How to upgrade suspension without compromising comfort

theruleslawyer said:

I think the scca tt classing achieves the opposite of the intended effect. Its a laundry list of what you need to do to compete in a class and not just a menu.

Maybe it tolerable at the lowest classes, but it still picks winners in classes as different cars respond differently to that list. At higher classing that list really explodes and it still suffers from the issue that a single mod can throw you into really rough classing super quick. 
 

SCCA tt classing seems to be more about attempting to attract their autocross audience to TT than anything. The prep levels are nearly identical and they support alternate classing eg ST cars in tuner. 
 

It is a weird choice too as most people seem to progress through hpde before reaching TT. While in hpde they learn than scca solo rules were not built with track in mind. I wish they had gone with a more track focused ruleset. Id be far more interested in competing under nasa or even gridlife if the series weren't so scattered geographically. 
 

But back to the main point- dual duty isn't that hard. It just requires pretty expensive dampers. The issue being that cheap ones are harsh at rates suitable for the track. Better dampers can manage high spring rates without that edge. 100% liked my Ohlins better than the stock suspension on my old m4. I've heard the same thing from owners of even more expensive dampers like mcs or jrz. The challenge is everyone wants to throw on a set of $1k bc coilovers and is surprised when they ride like ass. 

Kind of off topic but if the goal was to attract autocrossers they did a bad job because they went out of their way to create sport class which very specifically doesn't align with autocross street class. Tuner is pretty close to ST but like....it's also a very common set of modifications. And the upper classes aren't very similar to autocross. Cars responding differently to mods is a problem but it's also basically impossible to get away from. The points system has the same issue if mods are worth the same number of points regardless of the car they're applied to, with the added bonuses of basically infinite combinations to try to police and...math. The only thing that truly solves it is spec lines which is a huge clusterberkeley that nobody wants to deal with. Straight power/weight might be a bit of an improvement but still ends up needing a bunch of modifiers (yay more math) to work out well, and requires everyone to have a dyno sheet for their basically stock car. I don't love SCCA classing but I also have yet to see, or dream up myself, anything comprehensively better that isn't basically unrestricted.

JG Pasterjak said:

The reality is that any ruleset that applies the same allowances to different cars is not about creating parity, it's about creating accessibility. The only way to create parity is with specific allowances for specific platforms, and ain't no one in the club TT sphere willing to take on that ball of snakes. Some folks think the NASA format solves it, but all it really does is moves the window toward hyperspecialization and away from any pretense of daily drivability.

The NASA TT classes definitely don't solve it.  Those rules are really written for the Super Touring race classes, with TT being kind of an afterthought.  From what I can tell the fast TT cars are usually ST race cars where the drivers are double-dipping to try to win more contingency tires.

dps214 said:

Straight power/weight might be a bit of an improvement but still ends up needing a bunch of modifiers (yay more math) to work out well, and requires everyone to have a dyno sheet for their basically stock car. I don't love SCCA classing but I also have yet to see, or dream up myself, anything comprehensively better that isn't basically unrestricted.

I like power/weight dyno classing for road race cars, where the cost of generating a dyno sheet every couple years is a pretty minor factor.  I agree it's a non-starter for stock/street autocross classing.

dps214 said:

Kind of off topic but if the goal was to attract autocrossers they did a bad job because they went out of their way to create sport class which very specifically doesn't align with autocross street class. Tuner is pretty close to ST but like....it's also a very common set of modifications. And the upper classes aren't very similar to autocross.

...

Straight power/weight might be a bit of an improvement but still ends up needing a bunch of modifiers (yay more math) to work out well, and requires everyone to have a dyno sheet for their basically stock car. I don't love SCCA classing but I also have yet to see, or dream up myself, anything comprehensively better that isn't basically unrestricted.

Because stock class would be a terrible idea for TT. Aligning with it would put dangerously underprepared cars on track IMO. Sport is basically minimal track mods. Tuner literally cross classes with the ST classes. You can chose to follow the ST rules. Max is CAM and X. Again literally cross class legal. I can understand their tracksprint series being focused on having a compatible ruleset. For TT I'd rather see something that makes it easier to cross compete in nasa and gridlife.

Keith Tanner said:

As much as you can get, really. We have something like 7.5" of travel in the rear of our high end ND Miata suspension, and the press reviews of that stuff have been superlative.

The big thing is the balance between spring rate and travel, particularly compression (bump) travel. You need enough spring rate to keep you off the bumpstops as much as possible, as bumpstops aren't a comfortable place to be and will also lead to abrupt handling changes. So when you take away compression travel by lowering the car, you need to raise the spring rate accordingly. In our NA/NB Miata application, that means nearly doubling the stock rate with our springs which will lower the car roughly 1". I say roughly as the stock height of an NA Miata varied quite a bit, and the final ride height with our springs is consistent. And those springs are regarded as having a very good ride quality for a performance spring despite that spring rate, when in fact it's because of that spring rate.

Can you come up with a rule of thumb that decreasing bump travel by 50% means you need 100% more spring rate? I suspect so but I've never mathed it out specifically. It seems like it should work that way, the suspension would only move half as far on a given bump. But there may be an exponent in there I'm neglecting. I should check.

I would be interested to learn more about suspension travel and it's effect on handling. If you ever wrote anything up (even high level) I would read it. 
 
