How Good Are Our Brakes?

How impressive are the AP Racing 2 pot brakes? I read that the 4 pot upgrade isn't worth it for the road and they are not much better than the 2 pot but can handle abuse on track better
Can they loose performance over time?

I have my fluid changed every year (race)
Grooved discs and Mintex M1155s
ABS disabled
AD08R tyres

Yes they are okay and work but I always expected more from them if I'm honest.
I personally found the Mitsubshi Evo that weighs 1500kg (4 pot brembo) much better when surely the lightweight vx should be.

Having regular access to a Alfa 4C with brembo the brakes are monsters in conparison with just std road pads from Alfa. If I brake hard I feel like real geniune G force and the VX just doesn't feel the same. I don't get fad or long pedal just don't have the punch.

AP Racing are known for being one of the best! What's the issue? Can they loose performance over time or am I just expecting too much from mine?

Would rebuilding the front callipers make a difference?

Edited by scw02102, 20 August 2019 - 08:35 PM.

I haven't experienced the 4 pots but I have the standard 2 pots with pagid RS29s front and 42 rear and fluid change AFR) every 2 track days.

I know what you mean about comparing our brakes to others like brand new cars. I swore that a Toyota Aygo I hired had better brakes than the vx but I wasn't throwing tge Aygo around a track and repeatedly asking it to stop......

Sent from my LG-H815 using Tapatalk

Brakes are one of those things you end up compensating for without realising it, as they deteriorate, until you try another vehicle!

 

You end up with a slightly sticky caliper, some air in the system (or old fluid), and the inside of the disc has a build up of corrosion.. Some decent maintenance, with some fresh discs, pads and fluid (properly bleed), and you may find it brings the performance you expect.

 

But in general, with a better pad compound, the VX / Lotus braking system is decently spec'ed for hard road use.

 

Problem is that alot of newer cars have greater servo assistance, which makes them feel more aggressive and 'powerful' (bit like the modern approach to throttle calibration). VX brakes aren't too over-servo'd (not a word) and the vacuum hose is probably a bit leaky on a few cars by now.

The other cars you mention may well be over servod as well giving the impression they have mighty stoppers but would probably last 2 laps on track. 

 

Initial bad bite and ensuring thorough bleeding are the two biggest contributors after tyres. Tyres are always the first thing people overlook. They are a big part of your braking system and AD08R are not a track biased tyre imho and you'll notice a huge difference moving to say a R888R

You may not have the correct vacuum arriving at the servo (in our 20 year old tired cars!), it's easy to plumb a T-piece into the pipework before the servo and put an in-cabin gauge on the end of it. You should see approx 0.8 of a Bar of vacuum (i.e. approx -27 In/Hg) on a healthy engine when at idle.

 

When I did this many years ago, I discovered that I was only getting about 0.5 Bar of vacuum due to my cam overlap. Other things like a failed 1-way valve, a split/tired vacuum pipe that runs up the sill, or even a failing diaphragm in the servo can cause vacuum loss too.

 

I'm not sure what cams etc you have, but a permanent solution to gaining more vacuum is to install a vacuum pump like most modern deisel cars have. I've put a heavy duty Hela one on mine (from the VW range of diesels), which regulates the vacuum by an adjustable vacuum knob.

 

HTH.

Edited by Nev, 21 August 2019 - 07:39 AM.

Fit decent pads.

 

I just went to RC6 and they are a massive upgrade on the RC5+

 

The calipers on the VX are the same as the S2 Elise/Exige (as we all know)

 

ALL of the Elise Trophy both UK and Euro use original calipers with different disc + pad Combos (mostly Performance Friction) they are able to out brake pretty much anything on a track day - Also agree with Jon that tyres are hugely important.

 

Braided lines, good pads (PF or similar), Good Fluid (Motul, PF, Millers), good quality discs and either Avon ZZR's or Toyo R888R's 

 

With that kind of set up you shouldn't have any issues

 

Can't comment on your specific driving ability but sometimes a day with a driver coach can also work wonders.

 

MBR 

The other cars you mention may well be over servod as well giving the impression they have mighty stoppers but would probably last 2 laps on track.

This! Most modern cars have a huge initial over-servo effect on very light brake applications. Aka. breathe on the brake pedal and your head goes through the windscreen.

 

However.. Physics still apply and I find that after this initial excessive 'bite' they tend to be fairly mediocre when it comes to full braking (not much extra happening after this even when pressing harder) and wooden/lifeless pedal feel. Not to mention that they fade badly after some repeated stops.

 

Nice case in point.. This video...

 

https://www.youtube....h?v=kSoQtwbpcGU

 

AMG E-type with massive brakes, but notice how after not even a single lap Frank already mentions that the brakes seem to be fading and Lewis confirms..

 

Not to mention most cars these days also have some form of EBA (emergeny brake assist) which kicks in when you exeed a certain speed at which the pedal is depressed giving an extra 'head snap' feeling.

 

This is all done on regular cars because data logs from crashed cars have shown that most drivers never reach more that 70-80% pedal pressure even in an emergency. (with loads of people actually scared of the vibrating brake pedal when ABS kicks in and letting off as a result..)

 

IMHO the VX/Speedster is nicely setup (as is my old Pug 107    ). I still prefer my un-assisted Elise, but the amount of assist on the VX/Speedster is pretty spot-on. Don't want it to be too 'grabby' as the lack of weight on the front axle means you can lock up the fronts if the 'grab' is too agressive. Need a little time for the weight transfer to load up the front and allow you to progressively ramp up the pedal pressure.

 

The lack of 'dive' on the VX compared to front-engined cars also makes it feel a lot less dramatic and it seems like you are not slowing down as much, but when you do some repeated brake runs on a test track you find out these little cars are often easily the ones that consistently have the same brake distance the 1st and 10th time.

