Independent Rear Suspension Pros/Cons

Should I install an Independent Rear Suspension in my Ford 47 Pickup truck?
I have been told the major advantage of an IRS over a solid axle has to do with the overall stability of the vehicle in different road conditions. These conditions may be uneven pavement, high speed cornering, etc. Since the IRS allows either side to rise or fall "independently" of the other side, the frame ( and therefore the body, occupants and center of mass ) remain in a relatively constant location. This leads to the vehicle being more stable.
Any Thoughts ?

 

I wouldn't run an independent rear unless I was going to run an independent front.

One of the cons is maintence, the more moving parts you got the more moving parts you have to replace.

 

I personally don't like independent suspension in anything that didn't have it originally. To me that stuff says "street rod". My .02 One of my winter projects is replacing the covair (independent) front end in my deuce.

 

I had a friend that installed a Corvette independent rear in a '32 pickup. It had a dropped front axle for the front. It road pretty good but was hard on rear tires. We never could figure out why.

 

IRS ? on a traditional hot rod sight,.... sometimes, ya' just know how something will turn out.

 

Chef Mike- Sounds like you answered your own question. I've owned seven Corvettes, one XKE, and one XJ6. All had independent rear suspension. These cars were well suited for IRS. Trucks are designed differently so they can handle a rear payload. Seems like a waste of energy in my opinion unless you are able to install a frt suspension that justifies the reason behind it all.

 

The following are OPINIONS, and they are of course like...

The basic theory you summarized is all well and good.

Implementing the theory is where all the sticky bits trip you up.

IRS benefits: rough-road ride, rough-road handling, smooth-road/track handling in cars light enough (and where the suspension bits are light enough) for the sprung/unsprung weight ratio to matter.

IRS deficits: complexity, cost, effort involved in getting it right.

IRS with a beam axle in front doesn't make a lot of sense IMO.

Serious chassis people would say that your '47 frame is too flexible for the word 'handling' ever to enter the discussion.

But if you feel like a diving-into-the-deep-end sort of project, two or three hours of work will pull the entire front and rear suspensions out of a '70s-80s Jag XJ, and given some careful fabrication it'd probably all work just fine. One of those 80/20 jobs, the first 80% takes 80% of the time available, the remaining 20% takes the other 80% of the available time and effort.

Not optimal for hauling big loads, but that's mainly a function of the springs, it's all fairly beefy. Depends on how you plan to use your vehicle. And it brings some pretty decent brakes and steering along for the ride.

 

I have an old 420 Jag IRS in my '35 along with a period Holden IFS (Similar to Corvair), upgraded from box to R&P . Been on the road now 5yrs and 30K later still going strong, rides and handles well as I added F&R sway bars. If you do carry a load, use leaf springs over coils any day. If you go Jag IRS, use the IFS F/E as well, you won't be disappointed.

 

Very good points thanks!

 

Thanks for your input

 

Early on in my '50 Suburban build I was planning on just going later-model rear end and keeping the straight axle up front. Saves money, gets the project done and driving sooner.
Then a friend called...... said he had a 84 Vette rear for cheap. Like $150 cheap.

Well, one weekend later I had it installed and it's still in there. 5400 miles so far, no problems!

Of course this necessitated a call to Steve at Industrial Chassis to go IFS as well.

One downside to IRS is NO TOWING. So I use my other truck instead.
The Burb rides sweet and handles well. Tire wear is great, had no problems aligning it.
YES it's street-roddy, but I engineered and built it myself.

 

I put a Corvette under my 41 sedan delivery in my street rod days and a few Jags for friends. Once I got over my street rod diversion and back to my roots, I've never looked back and I don't miss them at all.

Unless you are building a road racer, I don't think that they are worth the cost and effort especially on a truck. Without the weight, an empty P/U truck will probably be a rough rider anyway.

 

Very cool ! I plan on installing a IFS II Mustang so I was exploring the option for the rear. Thanks for the feed back

 

Why can't you tow with IRS? I am really interested in understanding that statement as I am currently planning a '50 International build and IRS is on the list (IFS from jag is perfect for the truck, and it seems like buying a complete car for not much more $$ and using the LSD IRS gets me everything I want for both axles). It looks like lots of newer trucks/SUVs now have IRS, and with beefy mounts and beefy trailing arms on the Jag IRS I don't see why towing would be a problem.

What am I missing? Some googling turned up reports of the trailer pushing the back end around? Is it just overall strength (towing capacity)? Or excessive wear to the inside of the tires? There are also "Air Springs" that provide load leveling/etc if I found I needed to tow or stack up heavy loads in the bed on a regular basis: http://www.airliftcompany.com/products/air-springs/airlift-1000

I am building a DD truck, so it needs to be able to be used as a truck, and towing a sizeable load (5-6k lbs) is something I should be able to do, and it isn't obvious to me why a IRS would prevent me from towing.

