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Question for guys running tilton dual brake master cylinders

Old 04-25-09, 12:23 PM
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Question for guys running tilton dual brake master cylinders

Not on my RX-7, but I figure this sort of info is universal...

A buddy of mine just installed a Tilton dual setup on his PTE 2nd gen Integra. After a hell of a time getting everything bled, the brakes work, but not very well. There is quite a bit of loose pedal travel before it hits the hard spot, and we can't lock up the wheels no matter how hard the brakes are stomped on. When they're pressed the cylinder for the fronts moves much further than the one for the rears, but I think this to be expected, as it's a smaller diameter piston (which is what was recommended by Tilton for this application) and the front caliper pistons are much larger, so there's a larger volume of fluid to displace, and a smaller piston doing the displacing.

We have the balance bar set pretty much in the center right now, but we experimented moving it front and back without any real change.

Anyone have any tips for getting the most out of this setup?
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Old 04-25-09, 06:41 PM
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First, be sure the balance bar is perpendicular to the masters when the pedal is pushed hard. It will be crooked at rest. Adjust out the slack with the pushrods and make sure there is a little play so the line pressure can be released back to the reservoir. With the bar in the center you should at a good starting point if Tilton gave you the master sizes after going through their website tech service. Driving the car hard will be the only way to get it right and it will change with fuel load, wet/dry, etc.
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Old 04-26-09, 12:00 AM
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sounds to me like you need a bigger front master cylinder.

the bigger the cyl, the firmer and higher the pedal. You know you've gone too big when there is no travel and the effort is too high .
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Old 04-26-09, 09:12 AM
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I agree with racing driver. A bigger front master will bring the pedal up. The big issue you have is a small piston volume in the rear caliper and a large volume in the front. You need to supply more fluid to the front with the same cylinder travel as the rear. I went from a 7/8" master for superlite 6 calipers to a 1" and the pedal sits higher and pressures up much earlier. It does require a bit of a push though.

-Trent

Originally Posted by racingdriver View Post
sounds to me like you need a bigger front master cylinder.

the bigger the cyl, the firmer and higher the pedal. You know you've gone too big when there is no travel and the effort is too high .
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Old 04-26-09, 10:21 AM
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The problem with going with just a bigger front master is it may change the bias beyond the point that the bias bar can do anything for you. If they went through the Tilton tech page that you can fill out all your dimensions they should be as close as you can get. You can choose a pedal pressure range and you will get different masters for the same application.

The problem can be that there is no good choice of masters to match at higher pedal pressures. Lets say that for a 120 lb pedal you need a 3/4 for the fronts but the rears require something bigger that doesn't exist. They may be stuck with a little lighter pedal so they can use a 5/8 for the front and a 7/10 for the rear or something like that.

On my car I had to change the point on the pedal that the bias bar attaches so I could get to a 6:1 ratio from the pedal. The stock location was closer to 5:1 and we couldn't find a master combo that would work to give me a medium pedal (around 80lbs).
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Old 04-26-09, 09:21 PM
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Adjusting the piston clevises so that the bar was at an angle at rest and even when hitting the brakes helped things out a lot. If we'd read the manual we would have figured that part out faster :p The pedal is still pretty stiff but he managed to run a 40 minute race at Summit without getting tired out and was able to lock the brakes up if he really wanted to, so it looks like we're all set. Thanks for the help.
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