Understanding big non OE brakes

[rider]

Everyone knows big brakes are better than small brakes. The bigger the better (especially when painted) then allied to more pots the better and the bigger the material compressed on disc the better. Except there are plenty of myth buster sites that say you need to be very specific about bigger as its not always better as bigger has no respect for how the car is set up and managed by the automated ABS and traction control systems.

 

I have a jspec on its small discs low number of pots braking and that gets up to near 160mph before the limiter cuts in and it slows down from 160mph without any real drama whenever I've done that and I've done it a lot. So tiny brakes with limited pots do work in real life, real road conditions. It seems bigger brakes come into their own predominantly to dissipate heat fade relative to smaller brakes. Stopping distance is impacted to a large extent by the area of tyre in road contact. So, reading a few sites it appears big brakes may well only be any use if you have lots of corners and chicanes to negotiate while driving as fast as you dare to around a track.

 

There are even sites that mention big brakes can have safety concerns as they draw a lot more hydraulic fluid and DIY fitters may not have factored this into a larger reservoir. Also they can fool the ABS management into thinking things are in a different state of brake panic to where they really are, making braking assistance less effective in panic situations.

 

So, reading between the lines non OE big brakes may well be pointless unless ragging around a track regularly and possibly a retrograde step unless allied to reprogramming or isolating the electronic braking aids. Its an interesting topic and a bit of a black arts area from the limited reading I've done into the subject area. Seems to be a few things that need to consider before just slapping big disc 6 potter on because they look good, all that looks good may not be as good as they look. Pretty key in things a critical as vehicle braking. its a fascinating area where unforeseen side effects can mitigate the perceived advantage.

 

Think I'll do some more reading.

[David P]

If you're happy with your brakes other than how you want them to look, maybe these are for you?

 

http://www.ebay.co.uk/itm/Universal-4pcs-3D-Brembo-Style-Car-Disc-Brake-Caliper-Covers-Front-Rear-Kit-Gold-/311672739476?hash=item4891249694:g:3uQAAOSwU-pXqcms

[Mike2JZ]

Cool story.

 

ABS systems are the same across NA/TT's, so upgrading from oem 2/1pot brakes to the 4/2pot oem brakes won't cause any ill effects.

 

Most people buying big brake kits for the street do it for the bling, or with the aim to stop brake fade.

[j_jza80]

J spec 2/1 pot brakes are okay, nothing more. The 4/2 pot factory brakes were probably the best production car brake setup there was when the Supra was launched, and held a stopping distance record which was only broken some years later by a Porsche Carrera GT.

 

It's the way the larger brakes resist fade which is most obvious. A spirited drive on a twisty road can have the smaller j specs struggling.

[Scooter]

J specs suffer from seized sliders and Pistons (uk's can too) but work well in my experience if in good condition. Expensive pads can mitigate against initial fade and for extended track work upgrading the fluid will stop this boiling and getting fade that way.

 

Most people upgrade when the j specs are performing poorly or are on stock everything and it'll take hundreds to just upgrade them so will go the whole hog to uk's or beyond.

 

My old jspec with CW race pads (over £300 a set) were better than a uk setup with stock pads, but same pads, fluid etc the uk's will be better, as will most aftermarket big kits.

[Dnk]

I don't get the point about the master cylinder, once the calipers are bled the fluid drop in the master cylinder

when you press the brake pedal wont be noticeable, it will only drop a noticeable amount when the pads wear down.

 

I'd rather have opposed piston calipers than the j spec sliding carrier type, way better and less to go wrong/seize

[Ric]

Another thread of somehow my OEM car and oem none painted brakes is somehow better than everybody else. Jeeez.

 

There are even sites that mention big brakes can have safety concerns as they draw a lot more hydraulic fluid and DIY fitters may not have factored this into a larger reservoir.

 

This makes no sense. Once you have topped up the fluid on a freshly bled brake system the fluid does not move, or change. It's none-compressible. thats the point and how it works.

 

Yes you'd use more fluid to fill the system but it's not going to use more once bled.

[Dnk]

You can factor in other things that affect braking such as what tyres your using and the road conditions your on.

 

Its all about friction

[rider]

Jeeez..

 

Ric, you must be a big and quite possibly painted brake man. I'm sure you took into account any side effects fitting big brakes can have before heading off on track days. As for volume and pressures having no relevance I'll leave you with an extract written by an engineer. Maybe he knows what he is writing about, maybe he doesn't.

 

"Master Cylinders

Most production cars use a single master cylinder, typically with two pistons running in two bores. Each of the pistons are sized for the stock front and rear brakes. When upgrading brake systems, the master cylinder's volume and pressure must be known and accounted for."

