New is250! I need bigger wheels.
 

Hey guys,

I just bought a base is250 with the 16" wheels with 205 55 16 tires on all 4 corners. I’m going to upgrade to 18s and noticed the isx50's with stock 18s have a taller tires in the rear 255 40 18 as oppose to 225 40 18 in the front.

My question:
If I go with 255 40 18 in the rear. Will I need to get my Speedo re-calibrated?

Thanks,

i highly doubt it. my 95 LS400 came with 245/40R16 originally. Than i recently put on ISx50 wheels with 225/40R18 Front and 255/40R18. Everything seem fine to me, my Lexus friend didn't tell me to calibrate anything. We just slapped them on and took off :p

The oe combo would be 225/40-18F and 255/40-18R so speedo should be fine. Surprised you have an IS with 16's oe, never seen that before.

canadian IS250 had 16" stock.

should be, but keep in mind, I bet his traction system (abs at minimum) is programmed for same diameter all around, so, changing diameter from front to rear really wouldn't be advisable... however, he could do something like 225/40-18 front and 255/35-18 rear - that would be pretty much same diameter as OE and keep the ratio the same as well...

That's an excellent point. We're seeing this with the new Mercedes S-Class
to some extent. The base cars have 245/45-18 all around, but the AMG cars
have taller rear tires, 255/35-20 and 275/35-20. The Star system (ECU) is
programmed for this, but so far we can still get away with changing to
same-diameter front & rear set-ups like 255/30-22 + 295/25-22.

I'm not sure what the allowable range is on the Lexus, however.

I always thought the taller rear tires on the 18" IS package looked goofy anyway.