*** Long post - but hopefully an interesting read ***

After 6 months of investigation, negotiation, technical research, prototyping, production and final testing, I’ve now succeeded in establishing a 2-piece lightweight brake disc solution for all 4 Pot/V6 owners with 325mm rear, 380mm front brake discs (the ‘High Performance Brake’ option).

Up until now the only 2-piece upgrade option for this OEM setup was to ‘upgrade’ the rear disc to 376mm and fit the VAP/Girodisc solution. However, this entails fitting new calipers (£££), brackets (£290) and splash shields (£68), before you can fit the VAP discs (See --> Upgrading rear brakes). Adding these preparatory costs to the UK price of £2,760 for the VAP discs, makes for a very expensive £/kg weight saving. The annoying part is that the OEM rear discs weigh in at 7kg, where the VAP 2-piece rears come in at 7.44kg (16.4lbs), so you are actually paying to ADD weight. Although not a mechanical consideration, I don’t particularly like the appearance of the VAP discs, so the aesthetics were another negative factor. For me, the frustration was further compounded by the fact my calipers are custom painted, so I would also have to repaint the replacement rear calipers to match the fronts.

Determined to find a more practical solution, I approached some well know aftermarket brake disc manufacturers to establish what alternatives were available – the short answer was ‘none’! There are some 2-piece alternative solutions for the 380mm front discs, but nothing available for the 325mm rears.

Undeterred, I then asked what could be done in terms of creating a 2-piece bespoke option, specifically for the 325mm rear discs. There was little interest in pursuing this solution as the potential weight savings on the relatively small rear disc would be difficult to justify in terms of manufacturing investment and subsequent retail pricing. I expected my final approach to a company called Tarox, to yield a similar response, but Tarox have a unique manufacturing approach and this opened a door of opportunity. Tarox do not ‘cast’ discs and machine them in the conventional way.

Quote “Using only the finest materials, each TAROX Bespoke disc is machined from a solid billet of high-quality European steel, which is then heat treated for extra strength. Our steel has an ultimate tensile strength (UTS) of 57kg/mm2. Using CNC technology, each slice of billet is machined into the exact dimensions required to ensure a perfect fit for each application. Vented discs are manufactured with curved internal ventilation, utilising 20 directional ‘venturi’ vanes which accelerate hot gasses and aid heat dissipation. Composite brake discs that require a two piece configuration receive a hub section machined from 7075 billet aluminium which we hard anodise for protection from the elements”.

In short, Tarox can produce single bespoke disc pairs, without having to invest in new casting moulds, so it was indeed possible to produce a 325mm 2-piece disc. This was a step forward and boosted by the fact Tarox already make a 380mm 2-piece disc for the F-Type. While Tarox produce a single piece 325mm rear disc, the fitting hardware for a 2-piece disc means the dimensions are completely different and there was no guarantee a 2-piece disc would not foul the rear caliper. After an exchange of technical drawings, I spent a day mocking up a template for a 325mm 2-piece rear disc, taking measurements and photos, which were subsequently passed on to Tarox Engineering Team. After a few days, they confirmed a 325mm 2-piece disc could be produced, which should fit the available space envelope. This still left the unknow element of weight, as Tarox could not provide definitive measures until an actual disc had been produced. They did however state that significant weight savings similar to the 2-piece front disc were unlikely, due to the lesser volume of material in the rear disc ‘bell’.

Time to take a leap of faith and put my engineering efforts to the test – I duly ordered the first ever set of 325mm 2-piece discs with an estimated cost of £1,000. Cue five weeks of anxious waiting for two slices of shiny steel to arrive. A week later, I took another leap of faith, convinced that the Tarox 2-piece 325mm rear discs would fit, so pressed the button on the matching 380mm fronts, I’ve always been an optimist ).

The day finally arrived when the man in red (Parcelforce not Santa) knocked on my door and dropped off the large box covered in tantalising pictures. Somewhat excitedly I opened the box and took in the gleaming appearance of the contents before hurriedly placing them on the digital scales – more later. Knowing the Tarox 2-piece discs came with stainless steel hardware, I also purchased replacement titanium hardware (M6 bolts and nuts) to squeeze every last gram out of the potential weight savings. A full set of Brembo road pads were also lined up to complete the new brake package.

After a few days waiting for a suitable weather window, it was time for the final test, would the new discs fit and align with the OEM calipers. Time for some pictures:



Flushed with success with the ease of rear upgrade, the Tarox 2-piece fronts arrived two days later, so time to complete the project:




I haven’t detailed the disc/pad R&R procedure, as this is widely documented and several Youtube videos are available. So down to the crunch, what were the weight savings and how much does a complete disc (rotor) package cost? To make it easier, here’s a summary (figures per disc unless otherwise stated):






So was it worth the time and effort and did the exercise deliver in terms of a simplified disc (rotor) upgrade path, while providing cost effective weight savings (and some eye candy) – absolutely!

