Tyre pressures - again

[DavieR]

I've found a lot of good advice on the forum and have tried to put it all together to arrive at suitable tyre pressures for my Ducato Maxi based 3500kg campervan.

 

I have Vredestein Comtrac 2 All Season 215/75 R16C 114/116 fitted, the same spec and rating as the original Conti Van Contacts.

 

The weight plate states

3500kg

(1) 2100kg

(2) 2400kg

 

Weighbridge measurements fully loaded are -

Front axel 1740kg

Rear axel (single) 1720

Total 3460kg

 

Fiat recommend 4.5bar/65psi front and 5bar/72.5psi rear.

 

I've emailed Vredestein with the above info but have probably left it too late for a reply as we head off on Monday for a trip.

 

I took a look at http://blobs.continental-tires.com/www8/servlet/blob/476070/960c00deff28484e7fbdec87d1d00583/download-technical-databook-data.pdf and on pages 82/83 read that my pressures should be 3.75bar/55psi (added10% to load) front and rear.

 

I've noted the legal/insurance issues of running with lower than Fiat's recommendations and at this stage I don't have a weighbridge ticket or Vredestein's reply.

 

Is 3.75bar/55psi correct?

 

[Keithl]

Hi Davie,

 

I have just gone back to my old time resource of the TyreSafe website only to find it has just been updated!

 

https://www.tyresafe.org/tyre-safety/

 

The Download for MH specific tyres appears to be no more and in its place is a new tyre pressure calculator!!!

 

https://www.tyresafe.org/check-your-pressures/motorhomes/

 

If you enter your plated axle maximum weights and pick your tyre size it comes back with 3.76 bar 55 psi Front and 4.08 bar 59 psi Rear so your guesstimate is pretty close.

 

I would print out the TyreSafe webpage and carry with you as evidence for running at an alternative pressure to the Fiat figures you quoted earlier.

 

Keith.

[Derek Uzzell]

DavieR - 2017-09-02 8:18 PM

 

...Is 3.75bar/55psi correct?

 

 

Continental’s data for a tyre with a similar specification to your Vredesteins indicates that - for your weighbridge-measured axle-loadings - around 3.35bar/49psi should be suitable and ’safe’. Adding your 10% comes to around 3.75bar/55psi and that seems fine to me.

 

Continental’s advised pressures for the VIN-plate 2100kg/2400kg maximum axle-loadings would be 4.25bar and 5.0bar respectively, equating roughly to Fiat’s recommendations (with a bit extra for the front axle), but you aren’t loading your campervan anywhere close to those maxima.

 

 

[DavieR]

Keith & Derek, many thanks for the confirmation.

 

I had read the Tyresafe motorhome page but it doesn't specify my tyre size. The page is still there, I found it here -

https://www.tyresafe.org/wp-content/uploads/2015/12/motorhome-leaflet.pdf

 

The tyre pressure calculator is new to me and is a great resource!

 

Hopefully, Vredestein will get back to me and I'll report their recommendations if and when.

 

Thanks again.

 

 

[colin]

My van XLWB Maxi has same rated tyres and similar loads.

I find at 55 the handling starts to noticeably change, over 62 the ride becomes quite harsh.

[DavieR]

colin - 2017-09-03 9:21 AM

 

My van XLWB Maxi has same rated tyres and similar loads.

I find at 55 the handling starts to noticeably change, over 62 the ride becomes quite harsh.

 

Yes, driving our camper back from the dealer at 70/62 was a little harsh. Funny that both myself and OH have been to the dentist with broken fillings since :-D

[Chudders]

Post removed by me. Misunderstood tyresafe web site