Konis gone soft, or am I nuts?

 So, at the auto-x yesterday, in a fast(er) right hander I notice I'm touching the fender liner. That corner has the most sustained corner speed you could carry on the course.

 Next best tire/suspension loading opportunity was 2 gates away, a super slow speed left hander, and the car planted and turned fine, no touching the fender liner. 

I had previously thought the left front was a little soft, but chalked it up to my sense of paranoia after checking for a leaking damper and finding it dry. 

Car seemed to respond to damping adjustments, best I can feel (probably more so in the rear,  I figure more noticeable effect on  lower spring rates?).  NB Miata, 448/336, 12/12.25 ride height, 205/50 RT615s, fwiw.

Is it possible the oil and gas has mixed a little, softening the compression curve?

Seems to ride and handle fine for daily duties, except on certain irregularities where that left front does feel a little soft.  Not sure what's up. 

Once the car has reached a set, the shocks don't have much influence. If you're rubbing, that's because the geometry of your suspension will allow you to rub. Could be a degraded bumpstop, could simply be that small alignment differences left to right are enough to make the difference.

I have experienced a 'worn out' Koni, but what Keith said is more relevant to this situation. The shock won't affect the final amount of body roll you're going to get, it will just have some affect on how quickly you get there.

That's what she said.  

Is it fair to say that it's easier to bottom out on a "blown" damper than a fresh one?

Would the same mass accelerated faster travel "further"?

If it didn't feel like the driver front bottomed pretty easily on certain bumps, I'd chalk it up to "grippy" 205s compressing the spring more than "sport oriented" 195s and time to up my spring rate. 

But the passenger front never bottoms hard/fast/easy (and, yes, I'm now worried about what Datsun310Guy will say next!).

IF you had different tires between not rubbing and rubbing, then yes it just sounds like it's simply time to change spring rate or otherwise limit body roll. 

I don't think it's the main issue but yes, it is easier to use up all your travel on a worn damper. BUT... that mostly applies to bumps/impacts. Compared to bumps and road imperfections, the suspension movements that happen as a result of steering inputs happen relatively slowly and the damper would be less of a factor in 'bottoming out' there than it would be over bumps. 

If you think the damping is more or less fine on the front struts you could just space out your bumpstops or run longer ones. That would effectively increase your spring rate only near the end of travel. I've done this on multiple vehicles to fix rubbing issues. 

In reply to Vigo :

It has been on bumps, not driver inputs (heretofore, anyway) - so while the unit may be a little suspect (Thank you, Tucson, for spending $200M on an electric street car that goes 4 miles and will NEVER come CLOSE to paying for itself while ignoring the roads and screwing the half a million people that drive on them; and thank you, Pima County for having enough budget to maintain the roads, but ignoring it for God knows what - screwing the other half million people in the area, who drive on the crappiest roads this side of the Mississippi... end of rant), sounds like I need more spring rate regardless if I want to stay at this ride height - and I do....

 Thought I'd update this. 

After watching the gopro, I definitely need more spring rate - I had the same bottoming issue side to side, just didnt realize it while driving.   And, my left front still bottoms over seemingly inconsequential bumps...

I'm thinking a 550lb spring, an extra 100lbs in rate probably should do it, right?

That said, normal sports  tap out between 500-550, depending on who you ask, so, now, the question(s) is(are):

 Do I run Koni race up front?

How much "worse" will the street ride be if I do?

Keep in mind that I really think the sports on 448/336 with the right rebound are not bad at all, they are "comfortable for me".  But, with more rebound dialed in, they are at the upper limit of steetable  even for me. 

Or is it time for a coilover set specifically valved for auto-x/street car rates?

In reply to OldGray320i :

You’re about at the limit for Koni Sports. What I’m running on my 90 & absolutely love are 800lb-front/650lb-rear springs on Koni Race shocks(which are basically just Sports valves for higher spring rates out of the box). I have cheap coilover sleeves & ISC upper shock mounts - these also make a huge difference as they prevent the car from bottoming out, especially in the rear.

I’m also running the RB 1.125” hollow front bar & braces, no rear bar, Bauer lower ball joints & R-package tie rod ends. The alignment is -4.1* front/-3.2* rear with zero toe. The car would be faster with toe-out, but it still has phenomenal grip & is completely telepathic to drive. The ride isn’t harsh either. 

In reply to OldGray320i :

I’m trying to get a sense of your priorities here, I’ll just ask questions please don’t read anything into them.  

What bothers you most ? The fact that the tire is rubbing? 

That you might be leaving time on the table in autocross?  

That  you might need to spend additional money?   

Here’s the easiest way I know of to confirm a shock is good or bad.  Go over a speed bump at a slightly faster than recommended speed and carefully watch both fenders  dip as they hit the bump.  Assuming you hit it square, if they both go down about the same and recover the same chances are the shock is good.  

Spring rates are extremely personal.   Lotus, Jaguar, and Alfa all run softer spring rates and are perceived as having “good handling” .  Now some people want go-cart stiffness in order to go fast while others can use the softness to work the tires into better grip.

