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Old 4th March 2006, 16:54   #1
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Default Tyre Balance Qs - How come...???

Hey guys in my maruti 800 the steering wheel as well as the floor(by floor i mean the place where we keep our legs while driving)..was vibrating at any speeds above 100 km..edmund suggested that i get the ball joint checked..at an authorized service station..nd off i went to spectra motors today...the service adviser..sat in the car..nd pushed it till 100 km on the highway..nd he said that that balancing was out ..nd needed to be got done..he was good enough to tell me to get it done at some other place..rather than the maruti showroom as the rates were too high(80 bucks per wheel for balancing+weight) ..got alignmend nd balancing done at a place near my house..nd the result..no vibration even at 110...not much weights went into the rims though..
The thing i could not understand was:-
1)As much weight did not go in the rim..how come so much vibration(more on the floor..nd less on the steering wheel)..around 20 to 30 gms in the front rims..
2)Why was the floor vibrating in the first place..as in if the balancing is out..only the steering is supposed to vibrate..
3)The tyres are about 25000 km up..radial tyres..nd 2 of the tyres the tread is like 65% down..?..how come such early tyre wear? nd the other two have 50 % tread gone..(which is understandable)
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Old 6th March 2006, 00:16   #2
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Hi humyum,

Heres my take on it -

To put it simply, when your wheel spins at relatively high rpm any slight discrepancy in the weight, (ie a heavy spot somewhere along the rim/tyre) will cause the wheel to "bounce" (due to Newtons laws of motion).

In a simple sense, as the heavy spot is travelling upwards on the rotation, it causes a lifting force on the wheel/tyre and as it is travelling downwards on the rotation the imbalance in weight causes a greater downward force. (ofcourse these forces are compounded at higher revolutions which causes the imbalance to become noticable).

Quote:
Originally Posted by humyum
The thing i could not understand was:-
1)As much weight did not go in the rim..how come so much vibration(more on the floor..nd less on the steering wheel)..around 20 to 30 gms in the front rims..
2)Why was the floor vibrating in the first place..as in if the balancing is out..only the steering is supposed to vibrate..
3)The tyres are about 25000 km up..radial tyres..nd 2 of the tyres the tread is like 65% down..?..how come such early tyre wear? nd the other two have 50 % tread gone..(which is understandable)
1) 20-30gms(/wheel) is quite a lot of weight in terms of wheel balancing. Keep in mind the high rotational speeds the weight will be travelling at.

2) The reason your floor was shaking more than your steering probably is due to the fact that the imbalance in your wheel was more "up and down" in this case, hence not really moving your steering from side to side, and causing the bounce to be felt mostly on the floorpan near the wheel. (There are also two kinds of wheel balancing, static and dynamic; static basically takes care of only the up and down, and dynamic takes care of the side to side as well)

3) Tyre tread 65% down @25k-km. So that means they will be done at ~39k-km. And for the ones that are 50% gone, they will last till 50k-km! Thats a perfectly respectable treadlife for radials in my opinion.

As for the difference in treadwear (50%vs65%) keep in mind that the front tyres get worn out must faster than the rear tyres, due to the fact that they have to steer as well as do most of the braking (due to weight transfer to the front when breaking).
Also, RHS front tyre usually gets worn faster than the LHS one since (driving on the LHS of the road) in city conditions, on average we take (free) left turns faster than right turns (where you usually have to stop for a signal before taking the turn).

To solve the different rates of tyre wear, get your tyres rotated.
Search for "rotation" on the forum.

cya
R

Last edited by Rehaan : 6th March 2006 at 00:19.
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