[sokoloff]

Noticed the rear tires on the coupe were getting low on tread. So today I checked them. Both rears were in the 2 to 3 / 32nds range with more wear on the outside. Fronts still have in the 5 to 6 / 32nds and seem to be wearing relatively evenly. Got the original Kumhos on the car. Running at 36 psi on the rears.

I've seen other posts where tires needed to be replaced pretty quickly. Appreciate any input on your experiences and will welcome recommendations on what to put on next. Don't have to worry about snow around here, so an all season will definitely work or maybe even a summer tire might work.

Have the original staggered tires on the car and really have no intention or desire to changing to the same tires on all four wheels.

Len
2014 EV Coupe 15,000 miles
2014 EV Cabriolet 4,500 miles

 

[OliverB]

Wow, that’s very early for replacement! I don’t have experience with Khumo tires but have seen some negative comments concerning them on the fourm. Both my smarts have had Continental tires. I have been reasonably satisfied with them. Had 30K on the set on my 451 when I turned it in at lease end. They would have needed replacement in a few thousand miles. My 453 now has 20K on the Continentals and they appear to be wearing at approx the same rate as those on my 451. Unfortunately I don’t think there are a lot of options for 451 stock sizes.

 

[Yinzer]

My Kumho tires on my ED likewise wore out at 16K. The fronts wore a little better. Anticipating turning the car in at end of lease (I ended up getting a reasonable offer and buying it), I bought some very cheap replacement tires - Indonesian Achilles ATR- K Economist. They seem to be wearing better - although it is hard to tell since I swap them seasonally with Continental winter tires.

 

[InjuredAgain]

7775 miles on our ED and rear outside shoulders are at 5-6/32's, with the center and inner shoulders both at 7/32's.

Front tire outside shoulder is at 7/32's, and center and inner shoulder area are at 8-9/32's. Needs more negative camber both front and rear though I have no idea what dynamic loading does to the suspension geometry. Looks like our rear tires will be done by 15k.

Tire pressures I use are 32.5F, 34.5R. We often drive it pretty sedately, but when I drive it fast, it's mostly cornering where I am stressing the tires.

 

[sokoloff]

For the more mainline manufacturers, the choices are limited to Kumho, Continental and Vredestein. I'll probably rule out the Kumhos. Have heard good reports about Vredestein on other German cars, but not necessarily on Smarts. Oliver sounds like he's had good luck with Continentals. That may be the way I go.

Len
2014 EV Coupe 15,000 miles
2014 EV Cabriolet 4,500 miles

 

[MB DNA]

Unfortunately seems that the "launch" torque combined with the regeneration (brake) drag on the rear wheels may be impacting tire life? Regeneration may also take some braking pressure off of the front tires?

 

[ElementalDragon]

Well... that could also have to do with the fact that you're not accelerating with the front tires, and there's less weight on the front tires as well. I've got nearly 50k on my 453, and i'd probably have still been using the same pair of front tires if i hadn't gotten a nail stuck in one of them about 5,000 miles or so ago.

 

[Yinzer]

I put 33 psi in the front, and 40 psi in the rear. Yeah, ride quality suffers a bit, but presumably rolling friction is lower. Tire wear seems to be better too. The door-pillar recommended pressure for the front tires is definitely too low.

And yeah, the exaggerated rear tire wear is probably due to the regen. Recall that rear-tire braking is very inefficient as I learned once having to limp an old car with failed brakes home with the "emergency brake" only as they called it back in those days (in the obstinate ol' USA, always a ratcheting pedal on the far left - not a hand lever). So, I suspect that even the Smarts relatively mild regen puts a lot of extra wear on the rear tires.

If this is the case, the by driving more aggressively so the service brakes on the front wheels are used more, you might actually get better tire wear!

 

[Yinzer]

For the more mainline manufacturers, the choices are limited to Kumho, Continental and Vredestein. I'll probably rule out the Kumhos. Have heard good reports about Vredestein on other German cars, but not necessarily on Smarts. Oliver sounds like he's had good luck with Continentals. That may be the way I go.

A good number of cheap budget brands also have sizes for the Smart 451 - sold here (16 different rear tires shown - front size also available):

https://simpletire.com/catalog?year=2015&make=Smart&model=Fortwo&option=Electric Drive&zip=15224

For the kind of driving most people do with their ED's budget tires might be fine. Remember that they all have to meet the same DOT requirements and be graded for traction, temperature and wear like any other tires.

 

[InjuredAgain]

I put 33 psi in the front, and 40 psi in the rear. Yeah, ride quality suffers a bit, but presumably rolling friction is lower. Tire wear seems to be better too. The door-pillar recommended pressure for the front tires is definitely too low.

And yeah, the exaggerated rear tire wear is probably due to the regen. Recall that rear-tire braking is very inefficient as I learned once having to limp an old car with failed brakes home with the "emergency brake" only as they called it back in those days (in the obstinate ol' USA, always a ratcheting pedal on the far left - not a hand lever). So, I suspect that even the Smarts relatively mild regen puts a lot of extra wear on the rear tires.

If this is the case, the by driving more aggressively so the service brakes on the front wheels are used more, you might actually get better tire wear!

