Brake Options - Standard Aurion

[Steven]

Just make sure there is enough clearance (depth wise) between the fully open caliper when mounted and your wheels.

Also, non-OEM brake booster/brake master cylinder will undergo some scrutiny.

Being a 1 piece 4 pot caliper it doesn't have a sliding assembly so fully open is the same width as the pistons fully extended.

Mostly my interest in the master cylinder is that the Aurion one is sufficient for these brakes. Seeing how the R32 only needs a 1" master cylinder, it's not too large and considering the TRDs come with a twin-pot set up using the same MC (I assume) then I imagine it must be big enough for these brakes.

[Steven]

got some good news.

The IS350 uses the same rear brake caliper sizing as our Aurion. The assembly is slightly different, but for the most part it's the same sort of caliper. What's most important is that it's a single pot in which the piston size is the same as ours.

The IS350 and IS250 share the exact same brake master cylinder, however the IS250 has the same front brakes we do in the Aurion (single pot, same size piston).

I don't believe the Aurion shares the same master cylinder as the IS250/350, but it does look like it would bolt straight onto the Aurion if it were required.

From this, we can tell that the Aurion should be capable of running 4 pot front calipers without ruining front/rear bias. Further it would also imply the MC was up to the task of pushing the front brake pistons the correct amount.

The IS350's front brakes are actually bigger than the R32 calipers I'm thinking of using, so that works out well too.

Shame the Lexus brakes are rarer than hens teeth. They have a weird looking mounting bracket on the calipers (staggered) but I have a feeling they might still have fit as a direct bolt on.

[Steven]

anyone know if brake pad spacers are illegal and/or dangerous? Basically I want to fit an r32 caliper to the back brakes, but they need an 18mm vented rotor where ours are 10mm - alternate rotors that suit our handbrake aren't available.

I initially wouldn't have thought so, but I see so many people using them and even online shops selling them that I had to ask

[Foss]

By spacers I'm picturing a plate inserted between your caliper and your pad? I can't see how they'd be dangerous, as it'd just be like having a bigger backing on the pad. Legality could be iffy - some things are just illegal for the sake of being illegal, whether they're a safety hazard or not.

[trentmeyer23]

I dont know if there is any legal writing, however I can research it, but I would STRONGLY advise against it.

[Steven]

Still can't get a sure answer on the pad spacers, but I'll come back to that later.

Further fiddling with the calipers shows they WILL hit the inside of the sportivo rim using the rotor I had planned (some humble pie to be had here), however I have an alternate idea and need some opinion as to whether it will work.

Current OEM rotor is 49.3mm high from back of disc face to top of wheel hub. I have found a rotor (actually a 30mm thick rotor) that is 56.7mm high. I'm assuming this would mean the disc would sit further inside the wheel well and would give me my required clearance. Unfortunately the disc isn't a direct bolt on, the centre is 58mm (OEM is 62mm) and the PCD is 100x5 instead of 114.3x5 however I believe these are easily rectified with a few minutes on a mill.

Am I on the right track here? Obviously hub spacers are out of the question and different wheels are as well at this time.

[trentmeyer23]

Just keep in mind which part of the car you are modifying, it's not somewhere that you want to cut any kind of corners.

[Andrew357]

Still can't get a sure answer on the pad spacers, but I'll come back to that later.

Further fiddling with the calipers shows they WILL hit the inside of the sportivo rim using the rotor I had planned (some humble pie to be had here), however I have an alternate idea and need some opinion as to whether it will work.

Current OEM rotor is 49.3mm high from back of disc face to top of wheel hub. I have found a rotor (actually a 30mm thick rotor) that is 56.7mm high. I'm assuming this would mean the disc would sit further inside the wheel well and would give me my required clearance. Unfortunately the disc isn't a direct bolt on, the centre is 58mm (OEM is 62mm) and the PCD is 100x5 instead of 114.3x5 however I believe these are easily rectified with a few minutes on a mill.

Am I on the right track here? Obviously hub spacers are out of the question and different wheels are as well at this time.

