Making a really fast car, not just a faster car.

Diecast64 Friday, 10/17/2014

Jump to last page

So I haven't done a lot of customizing but I'm planning on entering the Sedan Shootout so I've been practicing a bit.  I've modded three cars.  The first two were kind of clunkers. The first car I just fixed the axles with JB Kwik, added a bunch of weight, and practiced stripping paint and then painting.  The car ended up being a bit faster than it was to begin with...but it wasn't that fast to begin with.  The next car I employed my old pinewood derby axle polishing skills.  I polished the axles in a manner that has been successful for my pinewood derby cars, added weight to the car, repainted (I was quite pleased with the paint job this time), put it back together with thoughts of this thing flying down the track.  Again, the car was a little faster than it was to begin with, but not even as fast as my boy's fastest everyday racer, let alone my fast cars up on the shelf! On to car number three.  This time I took a pretty heavy car, swapped out the axles for some FTEs, used graphite, added a bunch of weight, and put it back together.  The car was a bit faster than it was, but only just stayed with my boys fastest everyday racer, wasn't even as fast as the FTE donor car that I took the axles from, and was blown away by my Ferrari F40, which isn't even my fastest car. 

So here's my question (sorry it took so long to get to it), when modding cars, does anybody ever make REALLY FAST cars, or do you pretty much just get cars that are a little faster than they were to begin with? If you have, and don't mind sharing your secrets, I'd love to hear them. :)


Page 1 of 2
View member profile
Traction-Event 10/17/14

If you raced Pinewood Derby you know what to do...


I have been asked this by other members as well, so why not share with all.

By no means does this work every time. I can get photos to represent some of the steps...if needed

(((...I am by no stretch of the imagination the authority on building fast cars...))))

This is what works for me, regardless of wheels or axle type.


1.       Start with a fast car, even if you only plan on using the wheels/axles. If you have 2 of the same car, race them and use the faster cars wheels/axles.

2.       Check the wheels for run out, or side to side wobble. Spin the wheel and watch the surface that will contact the track…you want smooth spinning wheels that do not wobble.

3.       Sand the wheels in a donor chassis, or before you remove them from the donor car. I start with 400 grit sand paper making about 4in ovals to the right and left alternating. I only sand till the car rolls smooth and sounds smooth on a counter top.

4.       Sand the wheels with 1200 grit paper same as above till the wheels are smooth and shiney.

5.       Polish the axle ends where the wheel will ride, I use automotive polishing compound and a Dremel with a cloth disk. I polish one end at a time being careful not to let the wheel slide into the compound.

6.       Choose your chassis, decide where the weight can and will fit. Metal chassis? Debur, and polish anywhere the wheel may touch the chassis. Plastic chassis, same applies with smoothing the chassis. Wash with warm soapy water and dry.

7.       Test fit your axles, weight, body… be sure to have clearance anywhere the wheels can touch the body, weight, chassis.

8.       Test run car if assembly method allows. You have a known fastest car in your fleet? That is your baseline. Swap axles from front to rear and flip them to determine the best (fastest) arrangement.

9.       Setting the axles, I JB Qwik my axles in place. I try to lay a bead of JB along the axle channel in the chassis. Center the axle in the chassis so each wheel has side to side play when set.

10.   Alignment, can’t stress this enough. Fast cars go straight…and do not hug the rail or bounce side to side. With just the chassis and axles JB’d in place find a counter top or your track and adjust the alignment. Slight adjustment here, as too much will bend an axle and ruin your work.

11.   Assemble your car, and recheck alignment. Adjust as needed.

12.   Test run, against baseline car. Swap lanes, multiple runs.

13.   Graphite the axles/wheels, one wheel at a time I use powdered graphite directly on the end of the axle and work it into the wheel opening with a small paint brush. Pull up on wheel and spin grinding the graphite in… repeat on each wheel. Once a 4 wheels are done roll on counter top with slight pressure down to seat in the graphite.

14.    Test run, against original baseline car… improvement? Again multiple runs, swap lanes.

15.   Re-graphite the wheels, same method as above…

16.   Test run against baseline car, 4 runs maximum

17.   Ship it out.


  • Great checklist! — redlinederby
  • i'm clutsy, so i may run an elastic around the axle so i don't get the grit between the wheels and axles. — model40fan
View member profile
72_Chevy_C10 10/17/14

Yup...what he said! :)

Everyone will have their own techniques for doing this. One thing I would ad...DO NOT try to use any form of super glue on your axles to hold them in might think, 'I'll just use a little dab, right in the middle. It won't get out to the wheels'. Believe me, it will make it's way to the wheels and you will ruin an axle!

Also, you might want to make yourself a fixture for holding the wheels straight while the JB Weld is curing. This can be anything, really...I currently have an old, metal cookie tin (the side are straight up and down)...I turn it on it's side and, carefully, set the car on top of it. In theory, this should hold the wheels straight. I'm planning on making a little more permanent fixture for doing this.

My two cents!


View member profile
Stroller 10/17/14

I have no secrets.  It's just that I don't know what I am doing.

  • Im assuming this is the "like" button or "myself as well" button — 2seven
View member profile
redlinederby 10/17/14
Site manager

Good topic that I've struggled with.

When I started racing I did quite a few at-home customs to just try and make a stock car faster, more or less for my own testing and practice purposes. My results were very much like yours, cars were faster but not to the point where I felt like I stumbled across a secret sauce to make them outstanding.

To be fair, I never did an exhaustive super sanding or polishing...I usually just swapped wheels/bodies and added weight. I'm sure going to those extremes would have yielded better results.

I have to say that the whole tuning and testing process was really frustrating. I'd do my best to test a car with it not JB'ed together so I could make tweaks but I never trusted what I was seeing. So I'd go to the trouble of making a car, JB it back together, race only to find it stunk...then felt like I'd have to start over rather than iterate and tweak that same car over and over (which is what I'd love to be able to do).

There was one point where I tried to make a "test car" guide...I think I tried magnets or something...where I could keep the car together tightly but without JB or something that needed re-drilled to make tweaks. I didn't get very far in that idea but I'd like to try it again. If I could devise a system that lets you swap parts/weight without doing so permanently, I could tweak the car over and over in small increments rather than full on redoing. 

View member profile
Diecast64 10/17/14

Thanks for the tips guys. I think probably one of my biggest problems is starting with a fast car...which I haven't.  So far I've used castings that I really like, but they really aren't that fast.  I was hoping to turn my favorite casting into my fastest car.  I figured that their "slowness" was due to wheel and axle stuff, so with all my sanding and polishing I thought I'd have a really fast car, but I'm sure that weight distribution and body design play a larger role than I was giving them credit. 

In pinewood derby it's all about weight in the back to maximize your potential energy. I am guessing it is not the same for Hot Wheels?  Anybody done any experiments with weight distribution?

Traction-Event, when sanding the wheels, are the wheels rolling a bit as you are making your ovals, or are you holding them in place and then turning them a bit after you sand each spot.  With pinewood derby wheels I'm used to slapping the wheel on the drill and spinning it smooth! :)  I think that's where I'm having the hardest time with the transition is that in pinewood derby the wheels aren't stuck on the axle already.

72_chevy, do you have a pic of your cookie sheet set-up, I think I know what you mean, but not sure.

Overall it sounds like I'm on the right track.  I'm sure I just need lots more practice...which means I need lots more free time. ( time? What's that?)

  • Yes the wheels are rolling a bit so as to not flat spot them. — Traction-Event
  • The physics do scale down in size, it's probably just more subtle. — redlinederby
  • If I get a chance this week, I'll make a more permanent jig...and post a pic — 72_Chevy_C10
  • IMO. put your weight nearest the largest diameter wheels, for me that is the rear — model40fan
View member profile
model40fan 10/17/14

IMO... it is not to build a car way faster than the stocker... it is to build the car as fast as you can and have it look cool doing so... pride in workmanship trumps winning here in sloppyville...

now back to your regularly scheduled program...

  • Agreed, my goal is to build a fast custom...not just a wheel swap custom. I have built both, ground up customs waaay more satisfiying. — Traction-Event
View member profile
redlinederby 10/18/14
Site manager

The physics of weight distribution is the same for Hot Wheels as it is Pinewood derby. But that physics isn't limited to weight...rollability of wheels is just as important. You can add all the weight you want but if there's too much wobble or friction in your wheels, it won't do much for you (and vice versa).

Personally, I think the rolling quality of wheels/axles is more important than weight. But I have no real data to back that up outside of what I've done and what I've seen.

View member profile
Traction-Event 10/20/14

This got posted on the LJLRC Facebook page...the secret is out...we build fast

View member profile
72_Chevy_C10 10/21/14

Here's my jig for gluing in the axles...

You put some jb weld in the axle groove, set the axle in...let the jb weld get a little tacky and set the car in the jig upside down  (chassis up)...maybe put a weight on it and let the grooves hold the axles straight

View member profile
model40fan 10/21/14

great idea C10...I want one... I want to cut it in half side to side, drill through holes in one half, tapped holes in the other, slide a couple springs over the bolt shafts between the halves... adjustable for odd wheelbases...

  I may cut a slot down the center for clearance for when the grill is part of the base...

  • I can cast it and get you a resin copy to do whatever you want with it — 72_Chevy_C10
  • Smitty, I could mill a groove down the center before I mold it — 72_Chevy_C10
  • please. — model40fan
View member profile
Traction-Event 10/24/14

photos added, per request.

View member profile
redlinederby 10/24/14
Site manager

Thought on sanding the wheels...I never bothered to test but I often wondered if sanding the wheels, thus roughing them up, would create more friction versus the smooth/polished stock wheels...? I guess not, if everyone does that to make fast cars.

I know there are imperfections in every wheel but somehow I just figured the sanding would be worse. Maybe I didn't sand enough? Seems like you'd have to be careful so your wheels stay balanced.

  • never sanded a wheel... but usually i finish 3rd or worse... — model40fan
  • The type of plastic matters some leave a furry surface... i have waved plastics over a candle to seal the surface but that makes bumps ? — model40fan