Torque and wheel size of a car

In summary, changing the wheel size of a car from 25 inches to 24 inches will not affect the amount of torque at the wheel. However, there will be changes at the contact patch and the RPM of the car. The formula for torque is F=T/r, and the circumference of the wheel will also change. When considering changing tire dimensions, assume it is constant and the tractive force will increase. The tractive effort is calculated by dividing torque by the tire radius. With a constant torque of 100 Nm, the tractive effort will increase from 314N to 328.08N when using a 24-inch diameter tire, which can aid in climbing gradients.
  • #1
Nick666
168
7
So let's assume I have 100 Nm at the wheel of a car, with a wheel size of 25 in diameter

If I put wheels that are 24 in diameter, so 4% smaller, what exactly will change ? Will I have 4% more torque ?
 
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  • #2
Waaat.

You'll have exactly the same amount of torque. Something will change at the contact patch through.
 
  • #3
Isnt there some formula that might be applied here ? ... F = T*r ? Doesnt a change in wheel size of a car act like a gear change ?
 
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  • #4
Ohhh...its F=T/r ... I get it now.
 
  • #5
If F is the ground force on the wheel then T- F.r = IG
 
  • #6
Also your rpm changes. The circumference (pi*D) is less on the smaller diameter.
 
  • #7
no you won't have more torque .. torque is a function of gear ratios at wheel torque = engine torque*gear ratios*differential ratio
So when you are considering change in tyre dimensions assume it constant. so for changing wheel selection following things will occur.
in this case your tractive force will increase..
tractive effort= Torque/tyre radius (dynamic rolling radius)
say you have 100Nm of torque which is constant
now you used 25inch tyre= radius=0.3175m
so tractive effort = 100/.3175=314N

Now you used 24inch dia tyre=radius=.3048m
so tractive effort = 328.08N

so basically your tractive effort increases which can help you to climb gradients..
you can calculate percentages.
 

Related to Torque and wheel size of a car

1. What is torque in relation to a car?

Torque is the measurement of the twisting or rotational force that a car's engine produces. It is what allows the wheels to turn and the car to move forward.

2. How does wheel size affect a car's torque?

Wheel size can affect a car's torque in two ways. First, larger wheels have a larger circumference, which means they cover more ground with each rotation. This can decrease the car's torque, as the engine has to work harder to turn the wheels. Additionally, larger wheels are heavier, which can also decrease the car's torque.

3. Can changing the wheel size impact a car's performance?

Yes, changing the wheel size can impact a car's performance. As mentioned before, larger wheels can decrease the car's torque and make it feel less powerful. On the other hand, smaller wheels may increase torque but can also affect the car's handling and stability.

4. How does torque affect a car's acceleration?

Torque plays a significant role in a car's acceleration. The higher the torque, the faster the car can accelerate. This is because torque is responsible for rotating the wheels and propelling the car forward.

5. Is there an ideal wheel size for maximizing torque?

There is no one-size-fits-all answer to this question. The ideal wheel size for maximizing torque depends on various factors, such as the car's engine power, weight, and intended use. It is best to consult with a mechanic or do thorough research to determine the best wheel size for a specific car model.

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