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Old 08-21-2002, 08:46 PM   #256
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John:

question on shock positions - am i right in assuming that for the front, laying the shocks inward will give me more on-power steering while standing them up will make for more intitial turn-in? and does standing up the rear shocks generally gives you more rear traction or side bite?

camber links: on the xxx-s, a longer link does what? add or reduce traction?

oh, and have you tried using a locked front diff on the xxxs? the tc3 seem to be doing that and have been getting good results from it.
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Old 08-22-2002, 10:14 AM   #257
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When you move the top of the shocks inward on a touring car the spring tension at the wheel (wheel rate) is made softer. When you make one end of the car softer you tend to increase cornering traction of that end.
A stiff spring on the inner hole and a medium spring on the outer hole that have the same wheel rate can feel slightly different in the car due to slight differences in suspension friction (stiction). The difference in friction is small for medium tension springs, I just ignore it. It is a bigger efffect on stiff springs like the 20 lb/inch Losi Spring. For this spring it might be better to use the green 17.5 lb spring a little farther out on the shock tower than the 20 lb spring all the way in. The car felt better to me anyway.
A stiffer front spring gives you a quicker responding car (more initial turn in) at the expense of some cornering traction. Turns quicker but then pushes. A softer front spring will give more cornering traction and thus more on power steering. A softer car (front and back) gives you more on-power steering as well by delaying weight transfer to the back a bit.
I am running mod at the moment at ReflexRC indoor asphalt and am using the standard front diff set very tight, but not locked. The Losi is handling so well that I hate to mess with it. I can drive it really hard without screwing up too much. I tried a front oneway and lost so much time on the highspeed tight turn from lack of adequate braking, that my gains in the infield were nullified. In stock I use the one-way front diff. Setup is a personal thing, but mine is posted at the ReflexRC.com website. I am using drag brake on the high speed turn in mod, nowhere else on the track.

On the Losi I shortened the upper camber link(separtely on the front and the back of the car) by moving the inner mounting position out. This produced more cornering traction on each end of the car. Too much in fact in both cases on asphalt indoors and outdoors. I moved the links back to the second hole out. When you change the link lenght on this car you make a slight change to the roll center and you increase the ammount of negative camber gain of the tire as the chassis rolls. I would imagine that the change in the negative camber gain was more important here as the roll center is only slightly afffected on this car.

Last edited by John Stranahan; 08-22-2002 at 10:39 AM.
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Old 08-22-2002, 10:58 AM   #258
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John,
I could not find your setup on reflexrc.com. Would you mind posting it or providing a link. I race my XXX-S in mod.

Thank you,
Dave
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Old 08-22-2002, 12:45 PM   #259
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Dave- Its in the message forum of that site. Here is a copy.

Losi XXXS Setup for Mod at Reflex
Front Suspension: Toe 0 degree, ride height 4 mm, camber -.5 degree, kickup 0, caster 4 degree spindle carriers, no swaybar, front shock, 56 piston, 45 weight oil, .010 inch bevel made by hand with a small drill bit on the top of each hole in the piston, Green Spring, top shock mount all the way out, droop height about 4 on supplied gauge, Low roll center blocks shimmed up .040 to give a mid-level roll center, Pivot support 0F in lower holes, (shim blocks to make pins level) standard diff very tight, inner camber link pivot second hole out from inside.TC3 hex adaptors. Use Body Lexan for pivot block shims.

Rear Suspension. Toe 2 degree per side (stock), ride height 4 mm, camber -.5 degree, 4R rear pivot in upper holes and .040 spacer under rear low roll center blocks to achieve midlevel rear roll center(shim blocks to make pins level), no swaybar, rear shock 55 piston, 45 weight oil, .010 inch bevel made by hand with a small drill bit on the top of piston, Silver Spring, top shock mount all the way out, Droop height 6 on supplied gauge, standard diff, inner camber link pivot second hole out from inside outer camber link pivot in outer most hole with one .030 washer under the ballstud, the cup is trimmed on top with an X-acto knife. TC3 hex adaptors.

Motor Reedy Sonic 2 11/2 (90/20)x1.83 (a little too much motor for this tight track), Sorex 36R's with Elmer’s Sticky Out. (Or use Takeoff 32's dry. The 32's are going to be a little bit soft over 90 F, but they are the handout tire.

