Re-assembling rear suspension - Page 3 - Alfa Romeo Bulletin Board & Forums
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post #31 of 54 (permalink) Old 07-24-2019, 05:52 PM
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Quote:
Originally Posted by Michael Smith View Post
I have no vested interest in being right or wrong, only in understanding the suspension design and the repair process.
The rubber bushing is an extremely interesting piece of technology. It's a really simple piece of kit, but it brilliantly solves a complicated engineering problem: how to design a joint that maintains geometry while allowing for twisting and flex (no matter how rigid a suspension part, there is always SOME flex) AND dampening noise and vibrations while being reliable, low maintenance and economical to manufacture.

The rubber bushing is also somewhat counterintuitive as you pointed out because it does not really allow free movement - but it allows free enough movement within a very small range of motion. But a surprisingly small range of motion is all you need. When you tighten the bolts with the suspension weighted, what you're actually doing is setting the center of this small range of motion.

According to this article on Monroe's website it was invented by Walter Chrysler himself in the '30s...

https://monroeengineering.com/blog/t...e-to-bushings/

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1990 Spider Veloce

Last edited by GV27; 07-25-2019 at 06:31 AM. Reason: spellin'
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post #32 of 54 (permalink) Old 07-24-2019, 06:09 PM
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Thank you, I like that bit of bushing history, amazing how practical and durable vulcanized rubber is.
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post #33 of 54 (permalink) Old 07-27-2019, 01:17 PM
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Just an idea.

Could not the inner arm ends, against the subframe, be held at the correct angle and tightened before the outer bolts are fitted, and then, with the car slightly raised from the ground just enough to fit the outer bolts, the car could then be lowered to the ground and outer bolts tightened on the deck, in the correct position/loading?

As for getting the right arm angles at the subframe end, they could be measured/photgraphed before dismantling.

Any thoughts?
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post #34 of 54 (permalink) Old 07-27-2019, 06:11 PM Thread Starter
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Originally Posted by richardbradford View Post
Just an idea.

Could not the inner arm ends, against the subframe, be held at the correct angle and tightened before the outer bolts are fitted, and then, with the car slightly raised from the ground just enough to fit the outer bolts, the car could then be lowered to the ground and outer bolts tightened on the deck, in the correct position/loading?

As for getting the right arm angles at the subframe end, they could be measured/photgraphed before dismantling.

Any thoughts?
In theory sure, but that sounds a bit too much like a guesstimate that may be somewhat off. Also if the old bushings are trashed your measurements won't be good.

-RL; 1991 Alfa Romeo 164S, 2014 Mercedes Benz E350 4Matic, 2010 Chevrolet Camaro SS, 2008 Chevrolet Silverado 2500HD, 1995 Volkswagen Golf (Race Car)
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post #35 of 54 (permalink) Old 07-27-2019, 07:12 PM
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In theory sure, but that sounds a bit too much like a guesstimate that may be somewhat off. Also if the old bushings are trashed your measurements won't be good.
Surely if trashed old bushing or not, won't the angles recorded on the car on the ground still be accurate? And even if measured off the ground, after subframe removal via the outer bushes, won't even trashed inner bushes not under load revert to their correct positions? There is no 100% fixed angle here - the bushes by their very nature have a degree of play so as long as they are tightened at least close to the ideal should it not all be fine?

Last edited by richardbradford; 07-27-2019 at 07:13 PM. Reason: typo
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post #36 of 54 (permalink) Old 07-27-2019, 08:38 PM Thread Starter
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Originally Posted by richardbradford View Post
Surely if trashed old bushing or not, won't the angles recorded on the car on the ground still be accurate? And even if measured off the ground, after subframe removal via the outer bushes, won't even trashed inner bushes not under load revert to their correct positions? There is no 100% fixed angle here - the bushes by their very nature have a degree of play so as long as they are tightened at least close to the ideal should it not all be fine?
In theory yes, but IMO a margin of error exists and if theres a way to avoid that which could significantly affect longetivity thats the best route. In mean in theory you could get 4 wood planks as well, drive the car up on them that will give you a few inches to work with to wiggle under there and torque them down.

