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View Full Version : Stock MR-03 can't take a corner on RCP?


BlackBerry
2012.01.09, 05:11 PM
I picked up a Murcielago SV the other day and ran it at my local RCP track. Out of the box I installed Kyosho 20 radials in the back and Kyosho 30 slicks in the front and a PN 50T non-BB motor. The car would literally 180 at every corner, and either 180 or flip after the straight depending on how I entered the corner. It was a nightmare to try and keep it on the track.

After watching a video on youtube of a stock MR-03 on RCP with the same tires run perfectly fine I'm assuming the cause of the horrible oversteer was the PN 50T as the gear diff can't distribute the power properly perhaps (one wheel spin)?

At the time my thinking was the rear suspension was just so bad so I didn't bother attempting to run the stock motor, but after watching that video on youtube and thinking back on it now I was probably wrong.

Would a diff solve this problem? I don't expect the car to handle perfectly, I know that will take a bit of mods, but will I at least be able to get it around the track with the 50T motor.

Thanks,

BlackBerry

Rune
2012.01.09, 05:32 PM
If you go with Radial 20 rear, and 30 slicks up front I would think you have the solution.

20 radial up front is way to soft, and the 30 radial rear is not very grippy.

BlackBerry
2012.01.09, 05:36 PM
If you go with Radial 20 rear, and 30 slicks up front I would think you have the solution.

20 radial up front is way to soft, and the 30 radial rear is not very grippy.

That was the setup, i just incorrectly typed it in my OP. Fixed.

BlackBerry

briankstan
2012.01.09, 05:52 PM
check for the shock hitting something the body, a broken or tweaked t-plate or something like that. also make sure that diff isn't locked (meaning that if your running the gear diff that he wheel nut are not on too tight. especially the one opposite the pinion side.

if the top shock is hitting the body and not allowing movement is will also cause this to happen.

blt456
2012.01.09, 05:57 PM
I think it's just the diameter of the front wheels and the suspension. From the factory, the suspension has a good amount of travel and ride height, which you can obviously tune. When I ran full size front tires on my new 03 (only has PN racing front springs), it would do the same thing. I turned down the steering travel and balance but that messed up my steering. (wide diameter)

If you ask the track owner, he/she will probably be able to point you in the right direction. Just to start out, you will probably want to get some front springs (check PN's website) and some shims. Then, look into someone truing your tires to a smaller diameter. 23mm with kyosho 30 slicks on 20mm rims in the front is a good starting point.

kwsmith29
2012.01.09, 06:12 PM
Getting the front tires trued flat will help also.

Wade Smith

color01
2012.01.09, 06:13 PM
With a 100% non-damped rear suspension, I've noticed there's enough suspension chatter to flip the car at the end of a straight/beginning of a high-speed sweeper even on the stock 70t motor. 50t is definitely asking for it -- the stock rear end won't accept that kind of power without at least a little bit of damping action. At Kenon we stuff some Kyosho 30,000wt diff grease into the top shock to smooth out the cars a teensy bit and it actually improves the bad behavior you're experiencing.

The Murcielago SV is also rather narrow in the front with its +0N front wheels. The MR03's super fast steering response can lead to traction rolling and oversteer with this wheel offset -- the easiest-to-drive Box Stock MR03s tend to be the wide ones, such as the HSV, GT-R and 599XX. The wide offset front wheels (+2N or +3N) soften the steering response to reduce oversteer and rolling over. You can get around this behavior on the Murc SV by truing the front tires, as BLT noted, but because of the body's required offsets you will always have to work around its distinctive characteristics.

imxlr8ed
2012.01.09, 07:00 PM
Sounds like tire/body rub to me as well.
The Murch is finicky with new tires and soft front springs. I usually grind my headlight tubs out a bit to avoid this, but with worn or trued tires... the clearance is way better.

BlackBerry
2012.01.09, 07:19 PM
check for the shock hitting something the body, a broken or tweaked t-plate or something like that. also make sure that diff isn't locked (meaning that if your running the gear diff that he wheel nut are not on too tight. especially the one opposite the pinion side.

if the top shock is hitting the body and not allowing movement is will also cause this to happen.

Nothing hitting shock, t plate fine, also checked lock nuts day of (thought that was it too).

