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View Full Version : MR-03 RM cornering issues/setup questions


Deca
2011.02.16, 04:19 PM
OK SO, my Mini-Z experience has been going pretty well. I've been steadily improving my car, consistently spending money at each race on new parts...I even have 2 cars now! However, my MR-03 isn't cooperating with me lately.

I'll start off by listing what my setup currently consists of:

Arta NSX
Bearings
PN 64p Ball Diff
PN Motor Mount
70t PN Motor
PN DPS with Atomic RM adapter
PN front springs (softest/red)
PN....I'm not sure what rears (probably something I should figure out)
Kyosho 30 degree front slicks

Now, up until my last race I was running some mysterious front tires that a fellow member of our local crew gave me at our first race. They were Atomics with an X tread pattern, and are apparently no longer in production. After adding the DPS, running these tires, the setup was fantastic. No over or understeer issues and the car was always right where I wanted it to be.

However, those tires have been completely worn out and I needed to figure out what to go to next...I started with PN 8 degree slicks and after some experimentation and help from another club member, ended up with the Kyosho 30s...but it's still not handling as well as I know it's capable of.

My turn in is excellent, but as soon as it hooks up in a corner it understeers. I spent a fair amount of time setting up the LSD as well as I could, and managed to reduce the understeer, but it's still present. This is not a behavior the car exhibited before, and is pretty frustrating as it doesn't seem like just the tires should have been able to change the handling in this manner.

I was thinking it may help to tighten up the rear end with a stiffer T-plate (running stock currently) to try and keep the weight from shifting off of the front wheels quite so much. I also wonder if some front negative camber might be the solution I'm looking for here...I'm just kind of uneasy about changing the setup so significantly when it was running so well with those tires...but I can't seem to find any tires that reproduce the handling my car previously exhibited.

I'd really appreciate any thoughts or suggestions (that don't involve switching to an MM), hoping to get this straightened out Friday.

Traveler
2011.02.16, 05:11 PM
it doesn't seem like just the tires should have been able to change the handling in this manner.

Ummm! Think again! :) Doesn't seem like it should, but it does.

Not only does the brand, type and softness matter, but so does the outer diameter of the tire/rim. Before changing your entire setup, I'd recommend truing the front tires down and seeing if that helps!

Deca
2011.02.16, 05:14 PM
Well I understand that the tires are going to have a huge impact on handling, it just seems weird to develop understeer mid corner but preserve turn-in from ONLY a change in tires. If the tires alone were causing the understeer I'd expect turn in to be weaker.

What exactly do you mean by truing?

geeunit1014
2011.02.16, 06:39 PM
Well I understand that the tires are going to have a huge impact on handling, it just seems weird to develop understeer mid corner but preserve turn-in from ONLY a change in tires. If the tires alone were causing the understeer I'd expect turn in to be weaker.

What exactly do you mean by truing?


Not only can the "shore" (harndess) of a tire differ, but the "compound" (material its made of) differ as well, so you can achieve many many different feels and characteristics in a tires just by changing those. On top of that, you say the last tires you had were treaded pattern (not sure how far they had worn down), if you go from a treaded tire to a slick thats a whole new ball game on top of that. 90% (at least) of a good setup is tires. You can gain a tenth or 2 by making a good chassis adjustment, but you can gain 3-5 tenths, if not more, by getting better tires.

From what I have seen on RCP in my experience so far is that treaded tires grip better than slicks, which may be why the car pushes mid corner for you (the tire has no tread to grip the rough rcp). It may be as simple as going to a kyosho radial 30 front for you.

Truing is changing the diameter of the tire. By changing the diameter, you change how much sidewall the tire has, which is another adjustment you can make. It may be good for you to true your Kyosho slicks just a tad, as the tire is slightly rounded out of the package, so you if you true it to be flat, you can gain some contact patch and get some more grip.

color01
2011.02.16, 07:42 PM
Do you have any camber in the front?? 0 camber makes the car turn in well no matter what you do, but as soon as the front end rolls, the tire contact patch is gone and it's all understeer from there on out. :confused: What's worse, the PN MR03 Red springs are still fairly stiff and you're not going to get the chassis to roll enough to actually give you any camber. This is one possibility.

The other possibility, which I'm almost sure is happening, is that your car is an RM, which means there's not enough weight over the front tires to maintain front grip after the initial turn-in "swing", which is caused by the rear end. So no matter what you do, the rear end will swing out beautifully upon turn in for you, but the front tire choice is critical in maintaining front grip through the exit.

I would say that if you want to stick with the PN Red springs, go back to the PN 8 slick fronts and true them down to 23-24mm, that will really break them in and you should start to oversteer, if anything. The PN 8's have a LOT of grip, making my car almost undriveable, so I don't see why it wouldn't eliminate your understeer issues once and for all.

Otherwise, use your Kyosho 30's or 30 radials, and move to a softer front spring. Most other racers I know on the stock front end are using the "super-soft" spring kits from various manufacturers, I myself go with PN Oranges (the absolute softest). Most spring kits are geared towards MM chassis weight distributions, so with an RM you really have to go softer in the front.

Deca
2011.02.16, 07:49 PM
The kyosho 30s are broken in, they're a used set but still have plenty of life in them.

