Jump to content
glancyguy

Df-03 Ms Oversteer

Recommended Posts

Hello,

My DF-03 MS has some serious oversteer on pavement. It is to the point that I have to lay completely off the throttle and turn the wheel half way on radio or else the buggy spins out. It also spins out still on full acceleration (I changed the center-one way as TA_Mark suggested and that cured 80% of the problem).

Here are the stats on the car:

1) 19T Motor

2) Proline DirtHawg tires (not the best for pavement)

3) 46oo mah NiMh battery

The only thing I have done so far is adjust the front tires to a neutral toe. This hasn't helped much.

Oversteer Top

Oversteer Rear

Oversteer Rear 2

Here are my questions:

1) What kind of impact do the tires have on the problem?

2) How do I fix the toe in on the rear of the buggy?

3) Do I need to adjust the ball diffs to help correct the problem?

Share this post


Link to post
Share on other sites

Well, I'd take a look at your diffs first. Are they equally tight? If they're not, make sure they are and try again.

If that won't cure it I'd tighten the front diff slightly more than the rear (or make the rear slightly looser than the front). You could also make the front suspension slightlyharder (or the rear softer), but this probably will mainly be felt offroad, not on the pavement. As a last option you could make a front stabilizer bar (unfortunately they are not for sale for the DF03).

As for the toe, the toe in should actually make the car more stable and make it less likely to oversteer as well.

Share this post


Link to post
Share on other sites

My DF-03 has serious toe-in on the rear as well, I don't get why. It made the handling on my Manta Ray all twitchy when I set it up like that, so I went back to standard.

Share this post


Link to post
Share on other sites
My DF-03 has serious toe-in on the rear as well, I don't get why. It made the handling on my Manta Ray all twitchy when I set it up like that, so I went back to standard.

Three questions from both posts:

1) I do remember making the rear diff much tighter than the front. What is the easiest way to adjust them? It was hard enough when the gear box was in my hands, much less mounted on a chassis?

2) Herebemonsters, what do you mean when you say you switched to "Standard"?

3) I am assuming that the largest impact on oversteer is ball diffs, followed by toe, followed by decent tires. No camber?

Thanks,

Darren

Share this post


Link to post
Share on other sites
2) Herebemonsters, what do you mean when you say you switched to "Standard"?

Sorry, I got the toe-in by replacing the rear shock mount with the FRP part from a Top Force. Went back to a standard shock mount to correct it.

Share this post


Link to post
Share on other sites

Toe in is used to make the handling more stable, on both front and rear of the chassis. Front toe in will make make it more stable and dull the steering response. Rear toe in gives you less steering, better straight line stability and better traction, as under power the wheels pointing in means the power is directed inwards. Zero toe in will make it unstable as the power isn't directed up the middle of the chassis. There's also the problem that with zero toe in any slight play in the suspension means the geometry moves from toe in to toe out, meaning the rear end will steer in any direction when it hits any bump.

Diffs. Generally the tighten the diff the less traction and grip you have. Running the rear diff stiffer than the front will make it very responsive, giving you more steering. A stiffer front diff will give you less turn in to a corner, more traction to help pull it out of the corner. Competition touring cars use a solid spool in the front to make them stable under braking and be more stable putting the power down out of the corner.

To sort the handling by changing the suspension.

I'm assuming you are using the kit springs and shock oil.

Firstly wind those spring collars up to get the wishbones level front and rear. The angle of the wishbones is way too high for off road handling, never mind on road. The rear geometry is so high that when you slow down for a turn the rear end is going to dump all the chassis weight on the front end, causing it to dig in to the corner. The driveshaft angle will also help unload the rear suspension under braking.

Move the upper link to the bottom hole on the shock mount. It's current location makes the links parallel to the wishbones which gives a very high roll centre, which reduces the amount of rear grip. Dropping the location to the bottom position, and adjusting the links to put the camber back to the same amount, will lower the roll centre, allowing the rear end to roll more and generate more grip.

The simplest and most obvious way of fixing the oversteering is to throw away the one way. A one way works by disengaging the front wheels from the transmission whenever you let off the throttle. This gives you tons of front end grip as the front wheels just steer in corners, giving you loads of turn in which is what you want on a racetrack. The standard DF03 has no one way as that's a much better setup when you aren't running on a prepared surface with grippy tyres.

Nothing gives you way more steering than fitting a one way in there and the easiest way to make a buggy more stable is to remove it.

