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I have recently upgraded from stock 16" rims to 265/35R22 on my wifes 4cyl 2008 Ford Escape. I love the look but it does just the same as my 2001 Silverado also with 22" rims. While on the highway using cruise control set at 70-75 mph when going up any hill it downshifts harder than with the stock wheels. What can I do (computer mod, cold air intake....) to fix this issue ?? any advice would be appreciated  

this is a computer shifted transmission...


you might want to use a scan tool...  erase the codes..

then disconnect the battery for half an hour...

on first start up and movement.. be sure that the car is positioned where you can take it for an easy test drive..

where you will slowly accelerate to 40 MPH without lifting the throttle to force it to shift..


this may teach it new shifting routines ..   i don't know if it will work.. but its worth a try...

by going to a different sized wheel and tire combo... you have changed the leverage ratio between the engine, transmission, rear end and roadway..  

I did the math and according to Tire Guides, your vehicle came with P235/70R16.  A 265/35R22 changes the overall diameter just a bit over 1% - not enough to worry about.

So I wonder what is really going on.  Could it be just a perception?  

Its about the transmission of energy.  I'll bet the tire with the taller sidewall will absorb more of the sudden torque (turning or twisting effort) generated by a downshift thereby making it feel "softer". P235/70R16 has a sidewall height of over 164MM while the 265/35R22 has a sidewall height of 92MM.  Also, please consider the "high ply turnup" generally associated with super low profile V, W and Z speed rated tires results in quite a rigid sidewall which will undoubtably aggravate the problem you speak of, just me thinking outloud.  

I'd say this is a combination of 2 things, causing the shifts to feel harder:

The larger wheels make your engine work that much harder to move the truck, and so it downshifts sooner (at a higher RPM) than it did before.  And as someone mentioned, the new tires have a much smaller sidewall, and it absorbs less of the shock of shifting gears.

To remedy the first problem, you could look for a computer mod that increases torque at lower RPM (you want torque for this, it's more important than horsepower).

The smaller sidewall is a bit more tricky, it's kind of what you live with when you have 22" rims.  However, you can look for tires that have a softer sidewall, this will help a little.  If you really want the softer feel, you may have to move down to 20" or 19" rims.

Finally, you can consider a different transmission fluid, or additive.  I wouldn't touch an additive, but for any car that uses Dexron III fluid, you can upgrade to the newer Dexron VI

For customer reviews on tires:  links dot thefreemechanic dot com /tirereviews

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Curtis
TheFreeMechanic
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