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Old 7th June 2018, 01:14 AM
Beachworm Beachworm is offline
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Default Other ideas for lifts

I've been doing a lot of thinking and research. The idea of lifting a Subaru, particularly a Forester came to life when they had strut suspension both front and rear. When the multi-link rear was introduced in 2009 it seems that the spacer approach was modified to suit and it still remains a cost-effective way to lift except that it doesn't also lift the rear diff.

Has anyone given thought to doing it differently? There are heaps of options for lowering with lower control arms, adjustable toe links, adjustable coil-overs etc. but nothing for lifting except springs and spacers. Is there anyone with engineering expertise and an interest in the marque that has given thought to redesigning the lower control arm and other suspension components in a way that would give a better result?

I appreciate it would be significantly more expensive than spacers but as the SH and SJ models age and more people modify them for off road use given their inherently better traction systems, surely there would be a growing market for a more sophisticated lifting option.

Thoughts anyone????
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Old 7th June 2018, 01:36 AM
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Are you saying the the rear diff is not attached to the 2009 vehicle sub-frame but rather "floats" like a live axle? In multi-link diagrams it looks very solidly attached to me!


As Nachaluva already said in another thread:
Quote:
Originally Posted by NachaLuva View Post
Whether you use 1" strut top spacers or raised springs, you are still lifting the body and diff.
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Old 7th June 2018, 01:59 AM
Beachworm Beachworm is offline
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No. The diff and its sub-frame should remain firmly where they are. I'm thinking of a lower control arm that lifts the strut 50mm (removing the need for a rear spacer on the strut or the sub frame) while increasing ground clearance between the sub-frame attachment point and the wheel. The rear upper control arm and the toe link would also need to be redesigned or made adjustable in some way to compensate for the changes in angles. If this is even possible.
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Old 7th June 2018, 02:18 AM
Beachworm Beachworm is offline
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I could have expressed myself better.

What I really mean is that we are using sub-frame spacers to correct a problem created by using lift spacers on the top of the rear strut/coil-over, or whatever it's called. One disadvantage of this fix is retaining the stock clearance under the rear diff. If we start from scratch with rear suspension design and fabricate a different shaped lower control arm that raises the lower mounting point of the rear strut/coilover it could, at the same time, be shaped to give better ground clearance between the sub-frame and the wheel than the standard lower control arm does. The upper control arm shouldn't need modification if the design of the new lower is appropriate. The training arm would need to be lengthened and its shape altered to eliminate the need for a spacer where it mounts to the body (as this also reduces ground clearance at that point though it is of minimal consequence). Adjustable toe links are already available but probably would need to be longer or shorter as they currently only cater for lowered vehicles.

I hope this makes my ideas clearer.
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Old 7th June 2018, 02:35 AM
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All sounds like a very expensive exercise in modifications / redesign / re-engineering to me which would also require re-certification - just go with a strut top lift and be done with it.


I doubt the market is large enough to support it.
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Old 7th June 2018, 02:45 AM
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If you do a 2" lift on a multilink Subaru, by whatever method, you have created a couple of issues that need to be addressed.

First is the alignment. This can be fixed by fitting subframe spacers (like I do) or by using adjustable control arms. The ones that are available now seem to not be very strong, heard of plenty of people breaking them offroad.

Second is suspension droop (how much the wheel drops when you lift a wheel). With the multilink suspension design, droop is limited to start with. By pushing the suspension down 2"" to gain 2" lift, you lose 2" of droop. Dropping the subframe by 2" gives that back. I don't know how else you can keep the lift without affecting the droop as it's controlled by the design of the multilink setup plus the strut itself. Even fitting longer travel rear struts will only have limited effect on the suspension travel in these

Another thing to remember is the rear diff is not the lowest point on a Subaru nor the most vulnerable. It's tucked up pretty high & is a solid chunk of steel. It's probably the strongest part of the car!

It's the engine sump that matters. It's always the lowest point on a Subaru & is very vulnerable. There's only a very thin piece of sheet metal between rocks & the oil pickup. If this is damaged, the oil pump will suck in air instead of oil, the crankshaft main bearings will run dry & will be destroyed in a matter of only seconds. Time for a new engine!

By lifting a Subaru, this is lifted too, and by adding a sump guard you keep it nice & safe

PS: there is no need for a diff guard, the diff is way stronger than the guard that's meant to be protecting it lol. It's like using a tissue to protect a safe haha
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Old 7th June 2018, 02:50 AM
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Quote:
Originally Posted by NachaLuva View Post
Another thing to remember is the rear diff is not the lowest point on a Subaru nor the most vulnerable. It's tucked up pretty high & is a solid chunk of steel. It's probably the strongest part of the car!

PS: there is no need for a diff guard, the diff is way stronger than the guard that's meant to be protecting it lol. It's like using a tissue to protect a safe haha

Absolutely agree!
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Old 7th June 2018, 03:13 AM
Beachworm Beachworm is offline
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I agree. It would be expensive and require engineering certification but as there should be a growing market for such products (there are 3 or 4 different makes of after market lower control arms available for lowering including Whiteline) someone may be willing to wear the development costs to get products to market.

I don't know whether people who lower their cars are prepared to spend more money than off-roaders, but it would be easy to spend 3 or 4 thousand dollars on suspension parts to drop a Forester for tarmac performance handling. Why wouldn't it be a viable option for also lifting one for off-road performance.

I have some experience in design and technology but since retirement I no longer have access to facilities and the certifying engineer I was working with is also retired so I am not in a position to do much myself. I just have pictures in my head of some of these things and I would love to see them made available.

Although I am going ahead with a spacer lift (parts ordered from Nachaluva) I don't like compromises and using sub-frame spacers to correct an alignment issue created by strut-top spacers seems to me to be a compromise and I would like to see someone build a better mousetrap.
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Old 7th June 2018, 03:22 AM
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The suspension droop is an issue I don't have a solution for but I disagree about the diff not being the lowest part. I crawled under my car and took measurements. At standard height the diff is only 15 mm higher than the sump guard which lost me 15mm of clearance under the sump. Once my spacer lift is done (assuming I used 50mm spacers in the sub-frame which I won't - I'm only using 25mm to get some increased diff clearance), the diff will be the lowest point except for the exhaust and because the sump guard will have been lifted higher than the diff, if I'm driving over a large rock that easily clears the sump guard I won't know anything about it until it impacts the diff. Even if the diff is heavy, it is still a casting and therefore inherently brittle and subject to cracking. It will continue to function until all the oil has drained out and I will be looking for a tow.
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Old 7th June 2018, 03:33 AM
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So change line when you pass stone in front so it wont be in middle of car. Many things still can happen there for lifted diffs as well its not that lifted diff is safe, if car changes angles or front lifts or side with that ground clearance changes so you never know.
Put skid plate on rear diff as well so you could hear first as plate touches something and not diff.
My rear diff is highest point still i allways thinking whats happening with car and what i could grab there.
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