eimkeith 3rd gen rear bumper development:

eimkeith

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OK, I'm working on (what I hope is) the last revision of my 3rd gen 4Runner rear bumper and would like opinions on the appropriate amount of bumper-to-body clearance to avoid sheet metal contact while wheeling. I set up the file with 12mm clearance but the prototypes were slightly mis-bent, yielding 6mm - this is easily resolved by adding some bend slots for the press brake operator to line up on, but I'm concerned that more clearance than 12mm may be needed?

Opinions?

By the way, I expect that folks should be running poly body mounts at this point, so I'm not going to put a one inch gap in there..

Here's a look at the prototype:

F458495B-5BAC-4659-8294-C02E7A3C5A04.jpeg4EE69AA8-04F7-45FA-BDBE-C7F1F0BCA578.jpeg
 
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theesotericone

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but I'm concerned that more clearance than 12mm may be needed?

Opinions?

By the way, I expect that folks should be running poly body mounts at this point, so I'm not going to put a one inch gap in there..

You'll need more clearance. I am running Sonora Steel body mounts in the rear. My Savage bumper came with 1/2"(12.5mm) clearance all the way around. It's never touched the tailgate but it has hit BOTH sides of the rear quarter. Since I know guys that buy your bumper will actually wheel it I'd go bigger. The weight of a loaded trail rig coming off of big obstacles produces a lot more force then even the Poly bumps can handle.

Here's a few photo's for you.

Here's the contact on drivers side:

xwxcVXm.jpg



Looking down on the bumper it's pretty clear where the contact was:

UXVw9fy.jpg



That contact pushed the rear quarter up 3/16". It's now at 11/16".

vNsVxEE.jpg



Your bumper may be better built that Savage's but Roy makes a pretty stout bumper. I've been on the phone with him about it and I'm one of the few that has managed to do this. Could you stay at 1/2" and be totally fine? Maybe. Do you really want a maybe in your product line though?
 

eimkeith

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so no issues with 1/2" at the hatch though? - that's a good data point. I'm thinking 3/4" at the sides?
 

theesotericone

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so no issues with 1/2" at the hatch though? - that's a good data point. I'm thinking 3/4" at the sides?

No issues at all on the hatch. When the frame flexes the puts the largest difference on the corners. Hence why I've hit both of them. I think you should be fine with 3/4 at the rear quarter. It's a fine line between a huge gap and a gap that truly prevents contact. Like I said, most guys will never come off an obstacle that big that hard. Since your posting here though, you've already found the guys that will. lol
 

Theblackflag

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I need to actually measure my gap, but I believe im about 3/4 of an inch everywhere, Im running the sonoran steel rear poly mounts and some energy suspension poly mounts on the next set of mounts towards the front. 90% of the time it is fine and I have no issues, however if I drop it on a boulder with any kind of force which seems to be happening more often I make contact all the way around and have hit it hard enough to cut all the wires to my swingout clean and knock the hatch out of alignment enough it had to be pushed open from inside the truck. I think at MINIMUM you need a 1/2 to 3/4 gap. Ill be doing a 1/2 inch body lift and all new poly mounts to hopefully solve the issue forever. I dont really mind the gap that much, I would rather my sheet metal stay straight.

IMG_3563 by Phoenix Black, on Flickr
IMG_3557 by Phoenix Black, on Flickr
IMG_5317 by Phoenix Black, on Flickr

This is the front bumper so its a little different but it was built with the same clearance and gives you an idea of how much our frames flex, you can see how even just flexing I easily close the gap and recently it started to roll my fenders inward and push the headlights out because of the contact
IMG_9045 by Phoenix Black, on Flickr
 

eimkeith

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I need to actually measure my gap, but I believe im about 3/4 of an inch everywhere, Im running the sonoran steel rear poly mounts and some energy suspension poly mounts on the next set of mounts towards the front. 90% of the time it is fine and I have no issues, however if I drop it on a boulder with any kind of force which seems to be happening more often I make contact all the way around and have hit it hard enough to cut all the wires to my swingout clean and knock the hatch out of alignment enough it had to be pushed open from inside the truck. I think at MINIMUM you need a 1/2 to 3/4 gap. Ill be doing a 1/2 inch body lift and all new poly mounts to hopefully solve the issue forever. I dont really mind the gap that much, I would rather my sheet metal stay straight.

