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Tweak and TC setup question

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Tweak and TC setup question

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Old 02-15-2019, 08:28 AM
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Default Tweak and TC setup question

Below is my TC setup routine. Itís pretty standard but Iím confused about one pointÖwhat happens if the chassis is tweaked.


1. Setup the ride height by adjusting the spring preload collar on the shock. Make sure front and rear preload are adjusted evenly.

2. Setup the droop

3. Put the car on the setup station. Check for camber and toe.

4. Put back the tires and lay the car on a flat surface. Check for tweak by lifting up the car with a hex tip in the chassis centerline and check that both left and right wheels are lifting up at the same time. If not, adjust the spring preload for the opposite sideÖi.e. if tweaked in the rear, adjust the preload in the front.



For #4, normally this isnít an issue. However, this time I have some moderate tweak in the front. I took out the tweak by adjusting the spring collar preload in the rear (about half a turn for left and half a turn opposite direction for the right).


So, my question is do I have to put the car back on the setup station 2nd time because the camber may have changed slightly by me adjusting the spring preload collar?

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Old 02-15-2019, 08:45 AM
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You missed out my first step which is chassis flat on a flat surface to see if it i tweaked.
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Old 02-15-2019, 11:31 AM
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As antlockyer said, first of all you have to untight top deck screw to release eventual tension and check if it is flat. Then, push the chassis on the tweak board and tight (gently) top deck screws in a cross sequence (front left, rear right, front right, rear left). Now and then you have to untight and tight again bulkheads and motor plate screws.
If the chassis is flat, the preload is ok but the wheel lifting is not the same, check the droop. Do not forget to check shock towers, especially in the rear, becasue body mounts are connected to shock tower and in case of flip you can upload some tension on the show tower. So, untight and re-tight shock towers screws to release tension, then chek it again.
Now you can put the car on the setup station (just one time, at the end of the procedure).
This is how I chek the car. By the way, in this video you can find Martin Hudy tips:

Bye

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Old 02-15-2019, 11:56 AM
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If you don't already have one, get a good flat board to test for chassis tweak.
I picked one up from Exotek Racing for like $15, -it works great.
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Old 02-15-2019, 12:23 PM
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The chassis is slightly tweaked. So the question is do I have to put it back on the setup board 2nd time after I compensate for the tweak by adjusting the spring preload collar.
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Old 02-15-2019, 01:07 PM
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Originally Posted by jakelamotta View Post
As antlockyer said, first of all you have to untight top deck screw to release eventual tension and check if it is flat. Then, push the chassis on the tweak board and tight (gently) top deck screws in a cross sequence (front left, rear right, front right, rear left). Now and then you have to untight and tight again bulkheads and motor plate screws.
If the chassis is flat, the preload is ok but the wheel lifting is not the same, check the droop. Do not forget to check shock towers, especially in the rear, becasue body mounts are connected to shock tower and in case of flip you can upload some tension on the show tower. So, untight and re-tight shock towers screws to release tension, then chek it again.
Now you can put the car on the setup station (just one time, at the end of the procedure).
This is how I chek the car. By the way, in this video you can find Martin Hudy tips: https://www.youtube.com/watch?v=m_ScOTQHqrw

Bye

Jake
Excellent video. Watched it 3x already haha
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Old 02-15-2019, 01:38 PM
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So to ask the same question slightly differently…. If you know the car is tweaked. What do you do:

1. Do you first adjust the preload spring collar to compensate for the tweak so that both wheels lift up at the same time, then put the car on the Setup Board or