Been thinking about a crappy old car for DD duty. A perfect DD (in my mind) would be slightly raised on 15s and have loads of travel. I want a rally car. Suspension motion is fun and something that can hop curbs (in reason) and coast over speed bumps is perfect as a real world DD. So suspension travel, and how to get it, has been on my mind lately. 

My lowered racecar has more suspension uptravel than my XJ Cherokee. It is pretty fantastic honestly. I never hit my bumpstops when I drive over the curbing where I see other cars bottom out and become unsettled. I would love if my other cars could be both that low and have that much travel. Gotta love a german luxobarge

rhammond said:

Why do you use positive toe in at the rear? You shouldn't need the understeer from the toe with the -3 deg camber.

My daughter's M440i cabrolet has the factory rear alignment of 6' toe in with -1.35 camber. The rear tires lasted about 10,000 miles so she gets a new pair at each oil change. After the first pair, she got an alignment at the dealer. They INCREASED the toe to 12'. I suggested getting it aligned to zero rear toe. She said no, that's not the BMW specification. 

C R Hammond

The more camber you have, the more opposite toe you want for even tire wear. A good working relationship is .4 per degree of camber. 

The other factor is, you are looking at static toe. What does it do dynamically?  The old trailing arm suspensions had a LOT of static toe in because they would toe out under cornering loads.  Modern suspensions are better but the principle is the same: static toe is only what we adjust because we can't measure toe dynamically.

The concept of daily use comfort is a relative thing.  Those of us who are truly old school (or just old!) sort of grew up with seriously stiff suspension (autocrossing lowered and stiffened Spridgets in the 70's) and we became accustomed to relatively firm suspension.  My 981 Boxster S  with factory X3 suspension and my 996 911 coupe with H&R springs and Eibach swaybars have close to track day performance and would be considered stiff by most folks.  Yet my wife and I have made many trips in both cars.  They are less "comfortable" than most cars, but do give something back in emergency handling and controllability.  Not debating the article, but providing some perspective. 

Interested in hearing how the alignment ended up working...

I tried to tune my E90 similar to how I did my E36 and it was an unmitigated disaster (1/8" out f, 1/8" in b)... SO different to get a similar feel. I had started with VERY similar settings to what you all did with the F30, but ended up backing off much closer to OEM (0 front and 0 rear toe), and just focused on camber (maxing out front and -2.2 in the rear) and it got me with a really similar feel (albiet in a 800lbs heavier car).

randallprince said:

Interested in hearing how the alignment ended up working...

I tried to tune my E90 similar to how I did my E36 and it was an unmitigated disaster (1/8" out f, 1/8" in b)... SO different to get a similar feel. I had started with VERY similar settings to what you all did with the F30, but ended up backing off much closer to OEM (0 front and 0 rear toe), and just focused on camber (maxing out front and -2.2 in the rear) and it got me with a really similar feel (albiet in a 800lbs heavier car).

So far I like it a lot. It's not the quickest reacting car I've driven, and takes a while to take a set, so I think whatever front toe out you can give it definitely sharpens the inputs a bit. It's still no Miata, but it turns in with some authority as long as you don't instantly overwhelm the front tires.

It does have a tendency to step the rear out when the tires overheat, but it's easily controllable. Certainly no good for lap times, but it's not scary at least. I think that might be e-diff weirdness going on, too. 

Tom_Spangler (Forum Supporter) said:

Keith Tanner said:

the article reads like it was heavily influenced by the vendor

I mean... that's kind of how it works, right? No disrespect to GRM or the vendor, but these articles tend to be thinly-veiled advertisements most of the time. And I get it, I work in marketing, my company pays big money for "neutral" articles and longer form content that's absolutely intended to make us look good without being too obvious about it. It's just how the game is played, and kind always has been in enthusiast magazines.

If you wanna see how the car hobby and its magazines have changed - look at Hot Rod or Car Craft Magazines from the mid 60s before the muscle car era exploded then look at Hot Rod.

The 60s mags used to give Welding instructions on how to notch frame sections and torch straight axles to lower King Pin. Now its "Look at this new part that will make your car beautiful, faster, and easier to drive. Or - look at a motorcycling magazine when a manufacturer releases a new model. Every year Car and Driver would declare "This is the best Porsche 911 EVER!" The next year they'd say the same thing.

This is how the industry propagates itself. Welcome to capitalism and survival. No fault of any involved - we all have to make a living. 

My tone in this comment is surprisingly negative. I'm happy it is this way! Really!

Well, as long as J.G. isn't extolling the virtues of free MaxpeedingRods suspensions, or Linglong tires I'm okay with the way things are.

In reply to seeker589 :

I got a subscription to CC in 1983 and, while I have long lost my magazine collection, I remember a lot of junkyard spotters guides and stuff.  Certainly there were advertorials but there were also interesting things like making alignment and boost tweaks to a new Charger Turbo to get it in the 13s.  Not "do this and add this" but "we realized that we could increase traction by making the camber zero when launching, so we took photos of the car launching, then raised the car to that height with a jack, and set the alignment to zero degrees camber and slight static toe out at THAT height, so when under acceleration the camber and toe were zero, and this was worth 3 tenths for our 60' times" kind of explanation for the WHY they did things.

Does anyone know as a rule of thumb how much lowering a car by a given amount helps lap times, assuming suspension geometry stays the same? I remember seeing a simulation where someone  calculated it out purely from a lower center of gravity causing less weight transfer perspective and the impact was impressively small, although I do remember thinking that long races are decided by less.