The Rear Suspension

[pacotaco]

Help! I know all of this has been covered but reading all the posts has my head spinning with all the different answers. I am going frame up with a TR4A IRS but not to concours only to have a good reliable (ha!) driver. I am not going to autocross or race only enjoyment driving with the wife and occasionally sport thru some corners. First does anyone know the rating of old Moss part #670-148 coil springs (They were built to Triumphtune spec's and are for TR250/TR6 from what I have been able to find out). Will they raise or lower my car? Should I use polyurethane spacers or rubber? Most important will they make my car ride like a truck or be good? I got these new with the car. I bought urethane trailing arm bushing from TRF and am considering the adj trailing arm brackets. There does not seem to be a consensus answer on converting to tube shocks I was considering Ratco but now I think I will have Worldparts rebuild my levers - is this a good decision with the above parts? I want better handling and durability but do not want to ride like a truck. Oh I have done all the frame reinforcements front and back. If I use the above springs what should I purchase to "match" on the front. Like I say my head is spinning. Any advice based on experience or expertise would be appreciated.

 

[poolboy]

The answers to a lot of what you ask will be subjective. What I can tell you is that the stock rear springs for a TR6 is about 350#'s
Now, for an opinion, keep everything stock for the kind of driving you described. That's what the car was built for.

 

[RJS]

I know what you mean. My TR4A still has its original rear suspension but, I have done much research for when the time comes to rebuild my suspension.

The stock TR4A rear spring is rated at 280lbs and has a 9" fitted height.

From my information, Moss here in the US has 5 part numbers for rear springs:
675-035 280lbs Stock replacement NLA
670-148 420lbs
670-168 350lbs "stock height, uprated 25%"
670-188 335lbs "lowered HD, +20%"
670-045 354lbs "Stock TR6 replacement"

The Moss Europe catalog states the following:
“The rear end of the IRS TR4A was notoriously weak. Our standard spring (GSV1001) is in fact a TR6 rear spring specification which is slightly uprated (TR4A standard is 280 lbs) while GSV1001 is 354 lbs (+26%) really is the min strength to use on TR4A’s to avoid sagging rear end look. We sell hundreds of TT4212 which is a nice compromise between ride and handling, it’s rated at 390 lbs (+39%), which should not cause any passenger discomfort.”

I drive like you do and here are my thoughts when the time comes
-670-168 springs
-Rebuilt lever shocks with uprated valves
-Poly trailing arm bushes
-Undecided on poly spring pads but, will probably go with them for durability and longevity
-Stock trailing arm brackets (not the adjustable ones)

Hope that helps

Bob

 

[tdskip]

My comments are based on doing a complete rebuild of a TR6 and TR4A IRS suspensions. I will only use poly bushings at this point. I have not found they make the ride harsh but they will tighten up the handling. The quality of the rubber bushings today is - frankly - lousy. In SoCal at least they will degrade even if the car is lightly used and stored inside. There are different grade bushings, I've found the ones from BP Northwest to be consistently good. I have not used TRF ones so ask for people's experience who have.

Stock rear arms if in good order will be fine, if you are unsure of the condition of yours send them to Peter and team at NOS Import. Great folks, very reasonable.

Stock springs with poly bushings all the way around will be comfortable still. You can swap in TR6 rear springs in replacement of your TR4A original ones for more control without a big difference in ride.

It is common that new springs will change your ride height, sometimes greatly. If you start mixing and matching suppliers you are setting yourself up for a lot of work on then trying to dial-in ride height etc. Not that much can be done, especially on the rear, unless you use Richard Good's adjustable rear bracket kit. I highly recommend it, mainly to dial in handling, but useful on getting the rear ride height just right as well.

 

[pacotaco]

OK finally thanks to RJS I know the coil spring rating on the the uninstalled old Moss coil springs. At 420lbs it sounds like that would put me in for a rough ride. So I think I will bite the bullet and probably go with the matched set of uprated springs that TRF has for the front and rear since I was going to have to buy the front anyways. When I retire in a couple of years I will have a access road of 1 1/4 mile to the house that is not paved and rough and don't want to tear up the car with overly harsh suspension. Also I just want to enjoy the ride and enhance the handling some. It seems that maybe the Armstrong levers will work for me especially if they have some uprated valving and maybe the newer seals that Worldparts puts in them. They say they don't have a "heavy duty" upgrade like Apple Hyd but will provide heavier valving. What is the difference? I guess I will go with the polyurethane coil spring pads for durability unless someone tells me a good reason not to. TDSKIP I will look at NOS rebuilds. BOB I believe you may drive like I want to and probably will end up with what you suggest although I think I will go ahead and build it back up with the adj trailing arm brackets. BOB what did you do on the front?

