Username or Email Address
Do you already have an account?
Forgot your password?
  • Log in or Sign up

    VWVortex


    The Car Lounge
    Results 1 to 11 of 11

    Thread: FWD weight balance - better than you think...

    1. Member RogueTDI's Avatar
      Join Date
      Dec 12th, 2002
      Location
      USA
      Posts
      14,798
      Vehicles
      2010 Golf TDI 4DR MT6 SB 1989 AW11 MR2 4AGE 150whp 2250lbs
      05-12-2012 08:07 PM #1
      Was just thinking about this. Take a Mk6 GTI, empty weight distribution maybe 59/41 - pretty good as is, consider everything is up front.

      Now. Realize that all loadings (cargo, passengers, fuel) only help weight distribution.

      Running the numbers, for a 3100lb curb weight, for the most optimal case of heavy trunk load (200lb) some heavy passengers in the back, weight distribution goes to around 52/48.

      For a typical setup, 200lb driver, 40lbs "junk in the trunk, full fuel load (80lbs), gets balance to around 55/45, pretty close to a lot of FR cars.

      True, we wont be tracking a car full of people and cargo, but considering thw primary purpose of this arrangement (practical benefits), its nice to see this added benefit - the car loads the wheels nicely in its most typical usage. Just something to think about next time youre thinking "fwd has crappy weight distribution."

    2. Member zhenya00's Avatar
      Join Date
      Aug 7th, 2003
      Location
      Ithaca, NY
      Posts
      6,670
      05-12-2012 08:23 PM #2
      Can you really assign the weight of the driver fully to the rear axle? It's not in a terrible location, but it's generally closer to the front than the rear. Also, not too many people are going to be driving a GTI with spirit when loaded with passengers and/or 200lbs of stuff in the trunk.

      FWD cars with forward weight bias can be made to handle fine - but there is a reason there are so many RWD 'balanced' converts. You're not likely to get the feeling of a pendulum with the pivot point at your hips that a truly balanced car gives you. And with RWD, you effectively have a second steering device in the gas pedal.

      Also, you're ignoring the fact that as soon as the car is in motion, the balance point changes. As soon as your brake for a corner, the weight shifts forward, making a front heavy car severely under-steer, and even a 50/50 car under-steer on corner entry. This is why many race cars have a rear-ward bias.
      1987 Mercedes 190E 16v Cosworth
      1997 Volvo 855 T5
      2010 Volvo XC90
      2013 Prius Plug-In

    3. Member RogueTDI's Avatar
      Join Date
      Dec 12th, 2002
      Location
      USA
      Posts
      14,798
      Vehicles
      2010 Golf TDI 4DR MT6 SB 1989 AW11 MR2 4AGE 150whp 2250lbs
      05-12-2012 08:59 PM #3
      All my weight assignments are accurate. Its pretty simple. Assume front seats are 50/50 front to rear, back seats are about 3/1 toward rear. Cargo space is from 100% or higher to rear axle (just assume all on rear wheels, to keep it simple)

      Of course, the effects of passengers and cargo similarly benefit FR cars. However, as compared to FR layouts, the available rear luggage and passenger space is a little better. Also FR sedans generally are heavier than FF sedans, so their balance isnt effected as strongly per unit payload.

      As to dynamic inertial effects, it is no different than any other drivetrain layout. 50/50 is 50/50, regardless of drivetrain, in terms of handling, more or less. Of course, complications that arrise from driving the front wheela.are always there. But im talking about handling balance not so much drive train function. Certainly im not claiming FWD is somehow super similar to FR.

      Also, forward dynamic weight transfer does not cause understeer, but oversteer. No inertia(mass) is being transfered, just weight(load).
      Last edited by RogueTDI; 05-13-2012 at 02:26 AM.

    4. Geriatric Member SSLByron's Avatar
      Join Date
      Jul 29th, 2004
      Location
      Annapolis, MD
      Posts
      37,112
      Vehicles
      '13 Focus, '08.5 MS3, '97 Wrangler, '90 Miata
      05-12-2012 10:11 PM #4
      You want frontward weight bias in a FWD car anyway because you want weight over the driven axle. Weight = traction. Ideally, you keep at least 50% or more of the weight forward under hard acceleration to maximize front-end bite.

