Less brake is more better?

Hi Dai fam, not really a question but I’d just like you thoughts and opinions on something.

As you may know, I installed M3/M4 brakes during my 3SZ swap. I like the look, they do their job well, but there’s one major issue: shit’s heavy. Just the discs alone way nearly twice(!) as much as stock L7 brakes (5,1kg vs 2,6kg) and since these calipers are one of the few models with a bigger piston, I’m guessing they weigh quite a bit more than stock. Now, both @Roffelkut and @Wolff hit the 'Ring with their L7’s which both have 234mm Sirion M1 brakes (3.4kg discs) and they both say it’s plenty for track. Yet here I am with my street car on 254mm brakes.

So: should I swap my M3/M4 brakes for M1/M2 brakes?

Why it’s a bad idea:

  • Effort/money
  • There’s a chance I won’t even notice an improvement
  • The bigger brakes fill up the hole that is the wheel nicely

Why it’s a good idea:

  • Weight. I’m team function > form and the idea of so much unnecessary weight is bugging me
  • Going back to a smaller caliper piston would reduce pedal travel, maybe improve pedal feel
  • Weight
  • Weight

I’d love to hear your thoughts and experiences!

Yea I did some laps on the ring, including back to back ones with OEM grade discs and pads together with RBF660 fluid and no ducting, but I want to remind you that I have maybe 50% of the original 54hp left over. @Roffelkut mentioned considerable amounts of brake fade on his second lap, which you might be able to resolve with ducting.

If your main reason is to make it more like a street car, because its too overkill, I’d just leave them on because on you’re not going to notice the weight difference… I mean, it sure does look way nice than 234’s…

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My opinion is I wouldn’t sacrifice brakes for the weight reduction.

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For sure there will become a point where the added weight does not provide any additional benefit. However that weight and amount of material is providing a heat sink for the brakes.

I noticed a huge improvement from 234 (M1 factory caliper + DSport TypeS rotor) to 246 (Copen factory caliper and factory disc). Other variables were kept similar (braided lines, Penrite RBF600). Admittedly I used different pads, but both track orientated. Project Mu with the 234mm setup and Dixel with the 246mm.

Mallala racetrack in South Australia has two heavy braking points in quick succession and we do 15-20 minute periods where you can keep pushing as much as you (and your car) can handle. Each lap takes ~1:30. The only way I would go back to the original setup is with added brake ducting, and the intent to only ever do 1 flying lap, and not continuous circulation trying to improve lap times.

For tracks that are more flowing, have greater ‘rest’ periods between braking events, yes the smaller brakes might be a better option to save weight. For an actual race car that requires to have zero-fade over a longer period, I would think the biggest/best brakes are more ideal in that scenario.

I guess for a street car, no they’re probably not needed, and extra weight means slower acceleration and worse fuel economy. But you have the big 3sz for power and surely none of us are in this game for fuel economy :slight_smile:

I vote for the looks on the street car, and any smaller disc/caliper combo would look pretty average.

**edit - just realised you’re on a lighter chassis than the Sirion. So perhaps the M1 or Copen would be sufficient.

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For anything but drag racing, go with the big brakes.

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Whats the more important thing? Accelerating faster or stopping faster? 2.5kg each side (also unsprung weight so double that) is allot but when you are driving faster you don’t want to have your brakes fade. Its the only thing keeping you from suddenly becoming stationary :wink:

For daily driving you probably could get away with smaller brakes. But i don’t think you swapped the engine just to drive slow.

Sprung weight can be reduced, through replacing discs and calipers with those produced with lighter materials:

…calipers for the automotive industry have traditionally been made from ductile iron, but more of the calipers are currently being converted to aluminum, with weight savings of nearly 40 percent…

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You know you’ve made it when you have carbon-ceramic brake discs on a street driven daihatsu.

Maybe closer to a possibility is;

  • Two piece discs
  • Rotors that are ‘sun cut’ or ‘scalloped’ rotors to reduce some weight.

Which still might be hard to find ‘off the shelf’ for Dai’s.

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Similar to how one of these becomes a status symbol? :smile:

Leather strap attached to the bonnet??
:joy: :joy: :joy: :joy:

Imitation leather, maybe?
Installing the following will add five more cylinders:

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I was going to write a long piece but I changed my mind.

Car makers fit the smallest brake they can get away without making the car dangerous - its how the manufacturers accountants win.
Bigger brakes weigh more but can provide better and longer braking when the situation is required.
If you’re building a performance vehicle for the purpose of going fast its a worthwhile sacrifice.
Despite me loving 10" wheels I will be upgrading my L55 to L700 struts, hubs and brakes for better braking, wheel bearing hub design.


[quote=“DaleJeffree, post:12, topic:6291”…Bigger brakes weigh more…[/quote]Weight-saving is a way to reach issuing lower fuel-consumption statistics, giving manufaturers the excuse for casting plastic headlamp units, instead of those cast from glass. Both those and smaller brakes can get annoying

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I would scale down on brakes if they are way to overkill. Its rotating, unsprung mass so there are serious gains to be made.

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