captainmorgan Posted March 15, 2006 Share Posted March 15, 2006 eh, I was going to post a small rant here instead of in the circus ring of the other thread, but now I just don't care. Link to comment Share on other sites More sharing options...
05Limited Posted March 15, 2006 Share Posted March 15, 2006 ^???? Link to comment Share on other sites More sharing options...
jsalicru Posted March 15, 2006 Share Posted March 15, 2006 ANSWERS... ROTORA: Front 330mm 1-piece kit # of Pistons = 4 Type of Caliper = radial mount Piston Size = 38.18/42.85mm Rotor Diameter = 330 mm Rear 2-piston 1-piece # of Pistons = 2 Type of Caliper = radial mount Piston Size = 40.45/40.45mm Rotor Diameter = 290mm 2 Piece Kit Front 2-piece kit # of Pistons = 4 Type of Caliper = radial mount Piston Size = 38.18/42.85 Rotor Diameter = 330 mm Rear 4-piston 2-piece # of Pistons = 4 Type of Caliper = radial mount Piston Size = 30.23/30.23mm Rotor Diameter = 330mm Looks like the 2-piece rear is most likely designed to work with the 6-piston front kit. So I just replied to him and asked for THOSE specs.. "some say, his arms are made of coiled adamantium fibers. And that he tops his cereal with nuts and bolts. All we know is, he's called the Jose." Link to comment Share on other sites More sharing options...
jsalicru Posted March 15, 2006 Share Posted March 15, 2006 ROTORA Front 2-piece 6-piston kit # of Pistons = 6 Type of Caliper = radial mount Piston Size = 30.23/34.93/40.45mm Rotor Diameter = 355mm "some say, his arms are made of coiled adamantium fibers. And that he tops his cereal with nuts and bolts. All we know is, he's called the Jose." Link to comment Share on other sites More sharing options...
captainmorgan Posted March 15, 2006 Share Posted March 15, 2006 I just ran those numbers through the spread sheet and sort of made an educated guess at the effective diameter (not really sure how its calculated but based it on the change in the other diameters), and came up with a bias shift of 4% for an LGT and 10% for an OBXT to the rear for a Rotora kit with the same style pads as stock. Link to comment Share on other sites More sharing options...
praedet Posted March 16, 2006 Author Share Posted March 16, 2006 Updated the top w/ Rotora stuff... Rotora 4-piston Fronts w/ Stock rear or 2-piston rear looks pretty good Rotora 6-piston 330 mm rotor Fronts w/ 2-piston rear is biased like stock, but would be pretty sensitive Rotora 6-piston 355 mm rotor Fronts w/ 4-piston rear is pretty good bias, but would be ULTRA-sensitive... And just to add to this, if you run a moderate street pad (mu = 0.5) with the Rotora 4-piston fronts, w/ no upgrade to the rear, you are looking at an 80.5%/19/5% bias... Ted Link to comment Share on other sites More sharing options...
TSiWRX Posted March 16, 2006 Share Posted March 16, 2006 Thanks, Ted, for the figures. I "approximated" things a bit last night - and made the decision to go with the Rotora 4-pots already. I'll likely go for the rear retro some time in the future, but will wait to see how things go with the changed fronts before making that decision. Thanks again! -A <-- 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...
LittleBlueGT Posted March 16, 2006 Share Posted March 16, 2006 Good info. Finally someone can post something educational about brakes! 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...
sandwood Posted March 16, 2006 Share Posted March 16, 2006 so forgive me if this is a dumb question, but are you saying that the racingbrake kit is too rear biased, and would definitely benefit from using grippier pads in the front compared to the rear? getting out of the legacy game Link to comment Share on other sites More sharing options...
PGT Posted March 16, 2006 Share Posted March 16, 2006 looking at the brake torque spec, it appears as if the RB 4pots have less ability than stock. Link to comment Share on other sites More sharing options...
sandwood Posted March 16, 2006 Share Posted March 16, 2006 I'll email them. that's fvcked if true, and they simply took the wrx upgrade kit - which might have the appropriate, upgraded balance for that car, and applied it over to the lgt. getting out of the legacy game Link to comment Share on other sites More sharing options...
LittleBlueGT Posted March 16, 2006 Share Posted March 16, 2006 looking at the brake torque spec, it appears as if the RB 4pots have less ability than stock. The stock brakes have more then enough ability as far as clamping force. I don't think it is a problem, as long as it dissipates heat better, distorts less, and has better feel then stock calipers. 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 March 16, 2006 Author Share Posted March 16, 2006 Some things to remember. The amount of torque generated only matters when comparing front to rear, or when you start to get past stock torque numbers. Remember that moving to a mild street mu, 0.4, increases torque by 1/3 on the stock system. The greater the instantaneous torque, the more sensitive the brakes are. Going to the extreme, the 6-piston 355 mm Rotora front w/ 4-piston 330 mm rear with Bobcat/Ferrodo 2500 mu (0.5) is going to hava 110% greater torque for the same amount of pressure. Personally, that would be WAY to sensitive for me. Truly on/off... A good front BBK, if meant to be used with stock rears, should actually reduce the torque in the front to try for 70/30. So the RB kit just overshoots this. When you take the iON kit w/ stock rears and add pads to all 4 w/ a mu = 0.5, you get 55% more torque, w/ almost perfect 70/30 bias. That is ideal. To get the RB kit perfect, I would run a stickier pad (.5) up front and a moderate street pad in the back (.45) That makes it virtually 70/30 w/ a 42% increase over stock torque. Focus on the bias, and if there is a lot MORE torque than stock (bad because it becomes on/off.) The STi Brembo front only, with mu of 0.5 and bone stock rear is 82/18 and 53% more torque. Equivalent pads and it goes 73/27 and 72% more torque. Add the rear brembos and you get 74/26 and 70% more torque. None of those are what I personally would want to run on this car... Ted Link to comment Share on other sites More sharing options...
