[Samurai]

I guess we all know the compromises we have to make between handling and ride comfort while choosing to upgrade the tyres.

I have always wondered what really affects the ride comfort. Let's take a tyre like 175/70 R13 and change it. I know that the same rim may not accomodate modifying only one parameter at cer par, still kindly humour me.

1) Change only the aspect ratio.
175/70 R13 => 175/60 R 13

Handling should improve since the profile is lowered. What is the affect on ride comfort and why?

2) Change only the tyre width.
175/70 R13 => 185/70 R 13

Handling should improve since there is more rubber on the road. What is the affect on ride comfort and why?

3) Change only the wheel diameter.
175/70 R13 => 175/70 R 14

I don't really understand the affect of changing the wheel size alone on either handling or ride comfort. I know higher wheel size helps fitting lower profile tyres to a given rim, but how does it affect the handling and ride?

[Harrie]

Aspect ratio is width of the side wall expressed as a percentage of the tire width.

60 means side wall height is 0.6 times the tire width.

If the side wall height is more, it will flex and absorb the shocks and give better ride. But it also flexes under hard cornering thereby affecting handling.

Now coming to cases,

all of the cases whatever yuo have mentioned hold true. The only OTHER difference will be that the rolling diameter will be different.

[Shan2nu]

1) Change only the aspect ratio.
175/70 R13 => 175/60 R 13

Handling should improve since the profile is lowered. What is the affect on ride comfort and why?

Since you've reduce the side profile without changing the tyre width, the overall circumference will reduce. The lower profile will reduce the flexing of the sidewalls making the tyre hold on under hard cornering, giving you better traction at all times.

Since the circumference and diameter is reduced, the tyre will no longer be able to ride over potholes the way it used to.

2) Change only the tyre width.
175/70 R13 => 185/70 R 13

Handling should improve since there is more rubber on the road. What is the affect on ride comfort and why?

Since you've increased the tyre width without changing the profile, the circumference and diameter of the tyre will increase. This will reduce ride comfort but your handling will improve.

3) Change only the wheel diameter.
175/70 R13 => 175/70 R 14

This is the same as case 2, instead of increasing the side profile you've increased the wheel size but, since the profile is 70% of 175 (inlike 70% of 185 in case 2) ride comfort will be a bit less than in case 2 but the handling will improve.

Shan2nu

[speedsatya]

also the right air pressure is very important depending on the load.
cannot comment on other cars,but when i had 145/80r12 ,maruti recommended 24psi was okay when its only the driver ,but with 4 on board i foaund 26-27psi was better.but 26psi with only one person did harden the ride .

same with 145/70r13 on previous zens.maruti says 30psi.but thats okay when its fully loaded,but when u r alone,28psi was good.

now with 155/65r13,the handling was pathetic with 5.5j rims.butwith change in rims to 5j ,things have improved .also keeping 28-31psi depending on loads.

i felt teh wider 5.5 j rim made my tire wall look smaller than the 65 profile.


so i feel ,along with air pressure,the rims that u use to fit the tires is also important in deciding teh ride.

[Samurai]

Actually I am interested in the WHY. The case 1 has been explained by both Harrie and Shan2nu. Why does ride comfort decrease in case 2 and 3.

[speedsatya]

in 185/70r13,the tire wall is 70%of 185 whereas in 175/70r13 the tire wall be be lesser.so the OD in 185/70 will be more .so i dont agree that ride comfort will decrease.actually theoretically,as the tirewall has greater ht.,the ride should improve along with handling due to the wider tire.but ur speedo reading will be toatally wrong.

[amitoj]

Also point to note in case 2 is that it can affect your turning also. Since the tire width is increased as well as the sidewall height.
But i would like to add another somewhat related question to your original set of questions. What effect does changing the tire specs have on the car's suspension?

Cheers
Amitoj
PS: Satya, wot a signature, u dawg!

[Rtech]

2) Change only the tyre width.
175/70 R13 => 185/70 R 13

Handling should improve since there is more rubber on the road. What is the affect on ride comfort and why?
Since you've increased the tyre width without changing the profile, the circumference and diameter of the tyre will increase. This will reduce ride comfort but your handling will improve.

The ride comfort would not be reduced here. Infact, you are actually increase the the height of your sidewall, so in effect you should get a more compliant ride, but the handling would not improve.

In case 3 again, your ride comfort would ideally not decrease because your sidewall height remains the same hence giving you the same level of bump absorbtion. Infact, a larger wheel would give you a slightly better ride quality as it can handle larger potholes better than a smaller wheel. Your handling would also improve.

[Harrie]

ok in case 2 what happens is that you have a wider rubber to be fit on to the same rims. but we want the profile ratio to be same (70)

so what happens is the side wall in first is 175*0.7 but in second it is 185*0.7

clearly 185*0.7 means a bigger sidewall height

so the 185/70 will have better ride quality but the rolling diameter will be more.

