Thanks Balrok. Tom Berry was out in his Evo (luckily in a different class) destroying everyone like normal. I went for a couple rides with him and man that car just works. I think its time I make the jump up to 295s...

 

You know why it works? MORE REAR SPRING.

#brokenrecord

 

He wouldnt tell me exactly what rates he was running but said it was pretty close to what I run. Im at 12k F 13k R. You thinking I need to be in the 15-16k range rear?

 

I will say that the front is close, rear is not even in the ball park. 16k would be a start, still need more. I would run around 700-800 f, 1100-1200r to start. But even then, rear can use more.

Remember, 1rear spring has to control entire rear of the car when inside rear comes off the ground. Im running 800/1450 and rear spring still isnt too much.

 

Why not run a larger rear bar to maintain more compliance over bumps? Bad idea? My current setup is 12k/800 lb with a 27mm solid bar, but I'm planning to replace springs for tire clearance soon, so also considering a change.

 

Ok then. Looks like I will get some 16k springs ordered and go from there. I have the 24mm rear sway on the stiffest setting if that changes anything.

 

I'm running 16k out back in road race trim with 295's, as dallas said, for AX that's a ...start lol.

 

Still need lots of rear bar too but for a different reason. But once the inside tire is up, more bar isnt helping anything. Use springs to effect off throttle and bar to effect on throttle behavior, just dont confuse effects of excessive compression valving, stiction, or lack of camber for too much spring.

The back of the car isn't just along for the ride, the secrets to making an evo handle come from making the rear do maximum work. And you might say "but arent 2 wheels better than 1" and in this case, no not really. If the goal is to move a greater portion of total weight transfer rearward, you can only do that by putting it on the outside rear and in effect inside front.

I wish I could let everyone drive my car to understand that its not a twitchy beast to drive. Off throttle chuck it in and it just holds. If your results vary, then its not the spring causing too much rotation.

 

Do you run a stiff RSB with that?

I have 18k rear springs ready to go, but I'm worried the 18k rears with a moderately stiff RSB will make the car too twitchy. Might try to get some 16k springs as a stepping stone, or maybe just dial in some extra rear camber when I put the 18k springs on. (Road course duty)

 

How so? Rear bar still contributes some spring rate to the outside tire (Bar must twist for outside wheel to move up, so it's still in play)

 

In single wheel bump, yes-ish. In roll, not really. The bar has done about all it can at that point to transfer load and in effect more tries to lift the car.

Yes, it does have a bit more effect in transferring load, but the amount drops to less than half. In roll you expect one side to raise and the other side to droop. So you calculate bar rate as a doubled rate of two springs in parallel. Once the tire is lifting now the inner point is translating with that sides chassis mount. You change from two springs in parallel to two springs in series.

I have also tried stiffening the front bar when we're lifting a tire to see if that will have an effect of the total work the rear bar will do before getting to the lifted state (so even though it lifted, it is contributing more) and that was bust. Front end just went to crap and increased entry understeer pretty bad. Nope, dont do that...

So I still stand by, if you have enough bar to lift a tire and you dont oversteer at steady state, add spring till you do. Then add camber or toe or whatever till its ok, then add more spring. If you're lifting a tire dont add bar for off throttle performance, but you can add bar if you want better on-throttle rotation.

 

Thanks for the info Dallas. I still think I am going to start with 16k rears (shorter ones as well). Just have to check with Feal to see if they need to be revalved for that rate. Now just have to see how I can make 295s fit under the rear without hacking things apart or spending a million dollars.

 

Ya still the original progress 25mm back there on the mid setting. In Roval configuration it did fine. It's worth noting that Dallas's "conversion" has a lot to do with being non-twichy because the geometry is so much better so the car is that much more planted. It's literally the best thing since ACD tuning.

 

LOL!

800f/1600r with 27mm rear bar on full stiff.

 

I didn't want to spill anyone's numbers but there it is!

Now you need enough shock to manage those rates, but 12k/13k is a not quite the numbers run on Toms car.