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I wanted to undercoat my Smart Car to protect it from road salt in the winter. I was asked if I wanted the rubber or the oil. Has anyone done this and have a preference?
 

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The wax or cosmoline type material would probably be a better choice IMO. The rubberized material would probably add more weight. Actually, I wouldn't do either if it were my vehicle. I would follow up with undercar washes after driving on roads where salt or brines have been used.
 

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For some time, since cars have had better design, treated panels and even partial undercoating of critical areas at the factory, it has not been recommended to have your car undercoated. Two of my cars, a 1977 and 1990, were undercoated by the original owners but I’ve not personally had any new cars I’ve purchased undercoated since the early 1980s. I live in an area where chemicals are applied liberally to roads in Winter but, as recommended in a previous post, wash the underside of the cars after roads dry. I’ve not experienced any rust issues since the early 1980s but sure did in new cars I purchased previous to that date.
 

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While an undercoat can help, the crud gets other places than just the underside. I'm slowly working toward getting my 2010 back on the road and as part of that I had to remove the drivetrain subassembly so I stripped it down for cleanup. There was some rust forming along portions of the seams and at most welds, much of it on the upper surface of the subassembly rather than the bottom side. I was expecting more damage, but it really wasn't bad for a northern car; nothing that wasn't relatively easily fixed. I've noticed a lot more rust on the 2010 than on my 2008, but I think it's probably due more to when the previous owners drove it than anything else; I suspect the 2008 rested most winters and the 2010 was used year-round.
So I would say it's still a concern, but I'm not sure an undercoat alone would change much, especially if the car has already seen the grime of winter.
 

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I live in the snow belt in upstate NY where salt is liberally applied to our roads to melt snow. There is so much salt used that in the spring, white salt deposits are common on the sides of almost all roads. I have used undercoating spray on my ‘08 smart every year since I’ve owned it and managed to keep the majority of rust at bay. Without it, I suspect I would be having much worse problems. I do drive my smart on snow-covered roads, but want to keep it healthy as long as possible.

As for adding weight, I think it’s negligible, less than a few pounds. I pull the belly pan and cover all the steel surfaces, top and bottom to the best of my ability. With any luck, it will help my little buddy to stick around for years to come.
 

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I would use a product like POR-15. Rubber undercoatings are known to do more damage than just leaving the metal untreated and some wax coatings are almost as useless.

Rubber undercoatings are really bad because if there's any imperfection in the coating at all, salty water will get into the coating and rot the metal.

That said, I think undercoating a smart is Our cars already have excellent rust protection on the tridion cell, most of the undercarriage is covered with a belly pan, and the metal subframes aren't too bad, either.

My 2012 has been through 8 Midwestern rust belt winters, 170k miles, and thousands of miles being beat up off-road. Not to mention, the car went three years without getting a car wash. The only real rust to speak of is my tow hitch. I put a rubber coating on it that did just as I mentioned above. My new to me 108k mi 2008 is also a Midwest car, it's clean aside from a cracked spring.

Honestly, just wash your car frequently in the winter and you'll be just fine.
 

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My 2012 has been through 8 Midwestern rust belt winters, 170k miles, and thousands of miles being beat up off-road. Not to mention, the car went three years without getting a car wash. The only real rust to speak of is my tow hitch. I put a rubber coating on it that did just as I mentioned above. My new to me 108k mi 2008 is also a Midwest car, it's clean aside from a cracked spring.
My 2010 came from your neighborhood. This is what it looked like after a first pass cleaning up the rust.
64194
 

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Oof! I wonder how frequently your 2010 has seen cleaning? I know a lot of midwestern people hand wash their cars (especially smart owners) which is kinda odd as what'll end up happening is the body looks nice and sparkly while the undercarriage is about to split in half. My former rally truck (a Ford Ranger) fit that description.

I do wish smart did more to the Dedion tube and subframe. I guess I would definitely recommend POR-15 for anyone that seeks to protect these parts. I use the stuff on motorcycles and more rust prone vehicles (older VWs) and the stuff works magic! :)

OH! Midwestern and Eastern 450 owners should DEFINITELY undercoat their cars. The 450s came from the factory with a hilariously thin wax coating for rust protection. What inevitably happens is a rock chip breaks the wax layer and the car (including the tridion cell) begins rotting out. The 2005 I got from Pennsylvania was pretty crusty underneath. Never peeled back the panels to see if the tridion was also rusting.
 

