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View Full Version : Car is loose on left hand turns only.


double_green
2010.10.06, 10:52 AM
Hi guys,

I am experiencing what I believe to be a tweak issue on my MR-03. Before I get to the problem I will list the setup of my car and the track type.

RCP (2 - Wide Ls)
MR-03 chassis (94 wheelbase)
PN MM LCG motor mount
PN Carbon T-plate (Soft)
PN Alum 0 Deg Toe Tie Rod
PN Dual Spring Center shock set
PN Multi length disk damper set
Full bearings
Kyosho 30 Deg Radial (front)
Kyosho 20 Deg Wide Radial (rear)
Kyosho Wheels 0 Deg (fr and rr)
30 Weight oil on the disk damper

Basically, my car is loose on left hand turns (sweepers, chicanes, short shoot, etc). On right hand turns the car is planted and very easy to drive. The car tracks straight on and off power. I'm also running brand new tires. I'm going to try a new T-plate from Reflex Racing. Is there anything else I can try to resolve this issue?

-John

EMU
2010.10.06, 11:53 AM
What differential are you using, and is there any binding with it on the motormount bearings. There should be at least 1mm play on the axle to prevent binding.

Can you post a couple images of the setup, primarily the damper and motor wiring... what body are you using?

double_green
2010.10.06, 12:20 PM
What differential are you using, and is there any binding with it on the motormount bearings. There should be at least 1mm play on the axle to prevent binding.

Can you post a couple images of the setup, primarily the damper and motor wiring... what body are you using?

I am using the PN Light Weight V2 Ceramic Ball Differential Set. I will need to check tonight to see if there is enough play on the axle to prevent binding. I can can confirm that the diff action is very smooth. I will also snap some pictures of the damper and motor wiring.

I'm using the Kyosho RM Xanavi Nismo Z 2007 body (MZP325XN). The front lip spoiler, bumper canards, and tow hook have been shaved off. I am using the original wheels that came with the Autoscale set.

Mike Keely
2010.10.06, 06:46 PM
Are you using tape to hold the tires to the rims? A lot of the tires today are very soft and the outside part of the tire will roll up a very small amount. It may not seem like much but it takes most of the patch of tire away from the track surface and will cause you to spin out. The tires get worse when they get worn down more.

Check this out.
http://www.reflexracing.net/tire_mounting.asp

The only thing that I do differant is that I buy Krazy glue with a brush applicator to make it easier. Hope this helps. MK

double_green
2010.10.07, 09:36 AM
I took a picture of the motor mount and damper area. I'm not exactly sure where the motor mount bearing is located but there is no play in the axle/differential area. As mentioned before, the diff action is very smooth. The rear wheels are tightened snug (unlike the front). The front wheels are tightened enough to ensure they spin very free but won't wobble. On my 10th scale TC I would check for tweak in this type of situation. If one side handles differently I found that it was either chassis tweak, uneven shock preload, uneven tire wear left to right, weight balance, etc.

I am not using tape and/or glue to hold the tires. I'm going to order the double sided tape from Reflex racing to use on my existing wheel/tire set. I'm also ordering a set of Atomic S6 wheels to mount a new set of tires with glue. I plan to run stock only so I'm hoping that tape will do the job.

Although I believe that this will improve the over handling and consistency, I'm a little suspect on this being the root cause. I would think that the tire moving/shifting/rolling up around the wheel will cause handling issues on both turns. Having said that I do know the ill affects of handling caused by improperly glued tires. This will definately be on the to do improvement list.

30674

CristianTabush
2010.10.07, 09:49 AM
John, I think we talked on the phone about this. Try setting the tweak like we discussed. Or simply try a new T-plate. I also see you are running the PN Top shock. I would check to make sure it does not bind when moving side to side. This used to happen to mine and cause erratic behavior, hence the reason why I went away from these. The top spring is also pretty stiff, so I would try to install one of their aftermarket ones. With a disk damper, you don't need that stiff of a top spring, maybe their orange or red would do best.

double_green
2010.10.07, 10:47 AM
Hey Cristian - Yes, we spoke over the phone. I'm putting my 'grocery list' together and wanted to make sure I got everything. The Reflex T-Plate and the Kyosho Laser-cut shims (0.2mm) is a definte along with the other items we talked about.

Per your recommendation I also checked and verified the centering of the damper. I can confirm that it does not center when the right rear wheel/tire is pushed down and released. When the left side is pushed down and released it centers perfectly. I'm not sure if is due to the T-Plate or the PN center shock.

I'm disappointed to hear about the potential issues with the PN center shock. I don't believe mine is binding but something is causing the damper to center incorrectly. I guess it's either the T-Plate or the center shock. Can you point me to the aftermarket springs for the PN center shock? I guess I can also go thicker in the oil I put on the damper to offset the stiff springs. I'm not sure if this works in the Mini-Z world.

When we spoke I brought up my concerns of the body and it's affect on handling. I brought this up because when I ran the car without the body the problem went away. Spending some time to think about this, I now think that the extra weight of the body may have simply exagerated the issue that was always there. I may hold off on the new body. Can you recommend the offset for the S6 wheels for the Nismo Z 2007? Would it be the same 0 Deg front and .5 Deg rear?

At the end of the day I'm having a blast driving these cars. The fact that I have a track setup at my home is a plus!! The learning curve is a little steep but I'm thankful and aprreciative of support from the members of this board and vendors.

EMU
2010.10.07, 11:03 AM
Are motor wires hitting the body, restricting the shock from travelling?

double_green
2010.10.07, 11:52 AM
The motor wires were barely touching the body. I moved the wires so that they won't touch. While I was checking this I went ahead and checked the ride height and other suspension related items with the body on.

I think I may have found the issue. When I settle the car on a flat surface, the driver's side rear is higher off the ground then the passenger's side rear. It's important to note that this measurement is by eye and of the body and not the chassis. I do not have a ride height gauge to measure the chassis ride height. It's likely that the rear of the passenger's side is scraping the ground through left hand turns. Do they make micro size ride height gauges?

Another test I performed was compressing the shocks on each side. When I press down on the driver's side rear it returns to a higher position then on the passenger side. I also compressed the shocks on the center of the rear (both rear shocks compressed) and when released the driver's side rebounds higher off the ground.

CristianTabush
2010.10.07, 12:15 PM
I would go with 0.5F and +1R with that body. Also notice how we trimmed out 350Z's in our pics from our articles, it helps a bit to get proper clearance.

The body will exaggerate the tweak issue, which is exactly what is wrong with your car. I can guarantee it.

For the Optional spring set on the PN shock, the part number, I believe is MR2162 or MR2161 (1 is the shock, 1 is the springs). Use the orange or red one.

Sometimes the body clips are mounted at different heights on the bodies, these are hand assembled after all. I would suggest to see the low side, break the clip off carefully using perhaps a screwdriver for leverage and re installing it to level the body off.

Atomic makes a ride height gauge kit for these, but again, any wedge shaped gauge, from any scale can work as well.