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Old 02-22-2012, 08:54 PM   #1636
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Got the car (FGX/Rabbit) out on the track for the first time tonight. Started off with a huge on-throttle push in the car, the only way to get around a corner was to come up and brake hard to get the weight transferred back to the front then turn in. The back end was also dragging a little on throttle. So I rebuilt the rear shocks and added about 30g to the front end. Those two things definitely helped out, but it's still got a push in it, I think I need some softer front springs, harder rear springs, and some more weight over the nose to really bring the car into the fast laps. I'm running on very high bite carpet. Any other suggestions on getting the push out?
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Old 02-22-2012, 09:37 PM   #1637
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Got the car (FGX/Rabbit) out on the track for the first time tonight. Started off with a huge on-throttle push in the car, the only way to get around a corner was to come up and brake hard to get the weight transferred back to the front then turn in. The back end was also dragging a little on throttle. So I rebuilt the rear shocks and added about 30g to the front end. Those two things definitely helped out, but it's still got a push in it, I think I need some softer front springs, harder rear springs, and some more weight over the nose to really bring the car into the fast laps. I'm running on very high bite carpet. Any other suggestions on getting the push out?
Get the fgx aluminium motor mount and bulkhead. Do the necessary grinding for the mount and the right side front suspension mount and add a 1.5 mm shim under the front mount so the arms have some angle. You should be amazed with the difference in on throttle steering. shaved 0.3 seconds a lap for me. I went from a huge push exiting the turn to a very driveable car. Not perfect yet but getting there.
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Old 02-22-2012, 09:54 PM   #1638
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Get the fgx aluminium motor mount and bulkhead. Do the necessary grinding for the mount and the right side front suspension mount and add a 1.5 mm shim under the front mount so the arms have some angle. You should be amazed with the difference in on throttle steering. shaved 0.3 seconds a lap for me. I went from a huge push exiting the turn to a very driveable car. Not perfect yet but getting there.

Antis squat is nice isnt it??!!!

I couldnt keep driving with Sabastian he will not stop swerving at the starts!! so went back to Lewis
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Old 02-22-2012, 11:48 PM   #1639
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That setup looks very familiar... You'll smile the whole time you test. The grooved tires bark and chirp when you corner hard. I do drive this car just for the pure fun of it. And I love that color! Nice build all the way around.

Hey John yeah u we're right I had a blast till I hit the wall andbroke upper arm and a kingpin, so I modded the front end with turn buckles. Also found another manufacturers kingpin that fits and seems stronger.

I tell ya what though the setuP I copied from u felt madddddddd! I had grip like u wouldn't believe on a extremely dirty and dusty track. Had tyres chirping around every corner
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Old 02-23-2012, 06:35 AM   #1640
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Get the fgx aluminium motor mount and bulkhead. Do the necessary grinding for the mount and the right side front suspension mount and add a 1.5 mm shim under the front mount so the arms have some angle. You should be amazed with the difference in on throttle steering. shaved 0.3 seconds a lap for me. I went from a huge push exiting the turn to a very driveable car. Not perfect yet but getting there.
Well the car already has the aluminum motor mount on it and the F103 front end. with aluminum camber adjustment plate. I'll post a pic tonight of it's current setup. Can you get a pic of the shim placement your talking about?
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Old 02-23-2012, 06:46 AM   #1641
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Well the car already has the aluminum motor mount on it and the F103 front end. with aluminum camber adjustment plate. I'll post a pic tonight of it's current setup. Can you get a pic of the shim placement your talking about?
look closely at the front arm mount:



On your push issue, i say get rid of the 103/104 front end, one of the reasons you are getting push is two fold. The first is the fact that you have virtually eliminated all of the flex from the front which in turn gives you less traction on that end, hence front end push. Secondly balance is very important on these "bannana chassis" cars , and i dont mean weight balance , i mean traction balance from one end to another. The FGX creates more rear grip than a DD car therefore you can have more aggressive steering to keep the balance. We all know that traction and grip is limited on DD cars and this is one reason why the current trend in DD cars is to go with a softer compound in the front and harder in the rear this is done more or less to get the rear to rotate but it is a fine line and makes the car hard to drive on anything except for the "fast" line on the track. Great for qualifying horrible for close racing. Troy touched on this a few pages back and I believe he will agree. The FGX needs to be tuned differently than a DD chassis in pretty much all aspects and when the new front suspension comes out we will more than likely be outlawed from ROAR (Im calling it!!). IMO the rabbit conversion was created mostly due to the fragile front end on the FGX. not for performance. So what i think you are seeing with the conversion on your car is simply the fact that you have taken steering away via no flex in the front from a chassis that has lots of rear grip.
Now of course not everyone is going to agree with me and that is fine and there are alot of people out there with the rabbit conversion so if you plan on keeping it than you need to get your balance back. So this means that you need to get the rear to rotate and there are a few things you can try. Since the rear is so adjustable you should be able to get close! First thing I would do is go with the stiffest rear sway bar. If that is not enough than stiffen up the rear springs, maybe even shim the cantilevers for more leverage (the side that connects to the shock .5mm). Anti squat will help also as well as decreasing your rear camber ( like 0 or-.5*). Because of the rear dynamics you can tune the car to have controllable drift so dont be afraid of using harder tires in the rear.

