AJI Posted June 30, 2009 Share Posted June 30, 2009 Doesn't the 'power' applied to the brake calliper pistons come from the servo and master cylinder setup? So no matter if you have a 1-pot or a million-pot you will still have the same force being applied through the pad to the brake disc. I've always had the line of thought that if you are able to lock your wheels when braking (or can easily engage the ABS system) at speed then you have enough braking power. Changing the pads and fluid to higher grade materials will increase the effectiveness and performance of the brakes better than increasing the number of pots in the callipers. Quote Link to comment Share on other sites More sharing options...
dr_jekyll Posted June 30, 2009 Share Posted June 30, 2009 well im currently fitting uk spec lexus ls400 4 pots with 315mm discs on my j spec na-t , as i think the 2 pot j-specs are insuffcient for the 1.4 tonne car , my 2.5 tonne 1997bmw 728 can outbrake my supe from 70 to a stop by a good 30 yards , Quote Link to comment Share on other sites More sharing options...
Scott Posted June 30, 2009 Share Posted June 30, 2009 Doesn't the 'power' applied to the brake calliper pistons come from the servo and master cylinder setup? So no matter if you have a 1-pot or a million-pot you will still have the same force being applied through the pad to the brake disc. I've always had the line of thought that if you are able to lock your wheels when braking (or can easily engage the ABS system) at speed then you have enough braking power. Changing the pads and fluid to higher grade materials will increase the effectiveness and performance of the brakes better than increasing the number of pots in the callipers. Partially correct. The problem is heat, or more accurately the dispersment of it. The larger the discs & pads the more the heat is spread meaning that the brakes don't get "cooked". With 2pot fronts and 1 pot rears stopping from 180mph will be extremely hairy as the discs and pads will heat up very quickly. You are right though, the same braking force is applied to the pad. The friction of the pad then determins the biting/stopping force. Quote Link to comment Share on other sites More sharing options...
L33 Posted June 30, 2009 Share Posted June 30, 2009 Some very good points here. I think some people have the wrong idea about me. Im not one of these who go for power with out upgrading brakes. I havent had my car back since the conversion started so i havent driven it yet since it was a tt so im looking to upgrade the brakes at the same time. Now is the time every thing else is bought and built for me to find brakes. The big ones do look good but i want good stopping power. Im not one to toe it every where but its just knowing i have great stopping power. Like the single conversion, i dont need 600bhp but its nice to know its there Quote Link to comment Share on other sites More sharing options...
AJI Posted June 30, 2009 Share Posted June 30, 2009 partially correct? Yes, agreed the pad efficiency may be affected when doing multiple stops or doing 180mph stops and will cause a LOT of heat to be dissipated, but if the heat can be 'managed' then no real need to upgrade to huge number of pots (in principal that is). Quote Link to comment Share on other sites More sharing options...
Guigsy Posted June 30, 2009 Share Posted June 30, 2009 ill let steveL comment on the braking and corners thing. but if your in a longer corner and thinking "hum im going a bit fast" and put the brakes on if your not carefull you will be going backwars rather quickly. By braking in the corner you unsettle the car and shift weight to the front which gets the rear end loose and due to the g-forces and the direction your traveling and the direction the rear end w ant to go end up being different. Most of the time you will run wide or swap ends. I knew this before the llandow trackday and on the long fast last corner i always took it easy. however one time i did dab the brakes and even slightly you could feel the rear end wanting to come arround. Quote Link to comment Share on other sites More sharing options...
Scott Posted June 30, 2009 Share Posted June 30, 2009 it can't be managed without cooling or larger surface area though, hence the larger pots. Lee, you only need uk's. If you want the bigger brakes for the looks then fair enough. If you didn't cook your current brakes then they should be ok as your driving style will only have a blip due to your new toy. I wouldn't have anything less than uk's and i don't need anything more at the moment. If you start cooking pads or warping discs then its time for an upgrade. Quote Link to comment Share on other sites More sharing options...
jamesmark Posted June 30, 2009 Share Posted June 30, 2009 I am guilty of braking through corners but only when I drive an auto, not that I drive like I am on 2 wheels (I hate corners). Quote Link to comment Share on other sites More sharing options...
