Suggested amount of steer for thin/narrow wheels

[Watchitgo]

Hi everyone.

I am in the process of building a car for my daughter to participate in the outlaw race in my son's upcoming derby. Last year we had thin wheels. The car won but wobbled all over the place and I am hoping to prevent that from happening this year. I know that the every car is unique and the current guidance is 4 to 5 inches over 4 feet for the "fat wheels" is the same true for the thin ones.

Based on what I have learned here, we have bade some changes to this years design

1. reduced the wheel gap to .015
2. added notches to the body so that the wheels are not so far away from the body.
3. canted the rear wheels 3* and using a 9* bent axle to steer the car
4. the wheel base is 4.75 inches
5. we are shooting for a COM around .75 inches in front of the rear axle
6. the tack is a BestTrack that is in OK condition but far from a pro track

Video of my daughters car from last year.

 

[Vitamin K]

I've never built an "Eliminator" or an "Unlimited" car, but I believe you want:

- No camber on the rear wheels. |---|

- Less steer on the DFW than you would use for a fat wheel car. I don't know numbers, but maybe start at 2" over 4'?

- If your wheels still have a hub, then, yes, you're going to want to inset them into the body so that the distance between the inside face of the wheels is the same as it would be for a fat wheeled car.

 

[TRE]

most pro thin wheels are 1 to 3 inches

 

[bracketracer]

Watchitgo, the wheels on the car in the video appear to be cut down stock BSA wheels? If so, were they cut down on a lathe or "improvised equipment"?

Are you running them with stock BSA axles also?

If the answer is yes, improvised, and yes, then I would leave the steer up closer to 4.5 or 5" in 4'. Narrowing the nose at least as VK indicated would really help. I'd probably leave the rears canted to help stabilize the rear end. If you're running larger aftermarket axles then I'd be more inclined to drill the rears flat.

 

[Watchitgo]

You are correct the wheels are cut down BSA wheels. We used a drill press with a chisel and 1-2-3 blocks to cut them. The sibling race does not have the same restrictions as the scout race so we are using 92TX axles. We did narrow the nose on the DFW side.

Thank you every one!! I really appreciate the feed back.

 

[TRE]

i would put 5 to 6 inches in that car

 

[bracketracer]

If you only narrowed the DFW side so that it centers the rear wheels over the guide rail, I would then suggest to narrow the NDFW side until the inside face of the raised wheel is no more than .050-.060" from the rail if the rules allow it. When you watch the video of last year's car you can see that the car is rotating about it's COM and skidding to the left and right with every bump in the track. If you tighten the track width clearance up front, it won't be able to turn sideways like that and will probably be even faster overall?