too front biased and I would not have continued slowing down at the same rate as the rear lightened and started to swing No ABS intrussion during the above maneuver Ted Nice. Let me know what it is like on ice. Full tune of 68HTA, KSTech 73 MAF, Racer X FMIC and ID1000s................by the DataLog Mafia!!! Link to comment Share on other sites More sharing options...
praedet Posted April 18, 2007 Author Share Posted April 18, 2007 I will, and by the way. Using my VERY specialized weighing device, (My hands and my wife's hands ) we agreed that the Stoptech front caliper is about 3-4 lbs lighter than the stock front caliper. The 332x32mm rotor is about 1-2 lbs lighter than the stock front rotor, or about 4 lbs heavier than the iON 2-piece stock sized rotor. The Stoptech rear caliper is right around the same weight as the rear stock caliper, and the 328x28mm rear rotor is about 1 lb lighter than the stock rear rotor... So, 4-6 lbs saving per front corner, and rougly 1 lb per corner rear savings Ted Link to comment Share on other sites More sharing options...
LittleBlueGT Posted April 18, 2007 Share Posted April 18, 2007 I will, and by the way. Using my VERY specialized weighing device, (My hands and my wife's hands ) we agreed that the Stoptech front caliper is about 3-4 lbs lighter than the stock front caliper. The 332x32mm rotor is about 1-2 lbs lighter than the stock front rotor, or about 4 lbs heavier than the iON 2-piece stock sized rotor. The Stoptech rear caliper is right around the same weight as the rear stock caliper, and the 328x28mm rear rotor is about 1 lb lighter than the stock rear rotor... So, 4-6 lbs saving per front corner, and rougly 1 lb per corner rear savings Ted 4-6 lbs!!!!!!!!!!! Nothing my friend, nothing! Full tune of 68HTA, KSTech 73 MAF, Racer X FMIC and ID1000s................by the DataLog Mafia!!! Link to comment Share on other sites More sharing options...
praedet Posted October 25, 2007 Author Share Posted October 25, 2007 I added the WRX Stoptech kit to the calculations. I do not recommend this kit as you will drastically shift bias to the rear... I have not changed the stock rear bias calc yet. This is for two reasons. One, all the manuals I have read show a 38.1 mm piston, not 32 mm. If it is 32 mm, the bias on this car is more front oriented than any production car I have been able to track down. That leads me to the conclusion that either both front and rear piston sizes are off, or the two rear calipers that were measured were wrong... Anyway, I will update if we find out more... Link to comment Share on other sites More sharing options...
edmundu Posted November 1, 2007 Share Posted November 1, 2007 I just had a chance to measure the rear LGT caliper's on a bone stock '06 GT, and they indeed were 32mm! Link to comment Share on other sites More sharing options...
fweasel Posted November 1, 2007 Share Posted November 1, 2007 well that changes things. ignore him, he'll go away. Link to comment Share on other sites More sharing options...
zildjiank Posted November 1, 2007 Share Posted November 1, 2007 I added the WRX Stoptech kit to the calculations. I do not recommend this kit as you will drastically shift bias to the rear... Glad you're telling people ...cause it definitely is NOT made for the Leggy, that's why stoptech has made a specific Leggy kit. Link to comment Share on other sites More sharing options...
fweasel Posted November 2, 2007 Share Posted November 2, 2007 ...cause it definitely is NOT made for the Leggy Several people are running it on the Legacy platform with positive results. Also, thos calcualtions were made with what now appears to be possibly an incorrect stock rear piston size. ignore him, he'll go away. Link to comment Share on other sites More sharing options...
zildjiank Posted November 2, 2007 Share Posted November 2, 2007 Several people are running it on the Legacy platform with positive results. Also, thos calcualtions were made with what now appears to be possibly an incorrect stock rear piston size. Positive pedal feel is probably more like it. But when I called Stoptech, the guy there specifically told me not to buy the WRX kit, b/c they are specifically designed for that car. Not saying you won't see any "positive gains" or anything, I just think you'll see much better benefits if you go with the one designed for our car (since the piston sizing differs from the wrx kit to the Legacy kit). Just throwing it out there that the wrx kit is indeed the wrx kit, and just b/c it fits does NOT mean its specifically designed for the legacy... Link to comment Share on other sites More sharing options...