In addition to the raw figures outlined above, I can vouch for the engineering quality of the Tarox discs (30 years’ time served mechanical engineer myself). They simply cannot be compared with standard cast discs in terms of engineering refinement. In addition to the cost savings versus the VAP 2-piece option, the following points should also be noted:

1. Make sure you order the discs with “Anti-rust treatment”. This entails treating all non-swept areas of the disc with a special coating, which will enhance the appearance of the discs, while preventing corrosion and extending the life of the disc.
2. Tarox do not stock ‘bespoke’ discs, so each disc set is made to order. Standard manufacturing and delivery is quoted as 2 – 3 weeks. The 325mm rears purchased direct from Tarox took 5 weeks (admittedly first ever production run). The 380mm fronts purchased from ML Performance took 6 weeks!! So be prepared to wait (good things will come ).
3. The Tarox discs can be ordered in 5 different styles, depending on your personal preference. I went for old school plain slotted (C83), but more modern styles are also available. As I always do, I would caution against fitting drilled discs to a high-performance vehicle. Available styles are:
   
4. Take note that due to the venturi vane design, the Tarox discs are ‘directional’ and must be fitted to the appropriate side of the vehicle to ensure the correct direction of rotation and function of the disc.
5. For those of you nervous of introducing Titanium fasteners into the brake components, I should put your mind at ease. The Tarox discs use stainless steel ‘bobbins’ to transfer the rotational forces between the steel outer rotor and aluminium centre bell, similar to a motorcycle brake disc. The mounting hardware is simply there to keep the bobbins in place and is not subject to braking forces in any way. You can of course use the Tarox discs ‘out of the box’, while still enjoying cost effective weight savings. Should you decide to pursue another 200g weight saving and replace the mounting hardware with titanium, the torque value for the retaining nuts is 14Nm.
6. Don’t forget you need to put the EPB in ‘service mode’ to remove the rear calipers. See -->
   EPB Service Mode

I have no affiliation with Tarox, but have nothing but praise for them in regard to their professional and practical approach to tackling this engineering challenge over the past 6 months. Paradoxically Tarox do not currently provide a 376mm 2-piece rear disc, so don’t cater for V8 owners with the ‘Super Performance Brakes’. However, I have absolutely no doubt that should someone approach them (Adam Rogers – websales@tarox.com), to enquire about production of a 376mm 2-piece rear disc, they would be provided with the necessary support to achieve such an outcome (or a 355mm 2-piece front disc for that matter). I can assist with technical measurements if required and provide copy of engineering template via DM.

Part numbers and supplier sources:



Web links:
--> Tarox 325mm
--> ML Perf 380mm
--> Tarox 380mm
--> Brembo P 36 032
--> Brembo P 36 029
--> RaceTi M6 x 30mm
--> RaceTi M6 nut
--> Cardecals64
--> Wheel guide pins

I hope this post proves of interest to you P300, P340, P380, P400 (or equivalent High Performance Brake set up) owners out there and provides some encouragement to take on what up until now had been an almost inaccessible upgrade. Do let me know via this thread, if you decide to follow my example and of course I’m happy to help with any queries, questions you may have.

 

Just one correction to your terminology:
In JLR F-Type speak the "performance" brakes are the base model brakes, 355 mm front (not 380 mm) and 325 (AKA 326) mm rear, the combo of 380 mm front and 325 mm rear is called "high performance" (standard on the F-Type S V6) and the 380 mm front 376 mm rear combo is called "super performance".
Otherwise owners of base model F-Types with 355 mm front brakes (i.e. "performance" brakes) could be mislead into thinking this kit will fit their car when it won't work for their front brakes.

 

Thanks for sharing!

Having more options is always welcome and being able to spec the size yourself opens up other opportunities.

 

@OzXFR Thanks for the clarification re JLR marketing terminology. I've updated the OP to reflect the correct 'High Performance Brakes' description for the 380mm/325mm set up. Doesn't update original title unfortunately

 

And that's not counting the money and effort spent on gathering, preparing, and installing the calipers, brackets, etc for the 376mm rotors. With that considered, the VAP set comes out to substantially more than what's written above.


Edit: pardon me, I see that you did indeed mention that already!

 

To me, the weight savings doesn't make sense for the rears on 2 piece given the stock 326mm rear rotors are "relatively" light and deal with the parking brake...something to note....