Let us know!!

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Old 02-23-2012, 05:08 PM   #1642
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So one stopping stopping factor for me waiting on getting this car is a foam tire setup. One of my local indoor carpet tracks has a F1 class that is foam only. I know 3racing has wheels out, but what foams do I glue on them? I will pull the trigger on the car if I can get a solution for foams.
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Old 02-23-2012, 05:36 PM   #1643
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Can I get a few pics of how you guys have your electronics mounted? I'm having a heck of a time getting everything stuffed in there.
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Old 02-23-2012, 05:58 PM   #1644
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Originally Posted by MantisWorx View Post
look closely at the front arm mount:



On your push issue, i say get rid of the 103/104 front end, one of the reasons you are getting push is two fold. The first is the fact that you have virtually eliminated all of the flex from the front which in turn gives you less traction on that end, hence front end push. Secondly balance is very important on these "bannana chassis" cars , and i dont mean weight balance , i mean traction balance from one end to another. The FGX creates more rear grip than a DD car therefore you can have more aggressive steering to keep the balance. We all know that traction and grip is limited on DD cars and this is one reason why the current trend in DD cars is to go with a softer compound in the front and harder in the rear this is done more or less to get the rear to rotate but it is a fine line and makes the car hard to drive on anything except for the "fast" line on the track. Great for qualifying horrible for close racing. Troy touched on this a few pages back and I believe he will agree. The FGX needs to be tuned differently than a DD chassis in pretty much all aspects and when the new front suspension comes out we will more than likely be outlawed from ROAR (Im calling it!!). IMO the rabbit conversion was created mostly due to the fragile front end on the FGX. not for performance. So what i think you are seeing with the conversion on your car is simply the fact that you have taken steering away via no flex in the front from a chassis that has lots of rear grip.
Now of course not everyone is going to agree with me and that is fine and there are alot of people out there with the rabbit conversion so if you plan on keeping it than you need to get your balance back. So this means that you need to get the rear to rotate and there are a few things you can try. Since the rear is so adjustable you should be able to get close! First thing I would do is go with the stiffest rear sway bar. If that is not enough than stiffen up the rear springs, maybe even shim the cantilevers for more leverage (the side that connects to the shock .5mm). Anti squat will help also as well as decreasing your rear camber ( like 0 or-.5*). Because of the rear dynamics you can tune the car to have controllable drift so dont be afraid of using harder tires in the rear.

Let us know!!
m
Awesome information. Thank you. I was fighting a push both with the fgx front end and the rabbit front end. You nailed it on me. Rabbit for durability. I started with the hardest sway bar, hardest f201 springs 80wt shock oil and no rear droop. Mostly to keep the inside front tire on the ground in a turn. I have since raised the front ride height, put soft springs on the front, shimmed the wheels out 3 mm up front, shimmed the wheels out 2mm in the rear reduced front Ackerman added 1.5 mm of anti squat and installed a shorty lipo as far forward as possible. My on power push is pretty much gone.

Believe it or not I think I am having a problem with the rear being too stiff. My tires will severely squeal in the turns and you can see the car almost come to a stop because the rear seems to be sliding and breaking the car in the turns. It is definitely bleeding speed. Severely. I added 1mm of droop, changed to the softest f201 springs lowered the shock oil to 70wt and switched to a medium rear sway bar. Also changed the diff fluid to 80wt shock oil. Its getting better but its not gone and you can see the front tire starting to get light again. Currently using shimizu grooved soft in the rear and soft up front when traction is low and medium when traction picks up throughout the day. Running on high traction carpet.

I lowered the rear roll center but the car began to traction roll in the sweeping right hander. It also got really light at other points of the track. It is lower than the stock fgx but not as low as I would like.