praedet Posted November 2, 2007 Author Share Posted November 2, 2007 I will put in the new calcs for the 32mm rear... Something seems off, but maybe the EBD has a slightly different effect than we though too Can someone who still has some OBXT rear calipers measure their piston size? If it stays 38.1 mm, the OBXT has a better bias from the factory Link to comment Share on other sites More sharing options...
edmundu Posted November 17, 2007 Share Posted November 17, 2007 Well, I needed to check my rear pads, and while I didn't remove the claiper's to get a completely accurate measurement, I did eyeball it, as well as measure the piston imprint on the backing plate. It came out to about 35mm, close enough to 36mm, that I think the factory quotes on the STI BRembo's seem to be accurate. After recently driving a stock LGT equipped car, and then immediately stepping into my car, it was evident that there was more braking action coming from the rear on my car. IT just hunched down and stopped much better..... Link to comment Share on other sites More sharing options...
Guest Posted December 21, 2007 Share Posted December 21, 2007 I respectfully disagree. The pads have alot to do with braking capability. If they didn't then you would only need to increase piston size. Which in of itself will only allow a higher pinching point, but put thru the same size pads, and it results in almost identical braking. Except the larger psitoned caliper's will be able to lock up the wheel that much easier. There's a reason why swept area has everything to do with pad size & rotor size, and not with piston size. A cars ultimate braking capability lies within the whole package, and basing that solely on piston area and rotor size isn't telling the whole story. I have had a few of the mentioned combo's, and the addition of the rear brembo's, clearly gave more bias to the rear. It was felt in the seat, by the additional pulling from the rear. So was this ever settled? Link to comment Share on other sites More sharing options...
Guest Posted January 16, 2008 Share Posted January 16, 2008 The pistons in the rear calipers on both my 05 and 06 GT's are 32mm, FWIW. (did you guys get the headphones?) So we determined that rear stock piston is not 38mm. Pradet - could you update the thread as it provides wholly incorrect information wrt stock vs. BBK bias? Link to comment Share on other sites More sharing options...
praedet Posted January 16, 2008 Author Share Posted January 16, 2008 I will, give me some time as it is not a small task... Link to comment Share on other sites More sharing options...
TSiWRX Posted January 16, 2008 Share Posted January 16, 2008 ^ Dude, assign it to one of your students for extra-credit! <-- I love Winky, my "periwinkle" (ABP) LGT! - Allen / Usual Suspect "DumboRAT" / One of the Three Stooges '16 Outback, '16 WRX, 7th Subaru Family Link to comment Share on other sites More sharing options...
BlackHole Posted January 22, 2008 Share Posted January 22, 2008 The pad height does not affect the actual force the brakes exert because only the piston has fluid behind it. ...In actually, the higher radial height can hurt the total torque of the set-up because that meas the pistons might be closer to the hub, so the moment arm is smaller. I think you are getting two things slightly confused: yes the piston applies the torque but the pad height does affect the force applied exactly for the reason you stated: Radial pad height is needed for torque calcs since effective rotor diameter = nominal diameter - radial pad height. It's a reasonable assumption that the piston is radially centered on the pad. This can be confirmed by looking at the brakemath.xls file referenced earlier - all of the effective rotor diameters are calculated this way. Following that logic: Stock LGT: 78.1/21.9% F/R, 1760 ft-lbs brake caliper torque STi brakes: 73.5/26.5% F/R, 1973 ft-lbs brake caliper torque LGT F/RB 316 R: 76.9/23.1% F/R, 1887 ft-lbs brake caliper torque LGT F/WRX 2-pot R: 71.8/28.2% F/R, 1912 ft-lbs brake caliper torque The rear STi set-up actually moves the bias more forward because of the MUCH smaller pistons. What you might be feeling is the more rear bias due to stiffer suspension that doesn't allow for as much dive... I would agree if the LGT had 38mm rear pistons, but mine doesn't. Assuming a 31.8 mm piston (my piston size), the STi setup is a bit less front-biased than LGT stock which jibes with experiential data. Kyle "BlackHole" Link to comment Share on other sites More sharing options...
praedet Posted January 22, 2008 Author Share Posted January 22, 2008 ^^^We are saying the same thing... The pad height can positively or negatively effect the effective rotor diameter depending on where the pistons are behind the pad. Just changing the pad size does not increase or decrease the braking force. And that comment on the STi rear was made when we thought the pistons in the rear of the LGT were the size Subaru says they are Link to comment Share on other sites More sharing options...
