Birelart AM-29 tuning - 206 Heavy and Reds

Chassis Setup, Tires & Handling Forum
42

I’d agree with TJ - going negative on camber and taking caster out are complimentary changes, not opposing. For a kart that is too active on entry, either change could help. And on an old school single bend waist kart like an AM29, both of those things plus narrowed front are probably in the cards.

I’d double down on the negative camber if it’s a rounder profile tire too. Would work better on a Vega than an MG I’d guess and way better than on a Mojo.

3 Likes
43

Drop the front and rear ride heights?

44

Yes.

Slammed low from and rear. Only run higher if it’s wet or super cold.

It’s twitchy cause you’re transferring too fast from being high.

1 Like
45

Burpo is the Birel guy but I do agree that lowering ride heights will help also. Lowering the front really will numb the front end.

2 Likes
46

Update on this: I had three 15 lap sessions this morning:

  • I started the day off with everything the same but with the slower steering rate. This made a big difference, I felt like I had a lot more control. I used that as the baseline run.
  • Next, I dropped the rear ride height first (left the front ride height in the middle) and it completely removed the twitchiness. It was only about a tenth faster over the baseline, there was probably more in it but I needed to adjust my driving. I felt that the effect of the lower ride height in the rear was that the balance moved from the crazy oversteer on entry to very slight understeer on entry. So I added a 5ml space to each side on the front to try to get some better turn in.
  • The wider front end created oversteer on turn in, and was about .2 slower, so I went back in on the front.

Next weekend is a club race, I plan to start the day with this setup (lower rear end but the same 1.5 spacers in the front) and newer tires, focusing on changing the rear track width to see if I can get the balance back where I want it, since it seems like I am stuck on the front - 2 spacers is too wide and 1.5 is slightly too narrow. Current rear track width is 131.5cm.

Does that thinking make sense?

1 Like
47

10 and 5 spacers, caster in. Both ride heights low.

1 Like
48

Try the hardest front bar too (black). Matt setup my kart all the way low in the front and rear. Longest wheelbase setting too. Running just a touch negative camber, spacer and a half width in the front. I never touch the kart from there. Only changes all year have been gear ratio. It’s working too 7.5 point lead going into our last club race

1 Like
49

Confirming you’re running seat struts too? What hole do you have them in?

50

Thanks, I will try that. What’s your rear track width?

51

Most of our guys are running 51-51.5"

1 Like
52

Running struts and they are in the rearmost mounting holes on top of the bearing carrier.

53

Sorry for the poor quality upload. Looking at the data the data and this video (I am #014), it seems like I am lifting and setting twice in the long corners, and sliding in the fast chicanes, is that a symptom of going too wide in the rear?

54

Just following up on this, I have been struggling mightily to get to grips with this chassis. I went from being a regular podium threat at our local club on my old and worn out CompKart 4R to fighting with the new-comers at the very back of the field on this thing. I couldn’t carry any speed into corners without upsetting the rear end. After trying in vain to make the front end less aggressive on turn in, we determined the problem might be the rear being too flat, so we added a heap of caster, moved the seat rearward about an inch and a half from the Birel-recommended settings, removed the seat struts and front bar, this all helped with the feeling and pace. The kart now feels much more stable and seems to be a lot quicker. The test will be the final race this weekend.

55

How has your latest round of changes worked? I have an AM-29 and am fighting oversteer on very hard tires.

57

I changed a lot, including moving the seat back and adding a lot of caster. The seat seemed to be the biggest improvement. The kart became drivable after moving it back about 1.5" from where it was originally mounted.

1 Like