Trailing arm suspension flexing!!
Discussion
Hi Peeps..Got a mate to help by rocking the wheel as i found a lot of movement of the trailing arm..I dont think it should be so easy to move?...I couldnt see anything else moving other than a slight amount on the lower suspension bush..Could the mount fail after just a year?, Im also wondering if maybe the holes that the pins go through have become oval or something has snapped and will need welding?..Cheers..Ziga
http://s1114.beta.photobucket.com/user/mrzigazaga1...
PS:Does anyone else see a green horizontal line through the video?
http://s1114.beta.photobucket.com/user/mrzigazaga1...
PS:Does anyone else see a green horizontal line through the video?
Edited by mrzigazaga on Tuesday 15th January 15:31
mrzigazaga said:
Hi Mate..The movement is more in the trailing arm pin and mount where it bolts to the chassis..The other end hardly moves..Ziga
Hi Marke if the pins have been resently changed then i would be looking at the mounting piont as thats way to much movement in the wheel, if your free on sunday, pop over and i,ll jack it up and have a look with you, cheers, ralph
Cheers Ralph..I have spoke to Dan taylor who fitted the pins & Mounts a year ago and he wants to have a look on thursday, He said it might just be a case of tightening the bolts up..(Theres alway's hope)..Or some welding may be needed if the holes have become oval or something has snapped..
Thanks for the offer though and if the weather is ok on sunday then i might just take a drive over anyway for a cuppa..Thanks..Ziga
Thanks for the offer though and if the weather is ok on sunday then i might just take a drive over anyway for a cuppa..Thanks..Ziga
mrzigazaga said:
Cheers Ralph..I have spoke to Dan taylor who fitted the pins & Mounts a year ago and he wants to have a look on thursday, He said it might just be a case of tightening the bolts up..(Theres alway's hope)..Or some welding may be needed if the holes have become oval or something has snapped..
Thanks for the offer though and if the weather is ok on sunday then i might just take a drive over anyway for a cuppa..Thanks..Ziga
Hi MarkThanks for the offer though and if the weather is ok on sunday then i might just take a drive over anyway for a cuppa..Thanks..Ziga
no worries mate, always please to help if i can and good luck, lets hope it a simple fix , your welcome to pop over if you have time mate as be good to catch up, cheers, ralph
Hi Zig & a very happy New Year to you mate 
You're probably not going to like this but in my opinion the problem is a fundamental weakness inherent within the trailing arm design.
One of the critical jobs of the trailing arm is to provide correct axle location, there are a number of issues that conspire to mean the Lotus/TVR design fails to perform this role correctly.
A combination of that squidgy unsupported bush and the huge load it is subjected to, due in large part to the significant length of the trailing arm, and you have a perfect recipe for very early failure/play.
As you have demonstrated in the photos this wear first becomes visually obvious in the rear camber, Gavin's (Solitude's) was exactly the same, your video is clearly conclusive proof the bush is shot.
Even a newly replaced trailing arm bush will demonstrate surprising movement, remember even a small amount of movement in the bush translates to significant movement at the wheel due to the considerable length of the trailing arm.
It's the simple rule of leverage, & compounded by the fact that the bush is just too soft & unsupported, at the end of the day that bush doesn't stand a chance of locating the axle correctly even when new.
Poor axle location, wayward handling & excessive tyre wear are the inevitable outcomes.
All this is well understood, in fact it was well understood almost as soon as the system was designed, how it passed even the most basic pre-production evaluation is beyond me.
The design originates from the early build Mk1 Lotus Esprit, Lotus ditched it very very early on & for good reason, Oliver Wagglebottom then promptly took it with him as a gift when he moved from Lotus to TVR.
TVR also soon worked out Wagglebottom's gift was an ill-conceived one, its no coincidence TVR walked away from the trailing arm system when they introduced the mighty V8s Wedges.
I had my first good look at the design a few months back, & came away trying to think of a way of improving things.
Clearly I was never going to be the first to have these thoughts so I canvassed opinion amongst the Wedgie community on here.
Along with unintentionally upsetting a few Wedgies, the post did generate some interesting responses, with a few practical & innovative solutions to the problem just as I had hoped for.
One solution was to simply delete the squishy rubber bush replacing it with a polyurethane one, these are available off the shelf from SuperFlex.
You may want to talk to someone that's used polyurethane bushes to see how long they last, some poly bushes can have a very short life when subjected to the type of high loads such a long trailing arm would exert on them.
But TBH a poly bush has to be way way better than the squishy rubber one.
Another idea is to have a pair of bushes machined from bronze, or modify to a rose joint (major surgery).
