Front end shocks bottoming out!?

kyre · Post by **kyre** » Sun Jun 03, 2018 12:54 pm

I just put new Rancho RS9000 on the front of my 91 Delica l300 and now hear a clunk on certain bumps, but not all. It's doesn't matter if I adjust to the hardest setting. The Rancho's do have less compressed travel but more extended travel than stock (about 30mm longer compressed than stock).

I'm assuming I need to add taller lower bump stops? Sounds like I'm bottoming out the shocks before they get a chance to reach the bump stops. Can anyone confirm?

If I raise my front end (by cranking or reindexing torsion bars) will the extended travel these shocks have be utilized or are we limited by the upper/lower controls arms being a set distance apart?

I also have new rear Ranchos but when I went to install the compressed length just barely fit (about 30mm longer compressed length than stock) so I decided to keep the stockers on for now. I noticed my leaf springs were pretty much flat so I'm also assuming these need to be re-arched in order to lift the rear and have the new shocks fit properly?

Rear height from center of hub to top of wheel arch is around 49cm.

thanks for any insight. I looked around the forums of course but nothing specific to this that I could find.

kyre · Post by **kyre** » Sun Jun 03, 2018 1:35 pm

Just took my front lower bump stop off the drivers side (to see if the auto parts store has any a bit taller) and it's cracked anyways so probably need new ones no matter. Also looked at my shocks again and sitting on relatively flat ground there's no a ton of compressed travel left. I want to raise the front end by cranking the torsion bars but the fact my rear is at 49cm as well as my front currently I don't want the fronts taller.

Post by **Growlerbearnz** » Sun Jun 03, 2018 4:51 pm

You definitely don't want the front shocks bottoming out- the Ranchos don't have any internal bump stops and can be damaged. Hopefully that rubber bump stop is the culprit- you'll replace both sides, right?

Which Ranchos did you fit? RS999188 are 9" compressed where stock shocks are 8.5" compressed, but I can't imagine Mitsubishi would have made the tolerances *that* tight that an extra 1/2" would cause them to bottom out. I doubt you'll need longer bump stops with the RS999188's

The rear Ranchos sound like they might be too long though. If they're too long with the suspension at rest, what happens when it gets slammed into the bump stops? Even with re-arched springs, the length of travel will remain the same.

Your rear springs are tired. The 3 upper leaves shouldn't be touching the lowest, fattest leaf unless the van is heavily loaded. Check out this thread: http://www.delica.ca/forum/viewtopic.ph ... 0&p=138750
TL;DR: If/when you have your springs re-arched, *dont* re-arch the lowest leaf. Leave it flat.

I would suggest adding air shocks to the rear (viewtopic.php?f=100&t=18793). On my van at 30psi (considered a low pressure by Monroe) they added just enough lift to bring it back to stock height, and I can pump them up to eliminate any sag when I have something heavy in the van.

kyre · Post by **kyre** » Sun Jun 03, 2018 5:16 pm

oh man, I think I was fed some wrong intel as my front's are RS999166 which the min length is 9.750 (stock is 8.5 like you mentioned). The rears are RS999334 which have a min length of 12.360 (stock is 10.9). The Monroes (Front - 550012) have a min length of 9.375 and I haven't heard bad things from a friend who has them.

Not sure I can return the rears since it's been too long since I bought (Already have the fronts on so they're used already, but maybe I need to put the stocks back on for now until I can pony up some more money). I'll email Rancho and ask if I can exchange directly.

I saw your post about the air shocks. They sounded experimental so I didn't want to go that route but if they've been going good for you I think I'll consider them. They mention a compressed length of 12.250" which is around the compressed length of my Ranchos. Is that because air shocks can just be pumped up to gain more travel?

I just temporarily put a 3mm spacer under the bump stop. I haven't driven it yet so I don't know if that little extra would make a difference. Tomorrow.

Post by **Growlerbearnz** » Sun Jun 03, 2018 7:32 pm

I wonder if shock manufacturers measure shock length from different points? You're right, on paper the Monroes are 1.3" longer than stock (about the same as your 30mm Ranchos), but they fit really easily and from memory had plenty of travel left when the suspension was on the bump stops.

