Do bigger wheels make a car stronger?

[Aalim]

Hi Guys!

I have question about why people always seem to fit bigger wheels to cars they modify. Is it to make the car stronger or more powerful?

By stronger I mean that can the car now pull heavier loads than it could before it had bigger diameter wheels? Can anyone answer this for me?

[cyborg]

Well not stronger but more capable in case of 4x4 and proper off-road SUV. Bigger tire gives better flotation for sand driving and also lift the car body by few cms which makes them less prone to stuck and dig-in easily.

In cars (sedan), people fitting bigger tires I think it's only for looks. May be someone here will add more valid reason for this as well.

Car pulling power depends on engine and any additional engine modification will make it stronger or capable and not just tire upgrade. Actually it backfires more on power if you install bigger tire, car will be less capable if no engine modification is done.

[amid]

I heard ppl saying bigger wheels help in giving better fuel mileage, as axle diameter is same so sticking a bigger diameter wheel on same axel size will help vehicle cover more miles in same fuel.

[treks]

HI Aalim,

As @cyborg points out, bigger wheels will give you a bit of extra ground clearance, but that is it.

Fitting bigger wheels does not make a car stronger, or give it more pulling power. In fact, there is no relationship between wheel diameter and torque, since wheels are driven from their centres, meaning that the definition of torque, "Force Multiplied By Distance", does not apply.

However, the diameter of the driving wheels is only one factor in the equation that determines how fast a car moves at any given engine speed in a given gear. Therefore, if a car moves at speed X at 2000 RPM in first gear, the road speed and RPM will both change if the driving wheels are bigger than standard. This is because a bigger wheel covers a greater distance in one rotation than the standard wheels do.

Since the bigger wheels cover more ground than the standard wheels, the engine does not have to run at 2000 RPM in first gear to propel the car at speed "X". In practice, this means that if a cars' most economical speed was say, 120km/h at 3000 RPM in fifth gear with standard wheels, bigger wheels (depending on the size difference) can make the engine run at say, 2700 RPM to maintain 120 km/h.

In some cases this is good, since it uses less fuel, but if the wheels are much larger, and especially on smaller cars, it could mean that the engine is running below its maximum torque in  any given gear, which is bad, because the final gearing may have  changed to the point where bigger throttle openings than normal may be required to overcome the effects of the changed gearing.

Changing to slightly bigger wheels is usually not much of a problem, but changing too much larger wheels can have all sorts problems, including making a car use more fuel than before,  and causing shifting issues on automatics, since the engine speed now no longer matches the road speed in any given gear- which is one of the conditions that has to be met before a transmission will shift.

Finally, the only reason big trucks use big wheels is because big wheels are designed to carry the weight of the truck and its load. The final pulling power of a vehicle is determined by the engine and gearing in the transmission and differential(s), and has nothing to do with the size of the wheels.       

Edited July 7, 2016 by treks
word replacement

[Barry]

Fitting bigger rims on a passenger car means you can fit low profile tyres without changing the size of the rolling circumference of the wheel. Low profile tyres means you have less flex in the sidewall which has the effect of making the steering more direct thus improving handling. However, because there is less flex, you can lose grip  and spin out more easily when cornering. Not always a problem if you're into drifting. 

 

I like things with big wheels. The wheels on this monster truck originally came from the LeTorneau electric land train. Something interesting to read about if you have half an hour to kill.

http://blog.hemmings.com/index.php/2009/11/19/54-wheel-drive-the-letourneau-electric-arctic-land-trains-that-put-australian-road-trains-to-shame/

 

 

Edited July 10, 2016 by Technician
Added link

[salmanahmed]

On 7/6/2016 at 7:45 PM, amid said:

I heard ppl saying bigger wheels help in giving better fuel mileage, as axle diameter is same so sticking a bigger diameter wheel on same axel size will help vehicle cover more miles in same fuel.

that is true, a wheel which has a larger diameter than stock wheels will improve in getting better milage. But! you will be trading better milage for a price too heavy as larger wheels add a lot of strain on the clutch and gear box. in fact, gear sleeve can worn out well before time. Then your car's breaking system gets affected as its disks are designed to handle smaller wheels. And finally, the ABS can malfunction as it too is design on the calculation based on wheel diameter, tyre's surface area touching the road amongst other things. Going up by a small margin is something which might not damage your car too early but if you increase the wheel size too much them you are asking for trouble.

[amid]

Thanks buddy, for answering it very nicely with required cause and affect. Though I don't intend to but now I will be more careful in not to upgrade even while changing the tires, as sometime vendor recommend bigger tires as they dont have exact OEM option, so now I know my answer to such suggestive selling.