Kingpins - various questions

[Robertmg]

Hi All,I recently had the front jacked up and noticed that there was play in the axle / kingpins. So a couple of questions before I start;

Firstly, I have heard that modern kingpins are very often under size which can cause issues. My question then is exactly how much under 3/4 should the kingpin be? Or, exactly how much over 3/4 should the bush be in order to give the correct tolerance for oil? Does anyone know which suppliers (ideally in the UK) provide the correct size kingpin? Or will I have to buy an adjustable reamer to make the bushes smaller?

Secondly I currently have the cotter pins which have the steering stops (both ends threaded) however agree that these are not very hard. Does anyone know of suppliers of hard steel cotter pins?

Lastly: I teamed the trunnions on my MGA with non adjustable straight reamer last year. I found that the reamer did slightly bind - are the curved blades significantly better? I ended up having to use lock tight to stop the bushes from turning whilst cutting but definitely want to avoid that on the T.

Many thanks

Rob

[Steve Simmons]

I recommend Roger Furneaux for king pins. I've purchased them from him more than once and they are always to spec. The fit in the axle should be snug but not super tight. The bushes must be reamed / honed to size. I use an adjustable reamer, starting deliberately undersize and then work my way up slowly. Ideally you would hone for final fit but I've had good luck just reaming carefully. I did a write-up on one set I installed. You can see it on pages 10-11 here: http://www.tcmotoringguild.org/chassis/20MayChassis.pdf

The double threaded cotters are correct, and Roger carries these as well. The small nut goes up front and the large nut in back. The large is only there as a steering stop.

I decided on straight flutes on my reamer. I can't remember the exact reason why, but it has worked well. The trick is to not cut too much at once. If it starts to bind, stop immediately and shrink the cutting size a bit. It seems like the bushing should not be able to turn if the press fit is properly tight. There should be 1-2 thou difference in the two parts.

[Robertmg]

Thanks Steve. Very helpful. Sounds like reaming 1-2 thou under kingpin is going to be the simplest solution. I can’t seem to find any helical adjustable reamers so maybe they don’t exist.

One last question, our manual for the TA/TB shows lubrication including the steering joints is oil rather than grease. Is it now generally accepted they got it wrong and grease is better?

[Steve Simmons]

Maybe someone more familiar with TA can comment, but if it were me, I'd use grease. I would also make sure there were channels for it in the bushings to ensure even distribution. Very early cars used oilers for king pins and other pivots, but by the 40's that stuff was going away, presumably because it required constant maintenance and didn't lubricate as well.

[Robertmg]

Thanks Steve

[ROGER FURNEAUX]

Thanks for the mention Steve! I do indeed have some NOS kingpins which are exactly 0.750" or even a 'thou over, plus the proper steel-backed bronze bushes. These are certainly an interference fit in the knuckles, in fact some little bits of steel are often displaced on pressing them in. The adjustable reamers are readily available: try Tracy Tools in Torquay (info@tracytools.com). It is difficult to make the first cuts in line with the opposite bush without a pilot, so I user a long reamer in my lathe to start off.

As to the cotters, I think I am the only person making these to the original pattern: they are made from alloy steel, very tough but not hardened, because you have to file them to fit (they are machined with an angled flat, but always need a little more taken off.

Email me on roger.46tc@gmail.com and I will send you a price list.

Roger Furneaux
Devon Olde England
TC0978
MGBGTV8
MGB