With 235x45x18 tires 45et what would be the spacer size to clear suspension?
Rather than answer you in PM Eddy, here's your answer:
eddymarsh said:
The only calculator I saw told me stock size vs new size. I just want y o know how far I have to have safe backpacking. The only spacers I could get were 30 mm. I have about a half inch clearance between tire and suspension. Would 15mm be safe bet or 20
I cannot answer that without: 1. your wheel width; 2. your wheel offset in mm (ET); and 3. your tire width I'm mm. Then I can show you how to use calculator.
Stock 2004 GLX wheels are 16x7 ET38 with a 205/55 series tire. Thats a 8" wide tire mounted on a 7" wheel with a net offset of 38mm from center. If the upright clearance of the 205 series tire on a wheel with ET38 is .5", then to maintain the same upright clearance with a 235 series tire, you would need a net ET28 (because tire is 20mm wider, and half of that is on upright side of wheel, so ET38 - 10mm will "poke" wheel out an additional 10mm and create room needed for 235 series tire.)
So to fit your 235/45 18s ET45 (and assuming they are 18x8s) you would need 15mm or 20mm spacers, I would opt for 15mm. But other things to consider:
- Your original wheels are probably 205/55-16s. That means your circumference per wheel is equal to 2x(.55x205mm)+16"xPi (because circumference = Pi x diameter of a circle). I'll do the math 1.1(205mm)/25.4mm/inch + 16" = 24.774" and 24.774" x Pi = 77.83". So the circumference of your original wheels is 77.83"
- The same calculation applied to your proposed 18s is: 2x(.45x235mm)+18"xPi, or 0.9(235mm)/25.4mm/inch + 18" = 26.326" and 26.326" x Pi = 82.71". So the rolling circumference of your proposed 18s setup will be almost 5" longer (4.877") or 6% different.
This 6% will affect a number of things, it will cause your car to accelerate slower, because the force to turn a larger wheel is greater than the force required to turn a smaller diameter against the same resistance (the inertia of the the car), it will also cause your odometer and speedometer to read falsely by 6% slower (60mph indicated would actually be 63.6mph, 100mph indicated would be 106mph actual, etc.)
A possible benefit is a 6% in highway miles per gallon because you are effectively adding 6% to overdrive gear by traveling 6% farther with each revolution of the wheels.
The proper 18" tire size for the size wheels you are proposing is 235/40-18. This is again assuming your wheels are 18x8s or 18x8.5s and not some crazy 18x10s. 18x10s would be a completely new set of problems. Solvable, yes, but not as easily as 18x8/8.5s. 235/40-18s have a rolling radius of 79.8" or about a 1.2% difference from stock tire circumference.
:wrench: