Hi all, had a great run on the weekend and kart was super smooth with zero vibration until I hit a left corner kerb with my left front wheel at considerable speed then noticed a vibration through the steering wheel for the rest of that run (was last run of the day - 4 laps to go).
I've spun the wheel and it shows no signs of a buckle at all, tyre spins pretty well - maybe a very slight wobble but not major.
Has anyone else had a similar experience after running up a kerb? And what did you find fixed it? I'm kind just hoping the tyre took a mishape after the bump as theres no visible sign of a buckle or wobble.
I'm trying to figure out whether to try balance the wheel and see if that fixes it or just buy a new wheel (new wheel pair is 250 aud :( ).
Wheel is magnesium DWT M series non vented.
Any input would be greatly appreciated!!
Comments4
The stub axle might be bent.
e on February 19, 2018 at 19:49
The rear axle is probably bent!
Its a sad fact that where the front wheels go, the rear wheels usually follow :-)
Most likely a rear axel as these are easily bent on a kerb, and as said above, if the front has hit a kerb, the rear being wider and with more weight on it usually also takes a hit.
Before you go and buy a new pair of wheels, see if you can borrow a known good pair to test. I am sure someone will loan you some or run yours on their kart for a couple of laps.
Also look and see that the bearings and tie rods are in good condition and that they don't have any play in them as this can sometime amplify a very small viabration in the front end.
A slight wobble in a wheel is not uncommon, but doesn't usually cause significant vibration (though it may depend on the definition of 'slight'). Assuming the wheel is at least reasonably straight (i.e. not very bent), a vibration coming through the steering, rather then more generally in the chassis, I would tend to associate with a front wheel (tyre) being out of balance, i.e. needing some balance weight to be fitted at the rim.
An out of balance rear axle (i.e. any rotational component mounted on the axle) doesn't usually cause a 'feelable' vibration. Of course a bent rear axle will create some out of balance force, which in itself could cause a feelable vibration if bad enough, but more likely the resulting 'throwout' at one of the rear wheels will cause the rear of the chassis to rise and fall each time the axle / wheel rotates, causing a 'physical' vibration (as opposed to a 'dynamic' out of balance vibration, though both may be contributing to what is felt). It's not just rear axles that bend easily, rear wheels do too (because the outer edge of the rim is so hugely offset from the wheel hub, so any impact has a lot of leverage on the wheel centre).
Try this; take an electric drill with a rubber disc attached (backing disc for paper sanding disc). With the kart on the workstand hold the disc edge against the front tyre tread and spin the suspect wheel wheel up to speed. Does it vibrate?
I would have thought that a rear axle bend great enough to cause a substantial vibration would be easily visible when the axle is spun by hand. The rear axle can be spun up and checked for balance in much the same way as a front wheel (take the chain off). But don't be surprised if the whole kart does vibrate because of out of balance components, i.e. wheels/ tyres and, brake disc (not so much sprocket and its' carrier as they are not really heavy enough, but maybe).
I use this method to balance rear axle components (and correct wheel / tyre balance with stick on weights, brake rotor with weights added at the carrier bolts). Add each component to the axle one at a time and check it for balance. It can be quite surprising how much vibration can occur with the axle spinning fast with the kart on the stand, and yet can't be felt on track.
Out of balance wheels etc probably don't sap much power, but they must sap at least some because it takes energy to create a vibration, and if energy is being 'used' to create a vibration then it isn't being used to accelerate the kart. Balancing rear axle assemblies to correct imbalance that is too slight to actually feel on track may not make the kart faster, but it might, just a little bit...
Front wheel imbalance is easily felt because the front wheels are 'steerable'. The out of balance forces act not only radially, but also axially, i.e. the force pushes and pulls on the tie rods and directly pass force into the steering. This is not the case with the rear axle assembly because the axle is axially constrained, so only radial force is imparted into the chassis.
Regards,
John.