 

[tdskip]

Just be aware that the TRF springs will likely raise the ride height

 

[Rrbbeerrttoo]

My last rear end improvement was discarding the lever shocks rebuilt twice at Apple Hydraulic in the last few years , but never showed much difference, even with few miles on paved roads. Recently I installed tube shocks and I noticed a great improvement...just another subjective opinion!

Robert
66' Tr4a irs

 

[HerronScott]

Tom,

I don't recall seeing any huge amount of ride height changes when I restored my TR4A using TRF's uprated front and rear springs (SAH606 and SAH1081). I think they called them mild "competition" and were not supposed to change the ride height.

The green car has the factory springs and the blue car has the TRF uprated springs. This was right after I had finished the restoration on the blue car.

Of course these were the parts TRF was selling back in 1984 so not sure how today's versions compare. When I checked they are using the same part numbers still though.

Scott

 

[sail]

This is with TRF HP 132 springs which are Goodparts 1" shorter. There is no spacer in rear, adding 3/4" spacer in front should do it. These are harsh on cracked city streets but great on the road.

The rear felt dumpy. TRF originally sent what were called 20% stiffer standard height which made it look like a 4WD. I think they have it figured out now. Putting new stock springs in the rear and going driving is how I would do it over.

 

[pacotaco]

When TRF and Moss and others refer to standard or stock coil springs are they selling the 280lb springs that the TR4A came out with? Why would anyone want that coil spring when it seems to be understood that it was underrated? Or is the stock coil sold now uprated? Is high performance or fast road in the 350lb range? Where does the competition ratings begin?

 

[tdskip]

Hi Scott - they may have addressed the issue but when I used a set on TR6 they had her sitting like a 4x4. Same issue as Richard posted.

Was a common experience based on some threads over as 6-pack. I had to switch to springs from Richard Good to get it sorted (and to be fair I ended up deciding to have her lower) Glad you had a better experience than I did.

In any case more info can only help the new guys, so glad you posted your experience. Hope you are doing well.

 

[pacotaco]

HerronScott - How does your car handle and ride with the TRF spring set?

 

[sail]

This with stock springs on right and stock ride height 20% stiffer on left. Should be level, right?

 

[pacotaco]

HerronScott - How does your car handle and ride with the TRF spring set?

 

[HerronScott]

Hi Scott - they may have addressed the issue but when I used a set on TR6 they had her sitting like a 4x4. Same issue as Richard posted.

Was a common experience based on some threads over as 6-pack. I had to switch to springs from Richard Good to get it sorted (and to be fair I ended up deciding to have her lower) Glad you had a better experience than I did.

In any case more info can only help the new guys, so glad you posted your experience. Hope you are doing well.

Tom,

And as I said my experience was 27 years ago so who knows if it's even the same vendor or what changes have occurred to the part since then even if it is the same vendor.

I bought a lot of parts for the green car after I got it so I wonder if I have a set of circa 1986 TRF springs in storage.

I will note that if you look at both of my cars, the TR4/TR4A has quite a gap from top of the tire to the fender (stock or replacement) when compared to a lot of cars.

Scott

 

[HerronScott]

HerronScott - How does your car handle and ride with the TRF spring set?

Sorry but my experience may be too far out of date to be valid! Last time it was on the road was back in 1994...

Scott

 

[tdskip]

This with stock springs on right and stock ride height 20% stiffer on left. Should be level, right?

Yes, you want the car level for sure. Not surprising that different springs would result in a mismatch.

 

[sail]

I was really just making fun, it looked so stupid but since I had them for a couple years I just put in one side to be sure before exchanging which TRF was good to do.

There are some specs on Goodparts homepage which might help.

 

[HerronScott]

Richard,

Wow! You and Tom weren't kidding about how high those made it stand. You mentioned you thought they had the issue worked out now? Is that the feedback you got from TRF?

Scott

 

[tdskip]

I was really just making fun, it looked so stupid but since I had them for a couple years I just put in one side to be sure before exchanging which TRF was good to do.

There are some specs on Goodparts homepage which might help.

Sorry, missed the boat on that one.