stoping distance on "big brake kits"

[Scooter]

do those guys that have fitted R888 tyres and the like, feel the improved braking from having these tyres fitted?

[Sean1933]

do those guys that have fitted R888 tyres and the like, feel the improved braking from having these tyres fitted?

 

I would say without a doubt. Not had them on the supra but a mate had them on an Evo.

[paul mac]

do those guys that have fitted R888 tyres and the like, feel the improved braking from having these tyres fitted?

 

thats a good point mate i am sure some people are unaware that your brakes are only as good as your tyres, i am now in need of new tyres as the front Toyo's are shot i am going to buy the best i can afford and probably spend about £600 + on the full set, after going to all this trouble Ying cheng really isn't an option:D

[SUPRASUZUKI]

That braking force list is pretty much irrelevant though. It doesn't really matter if your brakes manage 1600 "braking horsepower" (whatever that is) or 1 million. If they are strong enough to lock the wheels it makes no difference. What matters is the amount of heat they can dissipate.

 

Also, it doesn't say anything about how the test was done. Plus there's no link to the actual results, it could just be a load of made up numbers in a table for all we know!

 

I've just emailed the author of the article to see if he's got any further info to back the numbers. If I get anything I'll post it up.

[Gazboy]

Fair point Ian and i would have to agree at this time.

 

I am in a lazy mood and cant really be bothere to go on a hunt but does anyone know the stock piston size on the UK specs? One thing i did notice is that the Brembo pistons are considerably larger than those of the j-specs. The calipers are alot lighter than the j-specs too

 

50mm I think.

 

I've got UK's all round with Endless CCX pads if you need the car for your proposed test.

 

It's telling that only now has the 911 carrera managed to match the Supras deceleration distances set in 1993.

[Sean1933]

50mm I think.

 

I've got UK's all round with Endless CCX pads if you need the car for your proposed test.

 

It's telling that only now has the 911 carrera managed to match the Supras deceleration distances set in 1993.

 

Thanks, i will have a look at the Brembo's next time im down the garage.

[Chris Wilson]

from what i have read i would say this is the definative test, we can theorise forever about brake force but its out on the road it matters, i think i may have posted this at the wrong time of year, when its dry and warmer i am going to do some testing and if need be install a bias valve until i get the best stoping distance i can, i found some really good info whilst doing the brakes on my car and one of the most thought provoking was on http://www.stoptech.com/tech_info/tech_white_papers.shtml, as follows ~

 

The most dramatic front-bias impacts are usually brought about by “big brake kits” which are not properly matched to the intended vehicle. Any time that a bigger front rotor is installed, there is a simultaneous need to decrease the effective clamping force of the caliper (installing smaller pistons is the easiest method) to offset the increased torque created by larger rotor effective radius. Unfortunately, too many upgrades do not take this factor into account, and those poor cars end up with both bigger rotors and larger pistons which serve to drastically shift the bias even more forward. While rock-solid stable under braking, stopping distances will go up dramatically.

 

www.apracing.com is also a good site

 

maybe i should have called my liitle treaty on brake upgrades a "White Paper" and given it a bit more class?

 

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.

[SimonB]

I've just emailed the author of the article to see if he's got any further info to back the numbers. If I get anything I'll post it up.

 

That would be interesting. I've seen them posted up a few times, but never where they actually came from in the first place.

[paul mac]

maybe i should have called my liitle treaty on brake upgrades a "White Paper" and given it a bit more class?

.

 

lol you need to hire a marketing consultant Chris, nice write up

[Ian C]

As a slight sidetrack, Chris, I know you've made a brake bias adjuster for the Supra before, but I recall you told me you'd have to junk the ABS system for it to work and then a good while later you said it'd work with ABS. Can you clarify my dodgy memories on such a thing, as I reckon the rears can do more than they currently do...

 

-Ian

[Chris Wilson]

I THINK it could be made to work with the ABS, but I have never really investigated it, and whether it would work with the ABS on both UK and J-Spec cars I have no idea. Depends whether the ABS unit totally divorces front and rear circuits, hydraulically.

[paul mac]

As a slight sidetrack, Chris, I know you've made a brake bias adjuster for the Supra before, but I recall you told me you'd have to junk the ABS system for it to work and then a good while later you said it'd work with ABS. Can you clarify my dodgy memories on such a thing, as I reckon the rears can do more than they currently do...

