PPP38vouge
Active Member
Hi, 16s or 18s are the correct sizes for the P38 but many do run on 19s as do I.
wil2813
Well-Known Member
Hi guys, firstly sorry for the late response it's been a bit work, home, work home. Thanks for the replies, it doesn't quite pin point the correct size. I've been having gear change problems as it is an automatic the chap at the gearbox specialist said I have to have the right size wheels on to start with then fix the other couple of issues it has. As it has a 18 inch in the boot I'm going to go with that. Thanks again for the info, Paul.
If you fit 19" wheels with 255/50/19 tyres they are within a few mm the same rolling radius as the 255/65/16 or 255/55/18 wheels and tyres fitted as standard equipment. Only thing a smaller than normal or larger than normal rolling radius will effect is the speedo reading. Smaller than normal rolling radius will give a reduction in gearbox ratios. Larger than normal rolling radius will give an increase in gearbox ratios. Other than that It will not in any way effect the actual gearbox operation.
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My beastie has mud pluggers on which, (I suspect), are not standard as my speedo is reading very low but this has no bearing on engine and/or gearbox performance, (other than the vehicle will may not be running within the designed/ideal rev range if the wheel size is wildly out).
I suspect that serious problems may occur, however, if you have a mismatch of sizes on any of the hubs!
Not wishing to hijack this topic but does anybody know the formula for calculating the speedo offset factor for different wheel sizes I wonder?
I suspect that serious problems may occur, however, if you have a mismatch of sizes on any of the hubs!
Not wishing to hijack this topic but does anybody know the formula for calculating the speedo offset factor for different wheel sizes I wonder?
ovalandrover
Well-Known Member
I will be putting 255 60 18 tyres on my P38 but the spare will not fit in the boot so i am also making up a swing away spare wheel carrier that will be able to fit on the towbar so easily removable.
the reason i am putting on higher aspect ratio tyres is that im hopeing to get fuel consumption and also beter protection for my rims as i have smashed 2 when travelling in Mongolia and Russia .
Also the spare wheel on the towbar will be easier to access when I am fully loaded and get puncture.
the reason i am putting on higher aspect ratio tyres is that im hopeing to get fuel consumption and also beter protection for my rims as i have smashed 2 when travelling in Mongolia and Russia .
Also the spare wheel on the towbar will be easier to access when I am fully loaded and get puncture.
Why do you not use standard 16"s?
Yes you can.
martyuk
Well-Known Member
Where's that setting? I presumed in the ABS module, but the WABCO 'D' in my Thor model doesn't have any options for speedo adjustment - you can force it on/off to test the output but that's about it. Not sure about the earlier WABCO 'C' models.
Haven't seen anything in the BECM settings either.
I always figured that you might be able to tweak it with one of the trimmer pots on the instrument cluster PCB, but have never had a chance to actually see what any of them do.
ovalandrover
Well-Known Member
because I have 14 18 inch rims
Nothing to do with Wabco look in instrument. Last screen.
No, you can't.
Tyre coefficient in nanocom is only for instruments mode display.
