A90 Supra S.TECH Rear Bump Stop Modification

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With the newly released S.TECH lowering springs for the A90 Toyota Supra, we wanted to put a notice out to owners about modifications needed to the rear bump stops.

S.TECH Lowering Spring set part number: SKTJ4-S1B00

Our S.TECH spring kit (part number: SKTJ4-S1B00) includes a pair of bump stops and dust boots specifically for the rear shock absorber. However, it is to be used in conjunction with a modified OEM bump stop.

Please follow along as we show you what needs to be done.

First, the rear shock absorber mount needs to be removed. Then, the the OEM bump stop can be pulled out of the mount. Now, the OEM dust boot is simply press fitted around the OEM bump stop. You can just pull the dust boot out, or you can leave it attached. Either way, the OEM bump stop needs to be trimmed significantly, and the portion to be removed also removes the OEM dust boot. Our included TEIN dust boot will replace this piece.

The rear shock absorber mount needs to be removed from the shock absorber assembly.

With the OEM bump stop removed, you need to measure 20mm from the top of the bump stop (widest portion) down and mark this location. This 20mm piece will be reinstalled in the rear shock absorber mount. You can use a razor blade (utility knife will do fine) to cut the bottom portion of the OEM bump stop off.

The OEM bump stop and OEM dust boot are assembled as one piece. The OEM dust boot is easily removed by pulling it off the OEM dust boot.
The top of the OEM bump stop will need to be remained. This should be 20mm thick after trimming.

Now, the included TEIN bump stop also needs to be trimmed. 10mm needs to be trimmed off the bottom (narrow portion) of the TEIN bump stop.

The included TEIN bump stop also needs to be trimmed, too. The bottom portion needs 10mm but from the bottom, which is the narrow portion of the bump stop.
A utility knife makes trimming of the OEM and TEIN bump stop easy work. Just use caution when cutting.

This picture shows how it is to look on the rear shock absorber (without the TEIN dust boot, for example only) along with the trimmed OEM bump stop.

For reinstallation, hand fit the modified TEIN bump stop onto the piston rod. Then, fit the TEIN dust boot onto the piston rod.

Then, reinstall the rear shock absorber mount (with the trimmed OEM bump stop hand pressed in) onto the piston rod. Now you can tighten the rear shock absorber mount with the 16mm flange nut.

Make sure the TEIN dust boot and bump stop are placed up against the trimmed OEM bump stop (basically you are going to sandwich the top of the TEIN dust boot against the trimmed OEM bump stop and trimmed TEIN bump stop).

The final assembly should look like this. The TEIN bump stop is covered by the TEIN dust boot, and both pieces are pushed up against the trimmed OEM bump stop. The TEIN bump stop is a tight fit around the piston rod in order to keep the TEIN dust boot in place and to protect the piston rod from any debris damage while driving.

The rear shock absorber assembly is now ready to be installed back onto the vehicle.

ENDURAPRO PLUS 20K Mile Inspection

I’m lucky enough to be one of the first in the U.S. to put our new ENDURAPRO shock absorbers to use in the U.S. My 2008 Honda Fit was fitted with the ENDURAPRO PLUS (16-click damping adjustable) shocks and struts, which I eventually added our S.TECH lowering springs, around March 2018. I figured it’s time to visually inspect these shocks and see how they’ve held up.

As previously mentioned, this car is typically my daily commuter for work. I average about 14,000 miles in driving a year. While I technically have just over 21,000 miles on these ENDURAPRO PLUS shocks, the other miles I drive for the year has been on my truck. Still, I think over 21k of miles on our ENDURAPRO PLUS shocks is a pretty good age to finally give them a look-see. Mind you, the average shock absorber lifespan is typically 36,000 miles in the U.S. Not too sure how that average came to be. We see shock absorbers last much longer than that. Quite honestly, I should have inspected these shocks a long time ago (a reminder to all to inspect their cars)!

