Possible solution to the TC issues under slippery conditions

Hi guys,
I've been reading about some Traction Control issues on the gen II Prii under particularly slippery conditions, such as cars refusing to climb a slope because of overly cautious TC, which does not allow for even the slightest wheelspin. We know that gen III's TC have been altered and allows for a little spin, making the things better. A very simple solution just occured to me and I would like to know your opinions.

I propose to fit a slightly larger diameter wheels on the front axis; say 16" to the front and 15" to the rear of the car. The TC works so that it computes the difference between RPM of the front (powered) and rear (unpowered) wheels, and when the powered wheels rev more than the unpowered ones it detects a spin and kicks in. With larger diameter wheels on the front, the rear wheels would rev a little faster under normal conditions, and therefore the TC would allow for a little wheelspin on the front, just as the gen III does now.

Unfortunatelly, I don't have 15" wheels at my disposal, as my Pri wears 16", and I don't have a chance to borrow them for the experiment either (not to mention that there is currently no snow around ). Would anybody be interested in doing a little evaluation and sharing the results with the rest of us? And what are your opinions in general?

BTW, you may argue that if the car refuses to move *at all*, the revs of the rear wheels would be zero, and therefore *anything* - 0 gives positive result (and therefore detection of a spin). But I don't believe that the TC really does not allow for *any* wheelspin at all, as the car would then barely move even under ideal grip conditions. Therefore, I believe that even in that case this solution would enable a *slightly* larger wheelspin than before.

 

The speedo/MPG readings should be unaffected, as those are computed using the front wheels, which would be unchanged. What I proposed was to fit slightly smaller rear wheels.

Well, my good Pri is pretty cautious, as I saw today on some wet stone pavement trying to accelerate up the hill from a standstill... Made me a little worried about some winter mountain driving actually. And yes, I have bought good winter tires today .

EDITED: Sorry, I just re-read my original post and saw that I actually *did* write about fitting larger front wheels and not smaller rears - my mistake, I formulated it badly .

 

Well, I didn't realize that the diameter of the wheel is not correlated to the rim size - you are right in that point, thanks for noting. Actually, I proposed to leave the front wheels alone (as I already have 16" as the car came from the factory), but to fit slightly *smaller* rears. The rears have to be smaller diameter than the front wheels, not the other way round, or it would actually make things worse .

 

Hi Tom,
you are right that my proposal would not make any difference at stillstand. I am aware that this is a major deficiency. Well, if you could fit slightly *larger* front wheels, than you would get slightly higher circumferential speed of the tire, which would make some difference. But larger front wheels probably won't fit in there and would affect speedo/mpg readigs, as Nefer stated...

OK, I think we may write my little proposal off as infeasible . Thanks for your answers!

 

Is it possible to turn the TC off? I didn't know that. How do you do it, would you explain the procedure please?

Yes, I was also thinking about messin' around the signals leading to the ECU, but this idea occured to me as a possible simple solution.

 

Yes, I just bought snow tires today and will put them on tomorrow . I am used to do that every winter with all cars I've ever had. This was never meant as a substitute for appropriate tires.