I think it's just the diameter of the front wheels and the suspension. From the factory, the suspension has a good amount of travel and ride height, which you can obviously tune. When I ran full size front tires on my new 03 (only has PN racing front springs), it would do the same thing. I turned down the steering travel and balance but that messed up my steering. (wide diameter)

If you ask the track owner, he/she will probably be able to point you in the right direction. Just to start out, you will probably want to get some front springs (check PN's website) and some shims. Then, look into someone truing your tires to a smaller diameter. 23mm with kyosho 30 slicks on 20mm rims in the front is a good starting point.

I don't think I have access to a tire truer, maybe I can run smaller diameter wheels? My track has the various diameter PN dish wheels all the way down to 18mm. What diameter are kyosho wheels?

With a 100% non-damped rear suspension, I've noticed there's enough suspension chatter to flip the car at the end of a straight/beginning of a high-speed sweeper even on the stock 70t motor. 50t is definitely asking for it -- the stock rear end won't accept that kind of power without at least a little bit of damping action. At Kenon we stuff some Kyosho 30,000wt diff grease into the top shock to smooth out the cars a teensy bit and it actually improves the bad behavior you're experiencing.

The Murcielago SV is also rather narrow in the front with its +0N front wheels. The MR03's super fast steering response can lead to traction rolling and oversteer with this wheel offset -- the easiest-to-drive Box Stock MR03s tend to be the wide ones, such as the HSV, GT-R and 599XX. The wide offset front wheels (+2N or +3N) soften the steering response to reduce oversteer and rolling over. You can get around this behavior on the Murc SV by truing the front tires, as BLT noted, but because of the body's required offsets you will always have to work around its distinctive characteristics.

When you say you put grease in the top shock I assume you mean the oil filled shock and not the stock unit? Do I need a disc/side dampers or will an oil shock with springs do the trick for now?

I would have gone with the 599xx if I knew at the time that offsets for mini-z were inverted compared to real cars (I though +3 was narrower). The SV was cheaper so I thought I would put the saved money towards another body I actually wanted.

To overcome the bodies unique characteristics for now I have decided to just run the same offset front and rear. If I run a 19mm front wheel can I run any higher offset than 0 on the SV? Or should I run the PN 18mm wheel in 0 offset to reduce overall diameter? Can someone explain to me how truing the front tires reduces traction rolling and oversteer?

Sounds like tire/body rub to me as well.
The Murch is finicky with new tires and soft front springs. I usually grind my headlight tubs out a bit to avoid this, but with worn or trued tires... the clearance is way better.

How much suspension travel do the front wheels get on stock springs? This might be the issue.

Thanks for all the help,

BlackBerry

unearthed name
2012.01.09, 08:44 PM
no, BB. when he says grease, he means stock top shock. pull it all apart. put the grease on the metal shaft.

can you post a picture of your car? it would be incredibly helpful to have some visual cue.

BlackBerry
2012.01.09, 08:58 PM
no, BB. when he says grease, he means stock top shock. pull it all apart. put the grease on the metal shaft.

can you post a picture of your car? it would be incredibly helpful to have some visual cue.

Got it. Didn't realize that can actually be effective, how much grease? How long does it stay there?

BlackBerry

pomme de terre
2012.01.09, 09:47 PM
Enough to feel some sort of damping effect on the shock. Keep in mind you will probably have to clean and re-grease every qualifier. And all these little hacks here and there might help a little bit, but in the end you can't get away from getting a disc or tri-damper if you want to be competitive.

As for the tires, you can expect to be traction rolling on a brand new set when running at MC3. It happens to pretty much everyone there. If you can't true, just run them in early in the day like most of us do. And you need to tape/glue your tires. It makes a big difference.

Be careful with smaller diameter wheels (stock wheels are 20mm), because they will also lower your ride height. You will want to be lowering your car from stock height anyways, but you'll need to adjust both ends. Remember, balance is very important.

Smaller wheels don't necessarily mean you can run a more aggressive offset. Maybe you won't rub, but if you poke, you will catch the walls. Hellaflush setups don't work well in racing on RCP.

Sinister_Y
2012.01.09, 10:30 PM
Chris, the murc is a good choice. You need to true down the front tires for sure and limit the front suspension travel big time so it doesn't flip or have uncontrolled oversteer at the end of the straight. i would run the stock wheel offsets not narrower. narrower will make your car weight transition even quicker, which is not what you want. if you're set on changing offsets then chane the front to a little wider than stock if it can take it. this will give you less turn in.

twinkie
2012.01.10, 12:31 AM
what transmitter are you using?

