Member Since: 15 Oct 2020
Location: Wokingham
Posts: 412
I've just fitted some new wheels & tyres ...
I've gone from the original 255/50R20 to 265/65R18.
I've seen various posts about updating the CCF with the new size but is it necessary?
I've not changed it at the moment and whereas the speed was always about 3mph off compared to GPS (on a straight, level road) it now appears to be absolutely dead on.
Other than the speed is anything else affected by the tyre size in the CCF?
12th Nov 2022 5:46 pm
LeighW D3 Decade
Member Since: 31 Jan 2006
Location: Brisbane, AUS
Posts: 920
Some time ago I did a spreadsheet to compare original with proposed tyre size changes.
I plugged your figures in and here is the result.
Click image to enlarge
Hope this helps.LeighW
The old girl is on her third engine...
* first ran a bearing (design failure in original engine)
* second had a failure of the water outlet on top of the engine (pls check yours)
13th Nov 2022 1:24 am
kajtzu
Member Since: 10 Aug 2017
Location: Helsinki
Posts: 6771
I approve the use of excel
If one wouldn’t want to reinvent the wheel, https://tiresize.com/calculator/ allows similar comparisons between two different sizes.
13th Nov 2022 9:39 am
Moleshome
Member Since: 15 Oct 2020
Location: Wokingham
Posts: 412
Sorry, perhaps I haven't explained it very well.
I know how much larger the new wheels/tyres are but if anything the speedo is more accurate now even though I haven't changed the size in the CCF.
The question is whether I'll see any adverse effects elsewhere by leaving the setting as they are rather than 'correcting' them?
13th Nov 2022 6:21 pm
Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10740
Just leave it.
13th Nov 2022 6:31 pm
Moleshome
Member Since: 15 Oct 2020
Location: Wokingham
Posts: 412
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