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MDS and aftermarket rims/tires

5K views 33 replies 10 participants last post by  Part Deux 
#1 ·
I just had a Kal Tire salesman tell me that changing to aftermarket rims and tires would interfere with my MDS to the point where I could be getting 30% to 40% worse fuel mileage. He said it happened to him on his Dodge Ram Hemi with MDS. Anyone ever hear of / experience this?

Now think about it, this guy should be the LAST guy you would expect to be dissuading me from buying rims and tires.

:banana:
 
#4 ·
awesome engineering feat.

Too bad the tire shop doesn't drug test, he's definitely been smoking something.
 
#11 ·
That is not enough of a difference to make much difference:

17's come with 215 x 65 x 17 tires that are 28" in diameter

18's usually have 235 x 55 tires, which are 28.2" in diameter.

20's usually have 245 x 45 x 20, which are 28.7" in diameter, but you can also use 255 x 40 x 20 which are 28.3" in diameter, as are 235 x 45 x 20.

The difference in weight of the rim isn't going to be drastically different either.

Where you will notice the difference is in the ride/handling.
Yep, the MDS won't even blink at that. It's just not that sensitive.
 
#10 ·
That is not enough of a difference to make much difference:

17's come with 215 x 65 x 17 tires that are 28" in diameter

18's usually have 235 x 55 tires, which are 28.2" in diameter.

20's usually have 245 x 45 x 20, which are 28.7" in diameter, but you can also use 255 x 40 x 20 which are 28.3" in diameter, as are 235 x 45 x 20.

The difference in weight of the rim isn't going to be drastically different either.

Where you will notice the difference is in the ride/handling.
 
#15 ·
I run 245/45/20's in the summer and 225/60/18's in winter. The summer rims, in addition to being bigger, are heavier. The only difference I've noticed was the gas mileage being slightly worse and the ride being a bit harsher. No difference in MDS performance on my 2010 5.7
 
#17 ·
This is very LOL - MDS gets you at best 10% improvement. But in either case, I used my Superchips programmer to change the tire size in the cars computer which was slightly off (like 5 mm) when I went to 20" wheels and tires. My MDS works perfect I can hear it engage when it is supposed to. It worked before I changed the tire size in the computer BTW I just wanted my speedo to be more accurate.
 
#26 ·
The system will not provide 20% improvement :) More like 5%

Nothing in all that blah blah blah sales crap indicates it's nothing more than a crude system that evaluated throttle position (and a few other conditions) and either shuts down cylinders with essentially 1980's technology (GM). The modern advantage is being able to use hydraulic oil pressure, which is a bit better in control.

Was I on the design team that designed the product, no... But I am familiar with how it operates.
 
#34 ·
Hell, it doesn't even play nice with a predator!

I did one 2-way run looking at the gas mileage difference. It was awhile ago, and think it was 1.25 mpg improvement with MDS. 1.25 over 21 mpg... is nothing. Wasn't worth the driveability issues nor the potential valve dropping problem.
 
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