Club 80-90 Forums

1985 14" DG Syncro

Grateful for some advice please.

I've upgraded to a set of 205/70/R15 on mefro 15" rims. Does anyone know the best front & rear pressures for these on a 14" syncro?

many thanks

Zeb

In the absence of any definitive response I have been delving through the archive and I did find some formulae to calculate a tyre pressure.
I’ve based the calculations on the quoted axle loading for a high top joker and added 100kg to each for a syncro. (does that seem right?)

my tyre ratings
106/104@ 65 psi

front axle 1100 kg + 100
rear axle 1300 kg +100

104 - 900kg
106 - 950kg

using the basic formula

front
1800kg
1800/1100 = 1.5
65/1.5 = 43.3 psi

rear
1800/1400 kg = 1.28
65/1.28 = 50 psi

using the safety formula
max axle load/tyre load x 2 ^ 1.25

front
1200/1800 ^ 1.25 = 0.59
0.59 x 65 = 38.35 psi

rear
1400/1800 ^ 1.25 = 0.72
0.72 x 65 = 46.8 psi

So the pressures from the door for 205/70 on 14” rims are 33 front and 36 rear. So I guess the questions now are, using the formula does 38 psi on the front and 46 on the rear seem right for a syncro, and have I loaded the axles enough? Also - should this be posted in the Syncro section?

many thanks
Zeb

I'd say you didn't get many replies because there isn't a definite answer, and everyone seems to have their own theory of what it should be. You calculations look sound, though the rear pressure sems a little high. Mine are usually about 38 front, 40 rear - but to be honest, they don't always feel 'right'. Seems to depend on the surface, rain/dry, and even the temperature.

ok - many thanks tforturton. I was hoping for some theories to get a feel for what was about right. I guess 38 on the front is a good bet and I'll start 46 on the rear and ease it down by stages if it feels wrong.

Zeb