XRAY - Model racing cars

Hi.

First I would like to say thank you for all the help I get on this forum to understand the complexity of car setup. My FK is performing better and better with your help

During the race we had this weekend I was made aware of an adjustment that I have seen earlier but totally forgotten about...

On the setup sheet for the FK there are indications of clips used on the inside of the front hinge pin mounts. This will create an "inboard toe out".

I was told that this would help the car steer better through the corners due to “active camber change”.

So I tried with 2mm shims to see what happened. It felt like the car had much more front bite and steered more through the entire corner. It also felt like this provided more corner speed.

It is a bit strange that I have hardly ever seen this adjustment being mentioned before. The setup manuals I have seen haven’t mentioned this either.

Could someone please explain the theory behind this adjustment (Tony V )?

I did have a look at how the camber changed according to steering throw and suspension compression when I adjusted it on my setup system. But I would like to know what actually happens when you adjust the “inboard toe out”.

I found the spare belleville washers from my Losi XXXs (part# A-2909) diff were just wide enough to not "sink" into the plastic like other smaller washers and the curve gives a good mounting resistance. When they're tightened down each one equals .5 mm.

I just added in-board toe out and noticed these things changed:

1. The ackerman angle is increased a little more
2. You have to adjust your linkage rods out a little more to get the same toe-out rate, which in turn decreases the steering angle on the inner wheel and increases the angle on the outer wheel as the wheels are turned to full lock

If I'm thinking correctly, the effects are:

1. Increases corner entry steering from mid to full lock
2. Decreases corner exit steering
3. Creates a more smooth mid-corner steering transition as weight is shifted from the front to the rear

I'm going to test it Thursday and if I loose too much exit steering would it make sense to try a 6 degree caster c-hub to compensate? Maybe I need to go to bed now...thinking too much...

Ok, I’ll try to explain what I found with the car on the setup system.

I put on 2mm shims on the inside of the front hinge pin mounts. Then I adjusted the toe out to the usual 1°. Then I adjusted the camber settings back to 1,5 according to the new basic carpet setup from X-ray.

So, with steering at neutral I had all the normal angles. And when I compressed the suspension at neutral steering I had a little camber gain as normal.
But when I turned the steering and compressed the suspension I got some very interesting readings from the setup system!
If I turned the steering all the way to the left and compressed the suspension I read a large increase in camber (about 3° reading on the setup system) on the right wheel (outside wheel in a left turn).
On the left wheel I got a reading of about 1° positive camber. So both wheels were actually leaning into the turn.

I experienced much more grip through the whole turn with this adjustment, but since the effect is directly dependant on the amount of steering throw and suspension compression it felt a bit strange.
I have to do a lot more testing and practicing to determine how to make best advantage of this (to me) newfound tuning aid!

I also suspect that 2mm shims may be a little too much. At least before I have learned to control the effect it gives…
I heard that a rather well known X-ray factory driver “always” uses 1,5mm, and I think that would be maximum for a driver with normal skills.

It would be interesting to see what would happen if you would totally overboard with this and used say 5mm shimming.
I guess it is a matter of balance, as it is with every other adjustment we make on our fine racing machines

PERFECT!!!

I didn't have to change a thing on my setup with the new in-board toe-in. My assumptions from the camber readings were correct and my front end is so dialed now that I can place the car anywhere I want. During practice today I felt like everything was in slow motion in the corners as I was able to make any correction necessary to overtake people. I was consistently faster than most if not all, including several local fast guys, and had to lap a few of them in a mock race. The car is fast in the corners and with the new Tekin, acceleration was better than ever. I was pulling a few car lengths on everyone down the straight and was able to pass them on the inside and outside around the right sweeper at the end of the straight. During the race, since I was able to place the car anywhere needed, I avoided several bumps from others as well as pass the rest in the first 2 laps. After that I pulled away from everyone and lapped a few at the end with very consistent laps. The grippy carpet track is very technical with 5 lefts and 5 rights one right after another, all with different angles and multiple lines. This is a great setup! I did trim my throttle forward to a fast roll while in neutral and this allowed me to keep my corner speed up a lot. My full setup can be found at:

http://www.geocities.com/acquaba/Images ... _Setup.jpg

The bottom line is the in-board toe out gave very predictable steering and stability in the corners. I put my left/right EPA to full (125) and changed the EXP to -70%. This way I was able to hit the corners perfect with both smooth arcs and very tight u-turns. The question of the day was, "Do I want to pass him on the inside or outside...?"