Based on my original intuition combined with what I'm reading here, camber might be my best bet, since I have turn in but understeer after the weight transfers..I am running 0 right now. 2 degrees seems like too much, maybe 1 or 1.5? What would you guys suggest...don't really want to just take a blind shot in the dark with alloy knuckles, a bit pricier than tires :p

EMU
2011.02.16, 08:08 PM
As far as I know, Atomic has not discontinued their AW tread X-pattern tires. I just received 10d - 40d front AW Groove tires yesterday... Just find out from the donor what the hardness was, and order a set.

I personally prefer a slick tire in the front, as I feel that I can feel the car a little better... Treaded tires grab a little too much initially, and for me create more chatter. Also the tire changes its handling much more over the life of the tire (as the tread wears).

As for camber, I like 1d for MR03, and 1.5-2d for MR02. I also only use 0mm offset front wheels.

chad508
2011.02.16, 08:34 PM
get the reflex upper tower bar. it will give you all the camber adjustments you would want.

geeunit1014
2011.02.16, 08:34 PM
The kyosho 30s are broken in, they're a used set but still have plenty of life in them.

Based on my original intuition combined with what I'm reading here, camber might be my best bet, since I have turn in but understeer after the weight transfers..I am running 0 right now. 2 degrees seems like too much, maybe 1 or 1.5? What would you guys suggest...don't really want to just take a blind shot in the dark with alloy knuckles, a bit pricier than tires :p

1* of camber is a pretty big change. Ive never liked running past 2*, more and the car drives funny, hooks, etc. If you feel like you want to play with camber a lot, it may be worth it for you to get a front end setup that will let you adjust camber in the tower bar, instead of the knuckles.

Deca
2011.02.17, 01:36 AM
If you feel like you want to play with camber a lot, it may be worth it for you to get a front end setup that will let you adjust camber in the tower bar, instead of the knuckles.

What exactly would that involve? I'd been wondering about it but don't totally understand what sort of setup allows for caster and camber adjustments. I was also planning to get that new R246 front damper system whenever it's available, would that interfere with such a setup in any way?

geeunit1014
2011.02.17, 02:04 AM
What exactly would that involve? I'd been wondering about it but don't totally understand what sort of setup allows for caster and camber adjustments. I was also planning to get that new R246 front damper system whenever it's available, would that interfere with such a setup in any way?

If your running the stock front end now, you can get the reflex tower bar (http://www.reflexracing.net/proddetail.asp?prod=RX1159) and get camber and caster adjustments. The bar is offset a bit and can turn around 180* for 2 or 4* caster, and obviously the arm mounts slide for camber. The key has preset camber positions for 0-3*, so you line the arms up with the hingepins in the key, and set the camber that way. Im not terribly familiar with PN or Atomic parts, but im sure they should have similar options

Not sure on the new R246 bit, it may still work (from the pic it looks like it could), but to be certain someone will have to mount one up ;)

Deca
2011.02.17, 09:36 AM
If your running the stock front end now, you can get the reflex tower bar (http://www.reflexracing.net/proddetail.asp?prod=RX1159) and get camber and caster adjustments. The bar is offset a bit and can turn around 180* for 2 or 4* caster, and obviously the arm mounts slide for camber. The key has preset camber positions for 0-3*, so you line the arms up with the hingepins in the key, and set the camber that way. Im not terribly familiar with PN or Atomic parts, but im sure they should have similar options

Not sure on the new R246 bit, it may still work (from the pic it looks like it could), but to be certain someone will have to mount one up ;)

Thank you for the info, I'll definitely be looking into this :)

I was thinking about the R246 front end this morning and something occurred to me...someone mentioned RM setups often needing a softer spring rate than an MM would need, and most spring kits are targeted towards MM setups...really hoping I'll be able to get that front end working but a little concerned now. Ah well it's not even available in the US yet, so I'll deal with that as I come to it.

iruninsoga
2011.02.19, 01:16 AM
The R246 setup comes with its own upper mount as the upper mounting point of the arms is different from the stock arms.

I suppose it might be possible to mount a different company's upper mount but the geometry will be all messed up. The roll bar might also be affected too.


*Just measured it, the R246 upper mounting point is 1mm higher than stock. You might be able to shim an third party's adjustable mount to make it usable.

color01
2011.02.19, 06:24 AM
That would be me, Deca -- because the RM weight distribution is farther back, you ideally want to go to a softer front spring and stiffer T-plate to maintain a balanced loading over the four wheels. If you have no softer spring choices in the front then you're probably going to push again, at which point you'll need to do something else (groove your front tires, for example).

mini-z
2011.02.20, 03:01 PM
Thank you for the info, I'll definitely be looking into this :)

Well, Deca did end up picking up the Reflex Racing Adjustable Upper Suspension Mount and I'll let him expound on the details but it seemed to be working really well on at the Dojo race on Friday! :)

Deca
2011.02.21, 12:13 AM
Yes! I did grab the Reflex tower bar and it's excellent! My initial guess on camber ended up being wrong, so it was a money saver as well. Running 2 degrees now, tire wear evened out nicely in a single night of racing and handling has improved.

Great part, I highly recommend it. The setting key works brilliantly and the quality of the part is top notch. Goes on super easy and holds settings nice and firmly.

geeunit1014
2011.02.21, 01:30 AM
Glad you like it! You can also fine tune your roll center/camber gain by putting shims under the tower bar (raises the inner pivot point). Good fine tuning adustment if you need to take away just a tad of steering in the middle of the corner ;)