Drak CV/ Axel swap

[nofearmxer]

Hi Im new to four wheel racing. I got a 2000 Drakart Formula Cross that was moded by ATVR with King shocks and some other upgrades.

Well I keep breaking axels and CV's. Right now I'm running 2CV Citroen axles and CV's, they are a two piece axle. I was told that these machines wernt made for jumping...if thats so I want to make this thing near bullet proof. What do I need to do? It seems to have too much negative travel, it sits up high in the stroke so as soon as you leave the ground the schock only extends about 3 more inches. At full extension my axle angle is so great it puts my CVs in a bind and...boom, destroyed. I was thinking if the rear suspension was wider the axles would be at less of an angle and therefore less binding. What would be the best/easiest/strongest way to do this? I would like to get into a one piece axle just because i get the feeling they are stronger. How could I do this? If the rear suspension needs widened I thought about just building a 5 link. Any ideas on a fix?

I plan on learnig all of this stuff, I signed up for a 4year mech. engineering degree but dropped out. So I have the will to learn all of everything, I want to use this Drak as a starting point for a up to date engineered single seater desert racer. I plan to go to school or somehow learn what I need to know to build these things, then be able to afford to race em. So tell me everything.

I tried to post a pic but I failed all 100 times. All while changing or widening of the suspension I'll have a million questions as far as geometry and shock location since my trailing arm sock mounts were changed by ATVR for the Kings.
[IMG]file:///C:/Users/mitch/AppData/Local/Temp/moz-screenshot.png[/IMG]

[K-fab]

I know that car. The old ATVR setup Drakfart suspension worked well. Neil and Jay did a very good job redoing the rear suspension.

The issues you're having with the CVs going poof-kaboom is that they can't handle the extreme angles that Alain built into the car's suspension. (as you've stated)

One option would be to limit the down travel so that it can't extend to the point of binding the CVs. Probably the easiest option. Even if you loose an inch or two of travel, it would be well worth it. That car has, what 14" of travel in the rear as it is?

The car can be set up for jumping - much of that is directly related to your right foot too. They are VERY sensitive to throttle input as you jump. Another aspect is that smaller cars tend to nose dive (see my avatar) when you don't get it quite right. Most of your jumping will be seat time to get it right.

BTW - the car will act like a bike in the air - gas it, front end rises (or back end drops), hit the brakes, take a hard look at the dirt as you nose dive.

There's a lot of the bike stuff that will cross over once you get used to the timing of the power delivery of the CVT setup (think turbo lag).

Talk to Livewire (here on the board) and see where he's gone w/the CV issues. He has a lot of experience and upgraded items since the old 2000 year model Drak.

[K-fab]

OH! forgot something...
Your ride height is way too high. If you're running mx courses or any sort of groomed track, that thing should be slammed and sitting about another 1/3rd lower than what's showing in your video stuff. I/3 to 1/2 the suspension travel (I'd be closer to 1/2 on a groomed course) should be taken up with the car full of fuel and you sitting in it (like it was on the line for a race).

[nofearmxer]

Hey K-Fab,
I am going to go ahead and lower it and run limiting straps set to save my CVs and expensive Kings.

But I feel like I have a bunch of shock there not getting used to its potiential. And that with some changes should be able to have decent ground clearence while having the car center of gravity low, AArms sitting about parallel for stability and cornering while still using the entire stroke of the shock. i just want maxamium travel and in order to do that my CVs will blow up so thats why I was thinking re-designing or easily modifiying the rear end to lessen the axle/cv angle at full drop. Limit straps yes problem fixed but I want total use of my suspension.

Yes it seems like if you know how to ride a dirt bike right figuring everything else out in the dirt aint so hard. I would argue that there is more technique ridding a bike correctly past its limits then any other motorsport. HA I did tap my back breaks in the air once when I got to drive it..didnt notice much but was probably just the way the lip threw me. It seemed to jump level and consistent.

Any suggestions for getting the axle angle right to use these nice kings to its full potential?

[Bugpac]

Dont worry about having unused shock... Worry about the cvs, I did a bi of rearranging on my car and had zero cv issues... The key IMO is to move the rear heels rearward about 1.5" Get rid of some of the forward angle on the axles... Kfab is right, the worst thing in the world is to crank the preload way up for Ground clearance... PM livewire, he has all the answers for sure...
PS, Total use of the travel equals unfailing parts... Use the travel it should be using and it will be near bulletproof... IMO put a spacer in the kings and limit the travel... The car was designed around a funky shock length...

