Rear Swaybar & Soft Suspension (Spring) Testing

We have been testing a new suspension that features a component not found on the Elise or Exige.  This innovation is a rear swaybar (anti-rollbar) that was developed by our partners in Italy, DNA Racing.   This rear swaybar allowed us to test softer springs than we typically run.  We've spent several weeks testing on the road and track.  We recruited our friend and pro-Ride & Handling Engineer, David Thilenius for set-up and tuning.  Our focus was to create a fantastic handling car for the street and occasional track use.  We were focused on delivering a flat handling car with grip and compliance, especially on rough roads and tracks.  All the work was conducted on our street legal '05 Elise.

We tested the following:

• Spring rates:
  • 250lbs/350lbs
  • 350lbs/500lbs
  • 450lbs/600lbs
• Valving
  • 2 different levels
• Swaybar settings:
  • Front: 20mm bar with 5 positions
    • .78Kg/mm to 1.1Kg/mm
  • Rear: 20mm bar with 4 positions
    • .93Kg/mm to 1.235 Kg/mm

The key advantage of the rear bar is that you can run softer springs than normal.   Swaybars are used to help manage large side-to-side body movements (body roll).  Running softer springs deliver a more compliant ride and more grip.  Without a rear bar, we've had to run heavy springs in an effort to better control the car and to reduce body roll.  The downside of a rear swaybar is the added complexity and cost.   Check this reference for more details: Wikipedia

Rear swaybar with 4 adjustments.  Requires drilling one hole into the lower wishbone as shown above.

We started with 450/600 spring rates but then switched over to even softer rates than we have ever run: 350lbs front & 500lbs rear.  We completed most of our testing with Triple Adjustable dampers with our V2 valving developed by our good friend Ralph@V2 Motorsport.  This gave us a wide latitude to test.  A future blog will cover the details of the dampers and settings. 

Dave T. spent a day running our Elise on his development route through SoCal roads to dial in his tuning.  His final settings proved to be good but firm.   He also had the dampers set at almost full soft and recommended that we revalve the dampers as well as other areas to find additional compliance.   I drove the car and was impressed but wanted to take it to the West Coast Lotus Meet to really put some miles on this set-up.

The West Coast Lotus Meet trip included a several-hour freeway trip to reach the location and one EPIC canyon run that took most of the second day.  The suspension felt good and performed very well as I hung with the tour leader for hours through some great but rough canyon roads.  I knew this was a nicely balanced kit BUT it was still a bit stiffer than I wanted.  It was more comfortable than the factory Sport suspension but stiffer than the factory Standard suspension.  I wanted the best of both worlds.

We had the dampers revalved to shift the curve to deliver more comfort but kept enough to make it stiff enough for the track.  We also placed the softer 250/350 springs on to help.  Dave was recruited once again to have a go.  The advantage of a professional is that you can get excellent data fairly quickly.  It took him another day of tuning to land on a setting that struck the best balance.  I took the car out onto my favorite test canyon road and was truly impressed.  The compliance and grip were what I was hoping for.  The car turns in flat and sharply.  The soft suspension soaked up the rough roads without beating me up.  

Track testing was our next objective.  I decided to drive the car to Spring Mountain and softened the Rebound 5 more clicks to see the effect.  It was even better on our bump-strewn freeways.  SoCal has expansion joints that are notoriously bad and can make a Sport pack Lotus feel like a bucking bronco.  Our new suspension was perfectly comfortable yet still sporty and responsive.  My goal is to create a  useable sports car that you can take on trips and yet still strafe a canyon or run an occasional track day, not a boulevard cruiser.  

Spring Mtn was running the East 1.6mile course.  This is a fast and smooth course but has many curbs that you can ride that can upset a less forgiving suspension.  After stiffening rebound to Dave’s road settings, I went out to do some warm-up laps and quickly realized that the car was too soft for the track.  We decided to put the swaybar onto the stiffest settings to see if that would help the wallowly response on track.  This proved to be a disaster as the car turned in quickly but understeered horribly.  I took one lap on track and exited immediately to make a change as it was almost undrivable!  It took us another few different iterations of settings on the swaybars and the dampers to get the car to my satisfaction.  I like a neutral-handling car that maintains a nice balance.  The final setting was exactly what I liked.  

