Suspension/chassis tuning question
03-04-2013, 12:27 PM
#1
Suspension/chassis tuning question
I'm very familiar w/ chassis tuning and the theoretical reasoning behing changes but a certain recent instance has me stumped. I have a TC5 that we are currently running on a rubberized type gym flooring. It is very dusty until the line is cleaned out by running the cars some. What I experienced was a very severe oversteer on power. Generally I would soften up the rear a tad and i'd be ok. However at this location the only thing that improved the situation, and it improved it signifigantly, was to not only stiffen the rear quite a bit but also stiffen the front as well. When I tried to soften the rear without touching the front it made little to no difference yet stiffening the rear helped. I also lowered the rear inner camber link (raised rear RC) which should hurt on power rear traction I'd think. This all has me baffled. Maybe you guys can shed some light on why stiffening the rear would help an on power oversteer issus. I run a front spool but tried a front diff and it made no difference. I have the rear diff about medium tightness.
35wt losi F/R and 1.5/1.25 sway, Camber was -1/-2.5
Excessive oversteer: Blue (17.0)/Silver (14.5)
No oversteer: Gold (19.5)/Red (22.0)
35wt losi F/R and 1.5/1.25 sway, Camber was -1/-2.5
Excessive oversteer: Blue (17.0)/Silver (14.5)
No oversteer: Gold (19.5)/Red (22.0)
Last edited by TT_Vert; 03-04-2013 at 12:55 PM.
03-04-2013, 12:50 PM
#2
Sometimes you over-roll and it affects the contact patch of the tyres. You'll also find that a car that is rolling will become more inconsistent at the limit because it is changing it's position quite a lot as it loses and regains grip. On high-grip surfaces you don't notice this phenomenon so much which is why cars can get away with softer settings.
I used to run a lot on slippy gym floors here in the UK with spiked tyres and very soft setups wouldn't work, the cars slide was more progressive and controllable with a harder setup. I've also seen it very clearly with the modern 4wd buggies which often handle better with a rear anti-roll bar on the very low grip tracks.
Basically there is a window of roll stiffness and geometry where the tyres are going to work, if you are either too soft or too stiff you are going to have problems.
I used to run a lot on slippy gym floors here in the UK with spiked tyres and very soft setups wouldn't work, the cars slide was more progressive and controllable with a harder setup. I've also seen it very clearly with the modern 4wd buggies which often handle better with a rear anti-roll bar on the very low grip tracks.
Basically there is a window of roll stiffness and geometry where the tyres are going to work, if you are either too soft or too stiff you are going to have problems.
03-04-2013, 03:23 PM
#3
It's very odd as I don't appear to have any slide now. it isn't that it is a controllable slide, I don't seem to have slipping which is good IMO.
Dave
Dave
Sometimes you over-roll and it affects the contact patch of the tyres. You'll also find that a car that is rolling will become more inconsistent at the limit because it is changing it's position quite a lot as it loses and regains grip. On high-grip surfaces you don't notice this phenomenon so much which is why cars can get away with softer settings.
I used to run a lot on slippy gym floors here in the UK with spiked tyres and very soft setups wouldn't work, the cars slide was more progressive and controllable with a harder setup. I've also seen it very clearly with the modern 4wd buggies which often handle better with a rear anti-roll bar on the very low grip tracks.
Basically there is a window of roll stiffness and geometry where the tyres are going to work, if you are either too soft or too stiff you are going to have problems.
I used to run a lot on slippy gym floors here in the UK with spiked tyres and very soft setups wouldn't work, the cars slide was more progressive and controllable with a harder setup. I've also seen it very clearly with the modern 4wd buggies which often handle better with a rear anti-roll bar on the very low grip tracks.
Basically there is a window of roll stiffness and geometry where the tyres are going to work, if you are either too soft or too stiff you are going to have problems.
03-04-2013, 03:31 PM
#4
Here is a video I shot last season - these are the quickest cars at the meeting, 13.5 boosted. They feel and look "planted" - but there is a lot of slide going on as you can see from the slow motion.
| + YouTube Video | |
03-05-2013, 02:53 PM
#11
I had been having issues lately after going to a new track with excessive loose neutral power, after fiddling with every setting (diffs, RC etc) it came down to just the wrong tyre compound for the surface.
Went from a Rubber 32deg to a 36deg tyre and its handling well as ever. It was odd as the softer tyre was a lot more slippery, maybe it was just over heating.
I too am going to buy the RC CrewChief, awesome bit of gear there!
Went from a Rubber 32deg to a 36deg tyre and its handling well as ever. It was odd as the softer tyre was a lot more slippery, maybe it was just over heating.
I too am going to buy the RC CrewChief, awesome bit of gear there!
03-07-2013, 06:32 AM
#12
Received a pm from one of the other guys that race at the track with some more info.
What caught my eye was the huge difference in spring rate ranges between different driver's setups as much as 3 times different (front springs 12# to 35#). That's crazy. Add to that the grip goes away after 2 minutes tells me the main problem as Monsta mentioned above is tires. Maybe you already have the best tire for your surface but I would suggest:
1. Check tire temps after a run to see if they are over/under heated. The Sweep OG tire is for asphalt so you may not be getting enough temp into the tire as the racing surface temp is low (65F).
2. Contact Sweep to see what they would recommend for your conditions. Give them as much info as possible.
Once you are convinced you have the best tire then you can try to optimize the setup.
What caught my eye was the huge difference in spring rate ranges between different driver's setups as much as 3 times different (front springs 12# to 35#). That's crazy. Add to that the grip goes away after 2 minutes tells me the main problem as Monsta mentioned above is tires. Maybe you already have the best tire for your surface but I would suggest:
1. Check tire temps after a run to see if they are over/under heated. The Sweep OG tire is for asphalt so you may not be getting enough temp into the tire as the racing surface temp is low (65F).
2. Contact Sweep to see what they would recommend for your conditions. Give them as much info as possible.
Once you are convinced you have the best tire then you can try to optimize the setup.
03-07-2013, 06:56 AM
#13
Thanks for all the effort Bob. I think that more of the problem is debris on the tire when you get out of the tiny groove that does eventually develop. There will be dust/glitter, etc. on the tire when you get anywhere out of the groove. It seems impossible to clean the tire during the run after that. When I get out of the groove I have massive pushing not the other way around. The track surface was about 62 degrees, i'll check tire temp but if anything my tractions starts off well until I get some dust on the tires.
Dave
Dave
03-07-2013, 02:14 PM
#15
Bob, enjoyed the video and still trying to understand using RC crew chief for setup ideas. Can you elaborate a little more about reading your tires for buildup and relating it to your camber settings. You can use private messaging (or even better your crew chief thread) if you would rather not muck up this thread.
Greg
Greg