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Coil over rear shocks


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Warning long rambling post !

Pondering the rebuild of the 5 because I've not actually got any cash to start it ! and my thoughts are currently focused on a rear anti roll bar.

Now I'm really impressed with how BUO my TR6 now handles even with a very average driver the thing goes round corners very well indeed, to the point where the LHC is suggesting the the MX5 seats fitted are not providing enough lateral support and I'm getting complaints ! So clearly the suspension set up is working well !

So back to my point, was planning to fit a similar set up on the 5 but the one issue I have with the rear ARB I have fitted is that it sits under the rear  chassis rails and the mountings can catch the ground especially when leaving petrol for courts and the like.

Now there is one supplier that provides a rear ARB that fits over the rear chassis rails ( it's a body off job to fit but I'm planning to Re chassis 

the car anyway) but you have to use their coil over shocks as well. I know that when this idea was being developed on a TR4a owned by. TVG member there were issues because I the shock aBsorber mounting point was moved towards the pivot point, the shock only operated over a very small travel and because of this the shock had to be set quite stiff which in turn lead to the shock getting to hot and putting a lot of strain on the trailing arm.

phew finally getting to the point .......anybody got this set up fitted and what are your opinions, please PM me if you prefer to respond privately 

Edited by Graham
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Might be worth looking at Neil R’s car and it’s performance on Tarmac rally’s./ sprints etc...looks pretty impressive to me.

 

Edited by iain
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I know that I might be considered biased, as I have known Neil since 1976 (when he undertook all the engineering drawings for the Technicalities booklet) and he re-built 4VC for me in 1990-1993, but every modification and improvement which he has produced over a great many years for TRs has been thoroughly researched, engineered and tested by himself, before ever he markets it.  Unlike Triumph and some other car producers, he doesn't use customers as the primary testers for his wares!

In the case of the coil over shocks for IRS TRs I know that he has had special shocks produced because a shorter stroke is required.  I have no experience of this system as my TR4 has a wonderfully crude system of uprated leaf springs and larger lever arm shockers - and the rear wheels stay upright all the time!

As can be appreciated from this video, and his personal involvement as sponsor and participant in the Sprint & Hill Climb Championship, his testing is far tougher than 99% of TR owners could ever achieve, and the results speak for themselves.  For certain, he doesn't hang about!

Ian Cornish

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One thing you do need to bear in mind with this setup is the extra strain put on the spring bridge, I have had to repair a couple that have cracked after a while of having this fitted,

Stuart.

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I have an underslung rear ARB too and initially it did ground on fast bumpy roads. I added a 9mm spring spacer & welded on some skid plates to protect the mounting. It rarely touches now.

You could consider cutting a slot in the chassis and mounting the ARB higher.

Jerry

 

Edited by jerrytr5
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Revington's description for the coil over shocker system states:

RTR 3003SPK. A limited amount of welding is required to the chassis to add mild steel strengthening gussets and top support plates to the spring turret. The lower bracket (consisting of a top and bottom part made from mild steel zinc plated) is secured to the trailing arm with nuts and screws.

I don't know whether this answers Stuart's point about extra strain on the spring bridge?

Ian Cornish

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16 hours ago, ianc said:

Revington's description for the coil over shocker system states:

RTR 3003SPK. A limited amount of welding is required to the chassis to add mild steel strengthening gussets and top support plates to the spring turret. The lower bracket (consisting of a top and bottom part made from mild steel zinc plated) is secured to the trailing arm with nuts and screws.

I don't know whether this answers Stuart's point about extra strain on the spring bridge?

Ian Cornish

Unfortunately that welding doesnt make any difference to the problem of stress transmission into the spring seat areas which is where I have had to repair them.

This chassis pictured below has that area built completely different to cope with a coil over setup if required though not fitted in this instance.

Stuart.

 

jeffstr5 160.jpg

jeffstr5 118.jpg

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  • 3 weeks later...

It is a simple geometric problem: If you put the damper 50% forward to the turning point

you have to increase the damping force by 100% for the same result.

 

What stresses the rear part of the axle area now adds double the force to the front area where

the spring is located. Although a very good idea just from the geometry and space for anti roll bar

it is not good for a stock TR without some reinfocement.

 

I love that type3 shock arm arrangement through the trunk and have that for many years in use.

860044296_Bilsteinrear.jpg.7310323313ffd57b41805bbe107cb865.jpg

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On 7/8/2019 at 4:02 AM, TriumphV8 said:

It is a simple geometric problem: If you put the damper 50% forward to the turning point

you have to increase the damping force by 100% for the same result.

