presslab Posted February 5, 2009 Share Posted February 5, 2009 Bug trucks have drum brakes but they are much bigger(actually overkill) and they also run off air. It's a little different. Take a truck driving class, it's a great way to learn about why they are used on big trucks and why they work better on big trucks and not as well on cars. Heat is the big reason!!! So are you saying you took this class? Can you elaborate as to why they work better on big trucks and not cars? Not sure if the brakes on trucks are overkill, I've smelled many truck brakes while driving over a mountain pass. Of course the trucks weigh 40 tons. I believe the original poster's problem was the brakes warping (presumeably due to heat) because of steep hills. I don't see how a rear disc would solve this problem, unless the rear disc can dissipate more heat than the drum. I use Porterfield R4S pads & shoes on all my vehicles. Not cheap, but worth it in my opinion. Quote Link to comment Share on other sites More sharing options...
bratman18 Posted February 5, 2009 Share Posted February 5, 2009 The biggest thing is that the drum brakes on trucks are built very big so that they can dissipate heat better and they can take more heat without glazing. They actually work better when they heat up a lot. Obviously any brake will start to fail if they have too much heat built up. But the little drum brakes on cars aren't designed to dissipate as much heat and when you ask a lot of them they are not going to work as well, which is why they are designed to not have a lot of braking power sent to them. Disc brakes are out in the open and have the ability to dissipate heat much quicker. Also brake fluid which is hydraulic fluid starts do break down with heat and in hard braking situations can start to feel spongy, but air doesn't work that way, it can take as much heat as you want to give to it and yes it will expand, but that only increases it's braking power. Yes I did take the class a while back and because a huge part of the test is air brakes, you have to learn all about them and about all types of brakes. I'm not flat out disagreeing with you but there is a lot to look at when talking about the differences between disc and drum brakes. Quote Link to comment Share on other sites More sharing options...
The Dude Abides Posted February 5, 2009 Share Posted February 5, 2009 I recomended the rear disk swap because it sounds like because of the steep inclines he faces daily hes useing the brakes alot. With the back brakes being drums and somewhat flawed and inferior. I suggested going with disc brake swap because he will have less wear and tear on his front brakes doing the job buy themselves when he has a good set of rear disc brakes to help along and disperse some of the work. I never feel the rear brakes on my loyale grab its always the front. Quote Link to comment Share on other sites More sharing options...
PoorManzImpreza Posted February 6, 2009 Share Posted February 6, 2009 or.. you can go crazy like I am and 5 lug your car then install jdm 2004 wrx 4pot/2 pot brakes all round and scare the *************** out of yourself everytime you hit the brakes... I haven't managed to fade these brakes yet..in fact it takes a few descent stops just to warm up the pads I've driven very aggressively and having gotten home where my stock setup would have been smoking, stinking and glowing on the four pot setup I can still put my finger on the caliper and hold it there for 5 seconds... my stock setup was: rebuild front and rear calipers new FHI rotors at the front turned rotors at the rear ebc green stuff legacy pads in the front stock fhi pads in the back fresh dot 4 fluid and kumho ecsta MX tires on 15" Pug alloys My current setup is: JDM WRX FHI four piston calipers on the front JDM WRX FHI Two piston calipers on the rear Powerslot rotors front slotted unknown brand JDM rotors on the rear Hawk HPS pads all round Castrol GTLMA Synthetic brake fluid and toyo proxes R888 tires on 17" JDM WRX wheels This is NOT a simple swap, but as I said I'm crazy.. Kaz Quote Link to comment Share on other sites More sharing options...
presslab Posted February 6, 2009 Share Posted February 6, 2009 or..you can go crazy like I am and 5 lug your car then install jdm 2004 wrx 4pot/2 pot brakes all round and scare the *************** out of yourself everytime you hit the brakes... I haven't managed to fade these brakes yet..in fact it takes a few descent stops just to warm up the pads I've driven very aggressively and having gotten home where my stock setup would have been smoking, stinking and glowing on the four pot setup I can still put my finger on the caliper and hold it there for 5 seconds... That sounds pretty nice! My pads need warming up as well; I need to really pay attention on the first couple stops, or else I'd end up in the middle of the intersection. Do you have a stock M/C? I still have stock calipers but even with stainless braided hoses the pedal was soft. I upgraded to a 1-1/8" SVX M/C and it was solid like a rock! However, there wasn't quite enough assist. There wasn't enough room for a 9" RS single stage booster but a Legacy 7"/8" tandem booster fit fine. It feels awesome now, I can lock the brakes up without any problem (once warm ), and the pedal is very solid with a good feel. Quote Link to comment Share on other sites More sharing options...
