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Discussion Starter · #1 · (Edited)
It seems that the XAT Racing front brakes are one of the ideal options utilizing factory, easy to find parts for the system base.

LS460 callipers with IS-F rotors (14”) will add and incredible amont of braking force while staying cool enough to not warp! The additional leverage of the calliper position due to rotor radius will really help!

Though for the rear, there doesn’t seem to be anything really available utilizing factory Lexus components, unless I’m missing a package that allows Lexus axial mount calipers like the ones on the rear of the LS460 (and our IS300).

In emails with XAT Racing, it appears that it’s on the do to list, but WAY down the list. There doesn’t seem to even be a potential timeline for this project of LS460 rear calipers on an IS300.

Are there any other options out there for rear brakes that will have a similar look and possibly larger diameter rotors?
 

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Discussion Starter · #3 ·
Unfortunately, this bracket kit is for a GS line not an IS.

I had asked about it directly to XAT Racing yesterday before the first post, and they had stated it won’t work without serious modification and the holes won’t align properly.

Has anyone on this forum bought this bracket kit and installed with relative ease in an IS?


 

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Unfortunately, this bracket kit is for a GS line not an IS.

I had asked about it directly to XAT Racing yesterday before the first post, and they had stated it won’t work without serious modification and the holes won’t align properly.

Has anyone on this forum bought this bracket kit and installed with relative ease in an IS?
It works on the IS also. If you search the forum. You will find where it has been done already.
 

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Discussion Starter · #5 ·
Unfortunately, @01 SolarYellow I've gone through 15 pages with 10 to go searching the term “GS430 rear brakes” which I have found 2 threads saying it’s possible with no one actually proving it and one thread has a member saying “pm me for details on brackets” (from 15 years a………

If there’s inside information where such brackets could be had, or what modifications are required for the LS460 calipers on a GS430 (because apparently there is a 25mm bolt spading issue, and those brackets don’t seem to accommodate a mod like that), could someone share?!?!?

Looking through the next 10 pages now, and then I guess I’ll search something else.
 

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Discussion Starter · #6 ·
Finished the 25 pages @01 SolarYellow - now searching “LS460 rear calipers” and going through these 25 pages………

If anyone has has actually done this, please chime in………. As searching doesn’t actually produce results in some cases.
 

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Personally, I wouldn't worry about rear brakes unless you're looking for appearance. The brake bias is very far forward in these cars so rear brakes don't do a ton. Getting larger rear brake rotors will probably decrease performance as your adding rotational mass and unsprung weight.
 

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Honestly a good pad, rotor and fluid should do wonders. Maybe even toss in some braided lines. My friend's old IS had all stock stuff but these super aggressive pads and his car stopped on a dime. Better than my LS400 brakes if I remember correct.
 

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Unfortunately, @01 SolarYellow I've gone through 15 pages with 10 to go searching the term “GS430 rear brakes” which I have found 2 threads saying it’s possible with no one actually proving it and one thread has a member saying “pm me for details on brackets” (from 15 years a………

If there’s inside information where such brackets could be had, or what modifications are required for the LS460 calipers on a GS430 (because apparently there is a 25mm bolt spading issue, and those brackets don’t seem to accommodate a mod like that), could someone share?!?!?

Looking through the next 10 pages now, and then I guess I’ll search something else.
If memory serves me. They only needed a little machining on the bracket. You could email XAT to ask. I think they helped the guy I remember doing it. Other than that. There where some aftermarket setup that did the rear and fronts also.
 

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Discussion Starter · #10 ·
@01 SolarYellow XAT was the one that emailed and told me it was heavy modifications required, the bolt holes will not line up and they will not return them if modified.

This is why I’m desperately looking for someone that has tried Lexus factory parts before for the rear brakes.
If memory serves me. They only needed a little machining on the bracket. You could email XAT to ask. I think they helped the guy I remember doing it. Other than that. There where some aftermarket setup that did the rear and fronts also.
 

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Discussion Starter · #11 ·
@_zaclemore & @Thatblueis - I’m fairly well versed in braking dynamics and systems, though warped rotors drive me crazy.

The first IS300 I ever drove (not mine, a friends) when they were new around 2005 had warped front rotors and severe pedal pulsation at any speed. When I picked up this 2002 IS300 two days ago - warped rotors. These are not as bad, they only seem to pulsate at higher speeds. It needs brakes, and I know that the weight of this car with IS-F fronts will never warp again.

For the rear, I was only hoping for something a little larger, vented and with a similar look calliper to the LS460 calipers that are be used with the XAT front kit.

There are relatively light wheels on the IS300 now, with some further weight reductions coming.

As a side note, my wife’s Stinger GT warps rotors like nobody’s business - it’s had them replaced under warranty once, machined a second time, and they are starting to again. It’s a HUGE problem and complaint to Kia all over, these Brembos were the wrong ones for this car!
 

