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Size tyres

valen46

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Hi, I´m thinking about change the size of both tyres from my NC750X for winning some off road capabilities. It would be 130/80 17 front, 150/70 17 rear. Anybody knows if I will have problems with the traction control or with DCT? Thanks.
 
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Can't change sizes on DCT without DCT acting up and throwing off shifting, or getting hung in gear refusing to shift (as per reporst from other DCT owners who have tried it). If you have a DCT I'd recommend sticking with as close to oem sizing as possible.
 
[QUOTE = "TacomaJD, publicación: 227394, miembro: 7350"]
No se puede cambiar de tamaño en DCT sin que DCT actúe y se deshaga de los cambios, o que se cuelgue de la marcha y se niegue a cambiar (según el informe de otros propietarios de DCT que lo han probado). Si tiene un DCT, le recomiendo que se quede con el tamaño más cercano al OEM.
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Thanks for your answer, do you know where is the post that talk about this? I cant understand why the size of tyres affects to the DCT. I think the speed sensor that DCT uses is in the engine and not in the wheels. Anyway you can reset the DCT after the change.
 
Thanks for your answer, do you know where is the post that talk about this? I cant understand why the size of tyres affects to the DCT. I think the speed sensor that DCT uses is in the engine and not in the wheels. Anyway you can reset the DCT after the change.
The DCT uses, among other sensors, the wheel rotation sensor at the front wheel. It is one of the inputs to the PCM. An example is that if you lift the rear wheel off the ground and attempt to “accelerate”, the DCT will never shift past 1st gear because it does not sense front wheel rotation.

The DCT has some tolerance for tire size changes. Owners wanting different tire sizes are free to explore how large that tolerance is before the DCT begins to misbehave.

The procedure commonly called a DCT reset is just a clutch engagement calibration that is to be done when the clutch pack is replaced. The “reset” does not change gear shifting programming or account for tire size changes.
 
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It doesn't matter where a speed sensor is located, a change in tire size affects final gear ratio and a speed sensor relies on this input. When the input is changed, the speed sensor can either keep working but won't be calibrated correctly for the altered size, or it would just detect an error as 670cc mentioned above and refuse to shift.

All you've gotta do is google search "DCT TIRE SIZE CHANGE FORUM" and go through search results. There is obviously a tolerance that the DCT can compensate for because there is a several mm difference in diameter of a new tire and a worn out tire....but a whole different change in size, especially if the change is disproportional like a tire that is 1" taller in front than oem and a rear tire that is only .5" taller, would likely make the problem worse to where it just refuses to shift.

Believe me, I wish I could run a 180/55/17 tire on the rear and change sprocket gearing on both of my DCT bikes.....but alas, I can't.
 
There exists a committee of sensors that gather info for the computer that makes the DCT decisions. Smaller or larger wheel diameters or sprockets change the relationship of reported road speed, wheel speeds, and transmission shaft rotation speed. Two transmission main shaft rotation speed sensors IIRC, the countershaft speed sensor and the two wheel speed sensors. There is some tolerance to changing tire sizes but exceed the tolerance and it no workee.
 
Hi and sorry for the refloat but I have found new info about this topic. I have seen in youtube that a user called Michael Duncan changed the syze of the rear tyre fron his NC750X to 150/70, this is 2.9% higher than original , without any problem operating DCT. The original diameter ratio between both tyres is the front one 96,15% less then rear, and with 150/70 the ratio is 93.44% less. Knowing this we can think that with 130/80 front and 140/80 rear (97.56%) thd DCT would operate well. What do you think?
EDIT: I have seen that 140/80 isn't valid for our rim, so it must be 150/70 with a ratio front/rear of 99.68%
 
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