whitedevilTA

iTrader: (8)

I have had C5 front brakes for years now, along with factory LS1 rears and an LS1 master cylinder. Ever since doing the conversion, the stopping feel just seemed "off." By that, I mean when coming to a stop under normal driving, it would seem like I had to push the pedal down too far before the brakes would start to engage and slow the car down. This issue has bugged me for years until I recently decided to look into it in depth, and I found the fix. Since many of you have posted and mentioned the same lack luster feel, I wanted to share. Read on...

Many people blame air in the master as the culprit, and this was a definite possibility. However, after bleeding the master multiple times as well as the proportioning valve and all brakes, the issue never got better. I finally started to notice that with the engine off, the pedal was nice and stiff however it didn't feel stiff until it was depressed about 3/4" to 1". Because the LS1 master is not the OE unit, I decided to look into my brake booster pushrod length and see if thats where the play was. Low and behold after taking some measurements, I found that the factory booster pushrod is roughly .100" too short which left about a 1/8" gap between the pushrod and the back of the master. While this doesn't sound like a lot, because the brake pedal is 10+ inches long, that .100" is quite a bit at the pedal pad.

The correct distance between a master and brake pushrod is .020" or less. It just can't be putting positive pressure on the master or else the brakes would always be slightly engaged, but the point is to get it as close to touching as possible. Luckily, my profession is a machinist at an aerospace company, so I made a new pushrod on the lathe which was approximately .100" longer than the stocker. This 100% fixed the delay in braking feel, and the brakes now engage after about 1/4" pedal travel and feel absolutely perfect like every other factory braking system. It made a HUGE difference in the driving feel and confidence I now have when coming to a stop under normal driving. Another alternative to making a new pushrod is to make a .100" sleeve to slide over the rear recessed area of your stock pushrod to make up the distance. There should be enough meat on there to get away with it. I would just be sure to either solder or red loctite the sleeve on so if you ever have to remove the pushrod, it comes out with it and doesn't drop into the booster.

I encourage everyone that runs an LS1 master to look into this, because if you still use the factory booster and booster pushrod, I can guarantee you there is too much pushrod play in your braking system!

yankeecarman

iTrader: (9)

Thanks for the info. Its always good when someone posts on here to help others with similar problems.

whitedevilTA

iTrader: (8)

No problem. I've been racking up miles on the car now since it's such a joy to drive knowing the brakes stop and perform as they should. I always hope I can help others out with problems that made me pull my hair out for so long!

sofakingdom

iTrader: (1)

Any idea whether the stock push rod in a LS1 booster is the right length? If so, it'd be a buzzard nest item.

whitedevilTA

iTrader: (8)

I'm honestly not sure. Never had one in my possession to confirm. Luckily, the pushrod is a relatively simple piece and wouldn't take much to make, even without the use of a lathe. Still would be interesting to compare a factory 3rd gen one to a 4th gen one and see if in fact the 4th gen version is slightly longer.

86White_T/A305

I gotta say that with my ls1 front/rears..the pedal feel still doesn't inspire confidence in the day to day life for stopping. If I jam on the brake then yes...the car halts.I put on ebc pads/rotors and love the bite they have but the pedal travel has always been something I want to rectify. I still have a new/stock replacement booster and master. So I wonder if this would still apply for a stock master setup,unclear if .100 would engage the brakes while at rest.But if you have another booster rod..Id be guinea pig lol

QwkTrip

iTrader: (22)

Glad you posted this. This confirms what I have suspected is the real problem with my brakes. I even bought the MP Brakes tool to measure the gap but just haven't gotten around to doing the job. You just confirmed it is probably a job worth doing. Thanks!

Ya, my car stops but the lousy pedal feel has kept me from running the car hard for fear of losing brakes. I've had no choice but to assume there is still air in the lines until I could prove otherwise. If get a good pedal then I'll probably do more with the car.

DynoDave43

iTrader: (11)

Made any progress on this issue QwkTrip?

QwkTrip

iTrader: (22)

No, didn't want to disable the car this summer for any reason. Just wanted to drive and enjoy! I have a list of things to do over winter when I can't drive it anyway.

DynoDave43

iTrader: (11)

Understood. Hope you find a fix for this over the winter.

86White_T/A305

I do have an update related to this topic. I mentioned earlier about the pedal feel being lousy and i have decent pads/rotors. I found my issue..its indeed the brake master! I took my car to a friends shop and we dove into the brake system fully.Checking all the lines,calipers etc for leaks and bled the system. I was noticing that every so often I had top topup the master. The master was only 2 yrs old,the booster is 1yr old,new caliber lines last yr also. After bleeding the system the car would have great firmness..once. Tested the master and low and behold it was indeed seeping.

I decided I want to get a known brand master instead of reman parts or cheap 3rdline crap. I ordered centric premium replacement master on summit. Put it on and did it ever change the whole brake feel. I could never get the car to really lock up unless i jammed my foot to the floor..maybe the fronts would.Now..all 4 would flat spot if i gave it and good stomp. A light tap when the ebc's are warm and the seatbelt locks into place lol i barely need 50% the effort I used to halt the car. I thought I might need to change the rubber lines upfront for steel just to get this kind of braking power.Not anymore..Id be very confident stopping the car at the strip or circuit or in a panic.Very crisp...I probably didnt need to get the ebc's stuff if I had replaced the master first lol

DynoDave43

iTrader: (11)

Sorry to ask...this new one is a stock, 3rd gen. 4 wheel disc master cylinder?

86White_T/A305

Yes I did a stock 3rdgem replacement master for 4 wheel disc cars. Its nice not having a yellowed brake reservoir too lol.