Drilling the hole out to 62mm shouldn't be an issue and it would be the same as the TRD mod of drilling down from 120x5 to 114.3x5 but in the other direction (ie drilling from 5x100 to 5x114.3)

The flare of the rims away from the centre of the rim may/may not give you enough clearance. For reference, The Viking tried a 4-pot setup (don't quote me, but I believe it was an R32 or similar) and he couldn't get them to fit in his Gen4 with 17" GTP rims.

More pics: http://www.carsales.com.au/all-cars/private/details.aspx?Cr=3&R=9647731&trecs=5&__Ns=pCar_RankSort_Int32|1||pCar_PriceSort_Decimal|1||pCar_Make_String|0||pCar_Model_String|0&__sid=12F60815F39B&__Nne=20&__Qpb=true&seot=1&__N=1247%201282%201252%201246%204294962861%204294961126%204294744753%201216&silo=1011

[Steven]

I only need another 5mm of clearance to fit, thats taking into account the wheel flare.

Out of interest, what are the dimensions of the rotor you intend to use?

[Andrew357]

I only need another 5mm of clearance to fit, thats taking into account the wheel flare.

Out of interest, what are the dimensions of the rotor you intend to use?

325x32mm. For what it is worth, the Viking has confirmed the TRD setup will fit on 17"

[Steven]

How high are they?

[Andrew357]

How high are they?

Damn mobile Internet, I can't check.

But it is listed on the DBA website. Look for he details of the Chevrolet c5 rotors

[Steven]

I tried but it only lists rear rotors? Im also on the mobile so will double check when i get home

[Steven]

Okay I think I've got the right rotor now. Corvette C5s, only 48mm high unfortunately so too shallow :(

They also have a centre bore of 71mm, how do you plan to work around this with the Camry needing a 62mm bore?

[DJKOR]

Didn't read the FAQ did you?

Also the rotor has a hub locator ring fitted to reduce the centre diameter from 71mm to 62mm.

Edit: LOL, I said the following on March 28 last year:

Well, it looks like this is something I am going to look into not far down the track.

And I still don't have new rotors yet.

[Steven]

Didn't read the FAQ did you?

Also the rotor has a hub locator ring fitted to reduce the centre diameter from 71mm to 62mm.

Edit: LOL, I said the following on March 28 last year:

Well, it looks like this is something I am going to look into not far down the track.

And I still don't have new rotors yet.

More humble pie.

Seriously this R32 set up is giving me head aches. Now I found I can't really get a much deeper rotor due to the dust shield design etc and it's mounting points. Then there are possible issues with this rotor (315mm) being too large a curve to sit properly in the caliper designed for a 280mm rotor and not getting proper pad contact!

In the best case I have figured there will be about 1mm clearance between the rotor and the dust shield, and about 2mm clearance between the caliper and the back of my wheels.

These are also some of the more compact 4-pots around. From this the landcruiser or hilux calipers haven't got a hope in hell of fitting.

I'm thinking this is a good time to sell off these calipers and cut my losses

[DJKOR]

Pioneering something always takes a fair bit of effort mate. You have come so far already. Are you absolutely sure there is no way to continue in an economical fashion?

[Steven]

Pioneering something always takes a fair bit of effort mate. You have come so far already. Are you absolutely sure there is no way to continue in an economical fashion?

A rough idea of overall cost came to around $700 to $800, which I was happy to spend if it resulted in a good quality 4 piston set of front brakes. At the same time though I have uncovered the following issues

- A rotor of at least 318mm diameter is required. The caliper is designed though for a 280mm caliper. Allowing for the free play in the caliper itself, I found a range of only 316mm to 324mm in which the rotor must be sized for the brake pads to come in full contact with the rotor. This limits my rotor selection somewhat

- The caliper extends outwards from the rotor much more so than the factory caliper to about 60mm from the rotor. This fouls on the factory sportivo 17" wheel. As wheel spacers are illegal/dangerous, and different wheels out of my budget, this means the rotor used must be a greater "height" to the factory one. The factory is roughly 49.3mm high, to obtain the needed clearance the rotor must be at least 55mm high. However as this means it would extend further into the wheel well, it would foul on the the hub assembly if it's anymore than 57mm high. This further limits my rotor selection.

