XRAY - Model racing cars

Hello everyone,

My T4 chassis gets tweaked after every run which is normal but I am unable to untweak it properly after the run... When I put the chassis all by itself on a flat surface it seems flat and when I rebuild the car there is 0 to a negligible amount of tweak. After a run the tweak always appears on the front right and the rear right of the car (or the battery side), the left side of the car is absolutely flat and there is no chassis movement. I tried several methods that I found on the Internet, given by team drivers and other people. Nothing except rebuilding the car from scratch worked. That seems too much of a hassle especially during a race weekend. So can you give me any tips because I am running out of Ideas here? Maybe the battery side is lighter and this is causing the tweak? I have no idea...

Thanks in advance for your help!

Boris

I have had this issue before. I usually find the tweak in the shock towers. Undo the 4 screws that hold the tower onto the bulkheads, lightly push down on the carbon towers and tighten up the 4 screws.

Are you talking chassis tweak or spring tweak? If it's spring tweak, then yes you'll want to check the shock towers, if it's chassis tweak the shock towers are probably not the issue.

One thing I find is the motor mount and layshaft screws are very finicky. You want to take your time tightening these screws and make sure all of the screws you use are true and straight. Even if one is slightly off it can cause a tweak like you're describing.

After each run I always loosen off the topdeck, center brace and bulkhead screws and check for tweak on a peice of glass. If I find any at all then I flip the car over and loosen off most of the screws (generally not the servo mount ones) and lay the car back on the glass and make sure it's square. If it is, then I very, very carefully and lightly tighten the top screws, then flip the car and lightly tighten the bottom screws. Note - LIGHTLY - don't torque them down yet. After this I check the tweak one more time and if it's perfectly flat I go ahead and methodically tighten everything back up. Then, check one last time.

The nature of the design leads to tweak unfortunately. I've found my car to tweak after a run even if I didn't tap anything at all. Sometimes the torque from a modified motor can tweak the motor mount. I don't know that you'll ever be able to get a car to run tweak free for a few runs... to me it's just part of my pre-race program.

Keep at it, you'll find a system that works for you. Don't be afraid to experiment with the order you tighten screws or how you do it, you never know when you may stumble on something good. And when you do, come back and share it!

Luke

Hello,

Check the motormount, and motormount plate. I found out that after a big crash, motormount plate, and rarely motormount itself can be bent. And when you tighten the screws, chassis becomes tweaked. Check when you loosen the motormount plate and motormount screws, and see if the chassis is flat. If so, you need to change.

Regards

I feel like maybe I am overreacting a bit. Maybe I don't properly evaluate the tweak. For me tweak is where the chassis stays flat ...on a flat surface when a force is applied to 4 points of the car. I choose those points to be the extremities of the shock towers. When I press the 2 sides of the front shock tower the chassis stays absolutely flat on my board, no tweak. When I do the same thing however on the rear shock tower the chassis lifts when I press too much. Maybe I use too much force or maybe I have to choose different points. If I put the car on the Hudy blocks and press the chassis on them there seems to be no tweak, the chassis stays flat on the blocks... How do you guys actually check if there is tweak? Am I doing everything wrong or maybe you are using a similar methods as me?

I wasn't overreacting there was indeed a lot of tweak in the rear of my car. I started disassembling the car part by part and checking if the tweak would disappear. I got down only to the motor mount...It gives a nasty tweak, so I guess Mustafa was right. I basically removed it from the car and put it back on and made sure it is centered and mounted with all 4 screws. The tweak disappeared right away when I put everything back on. In conclusion, for me if the tweak persist even after untightening the top deck, the motor mount should be checked. Thank you for the help!