I have a 91 CRX DX with CRX SI rear disks, and DA integra front brakes (EF EX knuckles) and I also have some 17CL15VN ITR calipers and 23T brackets on the way so I might go with that front setup. I also have the ITR brakebooster and 1" MC. Car is being prepped as a track car.

Currently I have the 1725 prop valve on it right now and I have a parts bin with a 3540 in it from an EF EX

I see contention in this forum that the numbers are basically 'part identification numbers' and do not dictate proportions/ratios so I'm not sure the best direction.

 

Leave your stock valve, which is already a rear-disc valve. You are sort of correct about the number. It is a valving identifier. The problem is that the number itself doesn't really mean anything.

The trick is you must test your new system out. You don't want the rear end locking up under heavy deceleration. This can only be tested in high traction conditions and can be dangerous. So be careful. Hang onto the other valve just in case you need to give it a shot.

 

94eg's reading must be bad. The 1725 he has on there now is not the proper vavle for big brakes up front and rear discs.

Try the 3540. If THAT doesn't work, then get a 4040.

There's no exact definition to the valves. Even the 4dr sedan with DA brakes up front uses a 3540, but has rear drums.

 

Oh. I assumed the 1725 was the stock valve from his 90 Si.

90 Si comes with rear discs and 54mm front caliper pistons. Personally I would match the prop valve to the rear brakes and weight distribution. A CRX has a shorter wheel base and will transfer more weight off the rear tires than a sedan. Meanwhile the bigger 57mm front pistons and larger rotors add more front bias. This is why I suggested testing vs, simply swapping it out.

Personally I would rather add 03 Si rear rotors (if needed) to bring more bias to the rear. Rather than a different prop valve. But it all depends on what you want and how much you want to spend.

 

Tyson, have any more 4040s laying around for sale?

1725 is stock for the DX (9.5" discs front and drums rear) and the SI (9.5" discs front and 9.x discs rear). I've driven an STS SI and felt like the stock brake bias was pretty decent (with 15x7.5 with 195 R1Rs) but with the 10.3 or 11" discs in the front and SI rear discs with 225mm R comps, I think I'll need more rear bias

 

im not going to bother selling any more for now.

 

Let me know if you do. I'll try the 3540 for now, but I like to have tuning options.

 

if you want more rear bite, change the rear pad.

 

Yep, on the CSP miata I used to race, the front brakes lock up so bad that most people run HP+ rears and Durlast fronts . It was like night and day better when we did the same thing.

Just found a 4040.