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Old 06-19-2021, 07:47 PM   #1
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Default Color-changing Sumo Springs?

My yellow rear Sumo Springs have undergone a color-change to a deep reddish/brown color in just 4 months since install.

They are not exposed to sunlight, so that is not the reason for the change. I rubbed and lightly scrubbed an area on them in case some kind of road spray had covered them. The reddish/brown did not rub off. The right one is only 7" forward of the exhaust pipe, but if it were heat-related, I'd think it would only affect the rear side closest the pipe. Yet it is uniformly discolored and so it the left side which is far away any such heat source.

Normally, color-change is a bad thing. The only times I've observed this on other plastics, it was due to UV exposure and degradation due to to weathering. The material seems as solid and firm as when installed, but it's got me worried enough to contact Sumo Springs.

Before I do, is this normal for those of you who've installed their yellow bump stops?
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Old 06-19-2021, 08:14 PM   #2
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Originally Posted by rowiebowie View Post
My yellow rear Sumo Springs have undergone a color-change to a deep reddish/brown color in just 4 months since install.

They are not exposed to sunlight, so that is not the reason for the change. I rubbed and lightly scrubbed an area on them in case some kind of road spray had covered them. The reddish/brown did not rub off.

Normally, color-change is a bad thing. The only times I've observed this on other plastics, it was due to UV exposure and degradation due to to weathering. The material seems as solid and firm as when installed, but it's got me worried enough to contact Sumo Springs.

Before I do, is this normal for those of you who've installed their yellow bump stops?

From reviews it appears that is very common. I think they are urethane but don't know if thermoplastic or themosetting urethane.
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Old 06-19-2021, 10:17 PM   #3
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I've never looked at mine, but others that have looked have reported the same color darkening. If you are concerned, I would call Super Springs and ask them. They are friendly people...
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Old 06-19-2021, 10:39 PM   #4
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Thanks for both replies. If it's normal, then I won't worry. But it seems very odd to me they would change color so quickly and that they'd pick such a bright yellow to start with (makes the change more noticable). They sell black, blue, and yellow bump stops so why not make them red or orange in the first place?

The change seems to be related to the outside environment, since they sat in a box in my house for nearly the same period before they were even installed and retained their original yellow color. The polyurethane had a slight oily feel when new and they've lost that. But other than that (and the color), no other change.
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Old 06-20-2021, 01:37 AM   #5
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Thanks for both replies. If it's normal, then I won't worry. But it seems very odd to me they would change color so quickly and that they'd pick such a bright yellow to start with (makes the change more noticable). They sell black, blue, and yellow bump stops so why not make them red or orange in the first place?

The change seems to be related to the outside environment, since they sat in a box in my house for nearly the same period before they were even



installed and retained their original yellow color. The polyurethane had a slight oily feel when new and they've lost that. But other than that (and the color), no other change.

The oily feel is the plasticizer coming out, most likely, and it does it until the surface is depleted. In tires it is intended to come out forever to prevent surface degradation and you get the same brownish coloring on the surface of the tire. In tires they are designed to push out the plasticizer as you drive with weight on them, eg flexing, so that is why sitting is so bad for tires.
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Old 06-20-2021, 02:06 AM   #6
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The oily feel is the plasticizer coming out, most likely, and it does it until the surface is depleted. In tires it is intended to come out forever to prevent surface degradation and you get the same brownish coloring on the surface of the tire. In tires they are designed to push out the plasticizer as you drive with weight on them, eg flexing, so that is why sitting is so bad for tires.
Well that may explain the difference in the yellow (while just sitting 4 months in my house) - vs - the reddish brown (after repeated compression by the rear axle for 4000 miles) perhaps releasing something from the polyurethane.
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Old 06-20-2021, 11:18 AM   #7
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My yellow rear Sumo Springs have undergone a color-change to a deep reddish/brown color in just 4 months since install.

They are not exposed to sunlight, so that is not the reason for the change. I rubbed and lightly scrubbed an area on them in case some kind of road spray had covered them. The reddish/brown did not rub off. The right one is only 7" forward of the exhaust pipe, but if it were heat-related, I'd think it would only affect the rear side closest the pipe. Yet it is uniformly discolored and so it the left side which is far away any such heat source.

