Help! Rear is always loose

[Patrick Hubbell]

quote:

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Originally posted by Joe Janowski:
General rule of thumb...when you keep trying things to solve one problem, and nothing works, you're seat is in the wrong position. Have you tried moving the seat yet? It's a pain, but something that needs to be done to achieve correct chassis balance.

Joe Janowski
Fury
GP Chassis/CRS ICC

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Excelent point Joe, this is so true about the seat. When positioned correctly minor adjustments will be more obvious than with an ill placed seat. A seat in the wrong place will make a chassi numb.

The construction of a chassis is so different from one manufacturer to another. Everything from material, the jig, tube size and placement, the welds, the welder ect. give each and every chassis it's own personality.

Adjustments like caster and track width have a point of diminishing returns. In other words there is a point where more is not necessaraly good. As was mentioned already there is a cross over point to where for instance going narrower gives more grip and then going narrower yet makes it loose.

You say you are 190lbs. so am I at 6' tall. Measure from the front axle(just ahead of your feet at the near edge(facing the gas tank) to the leading edge of the seat(what seat do you have). Also measure from the top of the axle to the top edge on the back of the seat. As far as side to side My Burton aluminum seat on the left side is right up against the pinch bolt.

I talked to your buddy Mitch he says you are running at Prairie City. This is a low grip track. When you are racing there what do your tires durometer at when you go through tech. They need to be at least 58 and no more than 60 hot.

As I mentioned before the problem may be at the front of the kart. An exit oversteer can be caused by either to much caster or an understeer wich can be caused by the following:

1)Not enough caster( i know, contridiction)
2)Not enough weight transfer to lift the inside rear wheel.
3)Incorrect seat placement.

If you have in fact an entry push and don't recognize it the kart will snap oversteer on exit. Does the rear come around slowly or all of a sudden. If it is all of a sudden then it may be entry push which can be caused by the following:

1)inside rear not lifting
2)over driving the kart, too much corner entry speed.

When the chassis is working correctly you can see it in the tires. The tread will look like 80 grit sandpaper. If it has waves going across the tread this indicates an understeer. An experienced driver who also has a great deal of chassis tuning time will be able to identify your problem.

I highly recommend you talk to Damon Meek. I too can help but Damon is the master, I'm just the "grasshopper"(student).
It takes

[Mark Shelton]

Thanks Patrick, (and everyone) for the response.
After another test session at Prarie City, I think that my setup is all wrong. I think this because it is widley different from other CTS drivers, and my changes do not give the response that I expect. My guess is that I am dealing with snap oversteer (initial push). I have been paying close attention to my turn in response (especially in turn 4 and the back sweeper) and it seems to hesitate just for a heartbeat before it goes, and then I'm loose. If I am dealing with a push, then that might explain why a softer axle makes it better, and a hard axle worse, which is opposite of logic, and what everyone keeps telling me. I am going to have the kart scaled by a shop (as opposed to the way I did it, which was with 4 identical bathroom scales, although in my cheapskate defense I did use a pretty meticulous method of pre-loading the scales and rotating them on each corner, and then figuring averages, but that's another story..) Ray might be of help here. I also have a burton seat, but I am switching to a ribtect or a tillet right away. My seat also seems to be mounted a bit low, as it sticks out the bottom of the frame about an inch. I know raising it should help with weight transfer. Funny though, for me:
rear torsion bar makes we more loose
side bolts make me more loose
seat struts in tighten me up a bunch
(no seat struts = undrivable)
4 spacers inside front work the best. 5 makes me push
Soft axle and short hubs are my current setup. I changed from a "b" axle and long hubs.
My best lap time out there is 49.1, my ave is 49.5, and my durometers are no more than 60 on hot tires. It would be great to get in touch with D. Meeks. Dee Cunnigham suggested him also. Can you help me contact him?

