So I just had my new (to me) Z51 shocks installed into my base C6. I did this knowing about all the complaints of the z51 shocks (bump steer, too stiff etc etc...). I had thoughts that the ride quality of these shocks got such a bad name because of the very high spring rate that the Z51 suspension has compared to the base springs.

In my opinion, I was right, the ride with base springs + Z51 shocks and sways is very good. Not too harsh, no bump steer, much less body roll (obviously).

So, in short, I got shocks for $95 + shipping instead of paying $300 for Bilsteins (which honestly is probably a very good solution for the real Z51 owners.) I am very satisfied with the upgrade, and I can safely recommend it.

Also, a special thanks to Rick & the Crew at Synergy Motorsports for taking care of the install...

 

If you don't mind me asking what it cost you getting them installed? I wanna get bilstein installed on Base C6
Thanks
Shalen

 

I got billed $350...Which is 3.5 hours of labor at normal Synergy rates...If my back wasn't so f**ked up these days I'd have no problem tackling that in my own home garage with a friend and a few beers

It sucks...I have a hard time just washing the car these days.

 

i just put the z51 sways on last night on my base suspension and i can definitely feel a difference, for 158 dollars this mod is a no brainer. next are the polyuerathane from pfadt.

 

I have a Z51, and it does seem/feel like the shocks and springs aren't matched that well. When ready (need to use the crap out of the shocks, similar to the runcraps), I will put some Bilstein sports on. In the meantime, I too, will try the Pfadt poly bushings, (a little wishful thinking or miracle doesn't hurt).

 

You mentioned "bump steer" several time. I thought bump steer was the relationship of the tie rods to the suspension angles?

 

I got the bushings and i can feel a difference, but maybe my lack of experience of what but i feel like the steering is a little more sensitive...

 

Hmm...to clarify...Bump steer is usually caused by caster issues. What I was describing (poorly) was when people complain about z51 shocks causing their car to be unsettled quite a bit when they hit bumps in the road, particularly through a high speed turn...

And as I said, I suspect the problem is linked to the springs more than the shocks on a Z51...

 

Take this for whatever it is worth. I am sure that many things factor into it.

Bump Steer
From Wikipedia, the free encyclopedia

Bump Steer is the term for the tendency of a wheel to steer as it moves upwards into jounce. It is typically measured in degrees per metre or degrees per foot.

On modern cars the front of the tire moves outwards, as the suspension is raised, a process known as the front wheels "toeing out". This gives roll understeer. The rear suspension is usually set up to minimise bump steer, where possible.

A typical value is two degrees per metre, or perhaps more, for the front wheels.

Excessive bump steer increases tire wear and makes the vehicle more difficult to handle on rough roads.

Solid axles generally have zero bump steer, but still have roll steer, in most cases. That is, if the wheels move upwards by the same amount, they tend not to steer.

Roll steer is an important part of the budget used to define a vehicle's understeer, known as a Bundorf analysis.


Difference between Bump Steer and Roll Steer

In a bump steer, both wheels rise together. In roll steer, one wheel rises as the other falls. Typically this produces more "toe in" on one wheel, and more "toe out" on the other, thus producing a steering effect. In a simple analysis you can just assume that the roll steer is the same as bump steer, but in practice things like the Sway bar geometry have an effect that modifies it.

Roll steer is usually measured in degrees of toe per degree of roll, but can also be measured in degrees of toe per metre of wheel travel.

Method of Adjustment

The linearity of the bump steer curve is important. If it is not straight then the length of the tie rod needs to be adjusted.

Bump steer can be made more toe out in jounce by lifting the rack or dropping the outer tie rod, if the rack is in front of the axle. The reverse applies if the rack is behind the axle. Usually only small adjustments (say 3mm) are required.

Reference

"Tires, Suspension and Handling" by John C Dixon

 

One hundred bucks an hour for labor? Man, they are more expensive than MB dealers.

 

I've never seen a half decent performance shop charge less than $80/hr, and also, they need to make their money, I mean, I didn't even buy the parts through them so they made no money from that. Plus, Rick is a cool dude, and I don't mind paying a little extra to go to a place I like.

 

I replaced the Z51's with Bilsteins and at first it was harder but then it became controlled. Honestly I agree with you and the Z51 shocks were pretty good to begin with. It wasnt nec for me to replace them. My original reason for changing them was that I heard it was a partial fix for the wheel hop issue and that turned out to be true. I guess the combo of spring rate and z51 shocks was contributing some to the wheel hop which is all but gone now. I rarely see it now.

Do you have wheel hop with the Z51 shocks and the base springs?