View Full Version : You would think I'd know this stuff by now!

2012.07.04, 11:46 PM
Ok, here's the problem I got with this car now...

I've got an MR02 2.4, gold terminal chassis, PN front A-arm w/purple springs PN 98 motor mount, medium kyosho plate, PN disc dampener with red top and green bottom spring, top spring is spaced. 64pitch 52 spur, 13 tooth pinion, Xspeed in PN can. Running fresh K20s rear and semi-worn K30s front taped on Mosler wheels. PN high clamp plate mount.

At least that is where it is after a few hours of tuning... and the car still kicks the a$$ end around like hell on exit of right hand turns!

Here's the rundown of things I've checked/changed:

Tires, tried a bunch... Current combo makes it work best

Diff, swapped 2 diffs into it, varied adjustments, still kicks out.

Radio settings, duh... all looks good though, dialed down right a bit more than left but really kills the entry too much if I go too far.

H-plates, tried about 5 different ones from wides, to narrows, to fiberglass... still does it.

Bodies, Mazda LM, McLaren F1, Murch... No rubs on any of them.

Front springs, White, Silver, Green, now Purple...

Wheel offsets, 0s, 1s in the front, 1s, 2s in the rear... Currently 2 front, 3s rear. Seems to have calmed the car down bit still hook right on exit.

Been at this for a while now, I've checked for tweaks, binding, set the droop on the front too many times to count. Front is equal side to side... nothing is binding. I've even changed bearings to make sure there isn't one locked up.

Rare for me to sit and fight with a car like this but I've tried everything as far as I know and I'm still ending up with the same result. I've eyeballed the chassis and tires for tweak, there is none.

Just trying to match a exact setup I have on another car I have that runs excellent and I end up fighting what feels like a tweak, but it just doesn't seem to be there.

Scratchin my head on this for a while now... any experts out there that may know something I'm missing?

2012.07.04, 11:59 PM
is the rear wheel bearing shot?

2012.07.05, 12:04 AM
Did you make sure the car turns left and right equally on the track? I put the car's side against the straight rcp rail, turn the steering wheel full lock and go slowly with the throttle. Then repeat for the other side. Make sure that the radius is the same (you have to eyeball this but it isn't that hard).

Now that your car should turn equally left and right, it would bea good idea to test it on the straightaway. I go full throttle reverse, then quickly go full throttle forward. If the car shoots off to one side, use the st trim on your radio to adjust the opposite side. This test helps the car track straight.

Sounds like you have tried a lot of different parts, which makes me think this is more of a steering radius issue. I would just revert your car back to the setup that works good and then do the two tests that I mentioned above. Sometimes my car hooks to one side, so when I adjusted my balance and set the trim it fixed my problem. Hope this helps. :)

2012.07.05, 08:01 AM
is the rear wheel bearing shot?

Swapped them all out, still no change. Did both shoot and rail test too, the car seems to launch good. I even tightened the diff up before I did the shoot test to guarantee that the wheels were equal on launch. Seems like it's only on turns.

Got a very interesting PM though and it's something I wouldn't have thought to check... He knew the exact motor pod I'm running just by my issue. I will update as soon as I get some tune time tonight!

2012.07.05, 08:19 AM
my guess would be trust bearing is going bad or is dry. also could be the wheel is to tight on the thrust bearing. i have been having this problem with pn's new shafts

2012.07.05, 08:23 AM
the mentioning of a motor pod jogged my memory. But mine was bad due to a wreck, in which case it got bent.

2012.07.05, 11:31 AM
my guess would be trust bearing is going bad or is dry. also could be the wheel is to tight on the thrust bearing. i have been having this problem with pn's new shafts

I thought that as well, rebuilt the first diff and still kicked out, threw another freshly rebuilt diff in and got the same thing. I always back off the wheel nuts a bit too, and I do try to keep a bit of side to side wiggle on the diff (just a half hair). I also am using thin steel washers on both sides that really just contact the inner race of the bearings. The shaft looks straight, rolls without wobble.

I also changed out the bearing carriers from #2s to #1s. It is the PN 98-102 mount, the one with the carbon "k" on top.

I've flipped the H-plate as well, and tried all kinds of combos. I even hit one up with a lighter to erase it's memory. Yes, bend carfon fiber enough and it will break bonds in between the fibers in one direction, my lighter trick has worked in the past. The side to side rotation on the rear feels even now with the newer Kyosho plate. I did throw one older one some lighter action to make the left rear plant harder, and it did take a bit of the kickout away, but really killed the entry into both right and left turns.

My desk is covered with all kinds of parts right now... looks like I'm working 5 cars at once.:o

2012.07.05, 11:43 AM
Do you have a different front end you can try? I know this sounds extreme, but I had a similar problem with one of my best cars. I just couldn't get it to work right. I couldn't get anything to work for any length of time. I finally decided to rip the PN A-Arm off and swapped over to a spare RR set up I had. Problem solved.

