Skid/Wheel hop of front wheel when hard braking just before the ABS kicks in, ??? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

steved0x · 11-06-2013, 05:12 PM

I had a weird thing happen to me tonight, I had to hit the brakes hard, and right before the ABS kicked in (first time it kicked in since I have had the car) It felt like there was a little hop/skid/squeal from on of the front tires right before the ABS kicked in. Once the abs kicked in, the hop/skip/squeal stopped.

When I got into my neighborhood, I did a quick stop from 25 mph and was able to reproduce the issue. It felt like the right front tire did a little hop/squeal and then the ABS kicked in.

Is that normal behavior? Was my right front tire locking up first, which triggered the ABS activation? And the hop was when the tire released to break out of the skid?

I tried to do some searching but I think terms like ABS and hop are too common.

Both times the car stayed perfectly straight with no tendency to pull to either side.

Does anybody know what may be the cause? Has this ever happened to them?

2000 S with 6 speed and Traction control. No lights came on the dash during the ABS activations.

Thanks!

Steve

Spinnaker · 11-06-2013, 10:03 PM

I have never experienced anyting like you described in my 2000S.
My guess would be that the damper in the front strut may be going bad.

ohhh my · 11-06-2013, 10:14 PM

A light is not suppose to come on. I would check tire pressure to make sure they are even on both side and check tire wear. Excessive tire wear can cause ABS to kick in earlier. Also older tires with harder rubber will do the same. ABS should kick in right before lock up. Sounds like everything on your system did what it's suppose to do. Keep you in a straight line and apply as much pressure with minimal tire slide. The better the rubber you have, the more grip you will have, the later ABS will kick in. You will feel a little fludder in your brake pedal when ABS kicks in, perhaps this is what you are describing as the hop/skip?

steved0x · 11-07-2013, 04:09 AM

It was fairly extreme, like running over a giant pothole just on the right front tire. It almost felt like it went airborne

there was definitely a lurch from the front right only.

The fronts have more wear than the rears, which have only 6,000 miles. I will dig and see if I can find the mileage of the fronts.

108,000 on the original M030 sport suspension so maybe time to get that updated?

Thanks for the feedback everybody.

san rensho · 11-07-2013, 06:16 AM

Same thing happens to me. Right before the abs kicks in I feel a little slide and just the slightest pull to the right, Then perfectly straight braking. No hop, however. One wheel is going to lose traction before the other for many reasons, tire adhesion, car weighting, brake efficiency so I think what you experienced is perfectly normal.

Topless · 11-07-2013, 10:01 AM

The ABS system on a Boxster is quite good and I believe in exploring it often. By design it will not engage until one wheel is moving significantly faster than the other. This requires a brief skid to engage ABS. If you are also hearing/feeling big "clunk" like you dropped into a pothole something needs attention on the front suspension or possibly the motor mount. Normal ABS engages without an unsettling clunk effect.

thstone · 11-07-2013, 11:46 AM

The tire will skid a bit and then you'll hear and feel the ABS pulse the brakes. That sound and movement might be interpreted as a "clunking" of the suspension.

ABS activation shouldn't result in a hopping wheel - if so then your shocks/suspension are probably worn.

MaxD · 11-07-2013, 03:40 PM

If you have 108K on the stock shocks, it is time to replace them. Also inspect all of the bushings for play and/or cracking, front and back. A clunking noise and hop suggest some suspension R&R is in order.

woodsman · 11-08-2013, 02:43 PM

It's also possible that the brake on that corner is grabbing for some reason. After a short drive stop and check (carefully) the brake and wheel temps by gingerly touching them. Compare side to side to determine if you've got a dragging caliper. You could also jack the corner in question up and see if the wheel rotates freely. A dragging brake can be caused by heavily corroded brake lines ( they will squeeze but not fully release), a broken pad surface or a seized caliper ( in this case a stuck piston). If it's dragging, you would PROBABLY notice a pull to that side occasionally. It's worth investigating as it could suddenly get worse and something could break.

san rensho · 11-08-2013, 05:09 PM

Quote:

Originally Posted by woodsman

It's also possible that the brake on that corner is grabbing for some reason. After a short drive stop and check (carefully) the brake and wheel temps by gingerly touching them. Compare side to side to determine if you've got a dragging caliper. You could also jack the corner in question up and see if the wheel rotates freely. A dragging brake can be caused by heavily corroded brake lines ( they will squeeze but not fully release), a broken pad surface or a seized caliper ( in this case a stuck piston). If it's dragging, you would PROBABLY notice a pull to that side occasionally. It's worth investigating as it could suddenly get worse and something could break.

The right side of a Box (or any car) is lighter than the left because the driver is in the left hand seat. So, unweigheighted right side will lose traction before the left side. Pretty simple. If the brake is dragging, usually you will notice a definite pull to one side in any braking condition, not at the edge when ABS kicks in.

woodsman · 11-10-2013, 01:57 PM

In this case I am speaking from direct experience. I know the RF will usually lock first and why but my DD recently changed and began locking prematurely and violently- with a hop feeling even. It was a stuck piston.

steved0x · 01-06-2014, 05:11 AM

To close the loop on this, I just did a front brake rotor replacement, and it resolved the issue.

Longer version: I just did some maintenance over the holiday break, and one of the things I did was replace the front rotors. They were both down to <25mm (new 28mm, replace at 26mm for 2000S). The pads had >10mm so I left them and just replaced the rotors (odd?) I went ahead and did a bedding procedure (I did about 7 or 8 60 to 15 decelerations and then drove for about 15-20 minutes and then parked without ever touching the brakes.) Later on a subsequent drive I decided to do a quick stop and activate the ABS and the issue did not re-occur. Problem solved

Steve

BYprodriver · 01-06-2014, 09:22 AM

I'm thinking the fresh brake fluid was the main thing that eliminated the issue.

steved0x · 01-06-2014, 09:29 AM

Quote:

Originally Posted by BYprodriver

I'm thinking the fresh brake fluid was the main thing that eliminated the issue.

Could be; I did have a full brake flush done (with ATE Super Blue) in Sept 2013 but the mechanic (I was short on time and had never done bleeding/flushing before so opted to have the mechanic do it) only bled the outer caliper bleed screws and he used "gravity bleeding", when I bled them this time I did both bleed screws and I got some "green" fluid (blue/amber mix maybe?) from the inner bleed screw along with a handful of very tiny bubbles...

Steve