[Patrick Hubbell]

quote:

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Originally posted by Mark Shelton:
Thanks Patrick, (and everyone) for the response.
After another test session at Prarie City, I think that my setup is all wrong. I think this because it is widley different from other CTS drivers, and my changes do not give the response that I expect. My guess is that I am dealing with snap oversteer (initial push). I have been paying close attention to my turn in response (especially in turn 4 and the back sweeper) and it seems to hesitate just for a heartbeat before it goes, and then I'm loose. If I am dealing with a push, then that might explain why a softer axle makes it better, and a hard axle worse, which is opposite of logic, and what everyone keeps telling me. I am going to have the kart scaled by a shop (as opposed to the way I did it, which was with 4 identical bathroom scales, although in my cheapskate defense I did use a pretty meticulous method of pre-loading the scales and rotating them on each corner, and then figuring averages, but that's another story..) Ray might be of help here. I also have a burton seat, but I am switching to a ribtect or a tillet right away. My seat also seems to be mounted a bit low, as it sticks out the bottom of the frame about an inch. I know raising it should help with weight transfer. Funny though, for me:
rear torsion bar makes we more loose
side bolts make me more loose
seat struts in tighten me up a bunch
(no seat struts = undrivable)
4 spacers inside front work the best. 5 makes me push
Soft axle and short hubs are my current setup. I changed from a "b" axle and long hubs.
My best lap time out there is 49.1, my ave is 49.5, and my durometers are no more than 60 on hot tires. It would be great to get in touch with D. Meeks. Dee Cunnigham suggested him also. Can you help me contact him?

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E-mail me with your private e-mail address. I'll get a hold of Damon and get you together with him.

You don't like your Burton seat?

Axles: The soft axle will absorb more of the energy/force that is being applied to the wheels. This can be tuned with hubs. Soft axle and short hubs is the least amount of grip. Same axle with long hubs will add stiffness and promote grip.

[ December 17, 2001: Message edited by: Patrick Hubbell ]

[Mark Shelton]

The seat doesn't fit me as well as it could. I like the fit of the tilet much better. Also being that I am 190 lbs, a lighter seat (a lighter anything) is better for me. I am also concerned that it may be a bit stiff and adding to my handeling troubles by not letting the chassis work. It's mostly a fit issue though.

[Patrick Hubbell]

quote:

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Originally posted by Mark Shelton:
The seat doesn't fit me as well as it could. I like the fit of the tilet much better. Also being that I am 190 lbs, a lighter seat (a lighter anything) is better for me. I am also concerned that it may be a bit stiff and adding to my handeling troubles by not letting the chassis work. It's mostly a fit issue though.

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Maybe we can get together with Damon and you can drive my CTS for comparison.

I'm thinking your seat is to far back. Get back to me with the measurements.

[Tim Paul]

Mark,

Ray and I pretty much tried most everything at PC with the last CTS I was driving with YDS.

The hardest part about fixing problems is keeping all the other variables consistant (motor, tires, the rookie driver). It is really hard to go out as a tuner/driver and be good at both or even one for that matter. Both have big hats to wear.

When working with Ray, I found that after hours and hours and hours of trying stuff, that the biggest gains we had was when we started moving the seat around. Up, down, back, forward, more angle, less angle. After each time we made an adjustment we would try to make the kart faster with that seat position. Once we got the kart going as fast as it was going to go and I still wasnt braking any records we would move the seat based on what the kart was still doing. From there we would chase the set up again. We ended up going pretty fast, but remember I only had two races in it. Now I am in a new kart and have the bugs worked out of it, I get to start the whole process over agen.

This is a huge topic with a LOT of answers that is why you always get the runaround.

Lets make the time to talk about this soon.

Tim

PS Different karts are just that different. Emmick to CTS to new and old CTS. A new CTS is not at all the same as an old one. Neither one is really much better,but they are different. Start with a base line and go from there. Hopfuly make sence the effects of the changes and react accordingly.

