How to balance wieght, ride height and spring rate

[Maxbashing]

Hi all,

I am fairly new to this racing thing and need some advice on a Cougar SV setup.

I entered my first race this weekend and it went really well but I was finding that I really would like more rear end grip as I come out of corners (I'm sure a softer throttle finger will also help).

To try and achieve this I am trying to put as much weight towards the rear as possible but as I do this of course the ride height is dropping. To counter this I have wound more pre-load into the springs but my brain is telling me this is stupid as it will be stiffening the rear end and therefore making it more likely to slide.

I bought the car second hand so I am not 100% sure about the current spring rate but I presume they are the kit standard ones, I was thinking that I would like to put on some softer springs but again I am concerned this will make the ride height issue even worse.

Can anyone provide any thoughts?

[mark christopher]

putting more tension on a spring does not make it stiffer, the rate remains the same, unless you had a progressive spring. only way to alter spring tension is to fit a defferent spring rate

[Maxbashing]

Thanks Mark.. Since reading your post I have read some things online (to remind myself of my GCSE physics) and of course spring rate isn't impacted by preload it makes sense now I think about it, please excuse my stupidity.

So now I have demonstrated I'm a fool anyone got any other thoughts on improving rear end grip? I have already shifted the shocks to the back of the wishbones, I have a Trishbits brass weight coming (thanks to the for sale section), I am looking at softer springs and I have read the idea of running a the smallest possible spur gear and a bigger pinion to shift the motor back. I am sure that running Saddles would would help but I have several good quality stick packs and I'm reluctant to spend a fortune on MORE new batteries. The car has the +8mm chassis fitted and I have the rear wing set at the maximum angle of attack. I am running Bowties on the rear and proline ribs on the front with soft inserts.

I am trying to get my head around roll centres and when I can work this out I might try playing with that too.

To give some detail the track is very low grip loose dirt with a few small jumps. I am finding the back steps out on me as I turn in under braking and as soon as I try and get on the power as I leave the turn. I guess the issue under braking is more my skill/technique than the car but I was definatley having to wait longer than others to get on the power.

[mark christopher]

have you had a look at the schumacher site in the cougar set ups, sure there was a dirt one in there, dont worry about asking, as you never know unless you ask.

[Maxbashing]

Yer thanks Mark I have been looking through the setups the issue I'm having is that many of them are for named tracks and being a noob I have no idea what surface those tracks are! I will keep researching the tracks and see if I can find something similar to what I race on. I guess I was hoping that someone might just have some general suggests that might set me off in the right direction.

[adamjimny]

What surface do you race on?

[Battle_axe]

i would start here http://www.petitrc.com/setup/schumac...224/index.html

[mark christopher]

Originally Posted by adamjimny

What surface do you race on?

answer in 3rd post.......

[moth898]

Originally Posted by mark christopher

answer in 3rd post.......

modify the rear arms and move them as forward as possible by dremeling them and shimming them in the inner and outer pins. run a shorty pack across the rear. the +8 mm chassis and top deck are a big help. last thing is the inline steering arms. the rest is for you to figure on your own.

[fastinfastout]

your kidding yourself running any mid mount 2wd on loose dirt..........sorry to tell you, it's the truth. You are giving away too much traction compared to a rear motor 2wd on loose dirt.

[Maxbashing]

Thanks everyone for your thoughts so far. Special thanks to Ulrich for sending me over your full setup. I am about to buy a dirt spec chassis so I am hoping that might help. Bit of an odd question but I'm sure I remember seeing a thread on here where people had talked about using the Ds rear with a normal chassis. Does anyone else remeber this or know anything about it?This really appeals to me as the club also has a very twisty grass track so I was hoping that this might provide a good compramise for both. While I'm aware that maybe this chassis is never going to be the best nor is my driving! I also like the idea of still being able to use my shell and undertray. The tought of not having an undertray does not appeal with all the dirt and small stones that come off the track. I am only going to be racing at local club level and have no ideas that my driving skill is ever going to take me further than that.