 

Its possibly because pistons go in and out requiring different volumes and system pressure than the manufacturers engineers designed into the system and the electronic braking support systems. Just guessing there though. Maybe you can do a write up and I'll pass it onto the engineers writing these articles and see if we get some feedback for you.

[Ric]

OEM UK's here..

 

Arent you UK? or is that hood scoop a modification?

 

You didnt say anything about pressures. you said...

 

draw a lot more hydraulic fluid and DIY fitters may not have factored this into a larger reservoir.

 

As if the larger brakes use more fluid... so you need a larger reservoir...

[Mike2JZ]

[rider]

You can factor in other things that affect braking such as what tyres your using and the road conditions your on.

 

Its all about friction

 

I read reports that said the brake size doesn't appreciably impact stopping distance, its more down to how much tyre is in contact with hopefully with dry road. So fitting wider tyres would seem to be the better way to reduce stopping distance. That's probably a reason why F1 cars don't run 165's. The only benefit that consistently came from big brakes was pedal feel and heat dissipation on frequent heavy use. That's presumably why F1 cars run large disc, 6 pot brakes and split hydraulics, front and rear.

[Ric]

That's presumably why F1 cars run large disc, 6 pot brakes and split hydraulics, front and rear.

 

F1 cars use brake-by-wire, the pedals are not actually connected to the hydraulic system, thus zero pedal feel.. Perhaps a tiny amount of simulated pushback.

Edited December 29, 2016 by Ric (see edit history)

[rider]

You didnt say anything about pressures. you said......

 

I didn't say anything. I'm no braking engineer. Its what others have said. I presume they are engineers who know something about what they write about. The summation is anyone considering fitting non OE brakes because they will provide better braking may not realise that expectation. It's probably like putting a big turbo on your engine because you read somewhere it'd give you 600bhp but then wondering why it doesn't because you haven't factored in the extra fuel required.

 

Its a fascinating area and an essential safety one where any changes can have foreseen and unforeseen consequences so its good to know we may well have at least one braking systems expert amongst us.

[j_jza80]

Surely your answer is to ask one of the big brake manufacturers, instead of forum members? The brake manufacturers will be able to tell you everything you need to know.

 

Bear in mind, the big brake kits generally have alloy callipers, and floating discs on much lighter seperate bells, so there is a significant weight saving too over stock (the discs being rotating mass).

 

Also, The j spec discs are vented, but not directionally vented like the larger stock and aftermarket ones.

[Guest Budz86]

I'd rather listen to a bunch of people on this forum who have real world experience in these cars and the exact modifications you are talking about. Plenty among us have gone from Jspecs, to UKs and then to big brake kits with varying stock and aftermarket component combinations and at varying power levels from 200hp to well over 1000hp, and have abused the hell out of them and tested the limits of each setup on both road and track. Don't get me wrong, the science is useful to know but it doesn't beat getting in the car and finding out for yourself exactly which setup you prefer for the use the car will get.

[bignum]

I only changed from uk's to brembos for a wider pad choice. I couldnt go back now though as peddle feel and modulation is much improved. Still on UK rears BTW.

[j_jza80]

I only changed from uk's to brembos for a wider pad choice. I couldnt go back now though as peddle feel and modulation is much improved. Still on UK rears BTW.

 

I found the same with my F50's, great brake upgrade that can be used with the stock 2 pot rears. Although to be fair, the brand new UKs on mine have much better pedal feel than the UKs fitted to my first car had, I guess the condition of the components has an impact pedal feel.

[j_jza80]

I'd rather listen to a bunch of people on this forum who have real world experience in these cars and the exact modifications you are talking about. Plenty among us have gone from Jspecs, to UKs and then to big brake kits with varying stock and aftermarket component combinations and at varying power levels from 200hp to well over 1000hp, and have abused the hell out of them and tested the limits of each setup on both road and track. Don't get me wrong, the science is useful to know but it doesn't beat getting in the car and finding out for yourself exactly which setup you prefer for the use the car will get.

 

The pretence of this thread is to down talk brake upgrades as unnecessary if the op had actually driven a variety of Supras with different brake setups, he would quickly realise that upgrading the brakes helps with more than just aesthetics.

 

Even on my n.a., I found the stock brakes to be crap. They are wholly unsuited to anything like a BPU TT driven on track. A shame a better variety of discs aren't available for the ls400 brakes, as they're a decent upgrade over small j specs on a budget.

[Hemanhead]

I can answer for you because I have both. J specs are absolute crap, if you have them, your brakes are crap. FIN.

 

My aftermarket ones however, outbroke an auto supra on refurbished UK specs with some well recommended pads. Everything has already been mentioned regards fluids and pressure, I also dont run abs either, take what you want from that experience, but they did alot more than 'look bling' luckily for me.

