Suspension upgrades on a T1N Interstate

[InterBlog]

This thread is a follow-on to Catastrophic tire blow-out in an Interstate.

TL;DR recap – I blew the streetside rear tire on my T1N Interstate van (THIS IS NOT A TRAILER THREAD) several weeks back, and the root cause of that failure was never determined to my satisfaction. On the Catastrophic thread, knowledgeable posters theorized that it was a pressure-loss failure which occurred following either negligence in the form of overloading or excessive speed or excessive tire age, OR damage due to debris, or some other cause such as historical latent damage that didn’t fully manifest until the day of the blow-out,... anyone one of a number of these structural problems that resulted in the tire becoming underpressured while under travel, and thus susceptible to failure in the form of blowing out.

The problem with those theories is that none of my observed or recorded data fit them. I won’t repeat all that detail here because it’s on the other thread.

Fast forward to this present thread.

My suspicion is that, WHETHER OR NOT some kind of pressure-compromising damage did result in that blow-out, my suspension may have played a role in it. I was concurrently unhappy with the condition of the suspension even before the blow-out (I was experiencing steadily-degrading handle-ability). The suspension and the tires are locked in intimate conversation because whatever adverse forces are not adequately dissipated by competent suspension components are essentially transmitted through to the tire sidewalls.

Therefore, it was time for upgrades, as we seek to improve our safety margins. We had replaced the original components with an upgraded sway bar and Koni shocks on the rear in late 2014, also due to handle-ability problems at that time (and that upgrade resulted in a dramatic improvement). We also replaced the front struts with a Koni product some years later (I’d have to go back and look up the date). The van is traveling at GVWR, however, and we have no real precedent on how long we should expect such components to last when placed under very heavy demand.

Our boxes from Van Compass arrived last night, and it looks like Christmas morning in our garage. We have heavy work days (we are both employed) today through Saturday, but I will slowly post our installation progress and details as to what these new fittings consist of.

Meanwhile, a pic:

[InterBlog]

Working, due to an unexpected meeting cancellation this morning for my husband...

Shocks comparison. We emailed a series of pics of the chassis areas to Van Compass, which recommended these over the Fox shocks that are considered by many to be the best available option for the T1N Sprinter.

We are currently working on two minor but important fit issues that we need to overcome, so we are not yet sure if these can be adapted. But here's what they look like, FWIW.

[InterBlog]

Falcon shocks installed. Husband says we are the first T1N Sprinter owners ever to install them (you'll notice that they say 2007-plus on the label, which indicates that they were designed for the NCV3 Sprinter).

There is one aspect that we need to discuss and confirm with Van Compass before I comment further, but for now let me say that we did take them for a test drive this evening, and I'm cautiously optimistic about their suitability.

With our busy schedules, we need to take them on the road tomorrow morning. No time to replace the front struts before we leave.

[InterBlog]

Two observations, after traveling about 360 miles on the Falcon shocks and Sumo springs:

(1) Observation for people who are annoyed by the Sprinter’s rocking motion while parked, with preamble:

Ideally if we were trying to isolate handling issues and associate improvements with a specific component, we would make one change at a time. But then real life intervenes, and it’s far easier to replace shocks and springs simultaneously when the weight is taken off the drive axle. The upshot of that is, I don’t know whether to attribute handling improvements to one, the other, or both, although I suspect both are contributing.

Prior to this transaction, I knew diddly about Sumo springs. For the T1N Sprinter, here’s the OEM with the replacement side by side:



I had heard about Sumo springs, heard some Sprinter owners rave about them, but I had also heard my husband complain that they are at odds with the OEM Sprinter design. They work by replacing what is essentially a bump stop (you can see the impact surface area wiped clean in this photo below, crude red arrow pointing to it) with a device that remains in contact - in fact, appears to lift the rear end by about an inch:



One effect of this which I think is attributable mostly to the Sumo springs rather than the shocks - the Interstate no longer rocks when parked. Prior to this, (for instance) if our dog shifted her position in the middle of the night, the Interstate would sway in response to her movement - it was extremely sensitive. This didn’t bother me, but it bugs the hell out of some owners, I remember from past threads. So if you want to make that kind of movement all but disappear, Sumo springs might be something to consider.

(2) After this replacement, my rear end behaves much better, so to speak. My front end doesn’t communicate optimally with my rear end at this point, but we still need to replace the struts, which are still sitting on the floor of our garage due to lack of scheduling opportunity.

I notice a big reduction in oscillations (which affects the tires) and also far better cornering ability, with these two new components on the rear. I’m not an automotive guru, so I was surprised at the improvement in cornering. I would have thought that to be dictated mostly by the condition of the front end, but apparently not.

[ITSNO60]

Did you notice any increase in harshness on bumps or potholes? This seems to be the only real complaint from some of the Sumo Spring users, although a very small percentage of reviewers mention it. I am on the fence, thinking of upgraded sway bar and shocks first. If that helps the sway and body roll enough I may skip the Sumo Springs, I don't really need the ride any harsher than it already is. There is always a trade off.

[Rocinante]

Thanks, IB.
Definitely interested in your longer-term experience with Sumo springs as well as your shocks and struts. As ITSNO60 noted, I have read from owners of the 3500 EXT Sprinter that Sumo springs can produce a harsh ride. Perhaps that's not the case with your T1N, which would be cool.
BTW, given your new rear shocks appear to be adjustable, how did you know what setting to use?

