Strange steering on my M05

[Superba 4]

I have an M05 that I race on tarmac with a friend. What’s odd is if the car takes a knock the steering seems switch 5 or 6 adjustments to either the left or the right. Sometimes up to 15 or 16. It then seems to reset after a few laps nd settle down. Is this a servo thing? I have switched servos and still get the problem. Thoughts from anyone would be appreciated

[TurnipJF 9192]

Servo or servo saver would be my prime suspects. The steering rack is easy to inspect, so I doubt there would be anything wrong there otherwise you would probably have spotted it already. 

[Superba 4]

But could it be 2 servos in a row? Also it’s weird that it slowly resets itself. 

[TurnipJF 9192]

Good point. Unlikely to be exactly the same fault with two different servos. Probably the servo saver then. Is it working smoothly, centering the arm accurately relative to the base after each knock, or is it sticking? A sticky servo saver would certainly explain the behaviour you describe. 

[WillyChang 1814]

If still using stock plastic part, sometimes the moldings isn't 100% true. The big C spring clamps onto 2 halves that make up a bit... if these 2 bit halves aren't exactly equal you'll suffer steering that changes neutral point every bump.

i change to hi-torque servosaver or 3rd party

[Juls1 1661]

The factory plastic servo savers tend to get grit in them and as a result don’t return to centre perfectly anymore. It’s pretty common issue with tamiyas especially on off road cars, but sometimes touring cars on dusty surfaces or racing on carpet have the same issue. I suspect this is your problem, either upgrade to a high torque servo saver, aftermarket or if you have a metal gear servo just eliminate it altogether with a alloy horn (or just glue the factory plastic unit together). M05 is so small and light which such tiny wheels (so no real leverage) it’s unlikely you’ll damage a metal gear servo, just make sure your EPA’s are set properly so you don’t damage the servo overdriving it. 

[WillyChang 1814]

If we "have to" use the original servosaver...

grab calipers to measure width of the 2 half nubs

gently file down to make them exactly equal width

assemble servosaver & install

tie a thin ziptie around the whole C spring. Sometimes even a drop of superglue at the 2 nubs and the tips of C spring.

Any impact will usually break the glue & ziptie before servo gears.

"usually"  

 

If we must run plastic geared Tamiya/Futaba stock servo always bring stock of spare gears to the race pits. 

 

[TurnipJF 9192]

I think that the stock servo saver has an unnecessarily bad reputation. Carefully assembled and kept clean, it works very well and there are many parts that are more likely to break in a collision. I have been running various M chassis for years now and while I have broken wheels, hubs, uprights and even the front of the chassis itself, the servo savers live on. And they don't show any significant slop either.

[WillyChang 1814]

Yeah I haven't broken too many servosaver in Minis... often they break the knuckle arm before stripping the servo.