 

-Ian

 

oh dear thats blown one of my summer projects out of the water, thanks for ruining my summer Ian:D

 

seriously i didn't realise a bias valve will not work with the ABS

[Chris Wilson]

I don't use bias valves, I made a proper dual master cylinder set up, and removed the servo, it was on serious race calipers though, and the pedal effort was a lot higher than stock. I made something similar for my own car, have a look in likely brake folders (bias brakes I thnk) at ftp://ftp.chriswilson.tv/skyline_stuff

[paul mac]

I don't use bias valves, I made a proper dual master cylinder set up, and removed the servo, it was on serious race calipers though, and the pedal effort was a lot higher than stock. I made something similar for my own car, have a look in likely brake folders (bias brakes I thnk) at ftp://ftp.chriswilson.tv/skyline_stuff

 

cheers Chris, as allways you are a font of wisdom:D

[spiderpigcity]

most people miss the point with big brakes. looking at my mates f430 the brakes are tiny. this is because they are light. the car is light, the drive train is light. everything is light. what im trying to say is, you don't need big brakes if your car is light in the right places. most of you will take the piss, but if you look at porsche, ferrari etc they are all the same in terms of size etc. not as big as you would expect. the weight of the wheels and components on the axle are just as important. the right size tyres also play a big part. i could start the discussion about the pounds per square inch pressure on the tarmac from the tyre. wider you go the less you have. but then the more adhesion you have cos there's more rubber. anyway im going off a bit there.

 

loose the weight and forget the outragous 8 pot stuff. if you are concerned about fade then you need to look at the cooling capabilities of the design in the wheels (weight of the wheel) etc. if you are really concerned about fade then you should be running carbon discs, they are lighter and will hardly fade at all. cost is the problem with carbon as you all know.

 

personally i would look at other ways of making my car stop quicker rather than buying expensive large 8 pot stuff.

 

Give me 3 grand and i will come and make your car stop quicker and accelerate faster than the guy who buys the flash brembos.

 

put 2 gallons in your tank, take your back seats out, take carpets out, empty washer bottle, take big spoilers off, replace glass with plastic, i could keep going you get my drift.

 

bottom line do you want bling or performance.

 

 

:p

[colsoop]

 

bottom line do you want bling or performance.

 

 

:p

 

The problem is people want both

[garethr]

That braking force list is pretty much irrelevant though. It doesn't really matter if your brakes manage 1600 "braking horsepower" (whatever that is) or 1 million. If they are strong enough to lock the wheels it makes no difference. What matters is the amount of heat they can dissipate.

Also, it doesn't say anything about how the test was done. Plus there's no link to the actual results, it could just be a load of made up numbers in a table for all we know!

I did some Googling when I first saw the Planet Soarer list a few years ago, and IIRC the "braking horsepower" is the result of a calculation involving things like master/slave cylinder area, disc diameter, etc.

 

EDIT:

Most of the references I found (other than those which used braking horsepower for "Brake Horse Power") were in the context of railway locomotives or heavy goods vehicles.

[paul mac]

Give me 3 grand and i will come and make your car stop quicker and accelerate faster than the guy who buys the flash brembos.

 

put 2 gallons in your tank, take your back seats out, take carpets out, empty washer bottle, take big spoilers off, replace glass with plastic, i could keep going you get my drift.

 

bottom line do you want bling or performance.

 

 

 

Matt you make some very good points weight being one of them, as for bling versus performance yes i am sure there are people out there who fit big brake kits purely for the aesthetics and couldn't give a jot about braking performance but that is no reason to critisise as its each to their own, personally i will admit i want bling and performance, as for "outragous 8 pot stuff" my set up comes from a stock Mercedes production car and is basically the same caliper Porsche and Audi use, if these manufacturers see fit to put this type of brake on a road car that produces less power than mine am i necesarily being "outragous" fitting it to mine, with regard to the weight issue please see the attached pic as i have done a lot of work in this area and basically if any item is not needed its off the car (that includes ICE and all sound insulation), seats, wheels, titanium rear brace/harness bar, weight distribution (washer bottle and battery in the boot) please feel free to look round my "garage" and advise where you could spend my £3000

[spiderpigcity]

i tell you what i will give the number of the guy who manages our racing team in the british touring car championships. he has the experience and the knowledge to make your car light.

