I'm not trying to sound ignorant or anything but do you have anything to read or a personal experience on an incident you just described. I'd like to check out what you're talking about, sounds like something I may or may not be able to avoid.

If the car came standard with 215/70/15 tires and he went with 175/70/14 tires the speedometer would be off by about 7 mph, according to one of those tire size calculators. So when the speedo reads 60 mph, he is really travelling only 53 mph. Safety being another issue, how will the this screw up the engine management systems?

How the engine computer uses vehicle speed in various routines is very complicated. I program OBDI cars but have not personally disassembled OBDII binary files. However, I do know that timing/fueling is dependent on vehicle speed -- for example "cruise" condition higher speeds will add timing and lean out a/f ratio, the amount of enrichment during acceleration will change, based on many things, but including vehicle speed. Also with your trans -- the most obvious thing based heavily on vehicle speed is the lockup torque converter. If the ECU will let the car lock up the converter in 3rd gear at or above 40 mph with light load, and you are only going 20 mph but the speedo reads 40, the converter will lock, and you will be lugging the car down (also putting unnecessary wear on the converter clutch since it will probably be engaging too frequently)

The speedo will be off by a percentage, which wil obviously be lower at low speeds and higher on the highway. Theres a chance that, aside from annoying transmission shift routines being slightly screwed up, that you won't really damage anything, but I certainly would not be taking that risk. Also how will a 3600 lb car handle in an emergency evasive maneuvre with 175 tires on it? Come on

I think I'll be fine. If I see any signs of what you have said I will more than likely get my computer flashed to compensate for the new tire diameter. But after I got them installed, I'll let you guys know how it'* going and if any problems have occured. I found some 185/70 from pepboys that I will probably buy, so maybe that'll will make this situation less potentionaly hazardous.

Intense-racing.com has a speedo recalibrater for around $100 if you run into noticeable problems. Oh man I just read you have an SSEi, this post makes me want to cry. You can have my L36 (N/a) LeSabre to slam and I'll take the SSEi.

Cool. That definatly would help if I need it because last time I heard a computer flash cost more than $100. Thanks for the information now I know what I could expect from degrading my tire size.

"You can have my L36 (N/a) LeSabre to slam and I'll take the SSEi."

You know I got to have some power out there for those a-holes who think they are the "shizznits"

Lowrider on a new era Pontiac? Very interesting I must say

yeah i custom airbag kit will run you about 2k
right now i am the only bonneville on this site to have something in the works

First off let me say that this sounds like an interesting project and the fact that a few of you are giving him crap about wanting to try and do it (even if it doesnt work) is appalling. We should be here to help each other out not say how stupid an idea sounds.

You will run into issues with shifting if using smaller or larger tires however the PCM can be flashed to compensate for the change (99.00 for a pcm and about 200.00 for a custom flash).

The SRC is only for gearing changes in the trans I believe. The PCM would need to be tweaked in the case of non stock tire sizes.