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Old 01-31-2010, 09:09 PM   #1
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Default XXX-S Tips and Talk for Stock Classes

Welcome fellow XXX-S drivers !! As you can guess, this thread is designed for all of you who have been following John Stranahans expert discussion and advice BUT have been longing for more information pertaining to the level of driving most of us mere mortals drive at.....Stock Class. This thread, like John's "mod motor" thread, will allow all of us stock class folks to share setups, chassis tips, advice, troubleshooting and anything else regarding the object of our affection.....the Losi XXX-S. Still one of the best chassis around. Whether you race in Touring Car class, VTA, RCGT or a customized class using sealed "Can" motors or anything between 17.5t and 25.5t, this is YOUR thread.
As the flow of information continues in many threads, the pertinent information becomes a little difficult to keep track of so....I'll be creating a website to index and archive the information for quick and easy reference.
So all you current and future XXX-S drivers join in and make this YOUR thread.
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Old 01-31-2010, 09:17 PM   #2
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Lets start out with a sound off of all you XXX-S drivers out there !! Tell us what class you race and what type of track you typically race on.

I'll start us out. My friends call me "Dino". I own 4 XXX-S cars. President of the Brevard Electric Auto Racers rc club. We race VTA and RCGT on a fairly smooth un-prepared concrete parking lot using a combination of PVC and Road Rails barriers.
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Old 01-31-2010, 10:35 PM   #3
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I run a XXX-SG+ in a Southern CA parking lot series - prepped asphalt, road rails type barriers, and lots o'traction. Since I am new to TC racing, I run in the 17.5 rookie class.

I love the car, easy to drive, cheap parts, easy to work on (or I just don't know any different). My only challenge to date is trying to get rid of some moderate front end push. I have the rest of the car running the way I want, just can't solve the push. I have been following the other XXX-S threads for ideas....
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Old 01-31-2010, 11:23 PM   #4
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to solve a push with a ball diff front end.

Make the front softer (move upper shock end in) or make the rear stiffer (move upper shock out). I like to keep the lower shock ends out for better suspension efficiency. In the front, when you reach the limit going in, then go to the next weaker spring. Just keep adjusting until you get results.

Also go to softer front sway bar, stiffer rear sway bar.
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Old 02-01-2010, 06:09 AM   #5
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And just a reminder....one change at a time. Unless you can isolate where the change worked or didn't work.....you'll just end up frustrated. Always good to keep a notebook or blank setup sheets on hand so you can see what you started with and what you changed along with the results.
And yes, the X is pretty simple to work on. The newer cars may be a bit better in some respects but don't believe everything you hear. After many different cars, the X is still my favorite and still one of the easiest cars to work with. I think you'll hear that alot on this thread and others.
I'm currently making some of the front suspension changes that John suggested in the mod thread. I'm also installing the Losi 10mm shocks from the JRXS. They fill from the top and have knurled caps and collars. Hopefully offer better action and be easier to maintain. I'll make reports as I make changes and get track time.
Thats a great suggestion for all of us....make sure to let us know the effects of your changes.
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Old 02-01-2010, 06:16 AM   #6
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Quote:
Originally Posted by Micro-E View Post
I run a XXX-SG+ in a Southern CA parking lot series - prepped asphalt, road rails type barriers, and lots o'traction. Since I am new to TC racing, I run in the 17.5 rookie class.

I love the car, easy to drive, cheap parts, easy to work on (or I just don't know any different). My only challenge to date is trying to get rid of some moderate front end push. I have the rest of the car running the way I want, just can't solve the push. I have been following the other XXX-S threads for ideas....
Erik, can you give us a summary of the current setup?
Anybody else dealt with a push situation ? If you have specifics on your changes....post em'.
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Old 02-01-2010, 10:57 AM   #7
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K. Here ya go…..

Front –
Caster: 4*
Toe: Out 1*
Ride height: 5mm
Droop: 3 (on the Losi droop gauge)
Pivot Support: 0F
Arms: Middle
Camber Ball: Black
Camber: -1*
Camber Mount: 2
Shock Mount: 2
Springs: Blue
Oil: 40wt Associated
Shock Length: 60.5mm
Piston: 56 (red)
Roll Center: High
Front Drive: Spool

Rear –
Toe: In 2*
Ride height: 5.5mm
Droop: 4 (on the Losi droop gauge)
Pivot Support: 0R
Arms: Middle
Camber Ball: Chrome
Camber: -1*
Hub Camber Mount: A
Tower Camber Mount: 5
Tower Shock Mount: 3
Arm Shock Mount: Outside
Hub on Arm Mount: Offset
Springs: Blue
Oil: 40wt Associated
Shock Length: 65mm
Piston: 56 (red)
Roll Center: Low

Drive Belt: Black belt
Body: Mazda 6
Tires: SJR Premount Sorex 36R (Simple Green to get them clean before each heat)

This is based of the Jon Kerr 7/5/2003 setup I found. The only changes I made to the setup:

1.) Dropped the front springs to Green from Purple. Purple seemed way too stiff out of the gate. Just last week I dropped the Greens to Blue and the car seemed to push even less – so I kept the Blues on.
2.) Reduced the oil from 50wt to 40wt.
3.) Removed front sway bar (.040). With this bar the car was very pushy so I removed it and the car felt better to me.

John’s post reminded me that I forgot to mention that I have a spool. I went with a spool setup because everybody who is fast at the track runs one. The car pushed a bit with a diff, so naturally it got a bit worse with the spool. Funny thing I noticed was the car felt MUCH faster with the spool on a good lap, but tracking my lap times (I graph them also) shows that there is no real difference in lap times between the spool and diff except the spool seems to be less consitent for me. Hmmmmm.... Maybe because of my lack of driving ability!!! The car with this setup is very stable and easy to drive. Speed on the straight (~160’) is not a problem and one of the intermediate 17.5 drivers commented that my car with right with them, if not gaining a bit.

