XRAY - Model racing cars

I struggled with my car all day at RugRacers at the weekend. I basically had too much rotation under power, so had to be really soft on the throttle. I also never felt comfortable on the straight and wasn't able to put the car where I wanted with confidence - especially on the in field dog leg (I guess because that was steering under power).

I tried to dial this out during the day and did make some progress. The best change was going to 5 and 5 droop (I started at 5 and 4). However the problem still persisted.

Putting the car on the setup gauges when I got home, I noticed that the read toe in was 2 on the near side and 3 on the off side. I guess this definitely won't help - but could this be the problem?

As to curing it, the two sides of the car are identical and the hinge pins aren't bent - so I guess I'm into looking for something that's tweaked somewhere. Has anybody else suffered this and any advice where to look? I'm tempted to renew all of the rear suspension components, but that's a lot of cost for a not guaranteed fix!

I also feel that the gear diff is tighter than I remember it - it's a specr with 1000cst oil. It was definitely quite a bit tighter than my friends, but his was an xray diff with 500cst oil.

Don

I found that the rear hinge pin mount for the rear wishbones doesn't line up perfectly.
It only seems to have to out by a fraction and the rear toe is screwed.

I just used the appropriate shims to bring the rear toe to what I wanted each side.

Out of interest, how was the handling on your friends car with the 500Cst oil in the gear diff?

Skiddins

Thanks Skiddins, will try that. What effect will uneven rear toe have?

The lighter oil gave his car more rotation on corner entry.

Don

The car was equally bad (unpredictable) last night, even after a complete rebuild and correcting the rear toe.

One thing I had pointed out to me was that the chassis is very worn on the motor side as a result of the outdoor season. So much so that it is wafer thin under the motor and starting to delaminate. The theory is that the car is tweaking very easily.

So I'm going to replace the chassis and see whether that improves things.

As for carpet racing, when I found an unstable weird acting car it turned out that it was a too low body specially on the sides when running some more droop. Standing still the body height was at 5mm and I never thought that this could be too low for smooth carpet tracks.

The chicane at my local track is very unforgiving on the chassis underside under the motor too - you only have to look at the motor! I am not saying it isn't that but the wear there has never caused me a handling issue.

Yeah I know. But I'm at a loss as to what else it could be. Just been through a significant rebuild exercise replacing all bearings, rebuilding all drive shafts, checking hinge pins are flat, replaced c-hubs, knuckles and rear uprights, rebuilt gear diff. I'm not sure there's much else it could be.

One difference is that I've gone onto sweep tyres (from sorex) for the indoor season. Perhaps they just don't suite my driving style

I'm about to upgrade to a T3'12 and give my son the t3, but need to resolve these handling difficulties first

One way is to run the car on asphalt and see if it is OK - I assume it was running on asphalt before. If it is OK then that suggests it is the carpet setup, then again I suspect you are using a carpet setup that has worked before. But if nothing is broken/tweaked then the problem suggests the setup is giving you too much front grip and/or too little rear grip. Perhaps you could post you setup for others to have a look at.

.... although it does not necessarily explain your earlier comment about feeling uncomfortable on the straight

The setup is not far off the standard kit one. 2.8/2.6 springs, 5/4 droop, 450/350 shock oil, 5.0/5.5 ride height, 2/1.5 camber. I'm running a spec-r gear diff with 1000cst oil, and have removed the top deck posts and the 2 rear most screws from front of top deck.

The uncomfortableness on the straights is that I have problems putting the car where I want it, so frequently have to back out early before the sweeper at the end of the straight as my line is wrong.