Opinions: Hubcaps and MPG...

Discussion in 'The Daily Grind' started by law_dawg, May 19, 2008.

  1. law_dawg

    law_dawg Hypermile Poser

    So, I'm just wondering everyone's opinions on this subject. We've all seen the aerodynamic "racing" hub caps on the market (http://jaygroh.dreamhost.com/priuschat/hubcap1.jpg). But I am wondering about a possible cheaper alternative:

    Would simply removing one's hubcaps improve MPG?

    Here's my thought about it: The lighter the wheel, the easier it is for the engine to turn the wheel. Now, given that the hubcaps on most cars would only weight a few ounces, wouldnt the spinning motion of the wheels make a pseudo-increase in "weight" for the engine to move (i.e., like how a spinning wheel held at the axel seems to resist movement for than if not spinning [angular momentum?])?

    I dont know, just getting thoughts, or results if anyone has tried...
  2. lyekka

    lyekka Well-Known Member

    I was toying with the idea of forming polycarbonate covers for my wheels to increase the aerodyamics while retaining the stock look.
  3. Xringer

    Xringer Older Member

    I don't think it has much to do with weight.

    I've been wondering about the effectiveness of those disc wheel covers too.

    I read somewheres that if the wheels are out in the air flow the disc work well.
    This guy could use them..

    But, if they are in a deep wheel well, maybe just an air-dam forward of the tread will do the job?

    I've been looking at the screw-on disc and wondering just how you put air in the tire?? ;)
  4. TheForce

    TheForce He who posts articles

    Since losing one of my caps in October I have not put them back on my car yet. I figure this would be a good time to collect some data. I don't think I have enough to make any conclusions. If there are some improvements they are very very small. Same with negatives.
  5. some_other_dave

    some_other_dave Well-Known Member

    Most wheel covers these days are lightweight plastic. The extra weight is pretty small, so the impact on FE should be pretty small.

    Most wheel covers also tend to have bumps and ridges and holes and such, so they are not very good for aerodynamics. They'll create turbulence and therefore drag.

    The flat covers (like the pizza pan ones that one Civic owner on EcoModders made) should be better for aero. They shouldn't add much weight, either.

    If you could switch to a very light wheel and tire combo, and also use flat aerodynamic wheel covers, that might be the best of both worlds. But lightweight wheels tend to cost quite a bit; a $1000 set is often regarded as being "cheap"... The cost/benefit ratio probably doesn't justify buying them.

  6. lamebums

    lamebums Member

    I think it depends on your driving--if it's mostly highway you'll see a benefit, although pretty small.

    I think it would help with being able to identify your car though. :)
  7. bellaggio1770

    bellaggio1770 Member

    I have access to a laser cutter, so I am able to cut out perfect plastic discs with holes for screws etc...

    The only information I am missing is: How to attach it to the wheel? I heard someone uses zip ties and even glue, but that just sounds very dangerous to me. I also do not want to drill into the wheels....

    I have 5-spoke wheels with 5 lug nuts each. Could anyone tell me what the best method is?

    Thanks !
  8. donee

    donee Well-Known Member

    Hi All,

    I have made aluminum flashing covers for my Prius trim rings. This gives a flush hub cap, similar in looks to what is shown on the hybridefects.com web site.

    This weekend I had my tires rotated, so I pulled of the trimring/flushcaps and cleaned up the wheels before taking them to be rotated. While off, I did some coasting tests. I coasted down a hill to about 45 mph. At the base of the hill, the road was level, and I looked at the coast down from peak speed. It seems to me that with the flush caps the car would maintain within .1 mph (I have mycanscan on my car, which gives speed in tenths) for about 3 or 4 seconds. Without the caps the speed would peak, and start dropping in about a second. I did four runs with and four runs without the trmiring/flushcaps.

    Not totally scentific, as I do not want to do the warp neutral on my car much beyond 45 mph, and do not want to burn 100 miles of gas to get a mileage with/without out of the noise.

    I personally think this is allowing me to hold a better speed in SHM mode, than others have reported. Something like 53 mph, versus about 50.
  9. some_other_dave

    some_other_dave Well-Known Member

    The guy I mentioned before (white civic over on Ecomodders) bought some cheapie plastic wheel covers, chopped out most of the cover, and glued and possibly screwed the pizza pans onto what was left. I think the aftermarket covers are held on with spring clips.

    You could either follow his lead, or look at what the wheel covers use for attachment and fabricate an equivalent of your own.

  10. Xringer

    Xringer Older Member

    Thanks! You gave me an idea!

    I could cut out 7 little triangles from thin sheet metal or plastic and use them to cover
    up 7 of the 8 holes in each of my rims.. Attach them with epoxy or tape them down.
  11. Takashi

    Takashi FUD

    Shaving a few lbs off a plastic hub cap or making it more aerodynamic will have minimum impact on fuel economy. The ability for a driveshaft to rotate a wheel depends on:

    1) The 'stickyness' of a tire to the road. The more friction between the rubber and the road the more energy is needed to rotate the tire. This is why one should never use a winter tire when outside temp more than 6oC. Winter tires stick to dry roads like there is no tomorrow and it will suck the fuel economy out of you.

    2) The weight of the rim. For those who you who are using steel rims, your 4 steel rims are hurting you because those steel rims are very heavy. For those of you who use alloy rims you might have a weight advantage. The best way to find out is to take the rim and wheel off the car, wash it, dry it, and weight it on a bathroom scale.

