Rob 02

I've seen an early post where someone mentioned C6 knuckles having a shorter steering arm.

If this is true I can see advantages to using them on the C5 in theory.

I would think that the shorter arm would provide better handling through a stiffer feel in the wheel, be more responsive and a possible tighter turning radius.

I will be changing my steering rack soon and was wondering if anyone has tried them. If so what were the results?

Thanks, Rob.

ChrisLSx

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JHrinsin

Not sure about the shorter steering arm, but I do know that C5 road course racers frequently swap to C6 knuckles because they are supposedly stronger/stiffer and less likely to have flexing issues when used under duress at the track due to extreme braking loads. Sort of like the C6 2-piston sliding front calipers are slightly better (less likely to spread) than the C5 units. I would have to believe that both the C6 front knuckle and the C6 front 2-piston sliding caliper were redesign due to the higher loading associated with the C6 Z51 13.4" front brakes.

bfit

I have a set of C6 and C5 in the shed Ill measure them tonight and post

Rob 02

The webbing is thicker in the brake area of the C6 knuckles. The C6 base and Z51 have the same caliper as the C5. The C6 Z51 caliper is mounted on a larger frame to accommodate a larger rotor. The C6 Z06 and ZR1 has the big calipers but still bolt up to the C5 knuckles.

I'm using C6 Z06 brakes but I can't really justify ordering and installing C6 knuckles for this purpose alone when street driving. If there was a benefit in in handling I would be more interested in them.

Rob 02

Thanks!

They are probably only a little different if at all. Maybe only 1/4 inch so it might be hard to measure.

93Polo

They will bolt on and I have a set on my '01. Steering arm is slightly shorter.

The C6 knuckle is stronger and from what I have read was developed because the engineers saw flex in the knuckle while developing the ZR1.

https://www.corvetteforum.com/forums...-geometry.html


The reason I swapped as I have a Stillen AP big brake kit and the car is tracked. If you have OEM brakes and not seeing track time, I would not do the swap.

https://www.corvetteforum.com/forums...-spindles.html

Rob 02

Thanks.

I'm installing C6 Z06 brakes tomorrow. I'm probably not going to be doing much serious tracking. Just spirited driving.

Have you noticed a difference in the steering with the arm being shorter?

93Polo

In my opinion it is not noticeable.

The early C6 Z06s ran the same spindle as the C5, I would not do the swap for your intended use. If you ever get stickier tires and aggressive pads, I would consider the upgrade. Honestly, some may consider me paranoid for doing the swap but I had a friend break the caliper mounting ears on his pro-touring muscle car that was on C5 spindles. However, I had rather spend a little extra on a car that I know has had track time practically since new under the prior 2 owners than have a failure at speed.

Rob 02

This is all good info.

Thanks again.

bfit

I measured the uprights I have and the only difference I can see is that the c6 z06 upright is heavier construction around the calliper mounting

Rob 02

That seems to be the consensus.
I thought that there might be a noticeable steering improvement in swapping them but that doesn't seem to be the case.
Oh well, one less part to change.

Asterios Anagnostou

Reviving an old thread here. Hey Rob, I just did this swap yesterday and it took me no more than three hours with the right tooling. If you're running the c6 Z06 brake system, why not just swap the knuckles out? I do spirited driving and canyon carving and sometimes hit the brakes pretty hard. The c5 knuckles weren't designed for that much stopping power and so they flex and, under the right conditions, break. So, with the c6 knuckles on there, that's one less thing for me to worry about. I know I have the right parts paired together, you know?

You can find them pretty cheap nowadays. There are some Corvette part out sites that sell the front pair for about $100. Maybe I'm paranoid, but I don't want there to be any question when it comes to braking if I'm going to be doing any more than mild street driving. Just my 2 cents.

Who knows, you may not even have the car anymore!

93Polo

The new knuckle was engineered when R&D on the C6 Zr1 discovered the spindle flex not the C6 Z06 which entered production with the same spindle as the c5.

Asterios Anagnostou

Err ok. Are you just saying it didn't depend on whether or not it was a Z06 because it was a product of testing on a zr1? I don't think I said that it did, rather only that the fatter knuckle should be used with the Z06 brake package. The upgraded knuckle became the knew campanion to those brakes which is why I said it would be pairing the correct parts together. Sorry if I misunderstood your comment.

93Polo

C6 Z06 brakes are fine with both knuckles as the Z06 brakes passed R&D with the same spindle as the C5.

The "C6" spindle was introduced in '09 after the 1st C6 Z06s. The C6 came out in '05 and the C6 Z06 in '06 with the same knuckles as the C5. It was a mid generation change after they discovered spindle flex when GM was testing for the ZR1 carbon brakes. ZR1 carbon brakes were an option on later Z06s. The Z06 brakes were 6 piston PBR calipers with iron rotors. ZR1s had larger calipers and carbon rotors.

Pumba verifies the change in post 13:
https://www.corvetteforum.com/forums...-spindles.html

If you are going to ZR1 carbon brakes or tracking the vehicle I do recommend the newer stronger spindle as failures have been documented under track conditions. Spindle failures have not been a problem with street driven Z06s.

JHrinsin

Yes the late C6 spindle/knuckles along with the SKF X-tracker front bearings, the Wilwood Aero6 front calipers and the Lambert Quantum brake cooling duct work are all way over the top, total over-kill on my mostly street driven car, which sees limited track time at HPDE type events. But being the **** retentive engineering type, I just could not resist the upgrades as well as the piece of mind knowing that I will still be able to drive the car home after the events, as long as I stay on the pavement and off the walls

Asterios Anagnostou

Case in point, just like you said, GM made a mid generation change after discovering through testing that the original implementation, with the c5 knuckle, was not sufficient. Based on these tests they decided ALL corvettes 09 and up should have the redesigned knuckle, which is why I'm saying he might as well change them out. I'm not really the "it's good enough" type. C6 brakes - up to date c6 knuckle. It takes very little time and is very cheap. If the time ever comes when the guy WANTS to track it, he won't have to worry about it because it's already done. In the meantime he can canyon carve or drive spiritedly without having that in the back of his mind.

Just a heads up, they're actually knuckles, not spindles.

This is good discourse guys. Thanks for adding to the discussion. ;D

93Polo

But...the old knuckle was sufficient for brakes other than the ZR1 carbon brakes. GM did not offer a recall or even a TSB to change. The fact that they changed the knuckles mid generation was due to economies of scale. It did not make financial sense to keep 2 knuckles not that it was an insufficient design for the other brakes.

If he doesn't see sustained track time there is nothing to keep in the back of his mind with C6 Z06 brakes.

gimp

If there's no sustained track time, the C6 Z06 brakes are only there for decoration, too. The weight penalty - rotating unsprung weight - is hopefully worth it.