[K-fab]

Originally Posted by nofearmxer

Limit straps yes problem fixed but I want total use of my suspension.

Limiting down travel IS getting full uses of your suspensions - especially if you're blowing CVs at full droop.

Anything past what the CV will handle is:
I) wasted
2) useless and
C) not worth the headache.

Even though there's excess travel there burning a hole in your pocket like a hundred dollar bills in a strip joint, you can't use it (like the people in the strip joint). So give it up and make the car work within the parameters that won't break it.

Get the car set so it quits breaking stuff and then work on dialing in the suspension to work the best it can.

There is not a lot of time that the car's at full droop - over jumps, and occasionally in corners (like when you're bicycling through them....) so limiting down travel to keep from breaking the car is just fine.

Everyone wants a small, single seater w/67" of travel and 846 hp only to finally discover that a smaller car, like a Drak, only needs about 10 to 12 to work CORRECTLY. I've seen many smaller travel cars that are setup correctly kick longer travel car's butts.

Go find the pix of the Revolt that has too much travel and bad controlling of the suspension (at least in the corners). Prime example of "wrong".

[nofearmxer]

ok thanks.

Guys I just got this car this summer rebuilt motor/repaired some things but just assumed it was good to go as far as suspension. Hell the shocks are as big as the car!

Bugpac-I did see a picture from somebody on a Pilot site that added a few inches in lenght to the front trailing arm and that moved the axle back, comming out of the gearbox close to straight. I have thought about this. I thought you wanted to use all of your travel, and if your not then your susp. settings could use some tweeking, just thinking back to racing days but thats why they always put o rings or zip ties or some indicator on my forks to get them dialed in. oh and I've heard of shock spacers but have no idea what you mean, spacers where they mount or internal shock body spacers...and then do what?

K-Fab- Your point goes to show just how little i know and need to learn about engineering and efficiency. Yea I have everybit of 14" of travel. I understand how to get the rear end set up since it has adj coilovers and bypasses but I have Axis 4 wheeler type shocks on the front. If I move the spring up/drop the front end how is the single shock going to react different from the dual set up on the rear? Can it work as smooth as a dual shock set up..I dont even know the details of a dual set up other then its what the big boys have so it must be good and a single shock set up be...not as good.

Livewire- You will hear alot from me, expecially if yours is a 2000 also. Alot of Rotax and axle questions.

[Bugpac]

If you put a longer shock on you can get even more travel, But it is useless if it wont work.. When i redid the rear of my car, It had about 14" and was plenty i think originally it had 16... The drak originally came with long shocks, and they put shorter shafts in them or a spacer, this was so they didnt have to be redesign.. They have had numerous different shock manufactures on the same set of mounts.. Big shocks,dont mean youll get a nicer ride, dual shocks dont mean so either, The key is having something that works right, I had single "dual rate" bilsteins on my car.. I got the car to bottom with a few inches of frame clearance, and not max the cvs without using any straps...

[K-fab]

Up front - Axis shocks - very, very good units. You'll have all you'll need to work with, just need to get the spring rates and ride height adjusted. You have the basics needed up front. Those are from the time that Mike Hallock was still making Axis shocks (pre-Penske buy out) and are the generation of Axis that you want on your ride.

Out back - There's a little history about the car's setup and what ATV Racing was trying to accomplish. Sit back and enjoy the read.

When Alain (the guy who came up w/Drakart - from France) first came to ATV Racing (back in 99, I believe), he brought a vehicle that was set up for European style off roading. Smooth(er) terrain, less "suspension use" setups and such were the original idea. Once he got the cars here, he realized that the desert, or out west (where the majority of the car's market was intended on being) was brutal comparatively. He started working with Neil and Jay and talked them into being the US distributor for the Draks. At the time, Alain was in Canada.

ATV Racing, sitting in the northern side of Phoenix, just off I-17, was about 10 minutes from the door of the shop to throwing dirt in the desert. (too bad this area's not open anymore. - it's now about 20 min. to go play)

ATV Racing had just become a King dealer.

So, taking into account what the car was going to be used for, the new King access and that Jay and Neil are both always looking to improve and make things work better, they yanked off the original shock system and started modding.