BlackHole Posted January 22, 2008 Share Posted January 22, 2008 Just making sure we're all on the same page. Now just for fun, on paper I tried to maximize clamping force using the stock rotors and known calipers while retaining roughly a 70/30% F/R spilt. Completely academic since I'm not about to build brackets to try this out and I don't have enough traction to use it all... F = SRT-8 calipers (44/44mm pistons) / R = Porsche 944 rear (28/30mm) 69.8/30.2% F/R, 1989 lb-ft caliper torque, about 13% more than stock. Kyle "BlackHole" Link to comment Share on other sites More sharing options...
praedet Posted January 22, 2008 Author Share Posted January 22, 2008 The interesting thing w/ this whole calculation... Now that we know Subaru made the LGT MUCH more front biased than all the other Subarus, I am wondering if EBD does a LOT more than we think. In other words, does the car actually proportion more (So instead of 1:1 F/R it starts out 1:2) to the rear to maintain 70/30 or whatever the folks at Subaru deemed "ideal" until it gets lock-up back there, and then shifts the bias forward Link to comment Share on other sites More sharing options...
LittleBlueGT Posted January 22, 2008 Share Posted January 22, 2008 The interesting thing w/ this whole calculation... Now that we know Subaru made the LGT MUCH more front biased than all the other Subarus, I am wondering if EBD does a LOT more than we think. In other words, does the car actually proportion more (So instead of 1:1 F/R it starts out 1:2) to the rear to maintain 70/30 or whatever the folks at Subaru deemed "ideal" until it gets lock-up back there, and then shifts the bias forward I would gladly do some testing to see my braking distances, but I don't know how to get repeatable and fairly accurate data. I was thinking of logging my braking, but even from high-speed our loggers don't update fast enough to be useful. (at least that is my thoughts) Full tune of 68HTA, KSTech 73 MAF, Racer X FMIC and ID1000s................by the DataLog Mafia!!! Link to comment Share on other sites More sharing options...
Guest Posted April 26, 2008 Share Posted April 26, 2008 I will, give me some time as it is not a small task... Please at least edit the list and remove the incorrect information to not confuse people if you cannot update it with proper numbers. Link to comment Share on other sites More sharing options...
robinlsb Posted April 26, 2008 Share Posted April 26, 2008 The interesting thing w/ this whole calculation... Now that we know Subaru made the LGT MUCH more front biased than all the other Subarus, I am wondering if EBD does a LOT more than we think. In other words, does the car actually proportion more (So instead of 1:1 F/R it starts out 1:2) to the rear to maintain 70/30 or whatever the folks at Subaru deemed "ideal" until it gets lock-up back there, and then shifts the bias forward Yup!!! "Belief does not make truth. Evidence makes truth. And belief does not make evidence." Link to comment Share on other sites More sharing options...
BlackHole Posted May 28, 2008 Share Posted May 28, 2008 My next brake setup: STi Brembo F / Rotora 2-pot rear (uses stock LGT rotors) 72.0/28.0% F/R, 2014 ft-lbs brake caliper torque The nice thing about this & the 06-07 WRX rear caliper setups are that the stock rear rotor can be retained (reducing cost) and actually exerts more torque than the STi Brembo rears due to the larger pistons. Stock LGT: 78.1/21.9% F/R, 1760 ft-lbs total brake caliper torque STi brakes: 73.5/26.5% F/R, 1973 ft-lbs STi F + 06-07 WRX 2-pot rear: 72.7/27.3% F/R, 1994 ft-lbs Note that these numbers are slightly different than how praedet calculated, so I've included reference setups for comparison. Any way you slice it you're still better than stock. Kyle "BlackHole" Link to comment Share on other sites More sharing options...
praedet Posted June 26, 2008 Author Share Posted June 26, 2008 All right folks, I believe this is fully updated. I think I have everything w/ the stock 32mm rear piston on the LGT and OXT. Based on what this does, I really want to find the specs on the EBD system, as I don't think Subaru is running a 1.1 Front to rear ratio during the first 20% of brake force. I think more is being proportioned backward than in most cars, and then EBD brings it back forwards as you brake harder... Anyway, good luck Link to comment Share on other sites More sharing options...
spiralsmurf Posted June 30, 2008 Share Posted June 30, 2008 so how bad would it be to shift the bias rearward a little bit by using a wrx stoptech kit? Link to comment Share on other sites More sharing options...
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