TR4A/TR250/TR6 Front Suspension
Repair and Rebuild by Chris Lillja With input from Henry Frye, Cameron Greig and Roger G. Bolick.
Several people have asked about the inherent weaknesses of the TR4A/TR250 front suspension. Bill Piggot warns of it in “Original Triumph TR”, the TRF catalog mentions it, and Kas Kastner devotes a considerable section of the “TR4/4A Competition Preparation Manual” to it.
One VTR list serve member commented: “.I remember a number of bad accidents here in the U.K. in the late 70s early 80s when people were fitting over sized wheels and tyres. One accident I remember resulted in three deaths when the front suspension collapsed and the car turned over and burst into flames. The suspension is weak enough without the additional strain of larger wheels.”
Basically the problem is this: on the TR4 and previous cars, the front lower suspension pivots are built right into the chassis frame. This design is incredibly strong, but very difficult to adjust for camber -short of using a welding torch to heat and BEND the frame. It’s also much more difficult to repair accident damage. Triumph engineers also felt that the roll center needed to be modified. Their solution was to add four upright brackets fore and aft of the front suspension towers. “U” shaped pivot brackets bolt to these frame brackets. Shims can be added between the frame bracket and the pivot bracket to adjust caster or camber. The biggest problem with this arrangement is that the “U” shaped pivot bracket is only attached to the frame bracket with one 3/8 SAE stud through the thin sheet metal of the frame bracket. Over time and miles, stress distorts the sheet metal of the bracket, weakening it. After a while, the stud holding the “U” can pull right out of the frame bracket! The frame brackets themselves are also a problem, especially on the TR250 and early TR6. On all wide chassis TR’s (pre ’72 1/2) the rear brackets are braced to the frame at right angles with only one gusset plate, welded to the top of the frame at the rear of the bracket. On the TR4A, the front brackets are braced by the steering rack mounts and tied together by the steering rack itself. The problem with the 250 is that they had to move the steering rack forward to clear the longer 6-cylinder engine – so the front frame brackets are no longer braced. It seems common for 250 frame brackets to be completely bent as well as the studs pulling out! I have also been told that brackets can be bent even if gusset plates have been added.
Before you begin any work on your car, make life easier (and possibly longer) for your self and get (or borrow) a real Triumph style spring compressor. You could even make one if you had access to real, high quality threaded rod. Don’t use cheap threaded rod. “Hook style” spring compressors, that work on either the inside or outside of the spring, are not safe in this application. The part numbers from both TRF and Moss are listed on the parts list page.
Use good practice in jacking up the front of your car. Use good quality jack stands under the frame and some sort of fail-safe should the jack stands slip or break. I wedge my wheels under the frame of my car. If you’re thinking “woah – that thing could fall and damage my nice Panaports.” Think again Clyde, you can’t drive your Triumph if you’re dead. Make sure the car up there so solidly that you’re not worried about your Panasports OR your head!
Strengthening the suspension is simple, but not necessarily easy.
Strengthening the TR4A is slightly easier than the 6 cylinder cars because the front frame brackets are already “gusseted” by the steering rack mounts. This is not to say that adding the gussets described below isn’t a good idea. It’s just that you are starting with a stronger piece to begin with and the TR4A brackets seem less likely to be seriously damaged in the first place. In the “TR4/4A Competition Preparation Manual”, Kas Kastner gives instructions on how to modify the stock 4A pivots with a second bolt and suggests using the backing plates. Instead of modifying the original brackets, I did this repair on my ’66 4A using TR6 pivot brackets. I checked the frame brackets and original welds carefully. They were slightly distorted where the old single stud went through the frame bracket, but they were fine otherwise. The frame brackets all had two holes (TR6 brackets have four holes)… I had to drill holes below the originals to fit the TR6 suspension brackets and backing plates. The backing plates are just plate washers, about 3″ square, .125″ thick with four chamfered holes drilled in them. They can be used as templates to drill the new hole in the frame bracket. Position the backing plate on the frame bracket using two 3/8″ bolts through the existing holes. Mark the centers, remove the backing plates, and drill the holes. Remount the backing plates inside the frame brackets. This effectively doubles the thickness of frame in this area…. The backing plates cost about $3 each and the part numbers are on the parts list page. Some folks will say weld ‘em to the back of the frame bracket … I’m not sure whether it’s better to spread the load or concentrate it at the weld.
For the TR250, most sources recommend replacing all four suspension frame brackets, adding six new gussets (two to each front frame bracket, one to each rear). This requires all four frame brackets to be cut off and replaced. Unfortunately, I don’t see how replacing the suspension frame brackets could be done properly with the body in situ . Use TR6 pivot brackets with two 3/8 studs each, a nice heavy backing plate behind the frame bracket and new hardware to hold it all on. It looks like the gussets are doable on the car – but BE CAREFUL welding around those fuel and brake lines.
TR6 Owners already have the right pivot brackets and many TR6′s have already had the gussets added. Triumph knew of the problem and the gussets were added to the ’72 ½ and later cars. It’s still essential to check this area carefully. Frame brackets that have been gusseted have been known to bend and break. Add the plate washers if you don’t have them. That way you’ll know the hardware is new and the bolts have been torqued to specification.
If you have any doubts about the frame brackets on your car – replace your frame brackets! Do not “skip” the welded gussets if at all possible! The idea here is that adding the TR6 pivots and the backing plates are the absolute least you should do to any car that has not yet been done!
While it’s all apart, it’s a good time to renew all the bushings, shocks and springs, if this hasn’t been done already. The bushings are simple for the most part. On the bottom inner pivots it’s fairly easy to press out the old and press in the new bushings. On the uppers, the soft rubber bushings just pop out once the ball joint and the castellated nuts on the fulcrum pin are removed. I wasn’t happy with the stock upper bushings. I’ll be replacing them with a polyurethane kit. The lower bushings have a bonded inner steel sleeve. They seem much sturdier. I added an after-market anti-sway bar and mild competition springs at this time. There are several options for shocks.
After your done, you’re ready for a good quality, 4 wheel alignment. I believe the alignment specifications are given for the car in laden condition. If your shop has trouble, you should probably weight the car as specified in the shop manual.
The handling of my TR4A was completely transformed by doing this work. I can’t even describe the difference!
You might find a couple of surprises. I found that someone had reversed my front and rear upper control arms on the right side. I found that an upper fulcrum pin was installed backwards. I found that one of the studs holding the pivot bracket to the frame was nice and bent. Check your vertical links carefully. Many have become bent over the last 20 – 30 years. Does your rim rub on the top ball joint? This is probably the cause. So check everything carefully, even if it seems to be functioning properly. Hey, while you’re there, have you greased your front wheel bearings this year? How are those calipers and front brake hoses?
One of the best surprises of all is that the cost of the parts is very low and availability is excellent. Check out the parts list that follows. Prices are an approximate average, and, as always, your mileage may vary.
|Description||Triumph or TRF #||Moss #||Average Cost|
|Pivot Bracket Assembly||148691||661-595||$20.00|
|Nylatron or Polyurethane Bushes||HP129||681-235,245,275||$130.00|
|Front Shock (orig) (Koni)
|Front Spring (Reg)