View Full Version : GTM adjustable front upper control arms.
HardRocker
02-26-2020, 04:24 PM
Is someone on the forum still making these? I want a set. Thx.
beeman
02-26-2020, 09:59 PM
I tried very hard to get a set a few years ago. I talked on the phone to the guy who had initially built them, he was in Florida I believe. I think Crash knew of the guy. He was very busy at the time but agreed to build some more in the months to follow. It never happened. So I cut and rewelded the UCA mounts to achieving the geometry that I was looking for in the adjustables.
crash
02-27-2020, 11:41 AM
It's been a long time since I saw anything about the adjustable UCAs. The cut and reweld method is what we did on the PDG GTM race car. Cheap, relatively easy, and maintains all "stock" components.
GoDadGo
02-27-2020, 12:37 PM
Have you looked at any of the "Build Your Own" goodies offered by SPC?
https://www.spcalignment.com
I'm pretty sure they make the uppers for the MK-4 and Daytona platforms.
beeman
02-27-2020, 01:26 PM
Back when I was looking for the adjustable UCAs, I looked everywhere. I think I ran across options for the C4 Vette, but never C5...
crash
02-27-2020, 02:23 PM
Have you looked at any of the "Build Your Own" goodies offered by SPC?
https://www.spcalignment.com
I'm pretty sure they make the uppers for the MK-4 and Daytona platforms.
I believe the ones offered by the guy on the forums were based on SPC components.
HardRocker
02-27-2020, 03:12 PM
Our issue is the Corvette uprights carry the balljoint. So an adjustable arm would have to have a tapered bore setup and not a plate for the balljoint like the SPC parts. However I will ping them and see what they may say.
The Stig
03-03-2020, 07:21 PM
Is someone on the forum still making these? I want a set. Thx.
I think that I still have a set that I was going to use on Pandora. I can't even remember what I paid for the completed set...
I'll go out and take a look tomorrow morning and let you know.
FYI - I also have a complete set of Gen 5 Upper and Lower Control Arms, Powder Coated Bright Mercedes Silver, with new Pfadt Poly-Urethane Bushings, and New Upper and Lower Ball Joints. I was holding onto them in case I might need to use them on another FFR project in the future, but that would more than likely be either an F9 if that one gets going, or a Mk-IV Cobra. So, if there are any interested parties, let me know. I'll post this in the "for sale" area as well.
Mike
HardRocker
03-05-2020, 11:18 AM
Stig, let me know on the adjustable arms. Thx.
The Stig
03-05-2020, 11:49 AM
I have them.
https://i210.photobucket.com/albums/bb94/jmichaelbaskin/GTM%20Parts/IMG_7825_zpsuswrjnmf.jpg (https://s210.photobucket.com/user/jmichaelbaskin/media/GTM%20Parts/IMG_7825_zpsuswrjnmf.jpg.html)
https://i210.photobucket.com/albums/bb94/jmichaelbaskin/GTM%20Parts/IMG_7826_zps79vkhhs9.jpg (https://s210.photobucket.com/user/jmichaelbaskin/media/GTM%20Parts/IMG_7826_zps79vkhhs9.jpg.html)
https://i210.photobucket.com/albums/bb94/jmichaelbaskin/GTM%20Parts/IMG_7827_zpszvduv5om.jpg (https://s210.photobucket.com/user/jmichaelbaskin/media/GTM%20Parts/IMG_7827_zpszvduv5om.jpg.html)
https://i210.photobucket.com/albums/bb94/jmichaelbaskin/GTM%20Parts/IMG_7828_zpszsykxjjh.jpg (https://s210.photobucket.com/user/jmichaelbaskin/media/GTM%20Parts/IMG_7828_zpszsykxjjh.jpg.html)
https://i210.photobucket.com/albums/bb94/jmichaelbaskin/GTM%20Parts/IMG_7829_zps1dbdzqub.jpg (https://s210.photobucket.com/user/jmichaelbaskin/media/GTM%20Parts/IMG_7829_zps1dbdzqub.jpg.html)
https://i210.photobucket.com/albums/bb94/jmichaelbaskin/GTM%20Parts/IMG_7830_zpslfubaxjv.jpg (https://s210.photobucket.com/user/jmichaelbaskin/media/GTM%20Parts/IMG_7830_zpslfubaxjv.jpg.html)
HardRocker
03-05-2020, 11:50 AM
Stig, I’m pm’ing you. thx.
