Can rim size affect trans performance?

[tkd_q45]

Before I spend time swapping rims to try it I thought I'd ask here first. My 94a W/18" rims does not have near the kickdown performance that my 92 w/stock 15s". Any thoughts?

[FarFetched]

It all depends on tire size.

[tkd_q45]

215/65/15 vs 245/45/18 - the later being 26.7-26.8" instead of stock 26" + difference of wheel weights (unsure though I'm certain the 18" weigh more).

[maxnix]

If intake path is not perfectly clean and all else up to OEM snuff, then you are close to lugging it. Remember, you are now going faster at lower rpm.

Use 3 around town and up to 60 mph.
Modified by maxnix at 10:14 AM 7/25/2005

[zul8tr]

Yes it can effect transmission performance because different engine RPM is going to occur. To match tire rim fitment the original OEM circumference (or diameter) needs to be the same. So the larger the rim diameter the less the rubber height has to be.

For example:

a 205/60 R15 dia. is 205x0.6x2 + 15x 25.4 or 627mm or 24.69"

A 225/50R16 diameter is 225x0.50x2 + 16x25.4 is 631.4mm or 24.86"

Therefore the 16 " rim setup will have less acceleration than the 15 although small in this example. There will also be a speedometer error of 631.4/627 or 1.007 or 0.7% about 0.4 mph low at 60 mph.

The other aspect of a different rim is how the weight is distributed in the rim tire combinations. If both setups weigh the same but the weight of one setup is concentrated near the outer portion of the rim then the that setup has a greater rotational moment of inertia (I) than the setup with the weight distributed closer to the rotation center. As a result the setup with the greater "I" value will have the poorer acceleration performance due to greater torque needed to accelerate the greater "I" setup.

Smaller wider tires are better acceleration setups than taller setups if both weigh the same with all else being equal.

[elwesso]

Just remember the 1st gear difference in the 9093 vs 94!!!