sulli

I usually use a 12v compressor with a digital reader to set my tyre pressures every week. I assumed it was fairly accurate, being digital, and probably a lot more accurate than the ones you get at garages.
I do my fronts at 33 psi, and checked this against two of my old manual pressure guages - the ones that push the sliding thing out to indicate the pressure - one showed 37 si, the other 36 psi.
that's got me wondering which is more accurate, and what is the best way to check the pressure.
Whilst i'm asking, I am going away with a roofbox on the car, which is carrying and extra 60-70 kilos, most of which i think is one the rear. Any idea what pressure I should go for? Last time I did fronts at 35 psi, and rears at 38 psi.

Fangoria

iTrader: (1)

Digital is far more accurate - the old gauges have a huge tolerance error........the Digital ones are usually accurate to 0.5psi........... but I'd go with the small digi ones that you get from Halfords for about £8........The digi ones used in conjunction with blowing up your tyres are not accurate at all I'm afraid......Just a guide.......... The small ones from places like Halfords are the ones to go for

Re pressures

Dont know what size your wheels are......38 at the rear sounds very high just for an extra 70kilos's or so

When I go and fill up the car full on a beer run in France I put the front at 34 and the rears at 34........(my normal pressures are 34 front and 32 Rear)......Thats on 18inch alloys with 35 profile..............i.e. I dont up the fronts at all.........

I dont think I'd ever put 38's on them.........on 16/17's most I'd go on the rears is about 35 tops....... When I had 16inch alloys I put them at 33 front and 30 rear...........(the Scoob prefers lower tyre pressures at the rear - add a lot of weight in the rear and you up the pressures 2/3psi)

911

For what its worth, I think Fangoria is dead right about pressures.
When I set my pressures for racing my Sti I use my 25 year old tube analogue 'stick' gauge. I tested this at the start of the year against a calibrated digital, and it was spot-on as much as you can read an analogue gauge.
I'd go digital.

911

sulli

The reason I put that much in the rear is that full load rears should be 33 psi, but towing a caravan is something like 41 psi - and the rear was fairly under load so I figured that was about right - drove fine anyway.
The tyre inflator I have got has a detachable digital reader - similar to those you are talking about - so if I use that on it's own hopefully it should be fairly accurate.