11-02-2014, 03:11 PM
Join Date: Jun 2013
Location: Oahu, Hawaii
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Originally Posted by FAChassis
Tire mount and balance procedure should be carefully performed. Recommend Hunter GSP9700 which can measure road force variation. Assembly variation should be 21 lbs (93 N) or less. A proper match mount can take several iterations, even left to right swaps between wheels and tires if target is not achievable. A really low road force tire may be tough to match to a wheel that isn't also low runout. So high-to-high or low-to-low is the right approach.
Tire flat spotting can be a very large contributor to veh vibration, and it can be permanent. For vehicles sitting longer than 2 weeks we recommend 45 psi for storage. Also helps to move vehicle a few meters every week or so. Karma doesn't like to sit still anyway so drive it often.
For new tires bead seating is a large contributor. Match mounting procedure with Hunter GSP9700, at low inflation pressure ~20 psi can help. Then inflate to placard pressure, then drive for 50 miles. If vibration is still present, try a very careful dynamic balance with inner/outer weight adjustment only (do not remove tire from wheel at this step). Check differences in balance weights. Improper bead seat can contribute 25-30g imblanace which is enough to feel in steering wheel, possibly seat track.
At Valmet the assemblies used Ahcon Matchmatic to 'crunch' the bead into the seat, 2 min cycle at 20 psi at ~500 kg. Some European tire dealers may have access to this. Not recommended to drive vehicle in this condition, machine only. But it can 100% resolve bead seating problems and resulting imbalance.
Damaged wheel can be a common cause too.
Vehicle cross caster is important sensitivity vs tire imbalance for steering wheel vibration.
Beyond this only half shafts and wheel bearings contribute to vibration, very uncommon.
Are these still the best specs to use?
Last edited by Roberta'sKarma; 11-02-2014 at 03:16 PM.
Reason: attachment added