Rear bumpstop options with LT setup (1 Viewer)

[ArBrnSnpr]

The way I've always know to measure bump stop length on modified vehicles is to measure the gap between the axle and bump stop at rest. Then remove the springs and shocks, put the frame on jack stands. Cycle the suspension with a jack and measure the distance the axle is from the bump stop mounting location at the point the wheel is about to contact the body (usually the first place to hit) when stuffing/compressing suspension, OR, when your shock is fully compressed.

That's your correct bump stop size.

I modified my factory bump stop as a temporary solution and it's been fine for about a year now. I just cut the first section above the little "window" off. I plan to replace them, but they haven't lead to any damage yet.

 

[co4wheel]

Never use those OEM Air Bag Bumpers with Coil Springs.

 

[HomersCanyonero]

@co4wheel and @ArBrnSnpr and @coops2k and @joabmc or anyone who has a similar long travel rear ... could you measure your distance from the axle to the bumpstop and from the axle to the frame where the bumpstop attaches?

I’m unable to cycle the suspension to figure out my correct bumpstop length, so I want to copy yours since I have a similar setup.

my setup is Icon 56550 extended travel rear shocks 17”/28.5” and Dobinson c59-675v rear coils that put me at 23.5” hub to fender in the rear. Proforged sway bar end links for extra 1” length. awaiting offset and extended non-adjustable rear lower link from Resz Fab.

 

[HomersCanyonero]

The bottom of my bumpstop is at 3.5” to the axle using the “Measure” app found in the utilities folder on my iPhone XR.

Edit: Using a ruler, the actual distance from the axle to the tallest side edge of the bumpstop rubber is 3 7/8" (almost 4"). This is after the conversion to extended travel coils and long travel shocks. This is measured while sitting on my driveway with an empty gas tank and the third row seats removed. So, less than empty rear and hub to fender was at 23 5/8".

 

[joabmc]

I’ll get you measurements tomorrow.

 

[HomersCanyonero]

Never use those OEM Air Bag Bumpers with Coil Springs.

@co4wheel I'm trying to figure out why you don't recommend the stock oem GX470 bumpstops with coils. Is it the length? Or the material? Or both? I'm just trying to understand the rationale behind the recommendation not to use them with coils.

There are so many different aftermarket bumpstops and one company even claims that their softer competition rubber bumpstops are better than the hard stock rubber FJC/4R bumpstops: Competition Rear Bump Stops [5thGenRearBumpStops] - $113.65 : Sonoran Steel Fabrication LLC, Toyota Truck Parts

So, I'm just trying to figure out why my stock GX470 rear bumpstops are not recommended with coils.

I do realize that they need to be at the appropriate length for my Icon MT LT rear shocks and that they are offset properly. So, if they are the right length and I can offset them properly, then why are they not recommended?

 

[HomersCanyonero]

@joabmc did you measure your bumpstop distances?

I just realized that there’s not much discussion on the rear upper spring cone isolator acting as a bumpstop inside the spring. I just measured the distance from the bottom of the upper isolator to the top of the coil puck inside the spring and it’s less than 4”.

So, it looks like we have two bumstops: inside the spring and outside the spring.

In my case, both areas are under 4” to make contact and act as a bump stop.

So, why do we need two separate bumpstops?

 

[joabmc]

Apologies. I was working on the FJC all day and forgot.
To add to the discussion, I pretty much destroyed the OE GX bumpstops after a long weekend just on forest roads. They actually started to disintegrating on me. They weren’t designed to take that type of abuse as the airbags limited contact according what I was told by MT.

 

[HomersCanyonero]

I see and it makes sense, but your upper spring isolators don’t help with the bumps?

Why we need two bumpstops?

Im wondering about that now.

 

[CarolinaGX]

I don't think we do have 2 bump stops. The outers are bump stops in the sense that it prevents the axle from hitting the frame and ours are different than 4runners because of the air bags but both have one in that location. The inners, also called isolators, are actually progressive springs. The conical, hollow, and varied thickness indicate (to me anyway) that they are a spring rate enhancer as the axle approaches the frame, before actually hitting the bump stop. That is my guess

 

[HomersCanyonero]

Hmmm, interesting discussion points.

So the inner upper spring isolators should hit first to help the increase the spring rate and then outside bumpstops hit next to really prevent the shocks from bottoming out.

