- Thread starter
- #101
M19 bolts look hard to find anyone know of a source? I’ve checked Fastenal and Bolt Depot. 3/4” is probably OK but I get hung up on keeping things metric.
Rear shock mount bending
- Thread starter kcjaz
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- mount rear rear shock shock
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- Thread starter
- #103
Hey @Turbo, I was looking at your shock mount relo bracket and thought it was essentially using the holes above the mounting pin as the relocated shock eye center but see that your bracket offsets that a bit.
If I just through bolt my BP51 shocks through those higher holes, the change in angle will cause the upper mount bushings to be compressed at a different angle than the OEM setup but will that really cause an issue? The angle changes as the axle goes up and down. Did you design your bracket to maintain the angle or to make it a bolt on mod not requiring enlarging the stock holes to accommodate a 3/4” bolt?
Here’s a couple photos I found of the 3/4” bolt we used and a small sleeve of steel tubing welded to a small square of plate to space out the lower shock from the support. Seems to have worked fine and is still the same. I like the idea of cutting off the bottom of my lower shock support too but I just can’t bring myself to do it.
Hope this helps if this is the route you take.
I also have LX600 shocks sitting on the shelf to eventually try seeing if they could even mount in this same location and give just a little more droop.
Yeah, my spacer moves the shock mount up and inboard to keep the bushing in a more oem position.
Compared to hole above oem pin.
So this is my plan. I've seen a couple post about enlarging the upper hole to accept a proper sized bole for the shock, welding it in properly the cutting the lower mount off.
I've put in Perry parts extended bumps in and have checked, looks like they will work perfectly for that second hole. I also have metal tech LCAs and they give extra movement in the axle
Do you think the bent shock mount and enlarged upper hole was from the Swell?
Make sure the rear springs, mainly the drivers side, won’t fall out at full droop. Also expect to extend the diff breather hose and the brake lines… not that I’ve done this, but I did look into it. Of course make sure shock doesn’t bottom out - remember the PP bumps are progressive so there likely will be more travel than just sitting on them without springs installed.
I’m looking forward to following along and eventually doing something similar one of these days…
Springs stay in, will probably add a redundant retainer though. And yeah diff/brake lines are on the parts table just haven't done it. I'm on dobinsons mrr and after a through compression test at uwharrie I'll have about 1/2 gap before bottom out
- Thread starter
- #109
The bent mounting pin didn’t happen in the Swell. It was all bent before.
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- #110
Awesome! That’s essentially what I had in mind but with the bolt flipped around so the nut is on the back side to protect it.
I think the first thing I need to do is figure out if the shocks will bottom out before the bump stops limit travel. I have Timbren active off road bump stops and they are kinda like progressive springs so I’m not sure how to figure out what their maximum compression is. I can remove the springs and put the
weight onto the truck on them but thats not the same hitting something at speed. That’s what @linuxgod was referring to at the Swell when we both hit a dip at speed and launched all 4 tires off the ground. If I was bottoming the shock before that jump would have broke something.
- Thread starter
- #111
So took some measurements and scratched my head a bit with some trigonometry and think I’m ok from in a max compression scenario. Someone please correct me if I’m not thinking correctly here but if I was OK before, and my bump stops bottomed out before my shocks, raising the lower mounting point is irrelevant, I’m still ok. From the suspension’s point of view, all I’m doing by raising the bottom mount height is compressing the shock to some other point within its travel limits. The bump stops don’t care where the shockers are or the axle was at normal ride height. It still stops the axle before the shock bottoms out.
So really, all I’ve done with measurements and math is confirm that my current setup is OK with shock travel in max compression. The bottom line is my shock’s max compressed length is 16.5” and the bump stops limit compression to 17.3” so I’m good. Raising the mount doesn’t affect his number.
For posterity (and in case someone is interested enough to check my logic and math) here are my measurements and calcs:
(I did confirm AI’s answer to my shock travel query with actual measurements).
So really, all I’ve done with measurements and math is confirm that my current setup is OK with shock travel in max compression. The bottom line is my shock’s max compressed length is 16.5” and the bump stops limit compression to 17.3” so I’m good. Raising the mount doesn’t affect his number.
For posterity (and in case someone is interested enough to check my logic and math) here are my measurements and calcs:
(I did confirm AI’s answer to my shock travel query with actual measurements).
If you have 2” of shaft today and shrink the shaft by 1.2” then I’d agree you won’t bottom out.
A separate question though - does ARB leave that 2” for a reason? Your shock is pressurized and is that 2” essentially the oil capacity? By dropping to 0.8” remaining are you doubling the pressure on the oil and risking blowing out a seal?
The way your shaft bent I’m still not convinced it didn’t effectively bottom out (being unable to compress fast enough), even if it didn’t actually bottom out. But I know very little
UPR LC
GOLD Star
Any chance you can look at your current shock and see how much of the shaft is "clean" versus dirty?
The extent of the clean shaft would be a good indication of how much the shock compresses, assuming you have flexed the rig recently.
