DerangedPony New Reader
3/25/12 4:33 p.m.

I have a set of 205/50R15 tires but I have two different options in which wheels to mount them on. I could use the wider 15x6.5 or save a little over 2 lbs. on the narrower 15x6 wheels. On a daily driver/weekend autocross car, would I see a bigger difference in the added width or the savings of 2 lbs. unsprung weight? This is my first year doing autocross, so I'm not expecting to be competitive, just making sure I like the sport before I start spending money on it. Thanks

mad_machine GRM+ Memberand MegaDork
3/25/12 4:40 p.m.

that's a lot of weight for half an inch width

FlightService SuperDork
3/25/12 4:44 p.m.

willing to bet the designs are very different.

2 lbs on 4 wheels is effectively removing 24 lbs from the car.

What's the car? Is that worth it? Do you have 24 lbs worth of stuff you could remove from the car already? (Books, tools, if it was Ted Kennedy's old car decomposed hooker?)

On the street I doubt you would even notice.

iceracer SuperDork
3/25/12 5:45 p.m.

I'd go with the wider wheel and run 5 less gallons of gas.

DerangedPony New Reader
3/25/12 5:47 p.m.

Its for a Focus. The 15x6s are a set of stock focus wheels while the 15x6.5 is a set of stock Ford Contour wheels that my winter tires are currently mounted on.

I'm sure I can remove 24 lbs elsewhere, but then I would be 48 lbs lighter if I used the lighter wheels. Basicly, will a 1/2 in. Wider wheel give me any noticeable benefit on a 205 tire?

mad_machine GRM+ Memberand MegaDork
3/25/12 5:48 p.m.

that is also weight in one of the best places to loose it. Unsprung AND spinning.

FlightService SuperDork
3/25/12 5:51 p.m.

Just to review the actual weight loss calcs

2lbs x 4 wheels is 8 lbs.

I am not going through the equations but rotating mass is effectively 3 times that of stationary so

3x8lbs is 24lbs.

Not 24 lbs of rotating mass. Just 24 lbs equivalent of stationary mass.

Just wanted to clarify

Gearheadotaku GRM+ Memberand SuperDork
3/25/12 8:44 p.m.

Performance difference will be very tiny. Put on whichever looks better.

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