Normally, color-change is a bad thing. The only times I've observed this on other plastics, it was due to UV exposure and degradation due to to weathering. The material seems as solid and firm as when installed, but it's got me worried enough to contact Sumo Springs.

Before I do, is this normal for those of you who've installed their yellow bump stops?

Hi: Mine did the same after just 2 months of use. I have read this is normal so no worries. Unknown to me reason? They just change color.
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Old 06-20-2021, 06:53 PM   #8
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Hi: Mine did the same after just 2 months of use. I have read this is normal so no worries. Unknown to me reason? They just change color.
I didn't look underneath until 4 months, so you're saying mine probably began changing color sooner. Very likely.

Just seems to me they'd want to avoid this type of question and make them in a darker color to begin with. For example, my front black ones are still black.
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Old 06-20-2021, 09:40 PM   #9
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I didn't look underneath until 4 months, so you're saying mine probably began changing color sooner. Very likely.

Just seems to me they'd want to avoid this type of question and make them in a darker color to begin with. For example, my front black ones are still black.
I had black ones too. They stayed black entire time on my van. They looked really good. I think the yellow ones are color coded. Maybe cost to change and stabilize color is too costly a manufacturing cost? Lots of people on Facebook Travato forum also commented on color change. I personally liked the yellow color.
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Old 06-21-2021, 01:09 PM   #10
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You guys just spend too much time peering under your rigs. lol I've never looked at mine since they were installed. As long as they are still working, I'm good.
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Old 06-21-2021, 02:13 PM   #11
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Don’t wish to push this thread off in another direction but I’m researching Sumos for my ‘17 Pleasure-Way Plateau TS. How do you choose between the 900# (black) and the 1400# (Yellow)? I don’t tow anything, but wonder if the stiffer 1400# sumo would have a better damping effect or just make the ride harder.
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Old 06-21-2021, 04:25 PM   #12
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You guys just spend too much time peering under your rigs. lol I've never looked at mine since they were installed. As long as they are still working, I'm good.
Until my recent 3" lift, I'd agree with you. But now that I can actually slide under and take a look at all the wondrous things underneath, I'm like a kid in a candy store.

PS - In the past, I've had to re-attach tank heating pads (one was barely hanging on after a trip), so it's always a good thing to do periodic inspections.
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Old 06-21-2021, 04:40 PM   #13
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Originally Posted by navcom48 View Post
Don’t wish to push this thread off in another direction but I’m researching Sumos for my ‘17 Pleasure-Way Plateau TS. How do you choose between the 900# (black) and the 1400# (Yellow)? I don’t tow anything, but wonder if the stiffer 1400# sumo would have a better damping effect or just make the ride harder.
Your concerns were the same ones I had.

Mine is a Chevy Exress and your's is a Sprinter, so it may not be a direct apples to apples comparison. But, my thinking was I needed the heavier yellow for the rear since it supports much of the coach conversion weight. And whether Chevy, Sprinter, or Promaster I haven't heard of anyone complaining they were too stiff.

It was a different matter in the front. The black (less stiff) bump stops were recommended on this forum. In addition, I've had communications off-forum with a couple of other Airstream Avenue owners (like mine) who complained of harsh front suspension impacts. In both cases, it seemed the prior owner had installed over-sized polyurethane bump stops that were not Sumo springs, but prevented normal front suspension travel and gave a feeling they described as "bottoming out". One changed to black Sumos and the other had their mechanic "shave off" their bump stops so it was no longer resting on the hard polyurethane.

Based on the above, it seems black front/yellow rear is the recommended way to go.
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Old 06-22-2021, 01:23 PM   #14
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Donít wish to push this thread off in another direction but Iím researching Sumos for my Ď17 Pleasure-Way Plateau TS. How do you choose between the 900# (black) and the 1400# (Yellow)? I donít tow anything, but wonder if the stiffer 1400# sumo would have a better damping effect or just make the ride harder.
You could always call Super Springs and consult the pros... but based on the fact that they have recommended the yellow for all of the Roadtrek Promaster conversions, I would expect that is what you need. I have both their front system and the yellow in the rear.
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