[sans33]

Hi,is it possible to fit 185/70/R13 on front and 165/80/R13 at rear on my Baleno Altura.Reason is,I have two good tyres with nearly 60% rubber but another two have less rubber and flat spots.Now I wish to upgrade to 185/70/13 but don't want to throw away two good tyres.

[Shan2nu]

Not safe at all. Psycho and Mclaren have expereinced this combo during the March 2006 track meet. From what i heard, it wasn't a good feeling.

Shan2nu

[iraghava]

It wouldn't work since you would have grip difference in both ends. In case of hard driving there could be unexpected behaviour from either end which could result in a crash. I would strictly advise against even trying such a thing.

In your case this would lead to sudden loss of grip at the back end & the car going into a spin which can have drastic consequences. I can tell you that because once I tried the same on my car (don't ask why) and on taking the first fast turn the rear promptly stepped out without any warning!

[Vid6639]

Just to add to what Iraghava said, if you try the other combo the fatter tyre at the rear, youll have loads of understeer. the front wont turn into a fast corner as the front grip will be substantially lesser.

Better not to try it.

[theMAG]

mclaren1885 is a master of fitting tyres of different sizes and living to explain abt it, wontcha mclaren?

[Rehaan]

Sans33,

If it were a difference of 185 and 175 with a very close overall diameter, and you didnt plan on pushing the car a lot, i would say it might be doable....
But in this case im not very sure what it will be like....

cya
R

[Shan2nu]

If it were a difference of 185 and 175 with a very close overall diameter, and you didnt plan on pushing the car a lot, i would say it might be doable....

Yup that will surely work. Even for track use, using a slightly broader (+10mm) front tyre reduces understeer. But diff of 20mm maynot be a good idea.

Shan2nu

[binz]

Yea rahul will know.-hes run everything from 14inch and 15inch on alternate sides.-eagle f1s and stock S248..195 14 on the front left and rear right..and 165 13 on the front right and rear left...hes crazy contact him!

[Rehaan]

Originally Posted by Shan2nu

Yup that will surely work. Even for track use, using a slightly broader (+10mm) front tyre reduces understeer. But diff of 20mm maynot be a good idea.

Shan2nu

Actually, now that i think about it, even if it was a 20mm difference, 185 and 205 for example, i would be ok with it...... however, i think the fact that in this case one pair is the skinny 165s is whats making me not like it!

(This is just my opinion ofcourse)

cya
R

[iraghava]

Originally Posted by Rehaan

Actually, now that i think about it, even if it was a 20mm difference, 185 and 205 for example, i would be ok with it...... however, i think the fact that in this case one pair is the skinny 165s is whats making me not like it!

(This is just my opinion ofcourse)

Ok Rehaan I didn't wanna state this in public but here is what happened with me.

I ran the worst tyres I ever bought (GoodYear Eagle F1 GSD2) and after 30k kms or so three of them had either burst or developed major sidewall bulges so I had to request my tyre dealer to give me 2 tyres to use as an intermediate measure before I could replace all my tyres. So he gave me 175/65 R14 Bridgestone S322's which were at the rear while my 185/60 Eagle's were at the front.

Now happily thinking that I was fine I drove on towards home & on the Expressway took the first sweeping turn at about 110-120kmph upon which the rear promptly started to move & stepped out which I somehow controlled. I tried it again a couple of times on different bends but the result was the same which led me to the conclusion that this was a bad idea & hence my advice to Sans.

P.S. Mine could have been a freak case though!

[Shan2nu]

Actually, now that i think about it, even if it was a 20mm difference, 185 and 205 for example, i would be ok with it...... however, i think the fact that in this case one pair is the skinny 165s is whats making me not like it!

That would depend on the degree of understeer the car faces while cornering. And it's not just the contact patch that changes, having a diff of 20mm means that you'l end up with a high profile rear tyre and a low profile front tyre.

Shan2nu

[Vid6639]

In turn also the front and rear track would change causing an uneven lateral acceleration.

This would mess up the balance and cause the oversteer.

