Rotating Weight
 

Anyone have any links to results from changing rotating weight?

I have the chance to lose about 28 pounds of rotating weight with the wheels and tires from what im using now (total for all 4 wheels). Just wondering if id actually notice a FE diff or not.

You really don't notice a difference from most things, but that doesn't mean it won't be effective. In this case I would go for it since weight is pretty solidly known to be a bad thing for FE

You probably won't notice a difference but it will theoretically make a difference. the factor is greater the further out from the rotational axis you go so 1lb lighter tires would make a bigger difference than 1lb lighter rims. Most of us are making lots of small changes which all add up to big savings.

If you are paying for it, it probably won't pay you back though. Not that that has stopped me.

http://forums.bimmerforums.com/forum...p/t-79243.html

why kind of driving do you do? might be noticable in town, starting and stoping often, but if you drive mostly highway there would be very little benefit.

aside from mileage, the lower unsprung weight might make your car ride better

if theyre free, try it. extremely cheap, maybe... but returns will diminish quickly as you pay very much at all.


....or DO IT! let us know!

If you planned on getting them anyway, it's worth while, and the MPG is an added benefit.

It's alot harder to change the speed of mass than to maintain speed of mass, which means that lighter rims will, in effect, save your suspension, brakes, and make it so you take less time/fuel to accelerate.

It's not just an MPG thing, it's the cumulative addition that makes things worth while.

i figure i was going to get them anyways for the race car, in 15X10 size for a neon, since that project was scrapped and my daily/race car are now one, 14X6 custom aluminum rims are much cheaper, and will allow me to mount some low RR tires at the same time. Current rims weigh 14.6 pounds a peice, and are shod with 18 pound kuhmo kh16s, in 196/60/14's. New rims should be around 9 pounds, and according to tire rack, bridgestone B381's are 16 pounds a piece in 185/70/14, and should have a much lower RR.

Plus im hoping for a much smoother ride with 7 pounds per wheel knocked off, since the slow lane here isnt paved that great

i think i was mostly curious if anyone had done some back to back testing, however if not i'll do some next summer when i set these up on the car

I definitely noticed a difference when i replaced my 15" steel wheels with 16" alloys. Turns out the alloys weighted 10lb more per corner. I went back to the steelies.

My drive is 5.5 miles (one way) and 22 stop lights. Posted speed is never above 35. So I'm concentrating on weight and rotating weight.
I bought some 13inch Honda VX rims (Craiglist) and then put 155/80/13 on them. I lost 6 lbs per corner.
If I commuted on interstate with an average speed at 55 then I would go with Aero mods.

Currently getting 40mpg on my commute in 1.5L 97 Mazda Protoge.

ya, i mostly freeway drive, however im not really worried about making my money back, at this point its more about doings whats right and reducing my pollution as much as possible

especially after my talk with the california air resource board yesturday, with them pretty much saying they dont care at all about global warming

according to the guy i talked to, theres 2 different types of pollution, smog pollution, which consists of carcinagens, and global warming pollution, which is like co2, and such. They said usually global warming pollution usually goes hand in hand with gas mileage, but often smog pollution doesnt, and that there only real concern is reducing "smog" pollution, the co2 and other global warming pollution there not so concerned about. This was told to me by there director of communications. He said there only worried about stuff that cause cancer and puts people in the hospital.

So lets see, if i got this right, california only cares if i increase the chances a tiny tiny bit that 1 more person might die of cancer, but they dont care at all if i increase the chances that everyone dies from the planets destruction?

Of course my dad, who has a doctorate in physics said the guys just talking out of his rear end, so that they can have control over who can and cant do things. With the CARB guy telling me that they give priority to businesses over people who arent going to sell anything, i agree.

This by the way, was in response to my question of whether theres a way my car will pass smog with the alternator removed, since the obd2 will notice that. Of course the answer is no, if the check engine light is on for any reason, you fail, period, even if its unrelated to smog. For instance, if i unplug my battery, like i would if it died and i change it out, my engine like comes on stating that the batteries been unplugged within the last 50 keyons, which would fail me.

rant over

tried to post 2 days ago, but it wouldnt let me, not sure why

anyways, the cars a 98 2.0L dodge neon RT, comes with a close ratio 5 speed (3.94 FD, .81 5TH)

currently has a cold air intake (that will be replaced soon), 4mm larger throttle body (which will be replaced soon), power steering pump impeller removed (so i can use it as an idler pulley for AC), no muffler (picked up and average of 1 mpg), no passenger seat, and an underdrive pulley that saved 5 pounds from stock, plus no wipers or antenna.

