Brake upgrade (qausi-writeup)
06-02-2009, 05:48 AM
#1
Brake upgrade (quasi-writeup)
I have read a bunch of posts here and there about upgrading your brakes. The purpose of this post is to give some details about the upgrades I tried and encourage anyone who is considering doing the same.
I'm not in a position to take extensive pictures and document my little brake upgrade project, but bear with me anyways. I had been struggling with a squishy brake pedal, even after multiple very thorough bleedings. I found that I often had to pump my pedal twice to get a firm pedal and the truck would often dive forward. Here's what I did:
1) Got a set of V6 calipers from Pull-A-Part ($20) off of a '90 V6 4Runner to replace the 4cyl ones on my 4Runner. These have slightly large pistons and slightly wider pads. The calipers are also bigger and have cooling fins. Note that I had to grind off about 1/4" of my brake backing dust shield. After that, the bigger calipers just bolted right on!
2) I replaced my stock 13/16" bore master cylinder with a 15/16" one. I wanted one with a warranty so I ordered one from Advance ($50). It was technically from an '88 V6 4x4 Pickup. The output tubes were vertical rather than horizontal, so I bent the brake lines to fit it. Note that a slightly longer brake like was necessary to go from the front output tube to the t-fitting below the booster. This part was $0.95 at Advance.
3) My 4Runner has 3 inches of suspension lift or so. I built a little bracket to jack the LSPV bracket up by 3 inches. This has nearly eliminated the 4Runner's tendency to dive under hard braking.
Result: a firm pedal and positive braking! Using a larger master cylinder does decrease the hydraulic leverage, however. It's like a small kid trying to lift a fat kid on a see-saw. In this case the small kid is shortening his lever arm so he has to push harder but not as far. But in my case I was willing to have to push a little harder on the brakes to eliminate the excess pedal travel that I hate. But the larger piston size of the V6 calipers helps increase your leverage (essentially moving the fat kid closer to the fulcrum). I do think that the 15/16 was a better option than getting a 1" bore, which might have made the pedal too firm. If I had to do it over again I might have even sprung for a 7/8" MC for slightly more leverage and a slightly softer pedal.
I'm not in a position to take extensive pictures and document my little brake upgrade project, but bear with me anyways. I had been struggling with a squishy brake pedal, even after multiple very thorough bleedings. I found that I often had to pump my pedal twice to get a firm pedal and the truck would often dive forward. Here's what I did:
1) Got a set of V6 calipers from Pull-A-Part ($20) off of a '90 V6 4Runner to replace the 4cyl ones on my 4Runner. These have slightly large pistons and slightly wider pads. The calipers are also bigger and have cooling fins. Note that I had to grind off about 1/4" of my brake backing dust shield. After that, the bigger calipers just bolted right on!
2) I replaced my stock 13/16" bore master cylinder with a 15/16" one. I wanted one with a warranty so I ordered one from Advance ($50). It was technically from an '88 V6 4x4 Pickup. The output tubes were vertical rather than horizontal, so I bent the brake lines to fit it. Note that a slightly longer brake like was necessary to go from the front output tube to the t-fitting below the booster. This part was $0.95 at Advance.
3) My 4Runner has 3 inches of suspension lift or so. I built a little bracket to jack the LSPV bracket up by 3 inches. This has nearly eliminated the 4Runner's tendency to dive under hard braking.
Result: a firm pedal and positive braking! Using a larger master cylinder does decrease the hydraulic leverage, however. It's like a small kid trying to lift a fat kid on a see-saw. In this case the small kid is shortening his lever arm so he has to push harder but not as far. But in my case I was willing to have to push a little harder on the brakes to eliminate the excess pedal travel that I hate. But the larger piston size of the V6 calipers helps increase your leverage (essentially moving the fat kid closer to the fulcrum). I do think that the 15/16 was a better option than getting a 1" bore, which might have made the pedal too firm. If I had to do it over again I might have even sprung for a 7/8" MC for slightly more leverage and a slightly softer pedal.
Last edited by RustBucket; 06-02-2009 at 06:24 AM.
06-02-2009, 09:22 AM
#2
Registered User
Good to know there are some other options besides the 1" bore MC. I had upgraded the brakes on my '83 with the 1" MC and bigger calipers and it stopped great, but I now have an 88 4Runner and the brakes are really not that good. This is on my list, thanks for the info.
06-02-2009, 10:23 AM
#3
Great, hope it turns out well.
As I scoured RockAuto.com for MC info I also found that certain 4runners and trucks had larger wheel cylinders. I think the small size is 7/8" bore and T100's used a 15/16" or 1". Presumably, if the larger wheel cylinders still fit inside the drum brake mechanism, they could provide a higher braking force. But since the LSPV is already reducing the pressure to the rears, maybe it doesn't make a difference... thoughts, anyone?
As I scoured RockAuto.com for MC info I also found that certain 4runners and trucks had larger wheel cylinders. I think the small size is 7/8" bore and T100's used a 15/16" or 1". Presumably, if the larger wheel cylinders still fit inside the drum brake mechanism, they could provide a higher braking force. But since the LSPV is already reducing the pressure to the rears, maybe it doesn't make a difference... thoughts, anyone?
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