[rks]

Originally Posted by iraghava

I ran the worst tyres I ever bought (GoodYear Eagle F1 GSD2) and after 30k kms or so three of them had either burst or developed major sidewall bulges so I had to request my tyre dealer to give me 2 tyres to use as an intermediate measure before I could replace all my tyres. So he gave me 175/65 R14 Bridgestone S322's which were at the rear while my 185/60 Eagle's were at the front.

I know you do very high speeds, of the order of 170+ kmph. It seems that the symptoms you mention, namely, tyre blowouts and sidewall bulges, are possibly indicative of low tyre pressures relative to these speeds. Another issue is the speed rating of the GoodYear Eagle F1 tyres -- was it high enough for your speeds? Of course, as you say, it could be that you ended up with bad tyres, maybe defective stock.

Now happily thinking that I was fine I drove on towards home & on the Expressway took the first sweeping turn at about 110-120kmph upon which the rear promptly started to move & stepped out which I somehow controlled. I tried it again a couple of times on different bends but the result was the same which led me to the conclusion that this was a bad idea & hence my advice to Sans.

P.S. Mine could have been a freak case though!

I agree with your advice. As per my Santro manual:

Replacement tyres must be of the recommended size and rating and should be of the same manufacturer and tread pattern on each axle.
...
CAUTION:
Tyres of different size, construction or tread pattern should not be intermixed on the same axle. Radial and crossply tyres should not be used on the same vehicle. The use of tyres and wheels of non approved sizes can be dangerous.

Interestingly, the manual seems to insist on sticking to even the manufacturer's recommended speed rating while changing tyres. Probably because changing the speed rating can also affect the car's handling.


The manual also insists that while changing wheels, the manufacturer's specifications for "rim section" and "rim offset" must be adhered to. I assume that the "rim section" here refers to the rim width (i.e, 4J for my Santro).

[iraghava]

Originally Posted by rks

I know you do very high speeds, of the order of 170+ kmph. It seems that the symptoms you mention, namely, tyre blowouts and sidewall bulges, are possibly indicative of low tyre pressures relative to these speeds. Another issue is the speed rating of the GoodYear Eagle F1 tyres -- was it high enough for your speeds? Of course, as you say, it could be that you ended up with bad tyres, maybe defective stock.

Well that could not be a reason because my set prior to the F1's (Bridgestone Potenza RE88 185/60 R14) & the set after (Michelin Energy XM1 185/65 R14) have not shown these problems when the usage conditions have remained more or less the same. The Bridgestone & F1's were run at the recommended tyre pressures whereas the Michelin's have been run at 28psi since I found running 30psi made the ride a lot more hard & bouncy.

As for the Speed rating of the F1's they were H or V rated which is comfortably more than my top speed.

Originally Posted by rks

I agree with your advice. As per my Santro manual:

Interestingly, the manual seems to insist on sticking to even the manufacturer's recommended speed rating while changing tyres. Probably because changing the speed rating can also affect the car's handling.

No changing the speed rating won't have an effect on handling but I think the warning is to avoid people from putting in lower speed rated tyres then recommended & having a high-speed blowout. Having a higher-speed rating than recommended does not have any side-effects.

Originally Posted by rks

The manual also insists that while changing wheels, the manufacturer's specifications for "rim section" and "rim offset" must be adhered to. I assume that the "rim section" here refers to the rim width (i.e, 4J for my Santro).

Yes, the rim section refers to the width.

[v1p3r]

Originally Posted by vid6639

In turn also the front and rear track would change causing an uneven lateral acceleration.

Even if the rear is just a dead axle?

Originally Posted by iraghava

As for the Speed rating of the F1's they were H or V rated which is comfortably more than my top speed.

AFAIK, and I could be wrong here (YOU are the tyre dealer!), the speed ratings are based on European road conditions, and the average road temperature is calculated to be around 30 degrees centigrade. In India, our temperatures are often double that. So I'd buy a tyre that was rated atleast two grades over my requirements.

I'd like to add that I have driven atleast 2 cars where the rears were skinnier than the fronts. And I often play with tyre pressures if a track is involved. It comes down to your personal driving style and preferences, and whether or not you can handle oversteer. I wouldn't advise people to try it on a daily basis, though.