KW HLS Hydraulic Lift System

[Apexspeedtech]

Hello all!

I'm working on a GTM build, and would like to add the KW Suspension HLS Hydraulic Lift System to add ground clearance for curbs, speed bumps, etc. I've used it successfully in the past on Porsche builds and am very happy with its performance.

I've found some threads around the internet talking about different dampers for FFR GTM's, but its still unclear if I can just order their KW HLS C5/C6 kit? Should I specify a different spring rate or does anyone think the valving will be an issue?

https://www.kwsuspensions.com/products/kw-suspensions/hls-hydraulic-lift-system/kw-suspensions-kw-hls-chevrolet-corvette-c5-c6-19261415.html

Thanks,
Neel

[crash]

I do not believe shaft lengths are the same as the C5/C6 and also have a look at the rear suspension. The shocks for the C5/C6 are "not standard configuration" with the "hoop" on the end of the shock. The GTM uses a "regular" shock end. Regular C5/C6 shocks are not going to work, especially in the rear.

[Apexspeedtech]

I do not believe shaft lengths are the same as the C5/C6 and also have a look at the rear suspension. The shocks for the C5/C6 are "not standard configuration" with the "hoop" on the end of the shock. The GTM uses a "regular" shock end. Regular C5/C6 shocks are not going to work, especially in the rear.

Thanks for the quick reply! Can anyone help with drawings, part numbers, specs or anything that can help me spec out the proper KW Dampers for this? Unfortunately the car is on the opposite coast of where I am right now, so I can't just grab the ones off the car and measure them.

Thanks,
Neel

[RR46]

Ring bolts each end both front and rear.
Appr shock length ear to ear when resting needs to be in the 14-15" ballpark depending on your desired ride height. Wheel diameter will obviously have an impact.
Stroke should be calculated around the resting length so you have droop and compression available. It's generally recommended in the automotive world to have 2/3 droop and 1/3 compression for road driving. I think many cars don't hit exactly that and do well anyway, but consider your overall wheel travel needs to keep all four on the ground in a canyon for example. Consider if you will have bump stops that limit compression. If you want airlift that works, you need to have enough droop for the lift to complete before the piston is fully extended.

Watch out for diameters of the springs and the lift system:
- Front upper A arm turns into a pinch point when at full droop/lift system fully raised. 60mm ID springs from Swift worked on my GTM (not sure on OD). 65mm ID springs got pinched by the upper A arm in full droop. Aircup sits on the bottom.

- Rear outer CV joint/boot is a limiting point for spring/shock diam rear. 60mm ID ok there too. 65mm ID springs rubbed. Aircup sits at the top.

Do make sure the kit you want to buy supports mounting "upside down" at will, to clear those limiting factors. Be especially aware if ordering a shock where the canister sits on the side and not a remove reservoir (or no reservoir).

[Apexspeedtech]

Thanks. I'll be using the KW HLS system, which I've used on a Porsche 997 application before and works well. They share very little about fitment and custom options on their website, so I'll have to chat with a dealer and give them some specs. The good news is their reservoirs can be remote mounted, and I've worked on plenty of race cars (mostly GT3 Cup cars) with KW applications, but don't have any experience working with their street components or spacing custom applications.

https://www.kwsuspensions.com/products/hydraulic_lift_system#hls-kit

As a point of comparision, do you have a cross-reference with a stock application that hits all the points you brought up in your post? I've been told, for example, that C6 Corvette shocks won't work. Or, do you have a drawing for a damper that does work - for example is there a drawing for the KONIs that come with the car?

Cheers,
Neel

[Erik W. Treves]

have you considered RLP-1.25" Front Kit $1,868.00 Price and there is even a rear kit that is half the price of the KW system? - I used just the front kit with success.

[RR46]

You could make a basic drawing with the eye to eye distance at resting, and max diameter. The Swift springs outer diameter measures slightly less than ~3.25". Clears front upper A-arm, rear CV boot. If your shock choice has a "long leg" and short body/spring then you could get away with bigger diameters but why risk it.

