A longer version is posted over
here, with more plots and stuff
Does the soft compound, thick tread blocks, and high number of deep sipes used in a snow/ice tire affect how much torque/power a roller chassis dyno would measure?
Yes. Winter tires lower the power output as measured by the dyno. The key being power being measured by the dyno. The engine, in both cases, is generating the same power.
The tires used in this comparison are from the opposite ends of the spectrum; one is designed for ice and snow while the other is for Tarmac. From the pictures below, one could imagine the difference in tread deformation when the tire is stressed. In relation to the test results, I would expect winter tires that uses shorter blocks and fewer sipes to experience less loss than the WS-70 and All-Season tires will likely have more loss than the RE-01R.
The Tires:Some information test setup: - Chassis dyno used in the test is a Dyno Dynamics 450DS AWD unit.
- Vehicle used is a 2006 Subaru WRX with catted Turbo Back Exhaust (TBE)
- Tires used are Bridgestone Blizzak WS-70 (New, 215/45/17) and RE-01R (~50%, 225/45/17)
- Tires are mounted on stock 06 WRX 17" alloys inflated to 45psi
Brief description of test sequence: - Wheels with RE-01R tires are installed onto test vehicle and loaded onto dyno
- Engine is warmed up and car is driven on the rollers to warm up tires and drive train components
- Engine RPM to achieve 40mph (dyno roller speed) in 3rd gear is recorded
- 3rd gear pulls are done starting from ~2000rpm up to >6000rpm
- Car is unloaded from dyno and wheels with Blizzak WS-70 tires are installed
- Car is reloaded onto dyno, repeating the warm up procedure above
- Engine RPM to achieve 40mph (dyno roller speed) in 3rd gear is recorded
- 3rd gear pulls are repeated
Results:Power and Torque
2nd set of resultsAurora W403 tires (non studded) has few sipes and tread compound feels harder as well.
Reduction in power but not as much as the softer WS-70