sendarius

Hi All,

Just drove an '89 (that would be my very own '89 - whoopee!), and lo and behold it has RDK (something I didn't know until today).

The warning is lit on the dash - just what pressure is it expecting to see?

Be gentle:
I am at work - without access to the WSM,
the car doesn't have an Owner's Manual,
and search SUX.

I'd like to see if the RDK system works before I disable it.

RKD in OKC

I don't have a manual to give you the correct pressures, it should be on the inside of the gas door. There is also a proper procedure to reset the RDK. I do know you have to follow the procedure or it will go off all the time. The procedure is to air the tires to a low pressure, drive the car around the block, air them up to a high pressure, drive it around the block, then air them down to the correct pressure. Sorry I don't have a manual to tell you what those low and high and set pressures are.

The RDK worked great on my 90 GT and only went off when I had low tire pressure from a nail, then from a screw. I liked it as it warned me in plenty of time to get it fixed without ruining the tire and/or rim.

Rob Edwards

For '89 ROW cars the front sensors trigger at 2.5 bar, the rears at 3 bar, or 36/44 psi.

Dumb fat American question- do y'all use bar or psi in Perth?

SharkSkin

IMHO 36/44 psi is way too much. The car will have all the traction of a steel-wheel roller skate, and you'll wear the centers of the tires long before the edges. Best pressure will vary with specific tire brand/size/etc. and IMHO the only way to get it right is by driving it hard under the most common conditions you expect to see (highway, twisties, etc.) then checking for even temps across the tread. 32 psi cold is probably a much saner starting point.

sendarius

Thanks guys.

The tyres were at 40 PSI front and rear, so I'll try pumping up the rear, and seeing if I can clear the error.

Rob, we typically use PSI for car tyres, but the service station (gas station?) air pumps are typically calibrated in PSI and kiloPascals.

one kPa = 0.01 bar = 0.145 PSI

sendarius

Dave:

Yes, I realise that those pressures are ridiculously high for a modern tyre. The black round things on the car only loosely fall into the 'tyre' category, but this exercise is solely to see if the RDK system works.

As I said, I'll be disabling it - I am just interested to see if it functions.

John Veninger

There is a process to jump out the RDK so you don't get the warning when you run modern tires at a lower pressure. You remove the connector, jump pins 2 & 13 on the wire connector and leave disconnected.
Here are the details (if the members area ever gets fixed!)

members.rennlist.com/pirtle/zsusp_rdk_disable.txt

RKD in OKC

Again to reset the RDK so it works without false alarms there is a procedure of airing the tire to 5-6 psi less than the correct setting, rolling the car ie. drive around the block, then air them up to 5-6 psi above the correct setting, rolling the car ie. another drive around the block, then airing them down to the 36/44.

There is also a way to set the RDK with the Hammer and rolling the car only a few feet, but after setting them with the hammer they still false alarm a lot.

If you want to see if the RDK works, then follow the correct setting procedure, not just putting the correct pressure in the tires.

Could someone please post the instructions from the Manual? He posted that he did not have a manual.

jcorenman

The RDK system is described in detail in the 1990 "Service Information Technik" bulletin on the Morehouse CD's, pages 4-7 to 4-17. The sensors are simple diaphragm pressure switches, two per wheel. The front switches are set to 2.5 bar, the rears 30 bar (44psi). It is an elegant system, the fatal flaw is that this pressure is not adjustible.

The procedure that RKD describes above is a test procedure to verify correct functioning of the RDK system. It does not calibrate or adjust the system itself, it simply verifies that it is operating correctly. The procedure for correcting false alarms is described in great detail on the following page (4-17) and basically says "add air until the alarm goes away" .

The pressure-switches are available in two flavors: 2.5 and 3.0 bar. So in theory it would be possible to swap the switches in the rear wheels for 2.5 bar switches, this would get it closer. But if the nominal operating pressure is 2.5 bar (36psi) and you need to run a few pounds more to avoid false alarms, then even that is too high. I agree with SharkSkin that 36/44 or even 36/36 is too high for most tires.

The other option might be to disassemble the pressure-switches and modify them, has anyone tried this?




Cheers,

pcar928fan

Mine will false on my '92 at anything less than 38psi... That has come up from 37... Factory Euro wheels and car... Real PITA. They should have been set to alert you at 5 psi less than recommended pressure, ie 31 in the case of the GTS.

worf928

+1 what Jim (and Sue) wrote.

+1 what James wrote: GTS RDK is 36f and 36r.

My experience with the RDK is that it works perfectly. I, also, used to think that it falsed a lot. Then I threw away the pencil-type tire gauge and bought a well-calibrated "professional"-type dial gauge. No problems at all after that. The design of the system - while kinda sucky since it isn't adjustable - is such that it should be more accurate than your tire gauge.

Alan

Well the sensors are temperature compensated - which a tire gauge isn't.

But for aftermarket tires (of course hugely improved over original stock - not that you can even get stock tires anymore) it is just too limiting to not have any flexibility.

The idea of 'adjusting' the sensors is crazy - it isn't going to happen - you'd have to destroy them to do anything...

Much better systems now exist so its easy...

Alan

worf928

I'm not saying that isn't true. Just that the stock RDK system doesn't suck as much as everyone thinks. If you're running stock-sized tires the GTS-spec RDK at 36/36 is fine for street driving. OTOH, if you're running wider-than stock then 36/36 is going to be too high. 44 on the pre-GTS RDK is rock hard and way too much.

I've always found that just checking my tire pressures works pretty well - just part of my "pre-flight" checks. A solid RDK-like system on a DD would be convenient though.

pmooradian

I used to keep my stock GTS wheels at 37 all around and the RDK worked great. Never had a problem with the tires wearing unevenly. A few months ago my RDK brain crapped out, so I jumpered the system to disable it.

Anyone who isn't using their RDK brain any more that wants to get rid of it, let me know what you want for it! I'd like to replace the bad one on my '93.

Rob Edwards

Call me a freak but I installed my 17" Cup I's with RDK and bought the proper GTS-specific RDK sensor spacers to move them out the extra 1/2". The system works perfectly and 36/36 is fine with PS2's in the stock sizes.