Back in the day, lowered sports car life was so much easier: Install Koni Sport dampers with lowering springs and become one of the cool kids. A lower center of gravity reduced weight transfer, and the stiffer springs helped reduced body roll while keeping off the bump stops.
Need a little more spring? A set of Ground Control coil-over sleeves …
Although admittedly I've always done front wheel drive cars, I usually go with a bit higher ride frequency in the rear than the front. This is to 'catch up' the rear to the front when going over a bump and level out the fore/aft roll of the car (prevents a 'porpoising' motion). It doesn't take much, maybe like 10-20% more in the rear.
It's always improved the stability of the car for me.
The damper body has graduations on the threads to keep track of perch and body length adjustments more easily. We had to adjust the latter to keep static ride heights the same when fitting stiffer springs.
By adjusting the body length, you were also adjusting your available suspension travel. This a really common oversight. Better to adjust the perch height and keep the range of travel the same.
One benefit of stiffer springs: reducing the range of travel used. We took notes to see how each setup affected rub over bumps on track. The narrower and shorter 235mm-wide Falkens only rubbed a bit with the initial 6K front spring setup; the contact disappeared with the 8K and 10K rates. The taller, super-fat 245mm Nankangs were another story, with massive contact at 6K, mild rub at 8K and finally clearing fully at 10K.
This looks like the typical confusion that occurs. You adjusted the travel range when installing the stiffer springs. The stiffer springs didn't reduce the range of travel, the change in shock geometry did. Stiffer springs (with no other changes to geometry, just the perch height location) will not change the possible range of travel. They'll just decrease the frequency at which the suspension gets into the far ends of travel. But there's always a bump big enough to hit the end of your travel. If you want to prevent rubbing, the thing to do is to adjust the possible range of suspension travel and to understand that's what you're doing. You don't even want the springs on the car when you're setting that, the way to do it is to fully compress the suspension and adjust so you have clearance. Then you install the springs and set your ride height.
If you're getting too much bumpstop activation, you need a higher spring rate or a higher ride height, but no change in the shock body length once it is set.
Sent an inquiry on my application as the options are pretty thin.
Funny Andy mentioned the konis and ground controls. The last time I had a mirage, the spokes crew helped me build out a custom set based off of rabbit struts in the front. It was like oh yeah been there done that.
Keith Tanner said:This looks like the typical confusion that occurs. You adjusted the travel range when installing the stiffer springs. The stiffer springs didn't reduce the range of travel, the change in shock geometry did. Stiffer springs (with no other changes to geometry, just the perch height location) will not change the possible range of travel. They'll just decrease the frequency at which the suspension gets into the far ends of travel. But there's always a bump big enough to hit the end of your travel. If you want to prevent rubbing, the thing to do is to adjust the possible range of suspension travel and to understand that's what you're doing. You don't even want the springs on the car when you're setting that, the way to do it is to fully compress the suspension and adjust so you have clearance. Then you install the springs and set your ride height. If you're getting too much bumpstop activation, you need a higher spring rate or a higher ride height, but no change in the shock body length once it is set.
Perfect segue into the next installment. :)
I have here some spacers (real thick packers) to adjust point-of-contact of the bump stop and also a set of helper springs to do the same going the opposite approach (perch movement). The spacer approach is on the car now, dialed in so that even the biggest bump will clear fully with the fattest tire/wheel combo I run.
The challenge with just moving the perch by itself is that the spring becomes unloaded and rattles around in certain circumstances. The rear of my CRX is especially prone to this. For that one, we did internal droop limiters. But the more common solution is helpers, as it is external and straightforward to install.
Once I get through the next round of tire testing, I'll be playing around with the two approaches to compare/contrast.
With those adjustable length bodies, you don't need the bump stop spacers. You can just adjust the shock body length. And yeah, either longer main springs or helpers if they're loose at full droop. Once the main spring is unloaded, you're basically out of travel anyhow.
With the amount of travel available in the ND suspension, I think we use a 12" long rear spring on our Fox setup.