[Samurai]

I see there was a mistake in my initial questions. I can't have a cet par assumption when one parameter is a function of other. i.e. AspectRatio is a function of TyreWidth.

AspectRatio = f(TyreWidth)

Therefore let me modify the question. Let's not worry about the numbers because they are actually confusing us.

How do the following modifictions affect the ride comfort and handling, and more importantly why?

Case 1) Narrower sidewall

Ans) Handling improves since the sidewall will flex to a lesser extent during turns. The ride comfort will suffer since it can't absorb bumps that well.

Case 2) Wider rubber

Ans) Better grip on on the road due to larger contact area, hopefully increases handling. What is the affect on ride comfort and more importantly why?

Case 3) Larger wheel (Not to be confused with larger tyre. It is possible to move to larger wheel and end up with smaller tyre)

Ans) Don't know.

Case 4) Larger tyre

Ans) Larger tyre would improve ride comfort since it can handle potholes better than smaller tyre. I am not sure about the affect on handling.

I am trying to understand these fundamentals so that I can make better judgement while choosing tyres and wheels in the future.

[Rtech]

Case 1) Narrower sidewall

Ans) Handling improves since the sidewall will flex to a lesser extent during turns. The ride comfort will suffer since it can't absorb bumps that well.

Well, the correct term would be lower sidewall. And yes, the result you have given is correct.

Case 2) Wider rubber

Ans) Better grip on on the road due to larger contact area, hopefully increases handling. What is the affect on ride comfort and more importantly why?

Better grip yes, but also increased steering effort. This would be less noticble on cars with power steering. Technically, increasing this one parameter alone would make your ride a bit better and you have a larger surface area to deal with bumps, hence spreading the force. So, at best it may make your ride a bit better, or else no change to it. Handling/braking would improve.

Case 3) Larger wheel (Not to be confused with larger tyre. It is possible to move to larger wheel and end up with smaller tyre)

Ans) Don't know.

Firstly, if you upsize your wheel, you have to upsize your tyre. If you mean the tyre width and profile remain the same (which I think you do), then your handling would improve and you should have a more stable car that can ride the bad roads better.

To take an extreme, consider the ride quality of a scooter which has 10" rims to that of a bike which has 17-18" rims.

Case 4) Larger tyre

Ans) Larger tyre would improve ride comfort since it can handle potholes better than smaller tyre. I am not sure about the affect on handling.

Again, what do you mean here when you say larger tyre? Larger as in 14" to 15" only or larger as in upsize in every aspect including width and profile?

Width/profile same & increase in diameter: same as case 3.
Width same and profile + dia. increase: more compliant ride but handling may be a bit worse
profile same & width+dia increase: ride should be a bit better.

Frankly, there are too many variables to consider and simply taking one aspect individually is not realistic. Air pressure, suspension of that car, type of road surface, everything plays its part and there is no such thing as the ideal wheel/tyre combination.

[Samurai]

Originally Posted by Rtech

Frankly, there are too many variables to consider and simply taking one aspect individually is not realistic. Air pressure, suspension of that car, type of road surface, everything plays its part and there is no such thing as the ideal wheel/tyre combination.

Exactly, so how do we understand the effect of upgrading the tyres/wheel.

I think the first two cases are understood now. Let's narrow down on the tyre/wheel size. In order to understand the effect of change in one parameter, one has to assume that everything else remains same or cet par.

Everything remains the same, only the tyres are bigger. Ride comfort improves. How does it affect the handling? and why?

[speedsatya]

also using the same tire on different rims,will change the handling considerably.

for eg.
if we take 145/70r13 ,even though it can be fitted on 4j,4.5j ,5j and even 5.5j the tire wall will be of maximum ht in a 4j rim and will be slightly lesser in a 5.5j rim.
but the contact patch with the road will be less in 5.5j as its wider ,while it will be lesser in 4j rim.

so the same tire will have bigger side wall in a narrower rim.so that means it will give better comfort in a narrower rim.
but that does not mean that it will handle best in a wider rim.
as my 155/65r13 handles better in a 5j rim as compared to a 5.5j rim.

[Harrie]

hey samurai look at it this way. If you are upgrading the tyre, then the overall diameter must remain the same.

Also decide the wheel size 13" or 14"

now you have only two variables, the tyre width and profile. But still they are also constrained by the overall diameter. So you can vary the tire width and profile ratio and get one that you would like.

overall dia = (wheel radius*2) + (sidewall height *2)

mind it wheel radius will be in inches while tire width will be in mm

[speedsatya]

you can get more info about tires ,Od and .... from this site.

you can put data about ur existing tires and get info about the correct upsize.

http://<b>http://www.chris-longhurst...bible.html</b>