[spiderpigcity]

another example. we run a clio club sport from the clio williams series, 6 spd sequential and all that. but more to the point we tried every kind of brake disc and pad available and came to the conclusion that the 60 quid renault spec discs and pads where better than all of them for fade, braking and what not.

just an example of how much people "can" waste their money and get carried away with aftermarket "performance parts" when really they are worse than the oem stuff.

 

i'm not trying to wind you guys up i'm just trying to help. like my mate says, if its simple engineering and nothing is moving then only pay fior what it is. if its a moving part with precision engineering involved then pay the money.

[spiderpigcity]

Matt you make some very good points weight being one of them, as for bling versus performance yes i am sure there are people out there who fit big brake kits purely for the aesthetics and couldn't give a jot about braking performance but that is no reason to critisise as its each to their own, personally i will admit i want bling and performance, as for "outragous 8 pot stuff" my set up comes from a stock Mercedes production car and is basically the same caliper Porsche and Audi use, if these manufacturers see fit to put this type of brake on a road car that produces less power than mine am i necesarily being "outragous" fitting it to mine, with regard to the weight issue please see the attached pic as i have done a lot of work in this area and basically if any item is not needed its off the car (that includes ICE and all sound insulation), seats, wheels, titanium rear brace/harness bar, weight distribution (washer bottle and battery in the boot) please feel free to look round my "garage" and advise where you could spend my £3000

 

 

looks like you have done a bit of stripping there. have you drilled any holes anywhere yet to save weight? obviously not just anywhere. plastic windows? replacement cast or steel parts with aluminium anywhere?

[Nic]

advise where you could spend my £3000

 

Paul I'll happy spend some of it on some Top Secret light weight Acrylic (driver and passenger) windows, GT carbon fibre mirrors and 4.7kg GReddy Ti-R exhaust

 

ps. I'll keep thinking, I'm sure I can find more things to sell you ( this in tech scratch that idea!)

[Thorin]

we tried every kind of brake disc and pad available and came to the conclusion that the 60 quid renault spec discs and pads where better than all of them for fade, braking and what not.

 

So you're trying to tell us that standard OEM discs and pads are better than any proper race stuff?

[Nic]

So you're trying to tell us that standard OEM discs and pads are better than any proper race stuff?

 

OEM brakes are actually very heavy, but they perform well and are relatively cheap.

 

If I was speccing a lightweight setup for the road/track, I would go with one of these, all of which are similar size to the OEM brakes, but are considerably lighter, more rigid and should perform better.

 

TRD 4 Pot Monoblock Front Brake Kit

 

 

Project Mu Forged 4 Pot Monoblock Front Brake Kit

 

http://img46.imageshack.us/img46/8540/picture1jz1.png

 

TOMS 6 Pot Front Brake Kit

 

http://img69.imageshack.us/img69/2637/43051tgs80lb8.jpg

 

TOMS 4 Pot Rear Brake Kit

 

http://img408.imageshack.us/img408/7592/43052tgs80sr9.jpg

[spiderpigcity]

So you're trying to tell us that standard OEM discs and pads are better than any proper race stuff?

 

if you read the post carefully i said in that scenario yes they where. i am not suggesting that every car is the same. but in general i am amazed at how many people buy aftermarket stuff which have all these "big claims". it's a bit like the supplement market with tablets and weight loss etc. a lot of marketing and no substantial proof. but also notice that this is a track renault from the factory not a renault cup 182/192 etc that you buy from the showroom.

 

i am not aiming this at the traders on the site, as a lot of the stuff clearly is for a purpose eg, injectors, bigger turbos, adjustable shocks etc, and does what it should.

 

the best thing you can do is go down to a touring car meet or the 911 gt cup and see if they will let you in the garage at the side of the pits, so you can stand and look at what these guys use. it will astonish you when you see 200-350k cars held togther with duck tape and stuff generally all over the place. its hard to explain until you sit in one and have been on the track in one.

 

i think the argument here is understand the difference between a show car that is very fast on the road eg. your supra, and a track car that will wipe the floor with anything you don't spend less than 200k on. that's the reality. i think fast and the furious is to blame although its a top film.

 

anyway of the thread a bit here but you get my drift.

 

 

:p