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Old 21-11-2017
Derka Derka is offline
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Question Setup help for mixed surface (carpet + wood)

Hi guys,

I'm hoping for some advice on setups for my 2wd PR S1 V3 FM.

I race indoors on a mixed surface of carpet and wood In a community hall.

The car feels good in the carpet sections but pushes wide off power and on power (unless using bucket loads of throttle to slide the rear out) in the wood sections.

My initial train of thought was to move weight forward, battery forward, rear shocks mounted on front of wishbones, stiffen rear, soften front but this did not help and my times showed on average I was perhaps slower.

This week I followed a setup from PetitRC exactly (apart from running geared diff Vs ball diff) which should of made the car much better but it was the same.

A chap at the club was helpful and we made some more changes which kind of helped but it was still under steering a lot, even low speed. We decided to try putting the weight more rearward to help try and rotate the car using the pendulum effect but with no great success. We also played around with springs. Softening it to try and provoke some roll.

Tyre wise on the rear I've tried Cactus, Mini pins and mini spikes. On the front I've tried low profile staggers and 2wd mini pins.

Any ideas as it's driving me nuts!

Last edited by Derka; 21-11-2017 at 07:13 AM.
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Old 21-11-2017
richm richm is offline
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here is the setup i was running at DMS last saturday. mostly Primafelt carpet, but with some lino and wood sections.
i had turned the punch down to minimum on the speedo which helped with my itchy throttle finger on the slippery section as well.


edit - i may have misrememberd the rear shock length. 22 seems very short. 26-27 would be more like it.
Attached Images
File Type: jpg DMS_S1v3_FMMM.jpg (292.5 KB, 22 views)

Last edited by richm; 21-11-2017 at 09:02 AM.
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Old 21-11-2017
Derka Derka is offline
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Thanks, forgot to post but I am running this setup but with a geared diff with 5k oil and normal arms.

I tried with the lipo weight, rear shock positions, battery position etc but just lack steering on the wood sections where others (B6, KF) all carry much more speed and tighter lines

http://site.petitrc.com/setup/prraci...ord2017042930/
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Old 21-11-2017
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cjm_2008 cjm_2008 is offline
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Things to check (this is generic advice since I'm unfamiliar with your car):

1. front tyres. What compound are you using? What profile? How wide are your front rims? Are the sidewalls stretched & more rounded? Running 2wd tyres on 4wd rims will stretch the carcass & limit the contact patch. Tyres are always the first thing to check.

2. front camber. Sometimes less is more - as in, try running 0 - 1 degree for a flatter contact profile. Also investigate the effect of the turnbuckle inboard mounting points, as this changes the rate of camber change (a longer link will result in little change, shorter = more camber under load)

3. where are you encountering the understeer? Corner entry? Mid corner on power? Corner exit? Are you braking at all? braking in the right place forces weight to transfer to the front, which will increase bite.

4. front toe - are you running toe in, neutral, or toe out? Toe out will increase steering on corner entry but may make your car 'darty'.

5. wishbone binding? - remove or disconnect the front shocks & make sure the suspension moves freely, both sides.

6. Diff: Ball or gear? And if gear, how heavy is the oil? A very stiff diff will cause understeer on entry, since a tight rear axle limits the rate of rotation, especially using mini pins on carpet.

Understeer isn't necessarily bad. Remember, your arse isn't in the car. Oversteer can be slower.
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Old 21-11-2017
tonydevon tonydevon is offline
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Quote:
Originally Posted by richm View Post
here is the setup i was running at DMS last saturday. mostly Primafelt carpet, but with some lino and wood sections.
i had turned the punch down to minimum on the speedo which helped with my itchy throttle finger on the slippery section as well.


edit - i may have misrememberd the rear shock length. 22 seems very short. 26-27 would be more like it.

is your 73/28 gearing correct?
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Old 21-11-2017
Derka Derka is offline
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Thanks for the feedback so far guys.

Here is the setup I ran last night.

