Dose's Sometimes DIY and Pay Someone Home & Boat Improvement Thread

[GTSBoy]

I thought the only (new) BM57 that was readily available was the one that was a BM57 but with the wrong bias. HFM or someone's?

[Kinkstaah]

They're available from Nissan! I was able to buy a GTR (R33) one.. relatively* recently. Perhaps this stopped now but I bought mine ... relatively recently.

I believe the 300ZX one has a different knee-point which is more rear biased, which I think the HFM one echos.

[Dose Pipe Sutututu]

So after some Chat GPT (yeah I know lol..) it turns out that the R35 GT-R BMC conversion may not be suitable for our shit boxes as it splits the fluid 60:40 instead of 70:30.

When looking at possibly doing the 370Z conversion, it seems it's quite similar to how the R35 GT-R booster & BMC mounts up, however after some additional digging the 370Z BMC bore is the same size as a R33/34 GT-R BM57 one.

Brake Pressure Split:

• Nissan 370Z: The typical front-to-rear brake pressure ratio for the 370Z is approximately 70:30. This is designed to handle the car’s weight distribution and performance characteristics, favoring the front brakes heavily due to weight transfer during braking.
• Nissan R33 GT-R: The front-to-rear brake pressure ratio for the R33 GT-R is also typically 70:30. However, this ratio is tuned for the GT-R's specific weight distribution and dynamic performance, considering its all-wheel-drive system and higher performance expectations.

Despite having the same nominal 70:30 ratio, the actual distribution of braking force in practice can be different due to other factors like vehicle weight, ABS and EBD systems, and brake component sizes.

Bore Sizes:

The bore size of a brake master cylinder affects the hydraulic pressure generated within the braking system and can vary between different vehicles based on their braking requirements.

• Nissan 370Z: The brake master cylinder typically has a 1-inch (25.4 mm) primary bore. The secondary bore can vary slightly depending on specific trim levels and brake options, such as the Nismo version or those equipped with the Sport Package which features larger brakes.
• Nissan R33 GT-R: The brake master cylinder in the R33 GT-R generally has a 1-inch (25.4 mm) primary bore as well. Given the GT-R's high-performance context and advanced braking system, the bore size is designed to provide sufficient hydraulic pressure for its braking needs.

Comparison:

• Brake Pressure Split: While both vehicles use a similar 70:30 ratio in the brake master cylinder design, the actual operational distribution might differ slightly due to differences in brake system components, vehicle dynamics, and tuning for each model.
• Bore Sizes: Both the 370Z and R33 GT-R use a master cylinder with a primary bore size of around 1 inch (25.4 mm). This similarity helps in providing robust hydraulic pressure for effective braking.

Additional Considerations:

• Braking System Design: The overall brake system, including calipers, rotors, and the master cylinder, is designed to work as an integrated unit. Even with similar bore sizes and pressure splits, the performance and feel of the brakes can differ due to variations in brake pad composition, rotor size, and ABS tuning.
• ABS and EBD: Both vehicles are equipped with Anti-lock Braking Systems (ABS) and Electronic Brake-force Distribution (EBD), which further modulate and optimize braking force between the front and rear wheels dynamically, depending on driving conditions and brake demand.

In essence, while the 370Z and R33 GT-R have some similarities in their brake master cylinder specifications, they are tuned to meet the specific performance and handling characteristics of each vehicle.

 

TL;DR, just use a R33 BM57 and call it a day.

[GTSBoy]

Typical LLM response. Nearly completely useless. Says nothing that wasn't already known, with no useful details.

[Kinkstaah]

FYI the BM57's in GTR do split 60/40 and they knee over from 50/50 at a certain pressure. (I found this after extremely painful googling awhile back)

The Z32 BM57 also splits 60/40, but the knee point where the 50/50 becomes 60/40 is at a higher pressure.
The S15 BM50 is the one that splits 70/30 I think?

They are also 17/16" size, and the plug fits, no downsides

[Dose Pipe Sutututu]

Yeah less mucking about grinding down the firewall, using brake line converters, etc.

Just send it with an original BM57 and call it a day.

[GTSBoy]

So the message is I probably want an S15 one.

[Kinkstaah]

3 minutes ago, GTSBoy said:

So the message is I probably want an S15 one.

I actually think the S15 is 80/20. I know I said 70/30 before but perhaps that is the GTT/GTST one. I wanna say it's the BM50 or BM44. I have one for sale if you want it GTSBoy, try your luck. For some reason the R34 GTT one is actually unlabelled, so it's a BM??????

[Dose Pipe Sutututu]

@Kinkstaah HFM will have a spicy BF sale in November, might be a good time to load up on the adaptors, new lines, etc.

Then may the best grinder win lol.

[Kinkstaah]

Oh I have mine all sitting in boxes ready to go, two sets of rotors, four sets of pads and caliper rebuild kits. They send a survey asking me if I had installed them months ago :p

Grinder not necessary to fit the fronts, and not *really* for the rears. They have some good simple videos on how-to.

I don't understand brake lines but from what I understand... somehow... OEM lines work, even though people say 350Z and 370Z use different banjo bolts, so it's possible 350'z had some different setup that Nissan changed to the 370Z/R33/R34 system?

....though are a little short, but past-me made a new bolt hole to bolt them to to reach my current fronts so I should be okay... maybe.

In any case HFM don't sell any *different* line kits for R33/R34 front brakes than they do for the 370Z kits. So in my mind they must be compatible or they would have different products made to suit the different calipers.

Please test and confirm for me kthx.

[Dose Pipe Sutututu]

44 minutes ago, Kinkstaah said:

In any case HFM don't sell any *different* line kits for R33/R34 front brakes than they do for the 370Z kits. So in my mind they must be compatible or they would have different products made to suit the different calipers.

It's more so I'm using the 1x piece line from HEL that goes from the body to the caliper. There's no middle block/mount like the HFM ones or the GKtech ones.

There are certain angles/suspension compression where the line actually slightly contacts the ARB.

Below of how mine sit (not my photo):

How I want it:

 

[Kinkstaah]

I hadn't got that far, my main worry was the connection to the actual calipers themselves. I'm just using new (ish) stock brake lines in the stock setup. I've just had a stud welded to the knuckle that is a little lower than the original stud (so my knuckles have two studs each side) to not have it be stretched so far in previous BBK setups, so the "block" (in the second picture) mounts a little lower for me and I hope I don't need to change anything.

I may have even changed the connection to the calipers in the past and have since forgotten I did that. I may not have. Guess how I'm gonna find out.

Source: hopium

[Dose Pipe Sutututu]

Pulled out this pile of shit, will be refreshed soon enough.

Had coolant hit my face and I accidentally tasted it. 

It's sweet.

[MBS206]

16 hours ago, Dose Pipe Sutututu said:

Pulled out this pile of shit, will be refreshed soon enough.

Had coolant hit my face and I accidentally tasted it. 

It's sweet.

Be happy it wasn't old auto gearbox fluid. That shit, is disgusting!

[Dose Pipe Sutututu]

DET shit on LHS, DE shit on RHS

Simples, especially not running a heat exchanger or the OEM bleeder.

[Dose Pipe Sutututu]

Cost of living crisis is real, bought Aeroflow fittings to run the water return from the turbo hardlines I made, back to the thermostat.

May regret buying Aeroflow, as the rest of the car is Speedflow 🥲

[Kinkstaah]

My Aeroflow stuff has held up just fine. Had to buy some stuff that wasn't in the Speedflow catalogue.

Proflow on the other hand...