"The Mazda" zoomzoom's NA Track toy

[MattR]

MattR why the question on the age, are older rotors better? And how the .... do you steer a Z around Lakeside in 57 seconds, not sure if I should call BS on that!!

Tim are they DBA rotors?

Timk, I was seeing the same speeds at Lakeside as Tim (zoomzoom) down the straights, a calculated off the revs done and tyre size plus gearing, 210-220kph through the kink and 190 odd kph under the bridge, just not the corner speed, so only down to 61's, my best lap a 61.3, on a good day and 62's pretty easy on second hand tyres, down to the canvas at times, any time I took it out. It did have just shy of 200rwhp and weighed 960kg plus me so that helped a bit. Brand new tyres would have seen sub 60s laps easy, but didn't have the wallet to do that at the time at $450 a tyre.

The question regarding the rotors age was more to do with how long they had been on the car as they would have seen a lot of heat cycles and the cracking and discolouration is a sign they have probably given their best in stopping.

Standard OEM type rotors these days are comparatively soft compared to the rotors of old and as I stated in my previous post can be regarded as consumables along with the pads. With the advances in pads in the last few years, Tim can concentrate on getting the pad/rotor combination right and not really need to worry about going bigger in the brakes which has the general disadvantage of extra unsprung weight.

If anything, Tim may benefit from looking at S14 brakes, 4 spot fronts and 2 spot rears with a 280mm diameter rotor up front and 258mm diameter rotor at the rear, if he wants to upgrade, though there maybe something similar in the Mazda stable that could be an easier fit.

[Magpie]

From memory Tim is running the OEM NB8B brakes (270mm front and 275mm rear).

[zoomzoom]

Hi guys, thanks for the input, hopefully I can answer some of the queries posted.

The brakes are NB8B with DBA slotted rotors. The microcracks do not concern me from a safety point of view its more just an indication of heat build up. These cracks are only in the very surface of the material, if they start to get deeper or towards the edges of the rotor that is a concern, it just means they should be inspected regularly. It is true that "seasoned" rotors are better from the point of view of metallurgy of the iron and these rotors are well seasoned.

They are also worn to around 20.8mm which means they have lost a few hundred grams of material to store the energy produced when braking, or around 5% of their overall mass and more when you just look at the mass of the ring, the area which will primarily store the energy during a stop.

As with everything on a car the braking system is a compromise. The disc and the pads are both consumable items and striking the right balance can be hard to strike between wear rate of the rotor and pad, heat resistance of the system and obviously mass, which in the case of the wheel braking system is unsprung.

I am already planning to upgrade the brakes but I am just seeing what I can get away with on the stock NB8B brakes until then.

I still have to decide which way to go with the fronts, since I am only doing sprint racing of 5 laps I am leaning toward a 26mm thick rotor at about 6kg which is only little over 10% gain in mass or I can also get a 30mm rotor at about 7kg and nearly a 30% in overall mass. Being that with decent pads the brakes seem to just cope with the 22mm 5.4kg rotors I am thinking of going the lighter way but I am yet to make that decision.

For the rears I am going to use the rotors I currently have on the front once they are worn down to 20mm. This should mean I will have ample capacity on the rear to use just about any brake pad I like .

Cheers,

Tim

[zoomzoom]

I finally got around to going through some of the footage the other night from Japnats at QR on the 24th. It looks like the camera went flat before I got my quickest time as is usually the case!

I grabbed a lap from earlier in the day which was about 0.2s slower and put it up of Youtube instead. This was from earlier in the day when the car was looser, particularly in the longer corners, but it was actually faster in the tight stuff according to my Racechrono and Qstarz GPS. As you can see I came up on a bit of traffic in turn 2 which I'm sure wouldn't have helped my time either. I had a few people egging me on from behind the pit wall as I came through turn 6 onto the straight with a little attitude to start the lap



Cheers,

Tim

[Lokiel]

That's some of the best audio I've heard from a driver's own MX5 video clip, your car is just roaring "GTF outta my way!" - car sounded great, will watch again!

[zoomzoom]

One of these days I will need to get hold of a decent camera and I might even look at mounting a mic somewhere that you can get some decent noise without the wind. This thing has been doing OK for a $70 special though

[zoomzoom]

I haven't had time to go through the footage from Lakeside yet, I might try to get to that in the next few days if anyone is interested.

Other than that I've had a little upgrade planned for a little while which I got a bit done on tonight, hopefully I can expedite this in the next few weeks. I will put up more details when the time comes...


Cheers,

Tim

[zoomzoom]

Just a little update for the time being after making a little progress over the weekend. Since I seem to be at, or even slightly beyond the limits of the NB8B brakes I have been doing a little work on some brake improvements.

I have made some changes to the rear brakes, in order to enable the rotors to shed heat more efficiently I have chosen to move to ventilated rotors. I took the 270mm ventilated rotors from the front and installed them on the rear with RX7 brake calipers.



And for the front I have fitted some modified Nissan calipers on some 288x26mm ventilated rotors. The 26mm rotors offer a huge improvement over OEM with a minimal weight penalty and the Nissan calipers have great availability of brake pads with the only real drawback being the thickness of the caliper affecting wheel clearance.



Cheers,

Tim

[MattR]

Tim, which Nissan calipers, S14, S15, Z32 or R32/3. If you need to take a bit off the face to get a mm or two a grinder will sort that safely.

I assume they are alloy calipers and not the cast iron ones. The only problem you may have, but I doubt it very much, is that the alloy calipers can flex when used at their limit. Generally only happens on the barge arse R chassis or Z chassis nissans.

[Apu]

Where did you get the adaptors for the calipers?

[Magpie]

What pads are you using?

[sailaholic]

i would guess the adapters were custom made by tim..like pretty much anything non stock on that car

[timk]

Looks good Tim, I like the safety wiring too.

Do the RX-7 rear calipers retain the handbrake?

EDIT: Oops I should have looked at the pictures more closely!

[zoomzoom]

Hi guys,

These calipers are from an R32 GTST. The Nissan calipers are all virtually the same with the major differences being that some were cast iron and some were alloy depending on what they came off, whether they were JDM vs. ADM and the length of the mounting ears also differs slightly from one model to another. There is also the difference of most of them being to suit a 30mm disc and some being to suit a 32mm disc.

These calipers being from a R32 GTST are of the alloy variety and are made to suit a 30mm disc. These were chosen due to the length of the mounts being most suitable for how I wanted to mount them. While I had them apart to rebuild them I had them modified a little so they now suit the 26mm disc. The Nissan calipers are quite thick through the piston housing so despite being alloy they are known to be quite stiff, I would hazard a guess that they would be considerably stiffer than most of the cheaper wilwoods which people are using and have a much better availability of brake pads due to them being so common in the performance car world on nissans.

The brackets are all custom made. The rears retain the OEM handbrake cables which I have not had a chance to try out yet as I have not bled the brakes.

I am going to use Winmax W5 in the front since I was really impressed with how they coped in the Mazda calipers and for the rear I will be using QFM A1RM as they should be operating dramatically cooler now due to the ventilated rotors.

Hopefully I will have the rest of the system sorted and might even get it out for Timeattack in a couple of weeks to start setting up and testing but I'll see how I go. I am yet to replace the master cylinder and bleed the system before I can try the first application.

Cheers,

Tim

[Apu]

Thanks for that Tim! Where did you get the adaptors made?

Reason I ask is that the Works Engineering calipers are based on the R32 Sumitomo made caliper. They are alloy monobloc.

I use them on my Integra but want the same on the MX5 but don't have the adaptor.