Sorry for the spelling and rambeling it is midnight.

[ December 19, 2001: Message edited by: Tim Paul ]

[John Valerio]

Mark,
you're average lap time of 49.5 with a fast lap of 49.1 is pretty fast if you are running the GP track. during race conditions my understanding is that the top 3 drivers are all running in the 49's. I could bewrong but we did transponder qualifying a few races ago and a bunch of us were running in the 49's on YDS tires

PS. if you're a newbie to PC its a tough track to learn. with the lap times you've got you're right where you need to be to win. cant imagine if you pick up 3-4 tenths and break into the high 48's. good luck...we'll be there sunday 12/23

thanks
John Valerio

[ December 20, 2001: Message edited by: John Valerio ]

[David Mayhew]

John Said "PS. if you're a newbie to PC its a tough track to learn."

PC isn't a tough track!! That place is a wide, smooth, non technical track. Haha.

[John Valerio]

David,
smooth,non-technical and wide.........what did you have for breakfast????

let me quess......wheaties.

[Tim Paul]

Not to speek for Mark but one of his biggest problems is that he cant get the kart to be consistant. Some times he hauls *** and other times he is hell bent to stay mid pack.

Mark is a pretty consistant driver (or at least when I am driving with him), but unfortunatly his kart is'nt. Once he gets that thing sorted out watch out.

Tim

[Dave Boles]

I know all the guys at KLS very well. Mike and Jason were very helpful when they were around, but they are very busy with their shifter program and I was running a Montermini in a sportsman class. The majority of the time KLS was testing or racing at a different track than I was at.

I support KLS Racing and will continue to do so. I believe the MBA karts are the best available for shifter/stickie tire racing. But by changing chassis I fixed my problem and am now running up front with the other Emmicks on YDS's It was hard to get help at the club level when I was the only MBA.

[T.KUTSCHER]

DAVE BOLES,changing chassis sounds like a great advise.I think the problem wasnt the MBA,if you cant get the MBA to work ITS THE TUNER.STOP trying to guess,get hold of a pro-tuner,pay $150-200 for a day and you will be rocking or contact your shop and ask for help.You spent alot of money on that shifter,get some profesional help from a tuner.It will pay of T.K.

[Dave Boles]

Just a thought...... What if MBA was to come out with a 28mm chassis with front/rear and side removeable bars. Wouldn't this be an excellent chassis for spec classes at the club level using hard tires on tracks that have little or no rubber down? What do you think? I know this is not their area of concentration in the kart world. But it would get the MBA name some recognition outside of SKUSA.

[Patrick Hubbell]

quote:

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Originally posted by Tim Paul:
Not to speek for Mark but one of his biggest problems is that he cant get the kart to be consistant. Some times he hauls *** and other times he is hell bent to stay mid pack.

Mark is a pretty consistant driver (or at least when I am driving with him), but unfortunatly his kart is'nt. Once he gets that thing sorted out watch out.

Tim

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Tim,

the most consistant or inconsistant element of a kart is the driver. I'm not saying that Mark is not a good driver just that he is in the learning curve. Some make it through the curve learning to drive consistant lap after lap and others can vary as much as a half a second. Prairie City is a tough track, period. There it takes lots of seat time to get it correct. I consider myself a very consistant driver who can turn laps at the local track all within .1 seconds. This I can not do at Prairie City with 17 years of driving a kart.

If it is the Chassis Damon will be able to determine wha the problem is. My guess after all the discusion here is Mark may be over driving the kart with to much entry speed.

We'll get him dialed in. No doubt he will be fast.

[Roger Miller]

At the risk of repeating myself, about 20 posts ago I said:

"That said, if all is well through the corner until exit, then you may need to work on your line and entry speed. Try going in wider, and a touch slower, to get out faster and cleaner. A later apex, just by a foot or so can be the difference."

Merry Christmas, and the best for 2002!