You don't say what rim widths you are using, but the pressure seems very low.
I have Vredesteins with 185/70-15 on the front of my 100M and regular profile
185-15 on the rear for higher gearing (very similar to 590-15 RS5's bias
plies), all on 5.5in rim width, 72 spoke wires. I run them at 28-30psi,
depending on road speed or event and get a smooth, stable ride with good
balanced handling. I am a bit surprised by the other replies quoting 30psi
front, 28psi rear, although maybe the later 6 cylinder cars need this to reduce
front end understeer with the greater engine weight compared to the 4
cylinders. Is this what the drivers manual says? I have always thought
pressures were set a bit higher at the back with rear wheel drive (as I have
always used for 20 years with my 185/70-15 TR4A Vredesteins) and a bit higher
at the front on front wheel drive. In both cases to balance the handling with
safer understeer occuring first. For an example, Pontiac quotes 30psi all
round for my SSEi Bonneville, but I raise the front to 33psi and can hold tight
fast turns with very little understeer until it breaks away and slides sideways
in the limit.
From: John Snyder <firstname.lastname@example.org>
Sent: Dec 26, 2004 3:07 PM
Subject: Tire Pressure
What is the collective wisdom out there on the best tire pressure to use in
185/70-SR15 Vredestein tires mounted on reproduction MiniLite wheels running
w/ 23 psi pressure? The idea was that since these tires are wider than
original and have a higher load rating, they should be run at a lower pressure
than normal. My freshly restored BT7 MK2 has this set-up. It has what I
would describe as a "bouncy" or "jiggly" ride on pavement that is less than
smooth. The entire front suspension has urethane bushings, but this feel
seems to come from the rear as much, or more, then the front. All four shocks
have less than 1600 miles on them.
This ride became more noticable to me when as an early Christmas present to
myself I took back to back drives in the above car, my freshly restored BN7
MK2 and my BT7 (MK1). Both those cars have 60 spoke wires and 165 tires.
Any suggestions would be appreciated. TIA
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