[rider]

The pretence of this thread is to down talk brake upgrades as unnecessary .

 

How did you deduce a pretence? Are you our very own Mystic Meg? I actually figured its a really interesting engineering balance with potential side effects, not all good, that I for one never considered. Call me dumb if you like because maybe as a Supra owner I should know things like brakes in detail but I learned some interesting things about brakes that I never would have thought of before doing a bit of reading, so maybe now I am better educated. Or just more confused? Interesting to note though was that slightly fatter tyres could be an effective and straightforward solution for people in their road cars looking to reduce their stopping distance.

 

Brake upgrades can be assumed as unnecessary on road cars as Supras don't have a reputation for poor brakes. The question is only are they a useful upgrade and could they impact negatively on Toyota electronic braking aids unless those are reprogrammed or isolated? I don't know the answer to that but I'm sure there must be many who do amongst those who have done brake system upgrades over the decades and know what works and what doesn't. People like me who might normally just go down Halfords and pick a cheap Chinese kit off the shelf need to be aware and if that means reading up a bit to make sure all bases are covered to end up with a system configuration operating to the max capability, that can only be a good thing. Maybe we can have someone share some actual before and afterward data. Someone must have that to hand somewhere, I couldn't track down any real life comparative data online.

 

On a track car you would definitely want big brakes, no ABS and no traction control. Just big balls. Now that's more like it.

[David P]

slightly fatter tyres could be an effective and straightforward solution for people in their road cars looking to reduce their stopping distance.

 

Watch out for the 30 profile flagellation squad.

[j_jza80]

How did you deduce a pretence? Are you our very own Mystic Meg?

 

 

Everyone knows big brakes are better than small brakes. The bigger the better (especially when painted) then allied to more pots the better and the bigger the material compressed on disc the better. Except there are plenty of myth buster sites that say you need to be very specific about bigger as its not always better as bigger has no respect for how the car is set up and managed by the automated ABS and traction control systems.

 

I have a jspec on its small discs low number of pots braking and that gets up to near 160mph before the limiter cuts in and it slows down from 160mph without any real drama whenever I've done that and I've done it a lot. So tiny brakes with limited pots do work in real life, real road conditions. It seems bigger brakes come into their own predominantly to dissipate heat fade relative to smaller brakes. Stopping distance is impacted to a large extent by the area of tyre in road contact. So, reading a few sites it appears big brakes may well only be any use if you have lots of corners and chicanes to negotiate while driving as fast as you dare to around a track.

 

There are even sites that mention big brakes can have safety concerns as they draw a lot more hydraulic fluid and DIY fitters may not have factored this into a larger reservoir. Also they can fool the ABS management into thinking things are in a different state of brake panic to where they really are, making braking assistance less effective in panic situations.

So, reading between the lines non OE big brakes may well be pointless unless ragging around a track regularly and possibly a retrograde step unless allied to reprogramming or isolating the electronic braking aids. Its an interesting topic and a bit of a black arts area from the limited reading I've done into the subject area. Seems to be a few things that need to consider before just slapping big disc 6 potter on because they look good, all that looks good may not be as good as they look. Pretty key in things a critical as vehicle braking. its a fascinating area where unforeseen side effects can mitigate the perceived advantage.

 

Think I'll do some more reading.

 

Comes across as if you've already made up your mind about brake upgrades.

 

Also, you seem to have decided that brake upgrades aren't necessary on a road car, and I couldn't disagree more. A track is relatively predictable, and often has runoff on bad corners. On the road, you never know what is around the next corner. This is especially true on auto cars, which are more dependent on their brakes.

[Havard]

This thread made me lol. I nearly killed myself and Mrs H chasing Ian Ian in a set of twisties some years ago, after three relatively sharp bends the pedal did nothing when stamped on. How we got around that bend with traffic coming the other way is beyond me.

 

Could have been the fluid but I would never run a car on j-specs at pace again. As a one off stamp they are ok but nothing much beyond that.

 

H.

[j_jza80]

This thread made me lol. I nearly killed myself and Mrs H chasing Ian Ian in a set of twisties some years ago, after three relatively sharp bends the pedal did nothing when stamped on. How we got around that bend with traffic coming the other way is beyond me.

 

Could have been the fluid but I would never run a car on j-specs at pace again. As a one off stamp they are ok but nothing much beyond that.

 

H.

 

Ha ha

 

I had a similar experience in my old Corrado VR6. Had bought it about a month before, and was having a spirited drive against my friend in his EP3 Civic Type R. I was all over him, didn't have enough to get past him, but the VR6 was clearly just as fast. Unfortunately the last owner had seen fit to install EBC green stuff pads, and predictably when my friend had to slam his brakes on I almost went in to the back of him.

 

Worst brake pads I've ever used by some margin.