HOW WIDE Tires ? (Page 1/2) Lou6t4gto JUN 05, 05:53 PM how wide a TIRE can I put on a 18" x 7.5" Wheel for the rear of my chop top ? ( i can use "spacers" if needed, because I have wide wheel openings/1/4s) Thanks Will JUN 05, 06:24 PM Not sure I'd go above a 225 on an 18x7.5 Lou6t4gto JUN 05, 06:48 PM make any difference 60-55-50 -45 ?? Lou6t4gto JUN 05, 07:02 PM make any difference 60-55-50 -45 ?? like to find a couple of 18x 10s to match what I have in 18x7.5 ! or even 17x 10s Joseph Upson JUN 05, 08:22 PM 50 series. The Fiero is not that wide of a car, I ran 18x9s on the rear and that was plenty wide. Just make sure you use good quality wider tires. I ran 245/40r18s and considering the Fiero is not that awful heavy, the wide tires on the rear required caution in the rain on the interstate and the exits. I could brake traction at cruise speeds on wet hwy roads in 4th or 5th gear by simply gradually applying throttle to accelerate until the rear end wiggled and if the alignment is not spot on the wider tires have a way of making that evident on wet roads also. cvxjet JUN 05, 09:45 PM I just want to do a comparison to the new Vette.....It runs 245 and 305 width tires, so considering the new Vette weighs in at almost 3600 lbs while our Fiero V6s weight in around 2700 lbs, the ratio is approx' 1.333 to 1........Comparable tire sizes converted by that ratio equal 185 up front and 225 in the rear! One critical thing to always be aware of is that really heavy tire/wheel setups absolutely KILL your car's performance......I have seen a range from 12 lbs up to 24 lbs for a 17 x 8 wheel......That is a TWELVE POUND difference! 40 lbs of unsprung rotational mass equals 200 lbs on the sprung/non-rotational mass. Also, a tire that is mounted on a (Relatively) wide wheel is more stable during cornering; My 1972 Comet had 235/245 60-14s on ET mags 14 x 6.75 rims- I could push the car sideways with my foot on the wheel approx' one INCH....I then converted to some really good looking Appliance 14 x 8 rims and couldn't hardly move the car sideways no matter how hard I pushed.....This is a similar effect to the low-sidewall tires nowadays..... Daryl M JUN 05, 09:52 PM I have 235/45r18 on my 87GT. I used 1" spacers for spring clearance, but that will depend on your wheel offset. I also have some 255/45r18 mounted for my 88 swap project on 7.5" rim's. Not on the road yet, but I think it will work ok. Different tires have different rim requirements. Some need wider trims than others. Check with the tire manufacturer. Lou6t4gto JUN 05, 11:25 PM MY Fiero Is WIDER than most, chopped, shortened etc. it has a" warmed up" 3800SC, so I'm not too worried about losing power with a heavy tire. Joseph Upson JUN 06, 06:50 AM quote Originally posted by cvxjet: ... One critical thing to always be aware of is that really heavy tire/wheel setups absolutely KILL your car's performance......I have seen a range from 12 lbs up to 24 lbs for a 17 x 8 wheel......That is a TWELVE POUND difference!... Absolutely! and I mentioned it at some point after the wheel and tire upgrade somewhere. quote Originally posted by Lou6t4gto: MY Fiero Is WIDER than most, chopped, shortened etc. it has a" warmed up" 3800SC, so I'm not too worried about losing power with a heavy tire. Worry, I don't believe it unreasonable to estimate that your warmed up 3800SC and my turbo 3900 stroked to 4200 would be fairly close in performance. I gained 20 lbs for each wheel assembly over the previous and I felt the penalty immediately on acceleration performance without question. Rotational weight (inertia) and mass are not the same. An increase in rotational wt/inertia will have a near double effect than if the equivalent amount of weight were placed in the passenger seat. Will JUN 06, 12:21 PM I have 285/30's on C5 Corvette 18x9.5's under stock bodywork with stock struts. I installed with 1" thick bolt circle adapters.