Prior to giving you a run-down of the inspection, I will say that overall the shocks still feel great! Over time, I’ve readjusted the damping click settings simply to find that “sweet spot” in comfort. After all, installing lowering springs will alter the ride quality. Currently I have the fronts and rears set to 8 clicks from stiff (essentially the middle setting). I had previously had it somewhat softer in front and stiffer in back, as I felt it worked well whenever I had the car fully loaded. I may end up softening the front just a little, once everything is reinstalled.

Speaking of fully loaded, that is probably the most awe inspiring experience that showcases how our shock absorbers perform! It really is! As you probably already know, our ENDURAPRO/ENDURAPRO PLUS line includes internal Hydraulic Bump Stoppers, which helps alleviate that ever-so-fun suspension oscillation whenever the car is at maximum capacity.

Again, since it’s my daily commuter, typically there isn’t much extra weight in the car, other than my kids’ seats and some kids junk in the back seats. With lowering springs that are a bit stiffer than stock, it can feel relatively firm over bumps and gaps in the highway. Overall, our S.TECH springs aren’t terribly stiff.

However, after my bi-weekly trip to Costco, which usually consists of purchasing several cases of bottled water, my kids’ diapers and formula, and a bunch of other necessities you have no choice but to purchase in bulk, the trunk gets heavily loaded, and you can both see and feel that added weight. Then add my sons, when i have to pick them up at their Nana’s house. It’s basically like I’m loaded for a long-distance road trip.

This is where our Hydraulic Bump Stopper really comes in to play. Our Southern California highways are anything but smooth, and there are plenty of large gaps, expansion joints, dips, pavement cracks/potholes, ramp-like bumps over overpasses, etc. It’s a great way to put suspension to work, and at highway speeds, this provides us with a horrific ride, and one that puts our vehicles through pure torture. Did I mention that I also have to listen to “Elmo’s Song” on repeat whenever the kids are in the car???

But seriously, over this type of highway terrain, TEIN’s Hydraulic Bump Stopper really does its part in helping absorb these high-speed impacts, preventing the polyurethane bump stop from doing that work and helping the shock absorbers rebound nice and smoothly. Honestly, it has to be one of the more rewarding parts of my commute. Now I can understand what trophy trucks must feel like over big jumps,,,,,, just at a much smaller scale. Hahahaha!

Anyway, on to the inspection:

One thing I noticed was the front strut mounts were making a bit of noise, especially when steering at slow speed. I initially thought it was the bearing making the noise. But, for all I know it could have been a problem with the struts. This just confirms it was indeed the upper mount. However, as mentioned during the initial installation of these ENDURAPRO Plus shock absorbers, the front mounts probably contributed to a slightly lower ride height than target, due to the mostly rubber mount taking a set after 80,000 miles of use. Now at 101,000 miles, it is time to change these components out to fresh new factory style mounts.

Old mount on the left, new on the right. You can see how the mounts have sagged over time. It was starting to make some noise, most notably at low-speed.

For the rears, the only thing I noticed was a hole being worn into one section of the dust boot. Looks to have made contact with the tire. Not a big deal, and replacement dust boots are readily available.

I also checked gas pressure while the shocks were off the car, and all of them seemed fine. By checking I mean I fully compressed each damper by hand and checked the rebound, as well as tried different damping settings during the same procedure. I will say the damping click adjusters were slightly stiff up front. However, that could be due to not using the included ADD Caps to cover them (this keeps dust out of the system). A simple spray of WD-40 or similar type lubricant will displace any dirt or corrosion in between the click knob and its base. Also, any exposed thread on the piston shafts for the front dampers accumulated some surface rust. A wire brush cleaning and some WD-40 helps clean that up. But since I removed the struts from the original upper mounts, the threads got a decent clean up simply from the removal process.