So, for me, the plan is to get the VAP fronts. 1200 British pounds minus the VAT (as I am in the US) but plus the shipping is likely no better and possibly worse than the VAP 1200 dollars. I have also had Girodiscs on other cars and they are superb. So to me, in this exact mode, I think the VAP if you live in North America are not more expensive, may be as light or lighter, and are top tier quality (not saying the others are not...but they are all over the place at track events in the US).

VAP also has been amazingly good at support and service - so my dollars will go to VAP when I upgrade.

I appreciate the new option, but they'd have to be under 800 dollars per end (front/rear) TO MY DOOR for me to think about them seriously. What I like at GiroDiscs is you can just get the rotors parts later and remount them to your hats....

My problem is my car has 65k miles and gets driven as intended and the TRW stock brakes are all at 55-60% life left...they just don't wear out. The OEM brakes are just really good for street use. On the street, no fade, great feel, huge stopping power. And I have the 380/326 option...to me the sweet spot as 376 in the back just adds extra weight for looks.


My plan given my use case is to get the VAP's for the front and be happy. If VAP gets Girodisc to make a 326mm rear set, I'd be into that but it probably would save only a few pounds it seems. Fully admit it would be for matching/looks on my part. I am not immune to looks....these are beautiful cars and that makes me happy too.

 

Unfortunately, based on recent correspondence I've had with them, it doesn't sound like VAP plan on offering a matching 326mm set anytime soon (they'd rather that I and others spring the extra $ for used calipers etc and get their 376mm set - as OP noted, spending $ to *add* weight??).

I, like you, did consider getting the VAP fronts only, but I know full well that a non-matching set (VAP fronts/ OEM rears) would bug the heck out of me.

 

I am sort of at peace with VAP girodisc rotors in the front and oem in the back...in my case probably a third party one piece. It is sort of annoying as the "hat" for the 376mm rear is done and that is the "costly" part...the rotor at 326mm would likely be the only thing needed to do it....so VAP if you see this please consider a 326 option.. (if the hat is the same of course...)

My brake supplier for my prior car (KNS) sells a basic one piece vented non-directional (the supplier is likely the Australian company) rotor for his track rat buyers. He explained that if you do the math, if you are not racing, it is just cheaper to get the one pieces - economics....these were targeted to the Corvette and BMW and 911 crowd I think...disposable items...super reliable "no moving parts"....just KISS principle.... Modern brakes don't need features on the rotor...just plain good steel and done. I am a sucker for weight and the girodisc fronts save 10# each....so to me ok...but the rears at 1-1.5# max each...hard to justify the costs. On that end, I respect VAP for being principled....not enough weight saving....there are huge differences in tire weights too people forget.

For example, my DWS06Plus tires are abotu 5# lighter than equivalent Bridgestones or Michelins. That is a huge deal at it is out at the full radius.....and before people comment on sidewall stiffness, I have the "PLUS" model and it is quite stiff enough for anything I need.....that is something people forget.

 

Shameless plug here, if anyone needs the 376mm calipers with brackets, i have them (along with the 380 front) available, please pm if interested.

 

@jcb-memphis Totally agree the big weight gains are from the fronts, but unlike you I just couldn't settle for 2-Piece fronts and stock rears, hence why I pursued the 'bespoke' option. I'd already accepted that I wasn't going to save much with the 2-piece rears, but couldn't live with the visual differences between front and rear. Your point on the minimal weight savings for the rears is valid, but has just made me realise there is yet another option. Tarox already produce a traditional cast 1-piece 325mm rear disc (Part No 0427), so it would be entirely possible to have matching 'style' discs, enjoying the benefits of lighter fronts without the expenditure for 2-piece rears. Tarox 1-piece rears currently priced at £404 from ML Performance. Also, I get it if you are US/Canada based, as the VAP $US/$CDN pricing is way better than £GBP prices (VAP fronts at $1,200 = approx £960, add VAT to get £1,152, yet UK list = £1,440, shipping in the difference of course). Not sure what you are referring to when you say "1200 British pounds minus the VAT (as I am in the US) but plus the shipping is likely no better and possibly worse than the VAP 1200 dollars"? None of the brake components I referred to are priced at £1,200

Like you, I share the view that 376mm rears are more for cosmetic appearance rather than performance. My stock 380/326 setup has never felt 'lacking', but bloody hell, those stock front 380mm discs are ridiculously heavy , so they had to go and VAP/Girodisc option was simply not an option as outlined above. Not had a proper chance to enjoy a 'spirited' drive yet (yes I live in UK so it's raining - again ), so can't speak for difference to ride and handling.

