Tire size questions

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mflynn

mflynn

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This is not technically an a-body question, but figured I could get good info here anyway. In addition to my ‘68 notchback, I have a 1987 D150, 2WD, 318, 2.9 gears with stock wheels and tires - 235/75/15 Wrangler TA (photos attached). I would like to run chrome Steelies with baby moons for the summer and want to get more of a street rod look but am worried about messing up ride and performance. I won’t be towing or hauling heavy loads. This is my daily driver When I am not driving the Cuda. I am thinking 245 (or 255)/60/15 BFG Radial TAs or Cooper Cobra Radial Gts. Any ideas on if these will fit ok and if so how they will affect speedo, performance, rpm at highway speed, etc? Also, any issue with running passenger rated tires on Light truck (remember, I won’t be doing heavy towing or hauling)?
101036A0-0BD3-4068-9D19-8757A7D15D5A.jpeg
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BFG are okay if you can find them. Cooper Cobra are crap tires - they just come in popular sizes for our vehicles. I'd lean toward the 255/60R15 personally. You could ask Cu440da what size he runs on his Warlock - if he still comes around this site. I think he uses different sizes front and rear and his is lowered.
Warlock and Dart at the track.jpg
 
Measure your existing tire . What is needed is the diameter and the width at the bulge . The diameter will determine if your speedo and mileage will change and the width will tell you if you haveenough clearance . All tire makers post these numbers . Get it close and you are golden . "75" series is a tall tire , I'm thinkin'.
 
ignore the pre-populated sizes, just plug in your own
 
Your stock tires are approx. 28.9" tall. A 255 60 r15 is only 27" tall almost a 2" drop in height. It will help acceleration but might look a bit small in comparison. Your Speedo will be 4.5% off ready slow, 60mph will be 57mph.
You can use this website to run some tire sizes to get an idea of how tall a tire is.

Custom wheels, rim tire packages
 
Remember that because the axle is in the center of the wheel, the truck will drop or rise 1/2" for every 1" of diameter difference.
 
Thanks for all the advice! Checked out some of the stuff you guys linked to. To keep about the same size overall diameter I am now thinking about 255s on 16 inch rims. I’ll post pics later this spring when I switch them over.
 
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