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LS400 front caliper conversion


bigbloodyturbo

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And a LS400 is just as fast as a Supra... its the speed the vehicle is breaking from that heats the discs not the acceleration that got it there.. both are limited to 155mph. of course, I'm only generalising. racing on a track would be different.

 

I dont think you understand what I'm getting at. LS400's are nowhere near as fast as TT's, they dont accelrate as fast, they would struggle to keep as much speed between corners and braking points. The brakes required to adequately stop a supra will be a lot different to ones required to stop a car that has the design brief of a TT supra. Therefore saying that because an LS400 can do 150mph just as a TT can therefore the brakes should be able to handle the same abuse is a rather simplified view of the requirement of your brakes.

 

So in answer to your rebuttle, no, it is not the speed your braking from that matters, its the frequency with which you do it and the cars ability to be faster between breaking points requiring more heat rejection from your braking system. If all everyone wanted was to stop really quick from 150 then jspecs would be just fine, i personally would rather stop from 120 five times in a row though.

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Guest Skullface
it is not the speed your braking from that matters, its the frequency with which you do it and the cars ability to be faster between breaking points

 

I might have come across wrong, but I completely agree with you, hence my parting comment regarding track use where the regular need to break hard and fast is most relevant. I was being specific about the caliper, not the disc/pad/caliper combo.

 

However, caliper is less relevant to thermal fade than disc and pad choice and the TT disc is slightly larger. The caliper does directly affect break force, and for that, it is fair to compare simply terminal velocity and vehicle weight.

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Everything else being equal (pad material, disc material, master cylinder, driver, tyres) the variables are the caliper piston area (one side of the caliper only), and the effective diameter of the disc (without a load of maths, call it the middle of the pad), so 4-opposed piston calipers are not necessarily any more powerful than 2-piston sliding calipers.

 

They won't really put anymore force onto the pads regardless of how many pistons you have. The difference the piston surface area makes is to spread the load across the pad. By your logic the pistons could be 10mm and as long as the force on the pad was the same it would give the same braking force, this wouldn't be the case though as it would be focused on the one spot.

 

Similarly with 4pot and 2pot, with the 4pots having 2 pistons on each side, the accumulated surface area spreads a lot more evenly with the 4pots thus giving better braking and cooling etc.

 

The more load spread across the more surface area the better.

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Everything else being equal (pad material, disc material, master cylinder, driver, tyres) the variables are the caliper piston area (one side of the caliper only), and the effective diameter of the disc (without a load of maths, call it the middle of the pad), so 4-opposed piston calipers are not necessarily any more powerful than 2-piston sliding calipers...

 

 

They won't really put any more force onto the pads regardless of how many pistons you have.
That's what I said. It's not the number of pistons, it's the total piston area on one side.

 

 

 

The difference the piston surface area makes is to spread the load across the pad. By your logic the pistons could be 10mm and as long as the force on the pad was the same it would give the same braking force, this wouldn't be the case though as it would be focused on the one spot.
That's not what I said.

I said "the variables are the caliper piston area (one side of the caliper only), and the effective diameter of the disc". In other words, more slave piston area = more braking force (and the master piston travels further), and bigger disc = more leverage = more braking force.

 

 

 

Similarly with 4pot and 2pot, with the 4pots having 2 pistons on each side, the accumulated surface area spreads a lot more evenly with the 4pots thus giving better braking and cooling etc. The more load spread across the more surface area the better.
Cooling wasn't mentioned.

A sliding caliper with two pistons (when it's working perfectly) distributes the braking force as evenly as an opposed piston caliper with four pistons. It's Newton's Third Law.

 

 

:)

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That's what I said. It's not the number of pistons, it's the total piston area on one side.

 

 

 

That's not what I said.

I said "the variables are the caliper piston area (one side of the caliper only), and the effective diameter of the disc". In other words, more slave piston area = more braking force (and the master piston travels further), and bigger disc = more leverage = more braking force.

 

 

 

Cooling wasn't mentioned.

A sliding caliper with two pistons (when it's working perfectly) distributes the braking force as evenly as an opposed piston caliper with four pistons. It's Newton's Third Law.

 

 

:)

 

 

I'm confused then, why did you conclude that 2 pot jspecs would be better than 4 pot UKs if the discs were the same size if you agree with what I'm saying?

 

Ahh wait, I think I'm following you now.

 

What you are forgetting is the friction and losses across the slider. The braking force will also never be even.

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...What you are forgetting is the friction and losses across the slider...

 

 

That's why I said "when it's working perfectly".

 

My Soarer is about to get a UK upgrade. It's not because I need the braking performance (far from it). It's because they look better, and because, after 130,000 miles in my daily driver GS300, I really, really hate the bloody sliders. :)

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The LS400 rear calipers are slightly larger but fit the same bracket as the j-spec rears. They even take the same pads.

 

I've been using the LS400 calipers on the rear of my Supra for years now with no ill effect. They were also easier (and cheaper, but that wasn't a factor) to get hold of second hand and in good working order.

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The internet (always trustworthy :)) says that the LS400 calipers have smaller pistons than the Supra calipers, which would make them less powerful.

 

If that's the case, a GS300 or a Soarer TT would be a better choice for replacements, I think they are the same as the Supra.

 

 

EDIT: Checked the EPC. The rear caliper piston is the same part number for the Supra, Soarer, Aristo, and GS300, but different for the LS400.

 

LS400 UCF20

Rear caliper piston 47731‑30120

 

Supra JZA80

Rear caliper piston 47731‑50040

 

Soarer JZZ30

Rear caliper piston 47731‑50040

 

GS300 JZS147

Rear caliper piston 47731‑50040

 

Aristo JZS147

Rear caliper piston 47731‑50040

Edited by garethr (see edit history)
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  • 2 weeks later...
Guest Skullface

could that be related to the piston material? If LS calipers are Alloy and the others are steel, it would make sense that the piston material could well be different.

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  • 11 months later...
Guest MrMagou

Hi..i`am new here. and sorry for my english.I have a question. what is the experience? the ls400 caliper is better than big brake from supra? EU/UK Spec? or the same?

thank you

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Guest MrMagou
The discs are slightly smaller, the swept area will be smaller, therefor less efficient. The only gain is saving a bit of weight.

 

thanks...but no weight is better brake?

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