Why torsion bars?

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Pskhaat

Pskhaat

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What was the reason that Toyota for the IFS 100 decided to go to torsion bars for front suspension components instead of coil-overs (for instance)?

Do you think it's simply because they wanted a consistent way to have a ride height adjustable system? It's supposed to be more durable, but I can't really tell why that would be any better/worse than other mechanisms.

Please exclude the obvious ``should have done live axle'' because it's blazingly obvious they should have :)
 
Who really knows why Toytoasan used torsion bars on the 100 series.

But here are a few suggestions

The setup works well on the lighter Hilux (not sure what you call it in US) so why not keep it for the 100 series so to keep parts simpler

The coil over (used on 3rd gen runner, 90 and 120 series) does have probs with lower bush wear and durability. Perhaps they (Toyota) know this and thought that the heavyer 100 series would not work well given this problem

Can use the same torsion bar for all engine/gearbox variations, just wind up/down the torsion bars to get the ride height (ex factory) correct - simpler parts taht way

Just a few thoughts running thru my head

:)
 
The hilux pickup is the working truck of the developing world, and it still uses torsion bars up front w/ rear leaf springs. A few years ago when travelling in N. Thailand, I stopped by a Toyota dealer and took a look underneath the hilux tiger crew cab TD they had up on ramps. Low and behold, the chassis is exactly the same as on the US-spec '85-89 4runners except the steering wheel is on the opposite side. T-bars up front, rear leafs in back, recirculating ball steering w/ idler arm (not rack & pinion like the taco/tundra).

The 100TD has different t-bars than the LC100 V8 or the LX470 V8, so it's not a 'use the same t-bar' issue. They aren't prone to sagging like coil overs, and take up a lot less space. Easier to adjust vehicle height, too. Don't overseas LC's and LX's have different clearance/wheel travel specs?
 
They have never used it since the 100. I think that tells you what Toyota thinks of torsion bar IFS.

It's advantage is simplicity but the coilover is so much better, imo. I think it's the only mis-step in the 100. Well, it works fine so I won't call it a mis-step... but wish they went with a better design.
 
I think when Toyota designed the 100 Series maybe it was in 1995 - the truck came out Fall of 1997 for the 1998 model, so that is a conservative guess that it took them 2 years to design, test and full production. So in the mid -90's no one had coilovers for trucks. Coilovers probably back then was in very early stages for heavier vehicles. I am not sure if production cars were using them, maybe high end cars but for the most part it was a macpherson strut for cars. Race cars probably had coilovers but not heavy trucks. (heavy being relative).

The Chevy's and the Fords were all using Torsion bars. So maybe also, the focus group wanted a softer ride like the American SUV's, they were not going off-road anyway, just to the mall and soccer practice. The same focus group probably want it to ride like a mini van. :grinpimp:

I think that coilovers didn't go main stream until late 1990's maybe even later. Also, Toyota had Ivan Stewart running around the Baja with a fully independent suspension race truck with torsion bars IIRC. Maybe they have some data from that.

There are some photos of a military truck with (small) coilovers and I am not sure if the torsion bars are still there for additional support. I think Drexx has some photos of them in his website. I did talk to a company in UAE that will sell coilovers that will fit in the current a-arm configuration but they recommend keeping the torsion bars at the same time, also the $2,000 price was a bit steep. I was thinking at the time if I could get rid of the torsion bars and use coilovers, I can use a Marks Adapter crawler gears - the 100 Series can't use this said crawler gears because it goes where the torsion bar are (towards the rear of the vehicle) - I would also have to modify the floor and gas tank too but .. that's another thread in itself - Slee has photos of the install on the Short Bus so you can see the modification needed to do this.

All though it would be nice to have coilovers, you can tune it better and very simple like FirstToy said but we would have to get new A-arms made since as it is the OME shock hits the upper A-arm at full droop. Also probably will need new shock mounts top and bottom - there isn't much room at either end.


