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Thread: Complete MK2 Supension Write UP
04-05-2005, 10:17 PM #1
Complete MK2 Supension Write UP
This is the article i wrote awhile back on suspension options for our cars - i have seen many many questions asked, that are easily answered by reading it:
The Mark 2 Toyota Supra (from now on, the Supra) uses a suspension system designed in the early 80's by a company called Lotus. At that time, Toyota had a controlling interest in Lotus and had them design the suspension for the Supra, as well as several other cars, including the AE-86 Corolla.
Up front it uses a Macpherson strut suspension with a single lower control arm and strut rod. The camber, caster and toe are all adjustable but not easily. The factory size antiroll bar is 1" diameter. The rotor is sandwiched between the hub and spindle which means that you must disassemble the wheel assembly to change the rotor. The hub rides on an inner and outer bearing with spindle assembly - the wheel bearings on the Supra are known to last for many hundreds of thousands of miles, provided they are kept clean and greased, but you may want to replace the inner oil seal if it looks worn, and use a new cotter pin on the spindle nut. The steering is a variable power assist rack and pinion design. While the front suspension shares its lineage with the RA series Celica, it has slight differences in shocks, springs and kingpin angles so it is not readily interchangeable. The steering system is also not interchangeable between the Supra and RA series Celica.
The rear suspension is a fully independent semi-trailing arm design and has one major downfall - the camber change under bump and droop is extreme, and there is no way to adjust the rear camber on a stock suspension, so lowering the car can produce undesirable rear camber characteristics. In the forum there is a thread detailing modifications to the rear crossmember to allow for adjustable rear camber. The small amount of extra negative rear camber provided by a small drop (under 1.5") may benefit the handling for motorsports applications, but can be bad for traction in a straight line and tire wear. The stock rear antiroll bar is 5/8". The rear hubs are assembled with a staked nut on one end and a thru bolt with splines to transfer the torque. It is extremely rare for these to fail or otherwise require service unless they get help from accidents or rust, so my advice is to leave them alone unless they are already making bad noises. This suspension is identical to the rear suspension in the RA series Celica GTS, except for the rear crossmembers, so it is for the most part interchangeable.
The steering system in the Supra works very well and for the most part should be left untouched unless there is slop in the system. Fully greaseable outer rod ends are not a bad idea and a smaller steering wheel is nice, since the stock one is large and thin by today’s standards, so you feel like you are driving a bus. Some people do not like the low steering rate (2 1/2 turns lock to lock) and while I'll agree it is not ideal, there are not many options short of getting a custom rack made which is very expensive. Some people remove the power assist system from the rack by using a bypass hose going straight
between the inlet and outlet on the rack. This saves weight and increases engine power, but it makes the car difficult to manoeuvre at low speed and tiring on long drives, especially with a small steering wheel. If your rack has any 'slop' in it, which is not coming from the steering shaft, Jorgen automotive(link=http://www.jorgenauto.com) will rebuild your steering rack for a reasonable fee. They also replace the outer AND inner rod ends if those are giving you grief (the outer ones are easy to replace yourself). If the slop is coming from the steering shaft, Toyota still offers new ones, or you can get one from the junkyard - if your steering wheel squeaks you need to lube the horn slip ring behind the wheel in the steering column. If they are leaking, all the power steering lines are still available from Toyota or other parts houses.
Springs and Dampers
Other than wider wheels and better tires, upgrading the springs and dampers is one of the best modifications you can do to make your Supra handle better. The key is to match the new springs with the right type of damper so they are not under damped (oscillating like a big cruiser with worn out shocks) or over damped (skitters over all the bumps). The choice of rear shocks or setting of adjustable shocks depends on the application - for general road use or a bumpy track, a softer setting is better while on a smooth track a firmer setting is often desirable. The rear suspension is easy to disassemble, but the front is a little more tricky - here(link=https://www.celicasupra.com/FrontStruts.htm) is a tutorial written by Jim King on removing the front struts safely. DO NOT try to do this if you are not 100% confident in what you are doing, as I have seen someone break their collarbone when using spring compressors improperly - imagine 3 inches of compression to get a 250 lb/in spring off = 750 lb of force! Any local automotive shop would be happy to remove and reinstall springs in a pair of front struts for a small fee. For springs there are a few options:
1: Stock ride height stock or aftermarket springs
These would be good for normal street use or drag racing, since they will maintain the correct suspension geometry, avoiding the camber problems in the rear. You may be able to find aftermarket springs with a higher rate but the same height, which would be ideal.
