JacobT

I've been thru 3 sets of rims and I weighted them all with tires(bigger tires are heavier too).

16" stock: 45 lb
18" RH C5 3piece (18x9.5): 56 lb
20" Dronell (20x8.5): 58 lb

I do feel slower with 20's. But you can tell it's probably not due to the weight

garnet92

No, I wasn’t blaming the loss of take-off solely on weight – but I’ve been curious as to what the wheels weigh since they weren’t listed in the 44-page wheel weight listing and gs4will didn’t have any weights for them. And who knew – they could have been extremely heavy wheels? Seems that they’re about average for the construction/size.

The UPS tracking detail for the new tires shows them at a total shipping weight of 60 lbs (2 tires). Figuring a couple of pounds for packaging, leaves about 29 lbs per tire. This would yield a total wheel/tire weight of 56 lbs, which fits right in with Jacob’s actual weights.

Just spinning the tires with a much larger contact patch would be more difficult – and yes, I know that spinning a wheel isn’t helping acceleration. Maybe I’m regressing to when I was 17, but I still like to light them up occasionally (just for grins). And, it’s not only the wheel-spin – it’s a perceived loss of torque at low-end. It’s not my imagination – I don’t WANT it to be slower on take-off.

So, in the final analysis, what causes the (apparent) loss of low-end?

My old 17” Toyo FZ4’s weighed 24 lbs and were 25.3” in diameter. According to GS400_PUSHER, the stock 17 chrome weighs 26 lbs, for a total of 50 lbs.

The new S-03 275/30 are 25.6” in diameter – and weigh about 29 lbs. That’s a total of 56 lbs.

Does 3/10th of an inch increased diameter and 6 pounds of additional weight (on each rear wheel) make that much difference?

As we say in Texas, I reckon.

IS2000

Here's my story...

I just upgraded my stock 16s (45.1lbs) on the GS430 to 18s. By doing so, I gained an average of 5lbs per wheel. My current setup is 245/40-18 (49.39lbs) front and 275/35-18 (51.04lbs).

I read somewhere on this board that an increase of 1lb on the wheels equals a x3 weight increase on curb weight since rotational mass is increased by the spinning wheels.

By my computation, 5lbs x 4 (wheels) = 20lbs x 3 rotational mass = 60lbs weight increase. So, I ditched my spare, trunk matting, jack which is good for roughly 55lbs (45lbs spare, 5lbs matting, 5lbs jack)

Gtech stock
0 to 60, same road, 1/2 fuel, normal launch (foot off the brakes and WOT), no A/C
2 runs yielded -- 6.32secs exactly!

Gtech with 18s (plus 20lbs from 18s)
0 to 60, same road, 1/2 fuel, normal launch, w/ spare, matting and jack. No A/C
2 runs yielded -- 6.62 and 6.63

Gtech with 18s (less 55lbs from stock) (plus 20lbs from 18s)
0 to 60, same road, 1/2 fuel, normal launch, no A/C, no spare, no matting and no jack
2 runs yielded -- 6.52 and 6.53

I really thought by ditching the heavy spare, matting and jack, that I could get back to my stock wheel speed times. However, from my tests, I only managed to improve .1 secs.

This really brings me to the conclusion that even though you are able to find extremely lightweight rims and tires that match your original stock 16's weight, the simple fact that you will be using wider tires in your plus sized wheel and tire combo -- this will affect your acceleration! Thus, wider tires with everything else being equal, does affect acceleration.

But what surprised me the most was how consistent the Gtech meter was!

bitkahuna

iTrader: (20)

IS2000 - interesting read! Do you know how much the diameter of your 18s is diff from the 16s?

IS2000

Spec Sidewall Radius Diameter Circumference Revs/Mile Diff
225/55-16 4.9in 12.9in 25.7in 80.9in 783 0.0%
(stock)
235/45-17 4.2in 12.7in 25.3in 79.6in 796 -1.6%
(optional)

245/40-18 3.9in 12.9in 25.7in 80.8in 784 -0.1%
275/35-18 3.8in 12.8in 25.6in 80.4in 788 -0.6%

garnet92

IS2000 – Thanks for the Gtech numbers – that verifies what we’ve all felt in our shorts. I’m surprised to see that removing that weight didn’t bring you back to original numbers though. That’s a pretty severe penalty to pay for larger wheels – an easy way to add .3 seconds to 0-60 time. Just think about the mods that will give you a solid .3 IMPROVEMENT in 0-60 – there here aren’t that many.

I am disappointed to see the 0-60 numbers though – generally, the Gtech has been shown to be about .2 sec fast (lower) compared to timed runs at the track. Assuming that to be true, I’d have hoped to see the Gtech numbers at 6 or below. Anyway, I think (weather willing) I’ll try to get out tomorrow or Sunday and Gtech my car as well. My biggest problem is finding a stretch of decent road long enough and with little traffic without driving to west Texas. This will just be to get a base point – I don’t intend to change out wheels, etc. But will re-run after install of SRT race ecu and TM plugs. I’m hoping to get some of that “.3” back via those additions.

Manaray

garnet - thanks for the info about ride quality...I'm sure it will help others choose!

IS2000 - Thanks for the numbers!