SteveL Posted June 30, 2009 Share Posted June 30, 2009 ill let steveL comment on the braking and corners thing. but if your in a longer corner and thinking "hum im going a bit fast" and put the brakes on if your not carefull you will be going backwars rather quickly. By braking in the corner you unsettle the car and shift weight to the front which gets the rear end loose and due to the g-forces and the direction your traveling and the direction the rear end w ant to go end up being different. Most of the time you will run wide or swap ends. I knew this before the llandow trackday and on the long fast last corner i always took it easy. however one time i did dab the brakes and even slightly you could feel the rear end wanting to come arround. ... no need to mate, thats pretty much it! Without getting too techy, and in a track environment, the only time you are on the brakes and steering is 'trail braking' but thats a whole different technique. On the road you can and most people do brake in corners when under normal conditions - you can because the dynamics of the car are no where near the limits (generally speakining). Lee, you only need uk's. If you want the bigger brakes for the looks then fair enough. If you didn't cook your current brakes then they should be ok as your driving style will only have a blip due to your new toy. .... exactamundo. You could try the UK's first - if you don't like them you can sell them on and try an upgrade. At least you'll know where you started from. Quote Link to comment Share on other sites More sharing options...
L33 Posted June 30, 2009 Share Posted June 30, 2009 Thanks for Some good advice even tho i hi jacked this thread. I will go uk rear for def then if i have enough money depending how much the labour bill is so far for the conversion i will either get uk front or go for the looks but even if i get uks i wil get some good disks and pads to help more Quote Link to comment Share on other sites More sharing options...
MarkR Posted June 30, 2009 Share Posted June 30, 2009 I had J-specs on a standard Supra - no mods at all. Even then the brakes were bad. Then I went BPU and they were very bad. Then I upgrade to Brembo fronts and J-spec rear, not too bad. Then I went from Auto/Tiptronic to Manual, and now they feel inferior as the amount of reaction time has changed as the gears are shorter. If you had a BPU and had the gas flat on the floor, you'd be accelerating at a certain speed. If you were in a single, you'd be accelerating maybe twice as fast (or at least feel like it), and by the time you realise you need to brake, and have started pressing on the brake pedal, you'd have covered twice the distance as in BPU, so therefore would need better brakes. If you were both going steadily at 50, then the turbo obviously makes no difference, but you have to take into account the potential requirements for braking, and the bigger singles will be doing from 50 - 80 faster than you can imagine, and suddenly going from accelerating to braking at that sort of load needs better brakes. Quote Link to comment Share on other sites More sharing options...
Guigsy Posted June 30, 2009 Share Posted June 30, 2009 But in reality not many people go from hard (or even steady) acceleration to foot to the floor braking. The only people i see doing that are in saxo's... if you see what im saying people accelerate... go along at the speed limit (or just above) and then need to brake for whatever reason. Quote Link to comment Share on other sites More sharing options...
Scott Posted June 30, 2009 Share Posted June 30, 2009 I had J-specs on a standard Supra - no mods at all. Even then the brakes were bad. Then I went BPU and they were very bad. Then I upgrade to Brembo fronts and J-spec rear, not too bad. Then I went from Auto/Tiptronic to Manual, and now they feel inferior as the amount of reaction time has changed as the gears are shorter. If you had a BPU and had the gas flat on the floor, you'd be accelerating at a certain speed. If you were in a single, you'd be accelerating maybe twice as fast (or at least feel like it), and by the time you realise you need to brake, and have started pressing on the brake pedal, you'd have covered twice the distance as in BPU, so therefore would need better brakes. If you were both going steadily at 50, then the turbo obviously makes no difference, but you have to take into account the potential requirements for braking, and the bigger singles will be doing from 50 - 80 faster than you can imagine, and suddenly going from accelerating to braking at that sort of load needs better brakes. Agreed but i can't see anyone driving that way on the roads and needing anything more than UK spec. As has already been covered in this thread J-Specs will put out just as much stopping power as brembo's. The stopping power is in the tyres, it doesn't matter what brakes you have as long as you can lock them up they are good enough. The difference is how often, how long and from what speed you brake. UK's with good discs and pads should handle anything we can throw at them. If you are on a track you will be using track pads, i reckon UK's would hold their own until getting really really competetive and pushing the limits. Its all about heat Quote Link to comment Share on other sites More sharing options...
