[kpzen]

Zakaaaass!!!

Although your tyres are not uni directional...check if the thread pattern lines of front n rear tyres are fllowing in same directions ...I had similar issues in my zen got the tyre flipped on the same rim the problem was solved....

[zakaaaaasss]

i'll check it out prajesh.

one thing i forgot to mention earlier. before i did the rotation + balancing last month, the car used to swirl only at speeds say 70-85; but now it does even at lesser speeds.

[kpzen]

Originally Posted by zakaaaaasss

i'll check it out prajesh.

one thing i forgot to mention earlier. before i did the rotation + balancing last month, the car used to swirl only at speeds say 70-85; but now it does even at lesser speeds.

What exactly do u mean by swirling ?

Is it that the steering vibrates while driving or the car shift its track on an even surface when the steering is pointed straight.....???

[zakaaaaasss]

yes it somewhat the second part or ur statement however not on even but uneven roads.

i know what me means by 'swirling'...at certain speed say 80s when u drive over little rough patch or say over the uplifted zebra markings or on a concrete road with little gravel/tar spots over it, the car tends to move haywards even when the sterring is still and hold firmly....

this is what we ( me and revhappy) meant by swirling

[rks]

@zakaaaaasss, The stock wheel for Matiz is 4.5J with offset=45 mm. Your alloy wheel is 5.5J with 36 mm offset, so looks like the offset is within bounds.

You have fit 145/70 R13 tyres (presumably stock size?) on 5.5 J alloys. If you look at the carbibles web site,

Car Bibles : The Wheel and Tyre Bible

you will see the following passage:

A rim that is too narrow in relation to the tyre width will allow the tyre to distort excessively sideways under fast cornering. On the other hand, unduly wide rims on an ordinary car tend to give rather a harsh ride because the sidewalls have not got enough curvature to make them flex over bumps and potholes. That's why there is a range of rim sizes for each tyre size in my Rimwidthulator above.

As per the rim width calculator given in that site, 5.5J is the maximum rim width allowed for 145 mm tyres. With the 32 mm tyre pressure that you are maintaining, your ride over bumps and potholes will probably be harsh. One possibility is for you to try reducing tyre pressure to, say, 30 psi and see if your ride improves on bumpy/potholed roads. You can afford to run lower pressures with the wide rims that you have. I am assuming that you have no problems on good roads; you should get very good handling with the wide rims.

Or else you could go for wider 155 mm width tyres, properly chosen as per the tyre size calculator; this should improve your ride on bad roads. Make sure that your tyre pressures are accurately set and when the tyres are cold. This is a frequent problem, since petrol bunks are very unreliable and your tyres are often hot when you reach bunks.

Secondly you mention that you did rotation+balancing. What about alignment? Your car has already done 7K as per your post, so you should check alignment as well whenever you rotate your tyres and balance your wheels. The alignment/balancing should be done in a good tyre shop with proper equipment. I am told that if the wheel juts out, alignment needs to be checked taking this into account. So go to knowledgable people in a good tyre shop. Do you have any uneven tread wear in your tyres (i.e., is there more wear on one side or at certain spots)? If so that could be a sign of misalignment.

[revhappy]

Thanks a lot RKS,
1st thing I will do is maintain air pressure of 28 in front and 26 at the back becos no one sits at the back, I hope that should stiffen up the steering a lil bit. I think in my case the swirling was linked with the extra smooth power steering, and hopefully reduced air pressure should solve the problem. I will keep you guys posted.

Cheers,
Revhappy.

[mtnrajdeep]

Originally Posted by kpzen

The recommended air pressure for zen with 145/80-12 is 24 psi...why are u running with such high psi??? Your ride quality must be hard n steering should be extra light at the moment with 30psi

The recommended tyre pressure for zens with 12" wheels is 28 psi and for 13" wheels is 30 psi

[rks]

Originally Posted by mtnrajdeep

The recommended tyre pressure for zens with 12" wheels is 28 psi and for 13" wheels is 30 psi

In that case I think it is advisable for Revhappy to try 28 psi. Zakaaaaasss can go below manufacturer's recommendation of 32 psi, maybe 30 or even 28 psi, because he has wider rims (in fact the maximum permissible width of 5.5J for his 145 mm tyres; usually recommended for good roads, but not advisable in India). Personally I would try to live with the rough ride on bad roads/ get used to the light steering if a 2 psi reduction does not work. Or else go for tyre upgrade. I am reluctant to reduce tyre pressures too much, especially for the highway.

[rks]

Originally Posted by rks

In that case I think it is advisable for Revhappy to try 28 psi. Zakaaaaasss can go below manufacturer's recommendation of 32 psi, maybe 30 or even 28 psi, because he has wider rims

Actually even Revhappy has wider rims (4.5J alloys versus 4J stock). So Revhappy too can go down below manufacturer's recommendation. My suggestions are:

Revhappy -----------26 psi (but not lower) for city driving/bad roads.

Zakaaaaasss --------28 psi (but not lower) for city driving/bad roads


For speeding on good roads, I would suggest to up the pressure by 2 psi for Revhappy and 4 psi for Zakaaaaasss. If this doesn't solve the problem, I would either live with it or go for tyre upgrade.

Let us also keep in mind that lower offset can affect steering response, especially on bad roads. Even though my personal experience with 20 mm lower offset in my Santro has been good, other cars may not be as tolerant.

[kpzen]

Originally Posted by mtnrajdeep

The recommended tyre pressure for zens with 12" wheels is 28 psi and for 13" wheels is 30 psi

Come on.!! I cant get this wrong in case of zen at least

[rks]

Originally Posted by kpzen

Come on.!! I cant get this wrong in case of zen at least

You are right. Revhappy could go down to 24 psi, but hopefully his problem will be solved with the 26 psi that I suggested.

[revhappy]

Hello Guys,
I reduced the Pressure to 28 psi and and now the steering firms up very well even at 40 kmph. Actually the earlier pressure which was 30 had become 35, I guess becos of tyre heating as I had driven some 15kms b4 checking the pressure. so the difference b/w cold pressure and hot pressure is 5 psi !!!. I was surprised by this also the wheels had become very hot. So when I changed to 28 the cold pressure mite be 23 I guess. I need to check the pressure before a long journey next time.
Anyways, Thanks a lot guys. Becos of this forum I am learning a lot about my car otherwise everything would be such big mystery.

Cheers,
Nitin

[elf]

I would suggest to all to keep whatever pressures make you happy, but fill your tyres with dry nitrogen instead. There's a thread on this forum discussing that in detail.

The reason I suggest this is that the rate of expansion of dry nitrogen is even & results in a cooler running tyre.

Normal air, primarily due to the presence of water vapour, has different rates of expansion & varying coefficients of friction with the other elements present in it's composition.

In short - run dry nitrogen in your tyres. It's better.