Re: Opony...
: 26 paź 2010, 14:40
Kurde, nie wiem czy to pod OT lekko nie podchodzi:
"I agree that 3% is probably not an issue, but there is a way that it can effect the DSC that is not obvious.
If the tires are a different diameter than original, the speed input to the system will be off by some amount.
The DSC system has many other inputs including steering position and lateral G.
You can calculate lateral G's using an equation that includes wheel speed and the diameter of the circle driven (substitute steering position for diameter in this case).
The system compares calculated Gs to measured Gs (and yaw rate) to determine if the car is sliding and if it needs to do something about it.
See where this might be an issue?
The DSC may take action too soon or to late depending on the speed error from the tires. I doubt you'll ever see any issues (except maybe a warning light) until you are in a situation where DSC is doing something.
That situation would be at the beginning of a slide.
If the system is supposed to help, I wouldn't want it making decisions based on inaccurate data.
ABS won't really care, but DSC will.
I'm not talking about a difference in wheel speed, ABS looks at that. It may use a calculated average of 2 or 4 wheel speeds as the speed input to the DSC though.
I'm talking about how the car determines if it is going where you want it to. It compares your intended path to your actual path, and determines if the car has lost traction.
The intended path is calculated from the steering position and your actual speed over ground, in MPH.
The actual path is measured using lateral Gs.
For example,
Lets say if the steering position is 20 degrees the car will drive in a circle with the diameter of 200 ft.
If you are traveling 35 MPH (actual speed ) in a 200 ft circle you will experience 0.82 lateral Gs.
If you are traveling 38 MPH (actual speed) in the same circle you will see 0.96 Gs.
If you change to smaller tires, the speedo will read higher than actual speed. Lets say the new tires indicate 38 MPH when actual speed is 35 MPH.
Now drive the skidpad at 38 MPH indicated. The car expects to see 0.96 Gs on the accelerometer with 20 degrees of steering at 38 MPH.
The car measures 0.82 Gs on the accelerometer because you are really only going 35 MPH.
The comparison of your intended path (0.96 Gs) and actual path (0.82 Gs) may cause the DSC to conclude you are sliding, and take action, whatever that may be.
I tried not to show too much math, as that makes it harder to read. There is another layer deeper into this that I am not going into to try any keep this simple and to the point. It involves the rotation of the car as compared to direction of travel. Its more math and really only helps refine the same answer as seen above.
What this really means is if you stray from the original tire size, you may have problems, but there is no way to know for sure until you try it. This is not as simple as keep all 4 tires the same size as each other.
Hope this helps."
A co do T1-R - na początku wyraźnie czułem jak kładzie się w szybkich zakrętach, ale po zwiększeniu ciśnienia o jakieś 0.3b jest lepiej.
Znika średnio-szybko (coś za coś), na suchym jest spoko (można wyczuć, że zaraz straci przyczepność) na wodzie już gorzej. W porównaniu do ori runflatów (Eufori@ - ktoś ma poczucie humoru, raczej żałoba) i tak są nieporównywalnie lepsze.
IMO są lepsze opony do kupienia - aktualnie pomyślałbym nad RE50A.
"I agree that 3% is probably not an issue, but there is a way that it can effect the DSC that is not obvious.
If the tires are a different diameter than original, the speed input to the system will be off by some amount.
The DSC system has many other inputs including steering position and lateral G.
You can calculate lateral G's using an equation that includes wheel speed and the diameter of the circle driven (substitute steering position for diameter in this case).
The system compares calculated Gs to measured Gs (and yaw rate) to determine if the car is sliding and if it needs to do something about it.
See where this might be an issue?
The DSC may take action too soon or to late depending on the speed error from the tires. I doubt you'll ever see any issues (except maybe a warning light) until you are in a situation where DSC is doing something.
That situation would be at the beginning of a slide.
If the system is supposed to help, I wouldn't want it making decisions based on inaccurate data.
ABS won't really care, but DSC will.
I'm not talking about a difference in wheel speed, ABS looks at that. It may use a calculated average of 2 or 4 wheel speeds as the speed input to the DSC though.
I'm talking about how the car determines if it is going where you want it to. It compares your intended path to your actual path, and determines if the car has lost traction.
The intended path is calculated from the steering position and your actual speed over ground, in MPH.
The actual path is measured using lateral Gs.
For example,
Lets say if the steering position is 20 degrees the car will drive in a circle with the diameter of 200 ft.
If you are traveling 35 MPH (actual speed ) in a 200 ft circle you will experience 0.82 lateral Gs.
If you are traveling 38 MPH (actual speed) in the same circle you will see 0.96 Gs.
If you change to smaller tires, the speedo will read higher than actual speed. Lets say the new tires indicate 38 MPH when actual speed is 35 MPH.
Now drive the skidpad at 38 MPH indicated. The car expects to see 0.96 Gs on the accelerometer with 20 degrees of steering at 38 MPH.
The car measures 0.82 Gs on the accelerometer because you are really only going 35 MPH.
The comparison of your intended path (0.96 Gs) and actual path (0.82 Gs) may cause the DSC to conclude you are sliding, and take action, whatever that may be.
I tried not to show too much math, as that makes it harder to read. There is another layer deeper into this that I am not going into to try any keep this simple and to the point. It involves the rotation of the car as compared to direction of travel. Its more math and really only helps refine the same answer as seen above.
What this really means is if you stray from the original tire size, you may have problems, but there is no way to know for sure until you try it. This is not as simple as keep all 4 tires the same size as each other.
Hope this helps."
A co do T1-R - na początku wyraźnie czułem jak kładzie się w szybkich zakrętach, ale po zwiększeniu ciśnienia o jakieś 0.3b jest lepiej.
Znika średnio-szybko (coś za coś), na suchym jest spoko (można wyczuć, że zaraz straci przyczepność) na wodzie już gorzej. W porównaniu do ori runflatów (Eufori@ - ktoś ma poczucie humoru, raczej żałoba) i tak są nieporównywalnie lepsze.
IMO są lepsze opony do kupienia - aktualnie pomyślałbym nad RE50A.
DZIĘKUJE za info! +1
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