Maybe I'll double-check the rear shocks' travel next time I have the van in the workshop.

kyre · Post by **kyre** » Mon Jun 04, 2018 12:09 am

Wouldn't re-arching the leaf springs increase the distance from the top eyelet to the bottom mount? Wouldn't this make the longer shocks have more compressed travel?

I think I had a little room to compress when on but not much.

I feel like my rear end (and front if I want them even) is about 4cm lower than it should be. I'm at 49cm from center of hub to wheel arch and I heard I should be around 53/54cm?

sk66 · Post by **sk66** » Mon Jun 04, 2018 7:02 am

kyre wrote:Wouldn't re-arching the leaf springs increase the distance from the top eyelet to the bottom mount? Wouldn't this make the longer shocks have more compressed travel?

Not really... it just makes it sit at a higher point in the travel range when at rest. Think of the springs/torsion bars as "helpers"... they take a certain amount of load off of the shocks, but they don't change the travel range.

Taking more load off of the shocks can help prevent bottoming of the shocks simply because they aren't having to do as much, but that can make the whole suspension much more stiff/harsh. Kind of like a rigid framed motorcycle...

kyre · Post by **kyre** » Mon Jun 04, 2018 9:47 am

So if I want these components to function properly I may have to lift the van? Would this kit allow my longer shocks to work properly? https://www.delicaliftkits.com/

Post by **Growlerbearnz** » Mon Jun 04, 2018 8:43 pm

The problem you're trying to solve is "what happens when the rear axle hits a big bump". The axle gets pushed up until the bump stops contact the chassis and arrest the upwards motion. The shocks need to be short enough to allow this to happen. If the shocks are too long, the bump stops won't hit the chassis, and the shocks will take all the load.

Lifting the van won't change that. The bump stops are still the same height, and the axle can still move upwards far enough for the bump stops to hit the chassis. (It'll take a bigger bump to do it, sure, but it's still possible).

You need to measure some things and do the math to figure out if your shocks are short enough.

Here's my van's measurements with the Monroe air shocks entirely deflated:

: Measurements.JPG (285.38 KiB) Viewed 7620 times

I estimated that the axle can move upwards by 30mm by measuring from the chassis rail to the clean, worn line on the bump stops, which is created when they deform from hitting the chassis rail. The actual measurement was closer to 25mm but I added 5mm for luck.

: BumpStop.jpg (168.94 KiB) Viewed 7620 times

I measured the length of the shock at rest between the lower edge of the dust shield, and the weld on the lower part. At rest this measurement was 95mm. I undid the lower mounting nut and, using a crowbar for leverage, pushed the shock closed as far as it would go (not pictured). The measurement reduced to 60mm. 95mm - 60mm = 35mm of upwards movement possible.

: MEasureShocks.jpg (122.25 KiB) Viewed 7620 times

So, from rest the axle can move upwards 30mm before the bump stop limits the movement. My shock absorber can move 35mm, which suggests that the shocks have 5mm more travel than I need. Pretty close, but still ok.

But wait, it gets better because the shocks are at an angle. 30mm of upwards movement at the axle doesn't mean they get 30mm shorter. 3rd grade geometry to the rescue:

: Math.JPG (234.99 KiB) Viewed 7620 times

When the axle moves 30mm upwards, the shocks get 26mm shorter. The shocks have 35mm travel between rest and their bump limit, which means I have not 5 but 9mm more travel than I need. Awesome.

9mm would normally be a bit close for comfort- the bump stops could easily deform 9mm further than usual under an extreme load. Fortunately the Monroe shocks have an internal bump stop, so even if they reach the limit of their travel they shouldn't be damaged.

kyre · Post by **kyre** » Tue Jun 05, 2018 9:01 am

Wow thanks for going to such great lengths Growlerbearnz! This helps a lot to understand what I need to do to measure how much compressed length I need (until the bump stops make contact) vs what my shocks will give me. It's a bummer the Ranchos don't have internal bump stops, wish I would have known (or thought to look) before purchasing.

