TR4/4A TR4a Live axle vs IRS

[Scotsman]

Other than the axle are there any additional differences between the "live axle" TR4a's vs the IRS models. For example I have read that Triumph improved the hood latches in later model TR4a's and was wondering if improvements were made to the IRS model that were not applied to the live axle model.

My understanding is that the IRS is more desirable but some folks tell me they like the "sporty" feel of the live axle more. Comments

 

[sail]

Seems to me simpler is better, lots of parts on the IRS. But then I prefer the 4 over the 4A (hope my car didn't hear that.)
No other differences afaik, never driven another TR so can't say about handling.

 

[trrdster2000]

Richard is right, lots of parts is correct. I think someone counted them up a few years back and the total was 94 different ones. I know the change would involve cutting the frame off behind the sets for one or the other.
The ride is a matter of taste, as far as set up for performance, I think the IRS can be adjusted better.


Wayne

 

[titanic]

There are certainly fewer problem areas with the live axle. Hub failures, broken diff mounts, trailing arm studs, binding splines, and u joints provide a lot of entertainment and expense on the IRS cars, that are non-existent on the live axle cars. I don't know if the difference in handling or comfort make IRS worth it.
I have always considered to live axle TR4A to be the best compromise between reliability and comfort.
Berry

 

[tomshobby]

I owned a 1964 TR4 when it was new and put a lot of miles on it and drove it hard. I also had a 1967 GT6 when it was new and drove it hard and made a lot of miles also. This last 10 years I have been driving a TR6 and have put on a lot miles too.

I have found a considerable difference in handling between all of them. I suggest driving both before making a decision. I prefer the solid axle but the IRS has some pluses too. As far as changing from one to the other on an existing car for myself would not be something I would do.

 

[Geo Hahn]

I, too, prefer the live axle -- but perhaps that is because I drove my TR3A for 20 years before I got a TR4. I just like the way you can throw the rear around w/o ever losing confidence that everything is still under control.

The change in the hood latches (assuming you mean the bonnet) I recall are conical locating buffers instead of the flat buffer. Also, perhaps that was when a safety catch was added to the latch - hardly needed on a front-hinged bonnet.

 

[charleyf]

There are body differences between the TR4 and the TR4A. But I do not believe there were any major differences between the body on the live axle 4A and the IRS 4A.
There may well have been a few in production changes within the 4A production.
Charley

 

[Brinkerhoff]

I prefer the IRS ride and handling but just putter around . Does the solid axle car handle better?

 

[Geo Hahn]

...Does the solid axle car handle better?

It handles differently. Most measurements would probably show an IRS handles better. Which is preferable is highly subjective.

My wife's Toyota handles much better than any Triumph but for me the TRs are much more interesting & fun to drive.

 

[jimg]

For all out performance the IRS car is faster. That being said, yes, certain things need to be done when you add grippy racing slicks.
Mine is a '64 body on a '67 IRS chassis. With the latest rounds of chassis mods I used QA-1 double adjustable coil overs on the front and added
adjustable spring perches in the rear with adjustable Spax dampers. With this I was able to corner weight the car to +/- .1% cross weight.
You will never balance a car that well with a live axle.
just my .02
jim g

 

[malbaby]

"jimg"...very interested in some pics of how you did the adjustable rear IRS spring perches, and are your dampers coil over style.

 

[Tybalt]

My take on the TR4A is go with an IRS model if you find one. The TR4 had a relatively stiff "ladder" like frame along the lines of the earlier TR series cars. The TR4A was designed for a semi-trailing arm rear suspension from the start with the solid axle car being a bone tossed to the dealers in the US that complained about the cost difference between the 4 and 4A. To shut them up, the solid axle 4A was bodged together using as much of the IRS frame as possible and the IRS was made an "option" on the US cars only. I seem to recall the price of the option was something on the order of $125 to $150 dollars over the course of the model run. This means that it retains that "wasp waist" set of frame joints close together at the rear of the passenger compartment where the forward section the "waist" would have been used for the trailing arm mounts had it been an IRS car. This is a more flexible chassis than the "ladder' type used for the 4 and as a result, when driven hard the car will be more prone to frame and subsequent body flex than either a 4 or a 4A fitted with the IRS suspension.

By the time the TR250 came out, Triumph basically said that it would be an IRS car only and told those few dealers that were still whining about it, a discount was offered as in they were told "2p off".

 

[glemon]

This is a more flexible chassis than the "ladder' type used for the 4 and as a result, when driven hard the car will be more prone to frame and subsequent body flex than either a 4 or a 4A fitted with the IRS suspension.

I had a live axle 4A and loved it, but agree with this statement. It seemed pretty flexible, I thought maybe it was the rust in the rockers, fixed it, still flexible, part of the reason I wanted to try an IRS car. The live axle is probably better handling as delivered, the IRS has more potential, a rear sway bar does wonders. I have mixed feelings about which is better, the IRS sure puts the power down better out of a tight or bumpy corner, and provides a slightly smoother but by no means cushy ride, but also has much more things that can break and need maintained. Try each if you can, but it can also be dictated by what cars are available to you, a good one with either set-up will be a happier proposition than a rust bucket with the set-up you decide you prefer.

 

[KVH]

I've owned both for years and have substantially rebuilt both. My IRS, however, has a Nissan rear end from a Goodparts setup.

I'm just saying, on balance, I think the car I'd hunt down and buy again without concern would be my TR4A live axle. Now, for an IRS, if reinforcing and upgrading the rear differential mounts is something you're willing to do, as I did with my IRS, then I'd recommend that model, TR4A IRS, just as highly. Reinforcing requires removal of the diff and rear axles, and welding support pieces in six or eight places: front bridge mounts, rear bridge mounts, rear spring turrets. and possibly the rear bridge bracket itself. See attached pics. I'd really like to think TR4A IRS models will be saved and preserved with upgrades as noted.

As for other differences between the two TR4A models, I'm not sure I know of any other than the frame, naturally. Comparing to a 4 is another matter, and then comparing to an early 4 is still another matter.