77 911 Very Twitching Handling

[Peabo]

I got the car on the lift today and found the rear wheel bearings to totally solid. I really wanted that to be the problem. What's next?

[dwelle]

what tire pressure?...

[john walker's workshop]

Did you do what I suggested in post #3? Need to get that off the list of possibilities.

[Peabo]

Tire Pressure is 36psi all around. But we've played with other pressures.

As far as watching the side wall while i lean on the car; Sure, they have some give but if you are going to suggest tires, i'll ask what tires we are all ok with. As said, these are P6000 with the Porsche P rating. These tires were designed for this car. I'm on my 2nd set. So, should these tires work? Do we know they won't? Buying 4 more tires gets to be an expensive experiment.

What tires are ok?

[gumby]

Tire pressure is incorrect! please lower the fronts to 28 -29 lbs, all will be right with the car, there is a sticker in the engine compartment stating the correct pressure

[JSV798]

Fitting Pirelli P6000s on my 1978 SC cured instability. Initially I had P6000s fitted to the rear only after originals delaminated and with different make tyres on the front the car was twitchy. So fitted P6000s to front as well and problem was solved.

[RSTarga]

Originally Posted by JSV798

Fitting Pirelli P6000s on my 1978 SC cured instability. Initially I had P6000s fitted to the rear only after originals delaminated and with different make tyres on the front the car was twitchy. So fitted P6000s to front as well and problem was solved.

Mixing two different construction/manufacturer tires front to rear is a recipe for bad handling. BIG nono.

[tobluforu]

36 is high, drop it and test as it is easy money. Check your alignment sheet to see what Toe is at. If its zero, then that will cause the car to be twitchy like stated above. I run zero toe, 31 rear, 28. Good luck.

[Flat Six]

Originally Posted by Peabo

Tire Pressure is 36psi all around. But we've played with other pressures.

I run ~7 psi more in the rear vs. front ('85 w/16" 7 & 8); this is the first time I've seen anyone here say they use same inflation pressure all around -- other tire pressure threads I've seen have posters here say they run 5-7 psi more in the rear than front.

Didn't see it in your post but sounds like you're running 15x6 all around? If so, I'd try ~3 psi differential. I know you said you tried different pressures but though this might help.

[Marc Bixen]

36 in the front????????????????
Oy!
You may want to check and also see if the alignment was done at 36.
If so, have it rechecked.
>83 29F/34R 84> 29F/36R (Non-turbo,non-M491)

[T77911S]

too much air in the rears on my 930 makes it quite scary.
when I put new tires on it they inflated to recommended pressure I assume, (don't know what it is) the pressure was quite hi. I thought the tires just sucked. dropped it down and it was much better.
very hard breaking and the back end was everywhere. cornering was not too fun either.

[Bill Verburg]

I don't know where some of the posted tire pressures are coming from but while 36/36 cold is on the high side it is nowhere near being out there

I prefer 34/34 cold for street use myself but down to ~30/30 or so is fine too. For a track car you might start in the high 20s in the morning then adjust as temps come up w/ use but that's not desirable for street use.

was the car in question corner balanced? Wheels are stock Fuchs w/ no spacers or anything?

a look at the alignment specs and ride height would be really helpful

[GH85Carrera]

On one set of tires my 85 had very greasy handling when new. It took almost 100 miles for all the mold release to wear off. It was a very uneasy feeling.

[EC900]

My ‘77S had an odd high mismatch air pressures front and back set by PO for some reason when I bought it...P3000’s. I’ll agree with the tire pressure being too high for highway driving, think about the contact patch an overinflated tire has. Too low pressure and it should sway like a fish out of water essentially riding on both edges. As for the new tire theory, I recently put new tires, non OEM Toyos on my F150 and at highway speeds too, it was wandering all over the road, no crowns, no winds, proper PSI, no shimmy. Took it back to the tire shop and the alignment was spot on spec. They had no clue. After 200 miles it seems to have settled in better.

[93nav]

Like others have said, tire pressure. I think on a 1976 it calls for 29 front and 34 rear.

What speeds does this occur at?

Also, do you have any sort of duck tail or similar on the back and what is the front air dam? If they are not stock, they need to be a 'set'.

Edit: I just looked in the little spec book for 1976/1977 models. Pressure is: front - 2.0 bar, rear - 2.4 bar.

[Indescikov]

It is toed out in the rear.

[Flat Six]

Bump
Did you ever get this sorted out?

[Gordo2]

What steering wheel are you using? My car feels somewhat "twitchy" with a Momo 350mm vs. stock 370mm.

[aj88cab]

Steering shaft u-joint could be binding after sitting for 20 years.

[porsche930dude]

Is there a difference in the struts left and right? Like if they are backwards the caster would be way wrong? Because I deal alot with lifted 4x4s and people screw up their caster all the time by clocking the front diff up to get the driveshaft better. And this is what happens. Very twitchy steering that doesnt self center anymore