Chassis Life

Graham Zerga · Joined: 24 May 2004 Posts: 62 Location: Belgium, Alabama,

Hi guys,
Would anyone be able to tell me some characteristics of a worn out chassis?

I'm trying to figure out if my chassis has had it. Its a few years old so logic says yes but when it works its as fast as anything out there, thats on a green track, usually if we show up for pracitce the day before a race, everything looks great for the race the next day, then the following day it always goes wrong as the kart starts to tighten up and I just can't dial it out as any small amount of grip goes down on circuit.

The kart is poor on long corners, understeers and wants to push on, feels like its probably not lifting the IR.
In the tighter stuff I can get it turned in alright usually but it won't release from corners.
I've tried everything, changing a front spacer here or there won't cure it, we've fiddled with axle placement, seat placement, etc, etc, etc and it really doesn't change the kart any amount.

Tyres heat very quickly, and the kart tighten up after a few laps then fades.

I'm really asking how you deal with an older chassis to bring back some life in it.
I wish I could just go get a new one but its really not an option unfortunatly (I know, I'm in the wrong sport if money is a problem...lol) and I hope I'm not just wasting my time racing this one.

Steve Frank · Joined: 06 Dec 2002 Posts: 626

When I first started Yamaha Pipe racing, I bought a used TOPkart that had two seasons of national level competition on it. I raced it regionally for a couple of years- Won only ONCE with the thing. Had lots of problems similar to what you've described...Had to dial in lots of front end geometry to keep from understeering on turn in. Kart bound up in long sweeping turns. The kart was never EVER loose no matter what I tried... After a couple years, I bought a brand new chassis from Trackmagic. I could not believe the difference. As soon as I drove the new kart, I wished I had bought a new chassis several years earlier- would've saved me alot of frustration. However, given your predicament, some things to try:

Move the seat straight up to see if you can use a higher CG to assist lifting the inside rear in lieu of lots of front end geometry.
Check the kingpin bearings and tie rods for any sort of slop. Old kingpin bearings will wreck a kart's handling.
Experiment with seat struts.
Maybe use a harder compound tire if rules permit.

Best of luck.

Patrick Hubbell · Posted: Fri Apr 29, 2005 10:44 pm Post subject:

How old are the tires? BStones YHC's? good for one maybe two races. After that they are about as usefull as a flower pot. Totaly inconsistant.

If it's fast sometimes at the same track but not always I would suspect the rubber. If its fast sometimes and at different tracks then look to the set-up. There is no better feel than a new chassis.
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Patrick Hubbell

Graham Zerga · Joined: 24 May 2004 Posts: 62 Location: Belgium, Alabama,

I was using older tyres for the last few races but had new tyres on the last meeting, this doesn't seem to be the problem.

It can be fast at any track when we get there on Saturday, when the track is fairly green and will still drift about a little. But it usually becomes so so tight by Sunday evening for the main race after getting progressivly worse through the day as rubber is laid.
Its the same story on all tracks we visit (about 5 in the region, all various surfaces, types of coners, etc..)

Now, I know you have to adjust the chassis through a weekend, and I used to be able to read the track to a tee when I was in 4-cycles but its almost like the chassis just doesn't have that range of adjustment to keep it freed up.Small changes like "use another spacer", or "remove a strut" just doesn't ever make enough of a change, even moving the seat around hasn't netted a great result. I'm wondering if its just going a bit soft and loosing its "spring".

Patrick Hubbell · Posted: Sun May 01, 2005 7:18 am Post subject:

If it doesn't respond to small changes anymore it's probably worn out.
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Patrick Hubbell

Graham Zerga · Joined: 24 May 2004 Posts: 62 Location: Belgium, Alabama,

Hmm, yep, my worst fears seem to be confirming... Sad

Oh well, I can re-mortgage... Very Happy

Philip Johnson · Joined: 16 Sep 2004 Posts: 140

I had a chassis like that also. It wasn't that old, but it had been raced hard, used for one national sticky tire event, and it had cracked where the rear crossbar joined the inside rail and been re-welded. Same symptoms, and I too had to pony up and get something new. I assume you've checked for cracks, which would be academic because I think you've realized the chassis pretty much gone.

Michael Polizzi · Joined: 18 Jul 2001 Posts: 1565

For an economical solution you could just replace the bare frame. usually around $900-$1000, costly still, but better than the full setup.
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Michael Polizzi
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Gary Kozuma · Posted: Mon May 02, 2005 9:39 pm Post subject:

I'm sure you've already thought of this, but if it has removable bars, try putting them in. My first chassis was a CRG Heron, man was that thing bad.

Phil Lovelady · Posted: Tue May 03, 2005 7:37 am Post subject:

ALL CHASSIS WILL BECOME "LAME" AFTER A WHILE especially the European/ Italian chassis (weaker metals used). I bought a brand new Corse Veloce 125 chassis and by the end of the year running the WKA nationals all year, the chassis turned to junk for that level of competition. I finished 2nd in the WKA points, but had I changed chassis sooner the outcome could have been better. Chassis handling is a personal thing, what works for "joe racer" wont work for you perhaps. The old saying, "the stopwatch doesn't lie" is the only truth. If you are competing on a National or even a Regional level, it is wise near mid season to have another chassis ready for the remainder of the season to be absolutely on top of your game. Just my two cents!

Doug Ring · Posted: Tue May 03, 2005 4:52 pm Post subject:

Michael's call on replacing the bare frame is dead on - over the last few years, I've had to do this three or four times (ususally cracked frame sections, replaced under warranty) and it's only a 4-5 hour job. If you have a fairly recent "major brand" chassis (Margay, Birel, CRG, Emmick, Top Kart, etc), the bare frame should run ~$1K - a whole lot better than a complete chassis at $3500+! Call the chassis importer and review this option with them.

Erik Maxfield · Posted: Sun May 08, 2005 2:50 pm Post subject:

I have managed to put a bit more stiffness in an older chassis by fabricating a new floorpan out of carbon/kevlar. This ended up helping to offset the "flexible noodle" syndrome. Made front end adjustments effective and also stopped pan breakage (aluminum will always break eventually due to vibration/stress reversals where composites can be designed for a infinite fatigue limit)
You can cut out a form from aluminum or any other sheet metal. I set up 2 layers of BID Kevlar at a 45 degree angle to the longitudinal axis of the kart. One more aligned with the longituninal axis. I then encased the whole thing in two layers of BID Carbon for stiffness. Materials are available from aircraft spruce. Use the Aeropoxy as it is less toxic (and sufficiently strong) and USE A RESPIRATOR (half mask with the appropriate cartridges). Most of the aircraft epoxies are a fearsome liver toxin as well as a carcinogen.

I put one of theese together for an older chassis that I got tired of replacing floorpans on. I got the extra bonus of the chassis becoming stiffer and more adjustable.
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Erik
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