Front strut coilover project to allow taller tires

[mountainhick]

Edit/update August 4 2015; This is a real project now. f you want to skip to the actual project/solution, skip to Post #10. I am picking things up there and will document the work as it happens.


Previously edited this entire thread. I started it before getting into the idea of building a set of lifted front struts and coil over springs, but that looks like where this going. This is pretty long winded so I'll breakit up into sections

The goal: 2” front lift and ability to use 29”-ish tires. Preferred size 235 75r15 just because they are super common in LT.

Transmission gearing and diff ratios are already accounted for. If I swap the diffs back to 4.3 it will give me essentially the same engine RPM to ground end ratio that I have now, with extra ground clearance. I realize I will need to trim wheel wells, Can possibly get away with just trimming the plastic that wraps from side trim panels, but we'll see.

Already tried:

-I did the 2” lift using Tim's method of building lift blocks for the top mounts. But, it doesn't raise the spring perch, so I can't run larger tires. In actual use I have caught oil pan, transfer case, exhaust and diff mounts when on dirt roads and really could use that extra clearance. If I am taking it apart again, rather than just replacing tired front springs, may as well really do it up.

- I tried to find other struts that would take care of it. I referenced Zenseeker's suspension page with possible strut replacements, and referenced to Monroe's dimension chart. I looked at mount type and stock tire size on the other models of cars. The one that came out the winner dimensionally was the model for Ford Escape/ Mercury mariner/Mazda Tribute, with the model for Hyundai Sante Fe runner up. So I went to the pick n pull and found these. Neither had bottom mounts that would bolt to the previa steering knuckle. I consider the one for the sante fe as completely incompatible. It is for a 1” thick steering knuckle and the Previa's is 1 7/16” The one for the Ford/Merc/Mazda is kind of closer, it is 1 7/16”, proper thickness, but hole spacing and holes themselves are smaller, and there is not enough metal in that part of the strut to mod without welding on extra metal and completely re drilling. May as well weld extensions on the bottom of stock Previa struts, but I don't think anyone around here will do any welding on a charged strut.

I also had a quick look at an earlier model Sienna strut and the spring perch was not high enough, so I didn't even take other measurements on it.

I still want to see the strut for the Mazda MPV before launching into a coil over project, but I have my doubts.

[mountainhick]

So in the meantime I am trying to piece together design data for possible DIY coilovers:

The original springs are probably progressive rate, coil overs are generally constant rate. There is the possibility of adding tender/helper type springs in a coil over, to make them more like progressive rates (really more of a double rate setup) but to keep it simple I'd try constant rate first.

So here is the proposed strut set up:

-Use spent set of previa strut bodies

-cut top of cylinder, and remove guts

-Option 1 (preferred): remove bulk of spring perch leaving just a bit of it still attached to strut tube as collar/ base for coil over adjustable tube. Threaded tube with bottom spring height adjuster nut(s) slides over upper strut tube and sits on this collar.

-Option 2 that I don't think will be necessary unless a threaded tube's diameter is too big; remove spring perch entirely and weld a collar on a couple inches higher on the strut tube to support threaded coilover tube. No problem to weld once the guts and pressure are no longer a concern.

-use shock/strut insert inside the cored out strut body. This is also something I'd have to spec out. Relevant parameters are size, travel and valving. Many of these have adjustable valving, but adjustment at the top of the shaft, and would be a nightmare to access under the dash. It would have to be a set it and forget it option, but these cartridges have the benefit of several adjustment levels rather than an insert with fixed valving which if not selected properly may just not work well.



So, to spec out the springs themselves, I need:

-Corner weights of front wheels. If anyone has this please let me know, or one way or the other I'll weigh mine

-Stock spring rate: I think I found a reference for stock spring rates based on Tein springs in Japan for Estima 1990-99 (thoughTR11-21 independent rear)

https://www.tein.co.jp/srch/eng_search.php?maker=TOYOTA&carmodel=ESTIMA&modelyear=1990.05-1999.12&item=HIGH.TECH&restype=1&allvch=0

Front 3.2 kg/mm (179 lb/in)
Rear 7.6 kg/mm (425 lb/in)

Front 3.2 kg/mm (179 lb/in)
Rear 7.6 kg/mm (425 lb/in)

-Spring height measurement from top hat down to spring perch, measured with vehicle on level ground. I can't get a useful spring height measurement here. My own van's spring height measurement is wrong (low) due to worn out springs,



SO...

