Good job, TS.

If the Load Index of replacement tyre is the same as the stock/as-is tyre, then similar tyre pressure on both would carry the same load.

However I suspect a replacement R16 is likely to have a higher Load Index than a R15 stock tyre, hence a lower pressure (than stock) in replacement tyre would carry the same designed loads as the stock tyre at stock pressure.

Having said that there is no harm in maintaining similar tyre pressure in a replacement tyre with higher LI, but not vice versa.

Not knowing the Load Index of both of your stock and replacement tyres, I think you should be fine and safe.

My 2 sen is silica or sand in itself is highly abrasive in material property and hence tire compound with silica can withstand better/stronger from being 'worn down' by the highly abrasive asphalt/pre-mixed road surface .... thus increasing tyre longevity in particular during hard braking.

Besides, silica has a very high hardness property at the expense of brittleness property like a glass ..... easily gets cracked or scratch while preserving the 'mother material' of rubber tyre compound.

The cracks in a typically hardened tyre rubber in operational service over a period of time especially in a Michelin does not normally propagate to the next protective layer (right below the tread rubber compound), hence the structural integrity of hardened and used tyres are still intact offering maximum level of protection as designed or as intended.

Replacement of used tyres (after 3-5 years of usage) on believing it being hardened and/or observing (hairline) cracks on tread compound is imho unfounded and baseless as is commonly practised in lowyat/locally.

This post has been edited by zeng: Aug 13 2022, 11:44 AM

It is safe to continue its service as these hairline cracks are cosmetic and not structural/strength in nature, according to tyre manufacturers.

Cracks is related to hardening of rubber tyre compound with oxidation/sunlight as a catalysts.

I'm not aware tyre manufacturers recommend tyre replacement on the basis of socalled 'dry rot', whose meaning/definition is not spelled out clearly.
In a way, I don't consider the hairline cracks on this 2018 tyre as dry not , as the structural strength of the tyre is not compromised and is intact.

Patching of a 1 cm puncture in a normal radial ply tyre is NOT recommended by tyre manufacturers.

Maximum allowable by manufacturers is 0.6 cm though there are owners who got away with it without encountering any problem for punctures exceeding 0.6 cm.

As for run flats, IDK but I suspect the same rule of max allowable 0.6 cm may apply here. In this context patching of 1 cm puncture may not comply with manufacturers recommendation hence replacing the one punctured tyre may make sense whilst retaining the other three.

This post has been edited by zeng: Aug 30 2022, 01:29 PM

With tyre service being available at our disposal almost 24/7/365 within 50-100 km radius wherever we drives around (especially along west coast of peninsular) the idea of run flats sound stupid imho, let alone its less than appropriate performance , pricings etc.

Besides, tow truck service and Google search service is just a call/search away with a cheapo rm3xx new phone.

This post has been edited by zeng: Aug 30 2022, 06:03 PM

Replacing high profile 70R tyres with low profile 50R should rightly be 'promoting' tramlining experience and harsher ride.

At similar tyre pressures, it should help in firmer ride reducing/controlling body roll generally.

Having said that I'm not doubting your actual driving experience or perception, more so if an alignment job was carried out during rims changes as I'd a hunch that the problem is alignment related.

I defer to TS on small sidewall bulge felt by running fingers over it and associated warranty claim in local tyre industry.

This post has been edited by zeng: Sep 6 2022, 11:05 AM

The bold suggests that the rear alignment #s of this car is off. Bigger 15" rim size is just a camouflage imho.

In a typical Saga, the rear alignment is easily adjustable IIRC unlike rear torsion beam designs in Peroduas Vios, City etc.

This post has been edited by zeng: Sep 7 2022, 07:00 AM

Interesting to note that there are tolerances acceptable in bulge/indentations and its size externally and/or internally(?) by QC .

Care to elaborate more on the QC tolerances in question or better still, if there are online resource on said acceptable tolerances?

Thank you for clarifying a 'newer' saga vvt has rear torsion beam design, which has no factory adjustment for rear alignment angles.

Yes, older generation saga/wira used to have multi link rear suspension system.

Having selected a specific tyre model/material in real life, tyre alignment is more significant and appropriate in dealing with your intended purpose imho besides driving skills.

Thanks for the heads up.

You're right. A quick search shows 2008 and up Sagas are rear torsion beam design.

I owned 3 Sagas from 1985 to 1990, IIRC they were all rear multi links but not definite about it.

Any info on rear suspension designs of Sagas from 1991- 2007?

Early Wira's are definitely rear multi link design.

This post has been edited by zeng: Sep 10 2022, 11:23 PM

At similar air pressure, the load capacity of your R15 likely exceeds that tyre sizes on the sticker.

So, you'll never overload and safe.

The tyre alignment finishing car owners are getting in the market are very mediocre and cin cai imho, including those whose print out (which is rarely given to customers) have numbers within green zones.

I'm also in search of a 'perfectionist' alignment shop. Somebody here did suggest a xxx Hin along Jalan Klang Lama if you're in klang valley, which I'm yet to try him.

-delete-

This post has been edited by zeng: Sep 10 2022, 11:43 PM

Ohh.... Iswara is pre 2007.

By cun cun aligning the 4 wheels in a 'near-perfectionist' wheel alignment shop which is very hard to come by .

You hit right on the head of the nail, my friend.

This is the MINIMUM tyre pressure (at cold always) recommended by car manufacturers (not by tyre manufacturers) specific to the OE tyres AND vehicle models, with some assumptions.


That's how all tyres behaves ......
hence it's perfectly normal and has been well considered by car manufacturers AND tyre manufacturers in dishing out their respective 'recommendations'.

Recommended tyre pressures (at 220 kpa in this case) by manufacturers is always at COLD, of the day or seasons (for gwailos).

Kind of 'ignore' operating tyre pressures in a discussion on 'recommended tyre pressures' per se, for clarity of mind.

MAXIMUM recommended tyre pressure is ALWAYS embossed on the tyre sidewall as a requirement in the industry. It is typically 51 psi (350 kpa) for most or all passenger cars here.

Optimum is anything in between Minimum and Maximum, philosophically to suit varying application scenarios and individua preferences.

In my Avanza the Optimum tyre pressure (to me) is 5-10 psi HIGHER than Toyota recommendation.

True.
I prefer 'older' new tyre, not fresh tyre when new.
Unfortunately it is hard to come by in KL.

This post has been edited by zeng: Jan 25 2023, 08:27 AM