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Anybody locked a wheel when braking?
#1

I haven't - but I've seen my car do it. In practice for the 8 hour race one of my co-drivers locked the lighter loaded inside front wheel for about 40 feet. It happened coming to the right hander which is the last corner at Portland. It didn't look unusual because a lot of cars will lock up there. But I just kinda looked in disbelief as I knew my car had ABS and I know it works. It just happened once with no other side effects and we can't quite figure it out. Best I can guess is that since it is not a racing ABS system, it was momentarily confused. Anybody else had this happen?



Eric
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#2

Is it possible that the tire was so lightly loaded that there wasn't enough traction to turn it? I've seen lots of cars lift their inside front tire completely off of the groud.
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#3

I think the tire probably had enough traction - it left a nice white cloud of tire smoke for everyone to see. But luckily there was no flat spot. It was just odd to see it smoke the one wheel.



Eric
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#4

Weird......I guess it's possible that the system was confused since only the one tire was locking up
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#5

I have locked both of my front tires!! The ABS-sensor on my left rear wheel faild. I ended up off the track <img src="/forum/images/smilies/968/rolleyes.gif" class="smilie" alt="" />



[Image: gallery_149_27_63909.jpg]



[Image: gallery_149_27_39628.jpg]



/Björn
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#6

I've locked up a front wheel before on the street. How do I test a abs sensor?
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#7

Which brings me to this question... what are the likely failure points in the ABS system?



Since the car has become a metal-on-metal, high-spring-rate club racer it seems to trip the ABS light on the dash with increasing frequency. Started at Road America with forays across the rumble strips in T5 and T8. Now, it will even happen from time-to-time on the street with no apparent sharp jolts.



I did check the tightness of the sensors at each wheel during recent brake upgrade. I should have reached back to the relays on the ABS hydraulic unit when I had the wheel liner out to see if either of them had become unseated. Is this the likely culprit?



Other things to check?



Thanks in advance.
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#8

Quote:How do I test a abs sensor?


The ABS light will come on if the sensor fails. At least it should. I have had mine come on after a rear sensor was chewed up when a axle nut backed off.



Quote:Other things to check?


I sounds like an intermittent electrical short. Check the connectors where the sensor wire joins the harness. The connections are in those round plastic cylinders. I would also check the connector to the ABS computer. The ABS computer may have an internal short, so you could try borrowing someone else's computer to see if the issue goes away. One of the sensors could also be giving up.



Eric
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#9

Thanks Eric. Do the sensors give up over time (intermittently)?



I've also heard that many 944/951/968 guys install an ABS reset switch due to the "chronic" nature of the problem...
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#10

i want to know how evo happened to have a camera on him at that precise moment
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#11

[quote name='flash' date='Nov 26 2005, 02:33 AM']i want to know how evo happened to have a camera on him at that precise moment

[right][post="12809"]<{POST_SNAPBACK}>[/post][/right][/quote]



<img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />



After this I had to buy 2 new front tires and a new ABS-sensor <img src="/forum/images/smilies/968/mad.gif" class="smilie" alt="" />



/Björn
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#12

That Armco looks just like the stuff from Watkins Glen!



Jason
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#13

I flat spotted a front inner tire at Watkins Glen this year in a practice session. Turning up into the "TOE", and braking-I believe that the front tire was on the curbing/relatively unloaded-must have scuffed across the top of the curb. Immediately had a bad vibration. The Hoosier guys confirmed the flat spot with the wheel/tire on the balancer later in the day. My ABS system continues to work well-before and since.

Gary
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