Scott Posted June 30, 2009 Share Posted June 30, 2009 But in reality not many people go from hard (or even steady) acceleration to foot to the floor braking. The only people i see doing that are in saxo's... if you see what im saying people accelerate... go along at the speed limit (or just above) and then need to brake for whatever reason. Agreed i just didn't want to say it Hard on the accelerator till your up someones arse and you need to hit the brakes hard is not the way to be driving IMO. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted June 30, 2009 Share Posted June 30, 2009 Brake upgrades can set out to try to achieve several objectives. The commonest are to increase resistance to fade and or increase braking effort for a given pedal effort. IE, the pads are pushed against the discs harder for a given pedal effort than before the upgrade, or the brakes will stop the car from 100 MPH, hard, for more times before fade sets in, than previously. The feel from the pedal, that almost intangible quality, can also be addressed and sometimes improved upon by brake size, or pad material changes, or brake flexi hose upgrades to something less squashy than rubber. It's easy to get carried away by the thought of brake upgrades. The limitation in most cars as to how short a distance they can stop in is tyre friction. Leaving aside pedal feedback, and fade, it is almost certain that a Supra on stock Jap spec brakes will stop in just as short a distance as one with an AP six pot kit on it, a Brembo kit, Pauls KAD kit, or whatever. It may not feel to the driver that it does, but usually such is the case if you just nail the pedal as hard as you can. The fancy kits may *FEEL* to stop the car faster, due to less pedal effort, and a better bite, but in reality, if you hit the pedal as hard as you can with stock Jap spec brakes, UK spec brakes, AP kit, KAD, whatever, the car will stop in the same distance. Repeat this test 10 times and stock Jap brakes may be on fire and long since faded, or the fluid boiled, UK ones may be very hot and bothered, but the upgraded ones will probably still be working within pad, disc and brake fluid temp limits. Add in the intangible "feel" factor, and a desire to brake as hard as possible, using as little skill as possible, but WITHOUT relying on the ABS to take over, and for sure a well set up brake upgrade may well allow more finesse. Herein though lies the rub. Upgrade only the fronts and the brake balance of the stock car may well be compromised. Let's take stock brakes. You press smoothly on the brake pedal with (say) 50 pounds force. The car stops fine. 70 pounds, the fronts are just beginning to lock (car makers ALWAYS aim for the fronts to lock first, as rear wheel lock makes the car very unstable and liable to swap ends). The rears are doing as much work as the brake engineers deemed safe to prevent premature rear lock up. The ABS cuts in, and maximum retardation has been reached. Now, take a car with big front discs and calipers. Only 40 pounds pressure now gives a smooth, lock free and powerful retardation. 50 pounds and the new, more powerful, (for the same pedal pressure), fronts are locking. The ABS cuts in. BUT, and this is the crux, those original rear calipers and discs are still well below the caliper pressure where they are able to achieve maximum retardation without fear of the rears locking. In other words the FRONT brakes are doing TOO MUCH work, albeit without breaking into a sweat, and the rears are, to exaggerate a bit, just along for the ride. The BEST scenario is to upgrade front AND rear brakes, carefully ensuring the original balance of effort at any given brake pedal pressure remains as designed, but that the more efficient front AND rear brakes stay cooler for more hard stops, and that old intangible "feel" from the brake pedal is improved, at lower rates of driver effort on the pedal. The latter may or may not be good or desirable, and can be engineered out by changing BOTH front and rear caliper piston sizes, or pad areas. In a race car the balance would be adjustable via 2 brake master cylinders, with a driver selectable change in mechanical leverage effort between front and rear brake circuits, one cylinder operating the front brake calipers, the other the rear. This can also be achieved on road cars, but to do so is usually complex and expensive, especially if ABS and brake circuit failure safeguards are to be maintained. It is far easier to calculate the caliper and disc sizes, along with pad area and compound to achieve this, as near as available off the shelf equipment will allow. Caveat. I said before makers engineer more effort on the front brakes to encourage straight line stopping if the tyres are locked up . They err on the excessive side, as, in the wet, the rear tyres can take a lot more braking effort than in the dry, due to less weight transfer onto the front tyres, as they will lock before as much weight is transferred when the grip of the road surface is reduced. So adding yet more front brake effort worsens this existing imbalance, especially in the wet. If it were not for the ABS the front wheels would be locking up very early. On the Supra a relatively sophisticated ABS allows some effort to be taken off JUST the fronts, and an artificial and very inefficient balance is returned. On cars with lesser (1 or 2 channel) ABS, or no ABS at all, a brake upgrade on just one end of the car can be lethal. Written hurriedly, and briefly, as my typing speed is terrible, but hope it helps explain the gist of the potential problems. Quote Link to comment Share on other sites More sharing options...