[mountainhick]

Question for anyone who can grab a quick measurement.

I need the measurement from top hat down to spring perch on good front springs, with the vehicle level.

And actually, the more the merrier. With Previas being older cars, I reckon many have tired springs, so the tallest measurement found with stock parts would be the closest most useful measurement to new spring height.

Please help me out!

[mountainhick]

It's the weekend and it'll take all of a couple minutes, please can anyone help me with this measurement?

Measurement with vehicle on the ground, front spring from top hat to spring perch. Mine is at 7" and I am sure much lower than it should be.

Thanks

[timsrv]

I'd do it for you, but my Previa (the only one I have left) is also lifted and I have rubber "H" blocks between the coils. My coils are also original and have been overloaded and abused. Good luck. Tim

[mountainhick]

Thanks for the consideration Tim,

The lift doesn't affect it. It is the same vehicle weight compressing the spring regardless. It would be different measuring "ride height" from the ground, but I am looking for spring height measurement only within the strut assembly. But with the spacer blocks and sag, yeah wouldn't be a useful case.

[mountainhick]

Please, is there anyone else that can take this measurement?

I really need the best info I can round up in order to spec out coil overs. Without it, it could be a lot of investment for mediocre or worse results.

Thanks

[mountainhick]

Update; another day at the junkyard yesterday. Struts from Mazda MPV do not have compatible bottom mounts for Previa. Too narrow gap for steering knuckle and holes spaced closer and smaller diameter.

[mountainhick]

Another update. I got my hands on Toyota Highlander front struts, 2 different versions from 2008 and 2012. Both have the correct bolt spacing and hole size on the bottom bracket, but much slimmer fit to the steering knuckle. No go.

So, I found 2" strut bodies with threaded retainers for strut inserts on a Volvo 240 and cut them off to splice to my old set of bad Previa struts. Looks like I am heading down the road of rebuilding them as coilovers.

I am finding the spring rate and shock damping issue quite challenging however. Older model years of the Toyota Rav4 used strut inserts that are about the right size with adequate travel. I checked with KYB. Previa struts have 110/40 front shock damping and the Rav4 has 105/55. That's about 5% softer rebound, but 37 % harder compression. A little stiffer ride would be good, but 37% could be a significantly more unforgiving ride.

[mountainhick]

After trying to find replacement struts to bolt in, I found nothing compatible. After trying to find inserts with correct damping, found nothing compatible in a reasonable price range. It seems Koni has some adjustables for other model cars that would have compatible range, but would add another $340 to the cost, more than double than if I use the stock struts.

So, Plan B is in motion:

-Use current struts which were just replaced 2 years and less than 12K miles ago.
-Remove old worn out coil springs, replace with coilovers
-Cut spring perches off current stock struts, but leave a small rim at the weld to support a coilover sleeve.
-After all the measuring and calculating, a 14" 200lb/in coilover spring seems best for maintaining close to oem rate, setting ride height and maintaining excellent suspension travel while allowing extra clearance for taller tires.
-Redo lift strategy, remove 2" lift spacer (Tim's version) at top mount. I think the passenger side top mount is stuffed anyway, so I am replacing the strut mounts and will fashion 1" spacers from solid material that are not welded to the top mounts, and gain 1" more lift from coilover height adjustment.

All of this will accommodate bigger wheels and tires. I plan on 28.5-29" tires. I will be going back to the 4.3 differentials to regain the torque, with a resulting 3.5-4% reduction in top highway speed, (currently optimised for about 75 mph in 5th gear at 3100rpm , that will drop to about 72 mph), but gain same percentage in low end torque. As is, acceleration is pitiful, so this is helpful. I am sure I'll need to mod the wheel well trim, and possibly the wheel wells themselves.