After the first heat, we changed to a AE Yellow (Softer) front spring, AE Blue Green rear, moved the lipo full rearward, moved the shocks back to the rear of the rear arm, removed a 48g under lipo weight and also changed the rear tyres to a Mini Spike in yellow.

Even after the changes, it was still pushing on the wood sections on throttle, off throttle but the rear would slide with some provoking, which it wasn't before which I think was the changed from Cactus to Mini Spike. If I brake while mid corner, it will rotate nicely and the setup I initially started with trying to get as much weight forward as possible to give more front grip, thats my understanding of how it might work, but we decided to try something else by softening the springs and moving the weight back and like I say, the only thing that made a slight improvement was Mini Spike rears, which I think is is basically removing rear grip, laterally, and forward.

CJM;

1. front tyres. What compound are you using? What profile? How wide are your front rims? Are the sidewalls stretched & more rounded? Running 2wd tyres on 4wd rims will stretch the carcass & limit the contact patch. Tyres are always the first thing to check.
Yellow, Slim, front Mini pin, 2wd wheel. Rears, Yellow Mini pin, Cactus and Mini Spike.


2. front camber. Sometimes less is more - as in, try running 0 - 1 degree for a flatter contact profile. Also investigate the effect of the turnbuckle inboard mounting points, as this changes the rate of camber change (a longer link will result in little change, shorter = more camber under load)
Will try reducing front camber to -1.

3. where are you encountering the understeer? Corner entry? Mid corner on power? Corner exit? Are you braking at all? braking in the right place forces weight to transfer to the front, which will increase bite.
Carpet sections the car appears fine. Understeer happens on corner entry, mid and exit. Coasting and on power, unless I provoke it with a load of throttle to bring the rear round. Braking will rotate the car but the corners are tight so I basically come to a stop when touching the brakes.

4. front toe - are you running toe in, neutral, or toe out? Toe out will increase steering on corner entry but may make your car 'darty'.
Zero toe. I might try some Toe out.

5. wishbone binding? - remove or disconnect the front shocks & make sure the suspension moves freely, both sides.
This is a new kit, but I have changed springs 2-3 times and everything is free.

6. Diff: Ball or gear? And if gear, how heavy is the oil? A very stiff diff will cause understeer on entry, since a tight rear axle limits the rate of rotation, especially using mini pins on carpet.
Geared Diff, 5000 cst oil.

Last edited by Derka; 08-11-2018 at 11:19 AM.
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Old 21-11-2017
tonydevon tonydevon is offline
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me personally I would run lighter oil in front, -1 camber, and some toe out

will try up load my setup sheet for you, last run at cardiff cobra so mix of carpet and exposed plastic floor.

lipo fully forward in FM I run 72gr weight under lipo, minipin 2 rear and yellow cut stagger front
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Old 21-11-2017
chris24jt chris24jt is offline
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i would have thought reduce the oil in rear diff will help - what do others run - do most people run ball diff?

also have you tried shorter wheelbase?

or just a bit of brake on sharper corners to bring the back end round?
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Old 21-11-2017
tonydevon tonydevon is offline
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try shifting the steering linkage out to the outer holes on hubs, so longest arms, that ackerman setting gives me more innital bite and works a treat.

rear hubs right back, front hubs back

cant upload a sheet as its too big a file sorry
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  #10  
Old 21-11-2017
richm richm is offline
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Quote:
Originally Posted by tonydevon View Post
is your 73/28 gearing correct?
aye. i dont run turbo on low grip.
i wanted to gear up, but i dimly remember that i couldnt get a bigger pinion to fit with the 83t spur, so got a smaller pinion. with hindsight, i should have gotten the 75 or 77, as now i can just about get the motor close enough to mesh on the FM. on the MM, as i discovered on sunday, the motor hits the RF wishbone hanger if you are running 1º anti squat. i ended up with 81/30 for that.

smaller spur also gets the motor closer to the rear axles, which cant hurt.
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Old 22-11-2017
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cjm_2008 cjm_2008 is offline
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Also investigate drag brake. It could help. I have 20% set on my speedo.

I run yellow cut staggers on the front of my cougar KC, on 'standard' 2wd rims.
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