trunnion failure

[acbateman]

We have a 1991 live axle car with the older trunnion-type front suspension. We have owned the car for 8 years, oil the trunnions with EP90 oil and have not had any problems. However, I am considering upgrading the front suspension to double upper wishbone and lower ball joints, mainly to avoid the risk of trunnion failure. How common is trunnion failure and is it worth changing the car's specification in this way? I am also considering changing from the standard rack to a 20% rack [for other reasons].

 

 

[Casbar]

I have also got a 91 live axle. I fitted double top wishbones, this was probably the best upgrade I have made. It made the car feel a lot more solid under braking. I also changed the shocks at the same time to Leda's so that may have had an effect as well.

 

You can fit the de-dion double top wishbone and ant roll bar onto a trunnion upright, but you need to change the wishbone track rod ends, as the non trunnion upgright has a different top taper to the trunnion upright. The track rod ends are about £5 from motor factors, and are off of a Fiat 132, although I can give you the part No when you are ready.

 

As for trunnion failure, if they are oiled regularly they shouldn't fail, I haven't heard of one failing, (someone will probably be along to disprove that statement). I thought about changing the uprights, but couldn't justify the cost, just for the sake of not having to oil the trunnions.

[AMMO]

I have been told by a Lotus Elan specialist that trunnions only fail if they run out of lube and are allowed to run dry for quite a while. More importantly you must check your bottom wishbone for cracks in the lugs where the trunnions and shock absorber bolts mount through.

 

Nowt wrong with trunnions.

 

AMMO

[Mcalvert]

Any idea what this complee conversion is likely to cost? Thanks - Michael.

[Bare]

Perhaps you should "search" for issues regarding the Rose jointed replacement for the simple/stupid and essentially trouble free Trunion before you discard it for the wrong reasons... I't's interesting :-)

Tens of Thousands of Triumphs survived fine using Trunions.. and I've heard tell that some even raced !..and they usually weigh double the weight of any seven.

[AMMO]

Grand Prix cars from the early sixties had trunnions.

 

If anything the measly 5/16" bottom suspension bolt in the non-trunnion wishbone has to be a bit suspect. Why do the suspension manufacturers all use a 1/2" o 12mm bolt on suspension if it was not neccessary?

 

AMMO

[Graham Perry]

Agree with Ammo. There is a bigger risk of wishbone failure at the bottom damper mount lug than there is of trunnion failure on a 1991 car.

[Sheds Moderator]

I don't think trunnions break very often - it used to be a problem with ratty old Heralds and Spits but only when they had been neglected and allowed to run dry. Most 7 owners are much more meticulous than this, and generally they don't do the miles between maintenance sessions. (OK, so some drive 20000 miles a year in the thing, but they are a minority and I hope not averse to a bit of maintenance on the P&J.)

 

On my old spit I had 1 trunnion go, but it was just an MoT fail, nothing catastrophic.

[Nigel Riches]

I had a trunnion snagged at M.O.T. time, but on closer inspection the movement was in the "top hat" bushes that the wishbone bolts through, so some new bushes and away we go again, fill with oil and they'll last you O.K. Nigel.

 

1982. 5 speed, clamshells. B.R.G / Ali. The True Colours.

[Old Septimus]

There are some great pictures of Brabham's championship winning Cooper Climax in this month's Motor Sport in cluding one of the front suspension, Herald upright and trunnion in full view. If it's good enough for Black Jack....!

[Joe 90]

On my car the upright snapped just above the trunnion because the trunnion had seized to the wishbone . According to the manual, the top hat bushes etc do not require oiling, and don't have a grease nipple, which means they would have to be stripped down anyway. Ball points are so much more reliable that you should seriously consider them.

 

99,700 miles so far

[AMMO]

Oliver

 

Ball points? I prefer fountain pens. 😬

 

AMMO

[PeterS]

I had both trunnions fail on my 1985 live axle car, in separate incidents, more than a year apart. The first time I was negotiating a mini roundabout in a quiet village, so was only doing about 15 to 20 mph. The second time I was doing about 70 mph on a dual carriageway. Close inspection afterwards showed that the trunnions had been kept properly lubricated, but the damage caused by the front suspension collapse, the wheel suddenly bouncing around in an unaccustomed way, crossing both lanes of the dual carriageway mounting the curb and continuing along the central reservation meant that meaninful failure anaylsis of what was left of the trunnion was virtually impossible.

I subsequently heard of a number of Seven owners who had experienced trunnion failure, but they always seemed to have gone at low speed. Caterham didn't have an answer, but the fact that they have subsequently designed out this problem, may be related to the stresses which Caterhams put through the component compared with a Triumph Herald.