Hopefully your stock fronts will wear out soon so you'll be able to justify a shiny new set of Girodiscs

 

You are correct on all counts. I was being too rough with the math....Great option if one is living in the UK to go with the one piece rears if the surfaces look is the same..that would be ideal....for me, here, will just do the VAP fronts and be happy. Probably need another 30k miles ...appreciate the well wishes in the last line....the stockers are just too darn well designed. I also drive in a manner that avoids brake abuse...mechanical sympathy if you will....all those track days and the costs trained me to be kind to rotors, tires, and the rear diff.....smooth is better....

 

@genp729 thank you for your time putting all these information in. I also found Tarox, when searching for the 2-piece rears. Please do you have any information about the "semi-floating" design Tarox claiming? Is it the same as VAP rotors offering? Is their solution good to go in winter on salted roads? Thank you

 

@J444G In order to explain the Tarox 2-piece disc "semi-floating design", it's probably easier to start with the Girodisc "fully-floating design" - bear with me. First let's take a look at the Girodisc steel rotor to aluminimum 'bell' or 'hat' mounting hardware:




The Girodisc design uses cadmium plated, steel alloy 'drive pins' to transfer the rotational forces between the steel rotor and centre bell. These drive pins are secured by steel cap screws, anti-rattle spring clips and hardened washers. This configuration allows for a small degree of lateral movement between the rear face of the centre bell and the front face of the steel rotor. This is termed "lateral float" and allows the steel rotor to expand at varying rates around the centre bell without causing distortion. More importantly if you are racing, it allows the steel rotor to 'self-centre' between the brake pads/caliper, compensating for alignment tolerances between the drive hub face and centre bell or brake caliper to hub mounting surfaces. This is what provides the instant 'bite' in a race set up, as the brake disc and brake pads will run perfectly parallel with full pad contact on initial brake application (I race motorbikes and have 'fully floating' Brembo discs for just this reason). In addition to the lateral float, the use of steel drive pins greatly reduces the size of contact surface between the steel rotor and centre bell, allowing the rotor to expand radially at differing rates to the centre bell. In a 1-piece disc, the outer rotor and centre bell are cast from the same material. The centre bell is not exposed to the kinetic to thermal energy transfer of the outer rotor (which can reach temperatures of 600 - 700C) and with the centre bell attached to the drive hub acting as a heat soak, you have the outer and inner areas of a 1-piece disc expanding at different rates, leading to disc 'warping', vibration and pad 'knock back'. So a disc designed to provide lateral float and minimise the effect of radial expansion via the use of drive pins is termed "fully-floating". As with most things mechanical there are advantages and disadvantages to this design.

The Tarox 2-piece design uses stainless steel drive pins similar to the Girodisc, however there is no 'lateral float' between the outer rotor and centre bell. The Tarox drive pins are not fitted with spring clips, the stainless steel securing bolts and nuts firmly clamp the outer rotor to the centre bell with no gap between them. The term "semi-floating" is used to describe the capability of the steel rotor to expand and contract radially independently of the centre bell by virtue of the drive pins as per the Girodisc design. In this respect all 2-Piece brake discs can be described as "semi-floating".



As to your final query regarding the ability of Tarox discs to cope with winter contitions and salted roads, this is where the advantages/disadvantages of 'fully-floating' versus 'semi-floating' come to the fore.

Fully-floating discs by design will be subject to constant movement of the drive pins within the outer rotor mounting lugs. Movement = friction = wear, an engineering fundamental. If you are racing and not taking your car out on winter roads, you can accept the increased wear as brake 'feel' and 'performance' are more important factors. If you introduce water, brake dust and salt, plus 1,000s of heat cycles into the finely machined bores of the outer rotor mounting lugs of a 'fully-floating' disc, they are going to deteriorate at a greatly increased rate. With regard to the Girodiscs, the drive pins are Cadmium plated. This is a 'sacrificial' anti-corrosion coating, which once erroded will further accelerate the corrosion of the underlying steel. (Note - due to environmental impact, under European statute cadmium plating is banned except for certain uses and worldwide, cadmium plating is being removed from almost all commercial uses). As the Tarox discs are 'semi-floating', there is no movement between the drive pins and outer rotor mounting lugs, therefore wear rates on the drive pins will be minimal. The outer rotor will wear out and be replaced independently of the centre bell, allowing you to extend the life of your discs. In addition, the Tarox drive pins are made from Stainless Steel, so are resistant to corrosion and the steel rotors are treated with a Cataphoric protective coating on all unswept areas to prevent oxidisation. So from a winter driving perspective I would suggest the Tarox 2-piece discs are more than capable of dealing with the harsh conditions.

Hope that was't too little or too much detail

 

@genp729 thank you very for the spon-on explanation.

 

This is really helpful information. Thank you.
jb