Tyre Pressures 255/45/18
- Thread starter DaveF
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- 18” 255/45/18 tyre pressure
I think that list is only giving max allowed cold pressure, and some conversion done from bar to psi, and rounded, and later conversed back to bar, and again rounded. Speedcode given in place of the usual R of radial.
On other plate I saw 255/45 R XL 103.H
Is maxload 875 kg/ 1929 lbs AT 2.9 bar / 42 psi upto 160 kmph/ 99 mph.
Maxcold is then only given on sidewall between 3.0 bar / 44psi and 3.5 bar / 51 psi, and an ocacional XL 4.25 bar/ 60 psi.
Can make you a cold pressure/ axleloadcapacitylist, with build in maximum reserve, at wich comfort and gripp is still acceptable.
For that, I give 90% of calculated axleloadcapacity for max 160 kmph/ 99mph.
On other plate I saw 255/45 R XL 103.H
Is maxload 875 kg/ 1929 lbs AT 2.9 bar / 42 psi upto 160 kmph/ 99 mph.
Maxcold is then only given on sidewall between 3.0 bar / 44psi and 3.5 bar / 51 psi, and an ocacional XL 4.25 bar/ 60 psi.
Can make you a cold pressure/ axleloadcapacitylist, with build in maximum reserve, at wich comfort and gripp is still acceptable.
For that, I give 90% of calculated axleloadcapacity for max 160 kmph/ 99mph.
Here the list for your tyre 255/45R18 XL 103H
In front of cold psi in lbs, and behind in kg.
Gives 90% of calculated axleloadcapacity for the cold psi for max speed to yse 160 kmph/ 99 mph.
Now you "ONLY " have to determine the axleloads in your use 99% acurate, the most tricky part, and your responcibility.
The 5 puppets and truncs on the plates , max permissable axleloads are used with no reserve, but for max technical carspeed, wich shal not be above 190 kmph for your car, because T speedrated given as lowest on one size.
For the 2 puppets and one trunc, the carmaker determined the expected axleloads, and used them to calculate pressure , again with no reserve build in.
Axleload LBS / cold psi/ axleload KG
In front of cold psi in lbs, and behind in kg.
Gives 90% of calculated axleloadcapacity for the cold psi for max speed to yse 160 kmph/ 99 mph.
Now you "ONLY " have to determine the axleloads in your use 99% acurate, the most tricky part, and your responcibility.
The 5 puppets and truncs on the plates , max permissable axleloads are used with no reserve, but for max technical carspeed, wich shal not be above 190 kmph for your car, because T speedrated given as lowest on one size.
For the 2 puppets and one trunc, the carmaker determined the expected axleloads, and used them to calculate pressure , again with no reserve build in.
Axleload LBS / cold psi/ axleload KG
1634 | lbs/ | 18 | psi | / | 741 | kg |
1713 | lbs/ | 19 | psi | / | 777 | kg |
1791 | lbs/ | 20 | psi | / | 812 | kg |
1869 | lbs/ | 21 | psi | / | 847 | kg |
1946 | lbs/ | 22 | psi | / | 883 | kg |
2024 | lbs/ | 23 | psi | / | 918 | kg |
2101 | lbs/ | 24 | psi | / | 953 | kg |
2179 | lbs/ | 25 | psi | / | 988 | kg |
2256 | lbs/ | 26 | psi | / | 1023 | kg |
2332 | lbs/ | 27 | psi | / | 1058 | kg |
2409 | lbs/ | 28 | psi | / | 1093 | kg |
2486 | lbs/ | 29 | psi | / | 1127 | kg |
2562 | lbs/ | 30 | psi | / | 1162 | kg |
2639 | lbs/ | 31 | psi | / | 1197 | kg |
2715 | lbs/ | 32 | psi | / | 1231 | kg |
2791 | lbs/ | 33 | psi | / | 1266 | kg |
2867 | lbs/ | 34 | psi | / | 1300 | kg |
2943 | lbs/ | 35 | psi | / | 1335 | kg |
3019 | lbs/ | 36 | psi | / | 1369 | kg |
3095 | lbs/ | 37 | psi | / | 1403 | kg |
3170 | lbs/ | 38 | psi | / | 1438 | kg |
3246 | lbs/ | 39 | psi | / | 1472 | kg |
3321 | lbs/ | 40 | psi | / | 1506 | kg |
3396 | lbs/ | 41 | psi | / | 1540 | kg |
3472 | lbs/ | 42 | psi | / | 1575 | kg |
3547 | lbs/ | 43 | psi | / | 1609 | kg |
3622 | lbs/ | 44 | psi | / | 1643 | kg |
3697 | lbs/ | 45 | psi | / | 1677 | kg |
3772 | lbs/ | 46 | psi | / | 1711 | kg |
3846 | lbs/ | 47 | psi | / | 1745 | kg |
3921 | lbs/ | 48 | psi | / | 1778 | kg |
3996 | lbs/ | 49 | psi | / | 1812 | kg |
4070 | lbs/ | 50 | psi | / | 1846 | kg |
4145 | lbs/ | 51 | psi | / | 1880 | kg |
4219 | lbs/ | 52 | psi | / | 1914 | kg |
4294 | lbs/ | 53 | psi | / | 1947 | kg |
4368 | lbs/ | 54 | psi | / | 1981 | kg |
Would like to know your max permissable axleloads and vehicle loads. Can be found on VIN plate somewhere on car, I is front , II is rear.