Thanks, Michael

 

I suspect it's a combination of forces while slowing down and cornering. I was told not to do it, so I don't.

 

i'm not a big fan of IRS although I do remember see a real nice 29 Sedan Deliver back in the 70's that had a jag rear and it did look cool,,,but they just ain't really traditional.

It is however your truck and if that's what you want ,,go for it! HRP

 

I am somewhat of a fan of IRS...for some applications....even the occasional pickup truck....but wanting to tow 5 to 6 thousand pounds with Jag or Vette IRS is not a very good idea, IMO, of course. A 1 or 2 thousand pound trailer would probably be okay...but I would think that would be the upper limit for several reasons.

Bottom line, the cars from which these units are sourced were NEVER intended to carry loads like you want to have the capacity for. There is no rational reason to think that when transplanted into a truck chassis they suddenly become stronger in any way......handling, load capacity etc.

Now, if you just want a good riding light duty pickup, used more like a car than a truck, there can be a case made for that.

Ray

 

Sure, but I don't want to kill myself by having my trailer push my truck off into a ditch / stream / cliff or something

 

Maybe someone with actual experience or knowledge will chime in here on the use of a IRS for towing. I'm currently building a 1955 ford panel. Installed a 1997 Lincoln Mark VIII IRS in it and I am very interested in this towing issue. My only issue so far in this swap is the width of the IRS is approx 4" wider so it is causing a minor wheel and tire size issue.

 

Do it!!!! A chromed out one looks bad ass, like a timepiece. If your trendy, no, the trend has moved on. That goes for the MMII front too.

A 47 Ford P/U . . . I would cherry everything out, chrome jag & MMII, 16" 5-hole dish mags, & a BROWN base patina paint job. Thats what I would do.

The current trend here for a 47 Ford P/U: Stock & the right stance(lowered a little).

 

In the overall scheme of things most hotrod trucks are never going to pull a load bigger than a teardrop or 12' Scotty trailer and carry anything heavier than a 392 Hemi in the bed. Since most any 50s sedan can handle both these jobs, IRS or not, I wouldn't worry about it.

 

if your plan to tow, go with a corvette. jags & vettes IRS both go for about $500 usually cheaper for the jag.

 

At least you are using a unit from a fairly heavy car. But for anything more than a couple hundred pounds tongue weight, I would strongly recommend a load distributing hitch. Rule of thumb for stability is 10% of gross trailer weight on the tongue.

I DO NOT have extensive experience towing with IRS, actually none that I can readily recall, but I DO have extensive towing experience using SUV's and 3/4 ton trucks, 18ft dual axle trailers and vehicles weighing as much as 5000 ibs. So, gross trailer weight at or above 7000 ibs. Even with a conventional rear axle and leaf springs, lighter weight tow vehicles so equipped are marginal, at best for such loads.

Ray

 

And what would the reasoning be?

 

If one lives in the Pacific Northwest he can see plenty of Corvettes pulling ski boats every summer weeked. It's all in how the rig is set up.

The good and bad on an independent under a rod or a truck"

The good, as stated previously, Usually a great ride and better handling plus a bit of Bubba factor points thrown in for good measure.

The bad, Usually quite a bit more expensive, if you loose a wheelbearing or other rear axle piece on the road you may end up with a serious tow bill or repair expenses. Or you may be stuck for most of your vacation time waiting for parts or repairs. it's not like going to any automotive machine shop and having a bearing pressed off and on an 8 or 9 inch Ford rear axle shaft and throwing it back in the housing and on down the road. Or pulling a third member out of something in the wrecking yard in Podunk Junction and sticking it in the truck in a parking lot and being off down the road in short order.

A well cared for rear end probably won't crap out on the road but keeping things simple helps with being able to make repairs in an expedient fashion at a fairly reasonable cost in time and money.

Don't get me wrong though, I'm not a hater of independent suspension front or rear. I'm tired of arm wrestling the 48 and loosing and that is why it is getting an independent front with a power rack and pinion. Going to Doc in the Box with chest pains and then finding out that they are because every muscle in my chest was strained from putting a 500 mile day on the 48 and having to man handle it every inch of the way was enough to convince me. At one time I was going to hang a C-4 front and rear suspension under the 48 but now it gets a MII front and leaf spring rear and that's good enough.

 

Just where did the OP say he was pulling a trailer? HRP

 

pass on the indipendent rear , most are ugly without a lot of mods .. your 47 was born with a cool rear anyway....just my 2cents

 

And sometimes,..... you can be totally wrong,...

 

I hijacked the thread a bit by asking about towing with an IRS. OP doesn't care, as far as I know

 

They're actually not that bad, the Jags use all regular part number bearings that can be had at most regular parts stores. And more and more cars have them so more and more mechanics are familiar with them.