supermoss

Will it affect the speedometer on a 2007 sl65 to put 20 inch sl63 wheels on it?

boostd

The correct +1 is 255/30/20 front and 305/25/20 back. As long as you have these size tires, your speedo will be accurate.

Viper98912

Use the tire size calculator under tools on this website (or google search the term)

sound 8

Do you realise by fitting 20 inch wheels you will loose POWER
According to those in the know...
S8

supermoss

You won't lose any power, it just will produce a higher top end like going to a lower numerical rear end gear ratio. In this case I don't think the loss in stop light to stop light quickness will be noticeable.

boostd

Depends on unsprung weight, actually. If the 20" setup is heavier, you'll lose some power.

byronburns

The ride will suffer. I have 20" vossens. the tire sidewall is so short. It makes for a harsh ride. I actually tried to get 19" ones. they won't fit over the front calipers. Good luck. they will look great

sound 8

Nothing to do with gearing, for some reason a bigger wheel will loose
power, this was discussed at length a few months back.
S8

supermoss

Opinions vary so lets just leave it at that. Thanks for your input though but my concern was only how it would affect the speedometer. With 600+hp power to the ground is not really a concern. I went from 20 to 19 on my TT Porsche and felt no difference.

boostd

Speedo is affected by overall diameter only.

supermoss

I will use the tires you suggested. Thanks so much for the info!

Jan T

Yeah, tire calculator works best for determining size. While at it, maybe consider 20 front 21 rear. Gives it a bit more rake appearance.