If there is x" of dirty (non-cycled) shaft and you are raising the shock mount less than that dimension, you should be good.
The shock should not care where in the travel the truck normally rides as long as you don't have bypass shocks. As long as the shock is not hitting the ends of its travel.
- Thread starter
- #115
Good points. I suppose rate of movement is a factor. I’m convinced I have enough total travel to be ok as long as the shock can keep up. I’d think the design pressure would account for that though and seals would be ok. With the mount moved up, I guess I’m hitting each bump with the shock higher in its travel. I’m not sure how that would matter. The shock still sees the same extreme. Anyway, I’m not sure what else to do to check it.
I ran with OEM bump stops for a few years. I don’t have the measurements but I’m sure I’d have less margin with the ORM set up. The bending started with the BB guards. This is primarily why I think I was ok before and still am ok if I move the mount up.
Check were the ride zone turns into the bump zone in the BP51s. I don't think you will want to be driving around when it is in the bump zone.
UPR LC
GOLD Star
I didn't realize this about the BP-51's, but my response above with the "unless you have bypass shocks" seems to actually be applicable to the BP-51s.
BP-51 Compression & Rebound
arbusa.com
You may want to do some more digging in regards to the BP-51 design before you move the mount. As it sounds like damping may be shaft-position sensitive.
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- #118
@turbo8 and @UPR LC comments on about bypass shocks good ones. I put the tire back on and measured normal rest height (shock length):
Max compression shock length = 16.5”
Normal ride height (truck unloaded) = 22.25”
Max shock extension = 25.1”
Total max travel = 8.6”
So, at normal ride height, I have 2.9” of theoretical droop (25.1-22.25) and 5.7” of upward compression travel (22.25-16.5). I’m not sure where in the travel range the “comfort zone” really is. AI says the “comfort zone” is in the middle of the shock travel which sounds reasonable but I can’t find an ARB document that says or shows this. AI also says that “ARB recommends there is roughly 2.5” of travel available for the rebound loop.” I’m not exactly sure what that means but I think that is the difference between normal ride height and max extension. If so, I’m at 2.9” (OEM shock mount location) which is close to 2.5”. If I move the mount up 2” I’ll be at 4.9” which is close to the midpoint of travel but probably not optimal for the BP51 shocks in terms of normal driving comfort.
I’d love to see an ARB diagram of the bump, comfort, and rebound zones.
Max compression shock length = 16.5”
Normal ride height (truck unloaded) = 22.25”
Max shock extension = 25.1”
Total max travel = 8.6”
So, at normal ride height, I have 2.9” of theoretical droop (25.1-22.25) and 5.7” of upward compression travel (22.25-16.5). I’m not sure where in the travel range the “comfort zone” really is. AI says the “comfort zone” is in the middle of the shock travel which sounds reasonable but I can’t find an ARB document that says or shows this. AI also says that “ARB recommends there is roughly 2.5” of travel available for the rebound loop.” I’m not exactly sure what that means but I think that is the difference between normal ride height and max extension. If so, I’m at 2.9” (OEM shock mount location) which is close to 2.5”. If I move the mount up 2” I’ll be at 4.9” which is close to the midpoint of travel but probably not optimal for the BP51 shocks in terms of normal driving comfort.
I’d love to see an ARB diagram of the bump, comfort, and rebound zones.
- Thread starter
- #119
From the marks on the chrome shaft, it looks like I’m using 6.5” of the theoretical max of 8.6”.
@turbo8 and @UPR LC comments on about bypass shocks good ones. I put the tire back on and measured normal rest height (shock length):
Max compression shock length = 16.5”
Normal ride height (truck unloaded) = 22.25”
Max shock extension = 25.1”
Total max travel = 8.6”
So, at normal ride height, I have 2.9” of theoretical droop (25.1-22.25) and 5.7” of upward compression travel (22.25-16.5). I’m not sure where in the travel range the “comfort zone” really is. AI says the “comfort zone” is in the middle of the shock travel which sounds reasonable but I can’t find an ARB document that says or shows this. AI also says that “ARB recommends there is roughly 2.5” of travel available for the rebound loop.” I’m not exactly sure what that means but I think that is the difference between normal ride height and max extension. If so, I’m at 2.9” (OEM shock mount location) which is close to 2.5”. If I move the mount up 2” I’ll be at 4.9” which is close to the midpoint of travel but probably not optimal for the BP51 shocks in terms of normal driving comfort.
I’d love to see an ARB diagram of the bump, comfort, and rebound zones.
- Thread starter
- #120
I’m confused (which is pretty easy for me). I’m thinking about raising the lower attachment point, not making it lower. The thing that isn’t getting through my skull is that, I think the bump stops currently prevent the shocks from ever getting to the theoretical max compression point. The marks on the shafts imply I am only using 6.5” of the available 8.6” of travel. If that is true, I don’t understand what difference it makes where the shock starts within its available travel.