ls1121

So I installed the Bilstein HD on my 08 Z51, these were the first set of Bilstein shocks I ever bought. Everyone said how great they were so i thought "what the hell why not".

My thoughts are the ride is Greatly Improved over the Z51 shocks, a lot smoother. The day after I noticed a slight squeaking sound and it just continued to get worse until it was squeeking all the time. I ordered a set of OEM rubber bushings from GM and replaced the bushings in the rear shocks...the squeek is gone. The rubber bushings are crap, the Bump stop is a joke and the Boots are flimsy. I re-used the old bump stops,dust boots and New GM bushings and all is good. You would figure for the money the parts would be good but they are crap.

Does anyone know if anyone makes Poly bushings for the sway bars. I'm not really sure what size the bar is on my Z51 suspension.

BlackFya

I was able to get a set of left over Pfadt poly bushings from one vendors having a shelf clearing sale. They are out there but you have to hunt. I'm not sure if anyone else produces them. I don't have any feedback because I am currently overseas.

ls1121

I've looked everywhere I can but......... GM call for 23.2 mm rear bushing for the rear w/ Z51 suspension.
I found some bushings alone @ 22 mm.
found a 23mm w/bracket for the front of a C5, don't know if it will fit.

would like them with the grease fitting. No luck so far.

byte_me

sorry- re-read and saw you were looking for sway bar bushings, not poly shock bushings...

Gearhead Jim

Are you saying that the Bilstein HD shocks come with rubber bushings, bump stops, and boots? That are low quality.

I've had base model shocks on our Z51 for about 35k miles, initially they gave a big improvement in ride with only a small decrease in real world handling. But they are now getting too soft and I might replace them with the Bilstein HD. We had Bilstein Sports on our C5 and they seemed just about as stiff as the factory Z51 shocks that came on the car.

Gearhead Jim

BTW, I did a back to back comparison with another C6, same tires and same suspension, except he put the Koni FSD shocks in his car. We both agreed that the Konis felt just as stiff as the factory Z51, but your wallet gets a lot lighter.

Boomer111

My impression of the comparision between the Z51 stock suspension and my 1LT with Z51 sways and Koni FSD shockes is that the FSD rides smoother while exhibiting the same handling.

Just not as harsh as the stock Z setup.

This was my initial impression and I can not recall if I had the Non RF tire.

I have gone back and forth with rims and tire type to many times to recall.

I do know that going from RF to Non RF is very evident with improved ride.

Gearhead Jim

We just had Bilstein HDs installed on our 2009 Z51, and I test drove them for 100+ miles yesterday, just before the salt started falling and shut down the season.

This is our third Z51 Corvette (2001, 2006, now 2009), I like the handling but the ever-worsening roads of Illinois have become too annoying. There is one road in particular, 2 lanes/55 mph, that I can drive for 100 miles to the Mississippi. The potholes aren't bad but it has a frost heave/tar strip/mismatched expansion joint, about every 30 feet all the way. I'll do the math for you, that works out to 17,600 smacks on the front suspension and another 17,600 smacks on the rear suspension. Each way. In two hours. Ouch.

With the original Z51 shocks, the front smacks were annoying but tolerable. The rear suspension smacks were something else, each time it would feel like the suspension was welded in place and the only "give" was in the tires themselves. It felt like the tires would almost come off the ground with each hit. Putting Michelin PS2 runflats on the car helped, but not enough.

At about 35k miles, I had the Z51 shocks replaced with GM Base Model shocks. The ride improvement on broken pavement was moderate, the improvement over the frost heaves was dramatic. It actually felt like the suspension was moving! Handling stayed about the same in big sweepers, like you would expect. Turn-in and transitions, like in a slalom, were not as good but still acceptable. After all, it still had the Z51 springs and sways. I was happy.

Now we are at almost 80k miles and the base shocks had become too soft. A combination of age/miles, and my constant desire to attack corners, said it was time for a change. Since I had driven an identical car with the Koni FSDs and decided it was too rough for me on our roads, I had to find something else. We had Bilstein Sports on our 2001 and they felt just like the factory Z51 shocks, so I eliminated them. The best compromise seemed like the Bilstein HDs, a call to Bilstein got me the information that the HD's are only about 15% softer than the Sports. Hmmm...

Last week we got the Bilstein HDs from Tire Rack and I had the dealer put them on. Looking at ls1121's original post, I also ordered all new nuts & bolts from the dealer, everything from GM related to the shocks that looked like it would work with the Bilsteins. Picked the car up Friday, tested it yesterday.

My 100 mile test drive was on that same road toward the river, but I only went half way, just over 100 miles total. The road has not been resurfaced since my annoying drive with the Z51 shocks.

I'm very happy with the HDs. They are stiffer than the base shocks, but far more compliant than the Z51s. Riding over the frost heaves was noticeably firmer, but (to my mind and my butt) not harsh like the Z51 shocks. Of course, it will take more road trips and perhaps an autocross to make a final judgment, but so far I'm happy.

BTW, the factory Z51 shocks have a gas charge in them that partially supports the car, replacing them with the base shocks lowered our car by about 1/4" front and rear. I had measured the ride height , both at the fender lips and underneath with the GM tool several times both before and after the first change, so I'm confident in those numbers. We had the ride adjusted (1 turn of the bolts = about 1/8" at the fender lip after settling from 200 miles of driving), drove for a while to settle everything, and then an alignment.

It's been over 30k miles since my last measurements, but today the front of the car is exactly the same as last time but the rear raised up by 1/4" with the new shocks. I'll want to get some more miles and repeat the measurements before adjusting, and that may not happen until Spring.

Hope this helps...