The purpose of the bevel on the shock pistons was to prevent the car pogo sticking on the bump at the end of the straight. The bevels actually worked.

The front one way was a little faster in the infield but much harder to take the high speed turn at the end of the straight in mod due to lack of good braking. I use a tiny bit of drag brake here.

The only change I have made recently is to remove the washer under the ballstud of the rear hub carrier. The rear roll center is actually at or near the ground even though it's described as midlevel.

Last edited by John Stranahan; 08-22-2002 at 01:07 PM.
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Old 08-22-2002, 12:58 PM   #260
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I recently bough a Orion Chrome 14/2 for use at Reflex. Had to gear it 88/23x1.83 before it got going. This is a higher gear (one more tooth on the pinion) than I use with a P2K2 stock motor. Motor temperature and brush wear was OK with that gearing (167F, 8 runs with no major brush discoloration, one light cut at 4 runs).

Roll Center-So how do you find the right roll center. If your springs front and back are getting on the stiff side before the car has good precision in a high speed turn, then you can stand to raise the roll center a bit. This allows you to use a little softer springs. The softer springs will allow the tires to follow the bumps in the road better. If the car is taking a little too long to roll or unroll and impeding your driving in mod then you can raise the roll centers a bit also.

Overall Spring Rate- Start with soft springs. If your layout has a demanding highspeed turn into a chicane or a hairpin then this turn might determine what spring rate to run. If the steering is imprecise on the high speed turn and you keep slamming into the corner disk then you might need stiffer springs overall. In a high speed turn you don't have the luxury of making 100 tiny steering adjustments to get to the marker. You basically get one shot at it. The car has to be precise. Performance in the infield is usually better with lighter springs.
Mod requires a little stiffer springing just so the car finishes rolling or unrolling quicker so you can get on with the buisness of the next turn. Use the lightest springs that will get the job done. Fine tune with upper shock mount position.

Shock oil-too stiff and the car will slide around. Start here and reduce the shock oil viscosity untill the car gets sloppy. Then go back stiffer about 5-10 weight. Stay on the light side so that tires don't hop and so that the tires follow the road bumps well.

Last edited by John Stranahan; 08-23-2002 at 07:42 AM.
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Old 08-22-2002, 09:56 PM   #261
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hey john, thanks for the input. i'll be testing some of it this weekend. keep it coming bro.
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Old 08-23-2002, 07:54 AM   #262
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Gearing For Mod- A few of us were having some trouble making runtime in a 5 minute race. Here are some tips to increase runtime. Wipe off the tires well and reduce your warmup lap to ony a couple of turns. I am usin 732 hz drive frequency on the cyclone speed control. This increases the efficiency of the motor at part throttle and improves part throttle punch. Reduce the timing of the motor a little. Keep the throttle just ahead of the cars speed. What this does is takes maximum advantage of the recirculating current that is going through the Schottky diode at part throttle. This is free current that does not come from your battery. As soon as you go to full throttle there is no recirculating current in the motor to take advantage of. Move the throttle smoothly stay at part throttle as much as possible.

It seems there is one perfect gearing in mod where the car will have maximum traction to accelerate. The tires hook up better at this gearing. Runtime will also be a little low at this gearing because the car is hooking up better. Gear a little higher (smaller spur) to soften the car a little and get a little more run time or gear down just a little to make the car accelerate even faster. This will also give you a little more runtime. I had a few mod races under my belt now so I took the second approach and geared down just a bit. I was rewarded with faster laptimes.
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Old 08-24-2002, 11:14 PM   #263
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Best Line For Stock Class. If you watch a formula 1 or a Cart Race and get an arial view, the best line is usually clearly marked with a blackened area of the track. It seems that every inch of pavement is used to make a corner. The cars start wide hit the apex and exit wide. In stock touring RC car's class there is just not enough motor to do that. If you travel a few extra inches your lap times will probably be worse. At the region 9 on-road regionals in Houston, I watched the line of the better drivers. You could almost take a straight edge and connect each corner radius with a straight line to find the fastest path. There were two exceptions. There was one corner (about 150 degrees, (where 180 degrees is a hairpin turn) very sharp) onto a chicane. If you took this corner about 10-12 inches wide of the straight path then you could use full throttle through the chicane and just steer through it. Coming off this chicane onto the straight there was a 90 degree corner. Your car was about 2/3 full speed here so it was a little faster to turn out about half to 2/3 the track width onto the straight. All the other corners were a connect the dots situation.

