strut vs sla

[Larry_S]

I know Bob has SLA system on his Mustang. I currently have Griggs world challenge front strut system however control arms are from very early in production and I have concerns about robustness. I am considering sla system due to not requiring -3deg camber, better tire wear, wider tires possible I believe due to strut not being in way.

My car is being built for occasional open track event as well as some touring. Griggs sla is very expensive and I am not positive on the prospects of company moving forward either. There is also agent 47 which looks good but kind of pricey as well.

I guess my question is is there a way to come up with a kit purchasing some pieces from a company like stock car products and maybe griggs upper mount or some hybrid where the system could be done for say around $2500 but have cheaper stock car parts for maintenance and cost? I am pretty sure you went this route Bob but having done it what are your thoughts or others on coming up with such a kit?

[Bob Holmes]

I firmly believe that you can "home-brew' an SLA for a reasonable price. A decent reading of the coleman, stock car products and other of their ilk's catalogs can get you there.


I have every intention of pursuing it for a road car. The biggest issue for me has been whether or not to use a dropped spindle. Racecraft makes one, but I haven't wanted to drop the coin on them. I'd use a set of the stock replacement SN-95 lower control arms, a set of off the shelf uppers (which is exactly what Griggs uses) and then figure out the upper shock mount system. I've never been really happy with the Griggs tower, we actually modified it, welding in reinforcement to the shock tower. Then you have to decide what you want for anti-dive geometry, and select some shocks.


Listing the things you need, assuming the use of stock components for the K-member, SN-95 lower control arms, SN-95 or SVO spindle, brakes to match the spindle choice.


Upper control arm
Upper ball joint (if you pick the correct one you can change its height, which gives you some geometry choices)
Upper ball joint to spindle adaptor
Method of attachment for the UCA
Upper shock attachment point
coilover Shock
Geometry calculations


Clear as mud?

[Larry_S]

I already have the Griggs k member and lower control arms. The main thing I am lacking is knowledge of the geometry calculations as you put it. Maybe when I finish degree working on now I will take a class on suspension dynamics or something to get a basic understanding of what is important and how to calculate or simulate. Do you still have an area on web showing detailed pics of your car as I would like to see how you modified Griggs mount and how uppers are mounted.

[Raven855]

Larry, there are some very good pics over on corner carvers of Mustang SLA. You will have to registar to see them. Beware that posting there is not for the faint of heart.

[Larry_S]

Thanks for info. I have been member of corner carvers for many years and read that site daily. I am specifically looking for pictures of Bob's setup as he went with hybrid I think using some Griggs pieces, some stock car parts, and modified shock tower it sounds like. Just kicking idea around now of what direction I want to go long term. I was considering selling SVO and purchasing 2012/3 GT but after serious consideration I am not prepared for depreciation that will result with new car. So having said that now considering improving front suspension and SLA seem like way to go for long term plan for street and track balance. I may just buy new Griggs arms for front with provisions to change to SLA in future and run strut system for time being. As I mentioned in first post my Griggs arms although not many miles are from the early production run and as with all things mechanical improvements have been made over years making me weary to use them as is.

[Raven855]

I remember a few years back when Griggs had some racetrack failures on some of his arms, though it seems to me that there was a question of abuse or overuse on the parts. I know that Bob was considering reposting the pictures, hope he does. Overall a great read.

[Larry_S]

Well I know they have improve their design. Having said that their parts are not designed for the rigors of daily driving as there is a balance between weight savings and robustness. The ones I have are just very old and need to be replaced. It would be a bad thing if that particular part failed on track. ;)

[Bob Holmes]

I'll get some pictures up. Remember that my set up uses Sweet spindles, which you cannot adapt to a street app given that they push the wheel and tire wayyyyyyy out past the fender line. Even with Maier's 3" flared fender mounted 1.5" outboard, I had to have special CCW wheel halves built to pull the tire within the required spec.

[Bob Holmes]

http://i136.photobucket.com/albums/q181/horsewidower/Mid%20build%20photos/P1000685.jpg

http://i136.photobucket.com/albums/q181/horsewidower/brakes/P1020036.jpg

[Larry_S]

Are you using a modified stock spindle? If so do you have pictures of how it has been modified for the upper arm attachment?

[Bob Holmes]

No, not a Ford. Its a Sweet spindle and Howe hub.

http://sweetmfg.biz/pages.php?pageid=15

http://www.howeracing.com/c-479-howe-hubs.aspx

[Larry_S]

How does the Griggs lower attach to the Sweet spindle?

[Bob Holmes]

With a high misalignment variable height ball joint angled the way I told my fabricator to build it. I wouldn't suggest that someone follow this route.

Larry, let me take a picture of an SN-95 spindle with the upper ball joint adaptor. I've got a couple in the boneyard.

[MustangRacer18]

Im currently working on a made for racing fully adjustable k-mem design that I will hopefully have done and ready for market by end of year so stay tuned. It will be all slugged out NASCAR style (as this is my background) so you can change pickup points to where you want them for different tracks. I'm using Howe latemodel hubs, ball joints, misc pieces. They have a road course spindle Im working off of too that's already setup for 6-piston wilwood calipers. It will have different levels for different price points but Im hoping my full all out version will be just under agent 47 price point. I'm putting my full race engineering background into this (I work in racing professionally). I also plan on having setup software that comes with it for free so you can put in where slugs are and it will spit back out where geometry points like anti's, instant centers, jacking, roll centers, etc will shake out.

