Trailing arm pins and bushes (again)

[V8 Fettler]

The eternal problem for early Wedges. Mine has just broken the nearside pin for the 2nd time in 12k miles, the concept of a shoulder on a safety critical pin is a nonsense. I'm looking at re-engineering the arrangement with an M16 bolt, replacement bush and thrust washers but I've got no wish to reinvent something that's been reinvented before, so suggestions gratefully received please!

[Danny Hoffman]

Do you know who supplied the replacement pin?

I've never had a problem with mine in 15 years and 70,000 miles (144,000 in total on the car), so maybe there is another issue or the quality of the replacement is poor.

[V8 Fettler]

Source of pin 12k miles ago was and is a reputable supplier of TVR spares.

[Danny Hoffman]

Have you raised it with him? If it's who I'm thinking of I'm sure he will offer a solution.

[V8 Fettler]

Thanks Danny. Got to finish dismantling first before approaching the supplier. Previous fracture was obviously a slow process (corrosion visible on the fractured faces), latest has no corrosion visible on the fractured faces.

[RCK974X]

Yeah, I reckon it's a dodgy design too - that shoulder/reduction in diameter is an obvious failure point IMHO.

One of my pins was bent at exactly that spot, and I had a local engineering place make me a new one out of an M16 bolt (NZ is a long way away!) and I wondered at the time if it was possible to replace the pin with a simple M16 bolt....would be stronger, and would just need a new type of bush ??

There's also another thread here about this, a few owner have added brackets to stop the pin flexing....worth a look at the pics...

[V8 Fettler]

Thanks Andy. Did the pin you had made still have the shoulder?

Edit: UKAuto's solution sounds interesting http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[RCK974X]

Yeah, machinist guy made an exact copy of original (but without the bend!!)
right down to checking the large washer was a push fit....was an excellent job really.

It's been OK since, or at least it doesn't look bent as far as I can tell...

[V8 Fettler]

To bring this back up: a local car restorer has designed and fitted a new pin/bush assembly based around a 16mm shaft with no shoulders, car has done about 700 miles since the work, seems fine but then I've never pushed the wedge to the limits on corners (which makes the 2 failures of the original design even more concerning). I'm going to have the other side done later this month, will report back!

[mrzigazaga]

Hi Mate...This sounds like it could be a good idea...I have had mount failure twice in one year and with minimal mileage, Again from a reputable TVR supplier!..I have opted for the superflex mounts which i know are new and not 30 year old stock..Will report once they have been fitted..Cheers...Ziga

[V8 Fettler]

mrzigazaga said:

Hi Mate...This sounds like it could be a good idea...I have had mount failure twice in one year and with minimal mileage

This was the same side?! Meaning the original failed after an unknown mileage and unknown age, but the replacement failed very quickly? The original is/was so far past it's original design life that failure is possibly understandable (did TVR design to a lifespan? Probably not), but for a replacement to fail so quickly is a nonsense, safety critical etc.

The failure mode for mine was very similar on both occasions: extended acceleration uphill (20 - 80ish), slowing to 15 mph and then some bumps/potholes. Crack! Car becomes undriveable forwards (rear wheel fouls arch) although could be reversed to safety. Gives me the heebijeebies thinking about it happening at speed, but perhaps it wouldn't fail catastrophically at speed?

[marcus1875]

Mines failed n/s coming up the a68. i was driving rather spiritedly around a particular windy section south of lauder. 30 - 40 miles till i got home. the corners were a bit hairy after that but drove fine in a straight line and didnt hit the arches. although i wasnt going too spiritedly as the wheel bearing went first.
got my new one from what is probably the same reputable source, couple of hundred miles done and it is excellent. touch wood (or veneer).
marcus

[V8 Fettler]

Hi Marcus, did your pin fail completely? I rode an RD350 in 1980 ('81?) on the A68 (or was it the A69?), can still recall the g forces on my head and neck at the bottom of the hills. Happy days!

[mrzigazaga]

Funnily enough when i ordered two mounts and new pins..(Again) from the same supplier the mounts felt a bit rough and like they were made of charcoal..I guess they were old stock as it looked like it might of dried up somewhat losing it elasticity and cushioning ability..It was suggested by the supplier that its not the bushes failing but an underlying problem with my chassis after i explained that they had failed so quickly.. ..Subsequently it was all checked over with a pry bar before and after the fitment of the so called new bushes and no movement or issues were found yet a couple of months later they both have failed again!..Suffice to say i wont be using them again or recommending them to anyone...I know the trailing arm design is not the best but the bushes should not fail so easily.

There is an interesting modification being carried out at the moment with a fellow PH'er and if it proves its worth then its definitely something i will invest in...Especially as i now have an extra 100bhp added to my 280i....

[V8 Fettler]

Hi Mark, did your pins fail? Or just the bushes?

[mrzigazaga]

Hi Mate..The pins failed the first time..One being bent and a bugger to remove but the second time they rusted in place..Everything was cleaned and greased the last time so the new pins should be ok..I hope, It was only a couple of months ago...Ziga


PS:Meant to add..This is a very interesting thread...The last post is the mod that i was talking about..
http://www.pistonheads.com/gassing/topic.asp?h=0&a...

Edited by mrzigazaga on Sunday 16th June 20:43

[marcus1875]

hi v8. yeah my pin failed. the bush was blown and the pin bent. but probably bent by the bush disintegrating!
the a68 is good if you can get a clear run, unfotunately some local neds have torched most of the cameras which is a shame.
marcus

[mrzigazaga]

phillpot said:

Those look very much like the forward diff mounts on an S Series (Sierra diff), do you know what Superflex list them as please ?

Hi Mate..I believe they listed them as for The Doloren DMC but if using it for trailing arm then the pins wont fit as the steel inners they supply were thicker..The original trailing arm pin sleeve can be removed and fit's snuggly into the superflex bush..(You just reminded me)...Cheers...Ziga

[phillpot]

Thanks, found 'em on the Superflex website.

At over £150 a pair I think the old rubber ones will have to do a bit longer.


So my little S has something in common with a Delorean!

Edited by phillpot on Thursday 15th August 06:40

[mrzigazaga]

phillpot said:

So my little S has something in common with a Delorean!

Yep!..Just like the wedge..Reach 88mph..Add 10,000 Gigawatts..I prefer Zigawatts and away you go...