Cornering procedure-So how do you make the stock touring car take this path. Well you divide the track into straight sections and curved sections. Coming into the corner you have to slow to the right speed. You just reduce throttle (rarely off throttle) Then you drive it around the marker at constant speed. The faster guys are about an inch from the markers. Our layout had some markers made out of a curved material with a gentle radius. These were driven the same way. You stay on the radius till you intersect the next straight line section. You can see a distinct change in the motion of the car on the corners. Constant speed is the key. The car is being kept right at the limit of traction for that radius of corner at constant speed.

So How do you make your car do this. A couple of suggestions. you can't have all of your steering travel turned off with the radio to control oversteer. Fix the setup and make the car able to take a tight radius turn. Then if you need a gentle radius you can just turn the wheel less. Don't get greedy with speed entering the turn. You have to enter at just the speed that you can maintain for the entire turn.

Last edited by John Stranahan; 08-25-2002 at 04:00 PM.
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Old 08-28-2002, 01:15 AM   #264
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John would be better as to set the car so it can throw into a turn without losing traction on the back and without the back end swinging outa control

or
in setup a way that the back end 'follows' the front end ...
without breaking traction ...
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Old 08-28-2002, 09:50 AM   #265
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imataquito

I have set up my car both ways. One in which you have to throw the car into the turn and the other where the back just follows the front. I like the latter the best, I think it's faster. I noticed that David Joor who won the stock Region 9 regionals at ReflexRC did not have a hint of loosenes in the back end. The back end just followed the car very precisely.

In the setup that I had to throw the car into the turns, I had shortened the rear camber link one hole. The car had too much rear grip with this setup. I had to throw the car into the turn to have enough steering traction.

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Old 08-28-2002, 08:08 PM   #266
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i agree with john. i have a "flowing" xxss and i have a tc3 that basically wants to be thrown into the corner and although the tc3 feels faster, im sure the flowing xxxs which basically floats thru the corners does go faster. going fast into a corner then yanking the steering at the very last minute to make a turn looks faster but it isn't actually so compared to a car that takes the the best/fastest line with very small and gradual movements in your steering wheel.

---- dont get me wrong about the tc3 and xxxs, those are jst how ive setup those cars. with the right set-up i can probably make the tc3 more "flowing" and the xxx-s want to be thrown into a corner.
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Old 08-28-2002, 09:41 PM   #267
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i love the flowing style setup but ..it seems like its easier for other cars to overtake me if i am flowing aorund the track ... altho my lap times are faster
and harder for me to overtake other cars

with the throwing setup i can throw my car inside or outside of another car LOL and they cant seem to 'eat me' from the inside


i am confused ....
for now i am using the flowing setup for huge tracks and throwing setup for tight tracks

is this about right ??
i do notice however that the pickup out of a turn seems slower with the throwing style ... but i tend to block the car behind me so its harder to overtake .....
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Old 08-28-2002, 11:14 PM   #268
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Imataquito
With the throwing style you dont need to slow down as much at the entry by making the rear end slide but this will tend scrub speed at the exit (depends on how much you slide). This setup is better for tracks with lots of 180s followed by very short straight sections where your gearing makes your car accelerate ver quickly to top speed. You gain time into the corners and dont lose as much out of them.
In a faster flowing track with rounder corners its better to use the 'flowing' setup so thet car carries its speed into the straights
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Old 08-29-2002, 12:24 AM   #269
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Yep, it all depends on you and the track you're driving on.

Get someone to time you, run the car one way, then try it the other way, see which is faster and then look at which is more consistent.

I like a tolerant, "playable" car - one that I can change the line so I can play with the guy in front of me if I have the chance to pass him. I want the rear to follow the front without having to be pitched around corners.

But I also like to drive my sedan close to the way I drive my Pro10. . .agressive into and out of the corners.

Unfortunately I have to give and take, so I look at which is faster on a given track layout (ours changes week to week). . .
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Old 08-29-2002, 12:26 AM   #270
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I just realized that the tone of my post sounded kinda stuffy and condescending. . .sorry - I really didn't mean it that way. . .just relating how I have to balance what I want with what seems to work. . .

oh well, it's late and I'm going to bed. . .
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