R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Electric On-Road

Like Tree1Likes
Reply
 
Thread Tools Search this Thread
Old 02-13-2017, 02:02 PM   #1
Tech Initiate
 
Join Date: Aug 2013
Posts: 49
Default Xray strong on power understeer

Hi everyone, I'm Marco.
I have an xray T3 2012, and it's my first electric touring car, after many years of nitro models.
This little thing is making me crazy, because it understeers so much, on power.
I started with the basic suggested setup from xray, but it doesn't work. I made some little change, but I can't get rid of the problem, the front of the car seems to not hear any change. Rear is solid.
I run this setup:
default downstop (6 front, 5 rear; tried also 7 and 8 front), 4 caster, 4.8mm front height, 5mm rear height, 400 shock oil, shocks more vertical as possible, default roll center position rear and front, 3000 diff oil (tried also 10000, rear pretty solid but the car understeers :shock: ), wheelbase shorter as possible, front width 186mm, rear 188, spring not original but as close as possible, stock anti roll bar, and everything else is like the setup suggests. I run LRP G32 and the body is a protoform P37R.
Someone say me that this body have few downforce and is for carpet. I run in a very large and fast truck with medium-high grip. The understeer is very strong, I have to cut power to come out from fast turns.
I really don't know why, I have 10 years of experience in this world and I never seen a problem like this. The car is in good conditions, nothing wrong from what I can see.
So please, give me some input, should be really appreciated
maRRRco is offline   Reply With Quote
Old 02-13-2017, 02:14 PM   #2
Tech Master
 
Join Date: May 2010
Location: Chi-Town West Burbs
Posts: 1,332
Trader Rating: 3 (100%+)
Default

Try less droop in the front and a stiffer rear sway bar. #OneRacersOpinion
__________________
Goal Achieved....Not Dead Last.
mooby64 is offline   Reply With Quote
Old 02-13-2017, 02:22 PM   #3
Tech Elite
 
DesertRat's Avatar
R/C Tech Elite Subscriber
 
Join Date: Mar 2011
Location: Sniffin the 'Sauce Fumes
Posts: 2,472
Trader Rating: 1 (100%+)
Default

With the right combination of tires and racing surface, having too stiff of a rear setup and too soft in the front can take steering away. This seems to be more prevalent in really flexible chassis touring cars as well.

I'm going to guess that you're full saucing your front tires as well, and your prep is good, car is properly built and not tweaked, from your stated experience with nitro

Does the car track and steer well during 50% speed laps but only start to push badly at race speed? If so, to me this is a classic symptom of the car dragging the edge of the chassis in corners. Depending on your racing surface you may not even have a rub mark or goo to indicate it. Applying a small amount of white-out on the underside edge is a good way to tell, and wont stain or other ugliness.

My order of attack: find out if the car is dragging, if it is, harder front sway bar until it doesn't drag. Then you can tune with the weight of the car on the tires.
__________________
I race toy cars for fun. If I need to explain, you'll never understand.
Current rides: Diggity DC4 Chassis #10. Losi JRX-S Type R. CRC Xi, Xti, and Altered Ego Aluminum Chassis. Associated B4 based dirt oval late model, and B4 Buggy.
WTB: Carpet racing in Arizona.
DesertRat is online now   Reply With Quote
Old 02-13-2017, 06:56 PM   #4
Tech Champion
 
Join Date: Feb 2011
Posts: 5,854
Trader Rating: 1 (100%+)
Default

Xray cars are usually solid with their setup....
bertrandsv87 is offline   Reply With Quote
Old 02-13-2017, 11:31 PM   #5
Tech Addict
 
Join Date: Dec 2012
Location: Beverly Hills
Posts: 550
Trader Rating: 11 (100%+)
Default

You should change the rear track with to get it narrower than the front.
This will help with the steering.
Are you running a spool or one way in the front?
If you run a one way change to a Spool.
Which version of the T3'12 you are using? Rubber or foam?
Remove some of the upper deck screws to increase the flex.
__________________
LRP America, Ulti Tires
silden is offline   Reply With Quote
Old 02-14-2017, 04:21 AM   #6
Tech Initiate
 
Join Date: Aug 2013
Posts: 49
Default

I tried less front drop until 0 mm . It helped a bit but coming out from slow turns is a nightmare because there isn't weight transfer to rear axle. Anyway problem is still there.
Good idea to see if the car is dragging, I considered that, so I increased ride height to 6mm rear and 5,5 front, and I don't think the chassis can drag to the asphalt with this ride height, but I will try. This track is very fast, and the model rolls so much, to increase steering I had to make the front softer and rear stiffer, but maybe this is not the way.
I run the spool, and thanks for your reply, increase the flex should be a good idea.
Any suggestions about the body?
Because I used a lola Blits and the feeling of the car is totally changed, it's full of steering. Maybe a body with more front downforce can help me?
maRRRco is offline   Reply With Quote
Old 02-14-2017, 04:35 AM   #7
Tech Adept
 
Join Date: Jul 2012
Posts: 150
Trader Rating: 8 (100%+)
Default

The short rear wheelbase is making your problem worse, and I would recommend a LTCR body for asphalt.
anr211 is offline   Reply With Quote
Old 02-14-2017, 06:51 AM   #8
Tech Initiate
 