 

The 'softer' initial bite on the VX  is IMHO a pro, not a con as it allows you to lean into the braking without upsetting the car immediately.

 

Bye, Arno.

The other cars you mention may well be over servod as well giving the impression they have mighty stoppers but would probably last 2 laps on track.

Initial bad bite and ensuring thorough bleeding are the two biggest contributors after tyres. Tyres are always the first thing people overlook. They are a big part of your braking system and AD08R are not a track biased tyre imho and you'll notice a huge difference moving to say a R888R

This.

I think from what you are saying that it's braking power that you're underwhelmed with rather than long session fading?

If you can trigger your abs or lock the wheels then you have enough stopping power, and using your brakes better will make them last longer. Having been a passenger on track with much better drivers than me, the 2 pot vx brakes are like hitting a wall if modulated properly. By comparison the heavily assisted brakes in my Kia Rio are super aggressive and you'd think they were ceramic!

Tyres make a huge difference though.

Yes Pete_R its not fading just not as good as I hoped. ABS is disabled and does lock up if I push them hard, in fact the fronts lock up fairly easily hence I ditched my Eagle F1 for AD08R which helped a bit.

 

Problem is this is a road car so didn't want RC6 etc.. as they are not good from cold/road use???

Hence I run AD08R as its a road tyre, I don't think the 888R will get heat into them for normal road use. My track car (MX5 turbo) takes at least 2/3 laps before the track tyres come in and on the road I cant get that heat into them easily.

I agree what you mean about new cars having over powering servos. 
I don't get fade and they can take abuse but just wasn't impressed with out and out performance.

I will do a few 70-0mph with my cars and see what happens, maybe I will be surprised. (joys of having a few to choose from)
If they are poor I will check the vacuum as above

 

Thanks guys

RC5+ and RC6 are fine from cold, as are semi slick tyres, the temp you need on a track is way outside what you would ever need on the road.. semi slicks cold will grip better than an AD08 when cold, and they will be quicker to warm up too.. semi's have a softer compound and there is more surface area.. the downsides of semis are the wear rate and the water dissipation..  

 

many years ago i did some tests. 

 

Test 1

*ABS ON*
Max Acceleration - 0.22 G
Max Braking - 0.79 G
Max Lateral - 0.54 G (Left)

 

Test 2

*ABS ON*

Max Acceleration - 0.54 G

Max Braking - 0.91 G

Max Lateral - 0.88 G (Left)

 

Test 3

*ABS OFF*

Max Acceleration - 0.54 G
Max Braking - 0.90 G
Max Lateral - 1.01 G (Right)

 

Edited by chris_uk, 21 August 2019 - 01:58 PM.

RC6 have terrific bite from cold. It's the dust and noise you might not like on a road only car. I raced on Pagid plain discs, RC6 pads and ATE Typ200 fluid for 6 years on a VX and never had a problem. They were also cooled

They're fine, but the ABS is probably the most laughably dangerous 'feature' ever applied to a modern car.

I changes to AP four pots. Was not very impressed. 

But they do look good. 

I changed from the mintex 1155 on the front to ds2500.... Fook me what a difference on track.... I've only done 3 track days so can't offer the same level of advice as the experienced folk on here but I'm going to look at replacing my rears with the ds2500..... Also the pads seem to last a lot better, more meat on them and so much less dust on my wheels.

Maybe will give the RC6 ago then, had it in my head they didn't work from cold so that good to know they do

Always heard good things about Performance Friction too

the problem is a poor distribution of the braking force, not weak calipers. it brakes too much on the front and blocks itself in relation to the back. the solution is weak serial pads on the front and strong rc6 on the back

I just did the 4 pot upgrade (Big version of the EliseParts 4 pots on the front, original 2 pot APs on the rear).  It took me a while and some other mods (including a Cayenne master cylinder) in order to get the feel I wanted from them, but that's another story.

 

Having had RC6 in the standard set up and moved to RC6 in the big brake set up, the difference in stopping power isn't incredible, however, zero fade on the track without using sympathy for 5 laps of Brands GP a few weeks ago in the 25 degree heat.  I also run R888R and the thing sends the skin on my face slapping into the windscreen and is waaayyyy better than my 2017 RS Clio Trophy on the brakes (which I took to Bedford earlier this year).

 

I also don't find any issue with too much front bias on the brakes any more, probably because solid two pot calipers flex less than the original floating calipers on the rear meaning less squeezing force on the disc is lost in the caliper.

 

I absolutely, 100% would not recommend this mod if you do more than a handful of road miles (mine is driven to tracks and back and that is it these days).  They can be snatchy when cold and squeal like an entire litter of piglets all at the same time.  Each corner makes a slightly different pitched squeal.  It's a horrific and embarrassing cacophony to be honest.  Once they are warm on the track though

 

Upgrade your pads and do the other checks people mention above and that will make a huge difference.  I only went to the 4s up front to try and eliminate fade on track due to overheating and I had a fooked rear caliper too

 

 

Edited by TheRealVXed, 27 August 2019 - 04:18 PM.

the problem is a poor distribution of the braking force, not weak calipers. it brakes too much on the front and blocks itself in relation to the back. the solution is weak serial pads on the front and strong rc6 on the back

 

Some say RC5 front and RC6 on the rears, but that is maybe a bit too much rear bias.

I fitted RC6E on the fronts, which are between the 5 and 6. Together with normal RC6 rears I can get all discs nice blueish...   

About front bias... Nobody speaks about wheel size.
Does a smaller front wheel (16 in) give more front bias ??
Wheels act as a lever and the usefull braking forces take place between tyres and road...