About two years ago I picked up a set of used Vishnu/Gerard spec Ohlins from a friend of mine who recommended that I get them rebuilt because not only were they pretty beat up, but he had upgraded the springs from 450/550 lb/in to 550/700 lb/in and not had them re-valved appropriately. So finally over the winter I had them rebuilt and re-valved, and now I have a properly functioning set of dampers.

Now these dampers only have a rebound adjustment, so even though compression is slightly affected by turning the knob, it's only rebound that is worth discussing. So under braking if the car nose-dives too much, then I should stiffen up the rear rebound, and stiffen the front if the car pitches up during acceleration (which is hardly noticeable in comparison). Similarly for body roll during cornering.

But at what point is too much dampening? Any clues on what I should be looking for to find that sweet spot where I've minimized body roll but not sacrificed grip?

 

I would say just stiffen the rears only and see if that takes care of the dive at least. Are you trail braking, if so is the dive affecting you corner entry?

If you had a separate compression adjustment it would be a different story.

 

Adjusting your rebound isn't going to vastly affect the overall spring rate - ie the braking dive or the pitch left-to-right. I think you might be asking too much from that little rebound knob!

You'd be better off reducing weight, lowering your center of gravity, lowering the car and/or raising your spring rates to migitate those effects. 550/700 is about 10k/12.5k - a pretty common setup for Evo's that both road-race and autocross so I think you're ok there.

What do you use the car for exactly and what does it weigh?

 

You shouldn't be using the rebound to effect how much a car rolls, only how fast it rolls. What it basically does is slow roll by increasing rate transfer. To much isn't a good thing and people seem to think a car that feels like it turns flatter is faster. Well it only slows how much roll and too much will cause a momentary decrease in grip due to too much weight transfer (Tires dont gain traction 1:1 with load).

I set up rebound by setting everything to zero. Make a run and write down the characteristic. Turn it up 2 clicks and make another. Keep doing that at each end till one end starts loosing traction at turn-in or during a bump. Then turn it back down test again. Then finally turn it down 1 click and see if I'm faster or slower. It usually takes 6-8 autocross runs to get a good feeling of them in the right place.

 

oops, double post.

 

Purely for track, and driving to and from. Car weighed in at 3240lbs with a half tank of gas, spare tire, and 6pt bolt-in cage.

Yeah sorry for not being clear. I didn't mean to say I was using the rebound to reduce the dive under braking, rather slow it down.

So slower the body roll, faster the weight transfer? Now that I think about it that makes sense. But what's wrong with fast weight transfer? Isn't it beneficial to have the weight transfer to the outside tires quickly so everything gets settled down faster? Or is that the equivalent of NOT being smooth?



- Char

 

Well I have a couple questions for you so that we may be able to better help you out.....

What is your tire and brake set up?
How much experience do you have on track, and what run groups are you in? (ie novice, intermediate, advanced/instructor)

When you're going from the gas to the brakes how smooth would you say you are? Do you pound them like your throwing an anchor down? Are you at the threshold or setting off the abs?

Do you trail brake? I have found that the Evo is very happy and composed when trail braking (at least at the tracks I have run it so far), even on the stock suspension.

When you're going from the brakes to the gas do you stab at it or do you roll on to the throttle?

To me as it is, it sounds like you just need to work on being smoother during you transitions from the gas to brake and back again.

~Shaun

 

Shaun

245/40/17 BFG R1s. Stock calipers with slotted rotors and Performance Friction 01 pads.


I run in the advance group, just started doing TT with NASA.

I think of myself as being smooth on the brake. The RS doesn't have ABS so I can't just stomp on the brake, it needs a little finesse.

Not regularly.

I was using the case of nose-dive during braking as an example of how to use rebound to affect the behavior.

My real question is how do I know if I'm using too much rebound adjustment that it's negatively affecting the handling, especially turn-in and mid-corner? With the rebound set at around the 5-7 clicks (1 being the most dampening) I found that the rear was stable, but very easily broken loose mid-corner. The benefit being that I could use the gas to make the car rotate a little bit. Lap times were faster, but the downside was that this caused the rears to heat up too much and then become greasy. So I had to back off a little to keep them grippy.


- Char

 

hey Char, what's up man. guess what i'd driving now, Troy's RS

it has the same suspensions setup you have 475/575, but i switched the springs out for 575/675. Troy said that these ohlins were valved to handle 12k/14k. they need rebuilt and i was going to send them to PerformanceShocks but they said turn around time was 4 weeks but i had an event i couldn't miss. now i've read that some shocks were made in Japan and the parts could take a lot longer to arrive. saw your shocks made in Japan.

 

WTF?! That explains why I saw MPG stickers on a IX RS What's Troy driving now?

Yeah mine needed parts from Japan as well, so it took a while. So what rebound setting do you run them? And what tires?

 

yeah, i bought his car over the winter because the shop couldn't finish the car. so i brought it home and finished it off. he picked up an 87 E30 and was going to turn it into a track car but that's on hold now because he's not sure with his job.

i don't think i can wait that long for the shocks to be rebuilt being the points season already started. i've only had 3 track days with the car so far, so i'm still trying to figure out the setup. i'm running hoosier R6 255 and i also have roll center kit. at NJMP Lightning last week, for the front set 5 clicks from full hard and rear was 8 clicks from full hard. the car rolls a little more then i would like, but i guess i'm used to my s2k being so flat in the turns. i have to get used to the evo being a little more top heavy. the car weigh 3280 lbs with 3/4 tank of gas. the car doesn't dive too much during braking but i'm not braking as hard i could because i'm still getting rear brake lock up with late braking, i have to get used to driving without ABS again. i've tried three different rear pad compound on the last three events. i'm going to try a fourth compound at the next event, so hopefully i'll be happy with this compound.

i set TTA track record at NJMP Lighting last week with 1:13.844
Troy ran a 1:13.7xx last year when the car was in TTS trim (more power, less weight) on nitto NT01

video from NJPM Lightning
http://www.vimeo.com/22539436