Understanding big non OE brakes

[rider]

 

 

 

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

 

I have cars with all sorts of brakes, mostly non assisted and lots of drums including an all drum Land Rover. So I find the Supra standard brakes pretty good by comparison. I did find one piece of science to support larger rotors and thats Force = Work X Distance. So larger rotors for the same size wheel (including tyres) will require less hydraulic pressure to achieve the same slowing force translated into friction and heat. This is presumably why people say bigger brakes have a better fell, because they require less effort to achieve the same braking performance. But, less effort doesn't invariably mean you stop or slow any quicker because even on tiny brakes you can lock the wheels with the ABS disconnected. See what little gems you find when you read into a subject. Still the biggest upside everyone zones in on is heat dissipation to reduce the potential for fluid boiling and vapour locks.

 

Still no data though. I just cannot find any supporting data. It'd be good to see the actual figures in distance and g force deceleration for an OE jspec setup compared to UK spec compared to 6 potters on larger still rotors using the same wheel size and if possible pad materials. If I spent £1k+ on brake mods I'd want to go demonstrate it'd been money well spent so surely someone has to have the data. Then it'd be obvious what advantages there are or indeed aren't in everyday open road use, forget track that's a given.

[j_jza80]

Unfortunately, all the info you want on the small j spec brakes will be in Japanese. If you've got the time and inclination to search it out though, please feel free to share.

 

Otherwise, you'll just have to accept what you're being told. That, or set up some benchmarking tests with a variety of Supras

 

Besides, I doubt you can really quantify 'pedal feel'.

Edited December 29, 2016 by j_jza80 (see edit history)

[rider]

Finally located real test data on a Nissan 350z using different brake and tyre combinations. Pretty much clears things up wrt actual stopping performance relative to brake setup.

 

 

https://www.zeckhausen.com/catalog/index.php?cPath=6446_6565

[Sheefa]

Read.

 

http://www.mkivsupra.net/vbb/showthread.php?225007-Big-Brake-Kits-Real-Numbers&highlight=Brake+comparison

[Sheefa]

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

 

Too true.....again.

 

http://www.mkivsupra.net/vbb/showthread.php?326965-What-does-J-spec-and-UK-spec-really-mean

Edited December 30, 2016 by Sheefa (see edit history)

[Nic]

The larger 4pot/2pot OEM brakes were designed specifically for the Supra and are a proven upgrade over the smaller 2pot/1pot setup, they won't stop the car any quicker but provide much improved pedal feel, require less pedal pressure, need less maintenance and will stop the cars repeatedly before fading (something the smaller brakes will struggle to do). They can be optimised with lighter 2 piece discs, braided lines, better fluid and pads and a brake master cylinder stopper which significant improves pedal feel.

 

Some words on the subject by CW http://www.mkivsupra.net/vbb/showthread.php?318433-Best-brake-upgrade-for-a-Supra&p=3986902&viewfull=1#post3986902

[rider]

Too true.....again.

 

http://www.mkivsupra.net/vbb/showthread.php?326965-What-does-J-spec-and-UK-spec-really-mean

 

I think its a case of Toyota engineers probably knew something about what they were doing. The data clears up whether big brake mods have any impact in a road car which is one question I was asking myself. Seems the journal and mag threads on big brakes I have been reading are born out in reality testing. I'm sure the data will be a revelation to many, probably not you though. You will definitely see the benefit of brake mods when you take your car onto the track. Any dates planned?

[rider]

The larger 4pot/2pot OEM brakes were designed specifically for the Supra and are a proven upgrade over the smaller 2pot/1pot setup, they won't stop the car any quicker but provide much improved pedal feel, require less pedal pressure, need less maintenance and will stop the cars repeatedly before fading (something the smaller brakes will struggle to do). [/url]

 

Nic, you know your parts really well. Do you know what is required to perform a complete jspec brake to uk spec brake upgrade?

 

I now know you wouldn't want to change the fronts and forget the rears as that would alter the braking bias front to back so the shopping list would start off with:

 

4 rotors

8 pads

4 callipers

4 dust shields

potentially 4 new road wheels

 

On other parts

Are the ABS sensors the same?

Is the master cylinder the same?

Is the ABS ECU the same?

Are the hubs the same?

Are the flexible hose couplings the same?

 

Do you have an idea roughly how much would it cost with new parts using OE pads to do the complete j to uk brake upgrade?

Edited December 30, 2016 by rider (see edit history)

[j_jza80]

The hubs, abs sensors etc are untouched. The heatshields either need some slight alteration or replacing with the correct ones (some remove them). The master cylinder is fine.

 

There are also anti squeal shims, and you might as well fit new braided lines.

 

Will probably cost circa £2k front and rear with new hoses: http://www.garagewhifbitz.co.uk/toyota/supra/brake-parts/big-brake-kits.html

 

A fraction of the cost of a brembo/ap/Alcon upgrade.

[Scooter]

The point is stock pads of either brake type can be overwhelmed giving fade. The smaller j specs will get hotter quicker as they are smaller and so have less heat sink capability. When really hot even with uprated pads you can get fade from the fluid boiling up.

