Front a-arm & suspension weight discussion

Suspension and other discussion

Front a-arm & suspension weight discussion

Postby CMS-GT4 » Sat Nov 08, 2008 8:23 pm

So I was oping someone could shed some light about how these a-arms functioned. I am interested in making the suspension lighter, but I am looking for easy replacements of certain components first before trying to create new ones.

The 185 a-arm is very different from these other cars, but I am not sure why.

Here is the The st185 a-arm. It has two pivot points. Can anyone elaborate why? I have been wondering if travel and strength are the reasons the a-arm is designed the way it is with two chassis mounting pivot points.
Image

St205. This setup uses a single bar like the sw20 although there are many other components at play here.
Image

st231 Celica. It looks like this a-arm would almost be compatible with ours but the secondary mounting point looks strange. Seeing this is what made me wonder about suspension travel in rally. I wonder how much lighter this is vs our a-arm and what it might take to convert it.
Image

sw20 Mr2. A single bar system. I am not sure if its cause of less weight that they can get away with this simpler arm. I have been wondering if this could be swapped over on the 185 w/o ill effects on the suspension and safety.
Image

Thoughts, insight?
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Last edited by CMS-GT4 on Tue Nov 25, 2008 11:40 pm, edited 1 time in total.
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Postby RedCelicaTRD » Sat Nov 08, 2008 9:25 pm

All suspensions will have two mounting point to the body for the control arm (or a-arm depending on your nomenclature). If they only had one point the hub would be able to move to easily under force. The MR2 pic is not complete, they have a torsion bar that connects to the main arm, and then goes back to the body. The st205 uses the two bars also, they then bolt to that adapter plate and then to the hub. All those arms function about the same, they simply go at it in different ways. You best bet would be to copy the stock design, but make it out of rods (like the rear suspension) instead of one large stamped piece.
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Postby CMS-GT4 » Sat Nov 08, 2008 9:31 pm

I see. I am starting to think there can be no simple swap option. It is likely something that will have to be fabricated.
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Postby Denver_whiteST185 » Sun Nov 09, 2008 11:08 pm

i think the only decent thing to do with the front A-arms is to remake them out of lighter alloys, but your going to loose strength unless you spend alot on a very high strength alloy. since the front a-arm deals with both front, rear, and side-to-side loads, i would think that would be a bad idea.

i think a better way to remove unsprung weight would be to make the three rear suspension arms on each side out of high grade aluminum (at least the longer rear trailing arms). they would be relitivly simple to machine or cast in comparison to a front a-arm.
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Postby CMS-GT4 » Sun Nov 09, 2008 11:25 pm

From what I weighted the st205 rear lower arm is ~1lb lighter than the st185 version. The others may weight less too but I am unsure as of yet. The issue is they are longer than the 185 part so you will need to swap them all and possible the rear 205 axles as well. From what i compared and read on the 205 data, I have concluded that it will also increase the rear track by 20mm on each side.
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Postby gtfourdreams » Mon Nov 10, 2008 9:43 pm

hmm.. are you trying to loose weight just from the suspension? or in the car entirely?

because just from personal experience, the heaviest thing on the car is probably the engine/transmission combo. especially that transmission. there are a lot of engine/transmission brace brackets that are quite heavy. also the manifolds themselves are pretty heavy. that transmission housing is very heavy also. i think if you were going to replace parts with lighter materials, i would work on those first before pulling the suspension apart.

but if you're looking specifically at the suspension, yea the damn thing is overbuilt. good luck. :P
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Postby Denver_whiteST185 » Mon Nov 10, 2008 10:46 pm

well, unsprung weight (mostly suspension, wheels, and brakes fall in this category) make a much bigger difference when weight is removed than when sprung weight is reduced (everything sitting on the suspension)

The engine/transmission is extremely heavy, but your not going to be able to reduce much there without it being costly. exhaust, intake piping, stripping out unnecessary stuff like the charcoal canister and EGR system (ABS and A/C if you don't care) will only go so far, and most things beyond that will be pricey unless you have access to a machining shop.

