TR4/4A Which TR4a is better - IRS or solid axle?

[tdskip]

I know the solid axle cars are preferred for racing, but how about daily use with occasional fast road use (quite fast)?

 

[TR3driver]

Stock or modified ?

 

[tdskip]

Solid axle stock, IRS has poly bushings and adjustable TA mounts.

Edit - Anti-sway bar on both up front.

 

[HerronScott]

I drove mine daily for 5 years and 75,000 miles and enjoyed every mile.

I've never had a solid axle TR4/4A to compare it to though.

Scott

 

[TR3driver]

Well, I've never driven a 4A at all, either IRS or without. But the IRS is basically the same as the Stag & TR6; both of which seem way too soft and vague in the rear for truly spirited driving, to me.

Right after I got the TR3 on the road, before any of the small suspension mods, sway bar or even wide tires, I went on a run with the club. The fellow behind me mentioned later that he was totally amazed at how well it cornered, compared to his stock TR6. I had fallen a bit behind the group and was pushing to keep up. Apparently, he literally missed a corner trying to follow me!

Of course, the IRS is much better in some situations, rough roads in particular. The ride comfort is also much better. But on a smooth road (and in a similar state of preparation), I'll take the solid axle.

Re: fast, my speedo is clearly wildly off at this point, so pegging it means nothing. But the tach seems pretty close and I've been out beyond redline in 4th OD ... not sure what the PO did to the engine but it runs good!

 

[Bob_Muzio]

The IRS car will be more comfortable, ride wise. The solid axle car doesn't have the complexity of the IRS unit which to some is quite desirable. Given the choice between a solid axle and an IRS model I'd take the solid axle......but then again, I've always had TR4s.
Bob

 

[TR3driver]

but then again, I've always had TR4s.

And a definite tendency to get complaints about driving too fast on motoring tours


(Not from me, of course.)

 

[sail]

Currently the diff is on the workbench, axle shafts are painted sitting next to new u-joints, diff mounts looked good and are painted along w/ rest of stuff back there, shorter springs are on the way because as you can see in the photo drivers side is too tall with standard springs. Bushings are in painted trailing arms but those s/b heli-coiled, gotta call Goodparts for new hubs and there is something else, what am I forgetting.
So taking into account all the stuff back there on the IRS, the simplicity of the solid axel with its cornering ability, which is better, IRS or Solid?

Mine is.

 

[Banjo]

I vote solid axle. I've owned a TR4A solid axle, and have had plenty of seat time in TR6s. Both are great, Both have definite advantages, but I like the feel of that solid axle. the IRS is cushy, and comfortable, but I like the road feel in the solid rear end. not to mention a lot less stuff to keep maintained.
it really all depends on what you're looking for from the car.
And like previously mentioned, Poly bushings, better springs and the like can greatly improve the stiffness in the rear. but that all costs$$$$

 

[vivdownunder]

I've not had a 4A, but to compare, have owned a solid axle TR4 and an IRS TR5. Both cars had standard rear suspensions.

The IRS in original form was a primative affair. Diff mounts broke, sliding half shafts jambed until the (costly) Nissan based aftermarket kits became available, and the lever shockers weren't really suited. Also, when loaded two up/luggage/full tank for a trip away, the back wheels squatted at a crazy angle. It was skittish when driven at a good clip through the hills - always threatening to break loose at the rear.

Handling of the solid axle TR4 was less evil near the limit and maintenance was altogether simpler. That said, it rode like a buckboard compared to the IRS.

Each has it's merits - an IRS can be much improved with $$$ and there are some very rapid, good handling TR6's on the track to prove it.

Viv.

 

[KVH]

I am fortunate to own both, and both are great cars. I found good ones, and made them even better.

I'm a bit partial to the solid axle. Simplicity.

On my IRS, I couldn't get comfortable with all the U-Joints and the sliding half axles, and when I saw what Richard was selling at Goodparts--fantastic CV Axles and new Hubs--I ordered those and installed them.

I also have a Nissan Diff, and adjustable trailing arm brackets.

Finally, with the IRS you may want to strengthen the diff mounting bridges because nearly every article about refurbishing an IRS suggests you do it. All you need is some patience and a good welder.

I love the ride of my IRS; it's like the car is on rails, but I'd credit that in part to the Nissan Diff.