[mark christopher]

where are you based? anyone else run a cougar at your club?

[Maxbashing]

I'm in Norwich and perhaps should have done some more detailed research before buying the car as people at the club tried to run the cougar but all switched to other things! (not a great sign) As I said my driving is pretty rubbish so I am just looking to make the car a bit more docile. Maybe one day I'll swap it for a 22 which seems to be the car of choice. I really like the cougar though so if it takes a bit of work and effort I can live with that.

[Maxbashing]

Originally Posted by moth898

modify the rear arms and move them as forward as possible by dremeling them and shimming them in the inner and outer pins. run a shorty pack across the rear. the +8 mm chassis and top deck are a big help. last thing is the inline steering arms. the rest is for you to figure on your own.

Sorry just another quick point what are the inline steering arms?

[Gayo]

Originally Posted by fastinfastout

your kidding yourself running any mid mount 2wd on loose dirt..........sorry to tell you, it's the truth. You are giving away too much traction compared to a rear motor 2wd on loose dirt.

I have to disagree. Although all mid-motors are not the same (C4.1 and mid-motor 22s seem to struggle on dirt), most can excel on loose dirt tracks.
Last week we had the French Nats on a loose dirt track. The winner used a X-6², second place: rear-motored 210, third: Cougar SV2, fourth: SK1 (hand-made mid-motor car), fifth: RB5.
A pic of the track:


Sorry for the thread hijacking.

[Maxbashing]

Originally Posted by Gayo

I have to disagree.

Sorry for the thread hijacking.

No I don't think this is hijacking at all as it suggests to me that I can have a chance of making this car good! Looks like a brilliant track

[moth898]

Originally Posted by Maxbashing

Sorry just another quick point what are the inline steering arms?

http://www.racing-cars.com/pp/New_Ca...SV2/U3934.html

it gives a longer wheelbase.

The dirt spec is a little too heavy for my taste, try what I suggested, and I have a feeling Schumacher is going to release a front end option to make the chassis longer. The longer the chassis the more rear weight bias you'll have.

[fastinfastout]

Originally Posted by moth898

modify the rear arms and move them as forward as possible by dremeling them and shimming them in the inner and outer pins. run a shorty pack across the rear. the +8 mm chassis and top deck are a big help. last thing is the inline steering arms. the rest is for you to figure on your own.

sorry to bring up an old post, but how does bringing up the rear arms forward help? Is it the forward sweep of the uni's?And then with the longer chassis....

your shortening the wheelbase with the initial rear arms forward, yet then lengthening it with the longer chassis. Sounds counter productive.

I'm just a hack with car setup, so any insight would be appreciated

[danmurphy]

Originally Posted by fastinfastout

sorry to bring up an old post, but how does bringing up the rear arms forward help? Is it the forward sweep of the uni's?And then with the longer chassis....

your shortening the wheelbase with the initial rear arms forward, yet then lengthening it with the longer chassis. Sounds counter productive.

I'm just a hack with car setup, so any insight would be appreciated

You'll gain more rear weight bias by lengthening the front section of the chassis.

Shorter wheelbase will put more weight bias over the rear axle and thus gaining traction. In the past I have found that identifying that you have too much front end grip and removing it will also gain rear traction since you are not fighting the car as much.

How old is this thread?! Lol!

[fastinfastout]

so the +8mm chassis, where has it been lengthened?

and lets just say, I went from 2mm trailing front axles to inline AND shaved my rear arms 2mm, this new setup is the same wheelbase.....will it still put more weight on the rear wheels?

and if you say the shorter the chassis, the more weight on rear wheels, so why dont mid mounts come in shorter wheelbase than they do now? I will assume you will say longer is more stable, but If I was to design a mid mount 2wd(which I'm not), I would want the shortest wheelbase than the current crop of cars.