I had a couple of Lotus owners drive the car to get their feedback as well.  Steve drove the car on track and was very impressed.  He has owned an Elise for 10 years and has done at least 60 track days so is very dialed into this platform.  He also has the Ohlins TTX dampers yet was very impressed with our kit.  Watch his video testimonial: Click HERE or below.

https://www.facebook.com/inokineticgroup/videos/388429991605550/

At this point, we are ready for production parts.  We placed an order with our partner and expect to see production parts by the end of Dec or early Jan'18. 

One additional configuration that we need to test is running this rear swaybar with the factory non-adjustable bar.   I'm not overly optimistic as the torsional stiffness of the factory bar may be too light - even after drilling a new hole to increase stiffness.   We try it out this coming week... (UPDATE Edit: stock front bar works.  New Blog will be posted soon)

Evora shiftR111 Progress

The earlier S1 Evora shifter is a derivation of the '07+ Elise/Exige shifter.  As a result, it also suffers from poor feel and durability. It has the same blue plastic ball joint that has broken in Elise/Exige/211.  We are now seeing this failure in more and more Evoras, as well.  Clearly, we felt there was a real need.

We took apart an Evora shifter system to see if our shiftR111 might work.  Lotus does a nice job of integrating various requirements to really drive down the cost of a component.  This shifer housing clearly serves a few different functions.  The key was that the overall height of the shifter and the mounting points at the front would work for our shiftR111.  It appeared with a change to our hand brake brackets, we could create a shifter kit for the Evora.  So we got to work on a design.

Shown below is our design for the Evora.  We are now getting a prototype made to test fit into a car.  We remain overtly optimistic.  8^)

We have already sorted out shifter cables and our innovative ESWkit for the Evora so a shiftR111 will complete the package nicely.   

Carbon-lined Synchro Testing

2nd Gear synchro

We had our trans fitted with the new carbon-lined synchros from Synchrotech.  Our '05 Elise (ArtCar v2) was once again our trusty test mule.  I ran almost 150 miles at Spring Mountain on these synchros.  The shifting and specifically the downshifts were really crisp.  Road use was also good with no negative behavior or characteristics.

rebuilt and ready to go in

The trans has stock gears, clutch/fly and no LSD.  The car was also equipped with our new shiftR111 and SMOOTHoperator but no short-shift kit.  We debated internally whether or not to run a short shift kit and ultimately decided not to have it installed.  We knew that the 'feel' of these new synchros would be important and anything that might influence feel would be another variable.

We ran on the 3.6mile Fittipaldi course.  This configuration uses 2nd,3rd,4th &5th gears.  There are some really fast sections and plenty of slow 2nd gear corners - with a couple of them heavy breaking zones.  Proper heel and toe downshifts are critical on many of the corners so it was a good test of the synchros.

a fast course with plenty of shifting from high speeds/rpms

Overall the car shifted nicely.  The feel was immediate and frankly crisp.  The down shifts were great and even at times when I did not get enough of a blip, they seemed to engage really well.  I drove the car on the 'street' a bit around the shop and grounds of SMMR.  Again the shifting was nice and confirmed that it can work fine on street cars - with no negatives,

taking a slight breather between sessions

David@Synchrotech referred to synchros as the brakes for gears.  As it turns out, there are many manufacturers who use synchros of this type for 15+ years.  Our kit uses brass, carbon and construction that have been refined by Synchrotech over several generations - mostly in Honda applications.  This is especially important to us as the Honda run 9k rpm trans that are similar to our 8k rpm gearboxes.  Essentially, the carbon can deal with high speeds far better than just the brass - as found on our stock synchros.  David did change the design slightly from stock to improve performance and my testing confirms that these changes are acceptable.  If you compare them side by side with a stock set, you may see some differences.  Our trans rebuilder, Jeff@Transaxle, was also duly impressed with the kit.  His opinion was key as he rebuilds many, many gearboxes for Lotus Cup racers.

I believe they are suitable for road & track.  The stock brass synchros are the weak link in the Toyota gearbox so these bits will be very welcome and will extend the life of the gearboxes.  Of course, you still need to heel and toe your downshifts!  Yes, these will allow for faster shifts but we still suggest clients be smooth and gentle.

We are going to get production products and release these parts.  You can find them: HERE

Evora Clutch Delay Valve

Lotus decided to protect the transmission in the Evora S at the expense of the clutch. Just like with the S240 and S260 models (which we blogged about HERE), they fit a clutch delay valve in the hydraulic system. This valve delays the flow of fluid out of the clutch slave cylinder which more gently engages the clutch. This protects the transmission from shock loads, it also prematurely wears your clutch. 

