My Yaris accelerate too slow !!! any suggestions ?? - Toyota Yaris Forums

CrankyOldMan · 08-21-2012, 07:54 AM

If you're into math/physics, here's a brief explanation of the laws that govern acceleration of rotating bodies: http://en.wikipedia.org/wiki/Moment_...ntum.2C_torque
This really boils down to an increased moment of inertia and a fixed energy source, so the angular velocity has to decrease to keep things in equilibrium.

If you're not into the actual math, here's a brief summary:

Going to a larger diameter wheel moves more of the mass away from the axis of rotation. Rotating a mass at a farther distance requires more energy to achieve the same acceleration/angular velocity. Try sitting in an office chair and spinning around while extending/retracting your arms. Now try it with your arms extended, then try with your arms extended holding some small weights.

In the case of your wheels, you've gone to a larger diameter wheel (15" to 16") that is also likely wider than stock (5.5" to 6.5"). Your tire diameter didn't change significantly (1mm smaller) but you also added 10mm of width. Even if you kept the weight (mass) of the wheels and tires the same, you would still lose acceleration and top-end speed because you (in theory) haven't increased the power available from the engine. I know you tried a few things, but the energy required to compensate may be more than you can get from bolt-on parts.

I discovered the same thing the hard way when I replaced my winter tires (175/70R14) with sticky summer tires (205/50R15). The only mathematical solution to counter this is to go with crazy lightweight tires to reduce the moment of inertia, but that's not financially do-able for me right now.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Yaris Motor Swap Thread Read before posting swap threads	Sabretooth	Performance Modifications	219	06-10-2025 03:58 PM
NEWS: TOYOTA REVEALS ALL-NEW YARIS SEDAN AT 2006 LOS ANGELES AUTO SHOW	VitzBoy	General Yaris / Vitz Discussion	7	09-20-2023 08:50 AM
Is a Yaris Really That Slow?	RacerFreakXXX	General Yaris / Vitz Discussion	68	07-02-2010 05:01 AM
2007 Yaris Pricing Info !	YarisBueller	New YARIS Purchase Forum	104	06-24-2009 05:54 PM

08-21-2012, 07:54 AM	#5
CrankyOldMan 2ZR swap. DO IT! Ask how! View User's Garage Drives: 09 Meteoric Metallic HB Join Date: Feb 2011 Location: West Michigan Posts: 2,333	If you're into math/physics, here's a brief explanation of the laws that govern acceleration of rotating bodies: http://en.wikipedia.org/wiki/Moment_...ntum.2C_torque This really boils down to an increased moment of inertia and a fixed energy source, so the angular velocity has to decrease to keep things in equilibrium. If you're not into the actual math, here's a brief summary: Going to a larger diameter wheel moves more of the mass away from the axis of rotation. Rotating a mass at a farther distance requires more energy to achieve the same acceleration/angular velocity. Try sitting in an office chair and spinning around while extending/retracting your arms. Now try it with your arms extended, then try with your arms extended holding some small weights. In the case of your wheels, you've gone to a larger diameter wheel (15" to 16") that is also likely wider than stock (5.5" to 6.5"). Your tire diameter didn't change significantly (1mm smaller) but you also added 10mm of width. Even if you kept the weight (mass) of the wheels and tires the same, you would still lose acceleration and top-end speed because you (in theory) haven't increased the power available from the engine. I know you tried a few things, but the energy required to compensate may be more than you can get from bolt-on parts. I discovered the same thing the hard way when I replaced my winter tires (175/70R14) with sticky summer tires (205/50R15). The only mathematical solution to counter this is to go with crazy lightweight tires to reduce the moment of inertia, but that's not financially do-able for me right now.