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Brake Issue

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Rob Glasgow

Rob Glasgow

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In driving my BT7 for 55 years, I never had any issues with the braking system except replacing the pads and one or two master cylinders due to leaks. The brakes have always stopped the car with some effort, but what I was used to with other non-power brake vehicles I've owned. It would never slam you towards the dash like modern power brakes.
During my restoration last year, I replaced the master cylinder, new rear shoes and wheel cylinders, new ceramic front pads, new stainless braided hoses. Bled the system and have a decent firm pedal. So what's the issue?
When I make a slow right hand turn, I get a rapid metallic clicking noise from the front right wheel area. Sounds like the brake pad is loose and rattling against the rotor. When I apply a little brake while turning the corner, the sound lessens a bit and if I push hard on the pedal, the clicking goes away. So it seems brake related, but when I look at the right pads at rest, they are tight against the rotors and I can't detect any slack. The is no clicking when I make a left hand turn.
So what do I tackle next? I did replace the caliper pistons 15 years ago but have never disassembled the calipers. There are no leaks in the system, front or back.

Another question, in testing the brake system, I am not able to lock up the front brakes, no matter how hard I step on the pedal. The rear brakes will lock up, but never the front. Should I be able to lock up the front brakes in a panic stop situation?

Other than the weird noise on right turns, the brakes stop the car in a reasonable distance and the front end dives if I apply the pedal with some force.

Any ideas?
 
I've never had a car I couldn't lock the brakes on so I think you do have a problem.

I don't think the clicking as you describe it is related to not being able to lock the wheels. I have experienced a faint clicking that quiets and goes away when the brakes are lightly applied and traced it to a slight thickness variation in the rotor - only takes a thou or two. What happens is there is light residual pressure from the sealing rubber keeping the pads in contact with the rotor and if there is a thickness variation the pads get lifted as the thick area of the rotor goes between them and then the thinner section follows and allows the pads to drop back down resulting in a faint clicking sound, very rhythmic and doesn't affect brake performance at all. You can check by micing the rotors at various points to see if there is a variation, again it only takes a thou or two.

As to the inability to lock the wheels, You said there are new rear wheel cylinders and master but you don't say if the calipers were rebuilt in the resto, if not, then that is the first thing I would do. Ceramic pads usually need to be hot to work best but even so, you should definitely be able to lock the wheels. I wouldn't drive it except for testing until you can lock them.
Dave
 
To Me, that sounds like a suspension issue. I would look at the wheel bearings.
 
All the above are good things to check. Here's some other thoughts. Do you have the thin metal, anti squeal shim in place between the pads and the pistons. The pad may be catching on the piston at times. Also the shim is directional don't know if it can be put in wrong but I would check that. As for the lack of ability to lock up the fronts, I would blame the ceramic pads. Depending on their compound, ceramic pads many times don't do too well in street driving. Characteristics from squealing to stopping power have been expressed. Having said all that I would agree with Greg, that sound you are hearing is commonly related to wheel bearing.
 
Thanks for the suggestions. The ceramics pads were from Moss and they are advertised for normal road use. Yes I did use the suggested bedding procedure when I installed them. Other than replacing the caliper pistons 15 years ago, I have not rebuilt The calipers. I was always told to never split the calipers but I guess with the new flat o ring available, I will do that. I haven't looked at the wheel bearings but in turning the wheel on the car, everything seems smooth, but it's worth a look. I. Do not have the shims installed. I've always used the smear on product on the pads.
 
I agree with all the folks and I would put the ceramic pads inah bin.
 
You don’t need to split the calipers to replace the seals and dust boots. If they’ve been in there for 15 years, they are due, if not overdue.
 
If you have the square-section o-rings, splitting the calipers is trivial. If you do that, you can do a great job cleaning the bores. If you clean them up and make sure the piston ring groove is clean, a few little pits won't matter, as the sealing is between the rubber seal ring and the piston. New pistons aren't expensive either. I'd just get the parts and do the whole thing at once & paint the calipers - it's easy and Bob's Your Uncle!

PS - I think all the angst about splitting the calipers is left over from when the square-section o-rings weren't available.
 
Well if you do not have one of em square gaskets, U kinda up the creek with no paddle N rocks in U pocket--LOL
 
EBC - Green Stuff Made in U.K. Organic material. Good initial bite better stopping power. Some dust. Summit Racing has them. I like them. GONZO
ebc-dp2169_w.jpg
 
Verbiage at bottom. (PN is Moss PN):
This is the O-Ring that goes in between the two halves of the Girling Caliper. This is not included in any of the caliper rebuild kits. Measures 0.480 outside diameter x 0.075 in thickness. Cross Reference 583-820

screenshot.1337.jpg


Last time I looked online, there was plenty of discussion on whether or not to split the calipers.
 
Gonzo, I wanted to try the EBC green stuff pads but couldn't find them for my BT7. I've only seen them for a BJ7 or BJ8.
 
gonzo said:
EBC - Green Stuff Made in U.K. Organic material. Good initial bite better stopping power. Some dust. Summit Racing has them. I like them. GONZO
ebc-dp2169_w.jpg
Click to expand...

Yeah much better N that metallic pad.---
 
I'd like to see some real data--not just anecdotal or manufacturers' claims--as to the relative stopping power, fade resistance, etc. of semi-metallic, EBC, and other brands/types (compositions). Anybody have applets-to-apples data?
 
Bob_Spidell said:
I always wondered if maybe the cross-bolts were installed 'torque to yield,' in which case they shouldn't be reused.
Click to expand...

The TTY theory makes some sense in view of the mattress-tag-level scariness espoused about separating the halves.

Bob - If the bolts are TTY, they would be torqued until they stretch and can't be safely reused. Can one visually tell if they've previously been TTY'd?

My Jag rear calipers have a crossover pipe - no internal sealing ring. They are often disassembled in order to mount up. DW even sells a flex line so you don't have to undo the hydraulics when you're separating the halves.
 
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