XRAY - Model racing cars

Hi all

Back my new car's first race this weekend. I was running my freshly built '19 - first new xray since my '17 which had served me well and was a peach to drive.

My first day with the '19 was an absolute disaster, possibly my worst race of the past 20 years. The car was desperately loose, mostly in the sweeper entry and in the chicane, but unconfortable everywhere, really.

Layout was tight and technical, except the sweeper (which was not smooth but more of a abrupt entry one, and then smooth). Lo-grip carpet. We run Rex30's and boosted 13.5's. My car was setup as per the stock setup sheet, except the aluminium extra-flex chassis, and 2.5-2.8F. Montech Racer snug with the front bumper. The rest, all stock. Electronics from the previous race, where they did better than fine. I could not get the car to behave, I never found a way to be confortable with the car and "pilot" it, and could only drive very conservatively. Heck, did spin out a couple of times in the sweeper...

Things I've done during the race to no avail, in that order
- tried another set of tires
- go to 2.7F/2.5R
- go from 450R to 350R
- removed the front brace
- toyed around with screws on motor mount
- swapped the alloy chassis to cwf one (yes... I did that during raceday and missed a couple of mains)
- go 5K diff
- heck, even changed motors and speedo setup

Checks I did during the race
- check that I hadn't swapped L/R C-hubs (for caster...)
- changed diffs (in case there was a warped something in there with a missing tooth or whatever)
- detweak after every run (not that it needed it... still do it all the time)
- checked for a binding transmission, it's 100.0% smooth and free
- no fleeing CVD pins
you get the idea.

The car was very very very edgy, I basically had to "endure" it all day and feather the throttle rather than drive it. I'm usually a mid-to-bottom A-mainer with 50/60 or so entries, and this time there were only 29 drivers due to a calendar conflict... and I was bottom of the B, and duking it out with people who usually are two mains below me. I understand I'm getting older and all and the younger guns are getting faster, but the car really really wasn't helping and I was doing one mistake every couple of laps or so, losing the rear all the time. When this is the case, usually it's the tires, but I did pull out 2 sets of Rex30's that day. Statistically, it can't be that.

At this point in time I'm wondering whether I've missed something during the assembly, or whether the nature of the car is to be edgy as heck... I can't believe it's the latter. Xrays are meant to be the RC equivalent of a gucci loafer, ie a confortable car that about works right out of the box with no efforts. Saturday, mine was anything but that...

I'll tear it down fully and rebuild it from the ground up. If you have any good suggestions...

Thanks,
Paul

Is there a reason why you didn't start with a setup that was as close as possible to that on your T4'17?

The biggest difference, handling wise from 17 car to 18/19 is the shocks. Make sure you have the shock shaft length no more than 9mm, otherwise piston may hit the bladder when you are driving the car, which might be the reason car handles funny. If still not solved, try the 17 shocks and shock towers on your new car. Sometimes old shocks work better on specific conditions. If the problem still persists, now you can search for actually a mechanical issue.

thanks. this will be part of the checklist for the forthcoming teardown for sure...

Best,
Paul

Just realized I had never updated this.

The culprit were the tyres... out of the 3 race sets I had that season, two were defective. With the third one, the car was just as good as anything else on the track...

Cheers,
Paul