Braking - pulls to LEFT...

Car is a fully restored 72 T 'hot rod', never wrecked or rusted car, and all of the suspension and brake components are new (using late Carrera calipers front and rear). Stock 72 master cylinder. Noticeable pull to the left when the brakes are applied - at speed or even at a few or less miles an hour coasting to a stop...steering wheel will quickly turn left. Issue has been present since its day one drive to present with 800 miles. Same symptom too from its initial 'garage floor' alignment to a properly done alignment rack alignment by a very experienced early 911 tech, so I'm confident it is not an alignment issue. Brake pedal has always been high and firm...not a hint of air in the system, so I have not yet re-done a brake bleed. I'm suspecting a front caliper issue...not sure if the LEFT is over-achieving, or the RIGHT is under-achieving? Any good way to tell? Other thoughts most welcome. Thanks.

Almost always the side opposite the pull not working a full capacity. Look for one or more stuck pistons, or a blocked fluid line.

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Originally Posted by Arne

Almost always the side opposite the pull not working a full capacity. Look for one or more stuck pistons, or a blocked fluid line.

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Thank you for the prompt and helpful reply. All brake lines are new as well, and all calipers seemed to bleed well (and the same), so I'm not thinking a blocked fluid line (unless you mean internal to the caliper?). If I remove (or at least undo) the RIGHT caliper and pull the brake pads out, I assume a light application of the brake pedal should show outward piston movement, and then be able to be compressed back...make sense, or a better way to check? Thanks again.

do not pull the pads out without inserting a spacer, maybe an old set of pads. the pistons might pop out.
New hoses too?

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Originally Posted by mac73s

Thank you for the prompt and helpful reply. All brake lines are new as well, and all calipers seemed to bleed well (and the same), so I'm not thinking a blocked fluid line (unless you mean internal to the caliper?). If I remove (or at least undo) the RIGHT caliper and pull the brake pads out, I assume a light application of the brake pedal should show outward piston movement, and then be able to be compressed back...make sense, or a better way to check? Thanks again.

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As David notes, pull the caliper off, but leave the pads in place. Insert a shim a bit thinner than the rotor. Late Carrera rotors are 24mm thick, so a piece of ½" to ¾" plywood would be good. With the shim and pads in place, apply the brakes gently to see if both pistons move.

Inspect or replace the flex line on the front brake caliper opposite the direction it pulls. I once had one that was faulty from the start. Same exact symptoms, drove me crazy trying to solve. If the hose end is not installed properly the inner liner can be cut, pushed into the fluid path and act like a one way check valve. Some fabricators run a ball bearing of the correct size through the hose after it's made as a check.

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Originally Posted by mac73s

Thank you for the prompt and helpful reply. All brake lines are new as well, and all calipers seemed to bleed well (and the same), so I'm not thinking a blocked fluid line (unless you mean internal to the caliper?). If I remove (or at least undo) the RIGHT caliper and pull the brake pads out, I assume a light application of the brake pedal should show outward piston movement, and then be able to be compressed back...make sense, or a better way to check? Thanks again.

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Originally Posted by R3350

Inspect or replace the flex line on the front brake caliper opposite the direction it pulls. I once had one that was faulty from the start. Same exact symptoms, drove me crazy trying to solve. If the hose end is not installed properly the inner liner can be cut, pushed into the fluid path and act like a one way check valve. Some fabricators run a ball bearing of the correct size through the hose after it's made as a check.

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Thank you to all who have continued to offer thoughts and directions. R3350 - can you explain further what you mean about the flex line 'hose end possibly not installed properly'...THANK YOU

Incorrect corner weights will also do that.

Right caliper piston(s) stuck.

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Originally Posted by mac73s

Thank you to all who have continued to offer thoughts and directions. R3350 - can you explain further what you mean about the flex line 'hose end possibly not installed properly'...THANK YOU

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Hose manufacturing defect requiring replacement of the flex hose.

+1 on corner balance.
Especially since the suspension was recently done. A proper corner balance is a must.

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Originally Posted by Tyson Schmidt

+1 on corner balance.
Especially since the suspension was recently done. A proper corner balance is a must.

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Thank you for this reminder...have not done it yet on this car, but had done so previously on my other 911 builds.

Post #10, in my opinion. Or take it all apart and start from s c r a t c h. Truly, it sounds like a inner flex hose defect/damage. @ least that would be a simple repair.

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Originally Posted by Cliff

Post #10, in my opinion. Or take it all apart and start from s c r a t c h. Truly, it sounds like a inner flex hose defect/damage. @ least that would be a simple repair.

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new
I appreciate the response and will be putting the car on my lift to start the diagnosis. Question though - since all calipers bled fine, if the new RIGHT flex hose was defective, wouldn't that have been obvious during the bleeding, i.e. the fluid first has to travel through that hose to the caliper. Perhaps a restriction...but not enough to keep it the caliper from bleeding properly? If I remove that flex line, is there a way to determine its integrity - or just best to replace it?

With the wheels free stomp on the brakes, then release, if the right seems to stay tight open the bleeder valve, if it releases the hose is defective.

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Originally Posted by edmayo

With the wheels free stomp on the brakes, then release, if the right seems to stay tight open the bleeder valve, if it releases the hose is defective.

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Thank you Ed..tomorrow's garage project! I'll report back what I ultimately determine the cause to be.

I did the stop and release a half dozen times and both wheels turned freely. I then had my wife progressively/incrementally apply and hold the brake pedal in positions from very, very slight application to full application - with me going side-to-side to check the brake drag until wheels could not be turned...absolutely no discernable difference left to right. I assume that would rule out concerns about the RIGHT side (or any) of the flex lines? Again, super nice solid pedal...but any value in trying a brake bleed given the results above? Thank you all for your continued thoughts, and yes, will do the corner balance.

Alignment and tire pressure too.

I've had an intermittent pull to the left under hard braking (intermittent…though far too regular…) since a complete brake system rebuild (four rebuilt calipers, new rotors, new master cylinder, and all soft lines), and still have it—though far less so now.

What I've learned so far: worn steering links will really exacerbate even a small issue. Replacing my gear from the rack to the wheels cut 80-90% of the problem, but that's not good enough. Now for that last 10%. Reading along in the comments, and thankful for them. My next moves were front flex lines and checking to see if one of the front calipers was rebuilt with a re-sized piston.

I've experienced this in only one consistent circumstance...

When rolling up to a stop over a diagonally undulating surface, where my front suspension is loading/unloading unevenly...

I happen to have an a very well traveled controlled intersection close by that has this particular condition IN BOTH DIRRECTION !!!!!...….. :rolleyes: