To Narrow Front or Not on Four Wheels Touching Car

[mehiggins101]

I see a lot of people narrow the front end 1/16". Does this help on a four wheels touching car? If so, which side or 1/32" off both sides?

[Vitamin K]

I see a lot of people narrow the front end 1/16". Does this help on a four wheels touching car? If so, which side or 1/32" off both sides?

If you're building a 4-wheel rail-rider, I think it makes sense to narrow the front end on your dominant front wheel. This would be the wheel that is steering into the rail, as you want to insure that the inner edge of this wheel is the only thing that ever contacts the guide rail.

On the other hand, if you're building a four-wheeled straight runner, you wouldn't have any reason to narrow the front end.

[Darin McGrew]

On the other hand, if you're building a four-wheeled straight runner, you wouldn't have any reason to narrow the front end.

If you're building a four-wheeled straight runner with the weight to the rear, would it help to narrow the front (or widen the rear) on both sides, so the lightly weighted front wheels are the ones touching the rail?

[mehiggins101]

On the other hand, if you're building a four-wheeled straight runner, you wouldn't have any reason to narrow the front end.

If you're building a four-wheeled straight runner with the weight to the rear, would it help to narrow the front (or widen the rear) on both sides, so the lightly weighted front wheels are the ones touching the rail?

x2 That's exactly what I'm wondering

[bracketracer]

If I had to build a four wheel touching straight runner I would narrow both sides on the front, but I would prefer to build a railrider and narrow the dominant side only if the rules allow. Either way you go, I would give the car a trial assembly before I cut anything off and see how much you need to remove to center the rear wheels over the rail, then take it apart and trim it.

[Speedster]

Yes, narrow the car at the front Dominant wheel 1/16". Vitamin K has already said why this is done. It doesn't matter whether it is a 3 wheeler or 4 wheeler. This is the way we set up our 4 wheeler ( Courtesy of Sporty). Right front wheel (Dominant) is set with Positive cant and Toe-in. Left front wheel is set with Negative cant and Toe-out. Rear wheels are set with Negative cant which will cause the wheels to migrate to the heads of the nails and stay there. This can be accomplished even if your rules say " Wheels must sit straight up and down". There is slop in the wheel bores. The slightest angle on the wheels will affect their direction. You can find detailed info on this by using the search function. We build a 3 wheel rail rider first and get its best time on our Best track. Once we have that we adjust the Left front wheel down with Negative cant and toe out so it just touches the track. The toe out keeps the wheel off the rail. Check your rules. If they are lenient there is a recommended amount of cant for the wheels.

As for a straight runner, I suspect there is no such thing. You might get the car to roll straight but the track will decide what it wants to do with your car. I recommend getting Troy Thornes's book, "Build a Winning Pinewood Derby car". For some reason they are not available on Amazon. Michael's and Hobby Lobby usually has them during Pinewood Derby season.