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Why AVO's will NOT fit correctly and how to fix it.
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Dave-M
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Joined: 20 Jan 2006
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Location: Yorkshire, England

PostPosted: Fri Oct 10, 2008 12:14 pm    Post subject: Why AVO's will NOT fit correctly and how to fix it. Reply with quote

Before I get to the heart of the matter I would to ask you not to post a reply until I have finished as it's likely to take 2 or 3 consecutive posts to get all the information and pictures on.
Also I would like to give you a bit of information so you will know where I am coming from.
1) I am a yorkshireman and some of the following may appear a little direct, no offence it's just how I am.
2) sorry for the mix of imperial and metric measurements.
3)When I aquired my Olympic I drove it some 7,000 miles (from8k to 15k) and at the same time was fortunate to own and drive a 1972 Lotus Elan sprint, so I had experience of a direct comparison of the two cars, My Olympic is also 1972 registered.
I currently own a 1970 LotuElan Plus2.

so I guess what I am saying is that I have some experience of the "long travel / well damped" suspension that people talk about in a very vague fashion.
While I am at it I will tell you what I thought about my Olympic :- CRAP!!
Very harshly sprung, tremendous bump steer, serious roll oversteer and different handling in left and right turns when pressing on. Familiar?
Anyhow back to the topic of why the club AVO's are totally unsuitable for our Phase 2's.
This applies to both Front and Rear although only front is discussed in this post.

Continued....


Last edited by Dave-M on Fri Oct 10, 2008 2:44 pm; edited 1 time in total
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Dave-M
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PostPosted: Fri Oct 10, 2008 12:21 pm    Post subject: Reply with quote

Here is a picture of an AVO as supplied by the club.

and here is a picture of it fitted to the front suspesion assembly

Nice isn't it.


continued......
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Dave-M
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PostPosted: Fri Oct 10, 2008 12:29 pm    Post subject: Reply with quote

You will note that the top and bottom arms are set at their correct angles for normal ride height ie. bottom arm horizontal.
As seen here:- (Lotus front end)

And here:- (Triumph front end)

And on countless other vehicles using Triumph uprights.
continued..


Last edited by Dave-M on Fri Oct 10, 2008 2:46 pm; edited 1 time in total
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Dave-M
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PostPosted: Fri Oct 10, 2008 12:45 pm    Post subject: Reply with quote

This is not how it should be
.
This is the normal ride position on one Olympic, around 20 to 25 degrees below the horizontal. (WRONG)
The next picture shows the damper from another angle

It' s got it's rather nice Aluminium top mount for the spring fitted.
The original top spring mount is the beige coloured thing clamped to the top of the subframe.
Penny dropped yet?
continued....
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Dave-M
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PostPosted: Fri Oct 10, 2008 1:01 pm    Post subject: Reply with quote

The spring would have to fit in a much smaller gap if the Ali top mount is retained, not ideal, coil binding and an incorrect ride height, plus all the suspension load would be put through the rubber bush at the top of the damper (NOT GOOD)Remove the ali spring mount and use the original mount, not too difficult?

Doing this will enable an original or equivalent spring to be used.
All well and good so far
Now look at the gap between the bump stop and the damper body!!!!
Remember that this is with the suspension at normal ride height.
The damper has 90mm of travel in total with the ali spring mounting plate removed and assuming the normal ratio of 2/3 bump to 1/3 droop there should be around 60mm of gap between the damper body and the bump rubber stop. There is 13mm.
In the picture below the non attached damper shows the discrepancy.

Continued...


Last edited by Dave-M on Thu Oct 23, 2008 1:06 pm; edited 2 times in total
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Dave-M
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PostPosted: Fri Oct 10, 2008 1:28 pm    Post subject: Reply with quote

Long travel well damped, I don't think so.
If fitted as supplied, the slightest bump in the road would have the bump stop knocking itself into the damper body.
Were club supplied spax dampers to the same spec as the AVO's if so their reputation for leaking may be unjustified.
A basic error was made by whoever commisioned the dampers to be made, because they overlooked the fact that on the original set up,both the spring and damper mounted in the same plane and on the AVO's they are 50mm apart, thus reducing the available damper stroke by this amount.
Exactly the same applies to the rear suspension
No wonder there are bumps and bangs and damaged shocker mounts

As I have already bought my dampers I don't feel inclined to buy more to a more suitable specification, I am correcting the problems as follows.

I am having made 4 stainless steel top hats at the correct size to fit here:-

They will extend the top fixing, of the damper rod, in an upward direction by the right distance to restore the full 60mm of travel in bump and also locate the top of the 2& 1/4 spring.
This is the position (approx) the new mountings will have to be.:-

Give or take a bit.