Join Date: Aug 2013
Posts: 49
Default

Quote:
Originally Posted by anr211 View Post
The short rear wheelbase is making your problem worse.
Why? The wheelbase is just that. No rear and front is only one. Shorter and the model turns more and has fast response. You can change it adding or removing shims front or rear but the effect is the same.
maRRRco is offline   Reply With Quote
Old 02-14-2017, 07:17 AM   #9
Tech Master
 
Join Date: May 2010
Location: Chi-Town West Burbs
Posts: 1,332
Trader Rating: 3 (100%+)
Default

Short rear wheel base moves the center balance point to the front. Taking weight away from the front end.
Try short front and long rear. This will move weight forward.
__________________
Goal Achieved....Not Dead Last.
mooby64 is offline   Reply With Quote
Old 02-14-2017, 07:49 AM   #10
Tech Fanatic
 
tbrymer's Avatar
 
Join Date: Feb 2011
Location: Arizona
Posts: 804
Trader Rating: 9 (100%+)
Default

I run on a high traction asphalt track with my T4 (2016) and I'm using 2.3 -2.6 front and 2.5 -2.8 rear springs, 37.5 weight oil, 5.8 rear 5.6 front ride height, downstop 4.6 front 4.4 rear, four button head screws removed from layshaft bulkhead area, sorex 32/36 tires depending on temp, 2 degree camber front and rear, .1 in and down front inserts, .5 center and down rear inserts, 1.5 degree toe out front, 2.5 - 3.0 toe in rear depending on track conditions. Car turns great. I have about 26-27 degree steering throw. 3000 rear diff fluid.
__________________
CRC - C&C Motorsports - SpeedZone

Last edited by tbrymer; 02-14-2017 at 02:35 PM.
tbrymer is offline   Reply With Quote
Old 02-14-2017, 02:17 PM   #11
Tech Initiate
 
Join Date: Aug 2013
Posts: 49
Default

Quote:
Originally Posted by mooby64 View Post
Short rear wheel base moves the center balance point to the front. Taking weight away from the front end.
Try short front and long rear. This will move weight forward.
I never considered that, but ... 2mm shorter isn't better than a little more weight to rear? This is a good question, anyway, thanks everyone, also for the complete setup, i will get good informations from that.
maRRRco is offline   Reply With Quote
Old 03-15-2017, 02:54 AM   #12
Tech Initiate
 
Join Date: Aug 2013
Posts: 49
Default

Hi guys this weekend I tried a new body, ltcr, with new setup settings. I used more straight steering rod so more ackermann effect according to xray manual. And more vertical shock. Now the car feels very responsive and direct with good corner entry and good steering in slow/medium speed corner but again understeers in fast corners. What I have to do? More lower roll center, soft spring? I don't know.
maRRRco is offline   Reply With Quote
Old 03-15-2017, 03:57 AM   #13
Tech Elite
 
Skiddins's Avatar
 
Join Date: Feb 2006
Location: Windsor, UK
Posts: 4,579
Default

Moving weight forward will increase initial steering, but once the car actually starts to rotate that additional weight at the front will want to make it push more.
__________________
Xray T4'16, T4'14 (Wet Car)
Xray X12 2016
Xray X1'16
wlrc.co.uk (West London Racing Centre)
RCDisco.co.uk
Skiddins is offline   Reply With Quote
Old 03-15-2017, 03:58 AM   #14
Tech Elite
 
Skiddins's Avatar
 
Join Date: Feb 2006
Location: Windsor, UK
Posts: 4,579
Default

Quote:
Originally Posted by maRRRco View Post
Hi guys this weekend I tried a new body, ltcr, with new setup settings. I used more straight steering rod so more ackermann effect according to xray manual. And more vertical shock. Now the car feels very responsive and direct with good corner entry and good steering in slow/medium speed corner but again understeers in fast corners. What I have to do? More lower roll center, soft spring? I don't know.
COuld try thicker rear diff, softer front roll bar, rear springs stiffer than front
__________________
Xray T4'16, T4'14 (Wet Car)
Xray X12 2016
Xray X1'16
wlrc.co.uk (West London Racing Centre)
RCDisco.co.uk
Skiddins is offline   Reply With Quote
Old 03-15-2017, 05:58 AM   #15
Tech Elite
 
Join Date: Sep 2010
Location: Beneath a rock down by the river. Don't have money for van
Posts: 2,693
Trader Rating: 1 (100%+)
Default

Hi Marco,
I think I know what's going on, can you please try the short wheelbase in the front and long on the rear?
30Tooth is online now   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
Exotek F1R Evoracer Electric On-Road 2384 03-20-2017 05:15 AM
Kyosho Lazer ZX-6 & ZX-6.6 4WD Thread 305M3 Electric Off-Road 2153 03-12-2017 08:51 PM
Ask Paul Lemieux, RC America/MOTIV/Gravity RC Paul L Electric On-Road 2761 01-06-2017 08:46 PM
Lab C-02 CapricornRC Nitro On-Road 569 02-20-2015 12:40 AM
Xray NT1 vs Team Magic G4S badKarma Nitro On-Road 35 10-13-2007 01:26 AM



Currently Active Users Viewing This Thread: 2 (1 members and 1 guests)
DesertRat
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 03:25 PM.


Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net