Or do it your way and then when you bring the car to be aligned have the shop loosen and re-torque.
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-RL; 1991 Alfa Romeo 164S, 2014 Mercedes Benz E350 4Matic, 2010 Chevrolet Camaro SS, 2008 Chevrolet Silverado 2500HD, 1995 Volkswagen Golf (Race Car)
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post #37 of 54 (permalink) Old 07-28-2019, 03:18 PM
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I've not used a spring compressor but it seems to me that this would work. If you can measure the spring length at normal ride height just use a spring compressor to achieve that length and bolt the suspension up and torque it.
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post #38 of 54 (permalink) Old 07-28-2019, 03:37 PM
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What a brilliant idea! Genius!
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post #39 of 54 (permalink) Old 07-29-2019, 08:30 AM Thread Starter
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I've not used a spring compressor but it seems to me that this would work. If you can measure the spring length at normal ride height just use a spring compressor to achieve that length and bolt the suspension up and torque it.
As someone who has used a spring compressor this is a terrible idea.

First off once you compress the spring you would still need to jack up the corner you're working on to the spring as the damper doesn't compress with a spring. Secondly external spring compressors which is what you'd need to use are ultra dangerous and can result in serious gruesome injuries should it slip off. I say this because I have actually seen this happen more than once. There are some better ones out there these days but its not a quick simple tool to use inside the strut tower.

This is a problem that can be solved by driving the car up on 4 double wood planks, or hitting a local shop, or 4 jack stands under the hubs, all of which are faster and significantly safer.
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-RL; 1991 Alfa Romeo 164S, 2014 Mercedes Benz E350 4Matic, 2010 Chevrolet Camaro SS, 2008 Chevrolet Silverado 2500HD, 1995 Volkswagen Golf (Race Car)
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post #40 of 54 (permalink) Old 07-29-2019, 01:18 PM
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Rougue Leader, you are right. I totally missed the element that the damper will remain fully extended. Glad you pointed it out before I tried it and had one of those 'Duh' realisations. Would be confident the compressors wouldn't slip off as they would hook around the curved bottom of the strut and the spring coils but the exercise itself would be totally pointless, as you have correctly pointed out - unless something like a bottle jack was used to squash the damper too - wouldn't lift the car with the spring compressed.

Personally not too keen on the plank idea stability wise so have got round it here by buying a pair of wide car ramps to safely raise the rear wheels enough to gain bolt access, while the front can be raised with a trolly jack and axle stands. Problem solved, at last.
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post #41 of 54 (permalink) Old 07-30-2019, 05:31 AM
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That's a low pressure gas strut just btw. You can lift those by hand. Even high pressure gas struts exert very little pressure.

As for the spring compressor slipping well so can a jack. The spring is restrained anyway. It's not as if you'd be dealing with a compressed but otherwise totally free spring.

The main reason not to use a spring compressor is that an ordinary jack could be used instead. The key element either way would be to know the ride height you need to simulate.

Easiest would be to torque everything up and then have the suspension loosened and retorqued while the car was on the type of lift that lifts the car by the wheels.

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post #42 of 54 (permalink) Old 07-30-2019, 06:54 AM Thread Starter
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Easiest would be to torque everything up and then have the suspension loosened and retorqued while the car was on the type of lift that lifts the car by the wheels.
Agreed, unfortunately since most of us don't have that its more of a how much money do you want to spend to do that part?

Or just had another idea, I have a car trailer with an open deck, can drive the car up on it and do it that way as well.

-RL; 1991 Alfa Romeo 164S, 2014 Mercedes Benz E350 4Matic, 2010 Chevrolet Camaro SS, 2008 Chevrolet Silverado 2500HD, 1995 Volkswagen Golf (Race Car)
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post #43 of 54 (permalink) Old 07-30-2019, 07:51 AM
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No need to make it difficult.

Put it all back together, keep bolts just enough loose. Either jack up rear end (from middle of rear) and put jack stands under hubs to compress suspension like it is on the ground (be careful though), tighten up everything to spec. Or put wheels on, put blocks under wheels and tighten up on the ground.

No fancy lifts etc...
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post #44 of 54 (permalink) Old 07-30-2019, 08:41 AM
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Do not keep rear subframe bolts to chassis loose. Tighten those up to spec. Just leave all the suspension arm bolts loose. :P


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post #45 of 54 (permalink) Old 07-30-2019, 12:03 PM
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You don't need to leave any bolts loose. When you have loaded the suspension accurately you can back off and retorque the bolts and the bushings will release and reset as you back off the bolts.

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