M100 pulls left under heavy braking

[carlotus]

My m100 is pulling badly to the left under heavy braking. I bled the brakes, but it’s still pulling left. Any ideas what it could be. Alignment? Sticky caliper?

[Saltire]

Without seeing the car, it’s hard to be sure, but my guess is that the front right caliper (passenger side for you in the USA) has a stuck piston, sliders, or both. This is a known issue with the standard calipers, and will produce the symptoms you describe.

I remove mine every year, clean the sliders and piston, and check for full and free movement. There is a caliper overhaul kit available from the usual suppliers with new seals etc.

The LEC wiki is down at the moment, but I’ve copied and pasted the part about a front caliper rebuild below to give you an idea of how to set about it. There is also a section on the main LEC site - with pictures - which explains how to rebuild the rear brakes; it’s the same principle, but a bit more complicated.

As always,if you’re in any doubt about your ability to work on the braking system, best take it to someone you know and trust to do the work. Can’t be too careful

Wiki Extract

IMG_2246.png

[Tuga2112]

Exactly as. Jonathan says, in my experience the sliders are the thing that is more likely to require attention (unstuck regresse or complete replacement)

[carlotus]

Great feedback, I will have a look at the right front caliper today. I neglected to say, my m100 came with a brake upgrade kit. Subaru Legacy rotors with Saab 9-3 calipers. I guess this doesn’t matter as the principle is still the same.

Cheers,
Carl

[Tuga2112]

Great feedback, I will have a look at the right front caliper today. I neglected to say, my m100 came with a brake upgrade kit. Subaru Legacy rotors with Saab 9-3 calipers. I guess this doesn’t matter as the principle is still the same.

Cheers,
Carl

Although the principle may apply. You may find it simply doesn't apply at all.

For instance my Celica gt4 and my 4runner front calipers don't have sliders at all. That be because their 4 pot calipers where the back pressure on to the pads is made by pistons instead of having the caliper move. (There's no sliders)

[carlotus]

I believe I finally found the culprit. The set screw is missing on the right front rotor. Now to find a set screw

[Fredjohn]

Not familiar with Subaru/Saab set up, but the set screw normally merely holds the rotor in place until the bolts/studs/lugs are put on.
The rotor will not turn independently of the wheel and hub once wheel is tightened up.
Suggest you keep looking a bit deeper. If it's a 2 or 4 pot set up, and no sliders, then one or all of the pots are sticking on that side

[dapinky]

One extra thought, maybe the flexible brake hose is breaking up internally and blocking the return of fluid once the brakes are released?

[Simon_P]

Its always to the left...

The duel circuit brakes are imbalanced - follow the bleeding instructions in the manual and keep bleeding until it is sorted - buy 5l of brake fluid then you aren't concerned about running out!

To add to Jonathans post - you need to clean the piston as the seal can stick to the piston if the car doesn't get much use.

[carlotus]

I took out all 4 slider pins and greased them up and this has made a noticeable improvement, but still pulls a little to the left. I’m back to bleeding the brakes until I get it sorted, as Simon says.
I want to thank those who responded, Jonathan, tuga, Fred, Dapinky, it is much appreciated by guys like myself, who are weekend mechanics at best.
PS: I found your YouTube channel tuga, great work

Cheers
Carl

[lotustonybassplayer]

Just to add I had a severe pull to the left when braking. The culprit, rear diagonal brake due to the proportion valve being inoperative. Solution was to fit dpinky's adjustable valve mod. Which balanced the front and rear brakes.

[Tuga2112]

Just to add I had a severe pull to the left when braking. The culprit, rear diagonal brake due to the proportion valve being inoperative. Solution was to fit dpinky's adjustable valve mod. Which balanced the front and rear brakes.

thats a very good point, and a much harder one to diagnose unless you do a brake test at the MOT station.
those valves are getting old, and certainly will be catching people out of guard more often as the years go by

[carlotus]

I didn’t have time to work the m100 today, but I’m going to continue bleeding the brakes when I get time. Tony, did you change the proportioning valve yourself? If so, how difficult of a job is it.

Cheers,
Carl

[lotustonybassplayer]

Yes I did it myself Carl, pretty straightforward i can't link Dave Pink's solution. Third page of suspension and brakes board. About 3/4 down proportion valve cheap upgrade. I'm sure someone who is much cleverer can link it

[dapinky]

not necessarily clever - but I know how it's done

I have done it to 3 elans now, and other people have also done it.... no reports of any failure or other worries.

viewtopic.php?f=41&t=23606

[carlotus]

Thanks Tony.

[carlotus]

While scratching my head this morning I discovered my left rear shock is bad. Right rear shock is stiff and left rear is going up and down way too much. I remembered the previous owner telling me the rear shocks were replaced recently and they’re adjustable. I made sure they’re adjusted similarly. I wonder if this could be causing my car to turn left under heavy braking

Again, I appreciate all the feedback

Carl

[Tuga2112]

While scratching my head this morning I discovered my left rear shock is bad. Right rear shock is stiff and left rear is going up and down way too much. I remembered the previous owner telling me the rear shocks were replaced recently and they’re adjustable. I made sure they’re adjusted similarly. I wonder if this could be causing my car to turn left under heavy braking

Again, I appreciate all the feedback

Carl

in theory yes, the simple solution is to set all shocks to maximum por minimum stiffness (i would suggest maximum) and retry. if the car doesnt pull you have finished your diagnostics. if it still does, you know have more work to do at the end.

as previously mentioned, the front brakes are the most common reason. onse those are ruled out with a proper inspection of their operation you can look and address rears, then the bias valves. but if you have a MOT equivlaent station nearby with the brake test rollers. i would hope paying them to do a quick test would be more time and energy efficient than jacking the car up multiple times to check every corner.

im saying that, but if it was me. i would just lift the whole car, take all calipers out and rebuild them all. set everything back and make time for a long bleeding session (remember the rear calipers need unbolting and tilting to bleed correctly and the handbrake adjustment is another faff) while its wheels are out, put all shocks on maximum stiffness to be sure everything is at (in theory) same point.

for you its going to be very easy to source all the bits to rebuild the rear calipers. and as far as the fronts. the sliders are from the pontial lemans but the piston itselt is not the same. you will need to get the larger bore piston (52mm) seals which i havent found out which car from the rockauto list will provide them. if you can find that we would all REALLY appreciate the knowledge. because at the moment the cheapest means to rebuild fronts in the UK is a bit silly priced when the only part missing is the piston seal (which i havent been able to source cheaply despite contacting 5 different companies

[carlotus]

If I come across 52mm piston seals I’ll surely let you know

What I’ve done so far
1. Check caliper pistons, they compressing and receding as they should
2. Lubed slider pins
3. Took temp of front calipers after heavy breaking with infrared laser thermometer, temps were similar
4. Set rear shocks to same height and stiffness
5. Bled all 4 corners, bled again, and then some more.

The next steps I plan on taking
6. 4 wheel alignment
7. Replace the proportioning valves

[Simon_P]

in theory yes, the simple solution is to set all shocks to maximum por minimum stiffness (i would suggest maximum) and retry. if the car doesn't pull you have finished your diagnostics. if it still does, you know have more work to do at the end.

what is the theory Jaoa?

Braking effort surely simplifies to the amount of friction applied at the brakes being applied to the tyre/road if you don't skid where is the imbalance coming from?

Duel circuit brakes
Suspension geometry
Tyres