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I'm having problems with the brakes in my 1969 Corvette.
I'm wondering why the brake pedal is so low on this car.
It is hard to see in the picture, but the brake pedal is at the same height as the gas pedal and the clutch pedal is much higher than the brake pedal:
Looking at the brake switch it looks like the pedal should sit much higher:
This is the third booster I've tried on this car. The first one (that was on the car when I bought it) was very sensitive, touch the brakes and they slammed on. The reaction disc had fallen off.
The next one didn't work at all. No assist.
This one seems to work (pedal sinks about 1½ inch when vacuum is applied).
I did some measurements on the three boosters I have:
Length from firewall to the brake pedal clevis is about 3 3/4'' plus the thread (about 4'' total) on all of them.
As I recall the clevis length is about 2'' from the threaded end to the center of the cross pin. I'm wondering if I have the wrong clevis?
It the clevis a Corvette specific item that is longer than normal? Or have all the boosters been wrong (the second one was bought from a "Corvette vendor", the last one from Summit).
The clevis is in the correct (lower) hole on the pedal.
Anyone know what's going on?
/Karsten
Last edited by Danish Shark; Apr 24, 2017 at 11:05 AM.
I'm having problems with the brakes in my 1969 Corvette.
I'm wondering why the brake pedal is so low on this car.
It is hard to see in the picture, but the brake pedal is at the same height as the gas pedal and the clutch pedal is much higher than the brake pedal:
Looking at the brake switch it looks like the pedal should sit much higher:
This is the third booster I've tried on this car. The first one (that was on the car when I bought it) was very sensitive, touch the brakes and they slammed on. The reaction disc had fallen off.
The next one didn't work at all. No assist.
This one seems to work (pedal sinks about 1½ inch when vacuum is applied).
I did some measurements on the three boosters I have:
Length from firewall to the brake pedal clevis is about 3 3/4'' plus the thread (about 4'' total) on all of them.
As I recall the clevis length is about 2'' from the threaded end to the center of the cross pin. I'm wondering if I have the wrong clevis?
It the clevis a Corvette specific item that is longer than normal? Or have all the boosters been wrong (the second one was bought from a "Corvette vendor", the last one from Summit).
The clevis is in the correct (lower) hole on the pedal.
Anyone know what's going on?
/Karsten
If your brakes actually work OK and the pedal does not go to the floor when you step on it, have you considered the brake pedal height may be OK, but the clutch pedal is too high? If the rubber bumper on the clutch pedal is worn or missing, the clutch pedal will be higher than normal. The clutch pedal on my 68 convert was about 1 1/2 inches too high until I replaced the bumper- then it was the same height as the brake pedal.
If your brakes actually work OK and the pedal does not go to the floor when you step on it, have you considered the brake pedal height may be OK, but the clutch pedal is too high? If the rubber bumper on the clutch pedal is worn or missing, the clutch pedal will be higher than normal. The clutch pedal on my 68 convert was about 1 1/2 inches too high until I replaced the bumper- then it was the same height as the brake pedal.
Thank you for answering
No, the brakes don't work OK. Without vacuum on the booster I have pedal, but very low. When vacuum is applied the pedal is almost at the floor (less than an inch left).
I can't rule out that the pin between the booster and the MC is adjusted too short and that may contribute to the low pedal when brakes are applied, but I have never seen another car where the brake pedal was in line with the accelerator pedal.
I tink (not 100% sure) that the rubber bumper for the clutch pedal is there.
No, the brakes don't work OK. Without vacuum on the booster I have pedal, but very low. When vacuum is applied the pedal is almost at the floor (less than an inch left).
I can't rule out that the pin between the booster and the MC is adjusted too short and that may contribute to the low pedal when brakes are applied, but I have never seen another car where the brake pedal was in line with the accelerator pedal.
I tink (not 100% sure) that the rubber bumper for the clutch pedal is there.
It sounds like you obviously have booster problems but those pedals are not supposed to be at the same height. On my 69 with the pedal bumper installed and original booster the clutch pedal sits about 1.5 inches higher than the brake pedal. You need the clutch pedal like that for proper clutch travel but you never want the brake pedal that high. GM designed it like that so when removing your foot from the accelerator pedal to apply the brakes it's a smooth transition and there is no chance of getting your foot caught behind the brake pedal on the way over instead of on top of it. It is supposed to be that low. I have a bit less than a half inch free play in the brake pedal.