Any thoughts?
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Old 02-23-2012, 06:18 PM   #1645
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m
Awesome information. Thank you. I was fighting a push both with the fgx front end and the rabbit front end. You nailed it on me. Rabbit for durability. I started with the hardest sway bar, hardest f201 springs 80wt shock oil and no rear droop. Mostly to keep the inside front tire on the ground in a turn. I have since raised the front ride height, put soft springs on the front, shimmed the wheels out 3 mm up front, shimmed the wheels out 2mm in the rear reduced front Ackerman added 1.5 mm of anti squat and installed a shorty lipo as far forward as possible. My on power push is pretty much gone.

Believe it or not I think I am having a problem with the rear being too stiff. My tires will severely squeal in the turns and you can see the car almost come to a stop because the rear seems to be sliding and breaking the car in the turns. It is definitely bleeding speed. Severely. I added 1mm of droop, changed to the softest f201 springs lowered the shock oil to 70wt and switched to a medium rear sway bar. Also changed the diff fluid to 80wt shock oil. Its getting better but its not gone and you can see the front tire starting to get light again. Currently using shimizu grooved soft in the rear and soft up front when traction is low and medium when traction picks up throughout the day. Running on high traction carpet.

I lowered the rear roll center but the car began to traction roll in the sweeping right hander. It also got really light at other points of the track. It is lower than the stock fgx but not as low as I would like.

Any thoughts?
Try raising the rear roll center, i have been meaning to CAD up the rear geometry just havent had the spare time to do it. Ok so i just sketched the rear geometry out on a piece of paper and there is no real roll center??? because of the angle of the lower arm the upper arm will never cross its path! I am going to draw it up and post later tonight. You want to try and get the arms as close to parallel as you can so this means the upper inside link needs to be spaced down ALOT!! I did this on my car and it works wonders. I think this is one of the reasons the car acts kinda funky with settings not only do you not have a true front roll center (king pins) and the rear roll center is somewhere in lala land. Using a rear only sway bar is always going to have a tendency to lift the inside front tire which leads to traction rolling. Try tuning your car without the rear sway bar or a very light one.
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Old 02-23-2012, 07:28 PM   #1646
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Here's the car in it's current setup. I wonder if I could just cut those rear mounts off the bulk heads to be able to shim them up like in your picture. I took the weight off the front also, I need to find a better mounting for it on front. I also need to figure out this final drive, after about 10 minutes on the track the motor was at 190, this is in blinky mode 21.5 with a 34t pinion and the spur is a 35t. So how do I calculate this final drive?

Thanks









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Old 02-23-2012, 07:44 PM   #1647
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FDR is spur / pinion x internal ratio. In your case 35 /34 x 2.71 = 2.79. I'm running a 3.05 and doing ok temp wise. About 140. Opening the body vents helps a lot.
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Old 02-23-2012, 07:47 PM   #1648
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Try raising the rear roll center, i have been meaning to CAD up the rear geometry just havent had the spare time to do it. Ok so i just sketched the rear geometry out on a piece of paper and there is no real roll center??? because of the angle of the lower arm the upper arm will never cross its path! I am going to draw it up and post later tonight. You want to try and get the arms as close to parallel as you can so this means the upper inside link needs to be spaced down ALOT!! I did this on my car and it works wonders. I think this is one of the reasons the car acts kinda funky with settings not only do you not have a true front roll center (king pins) and the rear roll center is somewhere in lala land. Using a rear only sway bar is always going to have a tendency to lift the inside front tire which leads to traction rolling. Try tuning your car without the rear sway bar or a very light one.
When you say get the arms parallel are you referring to the relation between the upper link and the lower arm?
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Old 02-23-2012, 08:05 PM   #1649
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FDR is spur / pinion x internal ratio. In your case 35 /34 x 2.71 = 2.79. I'm running a 3.05 and doing ok temp wise. About 140. Opening the body vents helps a lot.
Yeah I had not opened the air scoop up yet, 2.79, no wonder it was slugish off the corners, it's take half the straight to get upto speed, most VTA and USGT cars run 3.6 to 4.0 FDR.
I have the gears for 3.6 so we are gonna try that out next time.
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Old 02-23-2012, 08:10 PM   #1650
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Yeah I had not opened the air scoop up yet, 2.79, no wonder it was slugish off the corners, it's take half the straight to get upto speed, most VTA and USGT cars run 3.6 to 4.0 FDR.
I have the gears for 3.6 so we are gonna try that out next time.
Try the 3.6 but be prepared to go lower. I run vta at 3.84 but f1 at 3.05 on the same track. The 21.5 has a lot more torque to give.

Definitely open the vents. It helped me 15-20 degrees. I have also found a smoother driving style keeps temps down.
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