What is it with KW?

They stop like garbage when bobtailing, and heavy loads. I had a T6, brand new, a T8, and drove my 2nd T8 a few days ago. Everyone of these trucks stopped terribly bobtailing, and the last T8 with 130k gross felt like it didn't want to stop then either. I normally drive a 4900SA Star Car, it stops good with or without a load, and bobtailing. I've bobtailed Centuries and Volvo's, and IHC's, all were better than any of the KW's.
I'm normally at 120k plus, 7-8 axle chip boxes. So it's not like the KW had any more load than my Star Car.
I don't care to set foot in another KW at this pointe.

 

The T6 was an '07, and both T8's were/are 06's. Both T8's were 18k front, 46k rears, 4:10/4:11. The T6 was a typical road tractor, nothing really heavy duty about it.
Now I'm totally ignorant here, I thought the brakes were standard regardless of the specs.
The one T8 I've pulled the same chip box as the Star Car with no issues.
Both the T8 and the Star Car have the same specs.The guy that normally drives the KW said he hadn't noticed what I'm talking about, but I think he's just used to it, it's the only truck he's driven for a few years.

 

I don't think any of the trucks had poor maintenance, especially the T6 and the T8 I just drove. The restriction device is a possibility. Hopefully tomorrow I'll get a chance to talk with one of our mechs. It just didn't instill a lot of confidence in the brakes. It had been a few years since I'd been in a KW.

 

Would that affect stopping even with a trailer?

 

So,,, judging buy the description, it sounds like none of the KW's I've had, had this?