I too have a G-Tech but I haven't been really using it...I should try it and see what kind of numbers I get...it's much harder now that I have an exhaust...since on WOT, it's loud enough to perk someone's curiousity...I'd have to do a run and then run...away...

///MDex

Wheel spin is inherently bad, yes, but I can still get sideways when I want to with my 9.5s out back.

Time for the upgraded TC and LSD Bit.

dipstick

I believe some wheel spin will get you a faster time. Brake/torque starts are used for 0-60, 0-100 times by experienced performance drivers. No-spin starts (street start) always yield slower times. We have quite a few CL members who have run at drag strips -- what do they do? Also about plus wheel sizes, I have posted about a really thorough wheel size comparison in R&T a couple of years ago using four BMW 540s with sport package (directly comparable to a GS4 with L-tuned)and 16, 17, 18 and 19 inch rims with lower profile tires, maintaining tire OD. As I remember, the 17" wheels were overall best, followed by 18" -- look it up. I think 19s and 20s are really for looks, which is great, but I wonder about improved performance. You know, after you invest $3,000+ for big wheels, there is going to be a placebo effect. Just my 2 cents.

garnet92

Well, I finally got off of my lazy butt and found a patch of road suitable for some 0-60 runs. Disappointing times – but that’s life.

Made 3 runs with Gtech – same road, same conditions (hot). All within 5 minutes of each other. I would have preferred to cool down some in between, but I was concerned about pushing my luck. This is a new concrete 4-lane in an area of new housing. Had Ľ tank of gas, temperature right at 90, a/c off, otherwise usual crap in car/trunk, etc. And this is with SRT intake and L-Tuned exhaust.

1st run: Just floored it, no brake start – ran 6.29 0-60
2nd run: Brake start (@2000) – got 6.36 – some brief wheelspin (WTF – expected to improve)
3rd run: Brake start (@2000) – got 6.41 – again, brief wheelspin only

I quit – at that rate it looked like if I made enough runs I’d be clocking times that a concrete truck would beat.

One thing I noticed was the impression that my 2-3 shift didn’t redline – seemed to come too early. I’ll run some again after SRT “race” ecu and/or TM plugs and pay more attention then.

That’s my story an I’m stickin’ to it.

IS2000

Garnet,

I was studying your wheel / tire set up and got the following:

Spec Sidewall Radius Diameter Circumference Revs/Mile Diff
225/55-16 4.9in 12.9in 25.7in 80.9in 783 0.0%
245/40-19 3.9in 13.4in 26.7in 83.9in 755 3.8%
275/35-19 3.8in 13.3in 26.6in 83.5in 759 3.2%

The Altstadt IV 18 x 8.5 has a weight of 24.5lbs. I know these are not your wheels but I'm trying to extrapolate the possible wheel weight of the 19 x 8.5 Lubeck. On the average, a +1 size increase translates to a 2.5lbs increase on weight. Thus, 18" to 19" results in 24.5 + 2.5 = 27lbs per 8.5 wheel.

Since your rear wheels are +1 inch in width, once again, this translates to a 1.5lbs increase (an inch width increase seems to add less weight than an inch increase in diameter), thus, we have 28.5lbs for the rear 19 x 9.5s.

If we assume your tires to be 29lbs on the average, then we get 56lbs up front and 57.5lbs at the rear. (56 x 2) + (57.5 x 2) = 227lbs. We then subtract this to stock 16s weight of 45 x4 = 180lbs, so 227 - 180 = 47lbs. Multiplying 3 to this figure for actual translated curb weight increase, we get a whopping 141lbs increase! (Mine was just 60lbs)

I do not know by how much a 3.2% diameter increase will slow you down, but rest assured an increase in overall wheel diameter will hamper 0 to 60 times.

If my GS430 with 18s has been slapped a .3secs penalty. I could just imagine yours could go as high as .5 for the 19s and .1 for the increase in diameter.

Lastly, I weigh a hefty 190lbs. Assuming your above 200lbs, then that's another .1 sec!

IS2000

Garnet,

Dude, how does it feel after spending so much hard earned $$$$ and precious time on your car, you end up with stock numbers?

To be fair, my 6.32 stock run was done at 80 temp; however, I did have 1/2 fuel. I guess, GS400 = GS430 alright.

garnet92

IS2000 – like I said, disappointing. The loss of acceleration as a result of larger wheels has been in evidence on the forum for some time. Although, I don’t recall ever seeing it expressed in a 0-60 or Ľ mi. time based on some actual trials.

I expected to better your times since I’m running the SRT intake and LT exhaust (I’d assumed that your ride is stock) – but only @ .1 - .2 sec?

Our results quantify what previously was a seat-of-the-pants estimate. It certainly does bring into play another aspect to consider when thinking about new wheels – are you willing to give up .3-.6 seconds 0-60?

Guess I’ll start saving my social security check for a torque converter.

bitkahuna

iTrader: (20)

Guys, 6.3 seconds 0-60 for a 3800lb car is still AMAZING. And with your bigger rims you look cooler doin' it.

VVT-i

Garnet..thanks for the write up. This help me a lot on the decision for the rims. I agree with bit. your car is look good.