abog Posted February 6, 2009 Share Posted February 6, 2009 A properly working drum brake system will have comparable stopping power when compared to discs. The main difference is that typically drums are not adjusted properly and not working up to their potential. Secondly the heat dispersion of drum brakes is inferior to that of discs. Drum brakes are much more prone to heat related fade, so in high useage drums do not compare. Drilled and slotted rotors do work well in extreme or race situations. The normal street driven automobile will see no benefit from these rotors. To sum it up , a rear disc conversion , and high quality pads all around will give you the best braking for spirited driving, without breaking the bank. Large trucks and air brake systems are a completely different formula as far as size and weight. Quote Link to comment Share on other sites More sharing options...
presslab Posted February 6, 2009 Share Posted February 6, 2009 You all are missing my point, sometimes I wonder why I try... I take it from what you all are saying, is that Subaru designed their cars with inadequate drum brakes, which somehow caused jackbombay's front rotors to warp? If the drum brakes were the problem, they would burn up and not the front, right? I really doubt Subaru designed 90/10 brake proportioning. I'm sure in good working condition all the brakes will be sharing the load appropriately, if it was 90/10 that would be unsafe! The car would take forever to stop. Either there is something wrong with his braking system, like the brakes are not working up to spec, or he is just overwhelming the entire system and he needs larger/better brakes all around. Slapping on some rear discs without fixing the underlying problem isn't the solution... Sigh... I'm done. :-\ Quote Link to comment Share on other sites More sharing options...
carfreak85 Posted February 6, 2009 Share Posted February 6, 2009 I'll say it for a third time in two days. Drilled/slotted rotors are FOR SHOW ONLY! The whole reason they were invented was to allow the gas created from heat reacting with binders in the friction material that built up as old school racing brake pads (years and years and years and years and years ago) could have a place to escape without the gas being trapped between the pad and rotor, decreasing brake performance. We no longer have this out-gassing problem with any brake pads, so the whole reason these slots/drills were invented is pointless. Except that they look cool. Secondly, Subaru might not have designed a 90/10 F/R brake proportioning valve, but you can bet it was close. Weight transfer shifts a ton of weight up front (If you really want to know I can give you the method for calculating this weight transfer to apply to your own cars). This means less traction for the rear tires and consequently, less need for rear brake power. Sorry, I just woke up and don't quite remember all that I was going to say. I took a class on chassis/suspension/brake design last quarter. I'll go check my notes and get back to you guys on what the brake balance probably is later today. Quote Link to comment Share on other sites More sharing options...
Txakura Posted February 6, 2009 Share Posted February 6, 2009 My this thread wandered around a lot... He needs new rotors anyway, right? one point that came up was the effectiveness of his rear brakes. If it was my car I'd make sure the rears were doing their job, whatever they are. This is a good time to do a 4 way brake job to make sure there is no extra stress on the front. If money is an issue, I'd work on the rear and put up with the front for a bit more. Buy a nice semi-metallic shoe for the rear, replace the rear wheel cylinders, have the drums turned if they need it, have a surface pass done if nothing else... bleed your brakes until the fluid comes out clean, get all that old crap out of the line, when your reservoir is low, carefully clean all the crud out of the bottom. I can't speak for Brembo's. I'd buy a nice slotted rotor with a warranty against warping, there were a lot of valid points made in the thread about that being overkill, or not even useful... perhaps your wicked hill really is extreme enough to need something extra. If you can afford it, do it. If nothing else they will shed water better. Watch your lug nut tension, use a torque wrench to make sure they are all properly uniform. I spend 4-5 hours a day going from 30-0, 45-0, and 60-0 using my Loyale for a delivery route. I haven't warped my rotors yet, but I could do it pretty easily, our area is nothing but crazy hills. I just re-did my rear (drum) brakes and the overall effect on the car was amazing - it is much happier and more balanced, instead of feeling everything rush to the front it feels more like it is hunkering down and squatting on all fours. I've been looking at this myself: all their stuff is warranteed http://brakeperformance.com/site/brake_rotors.php?ad=google&gclid=CI_86dO2jZcCFQ0xawodCWcmow one final crazy thought, I just played with re-wiring my (1990 ea82) turn signals and corner markers. I don't necessarily need the hole in the front bumper for the oem signals, I'm using them as parking lights now. That bumper cut out, and the nut plates for the light housing would make a perfect duct location to bring air into the wheel well. It would be easy to make a collector*, duct and outlet in the inner (plastic) wheel well liner that blew air from the bumper toward the rotor from the inside of the well... do I "need" that? no. do I "need" half the mods on this bbs? no. but it is fun to make these things as an excercise in creativity and to enjoy our cars isn't it? *afterthought, hell use the light housings themselves as the collector, mmmm I sense another photo essay coming on Quote Link to comment Share on other sites More sharing options...