So, there you have it from someone who ought to know. I did a lot of research and learned a ton right here on this Forum, and others have done what I've done.

The point I'd drive home is not to shy away from an IRS if you're willing to give it extended life by giving it the care it deserves.

To repeat, I'm a bit partial to the solid axle, but mainly due to simplicity. Good luck.

 

[glemon]

I have had a solid axle 4A for a number of years and then my current IRS TR250. I agree with most everything that has been said. I have not driven the IRS car a lot yet, and not too quickly because I am still breaking it in. However, the IRS does seem to be a little less firm and a little more "squirrely" than I remember the solid axle car being.

One thing the IRS does seem to do better is put the power down coming out of corners, but then again I have a lot more rubber on the TR250 than I did on the 4A, also if driving at 8/10s or so in a bumpy corner the IRS will have much better feel and jump around less, the solid axle cars do ride somewhat like a buckboard.

I have to say, I like sporting cars and sporting rides, but the one thing I could never get over on the solid axle 4A was the jarring ride on potholes and such, not the jarring to me, but the frame flexing and windows rattling in their tracks, in that regard I like the IRS much better, as you can tell from my comments it is a mixed bag, but on a smooth surface I preferred the handling of the solid axle car.

I too will echo the comments concerns that all the books talk about reinforcing and potential trouble spots with the IRS, no such worries with the solid axle cars, long as your lever shocks are good and everything is bolted down well that is about all it needs.

 

[swift6]

The biggest culprit for vague rear feeling on the stock IRS cars are the soft bushings at the semi-trailing arm mounts. They are way too soft and allow the rear wheels to track differently through a corner. Thus the twitchy feel of the rear end when pushing it. Upgrade those four bushings to a stiffer materieal and it will radically change the way the rear end tracks through a corner. No more twitchy-ness from the rear wheels pointing different directions, and stiffer bushings here won't affect the ride.

 

[CinneaghTR]

Kudos to the independent-minded North American dealers for making this conversation possible. I've never driven an IRS Triumph enough, other than my GT6, but my question to pose in response to the question would be, "Which car are you driving that day?" Good stuff.

 

[HerronScott]

OK, I guess I'm the only one that doesn't see the TR4A/TR250/TR6 IRS design as complex as I've seen a number of references to the complexity of it (or rather the simplicity of the solid axle).

I'm sure it has a lot to do with my first Triumph (and car!) having it and recall thinking at the time what a simple and easy to maintain design. Not that I knew anything about cars at all when I acquired it! It was simple to pull axles and replace U-joints (one of my first tasks) or even the whole axle if needed without disturbing the brakes and same was true of the differential. And at the time in the late 70's and early 80's, spare parts such as axles were inexpensive so you didn't really have to worry about rebuilding them if they failed (which is complex!).

Personally, I'm more concerned with dealing with the TR3's solid axle, leaf springs and shackles than I am the TR4As IRS, but that comes from the experience I know versus the one I don't.

OK, back to Tom's question which is IRS or non-IRS for daily use!

Scott

 

[Marvin Gruber]

For the long haul, my choice would be the non-irs mainly because of fewer moving parts. I have even thought about changing a TR6 over to solid axle. Extra u-joints don't bother me, its the swing arm and mounting that will coming apart in the years to come.I have a stack of swing arms that the shock mount holes are wallowed out. Changing out the rubber bushings are no fun either.

Marv

 

[TR4A_IRS]

Gee, Tom. Are you going to ask "Ford or Chevy" next?

 

[tdskip]

Ha - not trying to just people worked up Ian. I have a decision to make in a couple months...

 

[cheseroo]

If I may interject..... The problem as I see it is that he has one of both and probably needs to shed one. The IRS car has had most or all of the rear end bits freshly rebuilt but I don't think the solid axle car has been touched back there. With 40somewhatever cars in the fleet, I don't think that any one of them will see enough driving to where you will get annoyed by either's idiosynchracies. I haven't been on that rally you do in October so I don't know how hard you guys drive but I can't see it being hard enough that you HAVE to have a solid axle car to do it. I'd say it comes down to which one drives nicer and is prettier. Personally, I'm partial to the blue IRS car.

So there

 

[TR3driver]

I haven't been on that rally you do in October

Which rally is that?