We finally got our Cornerstone and hit the road for our first trip. The drive was impressive and it's easily the biggest sports car I've ever driven.
Our last coach was a tag axle Allegro Bus on a Spartan MMGT chassis with 400 HP ISL at 1200 ft-lbs of torque. Compared to a 44' Anthem at 450 HP and 1250 ft-lbs, but with a bit more weight, the engine performance was virtually identically, although the Entegra modified chassis easily outclasses the basic Spartan chassis that Tiffin used. But the Spartan K3 with that big 600 HP ISX and 1,950 ft-lbs of torque steps it up into a whole new world. Our 400HP Bus took us everywhere so there's really no issues with the 450HP ISL being underpowered in a 44' coach. It will get you there just fine. But the 600 really does make it a more enjoyable drive.
The engine isn't really broken in yet do the fuel economy hasn't fully reached its potential but at present I find the fuel economy of the big 15 liter ISX to be equal to what I was getting with our 400HP ISL. The ISL also drops off substantially as the speed increases but the larger 600 doesn't seem to do that as much. Cruising in traffic at 75 MPH was effortless and the engine just lopes along without breaking a sweat. So there appears to be no fuel penalty for having the larger engine. In fact, at higher speeds it appears to be just the opposite, although more seat time will bear that out. We plan on running the wheels off this coach this year so we'll find that out soon enough.
Power-wise it was great to climb major grades without dropping off speed. It was always annoying in the past to pass a slower vehicle only to come to a grade where your speed would drop off and they would pass you and you would have to pass them all over again on the next downgrade. With the 600 that doesn't happen and you can stay with the traffic flow, making for a less stressful drive. Trying to merge into fast and heavy traffic when climbing an on-ramp or when leaving a rest area is also much nicer with the 600 because you can get up to speed much faster and merge safely with traffic without becoming a slow moving chicane for traffic to navigate around.
The first thing that most potential buyers think about when considering the chassis is the larger engine. But the K3 is so much more than that. Braking is another step up. Generally front axles use disc brakes while the drive and tag are drum brakes. But the Cornerstone has 6 wheel disc brakes. Combine that with the 3 speed Jake brake and if you ever did have to nail them in a panic stop it would probably be like an F-14 grabbing the arrestor cable on the USS Nimitz. But the biggest thing I've found is that they don't fade like drums. When in stop and go traffic and when crawling along through an accident where the interstate is backed up for a few miles you are constantly using the brakes. With drums they heat up and you find yourself using more pedal pressure as they fade so you wind up trying to save them as much as possible. The discs just keep on holding. I don't think I've ever has to use more than 25% pedal pressure ever to stop the coach and this remains consistent throughout the run. I can't wait to try them in the Bighorn mountains and around Yellowstone this fall.
The chassis itself is another step. Part of this is the way the K3 is built, part of this is the additional tweaks that Entegra does to the chassis and part of it is those big wide 365 tires up front. The thing just goes wherever you point it. The steering isn't heavy by any means but imparts an excellent feel of the road through the wheel. I prefer this to Comfort Drive any day. It's responsive without lag or delay and the coach just seems to stay where you put it. If you have to go through construction zones where lanes shift you sometimes find yourself straddling or driving on pavement changes. The joint where two slabs meet can shove you to either side but the K3 doesn't really care about that and it can ride the lines or wherever. I attribute that to the suspension but mostly to those wide 365 front tires. Entering cloverleaf off-ramp the coach doesn't lean like others I've driven. The X bracing that Entegra adds to the K3 helps to keep it upright and lets the suspension do the work. Then again, I've seen this in the Anthem as well so that's not a Cornerstone exclusive. Wind push and 18 wheeler bow wakes are always lessened with a tag axle coach but with the Cornerstone I can't even tell they are there. It's pretty much impervious to wind so if you want to know if it's windy you'll need to look for some flags flying someplace. The coach is so solid and imparts a feeling of security and safety like I haven't yet seen.
Beyond the chassis, the cockpit area also affects the drive. Entegra's huge windshield allows the mirrors to be mounted much lower. This allows the driver to see over the top of the mirrors, eliminating any blind spots at intersections typical to other coaches where mirrors are mounted higher up. The lower mirror location also allows you to see your rear tires as well as far back down the road. Higher mirrors don't give you that angle so you have to compromise and split between those two views. The cockpit seating is super comfortable (new Flexsteel chairs this year) and after a 600 mile drive day I'm not sore in the least.
All in all we are both quite impressed with the way this coach drives, rides and handles and are looking forward to more seat time.
Linear Mode