beeman
03-05-2020, 02:06 PM
Nice find! I'm really surprised these aren't available from a Corvette shop, given the limitations of the C5 suspension, especially with camber/caster....
The Stig
03-07-2020, 08:42 AM
Stig, I’m pm’ing you. thx.
Hi Rocker: These are yours if you want them. I'll let you know what the shipping costs are.
Enjoy.
Mike
Mike, do you have more of these? Else what was your source for the parts to build these? I see they say SPL, do they make these complete w the correct inner mounting?
crash
03-09-2020, 10:44 AM
RR- It's actually "SPC"...
https://spcalignment.com/race
beeman
03-09-2020, 12:45 PM
The key is knowing how and by whom they are being welded. The C5 arms may not have the perfect geometry, but they are proven and safe.
HardRocker
03-09-2020, 03:05 PM
I bought the set Stig had. When I get them I'll post the measurements of the SPC parts. I'll also post what SPC says about the taper plate. If they don't offer a tapered plate it would be a fairly easy option to have a tapered part machined that would fit the standard SPC balljoint plate that could either be pressed/bolted/welded (or threaded in for a Chrysler style plate).
The Stig
03-09-2020, 06:49 PM
The tapered plate was made and welded by Mike Jimmenez (Mikespms) in the Miami area of Florida.
I'm not sure whether he still checks in here on the forum or not. I bought the plate from him and he gave me a list of parts to buy.
The SPC links and connectors were purchased from Summit Racing if I recall correctly.
https://i210.photobucket.com/albums/bb94/jmichaelbaskin/GTM%20Parts/20150223_140807_zpse36mjvpo.jpg (https://s210.photobucket.com/user/jmichaelbaskin/media/GTM%20Parts/20150223_140807_zpse36mjvpo.jpg.html)
https://i210.photobucket.com/albums/bb94/jmichaelbaskin/GTM%20Parts/002_zpsjmtdzmg6.jpg (https://s210.photobucket.com/user/jmichaelbaskin/media/GTM%20Parts/002_zpsjmtdzmg6.jpg.html)
https://i210.photobucket.com/albums/bb94/jmichaelbaskin/GTM%20Parts/003_zpsdalgelgc.jpg (https://s210.photobucket.com/user/jmichaelbaskin/media/GTM%20Parts/003_zpsdalgelgc.jpg.html)
https://i210.photobucket.com/albums/bb94/jmichaelbaskin/GTM%20Parts/004_zpsesfo3syr.jpg (https://s210.photobucket.com/user/jmichaelbaskin/media/GTM%20Parts/004_zpsesfo3syr.jpg.html)
https://i210.photobucket.com/albums/bb94/jmichaelbaskin/GTM%20Parts/Upper%20Control%20Arm%20Brackets_zpsvtnra6tw.jpg (https://s210.photobucket.com/user/jmichaelbaskin/media/GTM%20Parts/Upper%20Control%20Arm%20Brackets_zpsvtnra6tw.jpg.h tml)
HardRocker
03-10-2020, 03:14 PM
Here's what I received from SPC:
"We have evaluated the C5 corvette platform in the past and have found making control arm components is not feasible at this time. Thank you for your inquiry and we will pass this on to engineering development."
Sad because the C5 and C6 would use the same setup. Don't know about the C7 but I imagine it's similar.
So for us either the entire plate with a taper would have to be made or a fitting machined to work in the standard SPC ball joint support plates. I don't think there would be a big deal to make the support brackets or machine new pins, or possibly use the old one with spacers so the clamp doesn't move forwards and backwards.