presslab Posted February 6, 2009 Share Posted February 6, 2009 (edited) I'll say it for a third time in two days. Drilled/slotted rotors are FOR SHOW ONLY! The whole reason they were invented was to allow the gas created from heat reacting with binders in the friction material that built up as old school racing brake pads (years and years and years and years and years ago) could have a place to escape without the gas being trapped between the pad and rotor, decreasing brake performance. We no longer have this out-gassing problem with any brake pads, so the whole reason these slots/drills were invented is pointless. Except that they look cool. Secondly, Subaru might not have designed a 90/10 F/R brake proportioning valve, but you can bet it was close. Weight transfer shifts a ton of weight up front (If you really want to know I can give you the method for calculating this weight transfer to apply to your own cars). This means less traction for the rear tires and consequently, less need for rear brake power. I agree, drilled/slotted rotors are pretty much for show. Maybe if your pads are literally burning/smoking they might provide a small benefit. The brake proportioning valve only reduces rear braking under near lock-up conditions; otherwise it is passive. I think what is more pertinant to this discussion is the static brake proportioning for normal braking conditions. This is determined by how much force each brake applies for a given line pressure. It depends on things like caliper piston size, pad area, pad composition, rotor diameter, drum leverage ratio, etc., etc. The attached pic is from the FSM for the XT. It shows the master cylinder pressure vs rear brake pressure. Edited February 6, 2009 by presslab Quote Link to comment Share on other sites More sharing options...
PoorManzImpreza Posted February 6, 2009 Share Posted February 6, 2009 That sounds pretty nice! My pads need warming up as well; I need to really pay attention on the first couple stops, or else I'd end up in the middle of the intersection. Do you have a stock M/C? I still have stock calipers but even with stainless braided hoses the pedal was soft. I upgraded to a 1-1/8" SVX M/C and it was solid like a rock! However, there wasn't quite enough assist. There wasn't enough room for a 9" RS single stage booster but a Legacy 7"/8" tandem booster fit fine. It feels awesome now, I can lock the brakes up without any problem (once warm ), and the pedal is very solid with a good feel. I'm running a legacy 15/16th MC and braided lines all 'round.. Feels pretty good. I'd love to do the SVX M/C (I thought it was 1 1/16"?) but we never got the svx here in my RHD land..I did get the part no...but I was suprized by how good the 15/16th part performs I expected mush, but it is nice and firm and very progressive..so the first gen tandem booster fits? cool.. BTW In all my insane brake abuse with the stock setup I never warped the OEM rotors.. Maybe 'cuz I was using FHI originals..? Kaz Quote Link to comment Share on other sites More sharing options...
Txakura Posted February 6, 2009 Share Posted February 6, 2009 If someone did spring for the 'show' rotors, it'd be cool if they did poor man's stopping tests before and after. I really like the above technical posts, fantastic research and info. This board amazes me. Group hug? Quote Link to comment Share on other sites More sharing options...
presslab Posted February 6, 2009 Share Posted February 6, 2009 I'm running a legacy 15/16th MC and braided lines all 'round.. Feels pretty good. I'd love to do the SVX M/C (I thought it was 1 1/16"?) but we never got the svx here in my RHD land..I did get the part no...but I was suprized by how good the 15/16th part performs I expected mush, but it is nice and firm and very progressive..so the first gen tandem booster fits? cool.. BTW In all my insane brake abuse with the stock setup I never warped the OEM rotors.. Maybe 'cuz I was using FHI originals..? Kaz Oh yah you're right, 1 1/16". I bought it from 1stsubaruparts and it was about $120 I think. The 1 1/16" is probably a bit overkill. I imagine you'll need to fab some pipes to put a LHD M/C on... Maybe a 1" Legacy M/C would be idea. After the SVX M/C install I needed the tandem booster. It didn't have enough power otherwise to lock em up. Supposedly the 9" single stage is better than the tandem in feel. With the SVX M/C and 8" stock booster it was firm. With the 7"/8" booster & SVX M/C it took a bit less pressure for moderate stopping (still very firm) and it allowed more pedal pressure before running out of assist. It's easy to tell when assist is gone - there is a little bump feeling in the pedal. Quote Link to comment Share on other sites More sharing options...