Here's the parts list linked to where I got them:

Allstar ALL64160 (http://www.amazon.com/gp/product/B006K8TFPC?psc=1&redirect=true&ref_=od_aui_detailpages00) 5" coilover sleeves
Allstar ALL 64180 (http://www.amazon.com/gp/product/B006K8TP3Y?psc=1&redirect=true&ref_=od_aui_detailpages00) coilover adjuster nuts
Coilover top hat (https://technotoytuning.com/universal/parts/conical-upper-hats-coilovers-25-id-springs-22mm-center) for 2 1/2" ID coilover springs, 22mm bore matches stock Previa/KYB strut shaft
Hypercoil 14" 200 lb/in (http://autoplicity.com/search?searchterms=Hyperco+UHT14-200) UHT coilover spings
KYB SM5095 (http://autoplicity.com/search?searchterms=KYB+Suspension+SM5090)Top strut mounts
shock boot/bumpers (http://www.amazon.com/gp/product/B00HCOGV96?psc=1&redirect=true&ref_=od_aui_detailpages00) (my old bump stops are shot)

Total cost of these parts shipped: $313.63

Next is to decide on which size tire. Maybe keep the original rims and go for 235/75R15, but they are a bit wide. Could cause rubbing on the shock tube itself. Might have to go up to 16-17 rims.

[Ian R.]

Hey MountainHick,

I saw a post you made on MP with regards to climbing rigs. I thought to myself, wonder if they are on TVT. Sure enough.. Your ride sounds pretty stellar!

[timsrv]

This is awesome! Pictures? :mrgreen:

[mountainhick]

Hey MountainHick,

I saw a post you made on MP with regards to climbing rigs. I thought to myself, wonder if they are on TVT. Sure enough.. Your ride sounds pretty stellar!

Cheers Ian, yes I am at Mountain Project

[mountainhick]

This is awesome! Pictures? :mrgreen:

Thanks Tim,

Just ordered the parts yesterday. Pics will be coming once work starts.

[timsrv]

Cool! FYI, the picture hosting feature on the site is now FIXED!!! :thmbup:

[mountainhick]

That's great Tim!

So I had to add another $32 to the cost. For the upper spacers: http://www.ebay.com/itm/231632712528

[zepedrorusso]

You're awesome! Any idea to build a special shield for the oil pan ? I have been knocking it in my hard trips !


That's great Tim!

So I had to add another $32 to the cost. For the upper spacers: http://www.ebay.com/itm/231632712528

[mountainhick]

We'll see about a skid plate, I don't know.

Work has commenced. I started working the aluminium plate for the spacers. Metalwork with woodworker's tools!

Unfortunately, my bandsaw tires crapped the bed. New set is on order, going to have to wait until I get them to cut the plate to fit the mount footprints. I'll update this post once I can complete the work and have usable spacers.

For now, here's what I have been up to:


Laying out for mount:

2785



Without a mill, how I do the circular cutouts... Drill first:

2786



Cut out with jigsaw:

2787


Oscillating drum sander to sand to line:

2788



Mount fitted, I chamfered the inside edge to ease the fit. Bolt holes located and initial drilling done. I doubt I'll be able to get the same kind of press in bolts 1" longer, so I'll probably tap the aluminium so I can bolt the strut mount to the plate and the bolts will protrude through to mount into the vehicle.

2790



More work, finishing the spacers:

Tapping the holes:

2803



Cutting out the shapes on the bandsaw:

2804



From there I filed/sanded them smooth and painted them. You'll see them in the next post with the struts...

[mountainhick]

The work on the strut and putting it all together:


Cutting off spring perch with cutting wheel on angle grinder:

2805

2806




Then I ground off most of the perch and wanted to try the fit of the sleeve, but the upper flange was too big in diameter, so I ground down the flange so the sleeve would fit over it. (Note, I kept cooling the metal with water as I worked, I didn't want any chance of a pressurized strut heating up).

2807

2808



After spending considerable time with a hand file, trying to make the remnant of the perch and it's weld provide a good seat for the sleeve, I wasn't happy with the result, and wanted a better platform for the sleeve. The solution was to use one of the pieces of aluminum I cored out from the spacer billet, and turned it on my lathe into a pair of collars.

Here's the strut with perch ground/filed down, the sleeve and the collar.

2809



The sleeve was a bit of a loose fit on the shock tube, so I built it up with a few layers of electrical tape to where it went on very snugly. Then I packed the gap at the top of the sleeve with RTV sealant.