We just pulled a clutch out of a 50k mile Evora S that was completely used up. If you look closely, you can see that the heads of the rivets are ground away; there was nothing left of this thing. It also damaged the flywheel and scored it badly enough that it also needs to be replaced. 

Delay valve shown

 Aggressive driving certainly plays a roll in the accelerated wear of a clutch, but slipping the clutch at every engagement really hurts life when combined with aggressive driving.

Our solution, the Evora CLUTCHline, is a piece of stainless steel braided line with the correct fittings that replaces the factory delay valve. 

The CLUTCHline will allow the clutch to engage as quickly as possible, preventing excessive slipping. It will also allow you to modulate the clutch in low speed situations rather than fight the delay valve. Of course if you want to do high RPM clutch dumps, you are going to put more stress on your transmission, but if you drive with some skill and care, the reliability of your transmission should not be compromised but your clutch life should be greatly extended. This is a good thing considering that a clutch replacement requires powertrain removal and takes roughly 40 hours of labor...

The lines are available on our site HERE.  It takes about 2 hrs to install it.

shiftR111 Track Testing

We brought our ArtCar v2 to SMMR and ran the 2.4mile Fangio B course. We managed to get about 100 track miles put onto her. No issues. The shiftR111 felt great. Watch the following video from inside the car showing the shiftR111 in action going up and down gears 2 through 5.

We recruited a couple of long-time Lotus owners who have run countless track miles on their Lotus cars. I wanted to get their objective opinions about our new shifter. Watch the video below:

Our next step is to confirm fitment into a stock Elise, finalize the reverse lock-out cable length and then kick off production. Yes!

shiftR111 Update: Generation 2 Prototype

Our Lotus shifter, the shiftR111, is making progress.  We are shooting for a late Jan/early Feb release for production parts.  Watch the video at the bottom of this blog entry to see it in action.

 We've installed the Generation 2 design into our Elise (ArtCar v2) and have conducted some basic street testing.  This second design is simpler and less costly than our first design.  The image below shows them side by side vs stock.  We learned a great deal from the Gen 1 and applied it to making the Gen 2 even better.

We're still employing the same basic mechanism as the first gen design but have taken out several machined pieces.  One area that was simplified was the reverse lockout mechanism.  Our Gen 1 used several machined parts that we ultimately deemed unnecessary.  In fact, we also chose to reuse the factory reverse collar in the Gen2.  We still need to spec in the final cable length to validate the operation but that will be quite simple - compared to most everything else!

Additionally this new design allows the factory center console to fit completely.  We know that some clients would prefer to keep their cars looking stock.  But we also know that many clients would like to have our shiftR111 exposed.  We will be designing a simple bracket that will hold the Emergency Flasher, Lock and TC buttons.

The shifter feels nice and smooth with throws that are similar to stock.  The LETSLA kit we installed on the Gen 1 version allowed us to shorten the distance to our preferred throw.  We will install it into this Gen 2 after we have completed our track testing.  Street testing has been great as the shifting is predictable and smooth.  Heel and toe downshifts have been great.

We head to the track later this week to start testing.  I'll recruit some Lotus owners to drive her as well to add to our findings.

The finishes shown do not represent the final product.  Most of the sheet metal pieces will be black and other machined parts will be hard anodized or left as raw stainless steel.  We are shooting for a technical look that is not to bling-bling.  We'll make sure it looks properly cool.

Watch the video below:

Tech Tip: Torque Your Dang Wheels - Carefully!

Keeping your wheels attached to your car is critically important. The most obvious opening statement for a blog post ever, I know. However, I do believe that familiarity breeds contempt and the little studs (or bolts) that hold your wheels to your ride do not get enough respect. The torque spec that your manufacture recommends is actually pretty important when it comes to wheel bolts and studs. There are times where "good and tight" is acceptable, your wheels are not one of those times.

As discussed all across the internet (including in this BLOG), and in fine books and pamphlets all over, fastener torque is critical to the strength of any joint. Also, the torque applied to a bolt is not the critical bit. What is critical is the amount a bolt is stretched (stained) when it is installed (ever wonder why rod bolts in an engine are not just torqued, but measured?). A torque value is just a handy way to measure and apply a set amount of strain. The torque value for a fastener is calculated by estimating things like the friction factor between the fastener and its mating part, or experimentally where strain is measured for a specific application and the torque required is noted.
When working on cars here, we often see studs that have obviously not been properly torqued. Usually this means they are WAY too tight and this happens for 3 main reasons:

1. Use of an impact gun
2. Torquing hot wheels
3. Stud lubrication

Leave this tool in your box
when working on your sports car.

