Does anyone know how TCS system calculates wheel speed differences from front to rear and more importantly what level is defined as slip? I have brand new tires up front that are 12 mm larger than the rear and at higher speeds it thinks there is slip. If I calculated it right, there's a 5% difference in diameter and consequently speed. Anyway to let system know what's going on or do I just need exactly the same diameter tires.
thanks
Traction Control
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driverdriver
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kentpsmith
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Re: (driverdriver)
Wow, how did I forget that.......................97 Q45.
Re: (kentpsmith)
The traction control is not sensitive to the front wheel speeds for at least up until a 1996 Q45 and I do believe this to be true also for your Q. Traction or lack there of is generally determined by comparing the speed of the driveshaft rotation versus the rear wheel abs/traction sensors so the front wheels have no input in traction control activation equation. At least this is how it works on my 95 Q45. Speed sensor is also determined from the transmission speedo gear that calculates off driveshaft rotation. The ABS is definitely senstive to changes in both tire diameter and rotational mass.
Post more information such as actual tire size for front versus back and then maybe you get more help.
Post more information such as actual tire size for front versus back and then maybe you get more help.
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kentpsmith
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Re: Traction Control (rsiwicki)
Sorry for the lack of details earlier but I was just trying to get some background info on how the TCS works without having someone have to go through an in-depth troubleshoot. Here's the whole story. After replacing the stock 215/60-16 tires up front with 225/60-16 the slip light will come on at speeds maybe above 45 mph with moderate throttle. Obivously the TCS begins doing it's thing to reduce the"slip". I am positve this is directly related to my tire size issue it happened immediatly after changing them. I am assuming that the traction control compares wheel speeds of front and rear and at some percentage difference begins to do somehting about it. It's not a huge deal since I will eventually get the larger tires on the rear also but I'd like to get some more miles out of what I have now. I am trying to find out if there is anything built into the system to allow for different diameters in front and rear. There has to be some acceptable margin before it triggers the TCS. The difference in the tire diameters is 4.6%. Apparently this is enough.
Thanks
Thanks
Re: Traction Control (kentpsmith)
Your comparison of (225/215-1)*100= 4.6% is not correct. You need to compare tire diameters. The new size you are running 225/60/16 = 26.7" diameter while the 215/60/16 = 26.2" diameter for a difference of (26.7/26.2-1)*100=1.9%.
Now this is why we need the details.
Regardless, the difference in size is not enough to trigger anything. You have something else wrong with your car that happened simutaneously with the new tires being installed causing the TCS error.
Now this is why we need the details.
Regardless, the difference in size is not enough to trigger anything. You have something else wrong with your car that happened simutaneously with the new tires being installed causing the TCS error.
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kentpsmith
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Re: Traction Control (rsiwicki)
No, this is why I left out the details in the first place. I don't need a lesson in tire diameter calculation. (Although, I obviously can't do it right myself) I was trying to learn how the TCS works. I don't mind troubleshooting it myself. Just lookin' for some background on TCS..... not tires. Thanks !
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SpecDRacing
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Re: Traction Control (kentpsmith)
I'll give this a shot. LOL Ok, TCS is a complicated system on the infinitis as it has changed almost every 3 years with infiniti and has seen many different versions depending on what year your car is and what model.
TCS works be seeing a differentiation in rotational speeds from several different locations. The ABS system can also input speed signals to the TCS system. Depending on what signals it sees and from what components. These signals are frequencies, using rings that look like gears located either on the differential at the input or output flanges, on the axles at the hubs, inside the differential and/or transmission and also the ring gear of the engine (also used for ignition timing and engine related components). All those signals are then processed and from that, slip is determined. Heres the clinch, slip is only determined when the computer sees that the signals recieved are failing to stay within set perameters predetermined by the programming (newer cars have whats called unified meters, which is the gauge pod on the dash, it houses the control unit now, along with VDC and ABS). Anyway, those sesnors can easily misrepresent reality, causing incorrect information to be processed, giving you your slip light.
Some causes:
-Drastic wheel size change (not like what you have).-Failing transmission torque converter and/or clutches.-Failing TCU.-TPS out of adjustment.-Faulty wheel sensor and associated speed sensors.-Faulty TCS Control Unit.-Faulty wiring.
Depending on the situations given, most of the above causes can be ruled out. I see you didnt want an explanation of how to fix it, so I'll leave you here. Thanks. Hope this helps you.
TCS works be seeing a differentiation in rotational speeds from several different locations. The ABS system can also input speed signals to the TCS system. Depending on what signals it sees and from what components. These signals are frequencies, using rings that look like gears located either on the differential at the input or output flanges, on the axles at the hubs, inside the differential and/or transmission and also the ring gear of the engine (also used for ignition timing and engine related components). All those signals are then processed and from that, slip is determined. Heres the clinch, slip is only determined when the computer sees that the signals recieved are failing to stay within set perameters predetermined by the programming (newer cars have whats called unified meters, which is the gauge pod on the dash, it houses the control unit now, along with VDC and ABS). Anyway, those sesnors can easily misrepresent reality, causing incorrect information to be processed, giving you your slip light.
Some causes:
-Drastic wheel size change (not like what you have).-Failing transmission torque converter and/or clutches.-Failing TCU.-TPS out of adjustment.-Faulty wheel sensor and associated speed sensors.-Faulty TCS Control Unit.-Faulty wiring.
Depending on the situations given, most of the above causes can be ruled out. I see you didnt want an explanation of how to fix it, so I'll leave you here. Thanks. Hope this helps you.