Share this post


Link to post
Share on other sites
Sorry, I got the toe-in by replacing the rear shock mount with the FRP part from a Top Force. Went back to a standard shock mount to correct it.
Changing the shock mount makes no difference to the toe in. Toe in is the angle of the wheel when looking from above.

toe.jpg

Camber is the angle of the wheel when looking from behind

camber.jpg

I assume when you fitted the shock mount you didn't replace the fixed upper links with adjustable ones so you could adjust the camber back to 2-3 degrees negative to get the geometry correct.

Share this post


Link to post
Share on other sites

Yep, I know what toe-in is, and changing the rear shock mount made the wheels point inward. Seriously. It was so severe it was actually causing adverse tyre wear, so I had to revert until I could find adjustable arms for the rest of the suspension.

Share this post


Link to post
Share on other sites

Hello,

Sorry I am late in my response. I dropped all of the suspension and softened the springs. All of the shafts were parallel. It definitely helped with the oversteer, but did not cure it. I then went and tightened the front ball diffs and lessened the toe-in (almost neutral). There are two newer issues I am now dealing with. I get the kind of steer I want at full acceleration. If I let off in the middle of a turn, I now spin out. This now sounds like understeer? Yes?

Also, is removing the one way simply replacing the bearing?

The other issue I still can't figure out is this:

At straight line full throttle, the steering twitches and sometimes pulls sharp to the right. If I let off the throttle in a straight line, the buggy completely spins out to the right (and has smashed a curve a couple times). I assume this is some play in the suspension and I don't have my toe set correctly.

Honestly mates, this is starting to get discouraging and I think I may have bought something too advanced. My DF-02 is much easier to handle than this.

Share this post


Link to post
Share on other sites
Hello,

Sorry I am late in my response. I dropped all of the suspension and softened the springs. All of the shafts were parallel. It definitely helped with the oversteer, but did not cure it. I then went and tightened the front ball diffs and lessened the toe-in (almost neutral). There are two newer issues I am now dealing with. I get the kind of steer I want at full acceleration. If I let off in the middle of a turn, I now spin out. This now sounds like understeer? Yes?

Also, is removing the one way simply replacing the bearing?

The other issue I still can't figure out is this:

At straight line full throttle, the steering twitches and sometimes pulls sharp to the right. If I let off the throttle in a straight line, the buggy completely spins out to the right (and has smashed a curve a couple times). I assume this is some play in the suspension and I don't have my toe set correctly.

Honestly mates, this is starting to get discouraging and I think I may have bought something too advanced. My DF-02 is much easier to handle than this.

The steering problem sounds to me like there's interference - I have a DF03 myself and I can't imagine that the play would be so big that it would suddenly just turn right sharply...

And don't be discouraged! It's a great car and I managed to get mine running without any flaws (except I had my diff way too loose on the first luckily very short test run). I was neither used to anything as advanced; the only ball diff I had is one I threw out of my car when I got it (a TA02) and the best build quality car I had until I got my DF03 was probably my TB01 with LA arms set... :blink: Once you get it running the way you want you'll be very happy you kept it :lol:

Share this post


Link to post
Share on other sites

The odd steering sounds very much like a servo glitch caused by interference. Try a different frequency, check the antenna wire is no where near battery or esc wires, do not coil the extra antenna wire, make sure it's touching nothing metal or CF on the chassis.

There is nothing that can cause that much slop in a DF-03 suspension, they are quite tight with very little 'wobble' unlike the DF02 which the lower arms flop around everywhere.

Removing the one-way is a matter of replacing the shaft with a standard one or with the hopup one-piece alloy cup. The correct bevel gear is included in the MS kit but not the correct shaft. (compare the MS manual to the base DF03 to see the differences).

Lifting the trigger mid corner is a driver mistake issue, not the car nor oversteer/understeer. Think of it like lifting your foot in a 1:1 manual RWD car, you get a compression lock up and the rear drifts wide (hand brake style turn using the engine compression to brake). When you lift off with the one-way fitted you only have RWD braking the chassis. It's all car balance... when you lift the throttle the weight shifts to the front wheels unloading the rear (and the inside rear the most) combine this with the 2WD tendencies off throttle of the one-way and it causes a spinout. How do you stop this? Don't lift off throttle hard mid corner, adjust your driving, keep a constant pressure on the throttle through the corner until your acceleration point. It's the same the other way when you slam on the throttle, weight shifts to the rear and you have very little steering until the car reaches speed and the weight balance evens out again. On power with the MS you have AWD, off power RWD, it takes some getting used to.

Onroad you want that toe to be neutral, toe-in will make the chassis very 'excited' when on a grippy surface. Toe-out will settle the chassis, but cause more understeer entering a corner.