2: Eibach Pro Kit, 1" drop.
This kit features progressive-rate front and rear springs that drop the ride height by one inch at each end of the car. The progressive rate allows it to be soft on the road, and hard enough to avoid excessive roll or bottoming at the track. The small drop also keeps suspension geometry problems to a minimum, and looks great on the Supra, eliminating the 'monster truck' ride height common on early imports. The main problem is the fact that you lose some useful travel in the 'mushy' portion of the variable rate, so they are not the best for motorsports applications. A good choice for occasional track use, or just better on street handling.
3: Suspension Techniques 1.3" drop.
This kit uses progressive rate front and linear rate rear springs with a drop height of 1.3" at both ends of the car. The spring rates overall are higher than the pro kit, so expect a firmer ride, and the drop is slightly more so they may get into the grey zone for suspension geometry if modifications are not made. The linear rate rears make an excellent companion to a coil over front setup, especially if the camber issue is dealt with, or if spacers are used. There is also the small benefit of the ST springs being slightly cheaper than the Eibach kit. Overall an ideal solution for combined track/road use, although the low ride height and rough ride may make for less than optimum cruising characteristics.
Because the rear springs are a standard size (5.5” spring with a 15” free length), you can order standard size springs to attain any combination of ride height/spring rate that you want. Remember that a higher rate spring will not compress as far with the unsprung static weight of the car (around 600lb/wheel) so you would be well advised to pick a shorter spring than stock (stock rate is around 150lb/in for the rear, so if you wanted the same ride height with 300lb/in springs you would pick ones with a 11 ˝” free length).
The choice for dampers depends mostly on the springs being used:
1: KYB GR-2
These are an excellent match with stock springs or stock height springs with the factory rate or a slightly higher rate. They will have problems damping springs with a significantly higher rate, such as the Eibach or ST kits, and may seem to react too slowly for track use. A great choice for a simple shock replacement on an otherwise stock suspension. They are not adjustable.
2: KYB Gas-A-Just
Only available for the rear, they offer self adjusting damping and will thus cope with a firmer spring in the rear. A good choice for occasional track use, especially with stock or Eibach springs. Internally self-adjusting.
3: Tokico HP
Generally agreed to be the best pairing with the Eibach kit, these dampers are firmer than stock, but still not too expensive. The best pick for occasional track use with the Eibach springs. Not adjustable.
Koni used to offer 'Red' adjustable shocks for the rear as well as 'Red' and 'Yellow' adjustable shocks for the front. If you can get your hands on a pair they will work well with most springs, as they are off-the-car adjustable, and a firm shock to start out with - especially the yellow fronts. The major downside is that they are hard or impossible to
find and expensive. The rear shock for a BMW E36 M3 will work, but the bottom bushing needs to be replaced and they are awfully stiff for road use, even on a soft
setting. The Koni shocks developed for the Supra are 4 way adjustable in the rear, and 5 way adjustable in the front, for rebound and compression at the same time (no separate adjustment).
You may be able to get your hands on a set of Tokico illumina (discontinued, adjustable), TRD (Japan only, adjustable) or Sachs shocks for the Supra. AGX adjustable strut inserts for other Toyota models may fit as well, among others (the MR2 rear struts are commonly used in the front, and a lot of models like the focus and E36 BMW M3 use very similar rear shocks). Check the forum for the latest, 935 motorsports also offers kits to adapt different shocks to the Supra. Any rear shock for a RA series Celica GTS will fit, but GT rears are a totally different design, and the fronts from both models have different valving due to much less weight over the front wheels.
