Stopping Distance and Grip With 18- and 19-inch Tires - 2017 Tesla Model 3 Long-Term Road Test

Comments

• morrisg2 Member Posts: 12

  May 2018

  Interesting tidbit about tire pressures: I have a Model 3 with a VIN in the 14xxx range (built in early April) and also ordered the 18 inch wheels with Michelin tires. My tire placard on the driver's door frame lists an inflation pressure of 42 psi, not 45 psi like Edmunds early production Model 3. I have heard rumors that Tesla made changes to the suspension tuning (spring rates and/or shock damping?) and implemented them on the assembly line in late March to early April. I think these changes were made to address the complaints about ride harshness in the early Model 3 production, but don't know for sure. Would the Edmunds editors care to try the 42 psi inflation pressure and report on it's effect on ride and NVH? After all, it's the same tire and wheel combo so there's no safety issue.

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• s197gt Member Posts: 486

  May 2018 edited May 2018

  tirerack.com compared the MXM4 to the Continential ProContact (non-RX) back in 2010. The MXM4 was recently introduced at the time according to tirerack.com, however the Conti still edged it out on the track/dry performance measure. (although the MXM4 had a better 50-0 stopping distance by a 10th of a foot.)
  
  Hard to find any info on the RX version of the ProContact but presumably it is an even newer version, hopefully enhanced performance. Tread design appears slightly more aggressive.
  
  I would also suggest another option: that one doesn't necessarily need to "upgrade" to a 19" diameter tire/wheel. Save the $1500 from the 19" wheel/tire package and just upgrade to a better 18" tire.

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• longtimelurker Member Posts: 455

  May 2018

  Those MXM4s are older than dirt by now...they were a really good tire back in the day, but...time marches on.
  
  Also, I very much doubt that a change to 42 psi from 45 psi is going to make any remarkable difference in any performance parameter for those tires. I think the idea of just going with 18" Contis is a better idea that will return most of the performance increases noted here in the 19" size.
  
  The super-hard rim-protector tires are a bad idea...if I end up spending $500 more for tires every five years for my two cars, due to using more fuel, higher initial price and more frequent replacement, because I buy higher-performing tires, I can live with that. The increase in grip here from .85g to .93g definitely has the potential to transform a crash into a near miss...that's a huge increase, especially considering these was no change in contact patch size.
  
  The Model 3 has a sophisticated suspension design and these Teslas carry their weight quite evenly distributed F/R and very low. The fact of this .9g+-capable chassis transformed into a .85g performer suggests to me how bad these tires are and how much of an afterthought they are - agree that the Conti was the development tire and the MXM4 was tossed on later.

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• throwback Member Posts: 445

  May 2018

  I would love to see a comparison of the handling with the 18s sporting summer rubber. My guess is the car will handle even better on the summer 18s. My experience (driving for over 40 years) is that all season tires are generally not very good if performance driving is your priority. If I owned a Model 3 I would gladly sacrifice range for better turn in, braking, and overall grip.

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• morrisg2 Member Posts: 12

  May 2018

  Well, latest info on the suspension is that Tesla did an update in December production to address ride harshness which is available at Tesla Service Centers for update. However, recommendation is to try 39 psi in place of the 45 psi pressures for more comfort. That reduces the range somewhat but that's the tradeoff between range and comfort.
  
  My April production Model 3 is just fine at 42 psi with the new suspension components and the 18" Michelin MXM4 TO tires. A nice blend of traction and range for my tastes.

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• actualsize Member Posts: 451

  June 2018

  morrisg2 said:

  Well, latest info on the suspension is that Tesla did an update in December production to address ride harshness which is available at Tesla Service Centers for update. However, recommendation is to try 39 psi in place of the 45 psi pressures for more comfort. That reduces the range somewhat but that's the tradeoff between range and comfort.

  As an engineer that tuned suspensions for a living, applying a simple tire pressure drop to an entire tuned system is a band-aid, at best. Suspension tuning involves a lot of careful coordination between spring selection, bushing specifications, stabilizer bar diameters, shock absorber valving and the internal construction of the tire itself (many tuning knobs there), all of which are iterated numerous times in the development process to produce the target ride and handling profile. Simply lopping off a few psi will take the edge off, but it is an incomplente solution that can never be effective in all cases and doesn't fix the underlying problem. But I know why they might want people to try that first. The full retune option represents actual hardward changes (springs & shocks, probably), which is a big warranty cost they'd have to eat. Compared to other carmakers I've worked for, they lose enough money to liberal parts-swapping as it is.
  
  The other problem with dropping your tire pressure is an increase in temperature-related TPMS alarms. Cars like ours that are placarded at 45 psi are set to trigger a low tire warning at 34 psi (75% of recommended pressure is the rule). Running them at 39 psi gives you a much thinner margin, so you'll need to check your tire pressures more often, especially if the area you live in has large day/night temperature swings. 5 psi can come and go with a passing weather front or a cold snap. Unlike some european competitors, the Model 3 has no "comfort pressure" setting in the menus that would reconfigure the TPMS trigger point to match - if in fact the tire's structural capacity could tolerate such a thing, which isn't a given.
  
  I think we may bring ours in for the suspension upgrade. We've already tried the lower pressure a little, and the car feels sloppier in some ways. Again, a simple tire pressure drop changes more than the tire's ability to absorb sharp-edged impacts. And there's more wrong with the Model 3's ride than just that.
  
  

  Twitter: @Edmunds_Test

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