½ inch travel, is that to the point where it starts braking?
Yes. About a quarter inch of free play where there is no pedal pressure except the return spring and then it starts braking on the discs at at about a half inch of total travel. Then it's mostly just more pressure for more braking without much more pedal movement. There is no sponginess at all. The entire setup is stock.
Yes. About a quarter inch of free play where there is no pedal pressure except the return spring and then it starts braking on the discs at at about a half inch of total travel. Then it's mostly just more pressure for more braking without much more pedal movement. There is no sponginess at all. The entire setup is stock.
Thanks, great info.
I will take it all apart again and check the total travel in the master cylinder and then compare it with how much travel the booster rod on the master cylinder side has with this setup.
I probably also have the rod in booster to master cylinder adjusted too short. I set it at 0.020 but I will reset it to 0.
Then I will probably weld a nut onto the booster clevis until I get a longer clevis (takes some time to get it from the US) so the pedal sits a little higher.
If your brakes actually work OK and the pedal does not go to the floor when you step on it, have you considered the brake pedal height may be OK, but the clutch pedal is too high? If the rubber bumper on the clutch pedal is worn or missing, the clutch pedal will be higher than normal. The clutch pedal on my 68 convert was about 1 1/2 inches too high until I replaced the bumper- then it was the same height as the brake pedal.
I have some similar questions. I just put a clutch and brake pedal into my 1972 housing to convert from an automatic. I noticed there was no rubber stop on the brake, and the brake pedal was stopping directly on the brake light switch, so I stuck the rubber stop that came for the clutch (it is the same part# listed where I ordered the pedals), on the brake side. It seems like it got rid of way too much travel. Someone answered a similar forum question saying that the AIM specifies 7 inches from the floor for the clutch, and 6 inches for the brake. The problem is, I was hoping to adjust the brake switch location while the pedal assembly is still out. Does anyone know if the rubber brake stop is the same as the clutch? Also, any idea how thick they should be. It seems that in order to adjust that brake switch properly the rubber stop needs to be in place.
It goes without saying that any air in your system will increase brake pedal travel so if it hasn't been done recently you may want to consider a flush and bleed.
Also it is difficult to tell but in the 2nd picture it does not look like the brake pedal is riding anywhere near the bumper. Is that correct?
Also it is difficult to tell but in the 2nd picture it does not look like the brake pedal is riding anywhere near the bumper. Is that correct?
Hi
The brake pedal doesn't have a rubber bump stop like the clutch pedal has, and as far as I know it shouldn't (not on a power brake car at least).
The pedal is quite far away from the brake light mounting tab, which is why I raised the question about whether the booster/clevis combo may be too short.
Knowing that the clevis is attached to the rod coming out of the back of a power brake booster. The distance from where the brake booster contacts the firewall and the hole in the clevis is a given length.
So...even if the 'book' shows a rubber bumper stop...it more than likely is NOT against it...because that would be telling me that the booster has not been allowed to fully go all teh way back IF it were resting on the rubber stop.
NON- power brake cars do have a rubber stop.
Karsten,
Hopefully you have your issue resolved to your liking.
i don't see a booster issue.
2 things
the piston in the master cylinder has a recess for the rod.
i have had to put my original piston in a new/rebuilt
m/c to get it right.
the pedal arm is against the brake switch, it could maybe go in about.25"
but thats it for pedal height travel . you have other brake problems.
0.25'' at the switch is a lot more at the pedal
I bought another master cylinder, but never got around to installing it.
I ran out of patience with this car. It also has engine problems so now it's just collecting dust and taking up space.
Last edited by Danish Shark; Feb 15, 2018 at 07:46 AM.
I had my original booster rebuilt from my 72' and the pedal doesn't come back far enough to contact brake switch now and pedal height seems lower than it used to be. I went back to whom rebuilt the booster and they said that there is only one length of push rod and mine is original. They suggested that maybe it wasn't bolted up completely to the firewall and brake pedal bracket assembly. So I installed it again and made sure its in completely, but still the same problem. I don't know what else to think other than maybe the Corvette had slightly different components which would give me the 1/4' more that I need. I may need to look at another car or I could make another clevis/rod bracket, but this used to fit just fine.
Brake pedal height