I thought you knew all this seeing you changed what I wrote and rewrote it, changing the meaning...

Share this post


Link to post
Share on other sites

:blink: Boy oh boy, I'm trying to follow this discussion in the event I'm faced with a steering problem. But I am getting more and more confused the more posts get in. I played around with my Nitro cars on the camber and toe and found that as TA MARK said all changed when I changed my driving style. The factory setup was a great in between for most surfaces and my fidgeting tended to upset the handling to the point where the car was uncontrollable.

Haven't had the pleasure of playing around with a DF03 yet so maybe I should shut up now...... :lol:

Share this post


Link to post
Share on other sites

Thanks for the next round of advice. I am sure there is plenty of user error in all of this as I learn to drive a better class of buggy. :rolleyes: Replacing the one way is my next task. Thanks for allowing me to ask these kinds of questions and your patient responses.

Share this post


Link to post
Share on other sites
I get the kind of steer I want at full acceleration. If I let off in the middle of a turn, I now spin out. This now sounds like understeer? Yes?
As Mark says, the spinning out is driver error not chassis problem. With the one way in there you only have rear wheel braking, letting off mid corner is the same as in a 1:1 car pulling your handbrake in the middle of a corner, both times the back end will come round. With a one way clutch in there you have to learn to brake in a straight line, let it roll into the corner then accelerate out. Removing the one way will let you get away with less driving skill as it will 4 wheel brake mid corner, so tightening up the steering.
At straight line full throttle, the steering twitches and sometimes pulls sharp to the right. If I let off the throttle in a straight line, the buggy completely spins out to the right (and has smashed a curve a couple times).

Sounds like interference to me under acceleration. I assume it's a modern motor with built in capacitors, or you have fitted the ones provided. It can also depend on what ESC and batteries you are using, if the batteries are cheap ones it is possible they can cause a voltage drop under acceleration causing a break in power to the receiver and servo.

The spinning out when letting off the throttle is again the same as handbraking a 1:1 car, it will spin out as you only have rear wheel braking. Move the throttle trim on your radio forwards slightly so at neutral throttle it will keep rolling without braking. You can get it to stop in a straight line, but the suspension geometry, shock length and spring load all have to be absolutely identical on both sides of the chassis.

Share this post


Link to post
Share on other sites

Thanks, this makes complete sense. I fondly remember the days of 1:1 "snow drifting" (pulling the handbrake) in empty car parks after a snow storm. I am going to replace the one way with:

http://www.tamiyausa.com/product/item.php?product-id=53948

Do I need any other pieces or parts here (bearings, clips)? Since I am ordering from Honk Kong (and it takes 2 weeks), I want to make sure I have everything I need.

As for the interference:

Trinity Komodo Dragon 19T stock (pulled from my DF-02)

Dynamite Tazer 15T ESC (Pulled from my LunchBox)

Duratrax 3800 NiMh battery

The only thing I can think of is that the ESC and receiver are too close to each other as I had to pack them pretty tight (the Tazer is much larger then the TEU-101). I am going to try to mount the receiver on the other side of the chassis.

Share this post


Link to post
Share on other sites

My solution to heavy rear weight bias tailhappyness...Some lead weight to balance the chassis 50/50 F/R.

Works well, and added steering is a plus also. (DF03ra/Humvee conversion)

df_002.jpg

post-26024-1234636529.jpg

Share this post


Link to post
Share on other sites

That part set will do the job. The bevel gear you need is in the kit but listed as un-used in the parts list in the rear of the manual. There should be a left over cross pin from the MS build. You can grab the E-clip from the one-way shaft. Bearings are the same. You will need to reference the Base DF-03 (Dark Impact, Keen Hawk, Avante Mk II) manual for assembly instructions of the shaft to make sure you have everything in order.

Share this post


Link to post
Share on other sites

Hello,

I ordered the one piece joint to replace the one way and it finally arrived today. Much to my dismay, the joint requires MR3 bearings while the one-way uses MK11. So, unless I am truly missing something here, I do indeed need some new bearings. There are no leftover MR3 bearings in the kit. Does anyone happen to know the official size of these so I can pickup some Duratrax replacements? I believe they are 5x10. I would like to pick them up at my LHS instead of having to wait another week.

http://www3.towerhobbies.com/cgi-bin/wti00...=LXD115&P=V

Thanks,

Darren

Share this post


Link to post
Share on other sites

There is indeed a difference in shaft diameter. The one-way shaft is 6mm, the standard or one-piece shaft is 5mm. Both fit into a 10mm seat. The correct size is a single 1050 bearing (page 5 of Dark Impact manual), and the size is printed there in the manual. 1050 is a common size. the two 1060's from the one-way are not. Nitro clutch bearings are usually 1050's and sold in pairs.

