spring rates with the R package

[RetroRacing]

What spring rates are supposed to be supplied with the R package? 350 front, 275 rear makes no sense to me, please explain.

Jeff:confused:

[AZPete]

Retro, if you post this in the 818R Discussions section you might get better responses.

[Jim Schenck]

350 front, 500 rear. If you are not running aero or strictly lower speed autocrosses then switch the front and rear.

more thorough explanation here: https://www.factoryfive.com/wp-content/uploads/2014/12/818R-Supplemental-instructions.pdf

[Bob_n_Cincy]

350 front, 500 rear. If you are not running aero or strictly lower speed autocrosses then switch the front and rear.

more thorough explanation here: https://www.factoryfive.com/wp-content/uploads/2014/12/818R-Supplemental-instructions.pdf

Hi Jim
Nice to see you posting here.
I understand that you want stiffer springs for higher down force.
I don't understand the radical change of swapping 350f 500R w_aero to 500F 350R w/o aero. Can you explain the technical reasoning behind this?

What would you recommend for higher speed track days with no aero?
Thanks
Bob

.

[Jim Schenck]

Bob,

We have found that mid-engine cars have a tendency to creep more and more toward oversteer as the corner speeds go up, basically it is a pendulum affect of the mass of the engine being more toward the rear of the car. For a non aero car that is going to be run at higher speeds the safest setup is to tune for neutral in the fast corners and then live with some push in the lower speed corners. For an autocross car that doesn't see the high speed stuff, and a lot of times likes to be on the looser side anyway, this doesn't apply. The best case though is when you can tune the high speed balance with aero and the low speed stuff with the springs, shocks, and sway bar. The setup we give is what we found worked best on a medium downforce car with a functional rear wing. For a more aggressive setup like our current car has you will most likely want to raise the rates front and rear to account for the extra downforce.

Also a lot of spring rate selection is driver preference as some drivers like the car with some body roll and others want more like a go-kart type feel. Also the differences in peoples cars in split between front and rear tire widths can play a roll in balance as well, meaning what we are giving for springs is what we feel is a good starting point for most people but is something that many people will experiment with and come up with setups to best fit their own styles. Even just between the three drivers we had testing these set-ups there was a noticeable difference in preferences. (Between John, Wayne, and Myself)

On a non Aero track day car I would start conservative with the front bar hooked up and the stiffer springs in front, this should give understeer as a baseline. If the car has a lot of push then I would disconnect the bar and go from there. Your car may be a little different with the tank up front and radiator out back but I still think you would be in the ballpark with the stock S model set-up and then tune based on how the car feels to you. If you could can find a good balance at track days with the sway bar hooked up then you may be still close for an autocross set-up with the bar disconnected.

[C.Plavan]

I personally like the springs stiffer. I bought/switched to 375 front and 600 rear. I may go even a tad higher. I increased the rebound on the shocks 50% also. This helped the car big time for me. No more driving a boat in the corners, and it helped a tiny bit with the ridiculous front tire rubbing on the front fenders (although until a design change, this will be the limiting factor of tire width (and height) in the front without major mods).

I was sent 300 front/ 500 rear from FFR

[Jim Schenck]

We were good rubbing wise on the old R with -3 camber in the front and Hoosier 225/40/17s which are a pretty short sidewall. On the newer car with the extra downforce we had to trim more off the flange between the fender and the nose so now there is room for two bolts there instead of three, but that was enough to have no rubbing with the high downforce setup on that car and 350lb springs. The new nose for the coupe is modified in that area to allow more clearance, the seam has been moved forward to the grill and the fenders themselves are about half and inch wider.

[Bob_n_Cincy]

Bob,

We have found that mid-engine cars have a tendency to creep more and more toward oversteer as the corner speeds go up, basically it is a pendulum affect of the mass of the engine being more toward the rear of the car. For a non aero car that is going to be run at higher speeds the safest setup is to tune for neutral in the fast corners and then live with some push in the lower speed corners. For an autocross car that doesn't see the high speed stuff, and a lot of times likes to be on the looser side anyway, this doesn't apply. The best case though is when you can tune the high speed balance with aero and the low speed stuff with the springs, shocks, and sway bar. The setup we give is what we found worked best on a medium downforce car with a functional rear wing. For a more aggressive setup like our current car has you will most likely want to raise the rates front and rear to account for the extra downforce.

