Is the harsh street ride on my coupe the price I have to pay for terrific handling on the track? I mean, it's so bad that the rear can get airborn if I hit the right bump in the road. Experimenting, I put the stock de-arched leafs back in, and it worsened both the handling and the ride! The shocks, BTW, are KYB gas, not the stiffest by any means. Is this a normal tradeoff? I think the only way to alleviate would be to put stock (non flattened) leafs in and use lowering blocks, but that would screw up the handling for sure. Or, I could fabricate a 4 link setup with coilovers (someday).

Matt unfortunatly this is what happens with most cars . Unless the roads are really good the ride is pretty harsh with good race susspension.
What kind of spring rate are you using?? I had 200lb with my A14 and now have 275Lb with the ca18 Im quite happy with this setup its ok on good roads but need a kidney belt on rough roads. Its brilliant on the race track.
I have seen some spring setups with like a short softer spring up the top I pressume this would help. The first bit of susspension travel would be a bit softer and once it has reached its limit it works on the harder springs.
Errol may have nore information Im pretty sure I saw that kind of setup with one of his SERIOUS struts.
Cheers Andrew

Let me be a litte more specific: my gripe is the harsh rear ride on my coupe. The front is quite nice using 150 lb. springs. But what's with the rear? No compliance what-so-ever! Is it the flattened leafs that make it so? No other vehicle that I've modified the suspension on had this problem. Like I said, I'm sorta stuck because if I try and improve the streetability, I'm sure to screw up the trackability. Any helpful ideas or suggestions are most welcome.

Hi Matt,

First question that comes to mind is how much space is between the top of the axle tube and the rear subframe (if you can call that piece of tin a subframe ;-}) when the rear suspension bottoms out?

Just had a brain fart... What functions as a bump stop on coupes? I'm a sedan guy and the bump stops on the sedans are part of the rear shocks.

Is is possible to relocate the bump stops to gain suspension travel on coupes?

On sedans I have relocated the top shock mount straight up to get more usefull suspension travel. On my current car I plan on having the rear springs de-arched to be flat when loaded, increase the length of the rear shackles to set the springs parallel to the ground, then use lowering blocks to set the ride height. The lowering blocks will have shock mounts built into them so I won't be loosing so much of the suspension travel. You do have to be carefull to make sure the bump stops hit before the axle hits the underside of the body works though.

I have not found lowering blocks to be detrimental to the car's handling. Last race car had de-arched springs and 2" lowering blocks. We got several top time of days the last year that we autocrossed the car.

Gary

If you re-arch the springs over the point where they're flat, they stop working!!
I've seen too many guys do this. Stick with the lowering blocks, and add some trampbars. If you re-arch the springs, keep it sensible!

The other thing with coupes, is that the rear shocks are at a 45 degree angle as stock. If you re-arch the springs, the angle gets more acute, and the shocks dont work!
Lowering blocks dont cause this problem, as the bottom shock mounts are on the lower plate, and the lower plate stays in the same place when you add lowering blocks.

Other than that, check for enough clearance between the bump stops and the chassis rails.

good info!!

i have a question though, i think my road car is too tail happy, the limit of my grip is definately defined by rear traction, i never get understeer unless i really try to

the setup i had was basically stock but with an extra leaf on the bottom and 2 inches of lowering blocks, i also have h190 diff and flares so tyres are sitting out a bit, the tyres are in good condition, it also has pedders sports gas shocks

i have taken out 1 inch lowering block but havent driven it yet, i did this to stop tyres scrubbing with weight in back

i think the suspension is too hard and therefore uncomfortable in the rear but am prepared to live with it for extra handeling

So im wondering why does it seem to get so much slide in the rear, the car turns in very well as the front suspension is pretty good too, may it be that the speed im turning in is just causing loss of traction at the rear when the rear comes round?

[edit] i suspect the suspension is too hard, does this sound right or not?

Yep, the hard the spring, the more 'work' that end of the car does, so a harder rear generally means more oversteer.

So, you could put a 120y swaybar on the front perhaps, or stiffen the front a little...

The stock rear geometry has a fair bit of roll understeer, so all things being equal it shouldnt oversteer without being provoked.

Ive found that 1200's love having suspension travel, a higher car will handle more predictably than one which has been lowered without any provision for more travel....

thanks, the front has 120y swaybar and stanza struts with 20W/50 engine oil in em, it also sits wider, so i dont think i can get it much more stiffer

i may try removing the extra leaf one day..

Ahh Ok I misunderstood the question. Im no expert but from my experience the best setup for both drivabilty and handling in the rear is a custom rear leaf spring setup its not flat like some ive seen. It has reverse eyes both front and back so it still has a bit of travel but sits 3" lower It has shortened bump stops and modified floor pan to clear the diferentail. the shocks had to be changed as the stock length ones where bottoming out from memory.
It has an extra leaf and also a half leaf at the front to help stop tramp. We fitted the extra leave aftre teh lkast power upgrade as the ca tourque was starting to make a nice S shape out of the springs bending the front up.
The setup I have now I bought from and was moddified bye John Taylor at pedders in sydney he has raced 1200 for many years with lots of sucsess. not much helkp to you being In USA I can take a picture and scan it in if you like to comper teh stock spings to mine??
Cheers Andrew

Matt your car should not ride poorly becuase of the mod's. I use Nissan Comp rear springs (flat) , I will tell you I had to change/cut the bump stops. With the Nissan Springs there was only about an inch of travel availible.It sounds like the car is bottoming out. Also I had to change the shocks - I got a pair of the Koni adjustables , the old style non gas type that you bottom and then turn to adjust. Everyone who has ever driven the car remarks how well it rides. I am not a kind driver to the suspension , I pound the curbs mercilessly with the car and it never upsets it.
Now 1200Rallycar , I'm curiuos as to under what condition your car oversteers. Are you carrying the brakes all the way into the apex or does it oversteer on constant throttle etc.
Carrol Smith's "Tune to Win" book says to always work the end that is a problem. So try soften up the rear. If the shocks are adjustable then soften them up or back off the sway bar anything over a 5/8 inch rear bar seems to make the car tail happy over 45 mph. If you have no way to soften the rear then by all means stiffen the front.

Tom