Ground control and QA1 offer a front coil over setup for the RA series Celica that will fit the supra with small modifications. This allows you to pick the spring rate you want, as well as having fully adjustable ride height. Because the spring and shock do not connect to the rear trailing arm in the same spot, and the shock tower is too weak to support the weight of the car, rear coil overs are not an option. An adjustable spring perch could be used to adjust the rear ride height, and is being developed. Beware that choosing the correct spring rate with coil-overs is important for both ride frequency and roll couple distribution. a 300 lb/in spring works good for street use, especially with stock rear springs, while a 350# or 400# can be used with the ST rear springs for street/track use - the 400# may cause the front end to be skittish over bumps or increase understeer depending on the weight distribution of the car and the condition of the track surface. I would recommend a 350# rate with adjustable stiff front shocks if you want a good track and street setup (the stock front rate is about 200 lb/in).
The stock antiroll bars on the Supra are 1" front and 5/8" rear. Addco offers an upgrade with much firmer 1 1/8" front and 3/4" rear. It doesn’t sound like much, but it makes a HUGE difference due to the thicker and stiffer bar material (plus the addco bars are hollow, so they are about half the weight of the solid construction stock bars). The kit includes all the polyurethane bushings and new end links needed to install the bars. At
https://www.celicasupra.com/Addco/Addco.htm there is a tutorial on installing them. Some members have found that the tabs on the rear trailing arms that support the rear endlinks can break with the stiffer rear bar and 'spirited' driving, so it may be advisable to weld some reinforcement to these tabs. The bars also interfere with the roll couple
distribution of the car, and can cause more understeer depending on the springs used, which is not always desirable. Your mileage may vary. If you are doing serious racing,
you may consider modifying the Addco bars to make them adjustable, or getting custom adjustable front and or rear antiroll bars made.
Both Energy Suspension and Performance Suspension Technology offer bushing upgrades for our cars, check their respective web sites for more info. The PST bushings are polygraphite and thus do not squeak like improperly lubricated polyurethane ones do. The PST front end kit also includes fully greaseable outer rod ends and ball joints, which is a plus. These bushings improve the responsiveness of the car substantially, but tend to make the ride harsher. 935 Motorsports also offers Super Pro polyurethane bushings, including some not offered by ES or PST like rear shock and rear main crossmember bushings. In all of the rear end kits, one of the bushings for the rear trailing arm does not fit properly around the metal sleeve you are told to reuse, so you may want to get a machine shop to make a new set of those sleeves. Refer to the forum for more info.
Although it is a solid design, the Supra is based on early 80’s chassis dynamics analysis technology and is thus a bit dated. Chassis flex is therefore a problem, especially with wider tires, stiffer springs and better shocks. Cusco offers front and rear strut tower braces, but they are a little thin and are known to flex under load. The LJM bar (https://www.celicasupra.com/ljmbar.htm) is a much better solution for the front and is available through the occasional group buy on the forum, or by contacting MkIISuperSupra (Leslie) on the forum. People have had success building a custom rear brace between the rear seatback latch bolts, or you can get one made up already by going to Wes' site at www.tscperformance.com. The best chassis reinforcement you can get is a roll bar or cage, and you will need it for some track events, especially fast drag times or wheel to wheel racing. One for the Supra is available at http://www.ioportracing.com made by Autopower. This also allows you to properly install a 5 point harness in your Supra by attaching it to a cross bar. You can get the roll bar manufactured with removable cross bars, so the back seat can still be used when not on the track.
Other bits and pieces
Several other small pieces are available which can improve the handling characteristics of the Supra. Roll centre adjusters for the front are occasionally available on the forum or from 935 and are great for correcting the front suspension geometry when using coil-overs or drop springs (ones made for the RA series Celica WILL NOT FIT). Camber plates are also
available from Cusco to firm up the pillow ball mounts at the top of the front struts and making front camber adjustments a snap, although they can be hard to find. Also check the group buy forum for my rear camber adjustment kits. Beware of parts made for the RA series Celica, as only the rear suspension from the GTS is identical to the Supra.
The following is a list of some good suspension and steering parts suppliers for the Supra. Some, but not all available suspension parts from each site are listed. For non-aftermarket parts the best place to go is the Toyota dealership.