2. Do you adjust spring collar for ride height and making sure that the preload are the same for left and right (same amount of turns). Then put it on the setup board. Then check for tweak and adjust preload as necessary…and done.
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Old 02-15-2019, 01:52 PM
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If you know the chassis is tweaked, first step (before doing any spring pre-load or anything suspension related) straighten out the tweaked part by loosening and re-tightening screws. If that doesn't fix it, replace any bent parts.
If the chassis is straight but you still get 'tweak' check if your springs are matched, as well as your weight distribution.
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Old 02-15-2019, 03:51 PM
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Originally Posted by LzREngineering View Post
If you know the chassis is tweaked, first step (before doing any spring pre-load or anything suspension related) straighten out the tweaked part by loosening and re-tightening screws. If that doesn't fix it, replace any bent parts.
If the chassis is straight but you still get 'tweak' check if your springs are matched, as well as your weight distribution.
I've checked all the things that you've listed. I think the cause is that the aluminum chassis has a slight bend and left and right weight distribution may not be optimal because I'm running a heavy lipo 7500mah.

I'm not so worry about the tweak as I can compensate it by adjusting the spring preload. I really just want to know what is the proper setup procedure for a slightly tweaked car.
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Old 02-15-2019, 04:07 PM
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Originally Posted by johnzhou2476 View Post
I've checked all the things that you've listed. I think the cause is that the aluminum chassis has a slight bend and left and right weight distribution may not be optimal because I'm running a heavy lipo 7500mah.

I'm not so worry about the tweak as I can compensate it by adjusting the spring preload. I really just want to know what is the proper setup procedure for a slightly tweaked car.
If you're just accepting that the car's tweaked, maybe it would be best to just put the car on 4 scales and get the corner weights right.
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Old 02-15-2019, 04:22 PM
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Every car will have some tweak unless you're really OCD. Even Martin Hudy has some tweak in his setup video and he compensate it by adjusting the spring collar. I'm just confused about what happens afterwards, after you adjust the preload collar, do you then put it back on the setup board or just leave it alone.
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Old 02-15-2019, 05:17 PM
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After you adjust the spring collars, you put it on the track. Spring tension won't really affect camber, caster, toe, and will minimally affect ride height, droop, and roll center.

If you have to drive a tweeked chassis, the best way to get left and right turns to feel the same might just be with radio settings.
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Last edited by xevias; 02-15-2019 at 10:05 PM.
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Old 02-15-2019, 06:37 PM
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Thank you Xevias. Exactly the answer I'm looking for.
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Old 02-15-2019, 09:00 PM
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i adjust tweak in a slightly different way. it really only applies to tweak that doesnt come from the usual places that can be repaired. I put solid turnbuckles on in place of all of the shocks and I put setup wheels on. I adjust everything to level with the turnbuckles. the car must also be pretty balanced left to right and front to rear.

It difficult to describe how to use the calipers but i set the calipers vertical and pick up the rr axle with the id measuring part of the caliper until the fr wheel just comes off the setup board. I then do the same thing to the lr wheel. if the fl tires come off the ground at the same distance the twist compliance is the same on both sides and the car will accelerate perfectly straight.

if its off by more than a mm i release the top front of the top deck but leave the screws a hair tight. i then twist the chassis by hand slightly and tighten the front deck. I do the left to right lift againand repeat the twist until the lift is dead even on both sides.

if everything else that you normally adjust for tweak has been checked out and you get the left to right twist even using the top deck corner weights, ride heights, and preload collars all get symetrical and easy to adjust.

because the stuff you have mounted to the top deck like double sided tape and so on stiffens different parts of the chassis you have to slight over twist the chassis in some cases to make sure it twist evenly on both sides. you will at some point have to re-adjust ride height i you have allot of tweak but eventually the ride height will be flat and the flex from left to right will be even.

what i found is that large holes or things mounted to the chassis with the super stick 3m tape will make the car prone to tweaking easily so i avoid chassis with large asymmetric holes and mounts. if you mount esc and receiver to a seperate piece of carbon stock and use 1 small piece of tape to mount the stock to the chassis the car will flex symmetrically.
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Old 02-16-2019, 06:46 PM
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Looking thru the hudy set up guide it says to adjust tweak using shock preload as a last resort. From my understanding they want you to check shock lengths equal droop, etc. If I loosen most screws below chassis and top deck. It usually untweaks my car and I dont have to adjust it using the shock collars.

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