    There are some other ways to make sure you are getting the most of your fuel economy.

    3) Make sure your wheels are well balanced. Cutting sheets of plastic to cover holes on your metal rim will NOT work. Not only you are adding more mass to the rim, you are also changing the balance of the whole tire. If you throw in a hubcap on your rim, make sure it is weight balanced. Similar to a ceiling fan, if your hubcap is not balanced it will add extra vibrations on your wheel which could lead to uneven tire wear, damaged drive shaft, and $$ repairs.

    4) You could ditch the steel rims on your car and replace them with lighter alloy rims. Not only it can make your car look more sexy, it's lighter so it gives you a more competitive edge on fuel economy
  12. vtec-e

    vtec-e Celtic MPG Warrior

    You are a handy man to know!

  13. basjoos

    basjoos Well-Known Member

    On my car, I got 4 pizza pans from WalMart, trimmed and crimped them to fit flush with the edge of my wheels, spray painted them black to match the tires, and then drilled and tapped three 8-32 holes on the raised portion of the wheel (just outside of sunken area where the lug holes are) and mounted the hubs on the wheels.
  14. Xringer

    Xringer Older Member

    "You could ditch the steel rims on your car and replace them with lighter alloy rims."

    Since I'm driving less than 1,000 miles a year now, how long after I replace my steels with
    typical alloy rims, will I break even on the gas savings? ;)

    I had not heard about "The 'stickyness' of a tire to the road".. But I have heard that
    inflating the tires up to the sidewall pressure would cut the tire's foot print, or contact
    surface touching the road. Which can really help with FE..
  15. Takashi

    Takashi FUD

    The idea is very easy to understand. Basically, the more sticky the tire is, the more energy is needed to overcome the friction in order to get it rolling on the road. It's like trying to pull a piece of masking tape off a table vs. putting a piece of duct tape off the table.

    Anyway, rather than over-inflating your tires in risk of uneven tread wear, hydroplaning on wet roads, changing the road handling characterstics of your car, and the tire blowing up when you hit a pothole or any other road hazards, won't it be better to change your tires and rims (which is the real source of problem)? It's more effective in the long run.

    Since you are driving < 1,000 miles a year, won't it be better if you just ride a bike, walk, or rollerblade? You will immediately break even on your gas savings. (Oh yes, I am starting to walk more and drive less)
  16. Xringer

    Xringer Older Member

    I get you.. Like when you have those wide flat racing slicks with the soft gummy rubber..
    No problem there, I ride on regular old Michelin HydroEdge tires..

    I never said I was going to over-inflate my tires. I'm using the 44 PSI per the side wall.

    I think hydroplaning is more due to low pressures, not higher pressures..
    Check out the pics..

    And, of course the handling is much better with higher pressures too..

    Check this out.. Driving Under Pressure http://www.cleanmpg.com/forums/showthread.php?p=102887

    From what I have learned about tire pressures in modern tires, it's low pressures that
    get people killed. So, I'm going to take a chance (like many other Hypermilers) and go with
    the max pressure per the sidewall rating. If people start reporting safety or wear problems,
    with Michelin HydroEdge tires, I'll drop it back to under 40 PSI...


    My wife and I bike everyday we can. So far this year (like last year), I have more miles on my bike, then my car.. :woot:
  17. Vooch

    Vooch Well-Known Member


    Air flow around the brakes is extremely critical to their function - Auto Engineers spend a lot of effort making certain that the brakes get enough cooling - Brakes that get too hot will perform worse - a lot worse.
  18. Xringer

    Xringer Older Member

    So, why aren't there any warnings in car's manuals about changing hub cabs??
    How are so many people getting away with installing solid disc covers (moon-eye etc)
    hubcaps on their cars for better fe??

    How can these guys http://www.kleenwheels.com/kleenwheels_install.htm stay in business?
    Shouldn't people be suing them by now??

    I'll tell you what I think.. a lot of Auto Engineers spend a lot of effort making certain
    their cars are put together with the lowest cost parts they can get away with..
    But, rule #1, the brakes have to work well under just about any circumstances.
    (Even if you do buy new hubcaps)..
  19. AbACUZ

    AbACUZ Juniorest member

    you are completely right Xringer , a device that functions as a heat generator will allways work perfectly no matter if the cooling sources are covered or not.

    Hot rods with moon eyes , and a toyota corola have the exact same aedynamic shapes , and if you can install moon eyes on a 1930's car, than a 2008 car will be the same too.

    Ang after checking my manual 100 times , i read nothing about replacing my airbags with a bag of nails, nothing, so if its not writen on the manual, it must be ok. and airbags must work well under any circimstances.
  20. Xringer

    Xringer Older Member


    Quick jump out of the way, his brakes are going to overheat!! :)

    If the steel rims on my CRV had some kind of air turbine function to blow air over the brakes,
    I might be worried. But, they are just little do-nothing holes.
    Maybe they are for looks, maybe they add some strength to the rim.
    If they have any real function, it's not cooling the brakes.

    I know that at least one hole is needed for the air stem, But the rest of them seems
    like a lame attempt to make the rim look like a fancy alloy rim..

    There is plenty of room on the backside of the rims for air to circulate over the brakes.

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