Do spacers increase fuel consumption? How about vibration?

vricardo · Post by **vricardo** » Sat Feb 03, 2007 3:28 pm

Hi, I was wondering if the use of 3/4 inch wheel spacers will increase the fuel consumption on a car. How about vibration at high speed, does anyone have experience on that?

Gary71 · Post by **Gary71** » Sat Feb 03, 2007 4:31 pm

They won't increase the fuel consumption, but unless correct for for the offset of the wheels you have they will reduce the life of your wheel bearings, and mess up the suspension characteristics!

vricardo · Post by **vricardo** » Sat Feb 03, 2007 6:47 pm

hummmm... and what would the "correct for the offset of the wheels" be? How is it calculated?

Gary71 · Post by **Gary71** » Sat Feb 03, 2007 8:13 pm

Here's an image nicked from the DDK 911 guru Andy!

The correct position for the wheel is the one originally designed by the guy at Porsche who knew what he was doing

(not me!)

If you have 6" rim with a offset of say 35mm and a 7" rim also with an offset of 35mm the centre of the tyre is in the same place relative to the mounting face, so the steering geometry will stay the same. Put a spacer on and the tyre centre will move outwards changing the steering feel and affect braking stability. Same goes for the back as if you change the tyre centre point you will change the toe in/ toe out characteristics under acceleration and braking.

Having said that there is a practical limit to how long you can keep the tyre centre at the design condition. A 11" wide RSR rim is a bit of a jump over the 6" and you won't get half of the width increase to go inboard as it would wipe the suspension out!

All tiied up · Post by **All tiied up** » Sun Feb 04, 2007 5:48 pm

The correct position for the wheel is the one originally designed by the guy at Porsche who knew what he was doing (not me!)

Having said that there is a practical limit to how long you can keep the tyre centre at the design condition. A 11" wide RSR rim is a bit of a jump over the 6" and you won't get half of the width increase to go inboard as it would wipe the suspension out!

Surely if the engineer knew what he was doing........!?!

Always try and keep to the original offset as much as possible, for all the reasons mentioned before, saftey primerilly, bearing life, brake performance, suspension / handling charachteristics and not forgetting, possible modification to the bodywork!!

What gave you the idea that it would affect the fuel consumption?

vricardo · Post by **vricardo** » Sun Feb 04, 2007 10:22 pm

My knowledge on aerodynamics is quite scarce, so it crossed my mind that the the spacers could enlarge the "volume" of the car, increasing its drag coefficient, leading to increasing the fuel consumption...