Keith Tanner said:With those adjustable length bodies, you don't need the bump stop spacers. You can just adjust the shock body length.
Actually, I do. Even fully extended, there isn't enough body length to get the bump stop where it needs to be.
The sad part of all of this is that I didn't need to do any of this until this one particular depression in the track suddenly got really severe....
Can you get a longer insert from your builder? It would give you more shaft travel as a bonus. I'd be interested to hear how this setup copes with crests at speed.
Rough tracks are more interesting than smooth ones :)
Keith Tanner said:Can you get a longer insert from your builder?
Possibly. But the helper spring setup is likely the final answer. At this point, my use case is solved with the spacer, and I've got three tire tests in the queue ... so I'm not in a huge hurry to get back to the coilover detailing. "Perfection is the enemy of good" and all that...
I reached out with an inquiry about the S30 Z car chassis. They had a very fast response time and offer customer valved BC coilovers for my car, which is an intriguing option.
Similar pricing as some of the higher end options available off the shelf, but potentially superior quality.
Thanks for sharing!
Do they offer upgraded springs? Like Eibach/Hyperco/Swift? I've read plenty of stuff about generic springs not always matching the advertised rate.
Mainly just curious as my car already has a set of built coilvers and if I change them it will be to move up to MCS or JRZ or similar.
They offer Swift springs as an upgrade.
They claim to be on par with MCS, JRZ, etc
Hmm this would be the ticket for my Mk1 Rabbit. It currently sits on custom damped standard body bilsteins with Ground Control Coilover Hats and 550/450 rates f/r. Would like a nice balanced setup that is adjustable as it has never felt as balanced as I'd like.
I have a set of the Standard Street series on my Yaris and adore them so much I became a dealer for RedShift.
I love how I can wind them down and they ride better then any old drop spring and damper combo I had on it. Yet I can crank them up for race use and it works so damn well.
They have an 'X' factor during cornering I have never experienced before...granted my previous coilover experience is largely limited to low end dampers such as FortuneAutos, BCs, D2s and Ksports (back in the day). The Standards just rock and I love them. I cannot wait to be able to get a system for my autoX car.
/end fanboi post ❤️
malibuguy said:I have a set of the Standard Street series on my Yaris and adore them so much I became a dealer for RedShift.
I love how I can wind them down and they ride better then any old drop spring and damper combo I had on it. Yet I can crank them up for race use and it works so damn well.
They have an 'X' factor during cornering I have never experienced before...granted my previous coilover experience is largely limited to low end dampers such as FortuneAutos, BCs, D2s and Ksports (back in the day). The Standards just rock and I love them. I cannot wait to be able to get a system for my autoX car.
/end fanboi post ❤️
I have a set of 8th gen Fortune Auto 500s on the '23 BRZ with custom valving and rates with the Swift springs. I had a set of Ground Control with Koni's on the '15 BRZ.
The FA's are not only slightly stiffer in rates, but also ride DRAMATICALLY better on the street than the GC setup could ever dream of.
I'd be curious to see how the pace of the custom coilovers (which you've shown are faster than the Koni setup) compares to something like the XIDAs. If you're chasing tenths, is it worth it to spend more on the XIDAs?
CrashDummy said:I'd be curious to see how the pace of the custom coilovers (which you've shown are faster than the Koni setup) compares to something like the XIDAs. If you're chasing tenths, is it worth it to spend more on the XIDAs?
Maybe?
In my case, the extra pace came from a specific issue I was trying to solve: consistency of grip over a bumpy surface. XIDAs would have likely given the same positive pace result for that issue. Any other potential benefits, I can't say.
BA5 said:Although admittedly I've always done front wheel drive cars, I usually go with a bit higher ride frequency in the rear than the front. This is to 'catch up' the rear to the front when going over a bump and level out the fore/aft roll of the car (prevents a 'porpoising' motion). It doesn't take much, maybe like 10-20% more in the rear.
It's always improved the stability of the car for me.
