DEX210: On-power understeer, off-power oversteer

[Origineelreclamebord]

Hi everyone,

I'll be racing my DEX210 on sunday at the Model Indoor Oss (MIO) track in the Netherlands. I've put my car on a basic setup for carpet.

I don't really have the time to go training tomorrow, but I don't want to come to the track unprepared. I found a small patch of carpet locally to test the car. I'm happy with the fact the car doesn't grip roll at medium speeds and agressive turn-in, but there are however some things to work on.

For starters, the car has horrible on-power understeer - all front bite just disappears under high throttle rates. The other thing is that the car feels hugely agressive off-power: the rear end is only just hanging in there and is on the verge of sliding.

The two contrasts are a bit of a problem: cancelling one out may well make the other one worse.

This is my setup:



My theories:
1. The increased rear droop is causing the off-power instability.
2. I should try running pins on the front.
3. I need to try 25 or 20 deg. caster.
3. I need to lose the front toe-out.
4. The 24g behind the battery can be removed.
5. Loosening the slipper might help.

The place where I ran the can today will be closed tomorrow. What are your thoughts on the required changes?

[mrspeedy]

Its always difficult to say for sure, but the Dboots up front and not your best friend ... they're way too grabby and could certainly be part of the off power oversteer, Schumacher cut staggers are good and easy on carpet.

.. .. and the on power under steer might be a result of you having to firm up the front trying to stop the off power oversteer ..

Have a look at the Craig Collinson std setup .. I've found it to be a brilliant starting point

[Origineelreclamebord]

Update: I went back with some tools to try out a few things. The resulting setup can be seen below.



The things I tried and kept:
- 25 Deg. caster: Increased steering (but also made the rear end yet slightly looser off-power), more importantly it made the car feel much smoother.
- 3 Deg. anti-squat: Seemed to add a little on-power steering.
- Rear shock more upright (middle top hole): More initial on-power steering, rear end can be kicked out to make a tighter initial turn. Rear however starts gripping again once the car starts rolling, ending up with (nearly) the same on-power understeer in long turns under power.
- Looser slipper: Made the car less edgy, but didn't add steering.
- Reducing rear droop back to kit level: This did a lot! Off-power the car became calm and stable, on-power the car had better steering in general, high throttle was less affected though than medium throttle.
- Longer front link: The car seemed to get slightly more steering in general, but off-power stability was kept.
- Swapping 24g battery stopper from rear to front end: Increase in steering on- and off-power, front end is more planted, the rear end is visibly slightly looser but in a controllable way.
- Front rollcenter, 1mm lower inside ball stud: The car seemed to have slightly more steering and have a smaller turning radius, yet didn't feel more agressive.

Things I tried but reverted:
- Schumacher Minipins, Yellow (4WD front & wide rear): The car became quite vicious with the car sliding out off-power. On-power steering was good for medium throttle, but understeer came back at high throttle levels. I reverted back to the dBoots setup (as I didn't have cut staggers with me).
- Rear rollcenter, 2mm higher inside ball stud: The car became slightly looser at the rear, helping steering, but I reverted this because I'm afraid the rear end may become loose on the low grip (PVC and Wood) sections of the track.

This is as much as I could have tested on a patch of carpet that was about only 4x8 metres The rest I'll probably have to find out on Sunday. The car feels better already: The off-power oversteer is not there anymore unless you decide to brake into the corner The on-power understeer is still there at higher speeds but is now manageable.

So despite the steps, I bet there's further improvements to make. If anyone has suggestions what could further reduce on-power understeer, your suggestions are more than welcome!

[Origineelreclamebord]

PS: I didn't see your post mrspeedy (I was busy typing) I know the dBoots Blockpass are not the most beloved tire - at the EOS last year, people either used those on 4WD rims and put glue on the outer sidewall of the tire to make the tire calmer (like I did) or used 2WD front nanobytes glued on 4WD rims and cut off the inside and outside 2 rows.

It's a shame I forgot to take cut staggers with me, those combined with minipins on the rear is probably the way to go - I'll find that out on Sunday

[Chris Doughty]

Looks like you have too much rear toe-in and also your shorty pack too far back.

the shorty pack position changing the way the car behaves A LOT!
the further backwards you get the more turn-in and rotation you get in the corner. and the car squares up really well on power (no on-power steering)
the further forwards you go the less initial steering and more on-power steering you get.
Oh, just noticed your ESC is in front... I'm not a fan of this location for the ESC because it limits battery placement.
I have found that battery placement and weight distribution is HUGE, especially when it comes to on power steering and turn-in

Gear diff will also help here too.

[Cody227]

you are experiencing a basic problem.in the design of mm buggies: too much weight transfer. for.some it fits the driving style ver well and for some it doesnt. try using only one idler gear but you will have to change your setup dramatically or else you will have way too much steering in all situations.

[Origineelreclamebord]

Thanks for the comments guys, I really appreciate your help! This will be my first time with the 210 on a track with this much grip. Usually I drive on my DEX210 on dusty clay, sand and medium bite astroturf - that's why the battery is completely in the back. That, and my ESC is so big it doesn't fit anywhere else!

I have an idea though: I could make a lexan sheet with the length of a stick pack. On that I could fit the ESC and a battery stopper. I can then swap this around so the battery is either fitted at the front or the back.

Would this be too extreme a change in weight balance (In other words, am I better off chucking some weight under the servo?) or is it worth a shot?

[mrspeedy]

Actually your weight distribution is exactly how I run mine at the mo, and the car feels great like this. Its just a question of changing the rest of the car to suit your weight distribution

Try a little less front droop .. it has a real nice feel with this layout ...

