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.

Switchblade Track test at SMMR

I took our Exige S to the track to do some initial testing.  We have several items on the car that needed to be evaluated, including the new clutch and suspension.  It was the first time in years for me to drive an Exige S on track and it was interesting difference compared to the Elises that we have had the last few years.  The car performed well and had some good points and some bad ones.  I ran her on SMMR's 1.5 mile configuration.

The Exige was very fast as we installed our BLADE275 kit on it.  This car accelerates like a scalded cat!  The auxiliary ducting kept the proICduct well fed with air so it did not feel as heat soaked as with the stock set-up.  The ambient temps were well into the mid to high 90s during my testing.  Water temps stayed below 203degF.

 The new clutch felt great.  During the initial break-in the car was a bit touchy when you launched it from a stop on the street in 1st gear.  I'm embarrassed to admit that I stalled her a couple of times!  The clutch now has approx 500 street miles and feels fine.  The pedal effort is slightly higher than stock but the power rating is much higher so I think it will be a very good option for clients with more power and who run on track.

The suspension is very soft and glides over the bumps very well.  It had great grip.  The car swayed much more than our last couple of Elises thanks to these softer spring rates but you could also feel the weight up high on the Exige.  The IC coupled with the roof, hatch/wing make for a car that feels more 'top heavy' than the Elise.  You really notice it on the track.  The 'inch down' ETHOS wheels and larger sidewall Toyo RA1s also contributed to the compliance and slightly slower turn-in.  The car was very fun and easy to place.  We still have the stock seats and no harnesses and I moved around quite a bit as a result.  We'll add some harnesses soon.

The single biggest negative was the 'ice-mode' issue that I was experiencing on a couple of turns.  This is a known issue with the ABS system on the Lotus.  I ran with the ABS on but many racers defeat it as it can cause this disconcerting feel of having no brakes.  Truth is, the ABS system thinks you are slipping so kills any additional rear brake pressure but your front brakes are still working.  If you get off the pedal and immediately back on, it corrects itself.  Of course that is never fun when your corner is quickly approaching!  We were running stock pads with our ULTRAdiscs so the initial bite was also a bit lacking thanks to the pads.  Different pads will make a huge difference.  We were testing a new brake fluid and it appeared to work fine as it is hard to boil fresh fluid in a Lotus.

I also had some shifting problems.  I think our cable adjustments need to be looked at but I was mostly having some shifting issues on the track.  Again it is well known that the 2ZZGE moves quite a bit with track use - especially with the addition of an IC on top.  We installed our sportINSERTS to help this issue.  I need to look closer at our adjustments to see if that was the cause or if we need to run stiffer mounts.

I drove the car to the track to see how comfortable it would be.  The TRACKpipe sounded great on track but was a little bit intrusive while cruising along the freeway.  The Exige is a louder car than an Elise.  Mufflers that do not drone, like the TRACKpipe, in an Elise, will be louder in an Exige.  I think the rear fastback clam of an Exige creates a bit of an echo chamber that causes it to be louder.

The day I arrived, a SMMR member took delivery of his new Spec:Race Atom.  He will be running it in our Winter Race Series.  Barry got one session in the car and we made a quick video of his initial impressions.

Nitron Build - Saving Unsprung Weight

We're almost finished with the installation of Nitron's tasty new bits on Michael's Cup car. After weighing both the stock parts and the new Nitron bits we found that there are significant weight savings to be had with Nitron's uprights. Over 10 lbs of unsprung weight were shed with the full set of four uprights.

OE Front Uprights (pair)=24.4 lbs vs. Nitron=17.3 lbs

OE Rear Uprights (pair)=23.8 lbs vs. Nitron=20.1 lbs

We'll publish more weight saving details later!

V2mounts - Secure & Safe

I have never been very happy with the mounting options for remote reservoirs on our Lotus. Most suspension companies provide zip ties or band clamps and leave you to find creative places to mount your canisters. The typical place to mount the canisters is the lower a-arms. Though this works, getting the reservoirs tight enough so they don't move during adjustment is tough. Plus they are located in an area that feels vulnerable to road debris. Ralph@V2 came up with a creative solution and sent me a couple to test out.

We installed them on Nirvana last month and ran it at Laguna Seca. Since I only had 2 brackets, I mounted them on the front under the chassis by riveting them. This resulted in a super stiff solution. Reaching in to adjust them was a

snap. We left the rear canisters mounted on the a-arms without the brackets. These remained much less secure as they would move slightly during compression adjustment. On some reservoirs the adjustment is very subtle and any movement can cause you to miss a 'click'. My other concern is adding additional weight to the suspension arms - it is clearly the wrong place.

We decided to order a small batch and assemble a kit we are calling V2mounts. The rear mounts can be installed in a few different locations:

1. Rear triangulation tube
2. Rear toe links
3. Lower a-arms

We like the Rear Triangulation Tube that extends down from the Roll Bar. On the Exige, this is an easily accessible part of the car. Ralph has mounted them here with sweet success. On the Elise it is a bit of a challenge. We've mounted them here BUT upside down on Nirvana. I will run it this way for some time to see how it works. Since most of us don't mess with compression adjustments on

every track outing, this should be less of an issue. Of course the engine will be hot so you have to watch your hands and arms...

I will be using them on my Atom as well to secure my Nitrons. I suspect they may work well on other performance cars.

Trackday at Big Willow

Spent the day at Willow Springs racetrack yesterday - testing and celebrating Jack's 60th B-day! His wife rented the track for Jack and bunch of his friends. I brought out the Exige to drive, Willow is one of the higher speed tracks in Southern CA. The car ran well as I acclimated myself to the track - it had been a couple of yrs since I was there last. The Exige has the following ReVerie aero parts: front spoiler , 5-element diffuser , Side Sills and 1650mm Rear wing. The Exige also has the Nitron Sport Pro and is running 120mm/125mm ride heights.

The front spoiler creates a truely flat bottom car - the stock Exige is not flat immediately behind the stock front spoiler. The ReVerie spoiler creates a smooth flat area to keep air running fast and smooth to the undertray and rear diffuser. The ReVerie sills also work to keep air from tumbling up the sides of the car. The Rear Wing is the largest we sell and makes the most downforce. This set-up provided a very comfortable balance to me. Some of the high speed understeer that I experienced on Buttonwillow was reduced by lowering the Angle of Attack on the rear wing.

With a prodriver (Craig Stanton), our Exige was able to go flat out from corners 5 until the braking zone for 9! No lifting at all - he is an amazingly smooth and fast driver! He really loves these cars as he was clearly having good time with our Exige. He especially likes the ReVerie XC seat!

Our Exige has the Katana with a base level of tune. This track is not heavy on the brakes and the AP Racing kit was deemed almost too good. Craig also noted that the suspension could now use heavier springs beacuse of the massive downforce. We have the new Nitron Exige GT3 kit ready to install.

All in all it was great day as the weather was also perfect. Thx to Jack's wife Nikki for arranging a great time for us all! Did I mention Alex VanHalen was in attendance - he was very fast in his race-prepped BMW! He is a very cool and a true car guy.