2012.07.05, 12:10 PM
ed, not sure you remember but that was the same problem i was having with my F360GTC at the BTE in downtown DC a year or so ago, the last time you attended. no matter what i changed the car still hooked in one direction.
i don't recall anymore what i did to correct the issue. i may have replaced the car. i do know that everyone in our club looked at the car and in the end only slightly dialed down the issue.

i wish you the best of luck. it drove me nuts :rolleyes:

2012.07.05, 12:37 PM
Try taping the bodies tight to the car. Some bodies I have raced including the murc rattle around on the chassis causing the rear of the car to spin out a lot. Run tape around the body while pinching the body tight against the chassis. And something I discovered a while ago is that some wheels fit too tight to the diff side leading people to run with the lock nut on the diff side loose. I've found that sanding down the hub on the wheel that goes against the diff with fine grit sandpaper( I use 2000 grit ) to the point that you can tighten down the wheel without it locking up and the diff feels butter smooth and not gritty made a world of difference. Plus try driving the car around the track without a body on it. I know it sounds stupid but if a body is causing a problem then you'll know.

2012.07.05, 01:55 PM
^ What he said above is an issue I and other locals ran into also. Maybe it is just the rims you use that bind up the bearings on the right side.
When I tightened the locknut all the way with almost any plastic wheel, the diff would lock up and I would have to loosen the diff. Now, I use PN delrin rims and the newest pn diff shaft and the bearings fit in great and I actually have to run a tighter diff setting with the lock nut tightened all the way.

2012.07.05, 01:58 PM
Yeah, I remember you had the same issue Ray. This isn't the only time I've had this happen as well, but like you, I too can't remember a real solution. Usually if a car gives me this much of a problem I end up shelving it and moving on to the next car... but I'm on vacation at home for once and got free time and it's too freekin hot out for yard work! :rolleyes:

Body contact and shift is something I checked for, even ran it without a shell and it still kicked (not stupid, just simple). I also have a habit of heating up my long allen wrench and melting the side clips where they go into the chassis so they go into that slot tight and secure. Maybe about a 2mm melt-in in the outboard direction just enough to take the rattles out. Another low-tech fix for everyone, just don't heat it up too much and touch lightly at first.

The Mosler wheels do go onto the bearings tight, I may check that when I get back down there tonight.

2012.07.05, 02:33 PM
did you check the motor wire? I have the same problem b4 and later found out that one of the motor wire is hitting the disk of the disk damper on one side.:eek:

2012.07.05, 03:24 PM
Got it!

Thanks to all with help on this shake-down!

What I've learned... Sometimes a simple test leads to a simple solution!

I got a PM from mleemor60 where he suggested a simple push-down on the front end, one side at a time. (oh yeah... now I feel real dumb, I did know this!) So, I got out my exacto and gave the right side front a push down right at the A-arm pin lock. Both rear tires stayed planted until near full compression. Did the same to the left side of the front end and with the slightest pressure, the right rear would do a levitation act!

So right away, I'm thinking every H-plate I have is just really tweeked out. So I grab a nearly new PN5 fiberglass to soften it up so it will rotate freely back there. Drop it onto a flat surface and repeat the test... Still does its levitation.

Now I'm searching for anything that may be binding up, motor wires were clear of the dampener post and the dampener itself felt free in both directions?I'm on a mission now so I take off the dampener. Seems ok but there is just a little bit of sticktion on the one side. I make up my mind to swap out the springs and I went with a red bottom and an old reject but soft silver spring on the bottom. And gave the disks a new coating of Ruby Lube.

Repeated the test and both rears stayed planted! Tossed it onto the track, and wouldn't you know it, the thing is running good! Success!

Ended up swapping rear tires to something a bit less sticky than fresh K20s and dialed a bit more steering into the radio. Now I've got something to work with!

A simple test showed the way. I did give the front end a push down last night to meke sure the front suspension was reacting equally side to side, I just didn't think to do the one side at a time push.

Disk dampener maintenance and physics is something I really need to pay more attention to from here on out!

Thanks all! Now onto my next setup! :D

2012.07.06, 04:14 PM
I'm on a mission now so I take off the dampener. Seems ok but there is just a little bit of sticktion on the one side. I make up my mind to swap out the springs and I went with a red bottom and an old reject but soft silver spring on the bottom. And gave the disks a new coating of Ruby Lube.

Repeated the test and both rears stayed planted! Tossed it onto the track, and wouldn't you know it, the thing is running good! Success!

Glad you found success. I'm pretty sure swapping the spings didn't fix your problem, so are you saying it was the "sticktion" that was causing the problem?

2012.07.06, 08:53 PM
Hard to say... I think one may help the other. There was still a trace amount of lube on the dampener when I took it off so I'm going to say that the softer springs did help out. I did have a brief conversation about this with Davey G up at the MHS race too in regards to dampener performance but I don't think this was a centering issue like we discussed, I think this was a bad sprimg choice for this particular setup.

Oh, I not only changed the springs but the plates too. I went from some old-school Atomic, black delrin plates to the newer PN style, white delrin or nylon ones. This could've played a major role in my dampeners new freedom level.

Played wih the tires and radio a bit more last night and really got this car flying now. Going out of the turns with great predictability now.

2012.07.07, 12:23 AM
nice... i feel like i just learned some stuff about the mr-02 in this read.:)