Food for thought.

Gaijin · 26 Oct 2007 at 13:11

Jonny69 said:
Well done for holding onto it, looks like it went good and proper.

Tyres blow out for seemingly no reason. I doubt it was through any fault of yours, not unless it was completely flat or pumped up to 45psi.

Aye, can assure you it wasnt either

. Also, i'm not going to take the credit for being some awesome recovery specialist - most of that damage would have been caused not just due to the blowout, but driving on it at the speed I was at immediately after failure and furthermore the distance I had to go to the nearest layby.

Matt82 said:
as for variations in pressures i found a good demo, this is for the porsche 993 which had 16-17 and 18 inch wheels

Summer Tires
front 16" wheels 36 (2.5)
17" wheels 36 (2.5)
18" wheels 36 (2.5) turbo 36 (2.5)

rear 16" wheels 44 (3.0)
17" wheels 36 (2.5)
18" wheels 44 (3.0) turbo 44 (3.0)

so change widths, profile and diameter all need different pressures

Sorry mate - what are the figures in brackets? I take it the 36 and 44 are pressure in psi?

Scottland · 26 Oct 2007 at 13:22

Gaijin said:
Sorry mate - what are the figures in brackets? I take it the 36 and 44 are pressure in psi?

Bar pressures.

Glad you hung onto it, it seems its the season of tyre problems

Appelhanns · 26 Oct 2007 at 13:27

the bracket numbers is pressure in bar?

Matt82 · 26 Oct 2007 at 14:07

the pressure in BAR.....

hence, putting larger wheels on etc means the tyre pressures will need to change

Gaijin · 26 Oct 2007 at 14:22

Matt82 said:
the pressure in BAR.....

hence, putting larger wheels on etc means the tyre pressures will need to change

Hmmm but the fronts havent changed?

Was that porsche AWD or RWD?

Perhaps the the larger wheels were significantly more heavy/wide and required a different pressure?

Very difficult to speculate.

I've been reading through this:

http://www.carbibles.com/tyre_bible_pg2.html

I may have read it wrong, but it seems to suggest that if the weight and contact patch are the same before and after new wheels, then the pressure shouldnt change?

I guess what i'm trying to ascertain is what type of factors determine the tyre pressure?

Matt82 · 26 Oct 2007 at 14:45

good question. as an another example, see my post up there aobut mk3 golf tyre sizes and VW's recommended pressures. almost 10psi difference when changing to a 10mm narrower tyre.

someone will konw more about why pressures have to change. i just know they do and hence have not fitted larger wheels etc in the past as im not brave enough to put unknown pressures in there