Spindle Height

[Walt Gifford]

Was reading the manual for the used Margay I just got. It says for more front grip to raise the spindles (lower frame). Why does it work that way? I always thought when you lower the frame you get less grip. Does this have to do with the little bit of tilt you get that makes more front weight?

Gif

FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience

[TJ Koyen]

That’s the opposite of what the OTK manual says. We actually did some ride height testing this past weekend at the USPKS race.

For OTK karts, it says to raise the ride height for more grip, like you said Walt. It lowers the spindle so it presses harder into the track when turning, giving you more weight jacking.

Driver/Coach/Wrench : Innovative Performance/Exprit
Owner : Oktane Visual - www.oktanevisual.com
www.facebook.com/oktanevisual
www.instagram.com/oktanevisual

[Dan Brown]

Walt, not sure why it works that way on a Margay but we have tried it on ours and yes it raises front grip. I ran a Tony Kart last season and this Margay reacts almost exactly opposite of the TonyKart on all adjustments. No idea why. I also think the Margay is more tunable , it reacts more to each change as far as seat off the pants feel. I changed rear hub length on mine last weekend and it felt like an entirely different kart.

Dan

[Walt Gifford]

Did you say lowering the spindle makes the tire press harder into the track? Do you mean raising the front gives you more caster which transfers more weight? Margay says transferring more weight gives you more rear grip = less front grip. Must be more than one thing in play.

Gif

FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience

[tony zambos]

Guess all the laws of physics are applied equally to everything in the universe EXCEPT for karts.

LAD Specialties customer / tony kart / rotax / kt100

[Jim Derrig]

My very recent experience (2015 Italkart Rapido) is the same as TJ’s:  raising the spindle (lowering the frame closer to the ground) decreased front grip.  Raising the rear axle decreased rear grip.  Basically, if you have too much grip try lowering the ride height.

Why does it work this way?  The laws of physics apply, though the application is self-evident.  My personal theory is that the driver is like a big, inverted pendulum sitting on top of the frame.  The pendulum moves in the opposite direction of the turn (the pendulum has a velocity/vector that is not the same as the kart’s)  This movement transfers weight to the outside of the kart and creates grip.

This effect is particularly pronounced with 6’2″ me.  As you raise the driver relative to the tires, you cause more weight transfer as you turn.  More weight transfer = more grip at the outside tires, particularly the front on turn in and the then more to the rear by mid corner.  Lower the “pendulum’s” height relative to the tire, and the weight stays more centered in the vehicle during the turn and does not create as much grip.

[Walt Gifford]

But the manual says the opposite. I guess I’ll find out sooner or later, I just hate wrenching on stuff at the track.

Gif

FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience

[TJ Koyen]

How could you possibly tune a kart anywhere BUT the track…

Raising the front ride height doesn’t give more caster, the caster angle is completely unchanged. But in the same way that caster presses the wheel down into the track harder on turn-in, raising the front ride height does the same thing. This transfers more weight to the outside rear, which might give you more or less rear “grip”. Depends on how much rear grip you already have. If you don’t have enough rear grip to lift the inside rear wheel, it’ll probably help the kart rotate and dig harder on the outside rear wheel. If you already have enough dig and grip in the outside rear tire, raising the front ride height might transfer enough weight to the rear that it goes past the limit of traction on the outside rear tire and you get sliding.

You can’t tune how much grip you have, unless you change tire pressures or compound. The tires are always at the same level of traction potential. You’re changing how effectively you’re using the grip of the tires through weight-jacking.

Driver/Coach/Wrench : Innovative Performance/Exprit
Owner : Oktane Visual - www.oktanevisual.com
www.facebook.com/oktanevisual
www.instagram.com/oktanevisual

[Walt Gifford]

TJ, I can tune at the shop because I always have too much rear weight, vertical CG, rear grip and snap over steer so I set every up to counter that problem. Big guys don’t belong in karts but it’s too much fun to stop.

How does raising or lowering the front ride height effect weight jacking? I can see where it effects weight balance by tilting the drivers weight.

Gif

FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience

[TJ Koyen]

I’m not sure how else to word it to explain it… But here it is in J3’s words:

“Raising the front ride height: This is accomplished by placing washers from the bottom of the stub axle and placing them on top of the stub axle. This has a positive effect on the entire chassis when the grip levels increase and the chassis begins to understeer. Essentially the front ride height has been increased so, when the steering wheel is turned the inside tire is pushed/forced further into the track thus giving the driver a more positive feel (Front-Grip) and it will result in a better handling chassis.”

Driver/Coach/Wrench : Innovative Performance/Exprit
Owner : Oktane Visual - www.oktanevisual.com
www.facebook.com/oktanevisual
www.instagram.com/oktanevisual

[Bill Craven]

Walt… the manual you are referring to for the Margay… is it available on line somewhere?

[Walt Gifford]

IDK I couldn’t find it. I’ve got the hard copy that came with the kart. Might be able to get Margay to email it.

Gif

FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience

[Dan Brown]

Bill, I have one on my computer, I think Greg Dingess at Margay emailed it to me. If you want me to email it to you send me a pm with the address you want it sent to.

Dan

[Gary Lawson]

I respectfully disagree with any notion that a ride height changes has any effect on mechanical jacking or how the tire pushes into the track. Ride height changes actually do alter your caster setting, although it is minute and ultimately insignificant in comparison to the change in location of the center of gravity. Raising the frame on the front moves the center of gravity further back resulting in more rear grip. The arrow chassis guide explains this topic and many others very well. I tested ride height changes a while back when I was still running margays and my findings were identical to what the arrow manual states. A higher front was a little lazy on turn in but has more grip from apex to exit. The lower front turned in quicker but head less turning power on exit. I liked the front lower on the margay.

[Author]

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