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Old 24th August 2006, 16:23   #31
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Originally Posted by kpzen
Stock rims 14"
Stock tyres 165/80-14"

Got upsized tyres 185/70-14" on stock rims....
Can one upsize that much on stock rims??? Isnt that a bit too wide???
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Old 24th August 2006, 16:29   #32
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Can one upsize that much on stock rims??? Isnt that a bit too wide???
It's usually limited to 20mm over stock so 185 is fine.

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Old 24th August 2006, 16:43   #33
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One reason why i'd rule out low tyre pressure.

This was how "Morten" had described the tyre wear on his car.

"" the tyres go from the outside towards the inside and the whole tyre is gone and the steel wires come out from outside of the tyre. The strange thing is rear tyres also go the same way.the tyre pressure was always maintained to 29-30.the alignment and camber was always ok.i guess the car is defective but cant tell what is wrong.""

Using low tyre pressure should wear out both the inner and outer shoulders. But in this case, the wear starts from the outer shoulder and then moves inwards. This can only be caused due to positive camber or very hard cornering (like what we do on racet tracks).

This diagram will help understand what i'm talking about.

Positive and Negative Camber


As you can see, when a car has +ve camber, the outer shoulder of the tyre is taking most of the cars weight. This will also cause the contact path to reduce and make the tyre heatup and wear out faster than usual.

Shan2nu

Great explanation by a technical guru...

regards
KP

Last edited by kpzen : 24th August 2006 at 16:47.
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Old 24th August 2006, 17:00   #34
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I agree with Shan2nu's explanation. I has misread morton's description of the tyres wearing from "the outside to the inside" to mean "from the shoulders towards the centre". So I guess morton should clarify what he meant -- is there wear on both shoulders or on only one? The fact that this is happening on all four tyres suggests that there is a systematic error involved. So possibly checking the alignment (including camber) at two different ASC's might do the trick --it is unlikely that both of these would commit the same errors. If excess wear is happening on both shoulders of the tyres, low tyre pressure is probably the culprit.
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Old 24th August 2006, 17:51   #35
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Quote:
Originally Posted by Shan2nu
One reason why i'd rule out low tyre pressure.

This was how "Morten" had described the tyre wear on his car.

"" the tyres go from the outside towards the inside and the whole tyre is gone and the steel wires come out from outside of the tyre. The strange thing is rear tyres also go the same way.the tyre pressure was always maintained to 29-30.the alignment and camber was always ok.i guess the car is defective but cant tell what is wrong.""

Using low tyre pressure should wear out both the inner and outer shoulders. But in this case, the wear starts from the outer shoulder and then moves inwards. This can only be caused due to positive camber or very hard cornering (like what we do on racet tracks). [...]
Good explanation. I have one more issue here. If there is a misalignment due to positive camber, the outside shoulder of the tyre should wear out faster, but the inside shoulder of the tyre should show much less wear than normal -- because the inside shoulder is taking a lower load than normal. But from morten's description, "the whole tyre is gone" in as little as 8000 kms in one case and 13000 kms in the other. So my guess is that morton's description is not quite accurate -- he might have meant that all four tyres wear out from "the shoulders towards the centre", rather than from "the outside towards the inside". This would be consistent with "the whole tyre is gone" within such a low mileage. Also, as I said earlier, the fact that this is happening to all four tyres strongly suggests a systematic error that affects all four tyres in the same way. E.g. the tyre pressure readings could be way off due to a faulty gauge in the case of two-sided wear, or the same alignment mistake is happening at all four wheels due to faulty equipment (in the case of one-sided wear).

Last edited by rks : 24th August 2006 at 18:03.
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Old 24th August 2006, 17:57   #36
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So my guess is that morton's description is not quite accurate -- he might have meant that all four tyres wear out from "the shoulders towards the centre", rather than from "the outside towards the inside". This would be consistent with "the whole tyre is gone" within such a low mileage. Also, as I said earlier, the fact that this is happening to all four tyres strongly suggests a systematic error that affects all four tyres in the same way. E.g. the tyre pressure readings could be way off due to a faulty gauge in the case of two-sided wear, or the same alignment mistake is happening at all four wheels due to faulty equipment (in the case of one-sided wear).
Maybe, but my reply was based on how the wear was described. A few snaps of the worn out tyres would solve the whole mystery.

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Old 25th August 2006, 11:55   #37
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Quote:
Originally Posted by Shan2nu
Maybe, but my reply was based on how the wear was described. A few snaps of the worn out tyres would solve the whole mystery.
I agree. The more I think about this, the more convinced I am that there is something wrong with morten's description of the problem. He needs to check with his friend as to what exactly happened and post a detailed description with snaps before any analysis can be made.

It seems that the car (a Jan 2006 Swift) has already done an awful lot of running (at least 21000 kms) till date -- so it must have seen a lot of the highway. There is a very serious danger of a tyre burst if the car is driven at speed on the highway with this problem unsolved. I hope morten's friend has been adequately warned. With all the free services that the car must have gone through at an ASC, I cannot understand how the problem still remians unsolved.
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