HardRocker
03-10-2020, 03:21 PM
The key is knowing how and by whom they are being welded. The C5 arms may not have the perfect geometry, but they are proven and safe.
You could weld these perfectly.
HardRocker
03-20-2020, 02:40 PM
Stig posted great pics above and some of the part numbers. The black adjusting sleeves are 5 and 4 inches long. Fully adjusted in they are 7-1/4 bolt hole center to center and 5-1/2 from bolt hole center to where it threads into the balljoint taper plate. The swivel clamps are 1-7/16 wide with a 9/16 diameter inside the rubber bushing.
RR- It's actually "SPC"...
https://spcalignment.com/race
Thanks mate, should have zoomed in better on my phone...
As an alternative solution I spoke to Borg Motorsports and placed an order for a set of offset lower control arm Delrin bushings. It won't give the ability to add significant negative camber, but in stock form only the lower offset bushings add about 1 degree to the 0.8-0.9 I see on my car at the moment. This will get the front somewhat in the ballpark of the raceproven negative camber we run on the PDG4 GTM, and that's before lowering the rideheight on my roadcar for track duty which provides further negative camber.
Borg typically sell these together with upper control arm offset bushings to achieve significant total camber on a Corvette, but for a GTM the uppers are not helpful since we can hypothetically grind the upper dogbone mounting holes, but in reality the innermost part of the upper control arms will hit the frame.
For that reason, Borg actually ended up offering to make a custom set of lowers with greater offset than their standard off the shelf product, to help achieve more than the 1 degree from the standard lower offset bushings. Looking fwd to see the final number, the bushings should be here and on the car in a few weeks.
beeman
03-21-2020, 08:44 AM
More (negative) camber is desirable, but you have to sacrifice caster to increase the negative camber. I've never driven a GTM but plan to soon. I don't see any complaints about the car "not wanting to go around a corner" but I have seen countless complaints about straight line stability/confidence at speed. So I moved the UCA mounts (currently at 7.5 caster and -1.5 camber with plenty of adjustability in all directions).
HardRocker
03-21-2020, 02:17 PM
Wow. Borg is really proud of their offset bushings at $1200. Someone with a small lathe could make them for about $50 in Delrin material and a few hours. Delrin machines like butter.
More (negative) camber is desirable, but you have to sacrifice caster to increase the negative camber. I've never driven a GTM but plan to soon. I don't see any complaints about the car "not wanting to go around a corner" but I have seen countless complaints about straight line stability/confidence at speed. So I moved the UCA mounts (currently at 7.5 caster and -1.5 camber with plenty of adjustability in all directions).
"don't see any complaints about the car not wanting to go around a corner"
lol You have not heard me working on this to beat much more modern GT3 cars in Trans Am... :)
Caster is king. Less camber is great for braking with lots of caster to give camber gain when turning. Trade off choice depends on springs and roll bars / body roll. Less roll requires less static camber. Tires like different levels too. A car that has softer street springs tends to need more camber than a stiff racecar on slicks w hard sidewall to utilize the tire. Your UCA mount mod looks super sweet. How did you mod it with respect to moving it more inwards?
beeman
03-25-2020, 01:44 PM
Yes, the GTM needs better straight line stability. And part of the reason I wanted more caster was to achieve camber gain in the corners.
I pushed the mounts in as far as possible, here's a pic I just took. Also added anti dive, I'll have to check but I think I added half the angle of the C5. The front of the front mount is now even with the back edge of the 1" frame member. Had to move the shock mount obviously.
I'll look for the preliminary alignment specs.
https://s19.directupload.net/images/200325/k6ni2pfk.jpg
https://s19.directupload.net/images/200325/o6qfl44b.jpg
https://s19.directupload.net/images/200325/fnvdjkyp.jpg
beeman
03-25-2020, 01:51 PM
Initial spec was 8+ caster, 2+ camber before adjusting on the rack. Again I think FFR specd the suspension for a manual rack which is why the caster was so low.
https://s19.directupload.net/images/200325/tn6creb9.jpg
Stig, where did you get those inner bolt through conversion brackets?