Numbchux Posted February 6, 2009 Share Posted February 6, 2009 wow, this thread has wondered. in theory, a drum setup SHOULD have as much power as discs. but do the swap, and you'll change your tune. also, a rear disc swap would help prevent the fronts from warping because they're not working as hard, and therefore won't build up as much heat. drilled rotors = cracked rotors slotted doesn't help much with heat...helps clean the pads, give more "bit" etc. only thing that you can do to a rotor to prevent warping is cryo treat it. frozenrotors.com offers cryo'd rotors for an EA82 (only listed for an XT, but they're the same). standard for about $90 each, and slotted for 140. I just ordered a full set of frozen rotors for my wagon. IMHO, these are the best rotors money can buy without changing size or material. Quote Link to comment Share on other sites More sharing options...
jackbombay Posted February 7, 2009 Author Share Posted February 7, 2009 Normally I can't see where an loyale would ever have rotor warping issues, but this pass really is brutal, 3 miles of %10 grade on both sides. I'll start with making sure the rears are working well along with new brembo rotors. New cylinders for the back should be pretty cheap so I'll swap them out while I'm in there along with a full bleed/flush. Quote Link to comment Share on other sites More sharing options...
carfreak85 Posted February 7, 2009 Share Posted February 7, 2009 only thing that you can do to a rotor to prevent warping is cryo treat it. Frozenrotors.com offers cryo'd rotors for an ea82 (only listed for an xt, but they're the same). Standard for about $90 each, and slotted for 140. I just ordered a full set of frozen rotors for my wagon. Imho, these are the best rotors money can buy without changing size or material. +1. Quote Link to comment Share on other sites More sharing options...
presslab Posted February 7, 2009 Share Posted February 7, 2009 only thing that you can do to a rotor to prevent warping is cryo treat it. frozenrotors.com offers cryo'd rotors for an EA82 (only listed for an XT, but they're the same). standard for about $90 each, and slotted for 140. I just ordered a full set of frozen rotors for my wagon. IMHO, these are the best rotors money can buy without changing size or material. After a bit of research it looks like cryo treatment stress relieves the whole rotor. I'm not sure why cold is used instead of heat (perhaps the material) but this is a great idea. Quote Link to comment Share on other sites More sharing options...
Numbchux Posted February 7, 2009 Share Posted February 7, 2009 After a bit of research it looks like cryo treatment stress relieves the whole rotor. I'm not sure why cold is used instead of heat (perhaps the material) but this is a great idea. yea, I don't know the physics behind why it works. but it does. the guys that work at frozen rotors (here in MN....active in the MNSubaru club) go as far as treating they're razor blades, which then last a ridiculously long time. Quote Link to comment Share on other sites More sharing options...
RenaissanceMan Posted February 7, 2009 Share Posted February 7, 2009 yea, I don't know the physics behind why it works. but it does. the guys that work at frozen rotors (here in MN....active in the MNSubaru club) go as far as treating they're razor blades, which then last a ridiculously long time. Ok, I remember learning about this in my metallurgy class, but I referenced back to my notes just to make sure. When iron is heated above a certain temperature (temp depending on the percentage of carbon), the crystal structure changes to "austenite". Upon a slow cooling process, the majority of the structures change to Pearlite & ferrite in low carbon steels, and Pearliite & Cementite in high carbon steels (cast iron falls in that catagory). If the iron is cooled very quickly it forms martensite. Martensite is very very strong but very brittle. Getting the right combination of all these crystaline structures is what gives certain metals their certain properties. For cast iron... in any regular cooling process, slow or fast... not all of the austenite transforms into something else. The problem with having these free-floating austenite crystals is that during normal service and mild temperature changes, they can occasionally alter crystal structure to something else. This happening when none of the other crystals around it are changing, creates stress. *Stress that can lead to warping on our brake rotors, or microfractures that eventually lead to cracking. Interestingly enough, inertia plays a role in the process. When the cooling process is stopped, molecules have a chance to "settle into place" and therefore become resistant to transformation. *With the cryo-treating process, The cooling keeps going. The idea is that continuing the temperature drop in the cooling process down into the negative 200 degree F range, allows more austenite to be transformed into another structure. Even though the metal gets extremely cold, the cooling process hasnt been stopped, transformations are still occuring because things havent "settled". The end result from cryo treating is that there is a minimal amount of austenite after the treatment process, greatly reducing the chance for warping and fracturing during service. (fun fact for the day) -Mike Quote Link to comment Share on other sites More sharing options...
presslab Posted February 7, 2009 Share Posted February 7, 2009 (fun fact for the day) -Mike That's awesome, Mike, thanks!! Quote Link to comment Share on other sites More sharing options...
soopsoop Posted March 16, 2015 Share Posted March 16, 2015 sorry to resurect this old question but my first subaru an 91 legacy fwd the brakes felt solid but didn't stop very good. they were up to the top but would lock up in panic stop which happen a lot in spokane (stupid divers). changed all the brake parts didn't affect it one bit,it was a design flaw from subaru, something about the brake hoses expanding to much pascels law of hydrolics. just my two cents worth. againj sorry about the old thread Quote Link to comment Share on other sites More sharing options...
