4 replies to this topic

[pekarting]

Hello all,

I've always had a theory about the utility of the seat struts of a racing kart. But I've read an article on a website and it tells just the opposite! So I thought some of you could maybe give me some help.

I was told that the struts (from the top of the seat to the top of the axle bearing, at each side) tightened the chassis so it has less capacity to flex and make the kart grip. Thus, with the struts a kart would be looser than without them.
The article I read tells that the struts transfer the driver's weight to the wheels, so they had more load and more grip. But I would say that at the same time the chassis is having less flexion so the inner rear wheel is not lifted enough, forcing a straighter trajectory.

Any idea?

Thanks.

[EvilPhil]

It all comes down to tyre pressures and heat i think. In the Wet those struts are loosened or even taken off cause massive flexing that you can actually feel as a driver. It can also make a huge diffrence in the dry between over steer and under steer... why ? i dont know ?

But yes the other thing is that in the dry lifting the inner rear wheel doesnt really matter but if you where to do that in the wet there isnt enough traction on the outter rear wheel to prevent a slide hence it causes huge over steer snap. So by loosening those structs you keep all wheel in contact with the track.

The front track is also widened hugely in the wet on the kart so maybe it also has something to do with that.

[Manson]

IMHO, the struts tighten up the kart and help free it up. More slide, less bind. In the wet, on even the cold, removing the struts causes the kart to flex more and give more grip. We ran a 1 hr enduro a couple of weeks back and that's what we did as the weather was about 6 degrees C. That kart handled better until the throttle return spring snapped causing full throttle for the vast majority of the race. Then I had massive understeer!

[pekarting]

Thanks EvilPhil.
Thanks Manson, that's exactly what I thought. So, I can't agree completely with what I read on that page. I quote it:

On a Tonykart chassis, the factory recommends running two seat struts on both sides of the seat running from the very top of the seat to the two outer bearing cassetes. On the motor side it may only be possible to use one strut. The seat struts allow the high leverage point of the driver to be used to transfer load to the rear tires and thus create more rear end bite. When the extra seat struts are removed, the drivers high position on the kart is not taken advantage of and minimal load is transferred to the rear tires. As a result, the kart becomes extremely loose. The seat struts are therefore only removed when all else fails to loosen up the rear of the kart. If you do have to remove seat struts, try removing one set at a time.

Sure the outer rear wheel will have more load with the strut, but you have less flex...

By the way, Manson, do you managed to stop it??

[Manson]

It was a Honda 6.5 hp motor so slowing it down enough for the corners wasn't that much of a problem. Getting through the tight switchbacks was tough to do cleanly lap after lap. At race's end, I reached back and manually worked the throttle so I didn't come racing into the pits out of control! I didn't feel like doing that the whole race so I left it wide open. I would drive by the pits where my buddy was with my right foot up in the air, off the pedal with the Kart still going like hell! I tell ya, after an hour hopping curbs and the like, I long for the suspension on my midget.