Share this post


Link to post
Share on other sites

Received 1050 bearings and put in the cup joint. It definitely makes a difference in cornering and reduces the ammount of steer. I am finding out that my driving style is leaning towards more understeer than over. The spikes also perform a little better on the pavement. I noticed that with the tires and removal of the one way that the car can do some drifting while cornering. It is kinda fun and something I don't have on any other buggy. Don't they make a DF-03 drift version or something?

I also noticed (maybe not related) that the interference starts to happen halfway through my NiMh packs. The only difference in this buggy as opposed to the others is that I have a high torque Futaba servo in there. Could be unrelated I guess. Would there be steering interference when the pack starts to get low on juice?

Thanks,

Darren

Share this post


Link to post
Share on other sites
It definitely makes a difference in cornering and reduces the ammount of steer. I am finding out that my driving style is leaning towards more understeer than over.

One-way doesn't suit many drivers, takes some getting used to. I'm the only one local running one, the other guys didn't like the feel it gave to the chassis. The chassis is faster with it, just much harder to drive and less forgiving to bad throttle inputs.

Don't they make a DF-03 drift version or something?

Throw some tourer size drift wheels on it (be careful of the 'braces' on the rim inside, DF-03 rubs on some rims), or glue some 2.2"/2.0" poly pipe to another set of rims and go have some fun. One of the guys here runs his DI with 2" poly on tourer rims when we run the onroad drifters (he doesn't have a tourer).

I also noticed (maybe not related) that the interference starts to happen halfway through my NiMh packs. The only difference in this buggy as opposed to the others is that I have a high torque Futaba servo in there. Could be unrelated I guess. Would there be steering interference when the pack starts to get low on juice?

Quoting Terry: Sounds like interference to me under acceleration. I assume it's a modern motor with built in capacitors, or you have fitted the ones provided. It can also depend on what ESC and batteries you are using, if the batteries are cheap ones it is possible they can cause a voltage drop under acceleration causing a break in power to the receiver and servo.

Same affect as this is a poor battery connector. Though, for me these 2 usually cause slow servo motion. Stuttering servo is sometimes the plug at the reviever with poor connection as well, cut/crimped/broken servo wire even. Try a different servo.

Share this post


Link to post
Share on other sites

Thanks Mark,

I did miss terry's comments earlier in the thread, my apologies - in the IT world, we call that RTFM. :lol:

The full rig is:

Tower Hobbies radio and receiver

Futaba S3010 High Torque Servo

Trinity Komodo Dragon 19T spec motor

Dynamite Tazer 15T ESC

Duratrax NiMh 4600 - DTXC2149

I used this motor, radio, ESC, and pack in my DF-02 with absolutely no issues. The only thing that changed is that my DF-03 has the Futaba high torque servo. I am aware that these are not the best components, but I also don't want to drop $400 to have to upgrade it all given cash flow and the economy. Outside of the servo, which one of these should I consider changing?

Thanks as always.

Share this post


Link to post
Share on other sites
Yep, I know what toe-in is, and changing the rear shock mount made the wheels point inward. Seriously. It was so severe it was actually causing adverse tyre wear, so I had to revert until I could find adjustable arms for the rest of the suspension.

This isn't even possible unless your lower A-arm pivot (where the A-arm connects to the gearbox) is severely cracked or split open. I think you're mixing up toe-in and camber... You mean that the top of the wheel points inward? That's negative camber.

Share this post


Link to post
Share on other sites
Thanks Mark,

I did miss terry's comments earlier in the thread, my apologies - in the IT world, we call that RTFM. :P

The full rig is:

Tower Hobbies radio and receiver

Futaba S3010 High Torque Servo

Trinity Komodo Dragon 19T spec motor

Dynamite Tazer 15T ESC

Duratrax NiMh 4600 - DTXC2149

I used this motor, radio, ESC, and pack in my DF-02 with absolutely no issues. The only thing that changed is that my DF-03 has the Futaba high torque servo. I am aware that these are not the best components, but I also don't want to drop $400 to have to upgrade it all given cash flow and the economy. Outside of the servo, which one of these should I consider changing?

Thanks as always.

Are your ESC and reciever near the battery or motor wires, or close to each other? You might want to play around with the components' location to see if it makes any difference.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...