-bushings, camber plates, strut tower braces, springs, shocks, coil-overs, RCAs
-springs, shocks, antiroll bars
-bushings, greaseable front ball joints and outer rod ends
-shocks, springs, antiroll bars
-ST front and rear spring sets available separately
-springs, shocks (may still have some Koni in stock, but expensive)
-Autopower roll bar/cage kit
-custom rear chassis brace
-rebuilt steering racks
Last edited by Funkycheeze; 02-01-2006 at 03:28 AM.'84 P-type, 5spd, Super red, black/grey leather - 2JZGTE swap, Precision 6262 on cast manifold, ECUmaster black with 875cc/min injectors, 465 WHP at 17 psi, built R154 with OS Giken twin plate, one piece driveshaft with 1310 joints, Truetrac with 3.73 R&P, 450 lb/in front coilovers, 300lb/in rear springs, Image BBM wheels 17x8 and 18x10, 4 corner BBK, AGX shocks, Whiteline bars, poly bushings, T3 GTX2 front control and steering arms etc. etc.
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04-05-2005, 11:14 PM #2
- Join Date
- Dec 2003
I think you have to PM Karaki about theFAQ.
04-05-2005, 11:39 PM #3
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04-05-2005, 11:46 PM #4
:clap: :clap: very well done, I know this will be a great help to me in the near future
04-06-2005, 04:51 AM #5
havn't had a chance to fully read through it, but I would have to disagree about the comment that camber is adjustable on the front. You say not easily, but I'd say not at all. The amount you can get from shifting the top of the struts to the body isn't worth mentioning if thats what your refering to. Unless your refering to lowering, which again, doesn't qualify for stock suspension.Black 86 mk2 Project Car
New SDR 86 mk2 Daily User, Highway Cruiser AND Parking Lot Abuser in the works!
04-06-2005, 10:50 PM #6
yeah, thats what i was referring to - i guess its not much
bottom line is that camber plates are what you need'84 P-type, 5spd, Super red, black/grey leather - 2JZGTE swap, Precision 6262 on cast manifold, ECUmaster black with 875cc/min injectors, 465 WHP at 17 psi, built R154 with OS Giken twin plate, one piece driveshaft with 1310 joints, Truetrac with 3.73 R&P, 450 lb/in front coilovers, 300lb/in rear springs, Image BBM wheels 17x8 and 18x10, 4 corner BBK, AGX shocks, Whiteline bars, poly bushings, T3 GTX2 front control and steering arms etc. etc.
04-11-2005, 11:05 PM #7
addco bars arnt hallow. they are solid and much heavier then stock swaybars. not sure where you heard hollow and lighter.
Black 84 7mgte/R154, MS2, truetrac, bbk, etc...soon to have 2jzgte and t56
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04-21-2005, 08:03 PM #8
weight: even my rusty as shit front bar was 20% heavier than the addco replacement, this is because the addco bars are hollow - it is stupid to make a torsion bar solid, since you can get better strength with a larger diameter bar that is hollow, for the same weight
they are also a different material (hardness test confirms this, stock bars are probably 1020, while the addcos are probably a 9000 series spring steel)'84 P-type, 5spd, Super red, black/grey leather - 2JZGTE swap, Precision 6262 on cast manifold, ECUmaster black with 875cc/min injectors, 465 WHP at 17 psi, built R154 with OS Giken twin plate, one piece driveshaft with 1310 joints, Truetrac with 3.73 R&P, 450 lb/in front coilovers, 300lb/in rear springs, Image BBM wheels 17x8 and 18x10, 4 corner BBK, AGX shocks, Whiteline bars, poly bushings, T3 GTX2 front control and steering arms etc. etc.
05-15-2005, 03:03 PM #9
Funky cheese: Why can't you use offset strut mount bolts to set the camber?They are eccentric. Depending on the diameter of the stock bolts-these are available for Chryslers,Fords,etc.12mm,14mm sizes. Try Northstar or Moog.
05-15-2005, 06:04 PM #10
i never said you couldnt - but i think the only place this would work is on the bolt that mounts the LCA to the front xmember, and you would need to heavily modify the way it bolts together
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