[Gregerl]

Originally Posted by Origineelreclamebord

Thanks for the comments guys, I really appreciate your help! This will be my first time with the 210 on a track with this much grip. Usually I drive on my DEX210 on dusty clay, sand and medium bite astroturf - that's why the battery is completely in the back. That, and my ESC is so big it doesn't fit anywhere else!

I have an idea though: I could make a lexan sheet with the length of a stick pack. On that I could fit the ESC and a battery stopper. I can then swap this around so the battery is either fitted at the front or the back.

Would this be too extreme a change in weight balance (In other words, am I better off chucking some weight under the servo?) or is it worth a shot?

I also noticed that you don't run any weight up front at all. We mainly race on carpet with slicks, so it might be a different story, but we always have 24g under the servo, 20g on the servo and 5g in the bulkhead. Found that this helps a lot. If you look at how Joern is running the 210 he has a 64g front bulkhead and then some weight on top of the servo when running on carpet. Personally I think that is too much, at least for us mere mortals....
This is also with a full stick pack.
The only time I have gotten this car to work well with a shorty has been with the 64g bulkhead and the shorty in the back, at least on carpet.

[Paultje040]

Im curious what make and type Slicks you run?

I'm also racing this Sunday on MIO.

My setup is almost the same as yours Paul. I run 3 deg. rear toe in. More makes the car to twitchy for my liking.

I do have the 64 gram bulkhead, haven't tested it yet. I do run a 8-racing shocktower with the 26 gram camber mount (KLIK
That does help the on power grip.

At first didn't notice your 6.5 motor. I run an 8.5 @ MIO. tested a 7.5 wich will work but be a hand full.
I think your 6.5 motor is to blame for the lack of steering on power

[Gregerl]

We race on VBC slicks with additive. It is a one type tire used for the Swedish VBC cup.

[Paultje040]

Originally Posted by Gregerl

We race on VBC slicks with additive. It is a one type tire used for the Swedish VBC cup.

Would that tire work without the additive as we are not allowed to use any on the track?

[Gregerl]

Originally Posted by Paultje040

Would that tire work without the additive as we are not allowed to use any on the track?

Depends a lot on your surface. In general I would say no, I would also say that the rear tire is probably easier to use without additive as it is easier to get heat into it than the front. The few times I have tried without additive, steering has been lacking alot.

[Lee24h]

This is what foward motor cars get rid off

[Paultje040]

Originally Posted by Gregerl

Depends a lot on your surface. In general I would say no, I would also say that the rear tire is probably easier to use without additive as it is easier to get heat into it than the front. The few times I have tried without additive, steering has been lacking alot.

Thank you.

[Dino_D]

Originally Posted by Cody227

you are experiencing a basic problem.in the design of mm buggies: too much weight transfer. for.some it fits the driving style ver well and for some it doesnt. try using only one idler gear but you will have to change your setup dramatically or else you will have way too much steering in all situations.

Try thickening the rear oil weight. It seems too light. If the front is heavy at 500cst (37.5wt), and the back is 250cst (20wt) what happens is the front doesn't lean or roll and develops a push, while the back leans too much thus the imbalance will cause the car to hook or spin mid corner, or a handful to drive out of the corner. Normally you need to try to ensure the roll rate of the front and rear is close otherwise you will have a ill handling car.. Or unless you got a point and shoot track. straight 180 turn, straight. 90 turn, etc..


Try 30wt approx 400cst front and 27wt approx 350cst rear. Using 1.5x3 holes front and rear. Its a good starting point for a med bite carpet setup.

Also battery placement. The more rearwards you put the weight, the more the car wants to rotate and swing in a corner. Moving it more forward, stops the rotation.

[dex210Nick]

So what did you end up with?

It does sound like a weight transfer problem. The car wants to squat too much on-power and release it all of a sudden off-power causing oversteer. I had the same problem on carpet a few weeks ago. I solved the problem with a softer front spring. I could have used a stiffer rear, as well.

MM3 also tends to work better on carpet. You don't need the rearward weight shift of MM4 to get traction and it makes the car more neutral to drive.

[Origineelreclamebord]

Thanks for the suggestions everyone!

The updated setup before the race is already posted. At the trackside I changed a couple of things:

- Tires: dBoots Blockpass (A)/Nanobyte (A) was replaced for Schumacher Low Cut Stagger (Yellow)/Schumacher Minipin (Yellow).

The dBoots front tires didn't seem to work for me, and the rears were starting to get too worn. The Schumachers provided more (and sharper) steering and the rear grip was much better too because it had more tread left.

- Shock Geometry: Rear shock upper hole moved from 2 (Center) to 3 (Inside).

The car still had a loose rear end on the plastic/vinyl sections of the track. My theory was that it was down to a lack of rear roll at low speeds. The change to a more progressive shock made the rear end more planted and the oversteer wasn't snappy anymore (you could feel it coming and correct for it a lot easier). It also increased on-power understeer on the carpet a tiny bit, but I recall the combination of new tires and shock geometry made the car about 20 seconds faster - that's nearly a full lap

- Shock Oil: Front shock oil from #500 to #450.

At the track someone pointed out my car had a bit sluggish front damping compared to the rear, so I changed this between the first and second finals. The result was more steering on- and off-power, and by this point the contrast between on- and off-power steering is very decent.

An important note to add is that in the last final, the rear tires were starting to go and thus the final before the rear tires may already have been over their performance peak. It may understeer more again with newer rear tires, but for this a 2mm shims (instead of 1mm) under the inside front ball stud should help - at least for me it did on other tracks.

I will continue to work on the car as I'm sure the car can improve further, but so far, so good! The advice has helped a lot and I'll definitely try the suggestions with the next opportunity I get!