8B Brakes on NA6 Sprints

[Dweezle]

Hi all,

I have been using stock NA6 brakes with Carbotech Pads and not really had any issues but would love a little extra stopping power during Supersprints and Club Days.

My worry is the extra weight, of which their appears to be a lot, will hinder more than help my lap times.
Especially as I am only doing 3-5 Laps maximum usually.

I know in a longer race style event that they would help with heat management but will I see any benefits in a Sprint?

The classes I run in allow me to use the larger brakes so I am very tempted. Especially as I will be due soon for new pads.

What do we all think ?

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[MattR]

If the current brakes are doing the job for what you want to do then don't change.

Just make sure that the rotors are in good condition along with the pads and that you flush the fluid reasonable often, and use a good quality fluid, but no need to spend stupid amounts on big brand name fluid. Personally i find the Penrite Sin or equivalent Penrite fluid, as they change names every few months, more than adequate for my NA6 and also my old race car.

The smaller brakes being lighter are better for the unsprung mass of the car.

It is possible to "overbrake" a car, and yes the extra weight can be detrimental to overall lap times and performance.

[Dweezle]

Thanks for the reply.

They work fine but I would love to be able to brake later.
I know where I have to brake with my current setup and if bigger allows me to brake a further 10m or more later I would be interested.

I guess my question is does the weight of the 8B brakes diminish any gains in braking performance to actually reduce lap times ??

I have a 1.6 making 80-85rwkw and am doing 1.13.5 at Wakefield Park on Ad08.

Could I see an improvement with the bigger but heavier brakes ?


Edit (sorry for some reason I only saw your first sentence when I replied)

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[Magpie]

I would look at pads first and see if this helps. Again MattR's suggestion on brake fluids as well should be considered. If changing pads make sure you follow the bed in procedure. If going to an agressive pad consider having a set of rotors specifically for those pads and when on the road swap to another set of rotors and pads. I have 3 sets of rotors and 2 sets of calipers.

Pad wise look at something like Winmax W3's front/rear or go W5 on the front and W3 on the rear. Note the W5 are an agressive pad, will take a lot of abuse, are dusty and take heat to get the best from them. Give Marty a ring at http://www.motorsportbrakes.com.au/contacts/ and discuss your needs.

Another popular sprint pad are the A1RM's from http://brakesdirect.com.au/aus/qfm-db1170-a1rm-brake-pads.html.

The bigger rotors help with heat management as well as provide a larger area for the pads to 'bite' into. With this in mind maybe duct some air onto the rotors first as well as a pad change and see if that helps. At least if you go to larger brakes you will already have air ducts.

[madjak]

The issues I had with the stock NA6 brakes was that I just couldn't get enough rear bias. With aggressive race pads I also chewed through my front rotors and pads as I think they were just getting way too hot. I also found that when the pads were cold they were very difficult to modulate which made the first few stops in hillclimbs / autotests very difficult to get right. I think this is a combination of small pad area and low leverage due to the small disks.

I have just upgraded to Wilwood rotors front and rear, Wilwood calipers up front and stock calipers on an offset bracket at the rear. I ran them for the first time last weekend and I actually had to wind my proportioning valve in a bit to stop the rear overbraking. So far on the track I've found them brilliant, but really so were my stock NA6 brakes... the real test will be on the hillclimbs and sprints where pad temp is down.

If your happy going through pads and rotors then the stock NA6 fronts are fine. Just run high friction pads and it will stop fine when at temp. It might be worth upgrading to the larger rear so you can get more rear bias. If corner weight is an issue you could always put the sports caliber (larger piston size) on the stock rear NA6 rotors for more rear bias as well.

[Dweezle]

Thanks all,

I am using Penrite Fluid and its been great.
The Carbotechs on the front are great but i just remembered i am still running my old Hawk HP PLus on the rear.
You must be right about the rear as they just do not seem to wear down.

I am almost through 3 sets of front pads before the rears need changing.

Would a proportioning valve help this or is it better to just increase the rear Rotor and Pad?

I do find it hard in a late brake situation to be perfectly on the limit of traction without a lockup.
I assume this is the smaller pad and rotor at play here.

[Magpie]

Limit of traction is a tyre issue not a brake issue. The question is how much brake can you use before you reach the limit of tyre grip. A more agressive rear pad could help without going to a bias proportioning valve.

A change in pad type will give you more inital bite as well as be able to work at higher temps when a normal pad would start to loose bite. However you will still be governed by your tyre grip irrespective of how much brake force you have, as MattR stated it is possible to over brake the car.

What tyres are you running?

[madjak]

Yes and tyres too. I had issues when my tyres were cold but once warm they had so much grip I didn't lock them. These were very grippy Advans though.

With stock rotors you can basically remove the stock proportioning valve and run it full open. Even with good pads in the rear you still won't get enough rear bias. If it's a road car be very careful what you change though! The wilwood valves are fairly cheap so I'd recommend putting one of them in as there may be times when you want less rear... not that i ever did.

I'd also run the same pads front and rear. On my car the rear pads were hardly worn and the fronts destroyed.

[madjak]

Limit of traction is a tyre issue not a brake issue.

