Club 80-90 Forums

What are peoples thoughts on airing down tyres for offroading? The general view is that one should air down to give a better footprint especially on rocks etc so the tryre can maintain traction and grip the terrain rather than just bouncing off it.
However nearly everytime I've aired down I have either rimmed a tyre or damaged a rim a tyre popped off one the rims yesterday which was at 15 psi, 20 psi seems to be the lowest we can go on bfg 215 75 15's which in airing down terms seems to be quite hard
I am also wondering if Mefro's and Syncro rims are too wide allowing the tyre to come off the rim, would a slightly narrower wheel, which would grab the wheel better and allow for a more ballooning effect protecting the rim ? Any opinions ideas guys?

Never drop by more than 40% cuz you gotta take into consideration the weight of the van and what you are driving on. Airing down for snow I wouldnt drop by more than 20%

My Vito 15" rims are 5.5" wide but it does seem to result in a pretty tall tyre when fitted. The DG's pulling 20mph/1000 on the 4.86 diffs, that's the same as the SA
The speedo is now bang on though
P.S. In the snow I trundled about at 25psi.

205/70r15 Mudders on 6J (IIRC) merc steels, regular use 20-25psi when in quarries etc... if I know I am going on some road sections, then normally not less than 30..

Not bent a rim coz of low pressure..... did when i drove into something....

I used to do a lot of Classic Trials in a highly tuned 1285cc Beetle. We would regularly run on 6psi or less for maximum grip. Of course this means lots of punctures, carrying spare two spare wheels, plenty of tubes and a bead breaker etc. We can only use standard road tyres on trials cars and no ATs etc.

In mud and general off road in my Syncro I have been well impressed with where it will get me at normal pressures. In the snow and ice before Xmas I found that 20psi all round gave loads of grip. It has BFG ATs.

Don't do much trialling at present because of self employment and something called a Syncro. Still have my Beetle though. This is it on Blue Hills running at 10 psi - see the grip it gave: http://www.youtube.com/watch?v=9nzhHSuSB6w

I used to do sporting trials and we used to have to bolt the tyres onto the rims to stop them flying off

Vanagons have a tendancy to lose the bead very easily due to the higher lateral forces as you've discovered it doesn't take much to lose the bead. Depends on the surface you drive. I can only talk from sand experience low tire pressure make enormous difference. Getting completely dug down at 10psi you can often climb straight out of your hole by airing down to 5psi! If you're serious about increasing offroad traction and want to air down as low as possible you could fit staun internal bead locks. http://home.comcast.net/~hillmanpinz/71 ... dlocks.htm

thanks for the input guys reckon about 20psi is the lowest one can go. Myself and Dave were considering getting a foam pumped at about 10 or 15 psi like they do on plant machinery on the old conways i have which would then hold that pressure regardless of punctures although wondering could a tyre still come off the rim surely not ? What do you think ?