Oil Dampers That Sit Low

[Malakite 6]

I have just finished building my BRAND NEW Marui Ninja (I'm so excited, it looks amazing!). The thing I've noticed is that the back dampers are sitting a little low and if I pull them up and let go, they lower slightly. Any ideas what causes this? Could it be old damper oil (i.e. its been in the box for years) or something else?! Any help on this would be great!

Also I don't know if I can bring myself to drive it as its sooo perfect, but I always told myself I wouldn't turn into someone who keeps a shelf queen and that all cars are there to be run, but the fact I have a couple of older ones in my collection now, I'm wondering if I should just bash those?! What would you do in my situation?

[WillyChang 1814]

Depends on how you've built them - were all their shafts in the same position when you topped up & capped them?

Volume of the shaft causes compression or vacuum depending on where they were before capping.

[Malakite 6]

Depends on how you've built them - were all their shafts in the same position when you topped up & capped them?

Volume of the shaft causes compression or vacuum depending on where they were before capping.

Hi mate, whats the time down under at the mo?! It's 1am here!! Well all the shafts were fully open when I screwed all the caps on so I don't think it can be that??

[markbt73 5316]

Do you mean with them mounted on the car? If so, that's how it's meant to be. You actually don't want the suspension to be sitting right at the top of its travel. You want the wheels to have room to go down as well as up. It sounds like your Ninja is acting exactly how it's supposed to.

Not many entry-level Tamiya kits are set up this way, but then, not may entry-level Tamiya kits handle well.

Oh, and if it were me, I'd run it, albeit carefully. Just save the real abuse for other cars, and give the Ninja a little gentle exercise. It will make you happy to see it in motion.

[Malakite 6]

Do you mean with them mounted on the car? If so, that's how it's meant to be. You actually don't want the suspension to be sitting right at the top of its travel. You want the wheels to have room to go down as well as up. It sounds like your Ninja is acting exactly how it's supposed to.

Not many entry-level Tamiya kits are set up this way, but then, not may entry-level Tamiya kits handle well.

Oh, and if it were me, I'd run it, albeit carefully. Just save the real abuse for other cars, and give the Ninja a little gentle exercise. It will make you happy to see it in motion.

Hi mate yup I think you are right about running it!!....

I see what you mean about the suspension but at the same time it does seem to be rather low, but like you say perhaps that was the design? It's an awesome looking car!! I'm going to have to sort myself out a showroom to stick some pictures up

[Malakite 6]

Does anyone know if old damper oil makes any difference to newer oil out of interest?

[Spetz83 0]

I don't think it would make a difference

Remember that liquids cannot be compressed (well they very slightly can)

So, when the shock goes in, the rod takes up volume which means that the cap on top (which is air on the other side) has to pressurise the air.

Now, if that cap is deformed (from not putting it together properly, or age etc) it'll have an effect on the shock, ie, when compressed it wont come out again. At the same time if you put the cap with the shock compressed a bit, it'll have a tendancy to always go to that spot (ie, the air behind the cap will be a vacuum otherwise)

[Mad Ax 9325]

Markbt is right - I'm always "shocked" that so few RCs actually sit with slight compression. After all, your family saloon wouldn't handle very well if the shocks were always fully-extended - the suspension would be way too firm, the wheels would leave the ground after every bump and the bumpstops would knock and wear out quickly.

Spring tuning is a very fine art and, unless the vacuum is sucking your shock back into the position, the ride height will be affected by the springs, not by the shock oil or damper setup. "Dampers" (the clue is in the name) are there to "damp" or reduce the bounce effect of metal springs.

[hedge 314]

Does anyone know if old damper oil makes any difference to newer oil out of interest?

Hehe old damper oil is err oil based, where as most new damper oil is silicon based ;-)

Paul

[Spetz83 0]

Mad Ax, in RC terms though comfort is not an issue

So, in some cases having no droop (ie, no suspension compression under the weight of the car) is good.

Imagine the rear "sagged" by it's weight, when you let go off of the throttle the rear would lift naturally and the car would spin out

[94eg! 834]

Mad Ax, in RC terms though comfort is not an issue

So, in some cases having no droop (ie, no suspension compression under the weight of the car) is good.

Imagine the rear "sagged" by it's weight, when you let go off of the throttle the rear would lift naturally and the car would spin out

That's the complete oposite of what would happen. With no droop the rear would still lift, but it would take the suspension & wheels with it leaving only the tire's flex to keep it in contact with the road. This will most likely result in a spin out. When the suspension is allowed to droop, the suspensions downward motion means the wheels and tire are free to stay in contact with the ground as weight transfers off the rear tires. You never want to run the suspension topped out like that. As mentioned earlier, every little bump & dip and weight shift would cause the tire to loose contact with the road making the vehicle very unstable in all aspects.

