235/40r17 vs 235/45r17 difference
08-06-2018, 10:02 PM
#1
Thread Starter
Join Date: Jul 2018
Location: Florida
Posts: 5
235/40r17 vs 235/45r17 difference
my 2003 mustang gt currently has 235/45r 17 tires in the front, and 275/40r17 tires in the back as it came like this from original owner. I am in the market now to buy new tires and was wondering if 235/40r17 tires in the front would be a drastic difference. Would it change the feel/ appearance of my car or lower it in any noticeable way? any help or comments on this would be appreciated. thank you.
08-08-2018, 02:53 PM
#2
Gentleman's Relish
Join Date: Feb 2005
Location: AZ
Posts: 13,090
I wouldn't go that low profile (40) on such a skinny tire (235) . It will be like driving on rubber bands and will transmit more road imperfections to the steering wheel and passenger compartment.
Here's something else to consider.
235/45 tire has a sidewall height of ~106mm
235/40 tire has a sidewall height of 94mm
That's a 10mm wall height difference and a 20mm overall tire height difference (25mm is an inch)
275/40 has a wall height of 110mm so overall tire height is comparable to the 235/45 (~106mm)
If you go with a lower profile tire in front (235/40 -94mm)) and keep your 275/40's in the rear (110m) that's over an inch (32 mm) in tire height difference that is biased towards the rear. A taller tire in the rear increases your oversteering...that means on hard and heavy corners, the rear is going to be trying harder to come around and get you sideways.
I would recommend keeping the same size fronts for both comfort and handling or, if you're considering a shorter front tire, consider a shorter rear tire as well like a 275/35 (96mm wall height) to match your new fronts. It will be better balanced for steering but will still transmit more noise and vibration into the steering passenger compartments and the seat of your pants.
Here's something else to consider.
235/45 tire has a sidewall height of ~106mm
235/40 tire has a sidewall height of 94mm
That's a 10mm wall height difference and a 20mm overall tire height difference (25mm is an inch)
275/40 has a wall height of 110mm so overall tire height is comparable to the 235/45 (~106mm)
If you go with a lower profile tire in front (235/40 -94mm)) and keep your 275/40's in the rear (110m) that's over an inch (32 mm) in tire height difference that is biased towards the rear. A taller tire in the rear increases your oversteering...that means on hard and heavy corners, the rear is going to be trying harder to come around and get you sideways.
I would recommend keeping the same size fronts for both comfort and handling or, if you're considering a shorter front tire, consider a shorter rear tire as well like a 275/35 (96mm wall height) to match your new fronts. It will be better balanced for steering but will still transmit more noise and vibration into the steering passenger compartments and the seat of your pants.
08-19-2018, 05:41 PM
#3
6th Gear Member
Join Date: Feb 2007
Location: state of confusion
Posts: 7,635
Your 2003 GT should have come OE with 245/45-17 tires, which are Load Index 99 in XL. 235/40-17's are only Load Index 90 in SL, which compares to 94 in XL. Basically it's too small of a tire for your car on the basis of load capacity.
245/45-17 and 275/40-17 would be the best staggered-tire combination for your car. The 275/40-17 compares at Load Index 98 in SL (102 in XL).
Norm
245/45-17 and 275/40-17 would be the best staggered-tire combination for your car. The 275/40-17 compares at Load Index 98 in SL (102 in XL).
Norm
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