[InterBlog]

Originally Posted by ITSNO60

Did you notice any increase in harshness on bumps or potholes? This seems to be the only real complaint from some of the Sumo Spring users, although a very small percentage of reviewers mention it. I am on the fence, thinking of upgraded sway bar and shocks first. If that helps the sway and body roll enough I may skip the Sumo Springs, I don't really need the ride any harsher than it already is. There is always a trade off.

The Sprinter, whether T1N or NCV3, whether 2500 or 3500, is harsh no matter what we do, because it was designed to be a cargo van. Ours was harsh before we made these mods, and it continues to be harsh afterward. To me, it’s six of one, half a dozen of the other. (We would have gone with air suspension had it been available for the T1N Sprinter in America, which it was not.)

My husband has different opinions, however, and he will likely play around with the Falcon shock adjustments to see if he likes the ride better one way or the other. The Falcon shocks are independently adjustable on both compression and rebound.

As long as I don’t have handling issues, I don’t care what is set to do what. The primary key for me is safety. The secondary (and related) key for me is handling, because poor handling demands more brain cells than I can spare to counteract it, and it’s exhausting.

[InterBlog]

Well, here’s a coincidence. MB issues a recall for stability problems just as we are in the process of trying to suss out the reason why we have stability problems. Except the recall does not extend to our MY.

[JC2]

I received my notice today also.
Don't know if speed sensors will be replaced again since they were replaced last August at 93,000 miles. Did get a code during the recent freeze but it cleared itself.
Hope the new ones are more waterproof.

[Titus]

I think you are mixing apples and oranges. The recall is because a failed WSS will cause the ESP to shut off (and ABS and BAH/ASR and cruise control shuts off too). It is odd that the recall focuses only on ESP - maybe that is the 'hook' that got NHTSA involved.

[InterBlog]

Given the comprehensive impact that recall will have on members of this forum, I expect someone will start a new thread on it, but by all means discuss it here too.

I don't know how much difference there is between the wheel speed sensors (WSSs) used on T1N vs. NCV3 models.

Independently of my stability issues, I have noticed an increasing divergence between the velocity my van reports, vs. the velocity my standalone Garmin GPS reports - it's up to approx. 5 mph, and the Garmin is clearly more accurate. Husband said, "Oh, that's just because we got new tires." Well, it seems to be a lot to attribute to same-sized, almost-identical tires. But what the heck do I know.

[Titus]

I don't think the wheel speed sensor provides input to the speedometer - least I don't recall that the speedometer quit working when the WSS did. From what (little) I understand about the WSS they don't degrade (provide an increasingly inaccurate signal). They either work or not, though the working or not can be intermittent. We the suite of dashboard warnings that later cleared, then a front WSS failed 1000 miles later.

[Boxster1971]

Originally Posted by InterBlog

Given the comprehensive impact that recall will have on members of this forum, I expect someone will start a new thread on it, but by all means discuss it here too. . . .

Taking your lead - started a new thread on this recall here:

https://www.airforums.com/forums/f24...ml#post2471890

Sounds a bit like Daimler Vans is implying that RV manufacturers have caused this issue.

[Hawk-ination]

I agree Titus, it’s apples and oranges. Good to separate the two.

Glad you are tackling the suspension. One of those things you’re better safe than sorry.

[InterBlog]

Bilstein struts are finally going on the front this evening, with the Sumo front springs.

Meanwhile, with my husband's help, I'm turning the old rear bump stops into tea light candle holders. It wasn't as difficult to drill out a center hole as we thought it might be. This rubber has been under the van taking a pounding for the past 14.5 years. It has lost a lot of its strength and elasticity.

I'm as absent-minded as freak, so I don't allow any open flames in my house. I prefer LED candles, although I might try to find a fancier tea light than this really cheap version.

It's a beautiful shape, design-wise - I didn't want to throw them out. I just gave them a good scrubbing after we drilled the center hole, and voila. Industrial chic.

[Hittenstiehl]

Well some good news in all of this. Those turned out really nice! They have really nice LED flameless tea lights now that even have a little bit of a flicker to them.

[MMSsprinter]

What's the verdict on this set up? I just purchased an 04 and it needs a major suspension upgrade.

[InterBlog]

Originally Posted by MMSsprinter

What's the verdict on this set up? I just purchased an 04 and it needs a major suspension upgrade.

Welcome to Air Forums. When I saw your username in the list, I mistakenly thought you were Joel, the owner of Million Mile Sprinter, because his acronym is MMS. From your ID tile, you are located 325 miles from him, and if you ever need work done on your T1N, I recommend him. He's one of the best T1N mechanics in America, to the point where I would actually drive from Houston to Philadelphia to have him work on my Interstate (and I have).

Anyway, I have been very pleased with the Falcons on the rear of our van. However, I never did get around to double checking with VanCompass about the install. The Falcons were designed for the NCV3, which has different frame rails, so in order to mount them properly on a T1N, they need to be reversed for the reservoir to be in the right position.

In a perfect world in which all T's a crossed and I's dotted, I would have gotten around to having that revert-back discussion with the seller, but alas, I never did. The proof has been in the pudding, though. VanCompass sold them to us believing that they would function as designed if they were installed properly for the model, and our Interstate handles better now than it ever did.

[MMSsprinter]

Thanks you for your input. Just coming off a 5K trip to CA and I definitely need to upgrade this suspension.