Im currently getting 42.18 mpg average, mostly freeway, at 55pmh.

Imediate plans are to put a different tranny in in 2 weeks (3.55 FD, .72 5TH, will drop my 55mph rpm from 2500 to 2000), along with a new clutch/flywheel that saves 6.25 pounds. I plan to delete the alternator this winter for long trips, and build a bracket to adjust belt tension for the AC with the AC compressor. Then with the 28 pounds of rotating weight lost from the wheels/tires, that should be close to 45 pounds rotating weight lost total on the whole car.

Later this year will also begin the aeromods.

Just curious, what section should i start a project log in?

hm, doesnt want to let me post

anyways, commute is 110 miles round trip, 105 of which are freeway. Ive been getting 42 mpg at 55 on the freeway, pulse and glide in town. However, im looking to improve gas mileage everywhere, since im not doing this hoping to make the money back.

I currently have 5 pounds of rotating weight taken off with the underdrive pulley, and when i swap transmissions in 2 weeks ill be saving another 6.25 pounds with the aluminum flywheel. Then add in that ill be deleting my alternator, and the powersteering, and thats another 4-5 pounds. Plus the 28 pounds from the wheels and tires. And when the engine gets rebuilt, theres going to be some money spent there reducing rotating weight. So in all im looking at maybe 50 pounds of reduced rotating weight. Just wanted to see if there was anything already done on this, if not ill have to test for sure.

Look into bearings and low friction fluids. I've also changed to 0w20 synthetic. I'm thinking about going with something lighter in the transmission. Haven't done any real research but better wheel bearings may buy you something.
Risky option: Since I've also pulled 140lbs of sprung weight out I was wondering if I could get away with a smaller/lighter rear drum or disk setup.
Sorry no real data. Just got a scanguage so any future changes I'll keep track of impacts.

smaller brakes are almost never a good idea, unless they get to the point where they're actually over sized for the vehicle, which is almost impossible, honestly.

Yes smaller brakes are last on my list. Not anytime soon.
Current brakes designed for GVW of full accessory vehicle with 4 passangers and trunk full of luggage. I want to do some more weight savings first then weigh my car. If I'm down 25% or more from GVW then maybe I can afford to loose some brake capability.
I'm an engineer so I can do the calculations and see if I'm still safe. We work on lightweighting Tanks/missile launchers/guns here at work so I'm seeing if I can do it at home on my commuter.

i plan on messing with bearing coatings and different greases as well, im using 5w30 mobil 1, which was recommended as the lowest weight oil to use by one of the engineers who designed the car

unfortunately the transmission is super sensitive, the wrong oil will really make the shifting suck, however, the right oil for it is already thinner then most transmission oils, the right oil is mobil 1 high mileage 10w30

i need to start a project log here, anyone thats been here longer then me, is this the right part of the forum to put it?

If you're using 5w30 M1, you can also use 0w30 M1, because it exceeds the SAE standard for 5w oils. I use it, with no problems. I haven't changed my oil in 10k miles or so.

Same deal w/ the transmission, if you use motor oil in it. You can use 0w30, and it shouldn't affect anything, because, again, the 0w30 meets the standards for 5w30, and the first number is the cold weight.

You can start it here, but if you look through the available forums, there may be a place better suited for it, depending on the specifics of your thread.

ill have to look for the engine oil, that sounds like that should be fine, but im not sure the make mobil 1 high mileage in 0w30 for the transmission. The reason it has to be high mileage is because of the material the synchros are made of, they require the oil to have a high level of ZDP, 16000 PPM or more. The only oil so far to have that amount is the mobil 1 high mileage, the original mopar stuff, and the higher end racing oils labeled for synchromesh transmissions, although those are usually thicker. The mobil 1 has tested at being 99% the same as the original mopar fluid, which was designed specifically for this tranny, with the only differences being mobil one has a slight increase in ZDP, and a slight decrease in sulfer (which was used as an anti-tarnish agent in the 95 model transmissions with brass synchros)

Thanks for the help, and look for a project log this weekend, ill probably put it in here, since its going to be a combination of a lot of different things, from aero to weight reduction to some new things i want to try.

They don't have any 0 weight oils in the high-mileage variety, that I know of. Mobil 1, I believe, only uses syn's anyway, so it's just a matter of getting the lower weight to get that last little bit of efficiency from it.