switchblade327
11-29-2010, 08:55 AM
My car has been in a resto shop for the past couple of years while I've been abroad for work but I'm back now and trying to take care of some of major issues that are still plaguing it, to get it back on the road.
Anyway, my '55 Bel Air (which I know is not a typical PT car but I'm trying to build it to perform) has been switched to 4 wheel discs but when test driven, it barely stopped, with apparently not enough pressure. I wasn't the driver and the car isn't running now so I can't describe it better than that. They've bled the crap out of the lines and still nothing. There are no apparent leaks so we suspect a mismatch of the components.
The front brakes are a kit from Danchuk, with 13" corvette rotors and PBR calipers like this:
http://www.danchuk.com/ItemForm.aspx?item=12817 I went with it because it was a big disc, good price and didn't modify track width like many kits for these cars do.
The shop owner was concerned that the calipers of this kit only grab about 50% of outer edge of the rotor and not the entire surface of the disc. But Danchuk has been selling this kit for years with no complaints about people not being able to stop. It may not be the best brake kit but I can't believe they'd be selling an inherently dangerous design.
The rears are 12.25" Wilwoods and were done much later when the stock rear axle was swapped to a 9" (hence the total mismatch).
Before I continue, am I crazy to run this combination? Of course matching brakes would be nicer but is this combination at least safe and usable?
The master cylinder is a Corvette disc/disc (not sure what diameter) with booster. The proportioning valve is a nonadjustable GM one, possibly disc/drum.
My thought is that the master cylinder is the most likely culprit. The proportioning valve is probably wrong for this setup and will be changed if incorrect but if I understand (nonadjustable) proportioning valves correctly, neither one would deprive the front brakes of adequate pressure to stop.
With having discs this big, is a stock style disc/disc master cylinder going to cut it or do I need to go to a smaller diameter aftermarket master cylinder?
Are the brake lines a potential problem here?
Any recommendations for diagnosing? I have about one month to get as much done as I can on this car before leaving again so I want to attack this problem with a vengeance.
Any help in troubleshooting this would be very much appreciated.
Anyway, my '55 Bel Air (which I know is not a typical PT car but I'm trying to build it to perform) has been switched to 4 wheel discs but when test driven, it barely stopped, with apparently not enough pressure. I wasn't the driver and the car isn't running now so I can't describe it better than that. They've bled the crap out of the lines and still nothing. There are no apparent leaks so we suspect a mismatch of the components.
The front brakes are a kit from Danchuk, with 13" corvette rotors and PBR calipers like this:
http://www.danchuk.com/ItemForm.aspx?item=12817 I went with it because it was a big disc, good price and didn't modify track width like many kits for these cars do.
The shop owner was concerned that the calipers of this kit only grab about 50% of outer edge of the rotor and not the entire surface of the disc. But Danchuk has been selling this kit for years with no complaints about people not being able to stop. It may not be the best brake kit but I can't believe they'd be selling an inherently dangerous design.
The rears are 12.25" Wilwoods and were done much later when the stock rear axle was swapped to a 9" (hence the total mismatch).
Before I continue, am I crazy to run this combination? Of course matching brakes would be nicer but is this combination at least safe and usable?
The master cylinder is a Corvette disc/disc (not sure what diameter) with booster. The proportioning valve is a nonadjustable GM one, possibly disc/drum.
My thought is that the master cylinder is the most likely culprit. The proportioning valve is probably wrong for this setup and will be changed if incorrect but if I understand (nonadjustable) proportioning valves correctly, neither one would deprive the front brakes of adequate pressure to stop.
With having discs this big, is a stock style disc/disc master cylinder going to cut it or do I need to go to a smaller diameter aftermarket master cylinder?
Are the brake lines a potential problem here?
Any recommendations for diagnosing? I have about one month to get as much done as I can on this car before leaving again so I want to attack this problem with a vengeance.
Any help in troubleshooting this would be very much appreciated.