: MRC v. 20" wheels

04-09-07, 09:45 PM
Another newbie question here. Any opinions as to the advantages/disadvantages of the 18 wheel Sport Package w/ MRC vs. the 20 wheel Sport Package (on the V8 model)? Anybody driven both? Any input welcomed.

Thanks in advance for your thoughts!

Steve Farley

04-09-07, 10:40 PM
from what i know about the cts the bigger the rim the more HP you lose.

04-09-07, 11:02 PM
You cannot order MRC and 20" wheels.


04-10-07, 06:20 AM
I realize that you cannot get the MRC w/ the 20" option. I was asking about the difference (plus/minus) between the 18" standard set-up w/ MRC compared to the 20" option w/o MRC.


04-10-07, 08:47 AM
20" = better looks, ok ride

18" without MRC = better ride

18" with MRC = unbelievable ride

05-05-07, 07:37 PM
Does anyone have MRC with aftermarket 20" wheels?

If so, does the MRC operate correctly (or acceptably) with 20" wheels?


05-06-07, 09:44 PM
I have a 07 V8 AWD with the facory 20's. Ride is OK, handling is great. I did drive a 06 with 18's and MRC - much better ride. I have reasearched this much because I just purchased my 07 with the full sport option - and my major hanging point was the lack of MRC. In the end I decided I liked the look of the full sport option - actually I love the look - and it was the over riding factor for me. As far as 20" wheels and MRC. I have done some homework on this - I would think MRC would work fine with 20" wheels - but I think the key would be to match the full wheel/tire weight for 18" with 20". The MRC "reads" shock travel and adjusts dampening and rebound accordingly. If the 20" wheel/tire is heavier - or moves the shock more (more shock movement possible with a stiffer/shorter sidewall) - then the MRC shock may misinterpret the "rough" signal and make the shock to soft. Also after detailed looking at my new warranty - and speaking with the dealer I bought this '07 from - installing 20" wheels may viod the factory warranty should a MRC shock fail. I checked the prices, dealer to customer cost for each of the front MRC struts are near $800 each. Assume the rears may be just as expensive because they also add a air supply to the rear shocks for load leveling. Not trying to influence any decisions - but this is the process I just went thru and learned before making my decision.

05-07-07, 07:41 AM
Thumper: Great analysis!

05-07-07, 11:52 AM

Thanks for your input!

05-07-07, 12:02 PM
I have aftermarket 20"s with MRC.

It was the best choice I ever made. The only thing I would suggest is MAKE SURE the centerhub is cut EXACTLY to spec. Don't screw with hubcentric rings or aftermarkets that don't exactly fit right. That will lead to massive vibrations and several trips back to the wheel center to get them adjusted. I thought about this many times, and I do have to admit, that the MRC might be over reacting to aftermarket 20's by bouncing excessively at highway speeds, but since I have never had properly cut rims, I couldn't make that correlation.

So if your into performance and cornering, go with the 20's. The difference in cornering is unbelievable. My srx vibrates at highway speed (Because they are not centered as good as they could be) but I would never put the stock 18's back on because the dip in cornering performance would be maddening

As far as the ride (over bumps) it is appreciable. Just stay on flat tar, most roads are of decent quality anyway.

They also told me that my 20's void my warranty, but not for MRC, but for premature transfer case wear. I told them I would see them in court due to the fact that the final selling point for me buying my car was "go ahead and get any rims you want, just sign on this dotted line"

05-08-07, 08:23 AM
Good point on hub centric rings. I have improved the ride slightly by reducing air pressure in the tires. They were running about 34 to 35 lbs each at cold. The door sticker for my factory 20's recommends 30lbs front, 32lbs rear at cold. I adjusted them to these values and they were much better. I also had a tire shop rebalance all 4 wheels, all were off significantly, assume they were off from the factory as the car only had 1013 miles on it when I picked it up. My opinion only, but I think Caddy should offer the MRC with 20's - heck the Corvettes have MRC with a adjustable setting - so why not do that for the SRX. I can live with the ride as it is though, now with the tire pressures at spec settings...