A rolling circumference issue ..
My Jan 2010 T32 140ps LWB (panel van converted to Kombi, insulated, lined)
The label on driver pillar shows two 16 inch tyre sizes:
205/65/16 circ = 2114
215/65/16 circ = 2155
These have a circumference difference of about 2% (give or take all the maths rounding)
I have 205/65/16 fitted.
So for 18" alloys the closest matches for rolling c. are
205/65/16 matches 245/45/18
215/65/16 matches 255/45/18
For T32 everyone recommends 255/45/18, and it seems because these are 103 load rated, whereas the 245s are only 100/101.
This is what i find on a lot of the tyre seller sites.
My van is fitted with 205s, (load rated to 105/107) so to change to recommended size, 255, I have a 2% change to rolling circumference.
Speedo at 70 means I'm actually 71.5...
Or, cruise at 1500 revs to maintain same cruise speed revs will be 1470. (I like to rev low)
I am asking the insurer if I can fit 100 load rated to the T32, as I'm only SDP not a big load carrier.
This may give me more choice (confusion) even if there's not a big difference.
Is there any benefit of 245 vs 255 (e.g. less resistance, better mpg !) ?
In the real world will I notice anything different at all ?
Am I being too @[email protected] about this on figures ?
sarcasm is perfectly fine.
ps I set up the circumference calculator in a spreadsheet to check the rounding in on-line calculators. I like figures.
My Jan 2010 T32 140ps LWB (panel van converted to Kombi, insulated, lined)
The label on driver pillar shows two 16 inch tyre sizes:
205/65/16 circ = 2114
215/65/16 circ = 2155
These have a circumference difference of about 2% (give or take all the maths rounding)
I have 205/65/16 fitted.
So for 18" alloys the closest matches for rolling c. are
205/65/16 matches 245/45/18
215/65/16 matches 255/45/18
For T32 everyone recommends 255/45/18, and it seems because these are 103 load rated, whereas the 245s are only 100/101.
This is what i find on a lot of the tyre seller sites.
My van is fitted with 205s, (load rated to 105/107) so to change to recommended size, 255, I have a 2% change to rolling circumference.
Speedo at 70 means I'm actually 71.5...
Or, cruise at 1500 revs to maintain same cruise speed revs will be 1470. (I like to rev low)
I am asking the insurer if I can fit 100 load rated to the T32, as I'm only SDP not a big load carrier.
This may give me more choice (confusion) even if there's not a big difference.
Is there any benefit of 245 vs 255 (e.g. less resistance, better mpg !) ?
In the real world will I notice anything different at all ?
Am I being too @[email protected] about this on figures ?
sarcasm is perfectly fine.
ps I set up the circumference calculator in a spreadsheet to check the rounding in on-line calculators. I like figures.