As others have mentioned the shocks for the GTM aren't the same as C5/C6. The GTM shocks mount with eyes top and bottom. Spring rates would be wrong and shock valving would only be good with some luck if the adjustment range was great enough. You do need to start from scratch and spec a shock.

KW supports a lot of custom programs and should definitely be able to make a set of shocks to spec. Give them vehicle weight, axle weights, motion ratios and intended spring rates and intended use case for the car, they'll come up with a great spec. For track spring rates, I would consider 65/115 N/mm to be the softest you should go to, that's if you install swaybars and wing. Those rates have been successfully developed by Wilbers, I found them very balanced with a 305/325 tire combo. Most people use skinnier fronts that would cause this to become a bit understeered so adjust your spring or tire choice accordingly.

As a sidenote to others looking for lift system options, the complete tankless Stance front axle 50mm lift system costs ~$840. It's easy to retrofit on an already build car. The only requirement to fit it is that your shock has enough stroke(wheel travel in droop) to utilize the lift and for a GTM your shock has to function when installed body up/piston down. I have zero affiliation and didn't ask for and wasn't offered any discount. I am just excited about how well it works, to have my splitter on at all times and a nice low rideheight. The kit is unobtrusive on track aside from minor additional unsprung weight.

Here's a quick video showing the lift in action. https://youtu.be/SJ2ONMN1NiY

[Apexspeedtech]

You could make a basic drawing with the eye to eye distance at resting, and max diameter. The Swift springs outer diameter measures slightly less than ~3.25". Clears front upper A-arm, rear CV boot. If your shock choice has a "long leg" and short body/spring then you could get away with bigger diameters but why risk it.

As others have mentioned the shocks for the GTM aren't the same as C5/C6. The GTM shocks mount with eyes top and bottom. Spring rates would be wrong and shock valving would only be good with some luck if the adjustment range was great enough. You do need to start from scratch and spec a shock.

KW supports a lot of custom programs and should definitely be able to make a set of shocks to spec. Give them vehicle weight, axle weights, motion ratios and intended spring rates and intended use case for the car, they'll come up with a great spec. For track spring rates, I would consider 65/115 N/mm to be the softest you should go to, that's if you install swaybars and wing. Those rates have been successfully developed by Wilbers, I found them very balanced with a 305/325 tire combo. Most people use skinnier fronts that would cause this to become a bit understeered so adjust your spring or tire choice accordingly.

As a sidenote to others looking for lift system options, the complete tankless Stance front axle 50mm lift system costs ~$840. It's easy to retrofit on an already build car. The only requirement to fit it is that your shock has enough stroke(wheel travel in droop) to utilize the lift and for a GTM your shock has to function when installed body up/piston down. I have zero affiliation and didn't ask for and wasn't offered any discount. I am just excited about how well it works, to have my splitter on at all times and a nice low rideheight. The kit is unobtrusive on track aside from minor additional unsprung weight.

Here's a quick video showing the lift in action. https://youtu.be/SJ2ONMN1NiY

My only reason for going with the KW kit was my prior experience using them on a Porsche GT2 build, and frankly I'd rather go with something cheaper first and let the owner get some miles on the car. If he decides to track it, we'll look at upgrades then. Will the Stance kit work with the provided KONIs?

[RR46]

My only reason for going with the KW kit was my prior experience using them on a Porsche GT2 build, and frankly I'd rather go with something cheaper first and let the owner get some miles on the car. If he decides to track it, we'll look at upgrades then. Will the Stance kit work with the provided KONIs?

Someone else had posted in a thread about this that the Konis don't work upside down, but looking at how mine was originally built based on old photos it had the piston down on the front axle, in that case it could work if the stroke is long enough. Someone with a Koni equipped GTM would have to chime in on this.

[VRaptor SpeedWorks, LLC]

Originally, the GTM's shipped with yellow Konis which worked in any orientation. Later (not sure if it was a clean break at the Gen II?) they switched to the black Konis....and those can only be mounted rod up or they don't work.