What is wrong with you DT-03?! Suspension setup

[skom25 645]

Hi,

I have some kind of general issue with suspension setup of my DT-03. I run mainly on surface as on photos/ movie.

As you can see, there is no rear grip at all. Car slides like on ice. It starts to slide somewhere on the middle of curve. To not slide, I have to go at max 40/50% of constant throttle. When I decrease throttle it just loose grip. Every fast change of direction ends the same: rear just loose all grip. To gain some grip I have to go crazy fast because rear just push front wheels and rear cannot slide.

I run this course many times in the past. I even could go for about 20 minutes without major mistakes. Now, I am not able to do single lap. In meantime I rebuild model and change settings but I do not remember how it was previously. Definitely it was much lower and suspension was harder but I do not think it is root cause. I had also Neo Fighter tires on front.

I know that rear tires are little worn but previously I ran with almost bald tires and I did not have such huge issue.

What do you think? I really do not have idea what is wrong. I tried to change suspension angles but it is even worse.

[Twinfan 765]

IMHO, you're running on a smooth surface which will always be hard to get grip on - especially if it's not been warmed up by the sun.  I would not be expecting great levels of grip with a light 2WD car and those tyres as the tread pattern is providing a minimal contact patch.

Maybe you need slicks?

[skom25 645]

I agree but as I wrote, I did not have such huge issue in the past. It is also quite strange, because I does not loose grip gradually. It is just sudden lack of grip and car starts to rotate.

[Wooders28 4563]

I'd start with tyres first, I've found the Schumacher blocks to be a decent all rounder (they're a 2" tyre, but do fit a 2.2" wheel..) Yellow compound for grip , blue compound for longevity.

Shock wise, I tend to run 50cst lighter oil in the rear.

I wouldn't expect alot of neg camber, can't imagine there's enough grip, to roll the tyre or chassis.

[sosidge 618]

You seem to have done a lot of changes to the suspension and you're running 4wd tyres.

Here's the thing about basic Tamiyas. Tamiya's engineers know what they are doing with the out of the box setup. Unless you really know what you are doing, you will struggle to make the car better.

Also, 2wd buggy on paving blocks is simply not the surface that they are designed for. And you will struggle to find tyres that are intended for it.

I'd rebuild it back to kit settings and get rid of those 4wd tyres.

[skom25 645]

I still have 2WD front tires, so maybe I will try them. I can use current on TT-02B.

[Pylon80 1393]

If I were running a DT-03 on pavement I would be very tempted to experiment with F1 tires and wheels like the F104 tires. I think the front would fit as it (but with slightly different bearings) while the rear would need some sort of 12mm to 14mm 3D printed hex adapters. Obviously not exactly straight forward nor cheap, but I am pretty sure it has been done before. The F104 tires have really good grip and the rears are nice and wide.

[Kowalski86 2181]

A part of that is your tires, and another part of that is because most 2wd buggies are rear-heavy, much like a Porsche 911 you need to figure out how to manage the weight in the back to keep them from spinning out.

 

[skom25 645]

14 hours ago, sosidge said:

You seem to have done a lot of changes to the suspension and you're running 4wd tyres.

Here's the thing about basic Tamiyas. Tamiya's engineers know what they are doing with the out of the box setup. Unless you really know what you are doing, you will struggle to make the car better.

Also, 2wd buggy on paving blocks is simply not the surface that they are designed for. And you will struggle to find tyres that are intended for it.

I'd rebuild it back to kit settings and get rid of those 4wd tyres.

To be honest, I did not make any changes which are not "allowed" in DT-03 by designers. Only change is 4WD tires on front, which I will change them for 2WD.

[one_hit 1011]

Here’s what I think is wrong. You tuned your suspension while it had the narrow 2WD tires. You were able to get it to handle to your liking. You then changed the front tires to 4WD tires which are wider and therefore grippier, which added steering and is now causing you to oversteer. 
 

I would reset all your adjustments to stock as stated un the manual, and see how it drives. You can also change to the firmer blue springs up front and see how that feels. Maybe dial down the steering dual rate a bit. If all else fails, you can always go back to the stock 2WD tires. 

[skom25 645]

That is the plan. I will go to stock settings and probably set suspension as low as possible. I had plan to go Off Road but because I do not have any place to run, it does not make sense to have around 3 cm of ride height, to run on smooth pavement.

[skom25 645]

I returned to more or less setup which was nice, at least I think it was.

I installed 2WD front tires with inserts. Rear tires stayed the same, because of two reasons. First is that I want to see if anything changed. Second is fact, that they are glued and I do not want to remove them till they wore out. Front shocks now have hard springs and 400 oil. Rear springs were not changed but I used 250 oil.

What else? Because I am lazy, instead of limiting travel with spacers inside shocks, I used shorter eyelets. Now car sits quite low. On photo there is no battery on board, so it is even lower in normal conditions.

As always, I cleaned everything to have "fresh feeling".

BTW. These steel driveshafts are joke. I see that pins on dog bones from gearbox side are visible worn after about 4-5 h of runs...

I hope that I will test in soon but it seems that weather will stop me for a good few days...

[Twinfan 765]

I'm not sure a firm front is the way to go with a DT-03.  There is very little weight over the front so would a soft setup make more sense instead?  A firm setup will just skip over the surface rather than absorbing bumps.  In theory, your setup is going to put more pressure on the rear which is carrying all the weight and outputting all the drive.

If you're still having problems when you try it out, that may be something to think about...

[skom25 645]

Hard to say to be honest. It seems that front is so light, that it is hard to setup it correctly.