1. Impact Gun 
The first most common mistake is that people put wheels on with an impact gun, this crime is committed most often (oddly enough) by wheel/tire shops. You would think that people that specialize in putting wheels on cars would do the task correctly, but they do not. It is such common practice to just buzz the lug nuts/studs/whatever on that no one bats an eye. If you are using an impact gun, how do you know that the torque is correct? Too much torque puts too much strain on the stud and the wheel itself, worst case, the stud snaps. Too little torque actually puts too much strain on the stud as well and severely lowers its fatigue life. Worst case, stud snaps. Nothing good has ever happened after a wheel stud failure. We NEVER use an impact to install wheels here. We also never use one to remove wheels either. Using an impact is hard on the wheel lugs/nuts and doing it by hand with a breaker bar allows you to feel if something is not right (over/under torqued, bad threads, etc.)

2. Torquing Hot Wheels
The second most common offense? The habit of torquing wheels right after a track session. In this scenario, the wheel studs and everything else associated with the hub are pretty hot, hot enough to change the strain in the system. So sometimes you can turn the bolt a little bit farther with the same amount of torque. You have now tightened the bolt further than you did initially (when it was cold), and now when everything cools back down, the bolt is strained more that originally intended. We think that this is minor but we still never recommend torquing hot wheels.

For peace of mind, you can check for loose bolts but wait till the wheels have cooled before checking torque.  Do it just before your session starts.

3. Stud Lubrication
The third reason why wheel bolts get over torqued is lubrication of wheel studs. As mentioned early, the torque applied to a threaded fastener is meant to produce an ideal amount of pre-stress or strain in the fastener. Most of the force (torque) applied to a fastener (about 90%) while you were tightening it is not stretching the bolt, it is overcoming the friction between the two mating threads as well as the friction generated under the head of the bolt. So then the amount of friction between the parts is critical in determining the correct torque to produce a given strain. The friction can vary wildly depending on the bolt plating, thread class, materials, and lubrication. Most torque values given by manufactures are for dry threads unless stated otherwise. So if you have a torque spec for a dry thread, then you lube it with something like anti-seize or thread locker, you are going to reduce the friction and you will end up with much more strain in the fastener for the same amount of torque applied. If a fastener does not call for lubrication, it is usually best not to lube it.

So if all these mistakes are being made and people are over torquing the hell out of wheels all the time, why aren't wheels flying off cars and people dying in fiery crashes 24/7? Safety factors. Engineers always design things with a safety factor and make things able to withstand loads usually 2-10 times higher than what is expected (air craft and race car engineers usually use safety factors under 2 to reduce weight). This covers things like over torquing, misuses, accidents, etc. However, the wise (wo)man respects the safety factor she is given and does not try to push his luck. Wheel studs CAN and DO fail from improper torque.

We Recommend:
1)Torque your studs/bolts/lug nuts with a torque wrench and according to the manufacture's specifications.
2)Tighten your lug nuts in a criss-cross or star pattern for even torque with a torque wrench
3)Check your wheel torque at least twice a day at the track - when the wheels are cold.  We like to check before every session.
4)Use a torque wrench (was repetitive enough?)

Tech Tip: Suspension Bump Stops Will Degrade!

The bump stops are an overlooked and underappreciated piece of the suspension system. Some people look at the bump stops as a nuisance because they lowered their car and now it is the bump stop's fault that they do not have as much suspension travel as before. The fact of the matter is that the primary purpose of a bump stop is to prevent suspension or chassis damage when you do run out of available travel. The secondary purpose of the bumpstop is to provide a progressive transition between your normal spring rate to the fully bottomed condition.

Standard bump stop on a
Nitron 40mm Single Adjustable Shock

The bump stop prevents damage by absorbing and dissipating a huge amount of force when your suspension bottoms out. If the bump stop was not present, a large (and harsh) impact force would be transferred into the chassis and into the lower suspension arm. In this scenario, the chassis and/or the a-arm can be damaged.  In other words, not good. You can have a bottom out condition without damage but it is still highly stressful to all the components and passengers involved.

The second, and more subtle job of the bump stop is to be progressive. When the car is normally going around a track, the suspension is working with what ever spring rate you are running (resulting in some wheel rate). When you run out of travel and fully collapse a shock with no bump stop, your spring rate (and therefore wheel rate) goes to infinity. Infinity is a very high spring rate indeed and is the least compliant you can get. Tires do not like to stick to the ground when there is no compliance. This situation does nothing good for handling. When a bump stop is in place, rather than an immediate spring rate to infinity transition; there will be a progressive ramping up of the spring rate. This is much more forgiving on the suspension and chassis and results in much more predictable handling.

