Mk4 Roadster/Challenge Car Front Suspension Update

[Mad Dog]

We've posted instructions in the Challenge Car and Roadster Wiki's on updating your Roadster or Challenge Car to the new Mk4 Front Suspension. Click here for the instructions.

[FFRSpec72]

Do you know when the package will ship, as I orderd a week before xmas or so and have not received an update?

[IEMRacing]

How does this compare to the S A I kit sold by Whitby?
Is the geometry better on this kit?
Thanks,
John
PS
I will not be racing with NASA, so I am not worried about the legality of the kits.

[FFRSpec72]

What spring rates (front and rear) were used on the test mule (#85)? Do we assume a lower spring rate with the sway bar installed?

[johngeorge]

Tony, I believe #85 had 700lb front, 550lb rear.

[Jim Schenck]

I lowered my front spring rates by 50lbs when I put this package on the car. I went from 750 to 700 front and I have 475 in the rear.

[FFRSpec72]

OK, I have 750's in front now and 350's in rear, so may have to change out, I assume with the Koni shocks these are the large bore springs? Where to buy on west coast?

[Jim Schenck]

I would think you might want to try 700s or even 650s if you stick with the 350 in the rear. It seems like the car would have some push with that setup you have now even?
I have been buying springs from Summit Racing, but I am sure there are other places with them locally. They are 2.5 in. ID and 8 inch length.

[FFRSpec72]

yep, I get the plow effect now, so might keep the 350s in rear and lower to 650s in front and see how that goes since I will have front disassembled with the changes anyway

[IEMRacing]

We've posted instructions in the Challenge Car and Roadster Wiki's on updating your Roadster or Challenge Car to the new Mk4 Front Suspension. Click here for the instructions.

Does anyone know the king pin inclination angle of the new spindles that factory 5 is selling?
Thanks in advance,
John

[FFRSpec72]

Rest of the front-end upgrade arrived today

WP_000004.jpg

[Jim Schenck]

John,

Kingpin angle on these spindles is around 12 degrees. (it varies based on camber setting)

Jim

[mhoward1]

Jim,
Quick question and maybe I just missed this.

What was being addressed with the lowering of the upper control arm? Are you lowering the roll center?

[IEMRacing]

Thanks Jim
That's the number we were looking for......
John

[johngeorge]

boy do the brakes fill up the wheels now..


more pics here if interested http://www.johngeorgeracing.com/gallery/seasonprep2012

[tcoon]

I finished the left side of my upgrade and I agree..the brake rotor aare a BIG improvement! my A arms were a mess after 7 seasons of use so I sprung for new ones and they adjust much more easily.

Hey John, you should check the instructions...I believe the tie rod end links need to mount above the steering arm to reduce bump steer with this setup.

-T

[johngeorge]

Tom, this article does not say where to put the bump-steer (only says for the slight bend of the arm to point front and outside), but I know it must go on the bottom with a small spacer for sure!

Look at this pic of Jim's car from the swaybar instructions (bottom pic):

[tcoon]

Thanks. I stand corrected!

[tcoon]

I checked on this further and according to the bump steer kit instructions further down in this wiki tech section the outer tie rod end should be on top. check wiki tech on bump steer line 11. hope this is helpful to everyone!

[johngeorge]

Tom, I see what you are referring to http://thefactoryfiveforum.com/conte...n-Instructions and I believe these instructions are for the fox spindles with manual steering (notice they say 3deg of caster). When you go to power steering you can crank the caster up (6+deg) effectively raising up the steering arm because of caster. To keep same bumpsteer you need to move from the top of the arm to the bottom of the arm.

[IEMRacing]

O.K.
I think it's time to pull out the old Longacre Bumpsteer Gauge.
Please, take a look at this video. This is how we do bumpsteer at my shop.
http://www.youtube.com/watch?v=Stp9kHAGfXQ

[FFRSpec72]

I would think you might want to try 700s or even 650s if you stick with the 350 in the rear. It seems like the car would have some push with that setup you have now even?
I have been buying springs from Summit Racing, but I am sure there are other places with them locally. They are 2.5 in. ID and 8 inch length.

So would this spring fit ? They are more expensive than I thought ! http://www.summitracing.com/parts/EI...0650/?rtype=10

[Jim Schenck]

Tony,
Those are correct. I found Hypercoils at Day Motorsports for 20 bucks less: http://www.daymotorsports.com/produc...L_OVER_SPRINGS
The 650s are the second to last one listed.

[FFRSpec72]

As I start the upgrade on the frontend I have a couple of questions;


What is this for, as I could not find it's usage anywhere in the instructions

WP_000042.jpg


When installing the sway bar brackets on the front of the 4" tubes, the right side looks fine but the left side seems a little close to drill the bottom mounting hole. Also which whole on sway bar were you all testing with the outer most on inner most?

Right side

WP_000041.jpg


Left side (where it looks like there will only be a 1/16 in or so left if I drill the hole)

WP_000040.jpg

[FFRSpec72]

Thanks I forgot that they added that in the front-end upgrade package, was expecting aluminum but can see it was easier for them to cut this out of steel when they were doing the other parts.

[FFRSpec72]

If your looking to replace you ball joint dust boots when doing the upgrade here are the energy suspension ones which are far better than the stock ones ENS-5-13102R and ENS-9-13130R

[FFRSpec72]

I wanted to put longer studs in the new hubs but can’t find any studs with the correct diameter knurl. Seems like they are a weird size, can anyone tell us what size we should get?

[Jim Schenck]

The ones we use in the 85 car are Moroso 46185. They are 3 in. long with a .594 knurl.

[FFRSpec72]

Jim, thanks!

[FFRSpec72]

Finished up the front end over the weekend, so items I ran into:

1. The sway bar's 2 end holes had to be drilled out to 1/2" as they were like 3/8
2. There was no mention of using 2 spacers when running the flanged sway bar bolt through the sway bar, spacer and the rod end (last step on your instructions) before you put the nut on (see pic below)

Alignment specs still the same ? Like .5 to 1 degree negative camber, 3 degrees positive caster and 1/16 toe out ? I put the gauges on the car (did not have time to play) but it looks like I can get more that 3 degrees of caster now, but not sure with only manual steering I want more or could deal with more but with the old setup that was about max I could get. Does this sound about right being able to get a lot more caster?

WP_000076.jpg

[Jim Schenck]

Tony,

On the alignment specs: We are usually more aggressive than that on camber for the race cars, I am running around -2.75 and I think most are between -2 and -3.5. It is a little bit of a trade off as the car is better in cornering but gives up a little in straight line braking, but that is where I have found my car to be quickest. On the caster and manual steering, the new set-up will allow you to run more than before because the lower SAI will reduce the steering effort. If you were happy with the effort you had you can dial in a little more caster (maybe try 4-5 to start) or if you felt the steering was a little to heavy then you can stay at 3 and you will have less effort than before. Also in order to make sure everyone can get the alignment settings they want it is legal to shorten the legs of the upper arm if needed to get into the range you want.

[FFRSpec72]

Jim, thanks will try adding more camber/caster and see how that works.