Technical What do you all think about this post.

[rmjbn1]

On reflection, I think I'll throw my hat in the 'stick with 155 for now' ring.

OP clearly needs at least one tyre asap, with winter approaching.

I think I would:

• get a new pair of 155/80 R13s and stick them on the rear
• if the old rears (or, the best two old tyres) still have reasonable tread, swap them to the front
• get a recommendation for good local indy for four-wheel alignment (note: there is no provision for adjustment on the rear, but would be useful to know what's going on)
• continue to monitor tyre wear once you're reasonably sure the wheels are pointing in the right direction
• shelve the switch to wider tyres to a later date. Something's wrong and it would be best to try to fix it first.

 

[vexorg]

Bigger tyres always look better.
And as long as the offset is correct and nothing rubs then you should be good. General the larger tyres will handle better, we're not talking silly wide, 175/185 is small nowadays.

I know a few people that would fine tune the pressure based on their car. Every car is a bit different, and both edge wear is a sign of under inflation.

 

[koalar]

Let's start at the beginning

Original 155 rims have b profile rim it's illegal to fit a J profile tyre

 

[koalar]

Some tyre are dangerous regardless of tyre width, especially if they have gone old and hard

I had two cars on 155 and one on 165

They do feel different

The 155 is great in deep slush, the 165 is marginally better in the dry but at the cost of comfort

No have never had high or abnormal tyre wear, front or rear on either size

If changing tyres I'd stick closely to the original specifications

155 ET 41 5B
165 ET 38 5J
165 ET 38 5.5J
185 ET 32 5.5J
195 ET 30 6.5J

Which unfortunately would involve changing the rims also

Especially with all the sensors

Electronic Stability Control
Electric Power Steering

Not a great comparison but it's the only test I could find with identical tyre in three different widths on three different rim widths

In Search of the Fastest Tire and Wheel Width Combination

We test different tire and wheel combinations in this Tire Rack test.

www.tirerack.com

 

[vexorg]

The idea of the offset is so the the centre of the tyre sits in line with the hub, but I've seen like the above, where the offset differs on rims size, usually to keep the outer face of the tyre in roughly the sample place and not go beyond the wing.
The question is, what offset would be right for the tyre to sit central to the hub.

 

[koalar]

The idea of the offer is so the the centre of the tyre sits in line with the hub, but I've seen like the above, where the offset differs on rims size, usually to keep the outer face of the tyre in roughly the sample place and not go beyond the wing.
The question is, what offset would be right for the tyre to sit central to the hub.

I don't know

But nothings perfect play in bearing, ball joint, without a small induced load the straight line stability would suffer


195 - 155 = 40 / 2 = 20 mm difference
41 - 30 =. 9 mm difference

I make it the out edge alters by 11mm, or maybe my maths is wrong?

The scrub radius is also being altered the pivot point around which the tyre turns
After hours of computer modeling and track testing under various condition this is what Fiat chose
It's a compromise, wet, dry, economy, braking, hydroplaning, handling, comfort, one small driver, fully loaded, crosswinds, smooth roads, rough roads, driven carefully, driven hard and so on
That's how I see it right or wrong
Quality of tyres, age of tyre, tyre pressures make a huge difference
Wider tyres generally equal more rotational force, higher rolling resitance, more noise, but will also depend on brand,