Scott Posted June 30, 2009 Share Posted June 30, 2009 Pfft i just said that Quote Link to comment Share on other sites More sharing options...
Guigsy Posted June 30, 2009 Share Posted June 30, 2009 The almight chris wilson *heavenly sounds from above, angels going "ahhhhhh" etc* has copy pasted from his encyclopedia of "my brain" close thread p.s when you gonna publish that book chris Quote Link to comment Share on other sites More sharing options...
cooin Posted June 30, 2009 Share Posted June 30, 2009 Been to GBH, they suggest me use the Ksports, actually, i was think about the AP Racing one........ Quote Link to comment Share on other sites More sharing options...
Scott Posted June 30, 2009 Share Posted June 30, 2009 Been to GBH, they suggest me use the Ksports, actually, i was think about the AP Racing one........ Good stuff, my mate got done for GBH. Its not fun Quote Link to comment Share on other sites More sharing options...
cooin Posted June 30, 2009 Share Posted June 30, 2009 Good stuff, my mate got done for GBH. Its not fun told price for Ksports will be 1500gbp include the fit, the AP one will be 2300........ Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted July 1, 2009 Share Posted July 1, 2009 Pay the extra, chalk and cheese. Don't be obsessed about six pot calipers on the front either. For the sort of purposes everyone I know of on here uses their cars, 4 pot calipers would be just fine. 6 pots were introduced mainly to reduce taper wear of the pads, in endurance racing, and as many "racey" things do, became fashionable, and then de rigeur, for the road. I had 6 pots and 4 pots to hand, on my garage shelf, when I built my Skyline track brake package, and I chose the 4 pots, for cheaper pads, and better packaging. I actually achieved a bigger swept pad area with the 4 pots than I could have done with the six pots, as well. Quote Link to comment Share on other sites More sharing options...
jamesmark Posted July 1, 2009 Share Posted July 1, 2009 Dave222 looked into K Sport for his BPU car and Single and he did not go for them after he found out more about them. Something to do with it not having some sort of seal so if they are rarely used they may cease, they are all alloy as well. Drop him a PM he will be able to tell you exactly why he never went for them, knowledgable guy too. Quote Link to comment Share on other sites More sharing options...
SteveL Posted July 1, 2009 Share Posted July 1, 2009 (edited) Is it me or is no one reading this thread...! Surely spending £1500 on a front brake upgrade and leaving the rears stock is a waste of effort/money and everyone's time on this thread who's trying to help?! - and dangerous in the wet !!! As Chris and at least 3 others have pointed out, the UK stock system is perfectly adequate for road/track day use with the right pads/discs. I don't say much often, but I've experienced some decent and crap brake setups on Supes on track... but it's your money. Get down to the basic question... do you want the car to work properly or just look good??? Basically were back to the questions earlier in the thread.... Edited July 1, 2009 by SteveL (see edit history) Quote Link to comment Share on other sites More sharing options...
Scott Posted July 1, 2009 Share Posted July 1, 2009 Is it me or is no one reading this thread...! Surely spending £1500 on a front brake upgrade and leaving the rears stock is a waste of effort/money and everyone's time on this thread who's trying to help?! - and dangerous in the wet !!! As Chris and at least 3 others have pointed out, the UK stock system is perfectly adequate for road/track day use with the right pads/discs. ??? Nope its not just you, did you see my reply Quote Link to comment Share on other sites More sharing options...
SteveL Posted July 1, 2009 Share Posted July 1, 2009 Nope its not just you, did you see my reply ... at least its not personal then OK heres some advise.... Buy the biggest full set of 12 pots you can find in dayglow orange and wack those on, don't upgrade the fluid and have fun Quote Link to comment Share on other sites More sharing options...
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