Sinister_Y
2012.01.10, 08:27 AM
he's using a KT-18

imxlr8ed
2012.01.10, 12:23 PM
The rub comes to mind only because I run 2 Murchs and my one setup had a softer front end and the rub only occured in heavy turning. Drove me nuts trying to figure out why my car was so inconsistent from one turn to the next. I then noticed a little rub mark on the inside of the body and realized what was going on. It wasn't much contact but it was really ruining the handling.

Harder front springs may get you more push into the turns, preventing roll-over. Worn tires will help as well. Tire taping the front tires to the rims will help prevent the tires outer edge from catching and also make the handling more consistent. A stiffer rear plate will also fight the weight transition from side to side too.

Welcome to the world of tuning! Hope your sanity stays intact! :D

BlackBerry
2012.01.10, 07:39 PM
And all these little hacks here and there might help a little bit, but in the end you can't get away from getting a disc or tri-damper if you want to be competitive.

If you can't true, just run them in early in the day like most of us do.


Yeah I'm not going to bother with all the little "hacks". I just didn't want to purchase parts at the track because I wasn't exactly sure what brands and setups I wanted to run. I'll be running the Reflex disc damper and a PN center shock for now so I can copy your setup. There are other parts I prefer to use than ones in your setup, but that will have to wait due to my lack of tuning skill.

Do you true your tires Jon? (is it John or Jon btw?)

Chris, the murc is a good choice. You need to true down the front tires for sure and limit the front suspension travel. if you're set on changing offsets then chane the front to a little wider than stock if it can take it.

Is there access to a tire truer at the shop? Does anyone know if the Lambo SV can take a bit higher offset in the front? I took a look at it and it seems to have room for maybe 1-1.5mm more max, but what do I know, lol.

he's using a KT-18

Unfortunately yes, till I pickup a module for my EX-1 which won't happen till the car starts to handle properly (ie: $$$). I know how valuable a digitally programmable radio can be, I hate using the Kt-18..

The rub comes to mind only because I run 2 Murchs and my one setup had a softer front end and the rub only occured in heavy turning. Drove me nuts trying to figure out why my car was so inconsistent from one turn to the next. I then noticed a little rub mark on the inside of the body and realized what was going on. It wasn't much contact but it was really ruining the handling.

Harder front springs may get you more push into the turns, preventing roll-over. Worn tires will help as well. Tire taping the front tires to the rims will help prevent the tires outer edge from catching and also make the handling more consistent. A stiffer rear plate will also fight the weight transition from side to side too.

Welcome to the world of tuning! Hope your sanity stays intact! :D

Which murcielagos are you running because I checked the clearances on my SV and highly doubt it's rubbing, no marks on the body either. I really despise tuning, that's why I'm just going to copy pomme's setup for now as a base tune :).

yasuji
2012.01.10, 07:52 PM
One of the things i dont see mentioned here is .... What tape are you using on the rear wheels/tires ?
and what tape r u usting in the front?
if any?

BlackBerry
2012.01.10, 07:59 PM
One of the things i dont see mentioned here is .... What tape are you using on the rear wheels/tires ?
and what tape r u usting in the front?
if any?

I used nothing the day of. Plan on using R246 tape front and rear.

yasuji
2012.01.10, 08:17 PM
I used nothing the day of. Plan on using R246 tape front and rear.

the k 20 radial is really soft and needs to be taped/glued... it is a good possibility that your main problem was that the tire was ballooning while diffing out!...and yes even with a 50t motor just hold one wheel and give it the stick and see what the other tire does
for sure tape the rears first and foremost.... try not taping the fronts just yet until you have tested the taped rears... taping the front tires will give you a little more front bite
i do not use the 246 tape i glue the rears and i use pn tape for the fronts!
:D

byebye
2012.01.10, 11:17 PM
A damper plate system and diff will get the rear end to settle. Oversteer means too much front grip. Your tire choice is good for front though so try a mzw17-20 on the rear.

Your motor may also cause the car to slow down off throttle faster than normal. This loads up the front end and causes a rear biased breaking affect. Try breaking in your motor and running a higher gearing.

Kris

imxlr8ed
2012.01.11, 12:40 AM
Just went down to look at the car again. My bad... That Murch has the wide track front on it. Stock offset doesn't touch the wheel wells.