Here are the parts ready to assemble (minus the dust boot/bumper). Note that the spring compressors are only on the top half of the spring. There is not enough room between the coil and the sleeve for them to fit down lower.:

2810




Top cap and conical washer. This washer is necessary so it bears in the inner bearing race of the upper strut mount. Without it, the spring top cap would not be able to pivot correctly when steering. This part is from Subaru, and is a standard part on pretty much all their struts since at least the 1990's. Blessedly it is a perfect fit!

2811



Top mount and spacer attached

2812



Assembled coilover strut:

2813



I will be installing tomorrow. More to come on installation and setup.

[timsrv]

:thmbup: Much better way to do this! My method sucks compared to this. Looking forward to seeing this with monster tires on it :yes:. Tim

[mountainhick]

Simulation adjusting preload; Actually did it in the bench vise. I didn't have a proper spanner so made one. The wood spanner worked before the coilover was installed in the van, but was too bulky in place. I adjusted it way too high, and once installed, had to drop it a couple inches to get it down to correct ride height. Anyway, I made another spanner from and old aluminum shelf bracket to do the adjustment on the vehcle, but the wood version is shown here:

2816


Coilover installed:


2817





So, a couple notes, learning points:

-12" springs would probably be fine and allow a bit more clearance for larger tires, but I think I'll be fine with the 14". We'll see when the new tires go on.

-When I did the original 2" strut mount spacer aka "Tim lift", due to the resulting angle from the control arm being pushed so far down, it was a pretty serious battle coaxing the steering knuckle into the lower strut flanges. With the new 1" spacer at the top, the entire coilover assembly is relatively an inch shorter and installation was absolutely no problem. The extra inch of lift now comes from spring preload,

-Now, the 1" spacer at top is bolted/removable, not welded to the strut mount. Before this new mod, I was having a lot of rattling on rough roads, and a particular clunk cornering both ways left and right. I suspected the top mount was shot, and when removed, I did indeed find the passenger side strut mount bearing was stuffed. So this seems a disadvantage to Tim's lift spacer. When a top mount fails, it is welded to the pacer and you need to replace/remake the whole unit or rebuild it by removing the bad mount welded to the spacer and welding on a new one. Now if a mount goes, it just comes right off, no welding required.

-The 200 lb/in spring rate is definitely stiffer than the tired old springs. Now there is less give when cornering. I found myself going faster on the familiar windy roads here and it felt more solid, but at higher speed, also feels a little more tippy, like it would be more unforgiving/prone to roll for evasive maneuvers. It is really nice on dirt roads, solid but not harsh. I was concerned about spring/shock matching and shuddering off corrugations, but the resulting combo feels much BETTER!

So, alignment tomorrow, then we are off for a backpacking trip. I got a set of 16" rims but need tires. I'll be going with 225/70R16 which are 28.5" diameter (stock is 26") and reverting to the 4.3 diff ratios. It'll be a few weeks, then I'll post about running bigger tires.

[mountainhick]

A couple more pics,

With ride height adjusted and wheel on:

2818



Hard to make out, but some added clearance on the inside of the tire:

2819

[timsrv]

I can't wait to see Super Swampers on that thing :yes:. Even if you do go crazy with big & wide tires, you can always put spacers between the rims and the hubs and/or off-set rims. This is totally realistic now that you're only dealing with small distances (all made possible by those small diameter springs). Tim

[mountainhick]

I am not completely decided about tire size yet, but won't be putting on monster truck tires! I am figuring on 225 70R16 because:

-There should be enough room, and maybe, I won't have to alter the wheel wells beyond just the plastic trim.

-with the 4.3 diff, it'll regain a bit extra pep/acceleration,

-to keep the tread width close to stock for snow traction.


Next choice would be 235 75R15, but that might be wide enough to need a different wheel offset. The benefit to running a bit wider stance could be to counteract the higher center of gravity and help prevent rollover.

[mountainhick]

Update, and almost finished this project!

We took the van on a trip to WY. Drove close to 1000 miles in all still with the stock 215/65r15.

The van handles SO MUCH BETTER! No sponginess in the front, solid tracking and performance on pavement and dirt roads. Feels better to drive than any Previa I have driven!