There is a little more I want to add but it will have to be later.

What do you guy's think, are we on the road to a well suspended Olympic with a compliant ride.

Regards
Dave


Last edited by Dave-M on Fri Oct 10, 2008 6:48 pm; edited 2 times in total
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Rodsmith
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PostPosted: Fri Oct 10, 2008 2:50 pm    Post subject: Reply with quote

Dave, I can see what you are saying. You have used the pic of my bottom arm to illustrate the wrong angle. Surely if I lower the spring collar at the bottom the arm may well move up to a more horizontal state, provided that the spring is not too long or overstrong?

The penny has now dropped, instead of having 2" of damper movement, as I have now, I will have reduced it to nearly zero by altering the spring collar.

Your idea of extending the top mounting seems good. How close are you to getting the car back on the road to verify your ideas?

Rod
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calex_fr
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PostPosted: Fri Oct 10, 2008 2:52 pm    Post subject: Reply with quote

Does this draw resume the problem ?

http://2.bp.blogspot.com/_8YoJ4Mo6PmU/R0nhdG8GGMI/AAAAAAAABUU/uPGN33TONnc/s1600/DSCN3312.JPG
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Alexandre Contat

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Dave-M
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PostPosted: Fri Oct 10, 2008 3:00 pm    Post subject: Reply with quote

Alex, your link does not work for me
Dave
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Dave-M
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PostPosted: Fri Oct 10, 2008 3:09 pm    Post subject: Reply with quote

Rodsmith wrote:
Dave, I can see what you are saying. You have used the pic of my bottom arm to illustrate the wrong angle. Surely if I lower the spring collar at the bottom the arm may well move up to a more horizontal state, provided that the spring is not too long or overstrong?

The penny has now dropped, instead of having 2" of damper movement, as I have now, I will have reduced it to nearly zero by altering the spring collar.

Your idea of extending the top mounting seems good. How close are you to getting the car back on the road to verify your ideas?

Rod


Rod, My car is some way off yet, but really the top mount extension does not need verifying it just needs to be correctly engineered and fitted, I can't think of another solution can you? I am hoping to have my top hats in the next 7-10 days.
Dave
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Rodsmith
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PostPosted: Fri Oct 10, 2008 3:18 pm    Post subject: Reply with quote

Dave, I have sent you a PM
Rod
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Paul Narramore
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Location: Aylesford, Kent.

PostPosted: Fri Oct 10, 2008 5:44 pm    Post subject: Reply with quote

Dave

A very interesting subject and I'm glad somebody at last has looked at the suspension carefully and off the car to see exactly how it operates. With the aid of photographs it's now easy to see that the damper's travel is almost all used up with the AVO units.

Tell me, have you looked at the standard set up on a Triumph Herald/Spitfire? I don't recall the Herald having harsh suspension. I know the wishbones are mounted differently but I wonder if the set-up is dimensionally different?

I wonder what the Herald/Spitfire spring rates were and whether the Herald/Spitfire dampers would fit.?
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calex_fr
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PostPosted: Fri Oct 10, 2008 6:02 pm    Post subject: Reply with quote

calex_fr wrote:
Does this draw resume the problem ?

http://2.bp.blogspot.com/_8YoJ4Mo6PmU/R0nhdG8GGMI/AAAAAAAABUU/uPGN33TONnc/s1600/DSCN3312.JPG


http://crazyspitfire.blogspot.com/2007_11_01_archive.html


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Alexandre Contat

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Dave-M
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PostPosted: Fri Oct 10, 2008 7:36 pm    Post subject: Reply with quote

alex, I don't fully understand the drawings but the problem looks to be similar.
Dave
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Dave-M
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PostPosted: Fri Oct 10, 2008 7:45 pm    Post subject: Reply with quote

Paul Narramore wrote:
Dave

A very interesting subject and I'm glad somebody at last has looked at the suspension carefully and off the car to see exactly how it operates. With the aid of photographs it's now easy to see that the damper's travel is almost all used up with the AVO units.

Tell me, have you looked at the standard set up on a Triumph Herald/Spitfire? I don't recall the Herald having harsh suspension. I know the wishbones are mounted differently but I wonder if the set-up is dimensionally different?

I wonder what the Herald/Spitfire spring rates were and whether the Herald/Spitfire dampers would fit.?

Paul, I have not looked at the Herald/spitfire set up. I just wanted a solution to my problem.
I would guess the herald spring rates would be too hard, in fact they are what I assumed were originally fitted, which lead to the harsh ride.
I don't know if they would fit, i am just working with what I have got.
I am sorry i can't be more helpful.
Dave
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