Yeah if you could get some measurements that’d be great. Thx
 

AssBurns

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I guess I could measure mine, but not sure what good it would really do since mine is all pushed up from being too tight without poly body mounts. I left probably around 3/8" gap (just guessing)

I'd say 3/4" should be plenty with poly mounts.

What about making the bumper with a wider gap rather than a taller gap? That way the body slides between the bumper on hard hits rather than onto it.
 

theesotericone

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What about making the bumper with a wider gap rather than a taller gap? That way the body slides between the bumper on hard hits rather than onto it.

I was going to suggest something similar. Maybe have the bumper with an angle at the rear quarter. You could hold the bumper 1/4" or so out from the body and have it angle down 3/4". That, in theory, would prevent contact. If it did contact it would direct the rear panel down the "ramp" instead of having it compress into the bumper.

It could be a way to have a very tight finished look but still avoid contact.
 

AssBurns

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I was going to suggest something similar. Maybe have the bumper with an angle at the rear quarter. You could hold the bumper 1/4" or so out from the body and have it angle down 3/4". That, in theory, would prevent contact. If it did contact it would direct the rear panel down the "ramp" instead of having it compress into the bumper.

It could be a way to have a very tight finished look but still avoid contact.
Great idea actually!!
 

eimkeith

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Yeah, I considered that over the weekend, but I don't want to increase the width (you need a certain amount of flange for the press brake and I want a narrow bumper if possible), and there's some logic to having 0° and 90° planes for bend accuracy (I'd need to angle the sides away from 90° to slide over without sacrificing as much width.) Alternatively, I could make that flange a weld-on piece - but I'm trying to minimize welding and fitting for the end user with my stuff as much as possible; I'd like to stay away from having it be another jigsaw puzzle bumper kit. ;)

(There's another approach to the issue that's being considered in the background though - so it might be moot soon.)
 

eimkeith

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Any updates on this @eimkeith when can we place some orders. :beerscheers:

I actually took today off to get a head start on working on it this weekend! (and got called in.) Should be back on it tomorrow, though.
I've revised the sheet metal portion already, just have to redo the mounts and recovery points and think about bracing for swingout pivots..
 

WrenchnWheel

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I actually took today off to get a head start on working on it this weekend! (and got called in.) Should be back on it tomorrow, though.
I've revised the sheet metal portion already, just have to redo the mounts and recovery points and think about bracing for swingout pivots..
Who do you work for? Ima give em a call. :bash:
 

eimkeith

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today it was tenants in our building; someone clogged a lobby toilet and sent floaters drifting out into the common space and into a suite. (and here I thought renting office space was going to be easy money)

shitty morning.
 

Dezert4Runner

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today it was tenants in our building; someone clogged a lobby toilet and sent floaters drifting out into the common space and into a suite. (and here I thought renting office space was going to be easy money)

shitty morning.
Shit happens ;)

Looking forward to the finished product. Always assessing my options for a reasonable rear bumper. I like what I’m seeing so far!
 

eimkeith

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Shit happens ;)

Looking forward to the finished product. Always assessing my options for a reasonable rear bumper. I like what I’m seeing so far!


Thanks!

You can kind of see what I’ve cut off this thing since the prototype for additional clearance:

E777A750-4B7B-4B12-826D-08AA0A8D113C.jpeg0773C49E-7902-4189-AE31-3B2E033C9F86.jpeg2596FAC1-C6DA-472A-B10F-4D1A5C74C480.jpeg
 

Dezert4Runner

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The side wings are definitely on point. Anybody putting 35’s on after this bumper is mounted may have to cut that area. So it looks like you had the foresight to tweak it ahead of time, nice touch.

Any tire swingout plans in the works? Or is it something that mainly be designed later on down the road? I love how low pro this thing is and has better ergonomics than the Savage bumper (also one of my favorites). They did theirs right with the modular swingout design.
 
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