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RedDevil · 08-31-2021, 05:09 AM

Winter tires have softer rubber and cut-up notches, so they will stay in contact with the road when temperatures are below freezing and conventional tire rubber becomes too hard to deform to match the road surface.

All season tires are better in the rain, but true winter tires will still have adequate grip.
In snow or on sheet ice grip levels drop enormously, and then the winter tires perform way better.
Even though my winter tires are not optimal 99% of the time, they still allow me to drive my car in a normal way, and when the cold sets in they won't leave me stranded.

As for speed bumps my point is that a speed bump, having slopes, increases the surface of the road over a certain horizontal distance so the wheels that go over the bump rotate faster than the wheels that do not.

If the diff between the front and rear axle is open (in a 4WD) then the wheels on the bump will resist going over the bump less than they would do in a 2WD, as the revs in the engine only rise half as fast. The torque on the drive shafts will increase somewhat, but as the diff is open so does the torque on the wheels on the flat, so, whatever resistance the wheels meet on the bump is countered by extra forward force on the other axle. Very smooth indeed.

If the diff is locked all wheels keep turning at the same speed; the wheels on the bump do cover a greater distance however, so there will be some friction then and the car will slow down a bit as energy gets wasted.

Come to think of it, I've noticed some very weird behavior in 4WD cars taking tight turns like crab-like movements, snap understeer or oversteer even at low speeds.
I believe in those cases the central diff locked up; as the front wheels travel a greater distance through the turn, the wheels will rub and once slipping will not regain grip easily. Add ABS not getting what is happening and doing something odd and the mess is complete. I saw one WRX slide sideways to the berm while moving slowly with no revving, leaving everyone perplexed.
The road may have been moist but definitely wasn't slippery.

08-31-2021, 05:09 AM	#873 (permalink)
RedDevil Master EcoWalker Join Date: Dec 2012 Location: Nieuwegein, the Netherlands Posts: 3,998 Red Devil - '11 Honda Insight Elegance Team Honda 90 day: 49.01 mpg (US) Thanks: 1,711 Thanked 2,245 Times in 1,454 Posts	Winter tires have softer rubber and cut-up notches, so they will stay in contact with the road when temperatures are below freezing and conventional tire rubber becomes too hard to deform to match the road surface. All season tires are better in the rain, but true winter tires will still have adequate grip. In snow or on sheet ice grip levels drop enormously, and then the winter tires perform way better. Even though my winter tires are not optimal 99% of the time, they still allow me to drive my car in a normal way, and when the cold sets in they won't leave me stranded. As for speed bumps my point is that a speed bump, having slopes, increases the surface of the road over a certain horizontal distance so the wheels that go over the bump rotate faster than the wheels that do not. If the diff between the front and rear axle is open (in a 4WD) then the wheels on the bump will resist going over the bump less than they would do in a 2WD, as the revs in the engine only rise half as fast. The torque on the drive shafts will increase somewhat, but as the diff is open so does the torque on the wheels on the flat, so, whatever resistance the wheels meet on the bump is countered by extra forward force on the other axle. Very smooth indeed. If the diff is locked all wheels keep turning at the same speed; the wheels on the bump do cover a greater distance however, so there will be some friction then and the car will slow down a bit as energy gets wasted. Come to think of it, I've noticed some very weird behavior in 4WD cars taking tight turns like crab-like movements, snap understeer or oversteer even at low speeds. I believe in those cases the central diff locked up; as the front wheels travel a greater distance through the turn, the wheels will rub and once slipping will not regain grip easily. Add ABS not getting what is happening and doing something odd and the mess is complete. I saw one WRX slide sideways to the berm while moving slowly with no revving, leaving everyone perplexed. The road may have been moist but definitely wasn't slippery. __________________ 2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut. lifetime FE over 0.2 Gmeter or 0.13 Mmile. For confirmation go to people just like you. For education go to people unlike yourself. Last edited by RedDevil; 08-31-2021 at 05:17 AM..