Battery relocation for HANDLING (not drag) - best spot to mount?

Suspension, Steering and Chassis

  1. MRGTX

    MRGTX Well-Known Member

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    When setting up a car for drag racing, the conventional spot to mount the battery is as far back and to the right/passenger side as possible in the trunk to optimize traction. This definitely has some handling benefits too. This location improves weight distribution significantly...but can guys building for overall handling do better?

    Every modification that I make to my Dart is done with the intention of making it more balanced, more responsive and enjoyable to drive all around...with that in mind, I'm thinking of mounting the battery in the well for the spare tire. Placing the tie-downs toward the front of the well should allow clearance of the gas tank and this has the benefit of lowering the CG of the car a bit and decreases the polar moment of inertia by placing that chunk of mass closer to the center of the car. This location is still aft of the rear axle, even if it's not completely optimal for weight distribution.

    What do you think?
     
  2. famous bob

    famous bob mopar misfit

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    I like them as far back as practical , and on the right side (pass.) , it helps offsett the weight of the driver also , (best for traction).
     
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    • Oldmanmopar

      Oldmanmopar Going left turning right FABO Gold Member

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      If your going for handling keep it in front of the rear wheels. Anything behind the wheels promotes tail swing in turns. Just a thought.

      For drag racing behind the rear is the optimal place.
       
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      • yellow rose

        yellow rose Overnight Sensation FABO Gold Member

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        This^^^^^If you are wanting the best placement, the car needs to be on corner scales, with the drive in place and then put the weight where the car wants it, and not where the magazines say to.

        All engines in these chassis are offset to the passenger side. So many times, the added weight to the right rear isn’t needed, especially if you have some way to add preload to the suspension, like an adjustable traction bar like the Calvert’s, or a coil over suspension.

        Of you have that adjustability, it’s better to make the car as neutral as you can and use the suspension to get the bite you want.
         
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        • 512Stroker

          512Stroker We are all here because we are not all there.

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          Leave the battery in the factory location and invest your money in sway bars, shocks and tires.
          Talk to the Guy's that autocross.
           
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          • Kendog 170

            Kendog 170 Let the boy go !

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            I mounted mine under the speaker package tray on far right. (No cage) Not saying it's right .
             
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            • kursplat

              kursplat FABO Gold Member FABO Gold Member

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              i just like it out of the engine bay. but if you want to do it for handling, get the lightest battery you can and mount it in the center of the car as low as possible
              DSC01432.JPG
               
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              • supertruck

                supertruck Retired Old Fart stock car racer FABO Gold Member

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                Right rear, located as close as possible to being above the axle. Get the weight over the RR tire.
                 
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                • MRGTX

                  MRGTX Well-Known Member

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                  I’ve got the Helwig hollow front sway bar, 1.14” torsion bars, QA1 tubular control arms, QA1 dynamic strut rods Hotchikis leaf springs and their recommended Fox shocks and an Eaton Truetrac diff with 4.10s. I added torque boxes and subframe connectors and still found a net 150lbs or so to shave off of the car without making it look like Swiss cheese. I just had the alignment dialed in according to the more extreme end of the “Skosh” chart which helped a lot! Tires are a sore subject since I’m dedicated to the 15s (don’t get me started) so relocating the battery might be a good next step.
                   
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                  • kursplat

                    kursplat FABO Gold Member FABO Gold Member

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                    you can get sticky 15's :D
                    EAGLES, PIRELLIS, KOOKS and TOYOS ONE, TWO, THREE, FOUR.
                     
                  • MRGTX

                    MRGTX Well-Known Member

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                    True. These are great if you have a Civic or a Miata. They’re 2” short for most of us here.
                     
                  • 69hemibeep

                    69hemibeep Well-Known Member

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                    Leave it alone the engine is offset to the right this helps counter that if you are after balance
                     
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                    • kursplat

                      kursplat FABO Gold Member FABO Gold Member

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                      ya, i saw your other thread where you mentioned what tire diameter you were trying to keep, after this. i know you're trying to stay with 15's, and i love the wheels on your car, but you've done a lot of suspension upgrades and as you said
                      you've kind of hit the wall with trying to stay within your tire choices.
                       
                    • MRGTX

                      MRGTX Well-Known Member

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                      You are absolutely right about that. Honestly, I’m ok with not having maximum grip. I know I won’t get that so long as I cling to the “proper” (my opinion only) diameter wheels...but a tire that is dynamically stable, predictable, and responsive is good enough for me.

                      I hold out hope that Avon will bring over those sticky 60 series tires or that some other brand will come up with something decent. In the mean time, we get what we get...and it just emphasizes the need to optimize weight distribution, IMO.
                       
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                      • RogerRamRod

                        RogerRamRod The Older I Get, The Faster I Was

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                        I know this is an older thread, but did you ever choose a location and try it? I was hoping to see some real world experience with different locations from some that track their cars like 72Blu, Autoxcuda, or Peter Bergman, (im sure there's others, but those come to mind)
                         
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                        • autoxcuda

                          autoxcuda Well-Known Member

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                          it’s a small change moving to different location and getting measurable results (track times) and data acquisition.

                          It’s one of those little things that’s known by physics and engineering. You do a bunch of little things and it adds up. But individually might be tough to measure (especially home build)

                          There’s a few things happening:
                          -one is the inertia effect of the car swinging or yawing around its center or gravity (top view)
                          -another is the weight transfer from center of gravity height (side views)
                          -another is tire loading weight balance on scales of (top view) *this tends to be the most significant and measurable change.