- The rotor must be only 28 to 30mm thick. A 32mm could be used but there would be only 1mm between it and the inner parts of the caliper, which could create rubbing if any flex was present in the system.

From all this I found the only rotor that fit the criteria was the DBA2650, a somewhat rare rotor found on late model Subaru's. To fit the centre bore was need to be machined larger, and the PCB redrilled to match the 114.3 Toyota stud pattern.

Whilst this would create a functional system, the clearance in several places would be around the 1mm mark and at such close tolerances I believe it's just asking for trouble to happen. Last thing I want is my rim catching on my caliper during a hard corner.

In a way it looks like the brakes are designed with a similar mindset to the TRD supercharger - well packaged but damn hard to fiddle with.

[Andrew357]

The easiest way is upgrading your wheels to 18" which will give you the clearance you need but obviously this will come at extra cost.

As The Viking mentioned already, the easiest way is the TRD Aurion brake upgrade as he did alot of trial and error with his Gen4 when he had it as his main car.

Another option would be the Gen3 widebody brake upgrade with Supra rotors. 13" rotors, 2-pot cast iron calipers (from v6) and all you need to make up is a bracket for the calipers. Ask The Pharmacist about it as he is running that setup now.

[Steven]

Considered gen3 but theyre damn hard to find

[Steven]

Thanks to Andrew357 I was able to locate some Gen3 twin piston calipers, to use a set up similar to STYLSH.

First some interesting comparisons. The single piston caliper has a total piston area of 3017mm^2, where the twin piston actually falls lower at 2034mm^2, that's 32% smaller! However the pad sizes on the single piston are roughly 5850mm^2, where the twin pistons come out slightly more at 6240mm^2 (only about 6.25% bigger).

Currently I'm at a lost as to how this will affect real world performance, as the pads are larger but the pistons are considerably smaller.

Now granted the twin pistons are meant to be used with a 323mm rotor (8.4% larger than stock), or possibly another rotor I've found which is 334mm (11.4% larger), so that question remains will the twin piston actually be any benefit? granted the larger rotors (thicker too) which increase cooling and thus reduce brake fade.

The other option I'm thinking of is using the factory single piston with the larger 334mm rotor. It won't fit on the 323mm but at 334 it will just fit under the 17s".

Opinions people? I reckon these figures pose a few questions regarding the gen3 twin piston upgrade.

[Steven]

Just adding to the above, I may have miscalculated the actual usefulness of the pistons. Considering that the pistons are really just the metal on their circumference (think of a hollow 0 rather than a flat, solid 0) then perhaps it may be more relevant to compare the total circumference's of the pistons of the calipers. Rough figures below

Single piston - 191.54mm

Twin piston - 226.08mm (15.3% larger)

So which is better? Total area inside piston, or actual metal making contact with the pad?

[Steven]

Pics

[450HP/tonne]

If you increase the total piston area, you decrease the force applied to the pad. This is inversely proportional, so doubling the area will half the force. You have to be very careful to not change the front / rear brake balance to the point where braking could become unstable (front end, or worse rear end, brake locking and resulting loss of control).

Pad surface area doesn't directly influence ultimate braking capacity (but it will affect cooling), but the pad coefficient of friction will. 20% higher pad coefficient will result in a 20% higher braking torque, but that may mean reduced service life.

The radius of the brake pad centroid on the rotor also has a significant change when you play with things, if you double the radius, you double the braking torque (ie proportional).

Summary: If you're going to change one end (front / rear), you have to do all of the above in the same proportions at the opposite end to ensure you don't wreck! PLEASE speak with a certified road authority ENGINEER in your state (VASS in VIC) before you drive on the road.

[STYLSH]

Ahh yes, forgot about the other advantage of having bigger rotors is that the braking torque is increase. Having gone from 275mm rotors to 323mm rotors, I certainly felt the difference in actual stopping ability.