I have a 2015 C7 with the ZR-1 package (Z51 wheels, tires, and spoiler) and to tighten the car's handling a bit I'm considering adding the Z51 rear sway bar while retaining the non-Z51 front bar. My reasoning is that my car will not ever see the track as long as I own it, but I would like to sharpen the car's handling some while harming the ride as little as possible.

The non-Z51 front bar is 26.2mm while the Z51 is 28.0mm, and although many claim the Z51 is solid while the non-Z51 is hollow, they are probably both hollow since the difference in weight is only ~2 oz. This doesn't sound like much, but does it translate into more torsional stiffness than it seems? If not, the behavior should be very similar. On the same token, perhaps the difference in ride would be minimal as well.

C7 development engineer Jim Mero has stated that the chassis has been tuned for a "tiny amount of understeer," as is the case for most (all?) production cars since it's an inherently safer attitude for most drivers, and that all Z51 road tests I've read state that this is the case with power oversteer readily available. The question is will adding a rear Z51 bar to a car with a non-Z51 front bar bring the car's behavior closer to neutral without any adverse side effects?

IOW, we know it should increase the oversteer and decrease the understeer thresholds, but will this likely push the car into near-neutral territory or push it over that line into potentially dangerous oversteer?

Some are doing this and I haven't read a negative report yet, although I must wonder how many are pushing the cars enough to really know what their cars do at the limit. If the car understeers slightly in stock Z51 form when power is not applied, will adding only the rear bar be a win-win proposition--pushing the car toward an even more neutral attitude while marginally improving ride over a car with both Z51 bars?

Does anyone have any input other than anecdotal suggestions that "the factory engineers know what they're doing, so don't mess with that"?

 

Yeah, I have a Z51 couple without magride. Out of the box it understeered a little so I installed the bigger 31mm rear bar and now the handling is about neutral. I think the 26mm bar might be just right and the 31mm maybe a little too much with the stock front bar.

 

Thanks for the input. That's the kind of practical info I'm looking for.

 

Have you considered the aftermarket adjustable bars that are out there?

https://www.corvetteforum.com/forums...izer-bars.html

 

I personally do not recommend the Hotchkis bars. I tried them and went back to stock (Z51 w/MRC). The bushings are so stiff they're nearly a hard plastic and with that came noise (creaks/groans/squeaks) even when using copious amounts of grease.

Here's the thread I started on them though:
https://www.corvetteforum.com/forums...oxing-day.html

 

I hadn't considered them because their minimum setting for the rear is 5% greater than the stock Z51 bars. I doubt if I would want to go stiffer on the rear while retaining the stock non-Z51 front bar. Are any available that would go -5%, 0, and +5%, or thereabouts?

 

Stock bars are cheap, around $100. I think I would get the 26 and see how it feels. If you want more go with the 31.

 

I ran the base stock front bar with the non-mag Z51 rear bar for a while. Still had too much understeer. Then, I tried the Z51 mag front and rear bar combo (28mm F & 31mm rear). I liked it much more than the previous setups but, I still did not care for the front end dipping too much at turn-in. Finally, went with the aFe adjustable bars and I'm pretty happy with the handling. You can run the non-mag rear bar with the stock front bar, no problem. I just think that for as little the stock bars cost, you should go with the mag-setup. Much more neutral handling than the non-mag with still enough understeer for public road safety.

 

Have base car with mag ride. Also want to install z51 bar in rear. Is there a difference between mag ride rear bar and non mag rear bar. I have a set of non mag z51 bars and would like to use them..Mike

 

Yes, magride is 31 and non-magride is 26. Brackets are the same, bushing different.

 

I didn't know that, and it doesn't make much sense to me. Why the larger rear bar for the rear only on mag cars? I wonder what 2016 non-Z51 cars with mag ride have. I have a friend with one of those and I just emailed him for info.

If a mag setup (28mm front, 31mm rear) is safe, I would think a 26.2mm front and 28mm rear would also be stable in all conditions.

This is some really good info you guys are providing here. Thanks for all the input so far.

 

How would you describe the difference between the stock non-Z51 setup (no rear bar) and adding only the non-mag Z51 rear bar? Ride? You implied it understeered less, so I assume you noticed no unnerving behavior at the limit.

 

The stock (no rear bar) setup; I can only describe it as "sloppy". Far too much understeer and the front was also too soft, taking away that "sharpness" from the turn-in. It is Ok for people who do not place much value on sharp handling on winding roads. Provides the best possible ride qualities but, not by a significant degree.

When I added the non-mag rear bar to my stock base front bar, it produced absolutely no negative effects. The car felt better balanced and the ride was not noticeably effected. However, the rear bar was still not for the ultimate handling, still pushing (understeering) in the corners. It was still heavily biased to forgive inexperienced drivers who might make mistakes during cornering. I remember liking the change initially, compared to the no-rear-bar setup but, after a while I still wanted better. Adding the mag-bar setup improves handling much more significantly than just adding a non-mag rear bar.

For ultimate handling, however, the front bar also needs to be much larger, as well, than any of the Z51 combinations. No accident that GM came out with the T1 swaybars for track usage where the front bar is 40 percent stiffer than the Z51 front bars. That provides that precision at the turn in and during cornering that racers are demanding and performance drivers want. At the end I went with the aFe bar set mainly because it is double adjustable at the front and triple adjustable at the rear. That allows me to custom tune my handling.

 

Thanks, axr6, for that review. I fit somewhere between you and "people who do not place much value on sharp handling," closer to you I hope. I'm not looking for ultimate handling at the expense of ride quality, but just want to sharpen the base-car's existing demeanor in corners without going to extremes.

Based on all I've heard here in these responses, which is much more than I expected to receive, I'm comfortable adding the non-mag Z51 rear bar, as I think that will do it for me. I've had some experience tuning sway bars in the past and know how an overzealous application can cause serious side effects, although in this case it just didn't seem to be much of a risk. It was experience from others that I wanted to hear about, and that's what I got. Thanks again to all who replied.

 

My 15 zf1 handled great from the get go. Added z51 bars but did not notice much but when going over uneven bumps. I added z51 rear shocks do to the ride seemed to soft in the rear. The shocks was better for me. The problem with the front my be the soft rubber bushings. The z51 rear bushings fit tight on a none z51 bar
Z51 bushings are hard rubber or poly.

 

As a follow-up, I added the 26mm non-MRC Z51 rear bar about three months ago and find the mod to be a success. I haven't noticed any oversteer behavior and ride is about the same except for a slight tossy sensation on uneven surfaces, particularly in corners. That would be expected understanding how sway bars work. This would not be a racing solution, but it did snappen the handling moderately at a low cost (<$200 incl. all parts and shipping), so I'll give this mod a thumbs-up for my needs and expectations.