R40 ride height ?

[nitrolight]

I finally put together my R40. It took weeks since
I bought it off e-bay and it was missing a ton of little
parts... anyway... I haven't made any adjustments yet
but I'm looking at a 19mm ground clearance...
yes the foam tires are new and haven't been shaved but
19mm ? The shocks are all 65.5mm long. should I
add a couple o-rings inside to shorten the length?

 

[Bouzouki]

Always run the lowest ride height possible to reduce CG.

If you have a bumpy track, obviously you will have to run on the higher side.

I usually run anywhere from 4mm to 5.5mm.

I wouldn't go lower than 3mm or higher than 6mm.

 

[Diver6127]

Wow, that's pretty tall. Back off the collars on the threaded shock bodies. Trueing the foams will help the performance and reduce traction roll ... to a point but I think the shock collars are the culprit here.

When you do true down the foams, most performance is seen around 63mm. If you keep the size the same between the front and rear diameter (no split) there will be a natural overdrive gearing for the front. If you do a 1mm split(smaller in the front), front and rear drive ratio's should be relatively close. This is if you keep the stock pullies.

 

[rossb]

I finally put together my R40. It took weeks since
I bought it off e-bay and it was missing a ton of little
parts... anyway... I haven't made any adjustments yet
but I'm looking at a 19mm ground clearance...
yes the foam tires are new and haven't been shaved but
19mm ? The shocks are all 65.5mm long. should I
add a couple o-rings inside to shorten the length?

Is that height measured with the collars backed all the way up? Something sounds very wrong. I have the stock shocks set at 65.5mm and if I back off the collars my car will basically drag the floor. You should not need to modify the shocks. I am currently running 4.5mm up front and 5mm in the rear. I adjust my ride height as my foams wear.

 

[nitrolight]

Well... I feel like a big idiot... I backed off the collars all the way, and the
car is sitting around 6mm off the ground... me dumb...
Thanks guys...

 

[rossb]

That still sounds a little too high. Are you using the ride height gauge?

 

[nitrolight]

It's 5mm in the back and 6mm in the front measured with a height gauge...
when I push the back down it touches the ground... when I push the front down
it stops about 2mm from the ground...
I haven't gone through and adjusted droop, downstops, ect, ect yet...
My understanding is that I don't want the car to be able to touch the ground, right ?

 

[rossb]

It's 5mm in the back and 6mm in the front measured with a height gauge...

The height you set depends on where you are running. That’s a bit high for a high traction groomed track.

when I push the back down it touches the ground... when I push the front down it stops about 2mm from the ground

Your bump stops (also called upstops) sound like they need to be adjusted. Do it evenly on both sides. Personally I use a thin strip of paper and I put it under the stop and move it around to see when the screw starts to make contact with the chassis as I compress or raise the chassis. I do this on both sides in an effort to get both screws set as evenly as possible.

I haven't gone through and adjusted droop, downstops, ect, ect yet

Droop is the same as downstop. The R40 also has upstops, which are used to set the minimum chassis ride height with the suspension compressed.

My understanding is that I don't want the car to be able to touch the ground, right ?

Correct as that will unload your suspension and reduce your traction.

Check the setup sheets for an idea of what the racers are using. You will have to change things around a bit to suit your track conditions and your driving skill. Leave the wheelbase, track, caster, ackerman, roll centers, camber links, hinge pins, and shock positions at the stock kit settings. Double-check your camber and toe. The stock kit settings put the front and rear camber at around –2 degrees. That is a good starting point. Front toe should be somewhere in the +0.5 to –1.0 degree range depending on track conditions and your driving skill. The racers seem to run a droop setting that is about 0.5mm – 1.0mm less than the ride height. They are running a bump stop setting that stops the chassis just before it hits the floor at 0mm.

All of this is important but if you can’t drive the car you will get beat by an out of the box RTR car.

 

[nitrolight]

Thanks rossb for the great info !
I'll be tweaking the car latter today

 

[nitrolight]

OK... one more question...
I just made adjustments on the car...

4mm front ride height
5mm rear ride height
width 200mm front & back
caster 2 ( leaning back )
-2 camber front & back
0 front toe
-2 rear toe
front droop is 3mm
rear droop is 2mm
down-stops are all +1 ( Hudy Droop gauge ) all four corners
I evenly adjusted the side screws on the front sway bars to
prevent the car from bottoming out at 1mm from the ground.

Now my question... How do I prevent the rear from hitting the ground ?

 

[Bouzouki]

Sounds good.

On my MTX-3 their are upstop screws for the front and rear, can't help you finding them on the R40.

 

[rossb]

How are you measuring your droop? 2mm in the rear does not sound like enough. You probably should have more droop in the rear than you do in the front.

Now my question... How do I prevent the rear from hitting the ground ?

There are upstop screws on the rear arms. Part Z23 on this page.

You can see them on the bottom left hand corner of this picture. The droop and bump stop screws surround the back side of the hinge.

 

[nitrolight]

Rossb you rock!
So now I have my rear bottoming out 1mm above the ground.

I'm measuring the droop by placing the car on a setup board, pushing
the front and rear so the suspension settles, placing a ruler vertical next
to the front of the chassis and taking a measurement at the bottom of the
chassis then I'm lifting the car from the center front, and taking another measurement as soon as the tires lift off the ground. then I do the same for the
rear... Should I set the rear droop to like 5mm or 6mm ?

 

[rossb]

I would probably try around with 4-4.5mm of rear droop. That will get you close to what the racers use on the setup sheets.