The regen probably contributes to the wear to some degree but I would guess the suspension also contributes as well. I say that because I've worn out a set of tires in a long three-day track weekend in my Corvette, which has a similar tire stagger (245 front, 285 rear) and as I posted earlier, can engine brake at between two to three times the deceleration that the smart can generate. It also puts down 400 hp at the rear wheels so wear under acceleration is much greater as well, but both fronts and rears wore out at the same rate, and the rears started out with only 8/32's where as the fronts started out with 9/32's.

From what I understand, a deDion rigidly holds both rear wheels in plane so there should be minimal, if any, dynamic toe changes during braking or acceleration. And also due to the rigid axle, camber changes are only created when the wheels move through their travel independent of the other.

Even on a sports oriented vehicle like a Corvette, the bushings are compliant enough that there are significant dynamic toe changes. Running zero toe in the rear on a Corvette will really wear the inside shoulders on a non-track driven vehicle, indicative of a lot of dynamic toe-out under acceleration. On a track driven vehicle, zero toe in the rear results in more even wear as the toe-in during heavy braking seems to wear down the center and outside shoulders.

There's a lot I don't understand about how these changes affect tire wear, and a lot I don't understand about how a deDion works, but the tire wear seems like more than just from the regen.

 

[OliverB]

My concern about some of the off-brand tires is that, while they meet minimum standards, handling and wet weather traction may suffer from poor tread compound and design. Years ago I experienced this and vowed never again to go cheap or off-brand on tires. Even some of the expensive brands aren’t always the best. When I need a set of tires on a vehicle I’ve never before bought tires for, I do a good bit of research and endlessly read user reviews for a good bit of time in advance. Also, I won’t ever buy directional tires again. Only did so once. No way to reverse rotation to smooth out feathering of tread blocks. Couldn’t use them on a smart anyway.

 

[MB DNA]

14,027 miles on OEM KUHMO Solus (rear) MY15 ED.

 

[sokoloff]

Here's something I just thought of. I've never owned a car before with the tire pressure monitoring system (TPMS). If I had my choice, I'd pick one without it, but that's a topic for another time.

When I buy my two new tires and have them installed, do I need to buy anything regarding the TPMS or change the battery, reset anything, etc.? Can the old one be reused or is it integral to the new valve stem? Are they all interchangeable?

Thanks.

Len
2014 EV Coupe 15,000 miles
2014 EV Cabriolet 4,500 miles

 

[MB DNA]

When I buy my two new tires and have them installed, do I need to buy anything regarding the TPMS or change the battery, reset anything, etc.? Can the old one be reused or is it integral to the new valve stem? Are they all interchangeable?

As your stem/sensors (all one unit) are relatively new, you should have no problem. When the batteries do fail, Nanny State says you have no choice but to replace unless you mount the tires yourself or go to a friendly tire store.

The batteries typically last 7ish years at which point $250 (installed) will get you a new set.

 

[OliverB]

The stem and sensors on my 453 are two piece. Found that out when I couldn’t remove caps after they had seized. Replacement stems were the same as Chrysler uses. Batteries in our 2004 Mazda RX 8 are still going strong.

 

[sokoloff]

Just checked the EPC and the Smart pressure sensor units are the same as some/all Mercedes, so you can get them from a Mercedes dealer if you so choose. By the looks of the drawing, the sensor is part #000 905 72 00 and has wholesale price of $56.25. The tire valve looks to be three pieces including the cap and is part #000 400 10 00 with a wholesale price of $34.50. The tire valve kit at my online parts place by the OEM manufacturer is $5.97. The sensor unit is about the same as Mercedes charges.

Len
2014 EV Coupe 15,000 miles
2014 EV Cabriolet 4,500 miles

 

[MB DNA]

When I buy my two new tires and have them installed, do I need to buy anything regarding the TPMS or change the battery, reset anything, etc.?

The tire valve looks to be three pieces including the cap and is part...

My response was driven by the picture you painted of "having them installed" not a DIY effort?

A "national chain" tire shop may offer to sell you a new rubber washer kit but most will not "rebuild" as they prefer to replace the complete unit. Unless you have experienced false reads, yours shouldn't require any attention?

 

[OliverB]

I used a local shop I’ve known for more than 10hears for the stem replacement. They do them all the time and the price was only $40+ for parts and labor for all 4 tires. You can get the sensor portion for a better price than dealerships charge but be certain to match frequency.

 

[sokoloff]

Thanks for the replies guys. I have always replaced my valve stems when I got new tires in the past, but this is the first time doing new tires on a car with TPMS. So the suggestion with the Smart is to just remove the tires and leave the sensor/valve stem in place and reuse it. Sounds like a plan. Thanks for the education.

Len
2014 EV Coupe 15,000 miles
2014 EV Cabriolet 4,500 miles

 

[Blackbelt]

Although the regen braking may cause the rears to wear, the rears on my ICE smart didn't last either. Our first one, a 2008, had the Continentals and they were junk by 17K. My leased 2012 had Kumho's and they were junk by 16K miles. Our 2013 Iceshine had kumhos and they were also shot by 16K miles. I put a set of Westlake RP18's and they lasted about the same. I did get almost 30K out of the fronts though. I replaced all 4 with the Achillies ATR-K economist and they seem to be holding up pretty well.
Another option is running 195/50/15's on the ear. Amazon has Hankook Ventus V2 in 195/50/15 currently for $44.48/ea with free shipping.