Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) 1957 Plus 4 tyre pressures

Hi. Merry Christmas to all Talk Moggers.
Advice please on the correct/best tyre pressure for a Plus 4 four seater running on Good Year GT80 165 R 15 rubber.
The car usually only has two occupants.
Am I right in thinking that the higher the pressure the easier to turn the wheels or have I got that completely wrong.
This older Morgan seems harder to turn and requires a lot more effort at the steering wheel than my 1985 4/4.
Regards Jeepy

Most Morgan's seem to prefer a lower pressure. Around the 20-21 PSI range if I recall correctly. Some prefer different front and rear.

I use 21 PSI (but mine is slightly different to yours).

Most importantly is that the tracking is OK.

I run my Plus 8 at 20psi all round but it's on 205x55x16 so a bit different.
I use to run the 4/4 Sport at 22psi all round and that suited it on Toyo tyres.

I'm guessing the tyres are goodyear radial as denoted by the 'r' on your 1957 plus 4 4 seater?
We are rebuilding our 1958 plus 4 4 seater so she is identical to yours?
We have old tyres on the car which are Avon Tourist crossply, these are not as effective at gripping the road but do give easier steering and are the original spec for the tyres.

In rebuilding the car we have SU carbs and are trying to figure out how they are cabled up to choke and throttle cables can you help with a photo please?

You are correct insofar as higher tyre pressures will lighten the steering, but there are a number of other factors involved too.

What state are the steering link and track rod bushes in?

Are the kingpin bushes in good order? Are they correctly greased, including the underside of the bronze thrust pad?

Is the tracking, camber, and toe-in set correctly?

What about the size of the steering wheel? A larger wheel will give significantly lighter steering.

I use 20 to 21psi all round with the same size tyres on my Moss box Plus 4.

As Tim says, heavy steering can be due to a number of factors. The steering is always going to be heavy at parking speeds due to the combination of radial tyres, the heavy Triumph engine and the Cam Gears steering box, but it should lighten up once you are on the move.

Check the front wheel tracking.

When greasing the front suspension, it's important to get grease into the area between the steering damper plate and the top of the stub axle. Jack the car, use a large blunt screwdriver with a hammer to prise the damper plate away from its seat on the stub axle and this will allow the grease to travel through the grease nipple into the cavity in the stub axle and then out through holes into the area that you have prised open. Terry Foxen at GEE Ltd taught me this.

Rob

PM me with your email address and I will send you some photos of the throttle and choke cable set up.

Tony

Ahh, simple things here. That car, if it has the original steering box is 2:1, later cars were 2.5:1, ie easier to turn the steering wheel, but you have to turn it more.

So older cam gears cars do feel heavier.

26 psi (1,8 bar) seems to be right for my 4/4.
I tried lower pressure and was not happy .
Checked higher pressure too but 25-26psi fit best to my driving style.

I use the Peter Mulberry Thrust Bearing and shorter springs on My +8 Bitsa. Needle Thrust Bearings on the '63 +4-4Str and '61 DHC. Removed bronze plate and damper blades from all 3. Not needed if Wheels/Tires balanced and Toe In set properly. There is a little hole from the grease reservoir to the bearing (or under the bronze plate) that lubricates. Don't understand prying this plate up and putting grease on it. In over 30 years I have not done this. A Mixture of gear oil and Hyper Lube helps a bit. I use 24 PSI in My tires. Replace the TR heavy engine with a Modern 2.0 ltr engine at half the weight. (grin)