Stiff makes it easier to feel in control and doesn’t require the same degree of commitment that taking a soft suspension to the traction limit does.  But you’ll find traction not possible with a stiffer car.  

If the issue is rubbing, a gentle roll around the wheel well with a wooden baseball bat between the tire and the fender will ease the sheet metal away from the fender without any visible  indication of what you have done.   

A koni PSA:   Make sure your bump stops are good on your koni struts/shocks. They don't take well to bottoming put. Like one good hit and they are trashed. With lowered cars that don't have altered mounting points (usually lowered via shorter springs) this is even more of a concern. 
 

Lee clued me in to this a while back (10 plus years ago now). Only after I trashed a set or three on my race car and could not figure it out. 

In reply to dean1484 :

I agree 100%, however on Miatas with high enough rates & aftermarket upper perches to increase travel it’s not uncommon to run without bumpstops, as the shock body would never contact them. 

On my car I trimmed the bumpstops in half, just to have something there for a bit of a safety margin. 

Ive had a bunch of koni failures, all have just catastrophically lost dampening. Not too impressed with them honestly. 

Pete Gossett said:

In reply to dean1484 :

I agree 100%, however on Miatas with high enough rates & aftermarket upper perches to increase travel it’s not uncommon to run without bumpstops, as the shock body would never contact them. 

On my car I trimmed the bumpstops in half, just to have something there for a bit of a safety margin. 

If you can’t hit your bump stops, that means you either are limiting your travel with coil bind (bad plan), with control arm/chassis interference (also bad plan) or grounding out the chassis (ow).

There is no such thing as an NA/NB Miata that will never hit the bumpstops. You can decrease the frequency of it happening, but there is always a bump big enough. Running without bumpstops is a terrible idea. It may not be uncommon in a small subset of people but none of those people have ever spoken to a knowledgeable chassis person.

In reply to Keith Tanner :

Keith I tend to agree with you too, but the continual/annual STS thread on Miata.net made it sound pretty common among that crew. Like I mentioned I did install the ones that came with the Konis when I put my car together, I just trimmed them down about 1/2-way. It’s personally not worth the risk to me. 

Someday, those cars are going to meet an event with a mid-corner dip and they’re all going to be chasing snap oversteer problems as their suspension goes solid.

In reply to Pete Gossett :

“the ride isn’t harsh either” is a lot of what I’m looking for – if you can say that about 800/600, I think I’m ok, and it allows me to up spring rate if I go 225s, or eventually 245s.  I’ve read in several places that the Race units are not terrible with the high spring rates, with most of them running 700/400 on race/sports.  This is one more, and I trust this board over the many other Miata sites.

I still plan to daily the car for the foreseeable future, so some ride quality is important.  I don't need cadillac, but I'm looking to avoid steam roller.

In reply to frenchyd:

Well, bottoming/rubbing I don’t want, and since I’m running 205s on 15x8 et36 6ULs, that means I’m touching the tops of the fender liners, not the fender lips (I’m running NA Koni’s on my NB, shorter, so they run further up when compressed).  I could run 225s on these things and have room.

Time left is important, but as the boy calls me “Captain Slow” it’s not keeping me from class wins or anything.  That said, I’d like to keep improving my driving and holding back here and there is worth a couple tenths at a time. 

Cost is a factor as well, but if I’m at the point where it requires something purpose built for the higher rates, well, my goal is to keep improving so that’s what I’d do.  But I’m not out to spend money if I don’t have to.

The reason I went with RT615s is they have more grip than Sport Comp2s (well, those were 195,but you get the idea), but not like the RE71s, which I’ve heard have stupid levels of grip and will cover a multitude of mistakes.  What was said of the 615s is that if you’re on the right line and not over driving, they’ll do well, but not tolerate ham fisted driving – my first couple autocrosses on them says that’s about right.

As far as stiffness, the tires are generating enough grip in certain corners to bottom, so it’s need as much as anything.

In reply to dean1484 :

Yep, bumpstops, the 5x/formerly fat cat units, 30mm/36mm stiff/medium (trimmed the fronts) – I like the combo.

So, I think I’ll grab the race units and 550lb springs for the front, unless sage wisdom says to get rears too – but my perception is that the 336lb rears would be fine with the sports for now.  I think if at some point I run 700/450, which some guys had done with race/sports, I'd probably opt for race units in the rear at that point. I guess I'll ask for that advice when I get to that bridge.

In reply to OldGray320i :

I think you’ll be happy with the higher spring rates. It’s stiff, but not harsh. Here’s probably the most objective example I can give:

I was on a 4-lane road, in the right lane, making a left-hand turn onto another 4-lane road(major highway). The highway had significant tire ruts from all the truck traffic. I happened to catch a late green-light without any other cars, so I took the corner at about 35mph. Even traversing the ruts of the inside lane as I turned into the outside lane, the car never bottomed out, broke loose, or did anything other than soak up the bumps and stick.

I run 550/450 on my street Miata with Fox and I wouldn’t hesitate to drive it across the country. High rates can be made to work, but you need the shocks to match. 

Most excellent.   Thank you for the inputs one and all.