"So that's that" :cheers:
 
I think it's interesting with the OZ A-arm problems when comparing it to other counries. I've heard everyone justify our lack of problems here because we don't use our trucks hard here in north america but there are those of us that run the rascals pretty hard w/o A-arm complications. We just don't have the TD sitting up front. :flipoff2: But EL_3grab brings up a very interesting point: Why don't we see problems in the middle eastern countries or the rest of the world for that matter? I would think the dynamic stresses placed on jumping a heavy vehicle as commonly done in countries like the UAE would far exceed the extended periods of lower stress that the OZ overloading situations produce. We've got guys on here like Bongani and several others in Africa and they don't report problems either. Why just OZ? I realize it's linked to the TD engine but the rest of the world has it too, just without reported incidents of a-arm failures it seems. :confused:
 
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Great information everyone! Just more a reason we should have had a 105 series here. At the end of the day, are we really that limited by the tbars? I would guess no, but the design geometry certainly does appear to be better than how Ford & GM did theirs as it is tucked well into the frame.
 
tabraha said:
Why just OZ? I realize it's linked to the TD engine but the rest of the world has it too, just without reported incidents of a-arm failures it seems. :confused:
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In Australia you've got two dynamics working against you. One, of course, is the heavier weight of the diesel engine. But the other, and far more important, is the nature of roads in the Outback, if you want to call them roads. We're talking about thousands of kms of harshly corrugated tracks, and the corrugations are the killer. Drive across the Simpson Desert with an overloaded 100 at 60 km/h on those corrugations, and there's your problem. These kinds of conditions don't really exist in any other part of the world, AFAIK, even in the Middle East. Yes, they jump dunes, but that's sort of a weekend hobby type thing, where they're probably not overloaded 1000 pounds past GVWR, and a dune being jumped is a single dynamic event that is more likely to cause some kind of immediate catastrophic breakage (like a diff), then the constant pounding that is causing these A-arms to gradually tear at the weld seam.

My $0.02,
 
Good insight Derek. One of the things that I don't understand is that it seems to me that in this scenario with loading the vehicle way beyond the GVWR that this situation is primarily a dynamic that would test the strength of the REAR axle far more than the T-bars up front. I can see a portion of the weight affecting the front if it's all in the cargo area but tongue weight should reduce the stresses if anything on the front suspension and affect the front minimally if the weight is balanced well.

I wonder about all of the hoopla in the semi-floating rear axle thread now looking at all of the overloaded vehicles in OZ and all we hear about is the a-arms. That SF must be pretty darn good.

Does anyone know what the weight difference is between the 1HZ-FE and the 2UZ-FE?
 
tabraha said:
Good insight Derek. One of the things that I don't understand is that it seems to me that in this scenario with loading the vehicle way beyond the GVWR that this situation is primarily a dynamic that would test the strength of the REAR axle far more than the T-bars up front. I can see a portion of the weight affecting the front if it's all in the cargo area but tongue weight should reduce the stresses if anything on the front suspension and affect the front minimally if the weight is balanced well.

I wonder about all of the hoopla in the semi-floating rear axle thread now looking at all of the overloaded vehicles in OZ and all we hear about is the a-arms. That SF must be pretty darn good.

Does anyone know what the weight difference is between the 1HZ-FE and the 2UZ-FE?
Click to expand...

HDJ100: 2585 kg. UZJ100: 2270 kg,
both Euro spec with AHC, navi, etc.
 
AUS spec curb weights for the GXL are:

Petrol Auto: ~2345Kg (2UZ-FE)
Diesel Auto: ~2348Kg (1HZ)
Turbo Diesel Auto: ~2530 (1HD-FTE)

Difference between TD and Petrol GXL is 185Kg (408lbs)

The Sahara version adds another 350-400lbs more.
 
tabraha said:
Good insight Derek. One of the things that I don't understand is that it seems to me that in this scenario with loading the vehicle way beyond the GVWR that this situation is primarily a dynamic that would test the strength of the REAR axle far more than the T-bars up front. I can see a portion of the weight affecting the front if it's all in the cargo area but tongue weight should reduce the stresses if anything on the front suspension and affect the front minimally if the weight is balanced well.
Click to expand...

Tad, I think you're correct, but also remember that a lot of folks out there really load up the roof, which will put some load on the front axle, though again, still most on the rear.
 
Pskhaat said:
What's the Sahara version include?
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Sahara is the luxo version, much like what we get in the States. Lots of electronics, little motors, soundproofing, leather, and other junk that adds weight.
 
Sahara includes: NAV, Variable Gear Ratio Steering, Refridgerated cooler box, fog lamps, wood console, power tilt steering, F&R climate control, AHC suspension.

The GXL also does NOT have:
VSC, std power moonroof, Trac control, power seat, leather interior. These features are added on the VX model.
 
hoser said:
Variable Gear Ratio Steering, Refridgerated cooler box
Click to expand...

Both very cool and we're all for sure envious.

wood console, power tilt steering
Click to expand...

<sarcasm>
Well, when I'm driving I sure do like to have the feel of hardwood flooring in my vehicle. Makes it SOOOO luxurious! Also, can't tell you how often my arm hurts from adjusting that annoying steering wheel angle.
</sarcasm>
 
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