Tuesday, February 13, 2018

Modding a Scion IQ? RIMS & TIRES

Stock from factory: 

wheel spacers/converters
Steel 16" rims
5" wide
4 lug pattern
4x100 spacing
weight: 38.5lbs with stock 175/60R16 tire
Tire height: 24.26”



The ranges of possible values for tires and rims for a Scion iQ 2013 

Tires for Scion iQ 2013

Diameters: 15.0'' - 17.0''

Width (mm): 175 - 205

Tire aspect ratio (%): 45 - 65

Smallest tire size: 175/65R15

Largest tire size: 205/45R17

Rims for Scion iQ 2013

Bolt pattern 4x100

Diameter: 15.0'' - 17.0'';  

Width (inches): 5 - 6.5;  

Offset (mm): 38 - 45.

If you are wanting to reduce the weight of your iQ wheels significantly, you'll most likely have to move to 14 or 15" rims with a 185/70/14 bigger tire for instance. Just make sure the tire height/diameter is still close or your odometer and fuel economy will skew. Your turning radius was significantly reduced as well. Not to mention that it’s much easier to bend rims because of the short wheel base.

You could move to 17" rims and smaller tires, but your curb weight is likely to increase and thinner walled tires are not recommended on the iQ.

You can also convert your rims from a 4 lug pattern to a 5 lug pattern with spacers. (Spacers do add weight though)

Spacers are two piece conversion wheel adapters that are used to convert a 4 lug nut wheel with 100mm bolt pattern to fit wheels with a 5 lug 4.5" (114.3mm) bolt pattern. They will also space out your wheels for 1.75-inch to help you get enough clearance for wider tires and rims.

A size 175/60 R14 tire weighs between 13 lbs and 14.5 lbs. 

A size 185/70 R15 tire weighs between 16.5 lbs and 18 lbs

A 16” tire usually weighs between 18lbs and 22lbs.

A 17” tire usually weighs between 20lbs and 24lbs.

1) Tires should be the same diameter, but can be different widths - often vehicles will have wider tires on the rear axle.

2) Having a different diameter than factory will throw off your speedometer calibration, as this is dependent on rpm count of one of the wheel hubs.

3) Larger is generally better as a rule of thumb, within normal limits. Larger diameter = less revolutions of the wheel to cover a given distance OR cover same distance faster. Wider = more traction, but too wide can result in interference, especially with steering set wheels.

It is technically illegal to resell your car if you know the odometer and speedometer are incorrect.

You must put on your title that your car exceeds its mechanical limits.

The math showing just 1” in tire size difference is as follows:

 4 miles per 100 if you are just 1” off. 

1” under and you’re traveling 104 miles on odometer reading but really only going 100 miles. 96 miles per 100 the opposite direction.

If you’re wheels are more than 5 pounds heavier than the stock 38.5lbs you’re adding significant stress on the engine. 

The iQ is a CVT (continuously variable transmission) so extra weight is a killer to the transmission.

The lightest weight wheels I've found are made by Konig - called Helium. I ended up purchasing 4x100 lug pattern, 15” diameter, 6.5”width,  10.55lb per rim, wheels for $320 shipped. This reduced the total weight, after adding a tire by 26 pounds per axle. My acceleration truly is better and it appears as if I have gained 1-2 miles more per gallon. My tire height is the exact same as the stock 16” rims (24.27”) using 195/60/15  tires.

I used Bridgestone Ecopia Mileage Plus 70,000 mile tires.

I found this page particularly helpful in deciding what I wanted to do and achieve:


I will continue to update this post over time as I discover and learn more about this topic.

I am currently investigating speedometer and odometer calibration in regards to changing tires and rim sizes.

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