I get lifting won't change the fact the shocks could bottom out before making contact with the bump stops, but I would get a bit more travel and I'd just have to get taller bump stops right?

I'm assuming when people lift their vans they must get taller bump stops (front lower) or purchase shocks with internal stops to prevent the compressed state from bottoming out.

Post by **Growlerbearnz** » Tue Jun 05, 2018 2:47 pm

kyre wrote:Wow thanks for going to such great lengths Growlerbearnz!

No worries. When I installed the Monroes I pretty much eyeballed it, but after looking at your numbers I was getting paranoid anyway.

kyre wrote: I get lifting won't change the fact the shocks could bottom out before making contact with the bump stops, but I would get a bit more travel and I'd just have to get taller bump stops right?

That's the one, though with a re-arch you're gaining bump travel at the expense of droop travel- the total travel stays the same.

Taller bump stops is an option, though you have to be careful they're no harder than the stock ones- the stock ones are presumably designed with a softness and shape that won't overload the chassis rail. Another option would be to add a 1" (or whatever clearance your shocks need) thick block of plastic to the chassis rail. Even a piece of hardwood (painted black for discretion) might do the job- it's only going to be touching very occasionally.

kyre wrote:I'm assuming when people lift their vans they must get taller bump stops (front lower) or purchase shocks with internal stops to prevent the compressed state from bottoming out.

I think most people just throw the new shocks on and go "There, I fixed it". And 6 months later "Those XXXXX brand shocks are shit, they failed after only one trip off-road".

They should *really* be doing what you're doing- measuring, testing, thinking about how it's going to work. Speaking of measuring and testing:

On my front suspension I put the chassis on axle stands, removed the bump stops (upper and lower), completely loosened the torsion bar adjuster at the back, then lifted the front wheel up and down as far as it would go. The suspension arms hit the chassis before the shocks bottomed out.

kyre · Post by **kyre** » Wed Jun 06, 2018 7:23 am

That's a good way to check the articulation of the front shocks and see if they bottom/top out! I'm going to try that and see what's happening.

BTW what front shocks do you have on yours?

thanks again! Time to figure this all out...

Post by **Growlerbearnz** » Wed Jun 06, 2018 3:42 pm

kyre wrote:BTW what front shocks do you have on yours?

Pro-Comp ES9000 part number 913515. Allegedly 9.25" compressed, 13.96" extended, but I think they're measuring from different places because they seemed shorter.

They're great off-road, nice and soft, but on the road they could be a bit stiffer to control the van's heavy nose better. I'm seriously considering fitting Rancho RS999188 so I can adjust them to be stiff for road/towing use, or soft for the fun stuff.

kyre · Post by **kyre** » Thu Jun 07, 2018 5:26 pm

So I went on a long, winding, bumpy mountain road that I drive a lot and since putting in the 3mm spacer under lower bump stop the van drives like night and day.

Those 3mm must have just been enough height to not allow the shocks to bottom out anymore. Now I just have to order some new lower bump stops since one of mine is broken anyways.

I’m still going to take the wheel off and loosen the torsion bar like you did Growler to actually see the articulation but I’m happy now.

I started in setting 7 then 8 then 9. They all felt pretty good but 9 stiffened the front end up where I felt most stable around turns.

I know this road well and know where the major bumps are because my van with the stock shocks would bounce up/down up/down where I felt almost out of control if going too fast. Now the van actually absorbs these bumps I dreaded so much before.

Gonna try the rears soon. Might get one of those 1.5” Delica lift kits to utilize the extra length I have now.

Post by **Growlerbearnz** » Thu Jun 07, 2018 5:47 pm

I think you'll find that once you replace those lower bump stops, you won't need the 3mm spacers- but they won't hurt either.

Consider upgrading the torsion bars, it really makes a difference to the "wallowy" front end. Check out this thread: http://www.delica.ca/forum/viewtopic.php?f=10&t=18844