This is generally how the OEs tune the suspension, which is why cars tend to have much larger stabilizer bars in the front than the rear, even with neutral handling.
Pete. (l33t FS) said:BA5 said:Although admittedly I've always done front wheel drive cars, I usually go with a bit higher ride frequency in the rear than the front. This is to 'catch up' the rear to the front when going over a bump and level out the fore/aft roll of the car (prevents a 'porpoising' motion). It doesn't take much, maybe like 10-20% more in the rear.
It's always improved the stability of the car for me.
This is generally how the OEs tune the suspension, which is why cars tend to have much larger stabilizer bars in the front than the rear, even with neutral handling.
Yep. Called "flat ride". And it's mentioned in the story in the discussion on ride frequency.
Andy Hollis said:CrashDummy said:I'd be curious to see how the pace of the custom coilovers (which you've shown are faster than the Koni setup) compares to something like the XIDAs. If you're chasing tenths, is it worth it to spend more on the XIDAs?
Maybe?
In my case, the extra pace came from a specific issue I was trying to solve: consistency of grip over a bumpy surface. XIDAs would have likely given the same positive pace result for that issue. Any other potential benefits, I can't say.
GRM should commision a test of this. For science!
This article seems a bit misleading. One of the benefits over a koni (or oem-like) setup mentioned at the start is more bump travel. Assuming that koni or oem have already allowed for the maximal practical bump travel, there really can't be any more bump travel, only less droop. On the NC MX5 these BC-derived 2 piece shocks seem to even reduce the available bump travel, as they replace a fairly tall oem top hat/bell with a shallower one. I assume this was because they wanted to limit shock upper mount articulation, ie were getting clearance issues with the smaller diameter spring. Can someone confirm this?
Interesting read. I bought a 2019 ND-RF about three weeks ago. It came with aftermarket springs and shocks (Swifts/Ohlins) and the springs are 6K/3K. It also came with an extra set of 7K/4K. It runs really nice on our local Michigan roads, but I may have to try the stiffer set (or buy even stiffer ones) next summer. The tire sizes listed in the article are also useful to know when the time comes for new rubber as the stock wheels were replaced with 17x8 Konigs. Good to know that wider fits. Thanks
I don't understand -- a properly corner-weighted car is the first essential baseline in any suspension tuning and probably 90% of the benefit of coilovers. You can put stiffer springs on the Koni's you have and re-valve them. But they don't appear to afford ride height adjustability without spring spacers (which I used on my SpecE30). But that can also be done, though it's a PITA. To attempt to sort and test a car that's out of cross-weight balance seems an exercise in frustration and futility to me. A properly corner balanced car builds driver confidence, makes the driver's job easier, and reduces lap times, arguably far more than any other suspension tuning. Arguably, the reason the car becomes so unmanageable over bumps is amplified by any cross-weight imbalances the driver is forced to contend with and have less to do with shock valving and spring rates. Granted, a loss of suspension travel in bump = infinite spring rate and loss of grip, so resolving that is critical, but even sway bar changes or adjustments can possibly address that as well.
jeffbob said:I don't understand -- a properly corner-weighted car is the first essential baseline in any suspension tuning and probably 90% of the benefit of coilovers. ...To attempt to sort and test a car that's out of cross-weight balance seems an exercise in frustration and futility to me. ... A properly corner balanced car builds driver confidence, makes the driver's job easier, and reduces lap times, arguably far more than any other suspension tuning.
This assumes that the corner weights are that far off. They aren't/weren't. I own scales...I use them.
I approach setup from a "lowest hanging fruit" approach...and the lack of suspension compression stiffness was the major problem in this case...not the corner weights.
And I strongly disagree with that bolded statement. I've successfully race engineered plenty of cars, amateur and pro. Often, there is a "knob turned to 11" that prevents every other change from having it's normal effect. Finding that knob is a pre-requisite to doing *anything* with the other knobs.
Just to give an idea of how well the new setup handles the bumps at Harris Hill, here's a video of a recent session.
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