Front strut out. I needed to remove the bearing, as I thought this also contributed to noise I was hearing at low-speed driving.
With the bearing out, I decided to inspect the shock. All components removed help to make a more detailed inspection.

While I’ve had the ENDURAPRO shock absorbers off, I checked bushings in the control arms, ball joints, sway bar end links, and tie rod ends just to make sure of their condition, which fortunately they are. I’m sure at some point I’ll change out the front lower arms (bushings by themselves are not readily available). For the rear twist bar, it’s hard to source just the rear bushing, so I’m going to keep searching for a solution.

I did have the tires changed at around the 3,000 mile mark on these shock absorbers. I wanted to try something a bit more sport oriented, but not very expensive. Also, my “tuning philosophy” (if you will) for starting to modify a car is usually in the order of- decent tires, sport (not race) brake pads/shoes, and some decent suspension (as in shock absorbers and possibly springs), especially if there is a damping adjustable option. This before ever considering more power. With ENDURAPRO Plus shocks and S.TECH lowering springs and some Stoptech Sport pads and plain rotors installed, I needed decent tires. So, I contacted the guys at GT Radial to order a set of their Champiro SX2 Summer tires. I’ve followed the 86 Cup group and saw that these tires offer very decent performance and very good wear resistance, and I wanted to try something other than all-season tires that this car has used over the years. I opted for a size slightly smaller in diameter than stock just to see if there was any gain in performance.

A new set of tires go on the Fit, courtesy of GT Radial
A big thanks to Gonzo, who invited me over to his Chateau. He’s got a full tire changing station in his garage! His son Enzo also came out to help. Good kid!

I will say that these SX2 tires still provided very good comfort. Being a daily commuter, this car only gets an occasional spirited drive. For me, that comes with the excitement of driving through Angeles Crest, since it’s kind of in my “back yard”. Interestingly enough, I found that these tires at 31psi cold, and a 13-click front shock setting (soft) and 6-click rear shock setting (somewhat stiff) had very good and predictable feel. I could very lightly get the back end to rotate with a touch of left-foot braking, and the feeling was pretty consistent throughout my drive through the hwy. The Fit is a very front-heavy car, so it takes a little coaxing to get the car to turn in, since the car understeers easily. One thing I could appreciate from these tires is the wear resistance. Rated as a 200 treadwear, these tires held up better than some 360 treadwear tires I had on previously (which actually only lasted about 13,000 miles before I changed them out to these SX2’s). Dunno what the deal is with that, but those are my figures.

Mind you, these aren’t all-season tires, so I take it a little easier during rainy days. However, wet weather driving is actually quite nice on this setup. Not that I was expecting to hydroplane on a summer tire on wet pavement, it actually handled heavy rain and puddles very well.

While this is sounding like a tire review, what I’m getting at is that these small changes to this daily driven econobox (TEIN S.TECH Springs, ENDURAPRO Plus Shock Absorbers, and GT Radial SX2 tires) have already made this car more enjoyable for my drive. Does it make me miss having a much more sporty car? Absolutely. But, gotta work with what I got. I think most importantly is the value of all these parts as a whole- Not a lot of money spent (granted, I got the shocks for free for testing on my car) to “upgrade” the car. So, for most of you guys looking to make your car a little bit faster and more fun to drive, this should be something to think about.

By the way, the slightly smaller diameter tires I chose actually helped improve a few things such as MPG (when I really take it easy on driving) and acceleration (most notably in higher gears). I was expecting MPG to be a bit worse. However, it has affected actual speedometer readings a tad, but the factory speedometer reads ~1 MPH lower than actual.

All in all, I’d say I’m more than pleased with the car as it currently sits. Not a ton of money invested in getting some performance out of it. Decent suspension, very good tires, and sportier brake pads up front, and I’m a happy camper!

TEIN Hydraulic Bump Stopper Technology

Lately one of our greatest developments to hit the mainstream in TEIN suspension kits is our Hydraulic Bump Stopper (H.B.S.) system.

