Koni insert research

Venom

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Jun 8, 2009
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Thought i'd do a separate thread to my car build because I may not follow through but some information may come out of this which others may find useful.

My suspension travel with BG9 outback shocks and 50mm strut tops on the car. Measurements to top of wheel arch.
On the ground (resting height): 460mm front and rear.
Fully compressed: 420mm front 385mm rear.
Full droop/extension: 545mm front 550mm rear.

All measurements are height from centre of castellan nut to the top of the wheel arches directly above.

145mm total travel in the front and 165mm in the rear. 40mm compression in the front and 75mm in the rear. Up front at full compression there is 60mm to the top of the wheel arch.

Pulled a set of S/H shocks from a car at Jolly's.
IMG_20141101_1725501.jpg


Measuring these from the base of the shock body to the end of the second step after the thread on the piston(?). This is without bump stops.

Front: Compressed length 400mm, extended 550mm. 150mm of travel, the body of the shock (base to weld at top) 355mm.

Rear: 475mm compressed length, extended 685mm, 205mm measured travel. Shock body 420mm.

Now because I have 50mm strut tops whose length I want to incorporate into the shock, it should just be a matter of adding 50mm to the above measurements to give me a baseline to work from.

Front 450mm compressed, 600mm extended.
Rear 525mm compressed, 625mm extended.

Objectives: gain compression, extension (assuming shock is not limiting factor), maintain current ride height.

BG5 koni insert stats: Need info on the fronts. Rears body length 400mm, min length 433mm, max length 675mm, 242mm travel.

BG5 Konis are out of production? Not listed on the Koni website but I can find part numbers.

More to come...
 
Seems there is very little travel on these OEM BG5 shocks…waiting for more info about the Koni's
 
Venom said:
On the ground (resting height): 460mm front and rear.
Fully compressed: 420mm front 385mm rear.
Full droop/extension: 545mm front 550mm rear.

145mm total travel in the front and 165mm in the rear. 40mm compression in the front and 75mm in the rear. Up front at full compression there is 60mm to the top of the wheel arch.
Click to expand...

The front is 125mm total travel. Thats only 5" lol. Back is a bit better at 6 1/2". But still not much. I'd hate to think what mine is lol.

Now because I have 50mm strut tops whose length I want to incorporate into the shock, it should just be a matter of adding 50mm to the above measurements to give me a baseline to work from.
Click to expand...

Not sure if I understand this. Wouldnt the strut top blocks be independent of the strut length? If you make the strut insert too long, under full compression it will hit up against the bottom of the strut & blow the bottom out...

Dedman might be able to help here :iconwink:
 
It's hard to explain.

It would obviously have to be supported around the collar or "bumps" at the top of the insert like any other, so if necessary it would require an extension of the strut body. That's what Ralf at Trutrack did with those Koni's for the Forester on here somewhere. Bump stops would have to be the correct size so it is bottoming out before the strut anyway. That's all a given.

First of all the inserts don't all have the same min compressed length to travel ratio so there could be gains there. That's part of the key to the research. For example the BG5 rear inserts have 30mm more travel than the WRX one but its minimum compressed length is actually smaller. Its utilizing a greater percentage of the body length for travel.

The other been by integrating the strut top length into the shock body size then you open the door up to more travel by utilising say an equivalent % as the BG5 strut but from something say with a 50mm longer body and utilising say 35mm of that in additional travel. It's minimum compressed length could actually be smaller than the stock strut + strut top for a gain in compresseion, but it's fully extended length longer for a gain in extension.

It's a lot of ****ing about for what is at best a 1" travel gain. Yet when you're talking 5 and a bit inches... well hey 6 1/2 is better than average!

The reason why the Hotbits coilovers have so much more travel is because with the external canister they are able to utilise more of the shock body for travel. I just don't have the money for them and can't wrap my head around getting all the measurements right to have them made to spec anyway.
 
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Venom said:
The reason why the Hotbits coilovers have so much more travel is because with the external canister they are able to utilise more of the shock body for travel. I just don't have the money for them and can't wrap my head around getting all the measurements right to have them made to spec anyway.
Click to expand...

Its not very difficult to get the right measurements. You measure the maximum stroke you can get (I have 1cm too much stroke front !), you weigh your car front and rear (ex : 800 kg front/700 kg rear) so you know that on a flat surface with 2 wheels in the air (diagonal spin) you have 800 kg on 1 coil over in the front and 700 kg in the rear. If you have 24 cm stroke front and take some 32,5 N/mm springs, they will be able to be fully compressed (24cm x 32,5N/mm = 780kg). Then you need to have springs able to compress 24 cm minimum. You can't find 48 cm long springs but you can utilize 2 separate springs. Because of that, each spring has to have the compression rate doubled (ex : 1 x 250mm x 60N/mm + 1 x 230mm x 70N/mm gives you a spring length of 480mm and 32,5N/mm rate). For the body length, I measured the stock SG struts (front 38 cm) but for maximum stroke, I decided to go 37 cm body length (1cm gain on compression !). You can take the measurements for the rear and do the same calculations…et voilà !

For the hydraulic settings, I just asked the OEM settings to have a smooth ride when the compression and rebound screws are open so I can stiff the ride by turning them clockwise.
 