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Oddly, the De Dion tube wasn't nearly as bad as the seams and welds on the subframe. The rust wasn't terrible and I don't think anything was compromised. I went at it with the needle scaler, wire wheel, and a little sandblasting in the hard to reach corners before coating it all in POR-15. First time using the product so we'll see if it holds up to the hype. :)
I was expecting a fair bit of rust after pulling off the rear crashbar and seening a lot of surface rust there whereas the 2008 had none, ergo my presumption that the 2008 was likely garaged the winter and the 2010 driven in it.
 

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Just to be sure, are you guys discussing the electric smart? While all smarts have the same rear suspension, in other respects they are quite different.
 

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What really needs rust protection are the two rear tone rings or reluctor rings. They rust like crazy and can eventually crack, screwing up the ESP system. Thick undercoating would mess up their function, but a good cleaning and then a light coating of something like POR-15 or PB Blaster should extend their life. :)
 

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What really needs rust protection are the two rear tone rings or reluctor rings. [jwight]
Photos please!

Protectant Spray: Mix 1/3 90w differential oil (used is ok) with 2/3 hydraulic fluid (used is ok) and spray liberally to under-carriage. The 90w tends to creep and stick as anyone with a slightly leaking steering box knows. The hyd oil is a thinner to allow spraying easily. Do this at the start of the winter season and again after spring washing sraydown and complete drying out.
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Photos please!

Protectant Spray: Mix 1/3 90w differential oil (used is ok) with 2/3 hydraulic fluid (used is ok) and spray liberally to under-carriage. The 90w tends to creep and stick as anyone with a slightly leaking steering box knows. The hyd oil is a thinner to allow spraying easily. Do this at the start of the winter season and again after spring washing sraydown and complete drying out.
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I have my 2010 disassembled currently and can easily get images of the reluctor rings and axles both on and off the car. It's trivial right now to get detailed images, so if there's a desire to see rear assembly parts ask for them. If there's interest I can make a new thread.
 

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Whaa??

Supermoderator need to SuperSplain!!
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The ABS rings (or "reluctor rings") on our cars have an interesting design. The ones up front are for the most part sealed and safe from corrosion but the ones in back are exposed to all of the elements. The rings themselves appear to be untreated steel. Thus, after several hard winters they will rust, crack, and break. The readings from these rings are responsible for the operation of the ESP and ABS system. When they begin failing you may witness strange behaviour like the car activating traction control when it's not necessary or ABS activating when it's not necessary. Some people have even experienced a wheel locking up. "Best" case scenario is like with my two 451s where the rings fail and the ESP and ABS system simply disable themselves (great for off-roading! Ha).

The car does remain perfectly driveable after the rear rings fail, but you won't get the aforementioned ESP or ABS, Hill Start Assist, or the creep mode.
 

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OH! And I will say that the rear crash bar is definitely a bad spot for rust on these cars. Some folks with high mileage Midwest/East smarts have taken off their panels to reveal crash bars that were either crumbling or darn near close to it. I guess maybe the car's aerodynamics will suck salt into that area but even an underbody wash is likely to miss it?
 

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The relentless creeping of 90w gear oil is your friend as it will insinuate itself into all crevaces, nooks and crannies to provide rust protection. It will only wash off from open exposed surfaces, hence the 2x per year on these areas. So buy a quart of 90w and a gal of hyd fluid and a quality hand-pump pint-sized sprayer and go to work on these critical areas. Cost of project: under $20-US maybe @walmart.
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I’ve owned 40 new and used cars, in my life. Live in the Midwest. I’ve Never rust proof, and of my modern car. They really don’t require it. My old American made cars rusted out, even under coated. Same with my British cars. I worked at a Pontiac, and Chevy dealership, when I young. We use to drill holes in door panels and quarter panels etc. spray rust inhibitor into them. All it did was gum up the window regulators. The panels still rusted. Rubber, under coating was a waste of time too. The rusting proofing Inhibitors, the auto manufactures use today . Are way Superior then aftermarket product can be apply. The worst cars, I’ve owned, that rusted. We’re Mazda’s. A smart car really doesn’t need to be under coated. When you wash your car, power wash, the under carriage of the vehicle.
 
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