Should all 4 tyres be replaced at once on AWD car?

[senator]

Buffering can't be done on street tyres, the compound is too hard, and a lot more heat is required to get the same result you would get from a track compound tyres…… there is no chance in hell any of the tyre manufactures will recommend this practice for street tyres.

[teK--]

I've just spoken to Bridgestone head office in SA. Very helpful guy I spoke to (Derek).

He explained that shaving street tyres is perfectly acceptable as long as the tyre is not shaved beyond the minimum treadwear indicators. Also the profile of the tread pattern must be maintained. I.e. do not shave it flat across width of tyre but rather follow the original curvature of the tread. With all these precautions taken there is no problem.

He went on to explain that as part of their Turanza product launch a few years ago they actually shaved the outer tread from their dual-layer tread compound, to show how well the tyre gripped down it was worn down to the secondary compound.

[senator]

[quote="teK--"]I've just spoken to Bridgestone head office in SA. Very helpful guy I spoke to (Derek).
quote]

Would you mind Pm'ing me Derek's details?

I work closely with many of the automotive manufactures and also tyres manufactures, buffering is a topic which is always argued, I am very surprised that a tyre manufacturing would be making those statements in relation to street tyres.

[marki]

The science behind it may be practical for motorsport, but were talking day to day driving, Its also very unsafe is general driving conditions, and unroadworthy australia wide.

What's unsafe about it? It's not as if the tyre is being shaved beyond the tread wear indicators.

I posted it as an alternative to getting 4 new tyres, if there is concern about meeting the 6mm circumference recommendation from Subaru. I have not heard of anyone going to these lengths in matching tyres though.

In any case, if the other 3 tyres are also worn within legal limits, then there is no safety issue at all in shaving the 4th tyre down to match. In fact it could be argued that safety is being improved by having 4 matched tyres.

Try to convince any copper there safe-- Unroadworthy any way you look at it.

[teK--]

Marki you've chosen one of the more extreme examples, but any copper worth their job would have a tread depth gauge.

Based on those photos 3mm center and 2.5mm shoulder is roadworthy as min limit is 1.6mm across full width.

Also it's funny that only last time you chose to publicly berate me for providing "misleading" information, but here you are blowing your trumpet that a tyre stated to be above wear indicators is "unroadworthy".

[marki]

Marki you've chosen one of the more extreme examples, but any copper worth their job would have a tread depth gauge.

Based on those photos 3mm center and 2.5mm shoulder is roadworthy as min limit is 1.6mm across full width.

Also it's funny that only last time you chose to publicly berate me for providing "misleading" information, but here you are blowing your trumpet that a tyre stated to be above wear indicators is "unroadworthy".

Its not an extreme example, Those photos are directly taken from the below website.
http://www.toyo.com.au/tech_info15.htm

Copper worth their job... the coppers not doing their job if they let you slide with them slicks -- UNROADWORTHY, your convincing no-one, again.

[teK--]

http://www.toyo.com.au/Proxes%20RA1.htm

"NOTE: The Proxes RA1 is legal for use on public roads in Australia but is designed for motor sport applications (including road rallies). Compared to street radials, Toyo motor sport tyres will have comparatively faster wear rates and increased ride harshness."

Above wear indicators = roadworthy. They are not "slicks" End of discussion.