PGT Posted March 16, 2006 Share Posted March 16, 2006 where does the ideal 70/30 figure come from? The full Brembo kit is not that and SOA could have spec'ed whatever they wanted. There's obviously a reason for the choices they made. Link to comment Share on other sites More sharing options...
ilh Posted March 16, 2006 Share Posted March 16, 2006 Some things to remember. The amount of torque generated only matters when comparing front to rear, or when you start to get past stock torque numbers. Remember that moving to a mild street mu, 0.4, increases torque by 1/3 on the stock system. The greater the instantaneous torque, the more sensitive the brakes are. Going to the extreme, the 6-piston 355 mm Rotora front w/ 4-piston 330 mm rear with Bobcat/Ferrodo 2500 mu (0.5) is going to hava 110% greater torque for the same amount of pressure. Personally, that would be WAY to sensitive for me. Truly on/off... Is the ratio of total caliper piston area to master cylinder area getting factored in here anywhere? If you increase caliper piston area (e.g., more pistons) and keep the master cylinder the same, won't you be decreasing sensitivity? That is, you need more pedal movement to produce the same caliper movement. It seems a lot of folks who are after less pedal movement (i.e., more sensitivity) might be shooting themselves in the foot with some of these BBK setups, no? Link to comment Share on other sites More sharing options...
PGT Posted March 16, 2006 Share Posted March 16, 2006 Not sure about that, but my Brembo/Hawk HPS front upgrade makes my pedal much firmer and 'bites' sooner....my goals for the swap. Link to comment Share on other sites More sharing options...
praedet Posted March 16, 2006 Author Share Posted March 16, 2006 Dan, Here is one of the articles that talks about brake biasing. I will look for more. In it, they tested an Audi S4. (twin-turbo) A ratio of 2.5, or 71.5%/28.5% was ideal for that car. While the LGT is different, it is close enough to the same, that the numbers from the S4 should be close. Factor in that we have a better F/R weight distribution, and the lower center of gravity due to the boxer, and that is why 70/30 (2.3333 using their convention) is likely ideal for our car. All manufacturers design in front bias so the tail doesn’t get happy during braking. Shifting closer to a 4 wheel lock-up equates to shorter stopping distances. The STi Brembo front w/ stock rear and stock pads is a 4.56 using their convention. Take a look where that puts you on the chart… Make sense? Ted Link to comment Share on other sites More sharing options...
praedet Posted March 16, 2006 Author Share Posted March 16, 2006 Is the ratio of total caliper piston area to master cylinder area getting factored in here anywhere? If you increase caliper piston area (e.g., more pistons) and keep the master cylinder the same, won't you be decreasing sensitivity? That is, you need more pedal movement to produce the same caliper movement.Good question! No. For these calculations I was mainly trying to show what you would do to your bias. I am working on building in the MC/piston size problems... Link to comment Share on other sites More sharing options...
PGT Posted March 16, 2006 Share Posted March 16, 2006 where would a stock STi be? Link to comment Share on other sites More sharing options...
praedet Posted March 16, 2006 Author Share Posted March 16, 2006 What is the weight distribution of a stock STi? Link to comment Share on other sites More sharing options...
PGT Posted March 16, 2006 Share Posted March 16, 2006 3,351 lbs F 58.2/41.8 R Link to comment Share on other sites More sharing options...
praedet Posted March 16, 2006 Author Share Posted March 16, 2006 Interesting. That makes me think the proportioning valve on the STi is set-up quite different. Subaru also might take into account the EBD on the Legacy and tune closer to the edge of a perfect bias since if the rears do lock the LGT will send more to the front and less to the rear... Ted Link to comment Share on other sites More sharing options...
PGT Posted March 16, 2006 Share Posted March 16, 2006 that being said about EBD, why is this even an issue to discuss?? If we have a dynamic system, why are the calculations based on static data? Link to comment Share on other sites More sharing options...
jsalicru Posted March 16, 2006 Share Posted March 16, 2006 that being said about EBD, why is this even an issue to discuss?? If we have a dynamic system, why are the calculations based on static data? Most likely because the dynamic aspect doesn't come into play until its ABS time. Its better if the EBD has to play less or barely any at all. The effects of an improper setup can be felt before the ABS hits. "some say, his arms are made of coiled adamantium fibers. And that he tops his cereal with nuts and bolts. All we know is, he's called the Jose." Link to comment Share on other sites More sharing options...
praedet Posted March 16, 2006 Author Share Posted March 16, 2006 He typed faster than me Great question too! Because EBD functions only when the tires lock... If you have it set up perfect, you can go further before they lock and EBD starts to send the biasing around. I wish it was a truly intelligent system, but it is not. But, this is truly a dynamic problem, that is why we don't have a 55/45 bias to match the car's weight bias. This also doesn't take into account the large flex of a sliding caliper, or the almost zero flex of an AP racing caliper vs. a Brembo caliper. Those are variables that come into play, but do not affect things so much that it changes the end result. Does that help? Ted Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now