Also a lot of spring rate selection is driver preference as some drivers like the car with some body roll and others want more like a go-kart type feel. Also the differences in peoples cars in split between front and rear tire widths can play a roll in balance as well, meaning what we are giving for springs is what we feel is a good starting point for most people but is something that many people will experiment with and come up with setups to best fit their own styles. Even just between the three drivers we had testing these set-ups there was a noticeable difference in preferences. (Between John, Wayne, and Myself)

On a non Aero track day car I would start conservative with the front bar hooked up and the stiffer springs in front, this should give understeer as a baseline. If the car has a lot of push then I would disconnect the bar and go from there. Your car may be a little different with the tank up front and radiator out back but I still think you would be in the ballpark with the stock S model set-up and then tune based on how the car feels to you. If you could can find a good balance at track days with the sway bar hooked up then you may be still close for an autocross set-up with the bar disconnected.

Thanks Jim,
Over the last 6 months we have been using stock S springs with no bar. With some old 205/45-16 53 offset tires and wheels.
The car is very loose and spins out with very little warning.

A couple of week ago we went to staggered bigger tires with a side benefit to cure the looseness. (still no bar).
With the body roll (tight autocross) we were rubbing the front fenders on the outside wheel and hitting full shock extension on the inside wheel. Could not test for looseness as we did not want to kill our fenders.

We switch to the R aero suspension set up this week and will test Sunday.
I also went up to 4.5" ride height with 600# of riders.
I'll let you know how it goes.
Thanks
Bob

[Jim Schenck]

If the car is loose and is not transitioning smoothly then the front bar would be worthwhile to try. The staggered tire sizes will also be a good step in that direction, but also if you go to the R shock and spring package then adjusting in more rear rebound will slow down the transition and make the car more predictable in slaloms or any quick left right transition situations. (controls how fast weight can come off the rear tires on turn in)

Have you scaled the car with that rear mounted radiator and your typical fuel load? If you are more rear heavy than the stock configuration then you may need to alter the spring rates to get closer to a neutral baseline.

Also if you are mainly sticking to autocross then I would at least consider power steering, I thought it would be way too much assist and take away feel but that has not been the case with our car. It makes it easy to make very fast corrections and not have to take your hands off the wheel as much.

[C.Plavan]

We were good rubbing wise on the old R with -3 camber in the front and Hoosier 225/40/17s which are a pretty short sidewall. On the newer car with the extra downforce we had to trim more off the flange between the fender and the nose so now there is room for two bolts there instead of three, but that was enough to have no rubbing with the high downforce setup on that car and 350lb springs. The new nose for the coupe is modified in that area to allow more clearance, the seam has been moved forward to the grill and the fenders themselves are about half and inch wider.

-2.6 degrees camber (All I can get safely), 225/40 R17 Hoosier tires, ~4" ride height (had to raise). 17x8" wheels with ET+38.
http://i.imgur.com/vbmJ3bll.jpg

Jim any suggestions?

[Jim Schenck]

What is limiting you from getting more camber? We didn't have to open the strut holes to get to -3.5 but if you have a little space between the ball joint and the tire that is the easiest way to get a little extra. Are you rubbing one side or both?

[Bob_n_Cincy]

Have you scaled the car with that rear mounted radiator and your typical fuel load? If you are more rear heavy than the stock configuration then you may need to alter the spring rates to get closer to a neutral baseline.


Jim
this was my corner weights without the Radiator bracket and No Body. No Passengers.
I need to do it again with the body and bigger tires on.
Bob

43906

[Jim Schenck]

That is about 35% front where we were 42% (with single driver) but I bet you have added enough to the car since then that the balance is probably different now. I would scale with driver and even with a passenger if that is how you most often run it. But if it stays close to 35 percent front you will likely need a slightly different setup than we have run, and the further apart the front and rear are the more aero can be a help to balance between the low and high speed stuff.

[C.Plavan]

What is limiting you from getting more camber? We didn't have to open the strut holes to get to -3.5 but if you have a little space between the ball joint and the tire that is the easiest way to get a little extra. Are you rubbing one side or both?

I'm rubbing symmetrically on both sides. I have no idea how you are not rubbing on the fenders, especially at the "R" ride height. We are all having these issues (818R's). -2.5 degree is the magic number for tire temps across the front tires. I do not want to cut the studs on the UCA's any more, or the aluminum adjusters (Bob's aluminum adjusters already became loose). I'm waiting for steel adjusters to come in so I can possibly cut those. I'm about ready to sawzall the top of the fenders off and making some flares that will work.

Better yet, why not change the old fender design to incorporate the new fender width? I'm not going to be upgrading to the new front end just to make "little" 225 tires fit. I have already spent way too much cash on this car. It's getting very frustrating.