some brackets could be easily machined from some cheap aluminum stock, but once you get into anything needing to be cast or forged, it gets expensive fast for one-off parts.
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Postby phattyduck » Tue Nov 11, 2008 10:07 pm

CMS-GT4 wrote:From what I weighted the st205 rear lower arm is ~1lb lighter than the st185 version. The others may weight less too but I am unsure as of yet. The issue is they are longer than the 185 part so you will need to swap them all and possible the rear 205 axles as well. From what i compared and read on the 205 data, I have concluded that it will also increase the rear track by 20mm on each side.
If you swap rear ST205 lateral links (suspension arms), you will need the ST205 axles. The rear track is increased, but I don't remember by how much. It would work quite well on a widebody ST185 - no need for spacers to get the right fender gap and no extra pressure on the wheel bearings. I had to roll the fenders on my Camry Alltrac just to fit the stock wheel/tire combo without rubbing.

As for the A-arms... the Celica has a very standard style a-arm in the front. If anything, I would ADD extra metal to it to increase its strenghth. The aluminum front arms for the WRX/STi increase performance slightly for the decreased wieght, but most of the performance improvement comes from increased stiffness. Stiffer bushings would also help in this regard. Remember that only about half of the a-arm wieght is unsprung.

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Postby Roundy » Fri Nov 14, 2008 5:49 am

i too have ummed and ahhed about something like this.

I think Chrome-moly would be a good material to use.

Very light and exceptionally strong.

When i took my arms off to change the bushes i was surprised by how heavy they were.

Another advantage is you could try to make them adjustable for caster as well :wink:
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Postby RedCelicaTRD » Fri Nov 14, 2008 7:31 pm

Here is an example for a Focus.

Image

If someone made something like this, then you could make an adator for the ball joint like the kind that is used on tie rod ends. Just a simple tapered insert and a bolt.
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Postby CMS-GT4 » Fri Nov 14, 2008 8:10 pm

I would be interested in these if we could get them made for a fair price. I like the idea of caster adjustment especially since caster plates are already so expensive.

Anyone got the hookup to get these made?
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Postby $200GT-4 » Sun Nov 16, 2008 4:39 am

If you could get tubular arms like that made, get them made a little longer to increase the front track width. These widebodies have a lot of fender to fill and given the understeering tendencies I think an increased front track width would be a godsend. Of course you'd need some upper camber plates, but you'd start off with some camber from the get go and be closer to where you really want to be in terms of alignment. The 205 fronts use what's called a super strut suspension, it's better than the straight McPhereson crap on the 185 in that the camber angle doesn't change so dramatically with suspension travel, of which there is a lot in this boat. The other (not MR2) arms are the same design as of my AE111 Trueno and I hate them. They're a pain to install, they look retarded, and worst of all nobody makes poly bushings for that one in the back. I really don't know why that design ever came to be, it looks like it'll let your toe bounce around under hard driving as well.
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Postby CMS-GT4 » Sun Nov 16, 2008 4:43 am

I don't want a wider front track. I fill my front fenders with lots of tire. I would have to run less tire and smaller wheels if I had a wider front track.

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Postby $200GT-4 » Sun Nov 16, 2008 6:04 am

You could pull the fenders out more. . . just a thought. I'm assuming with that wide of a wheel that the offset is somewhat conservative thus scrub is not an issue?
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Postby CMS-GT4 » Sun Nov 16, 2008 6:08 am

38et. No issues so far.
I can't imagine that just by making a longer a-arm that you can widen the track too much. Would you not really just be adding camber since the strut top is still in the fixed oem position and the axle isn't getting any longer.

I think if you swap over the the camry spindle like gtfour77 did you can increase the front track since the hub seems to come out a little more. He modified his front fenders since he runs 315s all around.
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