                          This diagram might help...

                          927A2E6E-70AA-4985-B6E4-EB8146F60A78.jpeg
                           
                          Last edited: Dec 29, 2020
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                          • Kendog 170

                            Kendog 170 Let the boy go !

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                            I put mine under right speaker. Makes my trunk clean. Fiqure weight on top of rearend . Weight on right side to accomadate no passenger. My car is just a driver.
                            Messy pic shows Battery.

                            Trunk.jpeg

                            Trunk1.jpeg
                             
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                            • 72bluNblu

                              72bluNblu FABO Gold Member FABO Gold Member

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                              Except almost of those also have a sub-200 treadwear. Which may be street legal in some cases, but they're not really streetable tires. The Toyo R1R, the only one with a 200 treadwear, has it's widest 15" option as a 225/45/15, which is only 23" tall. And is still narrow for handing.

                              Even for an AutoX car the sub-200 treadwear can be an issue, because a lot of classes that you would AutoX one of these cars in require 200 treadwear or higher (CamT for example). Sub-200 treadwear tires put you in really competitive classes.

                              Exactly. If you want to locate the battery perfectly for handling, a set of corner scales would be the way to do it.

                              Short of that, all of these cars are nose heavy unless you've done some really serious weight management. Even then, probably still nose heavy. So if the best handling you can get is the goal, you want a front/rear weight distribution as close to 50/50 as you can get it. Which means putting the battery in the trunk. Where exactly you put it in the trunk would be a job for the corner scales again. But my general inclination would still be the passenger side for most of these cars.

                              This is Tomswheels Valiant, which had a cage, the battery relocated to the trunk on the passenger side behind the wheel tub, fuel tank in the usual location, WITHOUT the driver. Small block car as well.
                              weights copy.jpg

                              On this it shows the passenger rear as heavy, but, with the driver in the car that would definitely change. And the car is still nose heavy. This is just one example, not every A-body would match this, but as a general idea I would still suspect the trunk on the passenger side would be the best option for most cars. That's where mine is, but, I did that without scales or anything so it's no more scientific than what I just said.
                               
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                              • kursplat

                                kursplat FABO Gold Member FABO Gold Member

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                                ya, he had another thread when this started this where he was adamant about staying with 15's. as for 200 tread wear, i don't want my handling car with tires over a year old anyway. might as well get them sticky and wear em' out :lol:
                                 
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                                • 72bluNblu

                                  72bluNblu FABO Gold Member FABO Gold Member

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                                  Which is fine if you only drive in dry and warm conditions or your car is a track car only. But if your car sees wet weather, or temperatures below 50°F those sub-200 treadwear tires will be worse than having all seasons in the summer. Tires designed for track use work best at "normal" track temperatures, and heat cycling is an issue for those tires. So yeah, if you're talking track only fine. But for street use, no thanks. The performance will fall off rapidly as the heat cycles increase, and with any kind of colder temperatures.

                                  Even the Falken Azeni's I'm running now are probably marginal for year round use. I was happily surprised the other day running them in the rain as they did pretty well, but I'm not so delusional as to think they're the best for rainy driving. Just that even as a daily driver they'll see a lot more dry conditions than wet. Always a trade off.
                                   
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                                  • kursplat

                                    kursplat FABO Gold Member FABO Gold Member

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                                    fortunately i don't have to worry too much about that here, and the OP is in Connecticut, so he's probably not driving it around right now. :steering:
                                    i ran those Falkens (older compound probably cause it was a few years ago), on my sti for auto-xing and daily driving. worked well, down here. like everything about these cars, always need to take your specific situation into account.
                                     
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                                    • autoxcuda

                                      autoxcuda Well-Known Member

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                                      That purple valiant calc’s to:
                                      54.1% front
                                      45.9% rear

                                      here’s my car: no cage, without driver, without spare tire, front mounted battery.

                                      1/2 tank of gas +/- 1/4 tank... gas load is a big deal. I should have noted it better.

                                      57.1% front
                                      43.9% rear

                                      CudaScale1_17_15Sm09.jpg
                                       
                                      Last edited: Dec 29, 2020
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                                      • A56

                                        A56 MoParAffliction FABO Gold Member

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                                        I wanted to relocate my battery for similar reasons as the op, but found that the left rear of my Fastback was best because it didn't run interference with the factory jack location and since the starter was on the left side running the cable just made sense to me.
                                         
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                                        • autoxcuda

                                          autoxcuda Well-Known Member

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                                          I’ve never used the factory jack. I don’t trust them not bending my bumper. Any distance I bring the smallest HF aluminum floor jack. Or I’d rather bring a small bottle jack and wood blocks.

                                          I have an aluminum Ford donut spare with center opened up.
                                           
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                                          • supertruck

                                            supertruck Retired Old Fart stock car racer FABO Gold Member

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                                            Battery should be in right rear IMHO, as close to directly above the rear axle, or slightly ahead of it, as possible. Not behind the rear axle. That location won't show a mistake on the scales but it acts sort of like an un-sprung weight in actual use. Similar to how a trailer would act if you put all the weight behind the wheels instead of on top of them, but on a much smaller scale, of course. The big issue is that most folks don't have the experience to notice a big difference when a battery is moved around. Some do, but most don't.
                                             
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