 

So those saying jspecs nearly killed them experienced one of the above, probably in combination with a seized slider or two, definitely a scary experience but fully working calipers, expensive pads and expensive fluid would have seen them ok. Harvard wasn't scared until the brake pedal did nothing (fair enough!!) he wasn't complaining of poor brake performance until he had zero!

 

So the j specs are marginal as they come, crap even if you are very heavy on them, but £400 for pads and fluid and you can have a non fading setup a la CW's old track day setup.

[j_jza80]

It's not just the heat dissipation though. No matter what you do to the smaller brakes, they will always have a smaller disc diameter and overall piston face area.

 

Interestingly (or not ), looking at those 350z figures posted before, a stock supra on the larger oem brakes and stock tyres has a shorter stopping distance than a 350z with the full stoptech upgrade. Surprising given the Z is 10 years younger, and lighter than the Supra.

[Scooter]

It's not just the heat dissipation though. No matter what you do to the smaller brakes, they will always have a smaller disc diameter and overall piston face area.

 

.

 

True but my point is the fade can be dialled out of j specs, the upgrades I mentioned will see better performance than stock uks with stock pads, but yes all things being equal the uk's will have better fade resistance.

 

some people don't find the limits of stock setups, some need to upgrade something, when j specs are tired the refurb costs or new caliper costs aren't much lower than new uk's hence the upgrade at that point makes far more sense.

 

I'm only waving the flag for j specs as they are not inherently terrible/crap and can be all you need depending on circumstances. But whatever setup you have if you are going to be hard on your brakes, you are going to need to spend a few quid on pads and fluid to ensure you get the best from them, calipers are just one part of it. Look at bignum, no decent pads has meant he's ditched the uk's through no fault of the caliper itself, just through lack of pad support/production.

[j_jza80]

But if you're going to start putting money into j specs, perhaps a better route would be the Lexus ls400 front upgrade. I would certainly say so on a road car where pad / disc choice isnt as crucial (although I think CW offers his pads for these now). These can be picked up for less than £200, and provide some of the benefits of the UK fronts without the cost.

[rider]

I think its been useful, for me anyway to find out more about brakes and if anyone learns something, like me, that they didn't know or appreciate before - that's fantastic.

 

Things I feel I've learnt or had confirmed from the viewpoint of strictly a on the Queens highway road user.

 

1. Bigger brakes, all things being equal, aren't going to pull you up any noticeable distance shorter than j stock brakes.

2. Bigger, wider tyres are the best way to maximise grip and through that, shorter stop distances.

3. Bigger brakes do dissipate heat much faster but that's not going to be an issue in every day road use.

4. You shouldn't just change the fronts setup without also doing corresponding changes to the rear brakes otherwise you unbalance system pressures and you deviate from the factory front to rear bias.

 

My conclusion from having done a good amount of reading around the subject in the last 24 hours is pad choice and tyre choice are way more important that rotor size and numbers of pots in determining the braking performance of a Toyota Supra from any speed in normal road use. The report I reference mentioned after going on to do a car specific setup through trial and error they could reduce the braking distance by almost 20% but the off the shelf options only delivered a 1% to 2% improvement in stopping distance. So a bespoke system is much better than a generic system which is probably why OE bespoke systems tend to work well in the first place.

 

Bigger brakes, especially moving to another OE setup such as the UK standard, are going to provide better endurance braking for those doing spirited road driving on winding roads. But possibly nothing that fresh brake fluid and racing pads couldn't match on the smaller j brakes. So UK brake upgrades for those still on smaller j brakes are a good way to go but probably, for me anyway, only worthwhile when the current brakes are worn out and in need of replacement and I also fancy gaining a new set of road wheels to.

[Mike2JZ]

I've had the 2/1 pot calipers on mine since day 1. I've tried a host of different pads & fluids.

 

For daily driving they really aren't a problem, the occasional hard braking here or there. The problems comes once you start driving like an asshole and use the brakes hard.

 

They may stop once or twice nicely from 100+ leptons, or they may give a few minutes of confidence inspiring braking but once you start generating sustained heat and you start smelling the pads, I can guarantee you that the pedal will start to feel softer and will require a lot more effort to use then it was a few minutes ago. It sucks

 

All the heat that these smaller brakes can't dissipate means you need to be spending more time maintaining the brake system afterwards as well. Checking sliding systems work, lubing them, rebleeding the system, checking wear on pads etc etc.

 

And at the time this was with an NA. I bet with more power the threshold for the heat being generated on a tough drive would be even less.

 

I've thought about sticking with the 2/1's on mine, but upgrading to DBA discs, braided lines, different sets of pads, the full works in order to counter the heat as best as possible.

But when you put all that into £££, you're not really that far off just getting the 4/2's which have a higher braking potential with the same set of mods.

[j_jza80]

1. Bigger brakes, all things being equal, aren't going to pull you up any noticeable distance shorter than j stock brakes.

