[928uk] FW: [Fwd: Re: PSD operation] & Tyre pressures

[Paul R. Smith]

I used to drop the tyre pressures in the winter by about 5psi, but 
didn't have RDK. The standard tyre pressures are set to prevent 
overheating at high speeds, but don't allow the tyres to warm up on 
cold, wet, straight roads.

The RDK sensors are temperature dependant, the given pressures being for 
20C, so you should be able to get away with a little less in the cold 
weather, but probably not enough to get extra grip without the warning 
going off.

Smiffy

On 09/02/2012 23:25, Mark Nichols wrote:
> Thanks Smiffy, I am pleased the function appears correct. You are
> right, I need to gain more experience. First car I have driven with
> an LSD and last night was unintended. Just poor driving. Cold night,
> cold tyres and poor road surface all conspired. I run standard wheels
> and T1R tyres at handbook pressures of 44psi rear and 36psi front. My
> TPS system works and nags readily if pressures drop by more than
> about 2psi. 44 Seems quite high for the rear. Do any 928'rs run at
> reduced pressures at all or is the 44psi considered optimum? I havn't
> run these tyres far enough to see if they are wearing in the middle
> yet.
>
> Regards Mark N 90GT
>
>
>
> ---------------------------- Original Message
> ---------------------------- Subject: Re: [928uk] PSD operation From:
> "Paul R. Smith"<smiffypr at clear.net.nz> Date:    Thu, February 9, 2012
> 9:57 am To:      928uk at lists.928.org.uk
> --------------------------------------------------------------------------
>
>  That all sounds like it is working correctly. The PSD does back off
> the locking gradually.
>
> In a cornering situation, with an open diff, the inside wheel would
> loose grip, limiting the torque to the outside wheel, allowing it to
> keep the rear end in line. With the PSD preventing the inside wheel
> spinning, it allows you to apply more throttle in the same situation,
> so when both wheels loose grip the back end goes more sideways. So,
> if you are using the extra grip that the PSD gives you, you need to
> be extra careful. Lifting off the throttle sharply makes it worse.
>
> You really ought to practice in a safe place rather than on a sharp
> country bend.
>
> Smiffy
>
> On 09/02/2012 22:23, Mark Nichols wrote:
>> Hi, My PSD appears to be working fine. Question is one of how it
>> should work in use. I have a steep drive (tarmac) and have to turn
>> sharp left into it from a narrow road, so no way I can enter square
>> on. Can't reverse on because front scrapes on the road. So what
>> happens is, no matter how careful I am, the inside rear wheel has
>> sufficient weight lifted off it so the PSD operates. I get onto the
>> drive and the PSD disengages and the light goes out, but it doesn't
>> release immediately, I can feel it engaged for a few seconds as I
>> ease up the drive (about 20 ft). All good. So I thought. Last night
>> I was a little too exuberant on a sharp country bend and the back
>> broke away. Fun I thought for a moment, but I wasn't able to
>> correct as quickly as I expected. Felt a bit strange which I could
>> only put down to the fact that the PSD locked the diff up once I
>> started snaking. Of course if the weight was being transferred left
>> to right to left, then I might expect that. I had lifted off the
>> throttle as it was quite low speed, but it got me thinking. How
>> quickly should the PSD activate and de-activate when it engages? Is
>> what I am experiencing normal? (I know, I should drive better!).
>> Thanks for experience shared. Regards Mark N 90GT
>>
>>
>>
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>>
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