Bump stops do wear out over time. The life is going to be determined mainly by the environment in which they live. Severe weather and track use will accelerate degradation and wear. Miles are pretty much irrelevant unless your car is "stanced bro" and you are riding on the bumpstops constantly. Evidence of this can be seen on a car we currently have in the shop. It is a 2006 Lotus Elise with 14,000 miles on it. Luckily this customer is getting a nice set of Nitron 40mm Single Adjustable Dampers to replace these tired units.

This is not an effective bump stop...

These stops crumble when touched, they will do nothing to help the vehicle and must go. If your bump stops look like this, get them replaced. You can send your stock shocks to Bilstein to be rebuilt or get an UPGRADE.

Struggles of Design: Alfa Harness Bar

We developed our 4Corsa Harness Bar for the Alfa 4C knowing that people would like to track these cars.  This blog entry discusses our harnessbar development process, a mistake we discovered AFTER we had began production and the solution that we came up to fix it.  We are happy with the final product but it took some extra effort to finally get it 100% right.

Brainstorming A Solution
Getting a bar into the Alfa presented some challenges as the chassis and seats did not give us much latitude.  We've designed harnessbars for over 10yrs for Lotus Elise/Evora and Mini Coopers.  Some of our design requirements for the 4C included:  be economical, 100% reversible, require minimal modification, and most importantly, be safe. Safe means it must be strong AND correctly position the shoulder belts.  Solutions we've seen in various cars, including the 4C, position shoulder belts too high.  After MUCH head scratching and going through a number of concepts, we landed on the one you see for sale today.  We hit our targets for safety and reversibility. 

Joe (our engineer) earning his paycheck.

Measurements were taken inside the car, a rough 3D model was made, and a prototype was fabricated. Making a one off piece is actually relatively easy. However, we needed to take this part and make an accurate 3D model for our fabrication vendor so they could make a batch of bars. We took measurements from this bar and had some tubes laser notched, they were off a bit, so we had some more tubes laser notched, these were correct. We basically remade our prototype with these laser notched tubes (the originals were notched by hand) to verify the design. It fit so we kicked off production.

Prototype bar in place. It fit our car!

Fitment Problem
Great! Right? Well, when dealing with these low volume cars, sometimes it is difficult to get your hands on a single car for testing, much less multiple cars. Before production, we identified a potential issue. We assumed there would be some variation in the distance between the seat belt mounting points that the bar bolts to. We did some estimation that the variation would be 1/8" or less which the bar was designed to deal with.  We were wrong.  After we started selling our bar, we found out we were wrong. It turns out the variation from car to car is more. This may be due to the introduction of a new model called the 4C Spider - though we are not sure.  Regardless, small volume cars generally have much more car to car variability and that must be considered in the design of any hard parts.

Problem Resolution
 We needed to get creative again and come up with a solution to take up the car to car variation. Our current bar fit some Coupes but not Spiders (2 so far). Most cars have 'slip joints' to take up build tolerances.  This gave us an idea.  We decided that the best way to allow the bar to accommodate the width variation is to allow it to telescope.  We brainstormed several different approaches to make this happen and finally landed on a solution.  Obviously safety was critical and we are happy that it is probably now even stronger than before.

TSSJ Technology
Our solution is a slug and sleeve arrangement to give the bar some telescope ability in the width direction. We cut the bar in half, insert and bond a slug inside the tube and slid a sleeve over the top. This sleeve is also bonded to one side of the 4Corsa.  The other side of the 4Corsa bar slides into this joint.  This arrangement is total overkill. The slug in the center is a piece solid steel round bar and the sleeve, being bigger than the tube it is covering, is even stronger. The both of these parts combine make sure that the bar is not any weaker than the original design.  We came up with the acronym, TSSJ (Telescopic Slug Sleeve Joint) because necessity is the mother of all invention and why shouldn't we have some fun at the same time?!

TSSJ Technology:
Section view of slug and sleeve retrofit.
Slug is red, sleeve is blue, original tube is grey.

Though we had considered adding additional adjust ability, earlier in our development, we ended up tabling it.  In hindsight this proved to be a mistake.  Ultimately our TSSJ solution makes our bar a product that will work on both models and offer a degree of adjustment that a small volume car truly needs.