[Bob Holmes]

That should be very interesting.

Without giving any of your secrets away, I hope you'll share some of your design exercises with us. I really enjoy this process.

[MustangRacer18]

Not a problem.... :D

[SVOC]

I see there are some CC member's here and thought I would contribute a few photos, the first if any one remembers the throw down between Bruce and Bill Mitchell of SVD over the ackerman discussion:

https://sphotos-b.xx.fbcdn.net/hphotos-snc6/185992_196882796997448_7211683_n.jpg

https://sphotos-a.xx.fbcdn.net/hphotos-ash3/182019_196883033664091_7388634_n.jpg

https://sphotos-b.xx.fbcdn.net/hphotos-snc6/181541_198336773518717_2226219_n.jpg

https://sphotos-a.xx.fbcdn.net/hphotos-ash4/189219_198336403518754_5719488_n.jpg

[SVOC]

And of course another look at the GR40RT set-up pre-Bruce sellout:

http://www.explorerforum.com/photopost/data/3802/PA100681.JPG

https://sphotos-a.xx.fbcdn.net/hphotos-ash4/419414_253914191294308_7904240_n.jpg

https://sphotos-b.xx.fbcdn.net/hphotos-snc6/254609_253912857961108_5889612_n.jpg

[MikeFleming]

There's a serious lack of red in those pics.

Just sayin'

[SVOC]

well instead of warming the bench, you could come out here and play with us :)



Don't be shy

[MikeFleming]

It's a really comfy bench.

[Bob Holmes]

Who's spindle on the Griggs pictures?

[SVOC]

Who's spindle on the Griggs pictures?

the spindles on the GT500 with the GR40RT are Bruce's, using the Porsche 996 bearing which was lackluster to be nice, heat/weight whatever the case may be for failure, it always came at a very inopportune time :/

https://sphotos-a.xx.fbcdn.net/hphotos-ash4/419414_253914191294308_7904240_n.jpg

I had a fairly in depth conversation with him over this at dinner one night, before Colin pissed him off about the whole thing, saying that him and the Cortex guys had already had a solution, but couldn't prove anything to me as they hadn't put it through any track testing.

https://sphotos-b.xx.fbcdn.net/hphotos-snc6/281910_253914384627622_8113958_n.jpg


This didn't do me any good since I couldn't get 200 miles street use or 1, maybe 2 days of track use before I get a pre-failure noise to total failure ratio critical.

https://sphotos-b.xx.fbcdn.net/hphotos-snc6/262404_253912771294450_6059166_n.jpg

[MikeFleming]

So you end up with bad hubs or bad bearings? Was that hub from a 996 - don't they weight abut 2900 Lbs? - being used on a GT500, weighing about 4000?

[SVOC]

Mike, the bearing would fail on the hub, but yes for the same reason, the heat and mainly the weight the bearing from the 996 would, fail, and lets keep the record straight, that's the bearing in the rear hub/upright on the Porsche 996 that is in Bruce's aluminum hub/knuckle assy.

[SVOC]

weighing about 4000?


This is before I cross weighted the car, but total was 3685lbs

https://sphotos-a.xx.fbcdn.net/hphotos-ash3/581466_494898343862557_2065064547_n.jpg

https://sphotos-a.xx.fbcdn.net/hphotos-ash3/523810_494898333862558_1458222010_n.jpg

[Patrick]

Try making a spacer for the bearings. Sort of like a pinion bearing spacer, but for the front hubs. I used them in many 6, 12, 24 hour endurance races with no failures.

[MikeFleming]

I assume that weight is without driver?

My EVO weighed 3651 when I first got it (full, no driver). It's about 150 Lbs lighter now (but I still weigh about the same).

[SVOC]

I assume that weight is without driver?

My EVO weighed 3651 when I first got it (full, no driver). It's about 150 Lbs lighter now (but I stillweigh about the same).

Yes that is without drive, and there are two of us at two very different weights that is has to be set-up for pending on who is driving, funny thing is the other driver doesn't know how to set the car up, so I have to use sacks of weight to set-it up for me.

[SVOC]

Try making a spacer for the bearings. Sort of like a pinion bearing spacer, but for the front hubs. I used them in many 6, 12, 24 hour endurance races with no failures.


Pat go into a little more detail in what your trying to explain, are you talking about putting pre-load on the bearing?

[MikeFleming]

My SVO after paint and re-assembly, ready to go (and petrol tank full).
1654

[Patrick]

Pat go into a little more detail in what your trying to explain, are you talking about putting pre-load on the bearing?

Oops, I didn't see that post.

I made up spacers that fit between the inner and outer wheel bearing. Pre assemble it on the bench to measure free play. Surface grind the spacer to get to proper dimensions. For steel hubs, I went with..0005 to .001'. If using an aluminum hub, you may want to bring the hub up to operating temperature before measuring. The target was to have as close to zero free play at operating temp without any preload.

That was in a class where I was restricted to using factory stock hubs, bearings and struts. On another car in a less restricted class, I replaced the stub of the spindle with a mini stocker rear axle spud from Speedway Engineering and their aluminum hub. That assembly uses very stout bearings which fit an IHC front spindle or a Jaguar XKE differential.