Strengthening the rear suspension.

[trsforever]

Hi Rob,
Nice looking project you have on the go, are you fitting parallel top links to the rear suspension? because that is when you
would fit a panhard rod or watts linkage, I have never seen a car with angled top links and also a watts or panhard I would think it might cause
more problems than it solves causing the rear to bind up in droop and bump as the links would be fighting against each other? I could be wrong
on that, but I would have thought good polly bushes in the rear would keep it in line, I used to rally a Toledo powered Sprint 16v with 180hp (less HP than you have but more extreme use) which has the same basic layout of rear susp and with polly style solid bushes in the rear it was solid as a rock. Good luck with the project.
Regards Scott.

[sonscar]

The whole suspension thing is a black art ,the only way
the axle can move is by twisting the bushes.If you as an extreme case replaced the bushes with solid bushes the only way it could move would be by flexing the mounts,possibly not a good idea.Compromise is required and the total range of suspension motion taken into account may mean that the deflections encountered are small enough to not be a problem.Boxing the lower arms may cause problems as theyprobably twist as they are now and boxing them may transfer this to somewhere else.I my experience,not with TR7 I add,is that when done carefully check periodically in use as the results can be serious if it goes wrong.Good modifying.Steve..

[Rich K]

It would also be worthwhile checking the condition of the suspension arm mounting points on the axle as these can become distorted through high stresses and weakening by corrosion. Just a thought while you are going to all the trouble of strengthening the mounting points on the car body.
Rich.

[Bobbieslandy]

A lot to think about! The mounting points on the car are solid and just how it left the factory. Genuinely.

My reasoning for fitting the panhard rod was to reduce the lateral forces on the upper and lower trailing arms, not really as a handling mod.

I have already stood there staring at the underside 'theorising' about what or what not to do, what i need is actual first hand experiences of rear suspension failures or stories where a 400lbft engine was thrown into a sound shell and ten years later nothing has failed. I could just weld everything up, this being my first thought but i would like to do what's necessary for this level of tune, no more and certainly no less. I'm also putting in a quaife diff, further increasing the stresses on the rear suspension.

My welding / fabrication skills are more than acceptable for a car and nothing i do will be unsafe. I'm aware that by strengthening, you are increasing and moving the flex to another part of the car, I'm only asking the (seemingly dumb) questions because i HATE doing a job only to be told afterwards that i missed something or "did you know after X thousand miles, this breaks". I get all the info first, make a plan, finish the job.

It's not often i have complete access to the underside of my car, 'right first time' is what i'm aiming for.

I will get pics of the mounting later today amd yes i am aware the anti roll bar lateral movement clamps are on wrong





Rob.

[Rich K]

Hi, carrying on from what Scott said about fitting parallel upper links, I think you should consider this. The works rally cars utilised parallel links with a pan hard rod and this is the normal arrangement with such a five link rear end. On the standard TR7, as I understand it, the lower links control the fore/aft location of the axle and the angled upper radius rods control the side to side location. If you add a pan hard rod to the standard set up then you may get undesired effects as per Scott's point that the two might fight against each other in some way. I am no expert but everything I have read points to a panhard rod and four parallel links being the correct way to go with this kind of set up.
Rich.

[Henry]

Agree with Rich K, Panhard rod will fight the triangulated top arms.
While you have the car like that have you also considered moving the holes for the lower arms upwards (towards the floor pan) as the works rally cars? It was done to alleviate possible axle tramp, I did it to my old car when it was up in the air like that. It was covered in Car & Car Conversions magazine back in the day when they did a whole series on making a TR7/8 rally car, the articles are available on the internet if you do a bit of digging.

[sonscar]

I can agree with weakened axle mounts


Steve..

[Bobbieslandy]

That's the lines i'm starting to go down.

I'll reasseble the rear end as standard, ie no panhard rod or relocated trailing arms, put the car down on the floor with some weight in resembling a fat bastard, take some measurements and Plan the new positions. The car will be lower than standard so will almost certainly need the trailing arms relocating.

Apologies if my last few messages came across as rude, it's difficult to get my point accross. I'm not rallying it, not racing it, not chasing the last 10th of a second of a lap time, i just want everything to compliment everything else. I don't believe i can just bolt in that engine, drive it reasonably hard and expect everything to be as i left it ten years down the line. Sydneys' pics are perfect, a few neat welds to hold everything together and Adams story of the brackets tearing off prove that some strengthening is necessary. The panhard rod will just be there to help the upper links with the lateral movement.

I like the Watts linkage idea but have to rule it out on the bang for buck principle, the gains just won't warrant the extra time and cost.

Thanks again,

Rob.

[tr8]

For race and rally the upper swing arms were made to be parallel to the lower arms in order to stop pulling the axle tubes out of the differential casing. The angled original arms pull out when the suspension goes up and the effect worsens with harder bushings or hiem joints. Here is a drawing that I got when I bought the TR7 race car that I restored (It had this set-up).

[tr8]

You can see the original angled mounts in this picture.

[jeffremj]

There is another rear suspension option that I saw on a Grinnell (IIRC). They had fitted the SD1 torque tube, the front of which has a bracket/arm that bolts to the bodywork. As you can imagine, the propshaft was the shortest I have ever seen!

[busheytrader]

I'm not sure if I described the corrosion I had to cut out and replace clearly.

It wasn't on the rear axle's brackets but on the rear floor pan and bulkhead close to where the lower arms locate. The stress cracks ran about an inch above the spot welded join with the floor pan, all due to rusty wafer thin metal. That caused rear axle steering as I accelerated hard up Elstree Hill in second gear.

A year or two later I noticed paint blistering on the floor behind both seats. It was directly above the lower arm mounting points, the contour looks like a large builders boot toecap when viewed from above. I sourced the repair sections from Robsport (but haven't found them on their website to post a link) and spent a hell of a long time welding and fettling them to fit as it was far from simple for my limited experience back then. Underneath the mounting point there's a thick gauge steel strap that bridges across It. I had to remove both of these to make my repairs but welded them back in to give as much strength as possible. I know some folks don't keep them after letting in new metal but I reckoned that the shell needed as much strength as possible since I'd doubled the power with the V8.

Adam

[sonscar]

On a similar vein,whilst fitting new disc pads I idly thought about what prevents the wheels falling off under severe braking?Two 3/4 inch nuts,If your floor/heelboard is good I do not think you have anything to worry about.Steve

[Bobbieslandy]

Hi Adam, totally with you on this. These are the areas i'm going to weld up along with plating the brackets. It's really tidy underneath, incredibly rare!







I love the torque tube idea too but it's a bit ott for me, as is the Watts linkage. I'm reinforcing what's already there because i already have lots of welding wire and plate. The Panhard rod is good bang for buck too. Also, installing parallel top links would mean ditching the springs, shocks and polybushes i have already forked out for, maybe when i stick something more powerful in

Steve, lets assume i am going over the top with all this, can you guarantee that with my engine and uprated suspension, i will never break those mounts? because i can't.

Rob.

[Bobbieslandy]

After getting the rear suspension / axle plascoated, i find an SD1 diff cover on ebay and the SD1 watts linkage on special offer at rimmers. Sods law. I'm never going to finish this car!