2. Bigger, wider tyres are the best way to maximise grip and through that, shorter stop distances.

3. Bigger brakes do dissipate heat much faster but that's not going to be an issue in every day road use.

4. You shouldn't just change the fronts setup without also doing corresponding changes to the rear brakes otherwise you unbalance system pressures and you deviate from the factory front to rear bias.

 

 

1. Wrong. It may also require a tyre upgrade, but specifying a different brake setup can absolutely result in shorter stopping distance.

2. Yes. The brakes are only as good as the tyres. But you shouldn't be skimping on tyre choice anyway.

3. Wrong. Fast road use involves building up heat in the brake system, as the brakes are used repeatedly, so heat management is very important. If you drive like a granny, you've bought the wrong car

4. Actually, the fronts can be changed *relatively* safely if you know the fronts are at least equivalent to oe. It's the rears which cause the biggest issue, as if you introduce too much rear bias the car will naturally want to spin under heavy braking. For example, swapping the fronts to Lexus ls400 and keeping the rears stock j spec is tried and tested, and works well.

 

Probably worth mentioning that the smaller brakes aren't designed for use in sporty cars. They first appeared on the Lexus LS400 in the late 80s, whereas the bigger 4 / 2 pot setup was bespoke to the Supra, and world beating. Make of that what you will.

[rider]

1. Wrong.

 

I can see you haven't learned anything.

 

As I said yesterday, its always good to have one resident expert. Hopefully you can spare some time to do a comprehensive brake write up as I suggested yesterday that I can send to the journal and article authors and maybe we can get you some feedback for you and us all because I'm not convinced, having read what I've read, that you really do know as much about the subject area as you appear to think you do.

[adam1983]

I have had 3 different brake setups over the years, all on supras.

 

Stock jspec: worked fine for general use but didn't fill me with confidence when put under heavy braking more than a couple of times. The pedal feel on these was quite spongy in my opinion.

 

K-sport 365mm discs 8 pot front 6 pot rear: first thing I noticed with this setup was the much grippier feel from the pedal. It's quite hard to explain without feeling yourself but it gives you a better feedback. Performance wise I would say it had slightly better stopping distances than the jspecs but the main advantage was that it would not fade like the jspecs did. This alone made it worthwhile in comparison as it was much more predictable what you were going to get from pressing the brakes hard.

 

Uk spec: pedal feel on these is a bit more spongy than the ksports but a lot better than the jspecs. Performance wise I would say is the same as the ksports if not better. It would not be worth upgrading from uk spec in my opinion. Only thing worth doing would be better pads and braided lines.

[rider]

Uk spec: pedal feel on these is a bit more spongy than the ksports but a lot better than the jspecs.

 

Someone PMd me earlier to say their UK brake setup is really good but also mentioned a spongy feel. I'll buy a OE UK setup ready to fit when my current brakes are no longer suited to my spirited driving or wear out. The car doesn't travel far these days so it could be a while.

[David P]

Only thing worth doing would be better pads and braided lines.

 

Don't forget the paint and go faster stickers.

[j_jza80]

I can see you haven't learned anything.

 

As I said yesterday, its always good to have one resident expert. Hopefully you can spare some time to do a comprehensive brake write up as I suggested yesterday that I can send to the journal and article authors and maybe we can get you some feedback for you and us all because I'm not convinced, having read what I've read, that you really do know as much about the subject area as you appear to think you do.

 

Was I supposed to learn something? You started this thread with an agenda, and surprise surprise, your 'findings' are the same as your preconceptions.

 

Meanwhile, I've owned 4 Supras, which have had 2 sets of small j spec brakes, 2 sets of UK brakes (with different discs/pad choices), and a set of Brembo F50s. I've driven these cars is all conditions, and circumstances, from the daily commute, to 3000 mile road trips, and a few sessions on the Nurburgring. I'm not a brake expert, and have never claimed to be, but I've got a lot of hands on experience of this subject. By the sounds of it, you've only had a Supra with small brakes, so your opinion doesn't really count for anything.

[rider]

Don't forget the paint and go faster stickers.

 

LOL - I've got granddad on board stickers and glow in the dark paint, that'd help me find the car at night.

[rider]

Was I supposed to learn something? You started this thread with an agenda, and surprise surprise, your 'findings' are the same as your preconceptions.

 

This is a revolving door, my turn.

 

The preconceptions were, rather, observations from doing a bit of research. I found them to be something that challenged my generalised preconceptions rather than reinforced them. I struggled to believe them fully, even though they were consistent comments amongst many commentators who read like they actually knew what they were writing about. I couldn't be a convert until I had some raw data to back them up, that's the science background in me still finding a way to show itself. That was a hard find, lots of hearsay where everyone has an opinion but raw data - not at all easy to track down. But when you have all the published 'experts' saying one thing and then some real and raw data comes to light (I'm going to claim a gold star for tracking that down) backing up what they are saying I'm probably going to believe it. I'm a convert, I've been educated.

[Ric]

I'm a c...

 

It's true.

[Kendo11]

Why on earth did I open up this thread.