XRAY - Model racing cars

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 Post subject: Loose as heck T4 '19
PostPosted: Mon Dec 03, 2018 11:20:37 
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Joined: Thu Dec 07, 2006 17:53:45
Posts: 41
Location: Switzerland
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


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 Post subject: Re: Loose as heck T4 '19
PostPosted: Mon Dec 03, 2018 13:08:21 
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Joined: Sat Jun 18, 2005 12:48:40
Posts: 1347
Location: Windsor, UK
Is there a reason why you didn't start with a setup that was as close as possible to that on your T4'17?


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 Post subject: Re: Loose as heck T4 '19
PostPosted: Mon Dec 03, 2018 13:26:52 
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Joined: Thu Dec 07, 2006 17:53:45
Posts: 41
Location: Switzerland
Skiddins wrote:
Is there a reason why you didn't start with a setup that was as close as possible to that on your T4'17?


thanks for your question.

My '17 would run really fine on carpet with the setup I used on the '19, really... So I was basically using the same suspension geometry/setup on both, really :)

I really wanted to give a go to the ultra-flex alum chassis though, so I started with it, but swapped to the stock CWF in the middle of the day after trying a few other things which didn't get me anywhere.

Lastly - the ULP shocks are different anyway, roll momentums will be different. And usually xray's base setup sheets are pretty much 98% there already, so I tend to always start with the their recommendated kit setup, or at least not move away from them too much.

anything specific you have in mind?

Thanks!

Paul


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 Post subject: Re: Loose as heck T4 '19
PostPosted: Fri Dec 07, 2018 02:43:43 
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Joined: Tue Feb 10, 2015 13:37:36
Posts: 19
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.


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 Post subject: Re: Loose as heck T4 '19
PostPosted: Mon Dec 10, 2018 13:20:35 
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Joined: Thu Dec 07, 2006 17:53:45
Posts: 41
Location: Switzerland
thanks. this will be part of the checklist for the forthcoming teardown for sure...

Best,
Paul


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 Post subject: Re: Loose as heck T4 '19
PostPosted: Tue May 07, 2019 10:02:49 
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Joined: Thu Dec 07, 2006 17:53:45
Posts: 41
Location: Switzerland
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... :roll:

Cheers,
Paul


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