At the least, I think the trunnion should be replaced every 3 years as a precautionary measure. Failure of this component can be catastrophic for the car, and even the occupants.

My car did quite a high mileage. The second failure occurred at (from memory) 50,000 miles. This could be a contributory factor.

[Graham Perry]

Interesting Pater, thanks for that. I am glad now that I have just replaced mine.

[Casbar]

You have to make your own decisions. There will always be someone who has had a failure. The reason Caterham changed to non trunnion, was nothing to do with safety, but to do with availability of Triumph parts.

 

If you looked at stats and at the number of Caterham and Triumphs running around with trunnions, the failure rate contributed to the trunnion must be a very small proportion. If you look at previous posts, someone has had a de-dion top wishbone failure, so as I've said, there will always be component failures at some point.

 

I don't think one failure would make me spend circa £300 just to get rid of the trunnions

[Old Septimus]

I had a trunnion seizure on an elderly Standard with the same upright where the thread in the trunnion for the upright had become so worn that the upright cut its own new thread in the trunnion which made the steering very heavy but didn't cause the trunnion to fail (or indeed fail its MOT but it was years ago). I suspect that seizure of the top hat arrangement and shearing of the bolt into the wishbone is likelier but regular examination of front suspension movement should guard against this. Are rod ends that more reliable? Morris Minors which use a different trunnion system can suffer a suspension collapse when the king pin jumps out of a worn trunnion.

[Sheds Moderator]

As most people have establishedd, there are 2 bits to wear out on a trunnion - firstly the top hat bushes, which are not luricated, being made of nylon, (and IMO no more subject to breakage than a BJ) and secondly, more famously, wear on the threaded bit of the trunnion as a result of neglect. This is the fave MoT fail point where the guy puts the bar under the wheel and lifts it up and down by 1/2". A siezed thread will prob. break the kingpin.

 

f you are really bothered, why not swap them out as service items? A kit comprising bushes and brass part was £15 last time I looked (say £25 now, tops) and took an hour to fit, each side. You can regrease your bearings at the time. Say every couple of years, and oil the things nice and regularly. This has to be a better route than a £300 conversion.

[edmandsd]

I wouldn't be surprised if the main reason for trunnion failure is as a result of the rubber bushes they're supplied with being too small and not moving with the suspension thus resulting in wear on the side of the wishbone. I instead used some titanium bearings off an old Le Mans Jag but i'm sure somewhere like Rallye design would do the plastic bushes in a top hat configuration.

 

Lets not forget that these trunnions are a well proven patented design........... and all things considered better in my opinion than an oversized rosejoint mounted the wrong way around taking the full suspension load.

 

Home of BDR700

[acbateman]

Many thanks for all of your comments! Does anyone have any bright ideas for the best way to oil the trunnions? I have tried a plastic grease gun filled with oil but this tends to leak out everywhere! More recently I have been unscrewing the grease nipples and injecting oil in with a plastic syringe but this is also a major fiddle. Is there a gadget that I can buy? Finally, I have heard at least one respected Seven authority suggest that grease CAN in fact be used instead [contrary to other advice]; what's the feeling about this as well?

 

 

[Mr Locust]

On my Triumph based Locust I had a trunnion failure which was caused by the threaded stub breaking off the bottom of the vertical link (low speed on a car park). It was a clean break, brittle fracture, with no evidence of the problem having developed over a long period of time and no real signs of wear on the threads. As a precaution I immediately changed both vertical links, trunnions, dust seals and nylon bushes etc. and got on with another 40K miles without trouble until some t********r wrote the car off by running into the back of me with a Vectra.

 

Links and bits were from TD Fitchett 01952 619585- Triumph specialist that advertise in most Practical Classics.

 

Original and Haynes Triumph service manual for Spitfire, Herald etc clearly state that EP 90 is to be used - that was good enough recommendation for me. A small 'Wanner' type grease gun is ideal for getting oil into the grease nipples - just keep pumping until clean oil starts to come out from under the dust seal. That way any contamination gets flushed out. Put some rag on the wheel to catch the spill - or do it on next door's drive if you don't like them!!!!!!!!!!!

[Sheds Moderator]

Any decent grease gun will do it. Back in my Spit days I used to favour using moly grease one time and EP90 the next - when one eventually wore out and I stripped it the thing was full of lovely slippery black gunk which had done it no harm at all. IMO the only drawback to using grease alone (and many did!) is that it may not reach all the threads, also that the extra viscosity makes it more difficult to detect wear. Conversely grease doesn't drain away like oil.