Finally got the right wheels off a 2004 RAV4 and a set of Cooper discoverer tires 225/70r16, put them on and took it for a spin. All is well. The only place where clearance is a problem is with the plastic trim pieces in the front wheel wells on the rear side by the door. These will be trimmed and I'll swap out the diffs for the 4.3 ratio this weekend.

There's about 3/4" clearance from the struts, and 3/4" clearance for the sliding door to clear the rear tires.

I am ecstatic! This worked beautifully!

Almost comically big tires for the Prev:

2896

2897

2898

[willyd]

Are you possibly gonna start selling something like this?

[mountainhick]

I am just a tinkerer, not an enteprenuer.

BTW, I ended up swapping the LSD between the differentials myself. Working from known good ring and pinion setup, good bearings etc, the FSM, and this web page as a "how to" reference: http://gearinstalls.com/ , I swapped the LSD for the open diff, set up backlash and preload, and the 4.3 with Torsen LSD is back in the van. The gearing in combo with the larger tires is indeed better.

I suspect I'll put up the 3.7 diff up for sale soon

Having driven many more miles after the change, the van drives and handles better than it ever has. I am really happy with it.

The speedo is still around 6% off, but just yesterday, I finally found the rare 18 tooth 6:18 speedo driven gear in a 1986 forerunner at the boneyard. I'll be swapping the old companion flange with 6 tooth drive gear and this driven gear into the transfer case soon, and if I remember right, the speedo will be within 1%.

So, the next brainchild is to rebuild the spare manual tranny I have as backup with a different set of gear ratios. I don't know if parts are interchangeable between Toyota W series and G series trannys but if they are... W59 has a lower set of first through third, and W58 has a higher 5th. From the parts research I have done so far, I am pretty certain I can transplant the 5th gear, but not too sure about first through third. With those ratios, and the current tire size, it would be the best of all worlds... better low end torque and acceleration,and 75 mph at 3000 rpm.

[cvtroger]

That is awesome bro!

[Jaho]

Love this post. What rear springs/lift did you use to even out the rear?

Thanks

[mountainhick]

Love this post. What rear springs/lift did you use to even out the rear?

Thanks

The Moogs for Mustang mentioned way down Tim's first post here: http://www.toyotavantech.com/forum/showthread.php?3-Lifted-All-Trac-Previa&highlight=lifted+previa

[f1slash]

Totally inspiring, yet totally out of my league!

I'm guessing there's no way to do any of this with off the shelf products?

[timsrv]

Back around 2005 I was searching for bolt on stuff and there were options (although limited). I was inspired by an air suspension system specifically for the Previa. It came with air struts for the front, air shocks for the back, compressor, and all the other goodies. It was a bit expensive (around $1,500 if I remember right), so I put it off. Then about 5 years later I decided to pull the trigger and could no longer find this or anything else. I guess there isn't a big enough market for "Previa specific" suspension kits anymore. That's when I decided to fab my own lift kit. Tim

[gshadow32]

bags are still out there, more universal stuff now. check universalair.com

im adding on board air this weekend.
5 gallon tank
dual viair 480c pumps
200psi
shocker xl train horns LOL

[mountainhick]

The only customized parts (other than cutting gringing the struts themselves) are the top 1" spacer blocks and the machined rings at the bottom of the springs. All other parts are off the shelf.

I am sure there are other ways to create the top spacers. Making the aluminum spacers was difficult for me without a mill. I wonder what other materials would work easier yet still have the needed strength.

I suspect you could find some kind of stock ring. I would prefer some kind of steel ring rather than aluminim. Treasure hunt...

[f1slash]

The only customized parts (other than cutting gringing the struts themselves) are the top 1" spacer blocks and the machined rings at the bottom of the springs. All other parts are off the shelf.

I am sure there are other ways to create the top spacers. Making the aluminum spacers was difficult for me without a mill. I wonder what other materials would work easier yet still have the needed strength.

I suspect you could find some kind of stock ring. I would prefer some kind of steel ring rather than aluminim. Treasure hunt...

Interesting.