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I think warping for these cars is mostly due to incorrectly bedding them in, though it's just my hunch.

Wheel Tire Automotive tire Tread Alloy wheel


This is how one of my new brembo front rotors looked after around 1000 or so miles. I never did a proper bed-in procedure and think I only drove carefully for 50 miles or so before I starting regularly braking. I tried doing several 60-20mph near stops in attempts to bed them in properly afterwards but it didn't help.

Grille Automotive lighting Automotive tire Hood Motor vehicle


This is how they look now. I got them turned at an O'Reillys and decided to just drive as conservatively as possible for as many miles as I could after getting them turned. I probably drove around 500 miles or so before any hard braking. I think this is the best strategy. A few thousand miles later and I'm satisfied. Can't really see the streaking unless you're this close. Barely any squeaking and no pulsation unlike before.

Too many people have warped rotors with these cars and that really shouldn't happen unless you're at the track.

I do recall reading of members on here swapping to bigger brakes and still getting warped rotors after installing.

Could potentially be worn caster arms, I've read about that too. After getting my rotors turned and installing my brakes the second time I had previously replaced those bushings with polyurethane. Might be a coincidence I'm not sure.
 

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My personal experience is if you warped factory rotors cutting rotors just removes material so it'll warp faster. I've found flushing with dot 4 fluid can help as the dot 4 and fresh fluid can help evacuate heat and prevent warping while braking. Warpage due to pad build up can be solved with slotted rotors which keep a clean pad surface. I wouldn't worry about rear they see such little pressure I actually have trouble getting it to hold for launching. When you install new brakes make sure the hub is clean otherwise the rotor won't sit flat and warp. Another issue with warpage is driving style. If you get your brakes very hot then hold your brake like at an intersection the rotor that the pad touches will cool faster causing warpage. I have slotted vented rotors ebc yellow pads dot 4 and ss lines and my brakes are limited by my tires which will become the weak point especially on big brake kits. I'd keep factory rear brakes. Start with just the fronts and see how you like it. Be aware the more aggressive the pad the harder it is to modulate at low braking pressure.
 

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Discussion Starter · #14 ·
Funny you guys mention this - I bought a brand new Magnum SRT8 in 2006, and the rotors were recalled for warping! It didn’t happen until about 3 or 4,000 miles - but Brembo issued slotted rotors front and rear to combat the issue. Seem to work.

I knew it wasn’t due to erratic driving, because my father bought the identical twin car that had the same issue.

I think there are always multiple factors that can have and effect on the rotor stability, but larger diameters can’t hurt (just additional centrifugal and unsprung weight).
 

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Now that you mention it, I think my stock ones were warped too. I never really noticed but I do remember my friend saying something.
 

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Discussion Starter · #16 · (Edited)
XAT Racing kit ordered........... Still not a fan of the rear brakes being solid rotors. It's too bad XAT or Figs hasn't developed a LS460 rear rotor/caliper situation yet.

Anyone know what the part number is for StopTech rear braided lines?

(I Show this i the catalogue 950.44500 - but was told by a 3rd party they are too short!?!?!)
 

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XAT Racing kit ordered........... Still not a fan of the rear brakes being solid rotors. It's too bad XAT or Figs hasn't developed a LS460 rear rotor/caliper situation yet.

Anyone know what the part number is for StopTech rear braided lines?

(I Show this i the catalogue 950.44500 - but was told by a 3rd party they are too short!?!?!)
98 TT Supra rotors are vented.
 

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Discussion Starter · #18 · (Edited)
Yes @01 SolarYellow - though it appears that there isn't a direct bolt on caliper for the application on an IS300 that I can find anywhere - the LS430 should work with a bracket - but I can also not find anyone whom makes a bracket for the IS300 Rear / Supra Rotor / LS430 caliper combination

In follow up, there was a member on here @hk300 that apparently had a connection or details on the kit, but wouldn't openly share it in the forum, and wanted people to PM for the information. Was probably misinformation, as I cannot find anyone that actually did perform this on their IS300

98 TT Supra rotors are vented.
 

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This may be a bit of a backwards way of going about this, but is there a hub/knuckle (terminology?) that you could source from a bigger car that would bolt to the IS, thereby allowing its respective brake system to be added?
 

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Discussion Starter · #20 ·
I’ve been deep in the car game for close to 30 years @BallerISandMR2guy - this is the first Lexus, I actually haven’t played a lot in the import scene.

There could be crossovers that might work, but then the worry is geometry. If it makes it worse, then it’s pointless.

The option is there - but there would have to be some digging into what actually works.

If you hear anything, let a guy know!




This may be a bit of a backwards way of going about this, but is there a hub/knuckle (terminology?) that you could source from a bigger car that would bolt to the IS, thereby allowing its respective brake system to be added?
 
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