      Weight distribution on factory car is kind of a silly metric. Yeah, it has real-world implications, but by itself it's a fairly insignificant stat for performance cars.
      Looking for a ratty Miata? My '90 is for sale.
      http://www.speedsportlife.com
      Quote Originally Posted by mhjett View Post
      4+ pages and at least 1 death threat in a compact-car comparison test thread - oh wait, this is TCL.

    5. Senior Member Aonarch's Avatar
      Join Date
      Dec 4th, 2006
      Location
      US 129/ GA SR 60
      Posts
      33,678
      Vehicles
      The Standard of the World | Feed Your Restless
      05-12-2012 10:13 PM #5
      My issue is my 2012 GTI has a stripped interior. Most of that weight saved is from the rear, which only throws the balance out of wack. The only thing you can really do to the front is washer reservoir delete and battery relocation.
      Semper Fi | USMC '06-'14 | 0311 | 0331| 0933
      Aonarch's Blog!

    6. Member
      Join Date
      Jun 13th, 2004
      Location
      CA
      Posts
      1,807
      Vehicles
      '05 S2000, '90 CRX
      05-12-2012 10:31 PM #6
      You have any pics of that? ^^^

    7. Member
      Join Date
      Jun 15th, 2010
      Location
      Bergen County NJ
      Posts
      1,215
      Vehicles
      N54
      05-12-2012 10:39 PM #7
      Quote Originally Posted by RogueTDI View Post
      Was just thinking about this. Take a Mk6 GTI, empty weight distribution maybe 59/41 - pretty good as is, consider everything is up front.

      Now. Realize that all loadings (cargo, passengers, fuel) only help weight distribution.

      Running the numbers, for a 3100lb curb weight, for the most optimal case of heavy trunk load (200lb) some heavy passengers in the back, weight distribution goes to around 52/48.

      For a typical setup, 200lb driver, 40lbs "junk in the trunk, full fuel load (80lbs), gets balance to around 55/45, pretty close to a lot of FR cars.

      True, we wont be tracking a car full of people and cargo, but considering thw primary purpose of this arrangement (practical benefits), its nice to see this added benefit - the car loads the wheels nicely in its most typical usage. Just something to think about next time youre thinking "fwd has crappy weight distribution."

      Good points, but you still can't steer with the throttle, and now you have a car that weighs around what 3,600 - 3,800 lbs sporting 225 rubber?

      FWD cars handle fine, but its tough to replicate a near 50/50 weight dist RWD car no matter how hard you manipulate the numbers. It just feels different, and although this may sound obvious to most, before I owned my first RWD car I never realized just how different. For me it was kind of like finding the light.

      I will never own a FWD car with sporting intentions again, it really is doing it wrong even though they deserve respect on some level.


      /RWDsnob

    8. Member RogueTDI's Avatar
      Join Date
      Dec 12th, 2002
      Location
      USA
      Posts
      14,798
      Vehicles
      2010 Golf TDI 4DR MT6 SB 1989 AW11 MR2 4AGE 150whp 2250lbs
      05-12-2012 10:51 PM #8
      Oh i totally agree FWD will never be FR or MR. Im just pointing out something interesting.

    9. Member
      Join Date
      Jun 15th, 2010
      Location
      Bergen County NJ
      Posts
      1,215
      Vehicles
      N54
      05-12-2012 10:57 PM #9
      Quote Originally Posted by RogueTDI View Post
      Oh i totally agree FWD will never be FR or MR. Im just pointing out something interesting.
      Indeed, never thought about that before you pointed it out. A full tank of gas alone can help - x gallons times 7 lbs per gallon..

      Just ~14 gallons of gas helps the dist by a good amount..

    10. 05-13-2012 06:25 PM #10
      Larger Battery in trunk?

    11. Member horribleR's Avatar
      Join Date
      Feb 1st, 2010
      Location
      CA
      Posts
      3,624
      Vehicles
      Miata, Miata
      05-13-2012 07:00 PM #11
      I never knew that there were 'rwd dick riders'.

    Posting Permissions

    • You may not post new threads
    • You may not post replies
    • You may not post attachments
    • You may not edit your posts
    •