Ultra Fit USB 3.0: Excessive Heat


“did you mean they were not replaced with Ultra Fit? Any chance to share what is the repalcement model which works well?” - SanDisk Ultra USB3 64GB, I did not chose the model, but specifically stated that I do not want a microdrive anymore.

“would you mind to share what is the average write and read speed you can achieve with the replacement model?” - a quick test shown ~100MB/s sequential read and ~50MB/s sequential write. While not great, but it is fine - also the flash drive remains barely warm with a load that killed the UltraFit (copying to flash drive a VHDX disk image of size ~10GB).

I am happy now with the “quality for price” I got with these new drives.

 @chin … well one person doesn’t mean anything. As I’ve said from experience…using it for a year, moderate use. no problems.

@chin how did you measure the ultrafit temperature?

@electronicsguy: As mentioned earlier, the temperature was measured with Infrared Thermometer which has 1.5’C accuracy tolerance.

“well one person doesn’t mean anything.” This statement also includes yourself Electronicsguy. Obviously there are lots of people that have Ultra Fits that are not functioning properly. I don’t have a digital thermometer to measure mine but as I stated when writing or formatting I can only touch it for 2 sec so it must be at least around 70 deg. Also the write speeds fall below 23MB/s so this is not functioning properly and is defective. These all should be recalled if they are running above 45c. No wonder Sandisk drives are some of the cheapest drives on the market. The only flash cards & drives that I have ever had fail/problems with are Sandisk. Anything Lexar I have ever got have been flawless and I will to continue buy Lexar instead of Sandisk.

yes ofcourse it does. but if there was a design fault, it would have been recalled. people are only complaining because its get much hotter than bigger (normal sized) usb drives. speeds fall and vary even with normal usb drives. that’s not a fault by itself.

Yes because manufactures are ALWAYS forthcoming when it comes to product recalls no matter how much money it cost them :smileyvery-happy:. How about VW diesel cars of today? If manufactures can get away by ignoring the problem and hope a government agency doesn’t find them out they will.

Yes and the only people who write on forums are ones with a complaint. the others don’t write. Is there any specific problem you have with the ultrafit other than heat or varying speeds?

@electronicsguy: I believe it is not true that only people who write in forum are the ones with complaint. Many others out there may have similar problem but there are many reasons why they do not write in forum, such as:

  1. They feel their problem has been well represented by other posters, hence once there is solution from manufacturer, their faulty device will entitle for the solution too. Why post so many posts while they indeed the same subject?

  2. They may not aware of where to complaint about their problem.

  3. They would rather let go the $$$ rather than spend time to complaint.

  4. They may not aware of the risks of the excessive heat generated by the device.

  5. They may not aware of their rights as a customer, especially those in countries where customer rights protection is weak.


Write speeds do not exceed 23MB/s,:confounded: have tested using 2 different softwares. Any USB3.0 Lexar is capable of that. I’m just keeping this drive as a backup copy of my Lexar and keep on my keychain, that way I’m not really using it. In future I’ll stick to Lexar or Patriot flash drives.

@sweetsks wrote:

Write speeds do not exceed 23MB/s,:confounded: have tested using 2 different softwares. Any USB3.0 Lexar is capable of that. I’m just keeping this drive as a backup copy of my Lexar and keep on my keychain, that way I’m not really using it. In future I’ll stick to Lexar or Patriot flash drives.

I’m afraid your argument doesn’t hold water. Look at the specs from the manufacturers and compare apples to apples. Lets take the Lexar small profile USB 3.0 as you claim. This is the official page: lexar

You can clearly see: 

16GB in orange (up to 150MB/s read, 20MB/s write)
32GB in blue (up to 150MB/s read, 30MB/s write)
64GB in teal (up to 150MB/s read, 45MB/s write)

So what exactly are you complaining about when you’re getting 23M/s write speeds? (Also remember the 23MB/s you measured is real world speed and the speeds quoted above ar “ideal” speeds which are not necessarily achieved)

Now if you compare this speed to lets say the large profile lexar one (like jumpdrive p20) which has write speeds of 80MB/s or more, then it’s not a correct comparison since that one is a large profile (hence more heat loss, so can be run at higher speeds, more channels on board, etc). But I don’t see what exactly you’re tearing your hair about for a small profile USB drive with similar speeds as the competitor.

@electronicsguy: wouldn’t it be more suitable to compare with Lexar S45 (http://www.lexar.com/jumpdrives45?category=207)) instead of S73 which is of bigger profile?

ok. compare with that. similar speeds (all theoretical there, practical will be lower. in any case range is from 20-45 MB/s)

Can anyone verify for me if there is any potential for this drive to damage USB ports?

We purchased (6) 64 gb drives to transfer data from our inspection trucks to our office computer daily.  The amount of data varies from 500 mb to 20 gb daily per drive.  The data is mostly wmv, jpeg, pdf, and mdb files.

We noticed immediately the heat issue and weren’t initially concerned, because who really cares if it just gets hot.  However, we did become concerned when nearly every USB port these drives have been plugged into have failed.  

The computers are all relatively new, I7 @ 4.0 ghz, 16gb Ram, 64 bit Windows 7.

The USB ports have failed to the point that the computer doesn’t even recognize when something is plugged in, it dings, but nothing else happens.  

If I plug one of these Ultra Fits into a working USB port, a message appears telling me that this drive has issues and must be scanned (which always results in nothing).

Can anyone tell me what the hell is wrong with these things?  Do I need to throw them in the trash where they belong?  Or will Sandisk replace them with units that don’t suck?  

To be honest, I’m leaning towards trashing them, I have had more customers complain about the reports we deliver on Sandisk drives than any other brand…

Or will Sandisk replace them with units that don’t suck?  

That’s the plan.


@kjh I guess everyone’s experience is different. I can say that I’ve used the ultrafit on my laptop and raspberry pi (continuous use) without any problems. Yes it does get hot, but its within design specs. The USB ports should not have been damaged by this heat. Of course if you could prove that the heat is outside typical USB design specs, then you would have a case.

I don’t see why Sandisk has to replace them since they dont “suck” in the first place. They’re tiny so they’re hot, get over it.

So you admit that these things suck…  Why would I want a direct replacement?  This Removed  is going in the trash.  

Btw, I am surprised at the level of Removed  you Sandisk representatives have.  

Please take some time to read our forum rules and guidelines. Foul language and personal attacks will not be tolerated. This will be your one and only warning. If you continue with the insulting posts you will be banned from posting in this community. 

Forum Admin 


1.) No one replying in this thread is a SanDisk employee or representative; only users like (or maybe not) yourself.

2.) I can’t see where anyone replying has admitted that these drives are categorically defective.

3.) There really is no need for the vulgarity in your reply.

You guys have thousands of posts on a forum for flash drives and don’t actually work for Sandisk?  

@kjh… if you can’t speak in a civilized fashion, it’s best that you don’t. No-one here is a sandisk employee. And there is no fndamental problem with the drives. If you have an issue, write a letter to sandisk rather than ranting here about non-existant problems please. Let’s move on.

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