What's at Fault Here? Is it the Tyre / Rim or Something Else?


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I own a 2009 Corolla Altis. I put new Michelin Primacy 3 ST OE size tyres (195/65r15) few years back on stock rims (15 x 6j - offset 39). In February this year i changed my alloys wheels to Momo Hyperstar Evo (15 x 6.5j - offset 35). The alloys not only looked great but also made my daily driving on bad uneven potholed roads so much better. I was wondering why and only then i came to notice the difference in rim width of 1/2 inch (6j vs 6.5j).

I was driving with a cold tire pressure of 32psi on all tires. Everything was fine for 4 months when the weather was really hot. Not a single drop of rain. Couple of months back, the car hit a small speed breaker probably around 30 kmph and slowed to a halt immediately. There were no issues but I kept checking the struts for any oil leak but didnt find any. After a week or so, i noticed a deterioration in ride quality especially on uneven roads near my home. Even then, on warmer days, after being in the sun for 30 min or so, the car ran fine. It was in the evenings that the problem showed up. I thought that the strut might have lost gas as a result of the impact on the speed breaker. I tried increasing the tyre pressure by 1 psi to 33 psi and it ran fine in the morning. But, in the evenings it was completely different. The steering became a bit stiff and the car wobbled on uneven roads and dipped more on potholes. On flat roads it was fine. I felt a thud sometimes from the back of the car as if the trunk is open and hitting the bumper. I suspected the rear shocks were bad since they had never been replaced before and their damping was really bad.

My OE shocks are made by Gabriel in India. I thought there were a bit too much on the softer side and it shows on the really bad roads in our area. I also heard bad reviews about them and always wanted to put KYB shocks on my car. My mechanic said he never recommends Gabriel to anyone. He said trw and monroe are way better than Gabriel.

Its difficult to get KYBs here in India and even if its available I was not so sure about its authenticity. I checked the import data for KYB shocks for altis and the import price was around Rs.600! They were imported from Thailand.

I decided to go with TRW and replaced all four struts as well as the stabilizer links, front springs and bushings. When we replaced the rear struts, we found the old ones had gone really bad.

The result - it didnt solve the problem but the rear has a good strut now and the comfort on bad roads and handling have improved quite a bit but ONLY when its warm outside. Yesterday it was all fine when the temperature was around 32, especially after the car sat in the sun for half an hour. Today morning the problems showed up big time as the temperature was only 27!

It makes me think that my tires have really got hard and its getting even more hard as the temperature drops. This in turn puts the entire load on the shocks?? This is the conclusion I've come to. Its also difficult to think this way because my tires are only 3 years old and have close to 20k kms only. I did an alignment and rotated the tyres after installing the shocks. The front tyres have almost 6 mm tread and the rear close to 5 mm. New ones come with 8 mm.

Any clues on how to solve this headache would be greatly appreciated.

Thanks.
 
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I am not sure how weird the issue is, but to my guess, if tyre rotation at regular interval not done might be causing the problem.

Check below things,
- low arm
- suspension is leaking oil
 
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Gabriel is a number one brand. If the struts don't leak, you need not worry. The wobbling issue is mainly caused at the front end of the car, if there is a problem with the rear suspension, the car would fishtail on breaking.

jack the front of the car, put your hands at 3 and 9'o clock postion, there should be minimal to no shake. Some cars shake a bit. If you notice excess shake, steering ends are the culprit.

put your hands on the 12 and 6'o clock postion, if there is shake it has to be the control arm/ball joints. In some cars, ball joint and control are one piece and in some it's two parts.

also check the Shim and sway bar and the suspension bushing,

a wheel aligment shop should be able to find the cause
 

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