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Old 08-01-2011, 06:19 PM   #1
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Default On-power under and off-power over

Hi, I haven't been running TC for a couple of years and just returned last winter. I've been in this hobby for quite some time but never really got into car setup much.

Yesterday I brought my RS4 Pro2 to the soda prepped temporary outdoor track we have here. It was about 20-22*C weather, and I ran the car with a set of Sorex 32R's to start.

The car was showing major on-power understeer when around sweepers and pulling out of corners. When l let off the throttle and turn, it starts to spin out.

That was without traction compound. On another run I sauced all four tires, the on-power under went away but the car was sliding around in general (I did wipe off the excess before the run).

Later I tried a set of Sweep 28's and it improved a lot, although still a tad oversteer when off-power, I was able to do consistent lap times with it. It started to oversteer near the end of the run but I suspect it was due to overheating?

So my question is, am I simply using the wrong tires or is there something wrong with the cars setup to begin with? And how do you determine if a set of tires is not right for the track when it is doing this (on-under and off-over)? Can it be remedied without swapping tires?

Im sure I have a lot more questions but I'll let it start from here.

And heres my setting if it helps:

Front:
50wt Tamiya blue (Hard White>Blue>Yellow>Red Soft)
-1 camber
-1 toe
2*+10* (12*) caster
droop 2
ride 6.5
no rollbar

Rear:
50wt Tamiya white
-1 camber
-2 toe
stock kick-up (non-adjustable)
droop 2
ride 6.5
no rollbar

Other: 13.5 boosted

When people mention droop, is it transferrable between different chassis'? Because from what I know varies from where on the arm you measure it and different cars have different arm thicknesses. Or are they talking about the actual difference between the settled and max ride height?

Thanks!
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Old 08-01-2011, 08:07 PM   #2
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Quote:
Originally Posted by rc_square24 View Post
Hi, I haven't been running TC for a couple of years and just returned last winter. I've been in this hobby for quite some time but never really got into car setup much.

Yesterday I brought my RS4 Pro2 to the soda prepped temporary outdoor track we have here. It was about 20-22*C weather, and I ran the car with a set of Sorex 32R's to start.

The car was showing major on-power understeer when around sweepers and pulling out of corners. When l let off the throttle and turn, it starts to spin out.

That was without traction compound. On another run I sauced all four tires, the on-power under went away but the car was sliding around in general (I did wipe off the excess before the run).

Later I tried a set of Sweep 28's and it improved a lot, although still a tad oversteer when off-power, I was able to do consistent lap times with it. It started to oversteer near the end of the run but I suspect it was due to overheating?

So my question is, am I simply using the wrong tires or is there something wrong with the cars setup to begin with? And how do you determine if a set of tires is not right for the track when it is doing this (on-under and off-over)? Can it be remedied without swapping tires?

Im sure I have a lot more questions but I'll let it start from here.

And heres my setting if it helps:

Front:
50wt Tamiya blue (Hard White>Blue>Yellow>Red Soft)
-1 camber
-1 toe
2*+10* (12*) caster
droop 2
ride 6.5
no rollbar

Rear:
50wt Tamiya white
-1 camber
-2 toe
stock kick-up (non-adjustable)
droop 2
ride 6.5
no rollbar

Other: 13.5 boosted

When people mention droop, is it transferrable between different chassis'? Because from what I know varies from where on the arm you measure it and different cars have different arm thicknesses. Or are they talking about the actual difference between the settled and max ride height?

Thanks!
the only thing i would do different is
swap the springs around you would want the softer ones in the rear for more traction & i would go with 2* camber in the rear also & maybe 2.5 toe in the rear & maybe 40wt in the rear
that just my base set up
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Old 08-01-2011, 09:17 PM   #3
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try stiffer rear springs and thinner shock oil maybe 40wt front and 35 back.
you will need a set of sticky tires for sure. your tires do not give you enough tractions
maybe loosen your rear diff abit and tighten front diff abit if possible
also try not to let throttle off too much to keep weight at the back?

Last edited by littlealex; 08-01-2011 at 09:33 PM.
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Old 08-01-2011, 09:44 PM   #4
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try stiffer rear springs and thinner shock oil maybe 40wt front and 35 back.
you will need a set of sticky tires for sure. your tires do not give you enough tractions
maybe loosen your rear diff abit and tighten front diff abit if possible
also try not to let throttle off too much to keep weight at the back?
Thx for letting me try the tires Alex it made a big difference
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Old 08-01-2011, 09:53 PM   #5
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Sounds like something is binding, have you checked that?
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Old 08-01-2011, 10:08 PM   #6
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Thx for letting me try the tires Alex it made a big difference
welcome. i think mostly is tires that make the car drive funny.
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Old 08-01-2011, 10:25 PM   #7
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Sounds like something is binding, have you checked that?
I fully rebuilt the car before running it for the first time in a while. All arms and hubs were sanded/drilled for smooth action.
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Old 08-02-2011, 12:05 AM   #8
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shock oils are heavy
go back to kit setup could also help just to start from scratch
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Old 08-02-2011, 08:50 AM   #9
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try with heavier battery first. it maybe your stick pack is too light. this car is design for older (heavier) battery.
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Old 08-02-2011, 09:07 AM   #10
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I never had that chassis, but no one sees a problem with 12dg of caster? almost every car runs 4 these days.
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Old 08-02-2011, 11:43 AM   #11
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I never had that chassis, but no one sees a problem with 12dg of caster? almost every car runs 4 these days.
Well, he can go to the 0* mounts but the Pro 2 did seem to like 2* of kick up. See if you can get a set of 6* or 8* blocks though, might help.

Also see if you can find a Roll Center kit for that car if you don't have one. Going to be hard to find. Here's one on eBay...I'd snatch it up if I were you. Makes a ton of difference on this car. All the guys at HPI had them on their cars when they raced the Pro 2.

http://cgi.ebay.com/HPI-RACING-73008...item4aad45042d
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Old 08-02-2011, 11:54 AM   #12
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I'm not sure if they made a 6* c-hub but i'll try the 8*

As for the handling kit i've seen people use 2mm spacers in place so i'll try that too.

Thanks for the help guys.
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Old 08-02-2011, 12:38 PM   #13
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Are you using a spool, ball diff, or one-way?
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Old 08-02-2011, 12:40 PM   #14
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front and rear diff
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Old 08-02-2011, 12:48 PM   #15
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Originally Posted by rc_square24 View Post
I'm not sure if they made a 6* c-hub but i'll try the 8*

As for the handling kit i've seen people use 2mm spacers in place so i'll try that too.

Thanks for the help guys.
I'm almost certain they made a 4 and 6 degree set just can't remember if it was for the Pro 2, 3 or 4...It's been a while...further research shows they made them for the Pro 3 and 4 and the Sprint 2...could have sworn we did a 6 degree in aluminum though...

Also, the roll center plates in the kit are 1.5mm IIRC...not 2mm. Lastly, ride height with the plate was about 4.5-5.5mm and most of the time we ran 5.0 front and 5.0-5.5 rear.
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