TR4/4A Early TR4 Rear Suspension & Tube Shock Conversion

[TRDejaVu]

This Winter I had a couple of posts asking specific rear suspension questions; thank you to those that offered advice.

This post is a bit about the leaf spring clean up, but mainly about the tube shock conversion that I decided to try.

The following is not intended to be used instead of workshop manual or vendor instructions. If in doubt have a professional do it with the proper tools and equipment; does that cover me for liability legalese?


Following the advice of others here, I dismantled my leaf springs to find the expected rust and some pitting.

I cleaned these up with wire wheel, careful use of an angle grinder and coarse abrasive discs. I primed them with Eastwood Rust Encapsulator then top coated with Rustoleum Pro.

Then following the advice of TeriAnn Wakeman and Randall I applied 2 inch UHMW tape to the upper surface of the spring leaves.

Next step was to replace the front spring hanger bushing with a Moss replacement (no pic). I then fitted the Joe Alexander rear spring hanger bushes. Really nice fit that required them to be pulled into place.

On to the tube shock conversion. Firstly, full disclosure. I came to an arrangement with Moss where I would review their Tube Shock Conversion kit (good or bad comments), but I did not get the kit for free.
Moss says that my kit is for cars up to CT23382.

A close up of the upper and lower shock supports. Notice that the lower one has a tie-down fitting for use when trailering.

You replace the original lower lever shock attachment fitting with their replacement. I had all my springs apart, but if you are doing it without going that far then use all the appropriate safety procedures when dealing with a loaded spring.

The Moss kit requires you to drill 2 new holes in the shock mount support structure of the car frame. They say to bolt up the upper shock mount using the 2 existing lever shock mount holes and then drill through with a 3/8 drill. I felt more comfortable drilling a pilot hole using a pilot bush. I then opened that up to just below 3/8 and used a reamer to reach the final size. Overkill, probably, but I had the tools from my aircraft days and I knew that I wouldn't have any problems with it. The holes were then painted for protection. Pilot bush in bottom right hole.

I did notice that the new holes came close to an unused blanked off hole. There are 2 stiffening pieces on the backside of the tower.

Everything else was a simple bolt-on job.
Upper shock mount setup

Lower shock mount setup

Complete assembly

I took the car for a short drive this evening; first of the season - yippee.

Not having driven it since last Fall, coupled with the leaf spring cleanup, UHMW tape and the new hard racing bushes makes an instant comparison difficult. That said I think that the overall effect is a more comfortable ride (for a leaf spring). I was babying it, but I tried a couple of quick tight corners on a country road and the car tucked right in nicely. I look forward to driving it harder and reporting back once I have let it settle in and rechecked all the bolts as necessary.

Comments on the kit. Time will tell if the design causes problems due to the different geometry and loads on the frame. The pieces appear to be very solid, but I have to say that the finish could be better (given the list price) as it was painted and not powder coated. People who want to do this conversion will have to judge for themselves whether the price is right as it is quite a bit more than the IRS tube shock conversion kit. That said, I am looking forward to driving it this Summer.

 

[TRMark]

Please, I do not want to insult anyone. But, honestly I do not like the looks of that conversion at all. I do not think the shock mount was designed withstand the stress that the conversion is going to put on it. The lever shock is mounted "close in" and link is located to inside of the spring. In this situation the shock is mounted out and will put much greater twisting motion on original mount, which is built of very thin material. Putting UHMW tape on the springs has removed it internal friction, in itself a dampning affect, making the situation worse yet. Just my two cents, and again I am not trying to cause difficulty in the forum.

 

[PeterK]

I really like the trailer tie down built on the spring plate. Might have to copy that one.

 

[bgbassplyr]

Please, I do not want to insult anyone. But, honestly I do not like the looks of that conversion at all. I do not think the shock mount was designed withstand the stress that the conversion is going to put on it. The lever shock is mounted "close in" and link is located to inside of the spring. In this situation the shock is mounted out and will put much greater twisting motion on original mount, which is built of very thin material. Putting UHMW tape on the springs has removed it internal friction, in itself a dampning affect, making the situation worse yet. Just my two cents, and again I am not trying to cause difficulty in the forum.

Just my opinion and also don't mean to ruffle any feathers, but I must agree with this assesment. There will be more flex to the mount than the frame and original shock mount can deal with over time.

The new shock tower needs a trianglulated mount at the top to transfer load front to rear AND side to side to the frame. This will require an added structure to transfer the load to the opposite side frame rail and to the same side frame rail.

 

[martx-5]

... I do not think the shock mount was designed withstand the stress that the conversion is going to put on it...

We saw the results of this in our club with a TR4 that was converted like this. The shock mounting on one side ripped out of the frame, and the other side showed signs of cracking. This all happened within about three weeks. We had to re-do the sections of the frame where it ripped out and reinforce the bracket. We also spanned across the two shock brackets with a brace. Admittedly, the frame wasn't in the best of condition, so make sure everything is real solid in that area.