“Muy interesante”

Please send me your bumpstop distance measurements especially if you have cycled your rear suspension to calculate the appropriate distance/size of the bumpstops.

 

[HomersCanyonero]

I just happen to see a dirt patch where I could flex a little more than the sidewalk by my house.

The stock oem GX470 rear bumpstop 4.25” aligns pretty good with the axle. I had it almost touching.

icon 56550 LT seems pretty close to max compression, but I didn’t have my ruler or tape measure with me and didn’t measure.

I’m trying to figure out what rear bump stop spacer that measures about 1” I could use for now.

 

[HomersCanyonero]

I ordered training hockey pucks for $3 each to install inside the bottom rear coil. This is to shorten the distance between the bottom of the isolator and the top of the coil holding metal puck by 1”. I’ll be at under 3” after installing training puck.

And I’m looking to build my own DIY bump stop extension aluminum brackets using 1.5” x 2.0” x 7” aluminum flat bars $28 total for 2. Drilling holes and attaching to my stock oem Gx470 bumpstops. This will leave me with about a 2.75” gap between the bumpstop and the axle.

 

[co4wheel]

@co4wheel I'm trying to figure out why you don't recommend the stock oem GX470 bumpstops with coils. Is it the length? Or the material? Or both? I'm just trying to understand the rationale behind the recommendation not to use them with coils.

There are so many different aftermarket bumpstops and one company even claims that their softer competition rubber bumpstops are better than the hard stock rubber FJC/4R bumpstops: Competition Rear Bump Stops [5thGenRearBumpStops] - $113.65 : Sonoran Steel Fabrication LLC, Toyota Truck Parts

So, I'm just trying to figure out why my stock GX470 rear bumpstops are not recommended with coils.

I do realize that they need to be at the appropriate length for my Icon MT LT rear shocks and that they are offset properly. So, if they are the right length and I can offset them properly, then why are they not recommended?

Because the oem ones tear and rip.

Just get a real bump stop and don't make a hard job of it. OEM 4Runner. Wheelers Super Bumps are actually nicer. Then use a strong bump extension to tune it to your specific shock length. That is why there is no universal option. Everyone makes different shocks with different collapsed lengths.

 

[HomersCanyonero]

I’ve read posts on the 4R and FJC forums where they buy the longer GX470 bumpstops when they do a 2” rear lift.

So, I’m gonna ride mine until they disintegrate! I’ll just add my own 1.5” DIY drop blocks and then I’ll buy new aftermarket ones.

 

[co4wheel]

I’ve read posts on the 4R and FJC forums where they buy the longer GX470 bumpstops when they do a 2” rear lift.

So, I’m gonna ride mine until they disintegrate! I’ll just add my own 1.5” DIY drop blocks and then I’ll buy new aftermarket ones.

If they fail, and the shock is over compressed it can ruin the shock.

 

[MTNHUNDY]

If they fail, and the shock is over compressed it can ruin the shock.

Just to clarify, if using wheelers super bumps with MT LT rear suspension and MT 3” bump stop drop, you should ditch the super bump mounting bracket and just run a 1/2” spacer between the super bumps/MT 3” drop?
Trying to get it tuned properly as it seems to bottom out prematurely and ride quality has suffered quite a bit. Plan on ordering a couple spacers from wheelers to get it dialed in before we start wheeling this summer.

 

[HomersCanyonero]

Im trying to figure out a fórmula to calculate the ideal gap between the bump stop and the axle.

I haven’t worked on my rig recently since I’m throwing $$$ at the 2008 LS460 money pit with busted suspension bushings and a possible bad brake actuator. Only silver lining on the LS460 is that Im getting a new dashboard and door panels due to a lexus repair bulletin.

 

[joabmc]

I need to get measurements. Forgot about this...

 

[HomersCanyonero]

I found this site that tells you how to measure shocks: How To Measure a Bilstein Shock

I went out to my driveway and mesaured from center of eyelet to base of stem using a string. The distance measured 21.5" long. Per spec, my ICON MT LT rear shocks are 17" compressed. So, it looks like I have 4.5" before the shock bottoms out.

The distance from the stock oem GX470 bumpstop to the axle is about 3.75", so you would think I'm good even if the stock oem bumpstops were to compress about 3/4".

Also, the upper isolator is under 4" from the base coil mount. So, both the bumpstop and the upper isolator will make contact before my shocks bottom out. I'm not sure what a safe gap would be, but at least both items will hit prior to bottoming out.