grumpi300

iTrader: (1)

oldmantan, it looks like from the pictures I've seen, that the prop valve can go anywhere on the REAR brake line, would make it better if the handle was a little easier to get too. so I would go ahead and guess either closest to the master cylinder where the handle can be easier to get too. but I have seen some pics of somebody, I don't think I would ever do this though, put it on the center console. so if they were driving down the street or drifting or track or whatever, would be easiest to get too.

fried_rice

iTrader: (20)

I had the same dead space you guys are describing with LS400/stock rears and stock Master cylinder. I tired everything, bled them 100 times, etc, with the same results. I'd also experience fade after a few laps, which required pumping the brakes.

All master cylinders I've pulled from the SC's say 1 1/16th. Which is the same size as the MKIV master.

Solution to dead space was rebuilding all 4 calipers, LS400 front and TT rear with stainless brake lines and stock master/booster. I believe the issue most people have with upgrading to LS400 calipers, people buy used, which is what I did initially, and also using old worn rear calipers.

I use Castrol SRF, which is the best brake fluid I've come across. I'm still using the same fluid after 24 hours of hard track time and 150mph stops. Tried many other brands including Motul 660, and all would boil after heavy braking at tracks known to boil brakes after a lap or two.

After putting rebuilt calipers (LS400 front/TT rear) and stainless lines, the brakes bled immediately and have no dead space whatsoever. My car is a road race car so brakes are very important. I have no fading or brake issues at all with braking just as good as any car on the track I've come across. I've driven a few other high end racecars and my car brakes better, with better feel. Also had other people drive my car and their opinion was the same. My car only weighs 2500lbs dry so it's more than enough brake to lock up all four 305 slicks at any given speed. I have my ABS unplugged, but have been too lazy to run new lines to totally remove it.

Stock master has a proportioning valve, no need to add an aftermarket valve unless you are a professional driver with a racecar only.

grumpi300

iTrader: (1)

thanks fried_rice. I appreciate the information. so now I know that abs can be completely removed and just reroute lines to all 4 wheels. no proportioning valve necessary. I will call lexus to verify this as well though. its better to hear this from 2 sources. i'll call on Monday.

fried_rice

iTrader: (20)

Yes, removing the ABS module has been done many times. If you're removing the ABS use a brake line flaring tool and make new hard-lines. I wouldn't trust using braided lines and T's on my car with the speeds I hit. I'm sure it would be fine if done properly. Get pre-made, hydraulically pressed stainless lines. I recently made some high pressure -3AN line with the screw on fittings and no matter what I tried it would leak. Not something I want to happen at 150mph+++

The proportioning valve is used to very finely adjust the brake bias for braking characteristics under track conditions. For instance if your car is over-steering badly or locking the rears up. With the LS4/TT, LS4/SC, or TT/TT calipers brake bias is pretty damn good. The racecars I see have them mounted in the cockpit, so they can change the bias as track conditions change, driver preference( multiple drivers), etc change.

I said "porfessional" driver, but what I should say is if you aren't pushing your braking 100%, you will most likely not be able to properly dial in the brake bias correctly. You'd need testing and experience of how the car is supposed to act at the high levels of braking. It would just add another factor to possibly make the car brake worse.

You can get an idea of removing the ABS from the link below.
https://www.clublexus.com/forums/sus...ac-delete.html

grumpi300

iTrader: (1)

so there is a writeup. haha. I have searched all through google for "sc300 abs removal" but I forgot to check clublexus for some reason. haha. anyways, I think it a good write up I just still think prop valves are important to have for daily use as well. it would be a bad think to happen if your rear wheels locked up during daily driving but front wheels barely grab. I know adjustable prop valves aren't as good as factory but it is better than nothing. unless of course theres already one on the master. I know i'm making this harder than it has to be, but Im a major perfectionist and prefer to have stuff done right and not do it a second time.

fried_rice

iTrader: (20)

The stock master cylinder has a proportioning valve inside it. The rod has a different sealed section and as it moves it pushes more fluid to the front than the rear. That is why it has outputs for front and rear brake lines.

grumpi300

iTrader: (1)

yeah fried rice. you are right. the master cylinder has a proportioning valve built into it. I called lexus as well to verify. so all that is needed is to remove abs is just remove the block and tee the front brakes together and the rear brakes together. remove the fuse and abs module and no light on gauge cluster. sounds simple enough. but knowing how much of a perfectionist I am, i'm going to want to run all new lines, tee in the perfect spot, remove all the wiring to the abs and module, remove the bulb from guage, it would probably take me about a week. haha.
anyways, since what happened to my vehicle, (car accident), I am not planning any more work on it till I either get my settlement check and get it fixed or just buy a new one. its a salvage now according to the first autobody that I went to. the cost of repairs is worth more than my car. :/ I still want to take pictures and show you guys but since I don't have a phone and i'm always at work, even now as I type this, it's been kinda hard.