Positive or Negative Camber for DFW

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4wheeldrift
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Positive or Negative Camber for DFW

Post by 4wheeldrift »

In past years we always ran a negative camber for the DFW, but I've seen in several posts on various boards that actually it should be a positive camber. I've read that the thinking is that there's less contact surface against the center rail as well as the wheel will migrate out to the axle head anyhow when it hits the rail. It all seems counter intuitive since we did a positive camber for mid-America and the wheel actually rode on the wheel beads (seems like more rolling resistance...no?).

I'd like to get folks' feedback who have tested both ways and for sure saw that positive camber was faster.

thx
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Stan Pope
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Re: Positive or Negative Camber for DFW

Post by Stan Pope »

The goal is to ride the DFW low on the rail so as to produce the shortest "sliding distance." This I accomplished with positive camber (axle head down.) Don't cut the tread down so far that the beads touch the track. Either leave the finished tread diameter slightly larger than the bed diameter, or cut into the beads just enough to clear the track.
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4wheeldrift
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Re: Positive or Negative Camber for DFW

Post by 4wheeldrift »

Thanks for responding Stan.

Unfortunately it's still not clear...what do you mean by 'sliding distance'? Do you mean that the lower part of the wheel makes contact sooner with the rail versus negative camber and contacting with the upper part of the wheel?

I was trying to visually figure out how the footprint would be any different on the rail and was thinking this was what other posters were talking about.

thx
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Re: Positive or Negative Camber for DFW

Post by Speedster »

That's correct, 4wheeldrift. Another advantage is if the sections of the track are not lined up perfectly. If the section you are going into is sticking out the Positive camber will probably ride over it. If you have Negative camber your DFW will dig into it causing the wheel to be damaged and the car possibly be thrown off the track. With 1 1/2 degrees Positive camber the beads should not touch the track.
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Stan Pope
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Re: Positive or Negative Camber for DFW

Post by Stan Pope »

4wheeldrift wrote:what do you mean by 'sliding distance'?
Sliding distance: distance of relative motion between rail and wheel as the nose of the car moves from start to finish. Distance is important because energy loss = work done = force X distance!
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Re: Positive or Negative Camber for DFW

Post by Slalom »

Hi,

recently on a test track, thought I had ourcar pretty wll tuned. Our car was significantly louder than faster cars on the track regardless of toe-in adjustments. What could this be? Run Cambered rears, and DFW, 3 wheels, smooth axles, krytox blend with teflon spray.

Has anybody fiddled with placing some type of lubricant on the inner wheel margin of the DFW ( the only wheel that touches rail)?

Thanks!!
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Re: Positive or Negative Camber for DFW

Post by Stan Pope »

Slalom wrote:recently on a test track, thought I had ourcar pretty wll tuned. Our car was significantly louder than faster cars on the track regardless of toe-in adjustments. What could this be? Run Cambered rears, and DFW, 3 wheels, smooth axles, krytox blend with teflon spray.

Noise derives from vibration. Here are some of your car's possible sources of vibration, listed in decreasing likelihood in my estimation:
1. Wheels with run-out (variation in the distance from the bore to the track contact point), including bore offset from center of wheel, irregular inner edge of tread, irregular (deformed) bore (particularly the outer edge of the bore).
2. DFW friction against rail. Negative cambered DFW probably noisier than Positive cambered DFW.
3. Bore-axle friction and hub-axle head friction
4. Camber angle at critical point where wheel changes from fully engaging the bottom of the bore against the axle and cross binding of top of inside edge of bore against axle and bottom out outside edge of bore against axle.
Slalom wrote:Has anybody fiddled with placing some type of lubricant on the inner wheel margin of the DFW ( the only wheel that touches rail)?
This is "standard procedure" and does yield improvement in times (while the lubricant lasts). We who are limited to graphite routinely dip a finger tip into a graphite puddle and run it around the inner edge of the dfw. So long as it is just a "film" the inspector doesn't bat an eyelash. You can probably do the same with krytox and/or spray, but keep it subtle.
Stan
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Re: Positive or Negative Camber for DFW

Post by Slalom »

Excellent thanks!
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Re: Positive or Negative Camber for DFW

Post by 4wheeldrift »

Slalom wrote: Our car was significantly louder than faster cars on the track regardless of toe-in adjustments.
There is the possibility that you experienced what we did where the angle of the camber was enough that the wheel actually rode on the outer beads of the wheel. That'll make a fair amount of racket.
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Re: Positive or Negative Camber for DFW

Post by Stan Pope »

4wheeldrift wrote:
Slalom wrote: Our car was significantly louder than faster cars on the track regardless of toe-in adjustments.
There is the possibility that you experienced what we did where the angle of the camber was enough that the wheel actually rode on the outer beads of the wheel. That'll make a fair amount of racket.
Good catch!
Stan
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