I was starting to wonder about tires. Everyone runs the 36R, but the track temp can run around 60-70 depgrees here. Could my slow driving not heat the tires up enough to generate enough front traction? I bought a set of 32 or 28s to test, do you think tires rated for track temp could change the game for me?
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Old 02-01-2010, 11:10 AM   #8
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I just read the traction roll thread, and the last post just made me think about something I neglected. I never balanced the car side to side. I now run Lipos (3200 TP 40C) and they are MUCH lighter than the NiMhs they replaced. I seems logical that running much less weight in an already stiff car can affect the ride quality. I have not weighed it but I bet the BL motor is heavier than my 19T and tiny Keyance speedo kit as well - really throwing off the balance of the car.

Thoughts? Am I overthinking it?
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Old 02-01-2010, 11:16 AM   #9
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With a locked front diff, things are not so clear. Adjustment depends where in the corner the push is and how you drive the corner. I always slowed for a corner with the XXX-S and entered with considerable power which I maintained through the corner until exit. In other words I cornered on power so the car would not slow and stall. If you corner this way a locked diff may not respond to normal tuning. I suggest you tune the car with a ball front diff, then install the slipper spool. Now if normal tuning does not get rid of the push, try reverse tuning. Usually a couple of shock movements up high tunes it up. (stiffer front to cure the push, this is reverse tuning).

The reason for this is the locked diff has considerable torque steer. As the outside wheel loads up in a corner it can provide more forward traction than the inside wheel. This adds to the steering toward the inside. Now the more loaded the outside wheel (stiffer front) the more of this torque steer there is. If you corner off power you wont notice this and will probably be somewhat slower.

A spool normally has slightly less turn in than a ball diff which has slightly less turn in than the one-way.

I am surprised by those hard tires in stock at 60-70 F. Is it carpet or asphalt. A hard tire will cause a push.

you muist balance the car side to side. Use X-acto points front and back in the middle and lift the car. The heavy side will lag. You may have to remove the front bumper. Or use two scales and two beams.
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Old 02-01-2010, 11:56 AM   #10
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John, thanks for the info!

I'll put the diff back in the front (KIIS principle) and tune from there as well as balance the car.

The track is asphalt parking lot. I reviewed my notes and I read the air temp instead of the track temp. The last track temp I recorded was 92*- that was with an air temp of 75* and sunny in November.
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Old 02-01-2010, 01:08 PM   #11
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Off to a good start guys. Thanks John. I'm sure I'll be looking for some help after this coming weekend. First time with the car in a couple of months. Micro-E...let us know what happens.
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Old 02-01-2010, 06:45 PM   #12
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Whats up guys, I've been following Johns thread on the XXX-S and its been a big help. I run VTA on a tight carpet track ( 95 X 45 ) at "The Gate" in Brunswick,Ohio.

I started out in VTA with the XXX-S about 18mos ago, then, switched to a Corally RDX. To make a long story short, I hated the car. No matter what i did, the car always felt twitchy and on the ragged edge of disaster! I have recently switched back to a XXX-S G+ with great results.

For my base set-up, I went to the Losi site and used Greg Hodapps 9/14/02 rubber tire set-up sheet. The only changes I made were following Johns advice: Used a 4R pivot support up front and installed the JRXS spool. Also trimmed every other tooth off a blue belt on a 108 tooth 64P spur. I run the Losi threaded shocks with titanium nitrided shafts. No sway bars.

I'm running the 21.5 / lipo combo. the battery is in the rear position and the esc (HAVOC) is also wedged in the rear ( behind the motor, just in front of the rear tires ). I treat the tires with Jack The Gripper on the inside half of the fronts and a full coat on the rears ( started to traction roll at the end of the race day, might go less on the Jack in the future).

This set-up has felt very stable and easy to drive. I was shocked at the night and day difference between this car and the RDX. I'm not the best driver by a long shot ( about 1.5 to 2 sec behind the fast guys ), but I'm a full 1 to 1.5 sec faster than my best times with the RDX. The added durability in the 8 to 10 car VTA demo derby is also a huge plus! Joe
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Old 02-01-2010, 08:07 PM   #13
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Hey Joe, know what you mean...the X just seems to grow on ya. I've heard Johns' take on the spool but mod is definitely different and I believe his is not a standard spool. So what should I expect with a spool in VTA or RCGT?? Strangely, I've never run with one. I always stuck with diff or 1 way..mostly because the tracks were smaller and more technical...supposedly not the kind of track a spool would be good for. John made a comment recently on his driving style entering into turns and accelerating out and it sounded like what I do so I'm gonna give the spool a try this weekend.
Did you find the 4R pivot trick to be of value ?
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Old 02-02-2010, 04:20 AM   #14
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To be honest with you, I'm not sure if the difference in the way the car feels can be attributed to the 4R switch. The last xxx-s I had was set-up by a guy at the track. The current one is set-up based on Hodapps sheet. That in and of itself may be the big contributor here, but the end result is the same...This car feels great! The spool is used by a number of racers here. I think because the 21.5's have so much torque, they absolutely RIP out of the corners. My car is equally as fast as any other car out there. The only hanicap seems to be the driver.
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Old 02-02-2010, 08:00 PM   #15
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Hey Joe, thanks for the mention on another thread.
Is anybody running high roll centers ?? We race on concrete and I'm using a setup from the Losi Board. Seems to work well but I honestly don't know why !! Technically it seems to violate the general rule of thumb for roll center adjustment.

Last edited by Evoracer; 02-06-2010 at 08:12 PM.
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