My personal favourite was to cage the original rubber bush, more machining required but a neat improvement worth the effort in my book, it looks like this:
I like this idea but ultimately you need to accept all these ideas are not solutions, just improvements helping to conceal that inherent design weakness.
However I wouldn't mind betting that cage over the rubber bush or even poly bushes would make a massive improvement to axle location and the way the car drives.
My advise is dont bother with the squidgy rubber bushes, they'll probably only last a year or so at best, view your predicament as an opportunity to upgrade to something much better.
And for heavens sake do both sides at the same time or you will have a very imbalanced car.
If I had a trailing arm wedge (& you know I'd love a wedge) it would be the fist thing I'd do with the car.
Good luck with it mate, I hope these links help?
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
You're probably not going to like this but in my opinion the problem is a fundamental weakness inherent within the trailing arm design.
One of the critical jobs of the trailing arm is to provide correct axle location, there are a number of issues that conspire to mean the Lotus/TVR design fails to perform this role correctly.
A combination of that squidgy unsupported bush and the huge load it is subjected to, due in large part to the significant length of the trailing arm, and you have a perfect recipe for very early failure/play.
As you have demonstrated in the photos this wear first becomes visually obvious in the rear camber, Gavin's (Solitude's) was exactly the same, your video is clearly conclusive proof the bush is shot.
Even a newly replaced trailing arm bush will demonstrate surprising movement, remember even a small amount of movement in the bush translates to significant movement at the wheel due to the considerable length of the trailing arm.
It's the simple rule of leverage, & compounded by the fact that the bush is just too soft & unsupported, at the end of the day that bush doesn't stand a chance of locating the axle correctly even when new.
Poor axle location, wayward handling & excessive tyre wear are the inevitable outcomes.
All this is well understood, in fact it was well understood almost as soon as the system was designed, how it passed even the most basic pre-production evaluation is beyond me.
The design originates from the early build Mk1 Lotus Esprit, Lotus ditched it very very early on & for good reason, Oliver Wagglebottom then promptly took it with him as a gift when he moved from Lotus to TVR.
TVR also soon worked out Wagglebottom's gift was an ill-conceived one, its no coincidence TVR walked away from the trailing arm system when they introduced the mighty V8s Wedges.
I had my first good look at the design a few months back, & came away trying to think of a way of improving things.
Clearly I was never going to be the first to have these thoughts so I canvassed opinion amongst the Wedgie community on here.
Along with unintentionally upsetting a few Wedgies, the post did generate some interesting responses, with a few practical & innovative solutions to the problem just as I had hoped for.
One solution was to simply delete the squishy rubber bush replacing it with a polyurethane one, these are available off the shelf from SuperFlex.
You may want to talk to someone that's used polyurethane bushes to see how long they last, some poly bushes can have a very short life when subjected to the type of high loads such a long trailing arm would exert on them.
But TBH a poly bush has to be way way better than the squishy rubber one.
Another idea is to have a pair of bushes machined from bronze, or modify to a rose joint (major surgery).
My personal favourite was to cage the original rubber bush, more machining required but a neat improvement worth the effort in my book, it looks like this:
I like this idea but ultimately you need to accept all these ideas are not solutions, just improvements helping to conceal that inherent design weakness.
However I wouldn't mind betting that cage over the rubber bush or even poly bushes would make a massive improvement to axle location and the way the car drives.
My advise is dont bother with the squidgy rubber bushes, they'll probably only last a year or so at best, view your predicament as an opportunity to upgrade to something much better.
And for heavens sake do both sides at the same time or you will have a very imbalanced car.
If I had a trailing arm wedge (& you know I'd love a wedge) it would be the fist thing I'd do with the car.
Good luck with it mate, I hope these links help?
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
Hi Dave..Happy new year to you too..I did read your post on gavlar's trailing arm isssue, I agree that it does seem a bit of a crazy set up..putting all that stress on a bit of rubber doesnt seem right!..I did read that Tower view racing did an upgrade on the trailing arm with some sort of stabiliser bar..Does anyone know of anyone that had that done?..The cage idea looks better also..Cheers to all for the info, Im hoping that the bolts are a bit loose but im not that lucky!..I will know for sure hopefully tomorrow...Cheers..Ziga
RCK974X said:
Chimp, some interesting points you raise.
I have to say also that when I saw how that trailing arm is actually located with the dual diameter pin and considering the offset of load from the arm to where its resolved into the chassis, I can't see how those pins can survive without bending, let alone the squidgy bush....
Why the hell didn't the arm have the bush WITHIN it, with a bracket on BOTH sides of the bush connected to the chassis ? That would seem to be a sensible (and more common) design, instead of the horrid offset one.
