Brakes Pull to the Right Options

[bkrantz]

Some of you might remember my struggle to get what I considered strong braking, even after many rounds of bleeding, bedding, pad brand changes, and voodoo. I finally noticed how much the firewall flexed and the master cylinder moved under hard pedal pressure, and built a brace to support it. See my main thread.

On my first drive of 2023, the brakes finally felt strong, and I could lock up the front pretty easily. But with strong brake response I now have strong pull to the right.

I did set the rear pad clearance on both sides, inside and out, to .004".

Any suggestions?

One thing I have not done yet is corner weight balance. If the right front (and left rear) are carrying too much weight, would that make the car pull to the right as the weight shifts forward under hard braking?

[Superhawk996]

99% of the time pull is in the brakes. The chances of having corner balance creating brake pull on the street while braking in a straight line is exceedingly rare. Especially since you didn’t notice the problem before winter storage.

My bet is that over the winter you’ve had air consolidate into a large bubble - probably in the left front brake line. As a result, that side is less effective than the right side brakes.

Less likely but not impossible is stuck piston or binding pad on the left caliper.

After that I’d be looking at alignment and tire pressures.

Very few production vehicles have perfectly even corner weights. Regardless, brake pull isn’t an issue when the brakes are working properly.

Assumption: ride heights are relatively even right to left (+/- 6 to 10 mm) and weren’t changed over the winter.

Assumption #2: car was stored indoors and the brake rotors look the same left to right. Parking cars outdoors for long periods with one side more exposed to prevailing weather can cause rotors on one side to corrode more than the other. Result: uneven braking that usually cleans up after some driving and the rotor surfaces become more similar.

[PatMc]

Can't remember if you put new hoses on it or not, but that's where I'd start. If you're calipers haven't been rebuilt in a while, I'd do that too....doesn't take much corrosion getting under the boot to drag a piston.

[bkrantz]

Thanks, guys. Yes, I know the corner weight difference is a long shot. But I want to motivate myself to get to my friends garage and use his scales.

Anyway, some other info. The system was all new or rebuilt by PMB, including the calipers. All the hard and soft lines were new. Everything has at most about 300 miles so far.

The car sat in my garage all winter, so unlikely that corrosion (if any) affected L and R disks differently.

I went through an exhaustive process for ride height and alignment last year, and did not touch any of that over the winter. I just set tire pressures. I will recheck the alignment to see if something changed.

BTW, I did sense a weak pull to the right last year, when I could not get full braking force.

[Dave_Darling]

If you have a wonky alignment, it can also affect the brakes and make them pull to one side or the other. Since you mention corner balance, it's almost universal to have an alignment done after. Hopefully you did, but if not this may be a contributor.

--DD

[r_towle]

Front and rear bearings, bushings, trailing arm mounts?

Go find a parking lot (empty) accel to 40, then lock up the brakes hard.
Which one locks first?
Get a spotter, or look at the rubber marks.

[Spoke]

What are the rotor temps after driving? If one caliper is dragging the rotor and pads will heat up and could brake harder than the cooler side.

[NARP74]

Do you have a proportioning valve installed, usually for the rear. Output of one side could be impeded.

We are getting to Zebras though, start with the horses.

[Front yard mechanic]

Only hit the brakes when your turning right

[Superhawk996]

Only hit the brakes when your turning right

(IMG:style_emoticons/default/lol-2.gif) good point - driving a 914 is all about maintaining momentum and keeping cornering speeds up.

Now . . . About those left turns (IMG:style_emoticons/default/biggrin.gif)

[r_towle]

Only hit the brakes when your turning right

Solved! (IMG:style_emoticons/default/beer3.gif)

[NARP74]

Is turning left and pulling right like understeer? I hate understeer.

[bkrantz]

Only hit the brakes when your turning right

Hey, this isn't NASCAR. Which actually requires turning left.

[76-914]

If NASCAR holds an event in the southern hemisphere will run it clockwise? (IMG:style_emoticons/default/confused24.gif)

[bkrantz]

One more data point after driving today: I feel little pull when the brakes are cold, or when I start applying force and the car first starts to slow. The pull comes on only after the car has slowed.

[r_towle]

You might want to flush the fluid and bleed them again.
Might be something wonky in the fluid that expands or contracts based on temps

I was struggling with brake drag on a Volvo and I learned a new thing (for me)
The piston retracts only from the force of just the rubber boot wanting to go back to its natural state.
That is not a lot of force.
Admittedly it only needs to retract a mm or two

But, if there is any dirt, rust, particles, it can (and does) easily get stuck
Brake fluid attracts water
These cars sit around tons more than our daily drivers
An annual brake flush might become a thing for me.

I will say, I bought the vacuum brake tool that sucks the fluid through, and that makes the whole process much simpler.