Member Since: 03 Feb 2019
Location: Toronto
Posts: 133
stupid IID question
in the car config, there is set 'tire radius' which is in mm
What is this? is this measurement from the centre of the wheel hub to the edge of the tread?
Cant find mention of it in the docs
18th Aug 2023 2:12 pm
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10742
Silly maths question
No, it's the radius
The outside round bit, if you were to measure the round bit, with a bit of string
18th Aug 2023 2:25 pm
RATA1
Member Since: 27 Feb 2020
Location: Somerset
Posts: 353
??
Measuring the outside 'bit with string' would be the circumference.
Radius is centre to outside point of a circle or tyre. You can work that out without string.
Click image to enlarge
In today's world, if you contribute something, you don't contribute enough. If you contribute nothing, you receive everything.
2014 Discovery XXV
1961 Series 2
18th Aug 2023 2:40 pm
Endeavour
Member Since: 03 Feb 2019
Location: Toronto
Posts: 133
I'm going to sound thick here, but isnt that the circumference?
18th Aug 2023 2:40 pm
Endeavour
Member Since: 03 Feb 2019
Location: Toronto
Posts: 133
beat me to it
so I was right originally? its centre of the wheelhub to outside tread edge?
18th Aug 2023 2:42 pm
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10742
I’ll get my coat
18th Aug 2023 2:59 pm
RATA1
Member Since: 27 Feb 2020
Location: Somerset
Posts: 353
Mathematically yes. In the IID tool I would hope so too - depends what the number IID is showing you.
My rolling circumference in my CCF print is 2330mm with 255/50 20 fitted. There is also a rolling radius which is 115. A radius of 115mm??
I guess the 2330mm comes from a 20inch diameter wheel (508mm) with a tyre profile of 255mm-50% (127.5mm) fitted averaged 115 due to wear?
2 x pi x (127.5mm + 254mm) = 2398mm - maybe a new tyre
2 x pi x (115mm + 254mm) = 2318mm - maybe a worn tyre
C = 2 x pi x (y + 254)
2330/(2 x pi) = y - 254
(2330 / (2 x pi)) - 254 = y
y = 116.83
No idea and my best guess. Maybe it helps?In today's world, if you contribute something, you don't contribute enough. If you contribute nothing, you receive everything.
2014 Discovery XXV
1961 Series 2
18th Aug 2023 3:00 pm
gazjacko
Member Since: 14 Jan 2012
Location: Portsmouth-ish
Posts: 233
Warning warning! Curved ball incoming!!!
So who accounts for the ‘flat’ bit at the bottom of the tyre when it’s on the vehicle and the weight of the car deforms the tyre?
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