 

[PeterK]

Coincidentally, this appeared on another forum :

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]The site above was pointed out by Bob Adams a day or so ago in an email about
Restomods. ( https://media.photobucket.com/image/ratco/Tabcon1/frame-2.jpg?o=9 ) and contained
photos of a very nice upgrade of the TR four cylinder motor---along with four
frames showing RATCO's newly manufactured frame for this TR4 "restomod". I
noticed that a couple of the photos had a red cross bar spanning the rear
shock mounting brackets and since I also have one of Tony's (RATCO) new frames
for my "restomod TR2 project" I inquired about this unfamiliar connector
link. Here is the story: RATCO also makes tube shock conversion kits for
TR2/3b's and rear sway bar kits. When the k as installed on some original
frame vehicles there were isolated incidents of the shock brackets breaking at
the frame joint, so RATCO set out to rectify the problem or stop selling the
kits for original framed cars (no problems with the new frames as they are
much stronger). I will quote from Tony's
response as follows;

"The rotation force of the lever shock on a stock frame is longitudinal and
the rotation of the tube shock conversion on the bracket/frame is transverse.
That places a different set of forces on the frame rails which in any case,
connects the shock system to the structural base. The new tube shock mounts
also have a longer are and hence a greater rotational torque. In old frames,
if the weld between the shock bracket and frame has lost some structural
integrity, then the chance of a break is possible. The red cross bar in the
photos on Tabcon1's site was designed to transfer some of the shock pulse to
the other side of the frame. The forces in the tube conversion rotate around
the longitudinal axis so this brace transfers force to the opposite side
during a pulse to any one side. When a simultaneous shock is hit, the effect
is nilled by the brace which then takes the full force of the pulse. This
"fix" will not help however if an original
frame is structurally unsound."

I am passing this information along in case anyone out there had preformed the
tube shock and or rear sway bar upgrades on an original frame TR and is
looking for a bit of "insurance" is unsure of their frames true condition.
NFI

Regards,
Dan Cronin[/QUOTE]

 

[TRDejaVu]

Thanks for the comments. I will see what Moss has to say about this. The mod is easily reversible if necessary.

 

[TRDejaVu]

I appreciate everyone keeping the discussion away from that of purist vs resto-mod. I hope that it will be useful to those who are considering future options. I welcome all the comments as I have not yet decided whether to continue with this mod or go back to lever shocks.

Here are the initial comments from Moss:

They have a TR4 that was used for kit development and testing, with over 2 years and several thousand miles logged.

They have many kits out in the field with no reports of frame failures.

They stress that the frame must be in good condition, for this or any other shock absorber. An obvious one.

They question if some of the other kits use shock compression and dampening rates that are matched to duplicate stock ride quality, or if they were too stiff for this particular application. They found many shocks that almost fitted, but would actually bottom out, which will result in higher forces transferring to the frame. They say that both of these conditions would require the use of a cross brace.

They describe that their upper and lower shock mounts are 90 degrees to each other to allow for side-to-side and forward-to-aft movement of the axle, which will reduce strain on the frame.

They state, "Our position is that we have taken the appropriate engineering steps to provide a product that performs better than original and is safe to use."

So, comments please.

 

[PeterK]

I think we've already made them.

 

[TRDejaVu]

I just thought that people might might be interested in how Moss responded and whether they think any of those comments were valid or BS. Sorry to have wasted your time.

 

[martx-5]

You're not wasting anyone's time. I'm glad they responded as they did, and I think that Moss has addressed several important issues that might plague other kits. However, they do stress that frame integrity is still very important. As I mentioned above with the Ratco Kit that was installed at his shop on the TR4, on the surface, the frame didn't show any outward signs of being in bad shape. It was only after the shock bracket ripped out of the frame (within three weeks) that the real problems showed up. The frame was rusting out from the inside and some critical areas around the shock bracket were just too thin to withstand the extra forces imposed by the extended bracket. After repairing the frame, Tony decided on adding the cross bracket as some insurance. The car has been fine ever since.

So, it's vitally important to really know that your frame is in top notch condition before you go ahead with this modification.

 

[PeterK]

I just thought that people might might be interested in how Moss responded and whether they think any of those comments were valid or BS. Sorry to have wasted your time.

I appologize for my smartxxx remark. Didn't mean anything by it, just a chuckle. And you certainly didn't waste my time.

I've always been interested in this mod but from what I've gathered, it interferes with aftermarket wheels. So it's a no go for me. I had my levers rebuilt (Apple) with HD valving and so far they work great.

 

[TRDejaVu]

Thanks for the feedback. I have to admit that the jury is still out on whether I keep it or go back to lever shocks.

 

[TRMark]

Moss Europe sells a conversion I like a lot better. It looks like the shock is on the inside of the spring, and the upper mount bolting to the bracket is in the original plain of the lever shock. It does require welding.

Moss Europe Conversion