Generally yes, but I found with the small stock NA6 fronts, the very aggressive race pads would cause lockups when cold due to the high initial bite. Sure my tyres were cold as well but I don't think it's a tyre issue as such. I just found it extremely hard to know how hard to press coming in on that first big stop with the smaller brakes. Then throughout the event the brakes changed constantly till they got to temp and started to work. Since the upgrade I think I have way more control and feel when they are cold, but then I have changed rotors, calipers, brake lines and pads so it could be any of those.

[MattR]

Dweezle, that sounds about right. I run HP plus front and rear on my car and get about 3 front pads to the one set of rears. Remember, the rears do not a lot of braking compared to the fronts.

My car is a NA6 and the Hawk HP plus is all that it needs. There is no need for me to go to a harder pad. You want to run the softest pad you can get away with. For a 3-5 sprint your pads will be fine, maybe look at making sure the compounds front to rear will work. Check with the Carbotech retailer to see what they would suggest for the rear if the hawks aren't suitable. As I said I run the HP Plus pads front and rear and they work wellon the road and the track.

To brake later, here is a little trick I use:

Lift off at your normal brake point, but instead of hitting the brake pedal count to 3 slowly before hitting the brakes. You will probaly get to 1 1/2, maybe 2 in the count and your foot will be on the brakes, but I bet you will make the corner and you will have gained your 10m or so. Once comfortable, that 10 m becomes the new brake point and then start again with the count, you will get to a point where you won't allow yourself to go any deeper due to self preservation kicking in, but you will be braking about 20-30m deeper than before.

With a standard motor I am usually the 2nd fastest in the 1600 modified class in the Qld club days with a car that runs old R888's and BC V1 series coilovers, and extractors, the rest is 220,000km old car.

[speed]

Just out if curiosity, What is the factory brake bias for a NA6 - 80/20?


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[Magpie]

I was collecting this data. Previous comments noted that the proportioning valve story is not as simple as I have made it out as, put it gives you an idea.

For my setup, front wheel lock up with FZ201's and Winmax W5's happens at about 780 PSI. I've offered Dweezle a test drive of my setup when I come down for the club track day on 12/04/15.

Master cylinder diameter
1900-00 22.22mm
2001-05 24.0mm

Brake Booster
1990-00 4.74:1
2001-05 9.7:1 (ABS)
2001-05 6.4:1 (NO ABS)

Pedal Ratio
1900-00 4:1
2001-05

Caliper Piston Dia
NA (F) 51.1mm (R) 31.75mm
NB (F) 51.1mm (R) 31.75mm
NB8B (F) 54mm (R) 34.9mm

Proportioning valve
NA Knee Point 427 PSI, 60% of front pressure (597 PSI at 995 PSI)
NB
NB8B

Pedal Travel
NA 133mm
NB

[project.r.racing]

Limit of traction is a tyre issue not a brake issue.

Generally yes, but I found with the small stock NA6 fronts, the very aggressive race pads would cause lockups when cold due to the high initial bite.

Say what? Race pads dont have high initial bite when cold.

I think you find you tyre setup needs some work. Either psi needs to be looked at, and ways of getting heat into them quickly.

[madjak]

hmm maybe I'm using the wrong term...

There was no tyre temp other than heat soak off the bitumen. It's always on the first and second corner into a hillclimb event were I found it hard. With the cold race pads, you obviously have to step on them to get them to stop, and when doing so they grab and lock the wheel very easily.

I have already noticed with the larger disks, they don't grab when cold like the smaller stock rotors. I figure it's because the pads have a larger area and larger leverage over the wheel.

But anyways, back to the main post. I think the NA6 rotors and calipers are fine. I'd run a proportioning valve and similar pads front and rear to try and get as much rear brake as possible. I don't think the bigger brakes are really required until you start pushing lots of power or get sick of replacing front pads and rotors.

I think (and Magpie's results seem to suggest) the stock proportioning valve reduces the rear brakes down to 60%. It's not a balance bar so it can only reduce the rears. When installing a Wilwood proportioning valve or no valve it brings the rear up to 100%.

[PeterB]

[quote="Dweezle"]
They work fine but I would love to be able to brake later.
I know where I have to brake with my current setup and if bigger allows me to brake a further 10m or more later I would be interested.
I guess my question is does the weight of the 8B brakes diminish any gains in braking performance to actually reduce lap times ??
I have a 1.6 making 80-85rwkw and am doing 1.13.5 at Wakefield Park on Ad08.
Could I see an improvement with the bigger but heavier brakes ?

I initially ran Britney (NA6 with 70-75 rwk with coil-overs and sway bars) on Toyo R888s using NA6 slotted rotors with Hawk HP+ front and stock pads at rear for a best at WP of 1.13.5. I was happy with the brake balance and stopping power, but cracked several rotors and glazed some pads due to overheating (no ducting). She was always inclined to lock a front, rather than a rear.

Braided brake lines gave a better pedal feel.

I upgraded to NB8A rotors, smooth up front with Carbotech XP10 pads and stock pads at rear. Balance was still good with an inclination to nip the unloaded front wheel. Heat management was much better with no glazing or cracking, but I cannot say I noticed any great benefit in stopping distances with the bigger brakes, nor any deficit due to the extra weight at supersprints or hillclimb.

It was worth it to deal with the heat issues. Probably the best way to pick up 10m under braking is tyres, as this will ultimately be the limiting factor.