The lower pressure behind then front, indicates lower MPAW rear then front.
For vans its mostly higher rear then front, then plate is wrong. I think they placed the van-image above, the wrong way around.
The lower pressure behind then front, indicates lower MPAW rear then front.
For vans its mostly higher rear then front, then plate is wrong. I think they placed the van-image above, the wrong way around.
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The top tyre pressure plate is from my T28. Max axle weights are front 1600kg and rear 1550kg with max mass of 2800kg.
On the weigh bridge the unloaded van (full camper conversion) weighs 1280kg front and 1000kg rear, so slightly higher pressure in the front makes sense. Loaded up the weight should end up pretty even assuming the additional weight is spread to a degree and not all behind the rear axle. Therefore even pressures front and rear is close. Even tyre wear over the last couple of years backs up these pressures.
Then I read wrong.
Fully loaded is the same front and back, and 2 puppets is front higher, as expected for motor in front.
1550 front and 1600 rear are that close, that same recomended.
My list gives 42 and 43 psi , is with max reserve for max 160 kmph/99mph.
Plate 45 psi , then for max technical carspeed, but with no reserve.
Fully loaded is the same front and back, and 2 puppets is front higher, as expected for motor in front.
1550 front and 1600 rear are that close, that same recomended.
My list gives 42 and 43 psi , is with max reserve for max 160 kmph/99mph.
Plate 45 psi , then for max technical carspeed, but with no reserve.
OK, so help me out here pls -)
I've a T32 LWB T6.1 DSG 150ps, camper conversion, its got 255/45R18 103Y XL tyres on it (just to be replaced since rears are really worn on the outside corner).
The van I weighed when touring Italy, it was 2560kg with 2 pax and loaded up with camping gear and luggage. With one pax, with all the camper conversion stuff its going to be about 2450kg, which is probably 70-80% of use cases.
I've no idea about the loading on each axle. The van only has a tyre loading/pressure sticker for R17s. I've tried various tyre pressures, currently sitting around 44psi on each corner 9got that from the CamperKing conversion website). Which may be too high given the above?
Any opinions on what I take as optimal tyre pressures ? Any thoughts before I put the new tyres on?
cheers, dave
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Here is a tyre plate sticker from a Cali for info:
And one from a T28:
Both have pressures for 255/45 18.
Then first I dangerously estimated your axleloads for 2560 kg, to be between 1250 and 1350 kg .
This would read in my list for exact the same tyres as you have, between 33 and 36 psi.
Yes that low if axleweights are right estimated.
Then max speed 160 kmph/ 99 mph wich you wont go over for even a minute, not that difficult to hold you on, I think.
And max reserve at wich comfort and gripp still acceptable.
The sidewear on one tyre is an alignment thing, so let it checked when changing tyres.
Hope rear can be alighned.
But howmany miles/ kilometers did you do with these tyres.
And same specifications tyres are fine to my opinion.
What do you mean with 2 pax and 1 pax.
Pax is just an abbreviation for passengers. maybe not used in NL?
I have just put new wheels on with 255/45/R18 tyres (Bridgestones) and have gone for 44 PSI all round. Looking at that California plate, I reckon that's probably a good starting point. Ride / handling feels fine to me.
