Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Steering - again

Steve - what weight did you have in the car when you did the measurements? It makes a big difference if unladen, as the wheels toe-in significantly in bump - maybe this is why MMC set them up toe-out at unladen knowing they will go toe-in laden? I do not for a minute doubt your results, only asking what the starting point was.
Also - does you car have the early SUPLEX suspension units or the later SPAX units with the increased ride height.
This would be useful for other owners. Regards PJB.

Steve, thanks for your input. and welcome the the TM Three Wheeler section. Peter has a very good point and it is probably the basic reason for the steering problems.

I'm wondering, and Peter may well know, if the ride height was raised after the initial setup of the steering, and if so, what was the reason for this. My guess is that it was to increase ground clearance under the bellhousing, the lowest part of the car? If this was the case, reducing the ground clearance by lowering the bottom spring platform, suggested earlier, may very well sort out the problem, the downside being extra vigilance for speed bumps and rough roads. The ground clearance under the sump on the Caterham is 75mm [3"] whilst the Mog has a huge 125mm [5"] of clearance under the bellhousing and far more under the floor. This would indicate that there is at least an inch or even two that could be used to lower the front of the car by, thus putting the steering arms into a more parallel position, relative to the ground, so that on bump or bounce there will be less movement transmitted to the wheel, thus causing less bump steer.

Whether altering the rake would change the roll characteristics enough to upset the handling is another question, I suppose the rear could be lowered a bit as well?

Peter?

Lots of things to think about here, I'm sure we'll get there eventually! They do afterall handle so well on smooth roads. Yesterday as I was going out on some particularly bumpy roads I tried lowering front tyre pressures to 18psi, I think it helped a bit .

The minimum permitted vehicle ground clearance in many countries is 100 mm. I don't know about America but this applies in Australia and some European countries (not Italy). Ground clearance is not currently part of the European homologation specifications.

This is published in some Australian explanatory notes:

• the vehicle must also retain 100mm ground clearance which
• all measurements must be carried out with the vehicle on level ground in its normal operating but unladen state

I have found that some states in America have a rule that nothing can be lower than the bottom of a line taken between the wheel rims. This is to avoid the car scraping the road if it gets a flat tyre (or should that be tire? )

The European standard for speed humps has changed but there are many that conform to the old standard still in existence, not to mention those that never conformed to any standard. The old standard was 90 mm but a variation (presumably to allow for subsidence or other changes in road surface) of plus 10 mm was permitted. Since mathematics is not an opinion this means that there are many speed humps of 100 mm in existence and a 75 mm clearance is going to give you a nasty jolt and maybe leave you hung up on a bump or a garage entrance. The new standard is 80 mm but still with a plus 10 mm permitted.

I know all about this because our car, as delivered from the factory in 2012, had a loaded ground clearance of about 85 mm or less. Not only did we his a lot of speed humps but we could not get the car into our garage. All the speed humps around Southbourne, Bournemouth were a real hazard for us and they are fairly flat. The springs were changed under warranty and we now have 100 mm ground clearance.

Interesting. Of course if the suspension were to be lowered, the springs could be stiffened a bit to compensate for load and compression, but, obviously not enough to ruin the ride.

It's all a compromise, and at least with speed humps, they can, or should be, seen in good time so that the speed can be brought down to a crawl.

I think the fact that there are minimum heights required in many countries would certainly influence the factory, and maybe this wasn't known at development time, but only came out later forcing the increase in ride height and associated problems with bump steer?

Will throw this in: After about 1500 miles driven singly, as in myself only, I had noted the bump steer and all the squirmy handling issues that have been observed. Had a friend join me for a nice run and the car was transformed! This was on the same local roads that I had been using and it was night and day. It behaved, the bump steer was noticeably diminished and diving into curves became much more predictable. Side note was that I was driving faster then before with much more confidence!

The added weight helped with the balance front to back as well as changing the steering geometry to what it's supposed to be.

My lady friend either has to join me full time or I will have to settle for weights...

I wonder if Morgan will introduce a carpeted lump of concrete like BMW sold in the 80s in Germany for the rear wheel arches in theboot of 3 series cars to improve grip in the snow?

"my lady friend either has to join me full time or I will have to settle for weights..."

It sounds as if you already know the answer to that question?

My mate had a 325i BMW when I lived in Bavaria I had an Audi Coupe.

The Beemer was a great car till you hit the winter. He was a scouser & too tight to buy the BMW blocks so he "liberated" some paving blocks from the house being built next door.

Happy days

Very much up in the air but I am hopeful!