Tire pressures - rivals and Z2s

[BAR51]

Does anyone have good information about what tires pressures to use on 205/50x15 tires for a track e30 325i weighing about 2100-2200lbs? I had a lot of problems getting the rivals to stick with hot pressures between 36 and 31lbs and wonder if it was too low. The Dunlop Z2s seemed OK at about 33lbs hot, but love to hear other opinions.

[tinkerputzer]

I don't have useful info on those tires, but have you tried chalking them to see how much they are rolling over?

[L8 apexr]

Grassroots mag has all the answers in this months tire test,can't remember everything but don't run 36psi in the ZII's.

[Nsquared97]

IMO your best bet is to get a pyrometer (preferably probe type) and take inside/middle/outside temps, try to make them as even as possible with camber/tire pressure. Usually about 10 degrees higher on the inside is best.

[tinkerputzer]

Grassroots mag has all the answers in this months tire test,can't remember everything but don't run 36psi in the ZII's.

Link to article?

[brodee]

I run the Rival in 225-15. At autox I use 35 front 33 rear.

[JGood]

Depends on too many factors to get info from other people, unless you're running a showroom stock car at the same ambient temps as someone else running the same car.

As others mentioned, inner/middle/outer temps are the best way to figure it out.

As an example, I had to run really low pressure in the rear of my old track e30 to get enough temp in them to get traction. It was fully gutted, and without a full cage, extremely light in the rear. Someone with a spece30, even though it's the same suspension and tires as mine, would be running higher pressures in the rear.

[brodee]

If you don't have a temp gauge handy mark them with shoe polish or chalk on the triangles. Wear should come down to the top of the triangle. If it goes past it, add more air, nor far enough let some out.

[markseven]

If you don't have a temp gauge handy mark them with shoe polish or chalk on the triangles. Wear should come down to the top of the triangle. If it goes past it, add more air, nor far enough let some out.

This is a "do I need more negative camber test". Tire pressures are a little more proprietary / unique, per JGood's post. IMO.

[JGood]

This is a "do I need more negative camber test". Tire pressures are a little more proprietary / unique, per JGood's post. IMO.

I'd agree, if the temp equipment is available. But after some more consideration after my last post, 'the chalk method' / 'use what other guys are using method', may indeed be the best way for the causal autocrosser/HPDE guy to get within at least a usable range. There's really no need to buy a temp gauge for those kind of events, on street tires.

[markseven]

I'd agree, if the temp equipment is available. But after some more consideration after my last post, 'the chalk method' / 'use what other guys are using method', may indeed be the best way for the causal autocrosser/HPDE guy to get within at least a usable range. There's really no need to buy a temp gauge for those kind of events, on street tires.

Wow, I didn't even see that brodee said "if the temp gauge isn't available" part...

I retract.