(T28 110bhp SWB manual)
ok thanks. pax= person. So normally when I drive alone + stuff, load would be 2450kg. Wife+luggage= 2560kg max.. And I wouldn't go more then 99mph!
I think axle loading is probably about right. The main weight other than the base van is the poptop, kitchen area and rear RIB bed.
Reason for asking if that the VW label for the van, with 255/45R18s is 36/44 psi low loading, 48/48 high loading. Camper king (campervan builder) recommend 44/44psi, which is what I've been running them at for the last 3000 miles, before this they were lower pressure at the back (42/37) after getting the van. But this table recommends much lower pressures? Do you know at what loading the VW label pressures are calculated at? 36/44 would assume to be at a loading of about 2900kg based on your table, which seems wrong for a standard T32 van, 1 person, piece of luggage??
btw, I've no idea how many miles on these tyres. I bought the van with them and have done 7500 miles on them myself.
In that time, tread had gone down about 1.5-2mm on the front tyres and 3-3.5mm on the rears (based on previous MOT records), so twice the wear on rears than the front. Tyres were rotated just before I got the van. Mainly motorway driving. Hankook S1 Ventus Evo3 tyres. Total van mileage is about 34K. I suspect they're the 2nd set of tyres in the life of the van, tread wear would put them (guesstimate) fitted about 12-14,000 miles ago roughly and have about 2.5mm roughly left of tread. So I'm guessing these tyres are good for about 15-17,000 miles if they weren't wearing unevenly.
thx
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The carbase maker uses MPAW and max technical carspeed for calculating recomended pressures, but no reserve build in.
But also sometimes highes, as I suspect rear 44 psi . 44 psi here is for axleload 2x 875= 1750 kg max axleload upto about 180 kmph.
Do you have that rear?
The motorhome- maker assumes ilegal overloading, so not calculated verry high, for liability reasons. So if you use lower, you cant hold them responcible.
So if you determine needed pressure yourselfes, mind that its ypyr responcibility.
That is why I write that determining the axleloads 99% acurate, is the most tricky part, and your responcibility, a kind of disclaimer.
To low pressure for load and speed, leads to overheated tyre-material, then beginning cracks are created, that tear further in time, whatever you do afterward, untill mayby only afterv2 years that far, that tyre blows or treath separates.
Then the relation with that once overheating is long forgotten, and other factors are blamed.
So this overheating tyre-material is only allowed " ZERO " times in tyres use.
To high pressure gives discomfort, and bad gripp, and if much to high centrewear.
I determined in timevthat if one tyre uses 85% of calculated loadcapacity for the pressure, for 99 mph, discomfort begins.
So per axle, I use in my list 90% .
Then unequall load R/ L possible.
One sidev85% , so no discomfort, other side 95% , so still reserve for inacurate reading, pressure-loss in time, etcetera.
That you drive max 130 kmph/ 81 mph max , instead of 160 kmph / 99 mph , gives extra reserve.
But also sometimes highes, as I suspect rear 44 psi . 44 psi here is for axleload 2x 875= 1750 kg max axleload upto about 180 kmph.
Do you have that rear?
The motorhome- maker assumes ilegal overloading, so not calculated verry high, for liability reasons. So if you use lower, you cant hold them responcible.
So if you determine needed pressure yourselfes, mind that its ypyr responcibility.
That is why I write that determining the axleloads 99% acurate, is the most tricky part, and your responcibility, a kind of disclaimer.
To low pressure for load and speed, leads to overheated tyre-material, then beginning cracks are created, that tear further in time, whatever you do afterward, untill mayby only afterv2 years that far, that tyre blows or treath separates.
Then the relation with that once overheating is long forgotten, and other factors are blamed.
So this overheating tyre-material is only allowed " ZERO " times in tyres use.
To high pressure gives discomfort, and bad gripp, and if much to high centrewear.
I determined in timevthat if one tyre uses 85% of calculated loadcapacity for the pressure, for 99 mph, discomfort begins.
So per axle, I use in my list 90% .
Then unequall load R/ L possible.
One sidev85% , so no discomfort, other side 95% , so still reserve for inacurate reading, pressure-loss in time, etcetera.
That you drive max 130 kmph/ 81 mph max , instead of 160 kmph / 99 mph , gives extra reserve.
