Improving brake feel - track use NB8C

[The Green Goblin]

Hey Fella's,

I've been using my car on the track/weekend use for a number of years now, driving aggressively etc. & I cant fault it however, in recent outings & as my driving style develops i am finding the limits of the brakes more easily, in particular i'm finding they lock up easily.. the pedal feel is kind of like an on/off switch with little to no modulation. I'm running carbotech xp10's + braided lines all round, with stock rotors & calipers, I also run performance/high temp fluid.

Million dollar question - how can i improve the overall feel & modulation whilst retaining current stopping power of my brakes & avoid easily locking up/activating ABS? I'm thinking an upgrade to a larger brake master cylinder maybe in order?

Cheers,
Jas.

[plohl]

Brake pads will make massive difference to the braking fell.
I have found the hawk dt-60s have great pedal feel, but wear relatively quickly compared to a winmax W5. PFC 11s seem to require more pedal force, but last a while. I haven't used any carbotechs, but the easiest thing you could do is try different pads. I like the winmax, but sometimes they can be hard to get.

[rossint]

What tyres are you running? These along with shocks are a big part of the braking system.
Bigger master is supposed to give you more pedal feel but I’ve mainly seen it talked about when you switch to a caliper with a smaller piston like Wilwoods in an attempt to get you back to the feel of the factory caliper.
As said, the easiest way is to try some different pads, I also run the DTC60 in an NA6 with 11.75 Wilwood upgrade. Factory booster and master. If I stomp the pedal it will lock easily but I find there’s plenty of modulation and feel to not lock up running a decent semi.

[Magpie]

Remove booster will improve feel, however I doubt this is an option.

As for Plohl’s suggestion look at pads. How is the pad wear as you could look at overhauling the calipers.

When was the fluid changed last?

Also as suggested tyres could be contributing to the lock ups. I was having a terrible session with lockup’s a few years ago switched tyres no lockup’s and a lot faster...

[manga_blue]

Also look at your spring/sway setup. At Wakefield Park the braking zones can be fairly bumpy. Truck and V8 racing there on hot days pushes up the surface like a dog piling up a rug. Soft springs with stiff sways will mean the car nose dives more under brakes, increasing negative camber to the point where you're just trying to stop the car with the inside shoulders of the tyres, and stiff sways are transferring the forces from a bump on one side over to the other side, breaking traction on that side. Try stiffer springs and softer sways.

[Roadrunner]

Brakes are largely dictated by your tyre traction. If you’re easily locking up you need stickier rubber or step down a level in brake pad friction to match your tyres.
I was running xp10 and noticed a big difference in brake power and modulation when going from road tyres to R-specs. I can seriously jump on the brakes and it just doesn’t lock up. Does generate a huge amount of heat though which leads to other problems.
It took a bit to get used to, but I was able to modulate the xp10 on the steeet tyres without locking up but you did have to start braking earlier because as soon as I pushed harder it’d lock up/trigger abs.

[bruce]

Yes, change everything.

[hks_kansei]

Brakes are largely dictated by your tyre traction. If you’re easily locking up you need stickier rubber or step down a level in brake pad friction to match your tyres.
I was running xp10 and noticed a big difference in brake power and modulation when going from road tyres to R-specs. I can seriously jump on the brakes and it just doesn’t lock up. Does generate a huge amount of heat though which leads to other problems.
It took a bit to get used to, but I was able to modulate the xp10 on the steeet tyres without locking up but you did have to start braking earlier because as soon as I pushed harder it’d lock up/trigger abs.

I agree here.

tyres make a massive difference to percieved brake feel.

Too little grip (since brakes can only slow a car down as far as the tyres will allow it to) and it locks up, and the brakes feel super touchy.

Too much grip and the pedal feels spongy, since you end up being able to push a LOT harder without lockup.


Of course, the actual pedal feel doesnt change, but mentally it feels like it does, since you have an expectation of what X pedal pressure should feel like as far as G forces.

It's all about balancing the setup, which is why manufacturers dont just throw giant rotors on every car they make. (well, and cost)






One of my previous cars was like this, a shitty Mondeo, but it braked fine and could lock the fronts if I needed to.
I then put on different wheels, with much wider tyres, and used a much softer compound.
The result was that it was almost impossible to lock a wheel in the dry, the pedal felt like it kept going lower and spongier since it now had the grip there to actually use pretty much full pressure.
It would also absolutely cook the pads after one stop, literally smoke from behind the wheels.

[The Green Goblin]

thanks for the input, to answer all;

- tyres are hankook rs3's which have seen better days, they have about 40-60% tread
- suspension set up - tein monosports set to above medium setting, whiteline swaybars front & rear with supermiata end links. I've had people comment/ride along & say the car handles well & stops very well.
- last brake fluid change happened 5000km's ago when the car hit 100,000kms
- the carbotech's have been on the car for 5000km's.. they do generate decent heat, I seem to get a long service period from them.. as i dont drive the car too much
- carbotech xp10's are well known in the mx5 community, proven, & recommended by multiple workshops here & in states.. they have a hard initial bite, but also maintain it throughout a usual 15-20 min sesh.
- i dont seem to have issues at wakefield, i noticed this more at luddenham where to keep most momentum, i broke late & hard as possible.. i just found them to activate the ABS too easily..

conscious this is also a subjective thing i.e. my braking hard can be someone's braking extremely hard & me wanting more modulation doesn't necessarily mean there isnt any. anywho, im just trying to improve it where i can without performing a major overhaul of the discs & calipers..

[rossint]

You’re at the limit of those tyres would be my pick, time for an R compound.

[wasp47]

Have you fitted a master cylinder brace, easy and cheap to make. The firewall flexes more than you think!

[rascal]

Have you fitted a master cylinder brace, easy and cheap to make. The firewall flexes more than you think!

That would make it worse.
He already feels like the brakes are an on/off switch. Removing the cushion of the firewall flex would increase this.

[16bit]

my opinion would be the tyres have been heat cycled too much and are probably on the way our regardless of amount of tread left.

i think given the rest of your setup is relatively proven for track use globally by a very, very large community it might be time to buy some new tyres.

either that OR you could try some of this as a cheap attempt to see if it helps/confirms that the tyres are the weak link - http://www.revolutionracegear.com.au/?P ... mary&CDO=0
http://www.autosport.com.au/octopus-gri ... oftener-1l

[1600Dave]

I'm thinking an upgrade to a larger brake master cylinder maybe in order?

Larger master will give less feel as it "pushes" more volume of brake fluid for less pedal travel. Pedal will feel "harder" or more "wooden".

Smaller master may give more feel, at the expense of needing more "shove" in the pedal and more possibility of running oit of pedal travel (ie pedal going all the way to the floor).

And yeah, best thing for more "feel" is to get rid of the booster.

[The Green Goblin]

Have you fitted a master cylinder brace, easy and cheap to make. The firewall flexes more than you think!

interesting cause someone who i met at the track recently said this.. mentioned it makes a tonne of difference.

my opinion would be the tyres have been heat cycled too much and are probably on the way our regardless of amount of tread left.

i think given the rest of your setup is relatively proven for track use globally by a very, very large community it might be time to buy some new tyres.

either that OR you could try some of this as a cheap attempt to see if it helps/confirms that the tyres are the weak link - http://www.revolutionracegear.com.au/?P ... mary&CDO=0
http://www.autosport.com.au/octopus-gri ... oftener-1l

You’re at the limit of those tyres would be my pick, time for an R compound.

My intention is to upgrade the tyres shortly.. & run toyo r888r's - lets see if they do the trick. Lastly, does a fluid flush help in this space?

cheers,
Jas.