I did wonder if it's possible to replace the bush with a roller bearing (like the rear wheel bearing) as the diameter is big enough....
Spot on RCK974X, I focused on the bush but you're absolutely right about that poor old pin, even a casual observer can see the geometry is all wrong for the system to work correctly.I have to say also that when I saw how that trailing arm is actually located with the dual diameter pin and considering the offset of load from the arm to where its resolved into the chassis, I can't see how those pins can survive without bending, let alone the squidgy bush....
Why the hell didn't the arm have the bush WITHIN it, with a bracket on BOTH sides of the bush connected to the chassis ? That would seem to be a sensible (and more common) design, instead of the horrid offset one.
I did wonder if it's possible to replace the bush with a roller bearing (like the rear wheel bearing) as the diameter is big enough....
As soon as the bush starts to wear, even more unnatural load & leverage is exerted on the pin, that pin must lead a really torturous life, no surprise to me it bends.
The fact it bends is more clear proof the design is flawed, I'd say Wagglebottom got his sums very wrong
RCK974X said:
"Why the hell didn't the arm have the bush WITHIN it, with a bracket on BOTH sides of the bush connected to the chassis?"
That's exactly what I thought when I saw it on Solitude's car, bracketing on both sides & caging the bush wont solve the geometry error, but it would mask 90% of the problem in a stroke.I'm pleased I didn't get anyone's back up this time, I was always taught before we can correct a design weakness we need to accept & understand it fully, that was the intention of my two posts & I'm glad my Wedgie mates understand that now.
I love my TVRs and I especially love a Wedge, part of the pleasure of owning any TVR is working out this type of thing and designing a solution, god knows I've uncovered a few on my Chimp, sorting them has been hugely rewarding
So now we have understood & accepted the fault we can start to embrace the ideas created by those resourceful Wedgies who have sought a fix.
I would call on the guy who created that nice bush cage to post a drawing, perhaps someone could machine up a batch to be sold within the Wedge community?
As I've said it's never going to be a complete solution, for that you would need to completely redesign the system, but it should mean the bush & pin last a reasonable amount of time.
A caged bush should also make a dramatic improvement to the way these uniquely charming cars drive & handle.
Come on Wedgies. I'm sure one of you chaps will have the skills & resources to make the bush cage a reality?
How about that guy who's been making all those lovely turned ally parts for you boys?
Good luck, I'm sure you can sort it
I think TVR "solved" the geometry issues of the design and "removed" the need for a rear anti roll bar by simply fitting really hard rear springs.
Should work fine on smooth roads, just a bit of an issue when you hits bumps mid corner. Axle tramp could also be a problem on more powerful cars
The TowerView stabiliser mod was reduce sideways movement from memory and I think it involve some welding to the chassis. Can't find a pictures of it, think they used be details on their website
Should work fine on smooth roads, just a bit of an issue when you hits bumps mid corner. Axle tramp could also be a problem on more powerful cars
The TowerView stabiliser mod was reduce sideways movement from memory and I think it involve some welding to the chassis. Can't find a pictures of it, think they used be details on their website
Danny Hoffman said:
I think TVR "solved" the geometry issues of the design and "removed" the need for a rear anti roll bar by simply fitting really hard rear springs.
That's not a solution Danny, it's a bodge!Sorry, but you cant solve poorly designed rear suspension system with stiffer springs, you'll just expose the problems in different areas and probably create new issues to boot.
The truth is TVR (& Lotus before them) actually solved the problem like any good engineer would.
They simply ditched the trailing arm system altogether and designed something better on a clean sheet of paper.
However, for those that have a Wedge with trailing arms, I still think big improves are available without major surgery.
From my point of view a caged bush (rubber or poly) seems to be the easiest, cheapest & most practical way to improve things.
Who will be the first to take up the challenge & machine up a few bush cages?
mrzigazaga said:
Hi Dave..Happy new year to you too..I did read your post on gavlar's trailing arm isssue, I agree that it does seem a bit of a crazy set up..putting all that stress on a bit of rubber doesnt seem right!..I did read that Tower view racing did an upgrade on the trailing arm with some sort of stabiliser bar..Does anyone know of anyone that had that done?..The cage idea looks better also..Cheers to all for the info, Im hoping that the bolts are a bit loose but im not that lucky!..I will know for sure hopefully tomorrow...Cheers..Ziga
I had the Tower View Racing trailing arm upgrade fitted to my wedge when I owned it Mark. It did improve the handling and I thought that it was worthwhile. Might have some photos of it somewhere, but not sure. If I can find them, I will try and post them up. Not sure if Tower View is still in business anymore though?Mark
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