HotBits coilovers

Red XS said:
The front weight is about 790Kg and rear about 610Kg under what I am taking as the lightest driving situation. I'm guessing my rear would be close to yours but the front is a fair bit heavier. A little over 10Kg would be bullbar and extra lights hanging so far forward over the front axle and the rest would be EJ253 and extra chassis strengthening in the SG.

Under full articulation I figure I'm going from 395Kg to 790Kg of weight on the compression front corner, with 35N/mm springs this gives me (790-395)*9.81/35=110.7mm of up-travel. I will reach bump stops before this happens. But let me know if I'm doing anything wrong, I've already had a lot to learn.
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What does the *9.81 refer to ?
 
* is what I use for multiplication, / for divide and 9.81 being Kg to N conversion. It looks like you did Kg divided by N/mm gives an answer in cm, which is easier.

I not 100% sure I'm following all of your calculations, is the Springs rates row calculating an existing spring rate with 254mm long springs?

Currently on level ground my 250mm long 45N/mm springs are compressed to a length of 160mm. This suggests there is (250-157) x 45 = 4185N of force through each front corner. Or 4185 x 2 / 10 = 837 Kg on the front. I think this figure is slightly on the high end, but there's a few sources of error in this method, spring sag, over rated springs, a couple of mm of measurement error ect.

Under articulation, full compression corner, the spring compresses to 75mm and this is with the coils hard packed against each other. This limits me to 82mm of up travel. Force on the compressed corner should be at least (250-75) x 45 = 7875N or 787.5Kg

So I'm estimating the front springs to be supporting a mass of about 790Kg

My plan was to use 35cm long 35N/mm springs which on level ground under an estimated 790/2=395Kg will compress to 35cm-395/35=23.7cm

And under articulation, under an estimated 790Kg will compress to 35cm-790/35=12.4cm

So these springs will allow 23.7-12.4 = 11.3cm of up travel, however I only have about 10cm before I reach bump stops.
 
Yes, 254mm are 10" springs.

This calculation was made with 2 springs on top of each other, worked well but had some rubbing on the strut housings, and spring perch were very low on the strut threads. Jeremiahs solution with barrel type springs is better, they have more usable length for a given length. I would suggest you going this route.

https://eibach.com/america/en/eibach-news/16-xt-barrel-spring

https://swiftsprings.com/products/universal/std-coilover-springs-25.html

Swift springs have a 4" OD on 16" springs, Eibach stay with 3" OD for all the lengths thus I installed Eibach springs.

If the springs are too short, you will have coil block on full compression before using the total amount of the shaft...no good !

How far from the top of the strut housings are the lower spring perch actually, front and rear ? Is it the ride height you want or do you want to go higher/lower ?
 
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Yeah I've got spring block all around and left rear is rubbing on the strut housing with the 250mm springs.

The Boynes springs I'm getting are 75mm ID wound down to 60mm ID on the end for mounting. These were a bit cheaper then barrel springs and should clear everything. So I'll see how these go first. But if I have any issues those eibach ones look perfect!

On other news today was the first time taking the hotbits offroad. I'm still missing out on some uptravel due to the spring block, however I did get through sections with out wheel lift that I previously would have lifted wheels. So it's already looking really good! Will post video tomorrow.
 
Yesterdays trip to Mundaring Powerlines. Previously I did lift wheels right in the air through this section. The only other vehicle on the day which did this section as easily was an XJ Jeep. Landcruisers and Patrols all had big wheel lift, I think another factor for this was the difference in wheel base.
https://www.youtube.com/watch?v=oSQrtBBr-Aw&feature=youtu.be
 
How did you modify the rear top hats ? How much shaft length did you loose in the rear top hats, 25mm ? You still have 275mm stroke, right ?

Short and long springs are the same price but for our application, springs are never long enough. Ask at Boynes the usable length of their springs and compare with the Eibach or Swift because they may fabricate springs with the same specs but with 2 or 3 more coils meaning you will block earlier.
 
At the moment I just stacked the hotbits supplied upper spring perch on the unmodified top hat so am losing closer to 50mm.

I will modify the top hats at the same time I fit the next springs so will probably only lose about 25mm at the best. Plus the 60mm bumpstops can compress to 30mm. So should be 245mm of usable stroke.

Boynes have 260mm usable travel on the data sheet. They say it will be slightly more than this due to having the ends wound down, but lets just call it 260mm. So 15mm to spare. To get the right ride height I will have 5mm of compression at full extension. So really there's only 10mm to spare...

Eibach and Swift both have more usable travel despite being a shorter spring.
 
If Boynes can make 400mm springs you should take them. Because if you want to change for more ride height it will give you more space between spring seat and housing top (thread length). Spring block is not very good for the spring seats as all the energy on full compression will hammer them instead of the bumpstops.
 
Hey Red ! How is it going with the HotBits ?
 
Lengthy process. The boynes springs went in, they gave full flex on ramps and drove nice on road. But the stiffer rates killed traction offroad. Despite being wider and wound down on the ends they still bent in the middle and rub on the strut housing. They also sagged more then expected, apparently they weren't designed for full travel regularly and was over stressing the steel. Which was not an issue I was expecting...

I'm now just going to get the Eibach 16" barrel springs in 27N/mm front and 22N/mm rear.

Do your rear springs rub on the car on full droop?
 
Red XS said:
Do your rear springs rub on the car on full droop?
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Yes, slightly but its not an issue as the Forester is not that often at full droop, its my DD and spends most of the time on road
 
Update, after fitting the Eibach springs I also lowered the rear diff 25mm. This gets more droop out of my 300mm stroke Hotbits with out loosing ground clearance as the front is still the lowest point on the car. Anyone else getting Hotbits for an SG that doesn't want to lower any diffs should get 210mm stroke front and 275mm stroke rear. But lowering the rear diff was relatively simple. I'm yet to do a proper offroad test with the Eibach springs, Subaru engine oil leaks need taking care of first.
 
If you don't want to lower the diffs, I confirm that the rear shaft length should not exceed 285mm for a given 260mm stroke (25mm are lost in the top hats)

At the front, on an SG, you should be able to go up to 240mm stroke which is the same as OEM with a 2" lift kit (190mm stroke + 2")
 
very cool indeed . an amazing foresters with longer travel. price is not whats amazing. but make it short can somebody tell the real number like OEM shocks vs HotBits. like how much more travel and how much more damping it gives. i see videos tested on dry roads. so what about muds , water crossing and rocks . those things should help on rocks i think.
 
so yours is that green forester ? not that in avatar pic ? or its not your car in videos ?
and are there any videos of long travel one going with stock one and how they flex both ?
 
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Stock stroke that came out of my 2006 Forester was 140mm. I think your 190mm figure is after adding the 2" lift. The 210mm Hotbits max out the downward travel of my control arm.
 
140mm stroke front ??????

SF is 170mm and SG5 is 190mm (without bump stops)
 
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