I just picked up the SPC parts via Jegs, the outer tapered cylinders via Parts Shop Max (to be welded onto the plate).
141907
beeman I did a bit of what you did to build the A-arm angle, but I used shims to only lift the fwd mounting point. Looking fwd to get the SPC arms on and measure what caster I can get with the wheels still in the right place and not rubbing (305 wide), then shake it down.
beeman
02-02-2021, 03:26 PM
What's your caster goal? And camber?
Yep, trying to get big caster with the FFR UCA mount location will drive your tire into the rear wheel well bodywork with the C5 UCA. To gain caster, while keeping the tire centered in the arch, requires moving the upper mounts forward. But with your ADJUSTABLE UCAs, you can probably make it work.
What's your caster goal? And camber?
Yep, trying to get big caster with the FFR UCA mount location will drive your tire into the rear wheel well bodywork with the C5 UCA. To gain caster, while keeping the tire centered in the arch, requires moving the upper mounts forward. But with your ADJUSTABLE UCAs, you can probably make it work.
Camber goal for now 3 degrees then eval if I need more or not. I can imagine landing anywhere from 2.8-3.5. We shall see.
Caster I normally do high 7-9 on cars I've ran but on the GTM it's still performing quite well with a lot less so no set figure in mind. Laptimes will guide where I end up.
Identified that SPC cross arms part 93410 fit pretty well on the GTM with these SPC arms.
To clear the cross arm, the top shock mount has to be moved outwards a little bit.
Other benefit. The SPC outer plate is wide offering more space vs the original C5 arm, so the Stance Aircup can now fit at the top of the coilover to reduce the unsprung weight.
143681
143682
143683
For peace of mind, I think I'll be adding some reinforcements to the inner mounts, to compensate for upper A-arm being held by 2 chassis tabs instead of 4 chassis tabs.
beeman
03-04-2021, 06:58 AM
I was thinking the original design used all 4 UCA chassis mounts? I think I recall an intermediate piece that converted the 4 vertical mounting points to 2 horizontal mounting studs, similar to the C5 chassis mounts? You could also incorporate some anti dive into such a mounting plate.
Are you referencing these? Have not found any source for these. Past contact to someone who used to make or sell these has been unresponsive.
143734
First level of reinforcement.
143835
beeman
03-05-2021, 09:12 PM
Are you referencing these? Have not found any source for these. Past contact to someone who used to make or sell these has been unresponsive.
143734
Yep, I just saw Stig posted a photo of them earlier in this thread
HardRocker
03-18-2021, 08:02 AM
Yep, I just saw Stig posted a photo of them earlier in this thread
Luckily I have these brackets but just looking at them I see how someone could use steel angle stock with a center square cut out one side, some tabs welded in, and some holes drilled. Should be easy to make. They used angle steel for the side tabs originally and welded to flat stock.
RR46, Hopefully you are someone else can help me out... where can I find the weld in taper cylinders? I tried looking online, but didn't see the part at Part Shop Max (maybe I had the wrong website). Can someone let me know where I can get the part and if there is a part #/name I can reference.
Thanks! 148110
Fred Brewer
05-20-2021, 09:23 PM
Mine in the Jig,,,,, a few years back... lol148230
RR46, Hopefully you are someone else can help me out... where can I find the weld in taper cylinders? I tried looking online, but didn't see the part at Part Shop Max (maybe I had the wrong website). Can someone let me know where I can get the part and if there is a part #/name I can reference.
Thanks! 148110
Email and ask for C5 tapered slugs for upper front control arm. They sell complete arms and don't list individual pieces, but if you are nice maybe they will help you as well.
This was such a good boost for adjustability.
Also now able to fit the aircup up top, reduces cleaning needs vs having them at the bottom, and it removes the unsprung weight off the LCA which improves wheel control = better handling AND ride comfort
152299