 

What stresses the rear part of the axle area now adds double the force to the front area where

the spring is located. Although a very good idea just from the geometry and space for anti roll bar

it is not good for a stock TR without some reinfocement.

 

I love that type3 shock arm arrangement through the trunk and have that for many years in use.

860044296_Bilsteinrear.jpg.7310323313ffd57b41805bbe107cb865.jpg

I have the Type 3 shock mount on my 4A. It transfers the loads back to the original lever arm mountings. It is also the shock position on the trailing arm that Triumph used on the 2000/2500 sedans and the Stag. Good enough for me.

I recall that Kas Kastner says that “flat is not fast”. It seems that a bit of roll actually makes the tyre grip better. Away from the track, anti-roll bars transfer bumps from one side of the car to the other giving a worse ride. I read in Autocar each week about the appalling state of UK roads and wonder why anyone would want to add an anti-roll bar at either end.

I’ll get my coat and hat. The apparent temperature in Melbourne Australia today is 8 degrees.

Rockie

 

 

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2 hours ago, Rockie51 said:

I have the Type 3 shock mount on my 4A. It transfers the loads back to the original lever arm mountings. It is also the shock position on the trailing arm that Triumph used on the 2000/2500 sedans and the Stag. Good enough for me.

I recall that Kas Kastner says that “flat is not fast”. It seems that a bit of roll actually makes the tyre grip better. Away from the track, anti-roll bars transfer bumps from one side of the car to the other giving a worse ride. I read in Autocar each week about the appalling state of UK roads and wonder why anyone would want to add an anti-roll bar at either end.

I’ll get my coat and hat. The apparent temperature in Melbourne Australia today is 8 degrees.

Rockie

 

 

^ +1  I've tried pedalling that "anti roll bars doesn't necessarily give better handling" to the forum members for a while now. Kas and I are in total agreement regarding "flat is not fast" to the extent that the race TR7 V8 in my signature didn't have any anti roll bars ,...at either end, just corrected and remodified suspension, surprised Jeremy Walton the motoring journalist. Oh and if anybody has a car that  corners like it's on rails...you are not driving fast enough.

Pass me my scarf, it will compliment your hat and coat.

Mick Richards

Edited by Motorsport Mickey
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I can't comment on live axles or full race spec., I only do the occasional track day. On a road IRS TR a rear ARB is the most cost effective handling improvement you will make.

Jerry

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With no doubt the rear life axle suffers from bad mounting points.

The more power the car has the worse ist becomes.

On acceleration the rear lowers down and rests on the rubber bump stops.

That gives a crazy feeling when under accel a little bump is crossed.

I had the rear with hard race springs what gives a proper road holding and keeps

the rear up under acceleration.  Anyway that is not the best for daily use because riding comfort suffers badly.

Under these configuration the rear ARB is not necessary.

 

I went back to springs only a little bit harder than original and with that the ARB

reduces rolling. What is best depends a little bit on the tires in use. The lower

the tires, from /70 and less the more it helps that wheels are rectangular to the ground.

 

So if you are on /70 or /65 tires and do not set camber very negative and springs are soft

the roll bars front and rear are a good choice. They should be set that the understeer ex works

of the TR6 is reduced what means something should be done at the rear.

 

Bugatti went opposite way with positive camber and let the car roll. But at these days the

cars had bicycle tires that like that. No hard shoulders and very small and round at the contact area.

Todays tires are different, they are made stiffer and wider and have a flat contact area.

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Interestingly when Triumph went over to rear telescopics on the 2000/2.5/Stags which use essentially the same trailing arm set up they mounted the damper at the end (where they did the lever arm dampers on the TRs) rather than coil over.

The coil over set up does make the assumption that the coil is in the optimum position rather than the damper.

From a design angle having the coil over set up saves space, but that's not a consideration when retro-fitting to our cars.

As Stuart points out the loadings with the coil over set up have cracked a few chassis and arguably is only worth doing if you have the body off so the bridge can be adequately strengthened.

 

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  • 1 month later...

I removed mine because of the spring bridge starting to crack on both sides due to the state of our appalling road surfaces.Mind you I did thousands of miles in all conditions over a period of ten years.

I changed back to lever arms  of which a number in North London have done as well  (normal telescopic shocks) due to pot holes and the like.

Regards Harry TR5 Nutter

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