Guinness
2012.01.11, 09:09 AM
i have a Murc SV and i run +1mm on the front with 2* camber and nothing rubs. on the regular non SV Murc i also run +1mm in the front with 3* camber and nothing rubs so i doubt his car is rubbing. i really think your car is struggling b/c you have a pretty fast motor and no other mods

if you look at all the other cars at the track at MC3, all the regulars have their cars heavly modded. the track here is pretty high speed and a stock car with that much power won't really handle that good

BlackBerry
2012.01.11, 05:12 PM
it is a good possibility that your main problem was that the tire was ballooning while diffing out!
:D

This makes a lot of sense, everyone has been telling me to glue/tape my tires. I just never considered the "ballooning" effect. First thing I'll do next time at the track is test the car with the exact same setup (stock) and just have the tires taped/glued. The results should be interesting.

Your tire choice is good for front though so try a mzw17-20 on the rear.

Your motor may also cause the car to slow down off throttle faster than normal. This loads up the front end and causes a rear biased breaking affect. Try breaking in your motor and running a higher gearing.

Kris

I'll try those tires in the rear if taping doesn't help (though I have a feelign it will make all the difference), they came with the MR-03 stock so it's not going to cost me anything.

I never considered how the neo magnets would cause the car to slow much faster, this makes a lot of sense as to why the car might have been handling the way it was. How would a higher gearing effect it?


if you look at all the other cars at the track at MC3, all the regulars have their cars heavly modded. the track here is pretty high speed and a stock car with that much power won't really handle that good

I understand it won't handle that good stock, but you should have been there to see it. It really could barely take one corner.

BlackBerry

Guinness
2012.01.11, 06:43 PM
I understand it won't handle that good stock, but you should have been there to see it. It really could barely take one corner.

BlackBerry

i was there. i was the one who lent u a set of batteries lol

BlackBerry
2012.01.11, 06:49 PM
i was there. i was the one who lent u a set of batteries lol

lol. Thanks btw, saved my day.

Atomic-USA
2012.01.11, 07:27 PM
How old and what's the condition of the RCP track?

RCP grip is dependent on how the track was treated in the past.

twinkie
2012.01.11, 07:38 PM
with the stock set-up and lambo body... where is the motor positioned?

Sinister_Y
2012.01.11, 08:19 PM
the track is medium grip

byebye
2012.01.11, 11:59 PM
I'm having the same motor issue now with a spare car I'm fooling around with.

I know what needs to be done but I don't Want to spend the cash on it since I already have good running cars.

A higher turn motor and higher gearing along with a good tire combo is the way to go. I think I mentions this before...:-)

Kris

BlackBerry
2012.01.22, 05:56 PM
Update:

Ran the car with a few new mods. I played with spring stiffness, ride height, rear dampening, and rear t plates. Flip, flip, flip. One lap the car would take a corner one way, same corner next lap the car would respond completely different. Car couldn't go down the straight and would do something different on it every lap. Same $hit, different day. Car likes doing acrobatics, I think I got 2 feet of air at one point during the day.

I think I have finally figured out what's wrong with the car (I'm 99% sure its the cause). The problem lies with the rear diff/motor mount. Between the right wheel and the diff assembly there is approximately .75mm of play. The diff shaft itself has approximately 1.5mm of play when installed in the motor mount. All this play would cause the weight to transition from left to right rapidly which would cause the flipping and cornering/straight inconsistency. At least this makes sense in my head right now.

Next week I'm going to return the car completely back to stock (except the PN 50T) and shim the rear.

This new finding requires me to know the following:

-What is the rear track supposed to be?
-What size shims do I use for the diff shaft?

Thanks,

BlackBerry

blt456
2012.01.22, 06:18 PM
I use these shims to space the rear axle: 700502 (part 3 from kenonhobby)

I use one shim between the left hub and bearing, and one between the bearing and the adjusting nut threads. Then, I use the backing of the tire tape (white paper) and put that between the left hub and bearing (then screw down the left hub so it has little to no slop). Another way is to add 1 shim between each bearing and part (mentioned above), but add a second shim between the left hub/bearing. Tighten down the set screw and repeat this a couple of times. Then, take the second shim out and you should have very little play. You should have a hard time fitting a piece of paper between the left hub and bearing (that is how little of play you want for the rear axle).

BlackBerry
2012.01.25, 12:39 AM
Thanks for the detailed directions blt456. Your post also gives me an idea to use the left hub from my mr01 ball diff. I`m using the stock gear diff and I found there is some slop on the inside of the plastic hub.

BlackBerry.