Loyale 2.7 Turbo Posted March 17, 2015 Share Posted March 17, 2015 ... the brakes felt solid but didn't stop very good. ... That is the usual symptom of a Car whose Master Cylinder has been changed with a Bigger bore one. In example, if your car came from factory with a 15/16" Master Cylinder, and someone swapped it with a 1" Master Cylinder, the Brake pedal will engage Higher, giving such a Solid Rock feeling, but the Clamping Force at the Calipers get Reduced, which is a Risk to your Safety. I Kindly suggest you to search about which Master Cylinder shall have your Front Wheel Drive Legacy, according to the VIN, and compare that with the actual one, let us Know if there is a Difference. Kind Regards. Quote Link to comment Share on other sites More sharing options...
l75eya Posted March 17, 2015 Share Posted March 17, 2015 Excellent article about the absolute b/s that is cross drilled and slotted rotors, and also the "myth" that is warped rotors. Suggested reading: http://oppositelock.jalopnik.com/brake-myths-what-to-expect-when-youre-expecting-to-st-1688020147 2 Quote Link to comment Share on other sites More sharing options...
ferp420 Posted March 18, 2015 Share Posted March 18, 2015 Funny thing i just installed the drilled and sloted rotors with some nice ceramic pads i was in a pinch and was only able to do one side i had to drive about 100mles like that and there was no differance at all if i dident do it my self i wouldent have known the set up was differnt from right to left i expected a little pull but nothing i got the set all 4 wheels the thing is i went to 2 differant auto parts stores and i couldent get close to the price on ebay and i got mine on sale cheap apperently no one wanted drilled and sloted rotors for there loyale so i got them i know from experiance the dilled and sloted rotors ware the pads out alot faster but ive never personaly seen them crack i have seen solid rotors crack on alot of differant cars so i sure it could happen but i dident get them as a upgrade so im not disapointed they where just cheap maybe $20 more than the cheapest set ups i could find so i see it as better than the bottom drawer but not top of the line but still better than the original stock set up that came with the car and hey they look good Quote Link to comment Share on other sites More sharing options...
carfreak85 Posted March 18, 2015 Share Posted March 18, 2015 (edited) sorry to resurect this old question but my first subaru an 91 legacy fwd the brakes felt solid but didn't stop very good. they were up to the top but would lock up in panic stop which happen a lot in spokane (stupid divers). changed all the brake parts didn't affect it one bit,it was a design flaw from subaru, something about the brake hoses expanding to much pascels law of hydrolics. just my two cents worth. againj sorry about the old thread Wait, if the brakes don't stop very good, how can you lock up the tires, or even panic stop? Bleed your brakes. Inspect your calipers for sticking slides or pistons. It is not a design flaw from Subaru, it is you. Funny thing i just installed the drilled and sloted rotors with some nice ceramic pads i was in a pinch and was only able to do one side i had to drive about 100mles like that and there was no differance at all if i dident do it my self i wouldent have known the set up was differnt from right to left i expected a little pull but nothing i got the set all 4 wheels the thing is i went to 2 differant auto parts stores and i couldent get close to the price on ebay and i got mine on sale cheap apperently no one wanted drilled and sloted rotors for there loyale so i got them i know from experiance the dilled and sloted rotors ware the pads out alot faster but ive never personaly seen them crack i have seen solid rotors crack on alot of differant cars so i sure it could happen but i dident get them as a upgrade so im not disapointed they where just cheap maybe $20 more than the cheapest set ups i could find so i see it as better than the bottom drawer but not top of the line but still better than the original stock set up that came with the car and hey they look good Holy run-on sentence Batman! If you "dident get them as a upgrade so im not disapointed they where just cheap maybe $20 more than the cheapest set ups", then why spend the extra $20 at all? Spelling and grammer check. It's a thing. Edited March 18, 2015 by carfreak85 Quote Link to comment Share on other sites More sharing options...
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