This technology isn’t anything new. However, the current derivative is a much more affordable design, and has now made its way into coilovers like our FLEX A and FLEX AVS kits, and now our ENDURAPRO & ENDURAPRO PLUS shock absorber lines.

Why are we creating so much buzz about this system? Mainly because a comparable Hydraulic Bump Stop system isn’t typically found in passenger vehicles, outside of trucks where you’d have to opt for something like an externally mounted bump kit.

Even our current Hydraulic Bump Stopper system used in our FLEX A, FLEX AVS, & EnduraPro/EnduraPro Plus shock absorbers differs from systems used in rally suspension, which are typically much more expensive units and require rebuild. Our current system is more affordable to make and doesn’t require servicing (FLEX A and FLEX AVS dampers are rebuildable, but the H.B.S. system doesn’t need to be rebuilt, per se).

Still, all this hype we’re making about a Hydraulic Bump Stopper doesn’t mean much if you don’t know what it does. So, picture this: You’re in a fully loaded vehicle (max occupancy) and have the trunk fully loaded. Already you can picture the suspension starting to sag. Then, while driving, you hit a big speed bump. On any normal suspension, chances are you’re hitting the bump stops, which will do a great job of preventing the shocks from bottoming out. However, the consequence of hitting the bump stop is a harsh impact and resulting bouncy or wallowing feeling.

Now, a Hydraulic Bump Stopper eliminates this bouncy/wallowing feeling. It does so by creating more damping force towards the end of the damper stroke.

Typically our dampers are valved to offer a digressive feel, meaning that as piston speed (of the shock absorber) increases, it will only increase damping force to a certain extent, then it actually does not increase in force if piston speed is even higher. That is typically fine, but when this high piston speed is towards the end of the shock’s stroke length, it will have that harsh feeling (remember that bump stop?) we’re mentioning about.

Honestly, a damper with progressive or linear rate damping can still hit a bump stop and cause that harsh feeling.

But why does creating more damping force with the Hydraulic Bump Stopper help? Essentially it’s slowing down the piston of the damper. It gradually builds up this damping force so that the end result is a smoother absorption of force, while letting the damper rebound normally without oscillation.

When you see Stadium Trucks or Baja Trucks take on a massive jump, what you see on its landing is actually quite impressive. The suspension fully compresses, but as the suspension extends again, it’s nice and smooth. No crazy up and down oscillation. That’s what our H.B.S. system does, but for a smaller scale (shorter stroke length than Stadium or Baja Trucks, obviously).

Or, another example: Using lowering springs on OEM or replacement shock absorbers. While this setup is common place, and most work relatively well, some lowering springs might be too low of a ride height or too stiff a spring rate for the OEM valved shocks. A premium replacement like our EnduraPro line is a better match. Valved to offer a beneficial increase in performance, the added Hydraulic Bump Stopper is a nice addition because of the lowered ride height with lowering springs.

While our EnduraPro/EnduraPro Plus shock absorber line is a match in terms of overall length (compared to OEM), they offer larger internal capacity and more damping oil, and improved damping characteristics. So from a performance standpoint, these are a great upgrade for your lowering spring. Again, these include our H.B.S. system, and when lowering a car using OEM/standard replacement shocks, reducing that stroke length can mean exacerbated issues with ride quality and more chances of hitting that dreaded stock bump stop. You’d end up with similar ride issues in a fully loaded vehicle. Now we can resolve this potential issue by using the increased damping force the H.B.S. system creates further down the shock absorber’s stroke length!

It really is an ingenious system, and one that we’re glad to bring into mass-production. The fact that we can adapt this product into our replacement shock absorber line means that this feature is available to all consumers, whether their budget allows for just our premium shock absorber replacements only, or for those looking for greater handling performance (like our FLEX A or FLEX AVS coilover kit). We’re hoping to add this to many more of our products in the near future!