Hard springs does not offer any SAG but soft springs are so soft, that I have feeling that suspension is almost passive.

I will try today one more time and probably go back to longer eyelets. I am afraid that I will hit chassis too often. I can of course limit travel with spacers inside but I am afraid that setup will be too hard.

To not go with theory, I will update after first runs.

[Twinfan 765]

I run soft roll bar and soft springs on the front of mine with lots of toe out, on grass and with the kit tyres, and it's pretty good for what it is - a cheap entry level kit.

[wolfdogstinkus 1718]

Who told you Tamiya's had steering?😁

[Tamiyastef 1632]

If a car doesn't handle as I want it to, my basic rule is to make changes one by one. If I change 7 things at once I won't know which change had what effect + one of the changes may limit or undo the effect of one of the other changes...  About your DT-03 the original front tires have less grip what results in (terrible but) predictable understeer. With those 4WD tires up front you get unpredictable and therefore hard to master oversteer IMO. I would start by changing the front tires back to original spec (and nothing else)

[one_hit 1011]

Firmer springs up front on an oversteering DT-03 is what I recommended because you want to minimize the weight transfer to the front when you release the throttle. Let us know how it feels @skom25 maybe you can try it with the 4WD tires 

[skom25 645]

5 hours ago, Tamiyastef said:

If a car doesn't handle as I want it to, my basic rule is to make changes one by one. If I change 7 things at once I won't know which change had what effect + one of the changes may limit or undo the effect of one of the other changes...  About your DT-03 the original front tires have less grip what results in (terrible but) predictable understeer. With those 4WD tires up front you get unpredictable and therefore hard to master oversteer IMO. I would start by changing the front tires back to original spec (and nothing else)

I know that method and will use it, but in that case, I had feeling that everything was wrong. As suggested by others, I went back to almost factory settings. Stock tires are bit rubbish and as you wrote, make car understeer a lot. With 4WD tires quick change of direction was so sharp, that car just wanted to rotate.

5 hours ago, one_hit said:

Firmer springs up front on an oversteering DT-03 is what I recommended because you want to minimize the weight transfer to the front when you release the throttle. Let us know how it feels @skom25 maybe you can try it with the 4WD tires 

Good point. 

[skom25 645]

Well...

I went for test run. Everything worked perfectly. I even recorded video to show how good it is now.

At the end I did quick run on road, to clean model as always. Something strange happened and model went straight into trench full of water...

[skom25 645]

I calmed down a little after yesterday and decided to rebuild car once again. As always, few new parts will be installed.

As I wrote, I recorded video after modifications.

It runs great now. Today I bought new tires: Dual Block K on rear and 2WD buggy on front. The same as on movie but from soft compoud.

BTW: I have also TT-02B with Sport Tuned motor. Because those models are quite similar, I decided that I will run them on the same course and record videos with comparison. It will be quite interesting which will be faster and on which parts of track. 

[Juls1 1616]

Seems like you’ve got it mostly sorted. 
 

I noted in your first vid, you had toe in at the front. 
 

toe in will cause the car to push as you enter the corner then grip as you exit the corner, this can lead to loop outs mid corner. Running tow out gives far more initial turn in grip at the start of the corner but will push slightly on exit, generally toe out is easier to drive.

i also noted your running camber adjustable top links. Make sure you’re running negative 1-3 deg in the rear and negative 0-2 deg in the front. 

more importantly ensure that the camber left to right is identical. This does not mean the camber links are equal length, that makes an assumption that the car is perfectly square. Generally that’s unlikely on Tamiyas cheaper models you’ll need to measure the camber with a testing device. If you have different camber left to right the tell tale sign is that it handles differently turning left or right. If you’re pushing turning left and spinning out turning right then your camber settings left to right are unlikely to be the same. 
 

there is little else you can change, generally as you’ve found lowering the rear and lifting the front slightly can help balance the chassis and increase rear grip in corners. 

[Pylon80 1393]

11 minutes ago, Juls1 said:

This does not mean the camber links are equal length, that makes an assumption that the car is perfectly square.

Another factor that will lead to different camber left vs. right even when the links are exactly the same length is if there are any differences in the springs lengths/constants left vs. right. Even with good Tamiya springs this happens. To get an accurate geometry it is as @Juls1 wrote: you will need to measure camber.

Now, all the above being said, if you do not have a setup station ($$$) or if you are not sure how to measure precisely with a small wheel camber gauge (it definitely gest tricky when the chassis has any free play or if the wheels are not perfectly true etc) you can at least aim to make the links exactly the same length, as a minimum accuracy standard and knowing that the chassis and springs could still be playing tricks on you. You will need calipers to measure the links.

[skom25 645]

@Juls1 thank you for description! Toe and other settings are now set regarding to manual. I will change one thing, check and then decide if it is better or not.

I measure links using caliper. I am afraid that there is too much play, to use special tools and check angles.

DT-03 is not the worst case. I have TT-02B with plastic driveshafts and there is sooo much play, that I am sure that wheel changes angle by a good few degrees.

At least I have good starting point and now car is fun to drive again. 

[SlideWRX 705]

On your first vid you had blue stiff springs in rear and red soft springs in front.  That is going to be a big part of the oversteer, for a rear heavy rwd car.  Switching to blue all around significantly improved the balance.  Generally speaking, for a rear weight biased rear wheel drive you want the front stiffer than the rear.  Keeping the rear a little softer than the front will keep it from oversteering, unless you throttle it just right.  The blue springs are more than twice as stiff as the red, and the original DT-03 springs are in the middle, closer to the soft red.