Anybody on here recorded the difference in ET between the 20" GMC wheels and 17"s or 18"s? I know the 20s must be considerably heavier than even the factory 17s and 18s. I'm running dealer installed D20's and G/year LS2's, which I really like the looks of, but I'm thinking of either getting a set of Centerline rotary forged 20's or some 17" or 18" wheels and tires to run at the track, if it makes a big enough difference.

 

i ran a 14.7 with stock 20s and then put the stock 17s from an 06 silverado a ran a 14.2. So 1/2 sec for me and the weird thing was i ran the same mph with the 17s at a 14.2 that i did with 20s at 14.7

 

Same with me, 1/2 second off from 20s to 16s.

 

So what is the weight difference from the 20's to the 16's ot 17's?

 

It may not be a total weight issue, but a rotational mass issue. Where the weight of the larger rim contains more inertia to prevent it from stopping, and takes more HP to get it spining.

This figures your tire heights are the same lets say 30 inches and the rim/tire weights are the same.

I was looking at some Centerline 24's a guy I meet had on his truck, and he said it still killed his mpg's by his standards.

 

20s were 84lbs each with tires, 16s were 46lbs. I ran with the 20s just on the front once, and still dropped time when I put the 16s on the front. It is rotational mass as well as actual weight. Now with the centerline 17s and the centerline 18s that I had, it wasnt as bad because they were really close in weight to the 16s.

 

I know cheap 20's can be up there, and stock steelies are quite a load. So I would love some Centerline 17x9's to get the 275/60/17 with a 250 treadware to lay down wider. Should be able to compete with the 20-22's on the street when tossing corners.

Although I will probily get Caddy take-offs to keep my new tire cost down since I due here.

 

I just went from the stock 20's with 275/45/r20 tires to the stock aluminum 17's with the 245/70/r17 tires. The 20's weighed 82 lbs. The 17's weighed 59 lbs. Only 23 lbs difference but the "SOP" feeling is really noticeable. Haven't been to track since swapping. Looking forward to see the difference.

 

Thanks very much guys. That's incredible gain! ****, even if I bought a new set of the Centerline 20's (which only weigh like 2 lbs more than their 18's) and new tires, that would certainly still be big bang for the buck! (BTW: Centerline have a special on now for some of their 20x8.5s with tires mounted/ balanced and lugs and locks for under $1600.00 bucks! (I had a set on my old Nissan Titan and loved them). I think I'll go with 17's or 18's though.
Better yet if I get a shorter tire and recalibrate for the shorter effective gear ratio!

 

I gotta say the smaller rim will be faster even if the 20's are the same wt. Like stated above, the rotational mass kills it. The further the wt is away from the hub the worse it is. I bought some 20" centerlines that only weigh 24lbs a piece, but the lower profile tire is heavier since they have to make the sidewall thicker. also to match stock tire ht i had to go with a 305/50/20. Looks good but way to wide. Almost 12". Last week i finally went to the track and could not hook up from anything under 1/4 throttle off the line. this was with general grabber UHP rubbers with a 320 treadware. Too wide kills traction with no wieght on the axel. Unless their slicks