Tires and Sizes -- FYI

[drkknight196]

Due to the issues I have had with premature excessive tire wear on both front and rear, I've replaced ALL my tires with the OEM (BF Goodrich, ZR "G-Force", KDWRS). After consulting with my Lincoln-Mercury service advisor and a Ford SA, I've installed 245-55s on all four wheels (and the spare). Managed to do it all for $100 out of pocket. Don't ask me how! I put 38 lbs in the rear and 34 in front. So far, everything seems just fine and I haven't noticed any difference in the appearance of the vehicle's stance. I'll post any problems.

[jefferson-mo]

Any ABS lights or any kind of electronic trouble????

"We" were told if we changed the stagger in the tires it would casue ABS problems.......if it doesn't that's a real good thing...........it probably helps acceleration too:uzi:


:bows:thanks

[TAF]

Thanks for the update. I'm assuming when Dennis put in your 4:30s he flashed your chip for the speedo offset...any reflash necessary with the same size tire at all four corners?

Also, how 'bout a thought from you on the RPMs/drivability of the 4:30s at cruising speed?

AND...I MUST ask...$100 for all 4? Forget it...Must be those "g-man" contacts...

Thanks,

[jefferson-mo]

Also can you post a pic of the car?

It probably looks great

[jefferson-mo]

I just talked to my brake guy and my EEC guy and they both said that with just ABS there might not be any problems, but with traction control there might be an issue.............

my suggestion is someone with T/C on their car could try this??

Also in my tire book I don't see KDWRS tires...only KDWS

Discount tire or Costco maybe????

[jefferson-mo]

KDWS=$156.95 each

[drkknight196]

OK sorry, they're "KDWS." All from BF Goodrich. All three dealers in this area can get them for $97/each. Here's how I did it: Fronts were replaced under Ford warranty since they misaligned my front end; Goodrich gave me %50 off the rears for premature wear; the Goodrich guy swapped my 235/50 spare for a new 245/55 since his mounting guy scratched one of my wheels (it's getting polished out Saturday). Service advisors tell me ABS is measured and controlled at the rear of the car hence it will have no effect. Can't speak to traction control (I have 300A), but don't know why it would be a problem since the rears are still the same size. Have no clue why larger tires on front would affect acceleration. Of course Dennis coded my chip to compensate for the 4.30 gears (tach and speedo are right on). Again, no clue why a reflash would be necessary simply because my fronts are a size wider and taller. ???????? Will post picture soon.

[engine23ccvfd]

I really like the down front end stance of the MM....But I am scared to death of a flat since it will take at least a day for a new tire to arrive (have not found anyone local that stocks our tires)...question is can the rear suspension be adjusted w/o comprimising ride to get that front dip back after changing to same size all around?

Would also love to see a pic!?!

[Crown Vic]

question is can the rear suspension be adjusted w/o comprimising ride to get that front dip back after changing to same size all around?
The rear air suspension can be adjusted. There is an arm that connects from the rear axle to the frame diagonally. On that arm, on the driver's side of the car, there is a little rod which is the level sensor. If you look at the top of that sensor, it has 2 bolts on its bracket that can be loosened. That little bracket can be slid diagonally. What you do is loosen those bolts, and slide that bracket to "simulate the car being too high (extend the sensor) or too low (shorten the elngth of the sensor). What this does is make the car think it has less weight and will lower itself accordingly...same as if you put 3 people in the back...the car senses more weight and raises itself to stock height. And when those 3 people get out, the car is jacked up like a truck and since it senses less weight now, it lowers itself to stock height once again.

It may take 2-3 tries to get your desired ride height. Also, before you begin, mark the stock location with a marker or a sharp point to scratch a mark. From there, maybe got in 1/4" increments and see how it turns out.

So you can use this to lower...to raise the car, just do the opposite. Once you look at it, you'll get the idea.

FYI: Make sure you disable the air suspension with that switch before you begin and enable it after you're done.

[darebren]

I don't believe you. according to your signature, you don't even have that car yet. lol.

[Crown Vic]

2003 MM 300A (born 6/03; adopted 9/11/03)
Very true!!! Seems the car was bron 3 days ago... Congratulations, its a girl!!! :D

[drkknight196]

I've had numerous critically-minded law enforcement and gearheads study my car and none have been able to notice any difference between the way it looked before and after. My guess is that the overall increase in height from the tires can't be more than an inch or so. Maybe someone knows exactly the difference in total height between the 235/50s and 245/55s.

[SlvrBullet]

I figure the difference this way: 235x.50=117.5
245x.55=134.75 The difference is 134.75-117.5=17.25
Got 2 of those radii, so multiply by 2: 17.25x2=34.5mm.
Convert to inches: 34.5/25.4=1.36 inches. I didn't calculate the 18" wheel, as it's a factor common to both wheels. Anyway, that's what I figure the difference in overall height of the two tires is 1.36 inches, and if I'm wrong, I'm sure I'll hear about it. :stupid:

[darebren]

hmm, so a 245 x 55 = 134.75

I thought a 55 sidewall was the same height for any width? I guess I'm stupid, but you would say a 265 x 55 = 145.75? whereas the sidewall height is a percentage of the width?

[darebren]

yep, 1.36 inches difference needed. i used this link

http://www.nsxsc.com/tirecalc.html

to verify the stock height difference.

now to see how other sizes could keep the difference to a minimum from stock difference. I suppose from Thomas Potter's posts about his new wheels, one can't play too much from stock due to ABS/TC issues.

[darebren]

I did some work solving for rear tires based on known front sizes that work and keeping the rear differences the same or close to stock. Keeping the revolutions per mile difference the same is probably the most important.

fronts 255/35/18 rear 255/40/18 stock rims

or

fronts 255/45/18 (kenny brown uses this) rear 255/50/18 stock rims

or

fronts 255/45/18 rear 285/45/18 (same differences as above example, but not sure if big meats would fit the back, and would need 9 inch rims, so would need to buy new rims up front to match. most expensive option.

[drkknight196]

Not sure why the revolutions per mile ratio between front and rear is important as speed/tach readings are calibrated by proper chip programming and OEM rear tire size ................?

[darebren]

revs is for proper trac control and abs function

[drkknight196]

Both are controlled at the rear wheels according to my service advisor.

[SlvrBullet]

Anyway, someone asked if the "series" was related to width and height. Yes, aspect ratio is the ratio of the "section width" to height of the sidewall. 50 series is half as high as it is wide. 70 series is 70% as tall as it is wide. Section width is NOT the same as tread width, tread width varies with model/manufacturer. The section width is the widest part of the shoulder of the tire. Try comparing the overall height of these tires to see if they are interchangeable: 245/45r17------275/40r17.