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Something else to consider with all this is the working range of the other components of the suspension. For example with my vehicle with a 50mm strut lift and no body lift then the CVs are at maximum working range at full droop, infact with the slight wear in my CV cups the axle just touches the cup when rotating on full droop. Less than ideal.... I also put new ball joints in yesterday as the old ones were shagged. I discovered that the new joints are right at the limit of there flexibility on full droop and any more lift or negative camber would push them past their capabilities. Of course if you have a full body lift then this would not be an issue but I personally like the added clearance for deep ruts.

Just something to consider that might otherwise be overlooked.
 
Yeah I won't get much more droop than what I have. My CVs are already on a fair bit of an angle even though I have the 2" body lift. Even brand new CVs will grind booting up a steep hill.

That would be another tick for coil overs. Have the wheel alignment setup for a level or close to CV joint angle for on the road, and wind it up for offroad. Wheel alignment and tyre wear aren't going to be a big issue on dirt or sand.

Need portalled Subaru hubs:
https://www.proformance.com.au/#!ultra4-ifs-irs-portal-reduction-hub/c1jhj
 
Agreed, coilovers with adjustable ride hight would be a great option. Lot of work though.
Venom said:
Need portalled Subaru hubs:
https://www.proformance.com.au/#!ultra4-ifs-irs-portal-reduction-hub/c1jhj
Click to expand...

For a moment there I though someone was actually making them for Subarus!! That would be the greatest mod ever. Although the 1.92:1 reduction would be way to high. Having reduction would also multiply the torque biasing effects of diffs which would be even more awesomeness. One can only dream....
 
Dedman said:
Something else to consider with all this is the working range of the other components of the suspension. For example with my vehicle with a 50mm strut lift and no body lift then the CVs are at maximum working range at full droop, infact with the slight wear in my CV cups the axle just touches the cup when rotating on full droop. Less than ideal.... I also put new ball joints in yesterday as the old ones were shagged. I discovered that the new joints are right at the limit of there flexibility on full droop and any more lift or negative camber would push them past their capabilities. Of course if you have a full body lift then this would not be an issue but I personally like the added clearance for deep ruts.

Just something to consider that might otherwise be overlooked.
Click to expand...

You are right Dedman.

I didn't want a body lift either but I wanted stroke where most of us put strut lift blocks. And because of 1 cm too much stroke (!), I installed some Heri HD axles front. Now everything works perfectly but I had to take the front sway bar definitely out.

It would be possible to have even more stroke but a body lift would be necessary…
 
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I've located a set of BG5 rear koni inserts. These should be the longest travel Subaru insert. Obviously they're out of production but luckily I found a shop that has some sitting on their shelf and they set them aside for me :) Interesting conversation with the shop though, they have their own database with the Koni insert dimensions/sizes. So they can search based on fully extended, compressed and body length. Only spec they don't always have in their database is the diameter of the insert, if not they have to pull it off the shelf to measure it.

So fitting up koni part number 86101416 (scion or toyota) to my front shock is looking good. That koni minimum length 395mm, fully extended 573mm. My target fully extended length is 600mm to equal my current shock plus the 50mm strut block. So with a 27mm extension added to the shock body with the scion koni (as per Douglass Ferriers thread) I'll get my 600mm fully extended length. Fully compressed will be 395mm (+the 27mm shock body extension) so 422mm, compared to the current 450mm of my stock strut + 50mm lift block, That is a 28mm gain in compression. Not bad, travel up front would then be increased from 150mm to 178mm and would include the deletion of the strut block.

Next issue though is adjusting for camber and caster with the loss of the strut block. I would need adjustable camber plates, although the alloy STI control arms will add some of both. The problem is the strut is going to foul on the strut tower. So a good work around for that would be a coil over conversion kit like this: https://www.ground-control-store.com/products/description.php/II=81/CA=25 With the narrower diameter spring it would create more clearance, and I could actually remove most of the strut spring perch as well.
 
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Have you thought about using full coilovers, not a coilover conversion which might bring attention if a cop had a look
 
I have, but you get no travel gain (they usually have less) and would still need a a lift block with a stock replacement coil over. Unless they're custom, and you have a spare minimum $6,000 to get them made by DMS or MCA.

I have emailed HotBits, I'll see what they say.
 
I wouldn't leave it like the photos in that link. The spring perch on the old strut doesn't hold the new spring, the adjustable perch on the threaded coil over sleeve does. So I think a neatly trimmed strut perch reduced to the minimum needed to hold the coil over conversion wouldn't even be recognisable to anyone who didn't know what had been done. There'd only be like maybe 5mm? left of the old perch, maybe not even that. It'd just look like a normal coil over.
 
Venom said:
I have, but you get no travel gain (they usually have less) and would still need a a lift block with a stock replacement coil over. Unless they're custom, and you have a spare minimum $6,000 to get them made by DMS or MCA.

I have emailed HotBits, I'll see what they say.
Click to expand...

I bought the DT2 kit (4 struts, 8 springs, 4 spacers, 4 top mounts with camber adjustment) US$ 2'450.- except import taxes.
 
Awesome thread Venom!

I find it interesting how we all aim for the same thing but go about it in very different ways! I think you're further along the "build complete" spectrum than I am if your digging this deep into suspension setup!

Looking forward to the outcome!

Cheers

Bennie
 
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