To the OP: If you built your shocks at full extension, it's neither the oil nor the build technique lowering your car. If you feel your suspension is sagging too low, you need to adjust the spring perches to raise the ride height. If those are not adjustable, then you need try a different damper mounting hole on the chassis (one closer to the ground). If that's not an option, you need to snap on some of those plastic C shapped clips around the shock body that the spring sits on. They are sold as a Tamiya option part and come with the Dyna Storm and Top Force Evo. They will fix your problem...

For off-road, ride height should be set so the driveshafts are parallel to the ground. This puts less stress on dog-bones and universals...

[Spetz83 0]

EG, having no droop definitely has it's drawbacks and at the same time having droop has positives too

If you have a lot of front droop that means when you throttle the car, less weight goes on the front wheels (front lifts, weight transfer to the rear). You might want this to make sure you don't oversteer etc

However having rear droop means when braking into a corner the rear will lift up which will transfer weight to the front (and away from the rear) meaning it'll oversteer

Not to mention that having droop (lets say front and rear) means that in a corner, the inside side of the car lifts effectively highering the centre of gravity

Have a look at race cars, their spring preload, droop etc is all adjustable. I think you can even use something like Buddy Club N1+ coilovers in street cars to adjust it. Anyway, if you notice when these cars are lifted, they have little to no droop because on flat surfaces it's better

[94eg! 834]

I disagree...

[Lonestar 1]

competitive electric touring car racers typically run their cars with 2 to 4mm or droop... that's with 5mm ride height. A car with no droop handles just plain wrong.

you gotta love technical discussions on tamiyaclub

Paul

[Spetz83 0]

I'm not saying I am 100% right and can't be wrong

But from what I've read, my understanding of physics, car behaviour and from setting up my car what I say seems to be correct

Like I said though droop isn't "bad" but rather it's a way to tune a cars behaviour

For example, set up a car with lots of front droop and you'll see that on acceleration (where the front will lift) it's steering response and overall front grip would be less

It's like in a FWD car when you set it up for drag racing, you don't want the front to lift and you especially don't want the rear to sag because both of these conditions would render less front end grip

[Malakite 6]

Hmmm very interesting answers, but all different from each other and hard to know what is right and what is wrong!

I imagine from it all, that some suspension droop is good for handling. My rear droops more than my front end, the car is a 4WD so I think this all means its 'OK'?? One thing though, is that I could screw the suspension into lower settings on the ars, which I guess means it won't droop any more but will stiffen it up a little? Good for onroad but not offroad I guess as clearance is required then?

Finally am I right in thinking that I should get some extra suspension clips for the springs so that I can tighten the springs to make the suspension a little harder in terms of resistance?

[94eg! 834]

Hmmm very interesting answers, but all different from each other and hard to know what is right and what is wrong!

I imagine from it all, that some suspension droop is good for handling. My rear droops more than my front end, the car is a 4WD so I think this all means its 'OK'?? One thing though, is that I could screw the suspension into lower settings on the ars, which I guess means it won't droop any more but will stiffen it up a little? Good for onroad but not offroad I guess as clearance is required then?

Finally am I right in thinking that I should get some extra suspension clips for the springs so that I can tighten the springs to make the suspension a little harder in terms of resistance?

Adding & removing clips doesn't make the suspension harder or softer. It ONLY serves to adjust the ride height. Since I was a kid I always wondered why Tamiya called it tension adjusters as this is very missleading. So only buy more if you really need more ride height...

Moving the lower damper mount to a hole that's closer to the chassis, the suspension will become softer. All things being equal, this should lower the ride height slightly (usually not the case due to shock angle). This is because you are reducing the amount of damper compression in relation to wheel movement (called wheel-rate). If you move the lower damper mount to a hole that's further from the chassis, the suspension will become stiffer. This, in turn, should raise the ride height (unless the damper is laying down more).

[Malakite 6]

Adding & removing clips doesn't make the suspension harder or softer. It ONLY serves to adjust the ride height. Since I was a kid I always wondered why Tamiya called it tension adjusters as this is very missleading. So only buy more if you really need more ride height...

Moving the lower damper mount to a hole that's closer to the chassis, the suspension will become softer. All things being equal, this should lower the ride height slightly (usually not the case due to shock angle). This is because you are reducing the amount of damper compression in relation to wheel movement (called wheel-rate). If you move the lower damper mount to a hole that's further from the chassis, the suspension will become stiffer. This, in turn, should raise the ride height (unless the damper is laying down more).

Yup that's what I have done so at least I know I've done the best I can no probs, it's the design of the car that makes it sit slightly down on the rear shocks, but as mentioned on this thread, that is supposed to be the way for better handling, and it DOES handle REALLY well, so all is well