Here's a pic from Buttercup (Glamis for those that are unfamiliar with the locals of the Dunes out west), April 2000. This is the very first Drak that ATV worked with:


click on it for a larger pic.

Notice the single rear shock.

So, in an effort to make the car work even better out in the desert, especially through the whoops (if you've never seen desert whoops, you'll have no clue. They're nothing like a motocross track's whoops. Big, rolling and can be absolutely vicious - they're exceptionally punishing) Jay threw on a set of the new King by-pass setups. They were experimenting. Plain and simple.

The dual shock setup, especially on a sub 1000 lb car, (the Drak weighs about 750 - 800, I think) is total overkill. There is absolutely no need for the dual setup.

Yea, it makes the car look like a "real desert racer!" Oohhh, Ahhh .

They're great shocks (the by-pass) and they look cool and it makes everyone thing "WOW, that thing's bad-ass! Look at the shocks! !"

Unfortunately they are a total waste of space, an additional 40 to 50 lbs and you'll be a lot happier if you yank them off and focus on the coil over side of the system - getting it set up correctly.

This means getting spring rates right, shock valving correct and most importantly (because you don't want to start tuning somewhere in the middle instead of the beginning of where you should start) getting the shocks set up so that they work with the suspension geometry that you have.

Yes, I know this is not what you want to hear.

"But it has those killer dual shocks on back!". yea, it does and you don't need it.

So, where to start?

The single coil over in back is more than capable of taking care of the rear end of the car. It's a great shock and very tunable. As old as they are, they need to be rebuilt too. It's simple to do.

Let's first start out with your ride height and spring rates:

By raising/lowering the collars on the shock, you'll adjust the preload of the shock spring. This is what sets ride height (provided your spring rate is close). Basically the preload tells the spring how hard to push back in the initial travel. Push the spring down harder, it's going to push the car up farther.

Your car's spring rates should be darn close. Jay and Neil took a lot of time getting it figure out.

So, if you slide the collars on the shocks up a bit (can you get pix of the top of the shocks, front and rear, so we can see what sort of pre-load you have?), you'll be able to lower the car so it works better and handles better on groomed tracks. Yes, motocross style tracks can be rough, but nothing like the desert - drop the car, make it work for the situation - you are not in the desert and the car still thinks it is. You're not loosing suspension movement, just changing where the chassis sits in the movement.

Once you've dropped the ride height and removed the by-pass shocks it will be time to start tuning the shocks. I'm guessing that the coil-overs are pretty much gutted as far as any damping ability. I'd be glad to ask Jay if he recalls what he'd done if you'd like.

Getting the damping set will require a little time on your part - but it will also give you the chance to put a travel limiting spacer inside the shock to keep you from blowing the CVs. The spacer will go under the piston and shim stack and not let the shocks (over)extend.

You'll need to get someone with a camera to help you out. Looks to be no issue, as you've already done a video.

Run the car through the whoops, over jumps and such and get the video person to try to focus on the rear of the car as much as possible - not some close up zoom, just make sure we can see what the suspension and chassis are doing in relation to the ground the car's going over.

Once you get some footage, dialing in won't be an issue. I can help, bdkw1 can help (hint, hint Brian!), Livewire can help and quite a few others can too.

You have the beginnings of a great ride. The older Draks needed some serious TLC to make them work up to snuff, but you're already half way there. It's just time to dial it all in correctly.

Yes, you'll loose a couple inches of travel.
Yes, you'll loose those fancy by-pass shocks (and a HUGE amount of weight comparatively)

But you'll end up with a machine that will do what you're wanting and expecting.



Side note: One thing that Jay figured out was to move the rear lower link mounting position. I can't recall which way he moved it, but axle plunge went from something ridiculous like 4"+ down to about .5". It pissed off Alain that he'd changed the geometry of the suspension ("That is not what I designed!" I heard screamed in the shop as Alain looked over Jay's mods. It was not a pretty scene that afternoon...), yet the mod ended up showing up on the two seaters and later single seaters. CV issues went away for the most part.

[LiveWire]

My travel is not limited, but my ride height is lowered. That does not cause a loss of travel. The wheels drop and you get all of it when landing from a jump. You can see that in the picture in the other thread that my wheels are all the way down when in the air. Lowering the rid height makes your CVs run at a lower angle most of the time. Peak angle is not your only concern. Take a front wheel drive car and drive in a circle in a parking lot as fast as you can for an hour and you'll toast the CVs.