Front brakes are sticking

[mgless]

Hopefully this is another easy one... front disc brakes functioned fine previously, then I swapped out my wire wheel hubs for a set of used bolt-on hubs. Wheel spins fine before bolting on the caliper. After putting the caliper back on, there is so much friction I can barely turn the wheel. Is there any sort of adjustment I need to do? I have already bled the brakes and have a nice firm pedal. Rear drums are functioning correctly.

 

[Gerard]

Did you swap the disc rotors as well? They are not the same between wire and disc wheels.

 

[mgless]

Yup, the rotors were still attached to the used hubs that I acquired.

 

[Billm]

It could easily be that your master is not adjusted correctly, but not necessarily the issue.
If the disks are rusty then they will drag until you get a few "stops" on them but if this isn't the case then it could be your master.
First- we need to know what year is the car?
BillM

 

[mgless]

It's a 65, Mk III Sprite. The bolt-on hubs & rotors are from a 72 Midget.

The discs don't seem to be rusty, certainly nothing out of the ordinary.

 

[RickB]

Did you put in new pads or use the old ones?
If new don't discount the possibility that they are wrong.
We have all seen so many parts that are wrong that I don't assume that just because something is new it is therefore correct. In fact it is safer to assume the opposite until proven correct for your car.

Also, I don't know this but it's worth checking, are pads for a 72 the same as pads for a 65 and which did you buy and use? If there is a difference then you want the 72 pads. Like I said, I don't know if there is a difference or not.

If you used new pads but still have the old ones I'd try putting the old ones in and seeing if the problem is still there.

 

[mgless]

I'm using the old pads. I didn't do anything to the caliper, just set it off to the side while swapping hubs.

I'm certainly not opposed to buying new pads if it would help. Looking at the Moss catalog, though, it looks like all years with front discs use the same pads.

 

[RickB]

Ok that's good.
Are the flex hoses to the front calipers in good condition?

 

[mgless]

Good question. They "look" fine, I think they're about 9 years old, but I can't remember for sure. They worked fine before I did the swap, but I could've strained them when I moved the caliper around.

When I bled the brakes, fluid seemed to come out of the bleed screws fine if that's any indication.

 

[Morris]

If you swapped rotors, I bet you just need to push your brake pistons in a bit. The other rotors where probably worn a bit thinner than the ones you have now.

 

[mgless]

That sounds logical. I've never had the brake pads out on this car -- should the pistons just push in by hand?

 

[Morris]

I doubt you will be able to push them by hand. I usually remove the pads and use a c-clamp on single piston calipers, but I can't remember how I did it when I last did my Midget. It sounds like they don't need to move much. Perhaps you can stick a pry bar of some kind between the pistons and gently pry them apart. Be sure to remove your brake fluid reservoir cap first. Also, be aware that this procedure will push fluid back into the reservoir, so if it is real full it may over flow.

 

[Billm]

Pull on your foot brake peddle to be sure that it fully returns by itself- the pivot bolt could be rusty and not allowing the peddle to come back up and that will keep the pucks from returning.
BillM

 

[RickB]

Pull on your foot brake peddle to be sure that it fully returns by itself- the pivot bolt could be rusty and not allowing the peddle to come back up and that will keep the pucks from returning.
BillM

Ah yes, I have had that one myself!!

 

[mgless]

Thanks everyone for your replies so far. I tried compressing the pistons last night -- seemed to work at first, but then after pumping the brakes a bunch I was right back to where I started.

I did notice while I was in there that the flex hoses looked worse than I remembered. There was some visible fraying in the rubber towards the end. I will see if I can pick up a pair today.

Didn't notice the brake pedal post until this morning, but I will be sure to check that as well!

 

[RickB]

I think those hoses go bad internally long before you usually see anything outside. It sounds like something is keeping pressure on the calipers, the pedal not going all the way back can also do that.
If you see signs of wear externally on the flex hoses then it's definitely time to replace anyway, having one blow when you need it most is not the way to find out it needs attention.

 

[Billm]

Check the peddle before you change the hoses- If the peddle shaft is sticking then you have to pull out the tray with the masters in order to clean and lube the shaft and you won't want to have to refill the fluid twice!!
BillM

 

[nomad]

Pistons could be sticking in the bores as well. Not uncommon with some age on the system!

Kurt.

 

[RickB]

Pistons could be sticking in the bores as well. Not uncommon with some age on the system!

Kurt.

Yes, you could have pitting or rust in the bores or on the piston surfaces and changing the thickness of the rotor by switching from the old to the 'new' would have put the pistons at a different place.
Any stickiness in there and you have trouble.

 

[mgless]

Just picked up the new hoses -- they needed to be replaced regardless. I'm not ruling out the pedal or calipers, though.

I'll dive back in tonight and report back!