Looks like gshadow was able to get his lift with stock Previa shocks and struts, a spacer, and 8088 springs. Seems like the simplest method I've seen yet. And for me, simple is good.

http://www.toyotanation.com/forum/85-previa-forum/372460-got-lift-kit-built-installed-2.html#post10296858

[mountainhick]

That is a simpler solution. Getting lift is one thing, getting rid of the front spring perch is another. Depends on your goal, how big a tire do you want to run? What performance issues do you want to improve?

And, I wasn't happy to just wail on the spring perches with torch and hammer.

BTW, I did the front spacer rear spring version first. The self built coilovers were to improve the front lift and totally get rid of the spring perch. And the coilover springs are vastly better than the tired stock springs. Definitely runs/rides a lot better. I have no regrets.

[f1slash]

I'm currently running 215/50r17 snow tires and stock size 16" summer tires that have virtually the same circumference.

The goal is to increase clearance so I don't bottom out as easily when off road or in deep snow. Looks like 2" is the max people have gone comfortably. I'm not sure what size tire I want to run but looks like what you and gshadow are running would work. Or something along those lines. I'd be happy to run whatever gets me there with a minimum of tinkering.

I need to replace all shocks and struts anyways but there's no point in taking everything apart and replacing with stock if I can just change/add a few parts and get a lift at the same time.

[tbuyan]

I just completed a 2" lift using all off-the shelf parts and a little machine work.
Details to follow.

[tbuyan]

Doesn't look very dramatic does it? Here's what it looked like before:

[mountainhick]

I just completed a 2" lift using all off-the shelf parts and a little machine work.
Details to follow.

Yeah! Let's see it! :thmbup:

[tbuyan]

I'm working on the narrative. I'll start a new thread.

[chugach]

would this work, http://www.ebay.com/itm/JDM-Toyota-Previa-Estima-TCR10-TCR11-Kouki-Racing-Coilovers-Springs-/361460376047?hash=item5428b7a1ef:g:BoAAAOSwT~9Wh0W K&vxp=mtr

[timsrv]

would this work, http://www.ebay.com/itm/JDM-Toyota-Previa-Estima-TCR10-TCR11-Kouki-Racing-Coilovers-Springs-/361460376047?hash=item5428b7a1ef:g:BoAAAOSwT~9Wh0W K&vxp=mtr

For $500 + another $220 in shipping, I think I'd rather adapt/fabricate. Just my .02 cents. Tim

PS: I just notice he has it listed as "used" :lol:

[tbuyan]

Also, not apparent that they provide any lift, although certainly would accommodate taller tires.

[mountainhick]

If they are made to ride at neutral ride height, cranking up the springs to create more preload will also raise the vehicle, but if you go too far, both ride and strut travel will suffer, which is why I didn't depend on my setup's coil preload to lift it the full 2". Still used those 1" top spacers.

But, being advertised as "racing" coilovers implies lower ride height if anything.

Agree that $770 is too much for me.

[tbuyan]

Roger all that. Nice set-up for adjusting rear ride height though. Again, probably for lowering rather than raising.

[tbkilb01]

http://Journeysoffroad.com/toyota-previa-lift-kits 1 .html (http://Journeysoffroad.com/toyota-previa-lift-kits.html)

Well Journeys finished their design...looks familiar? Even coming out with coilovers...dooh!
starting at $350 for 2wd/$450 alltrac...
GOT LIFT?

[mountainhick]

Looks mighty familiar! :clap:

[93_Previa]

Yes, I too am drooling over the Journey's Off Road AWD Previa 2 inch lift kit, plus their front coilover spring offering (supposedly will be available "soon") in the hopes of putting larger tires on for better ground clearance on our 93 Previa All-trac.

Quick question: What have other folks that have gone to larger diameter tires done in terms of fitting a true full-size spare in their Previa? In other words, having a spare that's the same diameter as the larger-than-stock tires you're running now. What is the largest spare tire diameter you can fit in the spare storage area on the Previa?

[mountainhick]

Yeah, my spare tire does not fit. For now it resides inside the van... definitely not convenient.

I haven't started the work but have started to aquire the pieces to build a rear bumper with swing out tire carrier. I now have a piece of steel rectangle for the bumper and swing out arm that a guy built for his project that he never finished. It has a nice 1"axle with taper roller bearings. Once I get to it, I'll post the project here.

I also considered doing a fixed carrier on front bumper.