4.10 gears installed last Saturday

mustangdave said:

Just a thought: giant wheels (20") look cool but slow you down. My stock 18 inchers turn more revoultions for every turn of the driveshaft. My 3:55's could be faster than 3:90's or 4:10's with bigarse wheels.

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That's why they make 4:56 gear sets.
For us with the bigarse wheels

I love my 4.10s and they still help get me down the road fairly well being they're turning 29.2" tall rear tires now I run 26.5" tall MTs at the track.

I love my 4.10s. I lost about 2-3 MPG, but who the hell cares. If I wanted more MPG, I wouldn't have installed 4.10s... Or I'd have bought a Prius.

Haha true that Poopdawg! But it is nice having fun with the car and still not filling up until after 325+ miles!

Wheels

Everyone is going to 19" and 20" diameter wheels these days. They are just bling. Go to any race track around the country and you won't find any true racer running 20" diameter wheels. The reason is simple, big diameter wheels are too heavy!

They increase unsprung weight which hurts handling, and they increase the rotating inertia which hurts acceleration.

Also, it is difficult and expensive to find truly high-performance tires in the 19" and 20" diameter sizes.

Then you add a big brake kit.....adding even more weight....

Larger wheels with 'thin tires' and stiff sidewalls increase handling capabilities. No arguing that 'big' wheels are no good for drag racing.

They increase unsprung weight which hurts handling.....This means a heavier wheel takes longer to return to full ground contact after a "bump" ....i.e a heavier wheel has less ground contact therefore less capable handling no matter the tire type, weight is the key. It also takes more energy to turn heavier objects so lighter objects turn faster at equal effort.

If you place a stiff sidewall tire on an 18 inch wheel it will outperform a the same stiff sidewall tire on a 20 inch rim because it is lighter, requires less power to turn and maintains better road contact....

Tirerack has a good article on wheel weight.....and diameter

17" x 8" alloy wheels (brand name withheld) fitted with 245/45ZR17-sized Pirelli P Zero Asimmetrico tires

The heavyweight aluminum alloy wheels used in this test were selected because they were designed to emphasize a trendy fashion style without regard to overall weight. BLING! The heavyweight aluminum alloy wheels on our BMW test car weigh 27 pounds each (ten more pounds per wheel than the lightweight wheels).

When combined, the weight of the Plus One-sized P Zero Asimmetrico tires mounted on the heavyweight alloy wheel results in a 48.5 pound Tire & Wheel Package which is about 7 pounds heavier than the stock combination.

On the road, this combination was only praised for its ride quality. Our experience showed that the heavyweight wheel's reluctance to be moved as the vehicle rode over expansion joints, patches and potholes actually damped the impact harshness transmitted to the suspension, and forced the tires to absorb more of the jolt. However, when it came to steering feel and responsiveness, heavyweight wheels made the tires less communicative and responsive at highway speeds. On the track, this combination found no praise. It felt heavy and lethargic, and actually reduced the feedback the tires normally transmit to the driver, making the vehicle more difficult to drive at the limit. This made it more difficult for the driver to know how much input was required and reduced the vehicle's ability to transform the driver's input into performance. For that matter, many of our team members compared the feeling of running on heavyweight wheels to that of jogging with ankle weights or hiking with field boots. You really feel the difference when you take them off. The car equipped with the heavyweight alloy wheels and Pirelli P Zero Asimmetrico tires benefited from the handling of the tires but couldn't match the performance of the lightweight combination, and its lap times fell between the other two combinations tested.

While we expected to feel the gyroscopic effects of wheel weight at highway speeds (where at 60 mph they revolve about 13 times a second), we were rather surprised at their influence on the car's feel at the lower speeds on our performance test track drive. Additionally, realizing that the impact of heavyweight wheels would increase as top speeds climbed on a race track (where at 150 mph they would revolve about 33 times a second), it left little doubt as to why professional race teams spend thousands of dollars for wheels which minimize weight while retaining strength.

Finally, we monitored our test car's fuel economy using their onboard trip computers during our road rides. Covering a total distance of just over 350 miles, the three vehicle's average speeds were virtually identical (all within 3/10 of 1 mph). During that time the BMW 3-Series equipped with its Original Equipment Grand Touring Michelin Energy MXV4 Plus low rolling resistance tires averaged 22.8 mpg. The vehicle equipped with the Plus Size Pirelli P Zero tires on lightweight wheels averaged 21.5 mpg, while the Plus Size Pirelli P Zero tires on heavyweight wheels dropped to a 21.1 mpg average.
Vehicle Combination Average Speed

Average mpg

BMW 3-Series equipped with
Original Equipment (16") Stock 38.7 22.8

BMW 3-Series equipped with
Plus One (17") Lightweight 39.0 21.5

BMW 3-Series equipped with
Plus One (17") Heavyweight 38.8 21.1

Rotating mass does reduce performance, I agree. The sidewall on a 20" wheel vs a 18" wheel, if both have the same overall diameter, is going to be stiffer. It will offer better handling. How much? Probably very minimal. Look at how many exotics have large wheels. Now, throw in the variable of a forged 20" wheel which is going to be light weight and use a stiff sidewall tire. It's the best of both worlds.

The weight difference between a 18" wheel and 20" wheel is very minor. If the wheel is bigger, than the tire is going to be smaller which means the tire will weigh less. If the wheel is smaller, than the tire is going to be larger which means the tire will weigh more. It's all about trade offs.

I've seen the results of power between factory 17" wheels and tires and a cast 20" wheel with a Nitto NT555. It's only 4 rwhp, not much IMO. In the end it all comes down to doing what you want because you're the one who pays the note.

OK

Just read the article above....this isn't personal, or about costs, its about performance, its just physics, not a personal opinion....lighter wheels outperform heavier wheels in acceleration, handling and fuel economy.....

mustangford289 said:

Just read the article above....this isn't personal, or about costs, its a performance, its just physics, not a personal opinion....lighter wheels outperform heavier wheels in acceleration, handling and fuel economy.....

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Don't worry, I'm not taking anything personal. Discussing things like adults is what these forums are for .. I agree though, it being a larger wheel has nothing to do with it in reality. It's about the overall weight and tire stiffness. (Not talking about drag racing, that's a whole 'nother ball game !!)

mustangford289 said:

They increase unsprung weight which hurts handling.....This means a heavier wheel takes longer to return to full ground contact after a "bump" ....i.e a heavier wheel has less ground contact therefore less capable handling no matter the tire type, weight is the key. It also takes more energy to turn heavier objects so lighter objects turn faster at equal effort.

If you place a stiff sidewall tire on an 18 inch wheel it will outperform a the same stiff sidewall tire on a 20 inch rim because it is lighter, requires less power to turn and maintains better road contact....

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+1

20" wheels look great on our cars, but...I'd rather get better performance (and yes, it's VERY noticeable)...and get lightweight (forged) 18s. The difference in weight is immediately noticeable. Everything from acceleration to turning, braking....is improved. Who wants 75+ lbs. of unsprung, rotating weight in each corner?

Exotics have large wheels, sure. They even have offset diameters and widths front to back. But they also have close to 500+ hp in them. I suppose if you're rolling with 400+ hp, acceleration performance won't be noticeably hampered, but if you're going with bolt-ons only, you'd want to keep as much power as you can and not give it up to bling.

Or maybe you do.

bigs and littles

I know most go with the giant dia (19-20-22) rims and short sidewall, but I'm old school drag racing and was wondering how much of a prob it is to run 15-16 inch Welds/Bogarts etc. Are the rotors able to clear these? See Justin Burcham's Silver stang.