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We've been kicking around the idea of doing a new front upright(also called a knuckle) for almost 15 years! About 3 years ago we started in earnest to design our own Ultimate Upright.
There are several reasons to improve upon the stock design. To see details go to the "Extended Information" tab.
1. Suspension Geometry improvement.
2. Strength & Weight
3. Wheel selection
4. Braking improvement
The BWR design features:
- Highest FoS(Factor of Safety) design available even compared to stock uprights!
- 2lbs lighter than stock uprights!
- Made from Aircraft Grade 7075-T7351 NOT 7075-T6 because of it is far less susceptible to corrosion cracking
- Uses thread inserts AND ball joint taper insert(all stainless steel) for toughest, robust design.
- Wide brake caliper selection available.
- Allows ride heights from stock all the way down to 90mm
- Reduces roll-center migration by 1/2.
- Reduces excessive camber gain to keep the effective camber while cornering in a more optimum window.
- With stock steering arms you can get -3 degrees front camber at 110mm ride height.
- Fit most 15" wheels on the front
These ideas have been designed in software, tested on the track, and proven with Wins and Championships.
Suspension Geometry Improvement.Back in 2006 when I started building what would become our 10 time championship-winning X-Prepared Car, we discovered the front suspension geometry gets wonky when the car is lowered much below stock ride height. The roll-centers drop below ground causing the car to NOT turn. Back then, the fix was to hack on the stock uprights and use some custom ball joints. This has been iterated on over the years.Some other uprights on the market simply shift the hub-center up, which effectively keeps the same lotus geometry at a lower ride height. In our case, we changed the geometry to improve upon the original design.The BWR design:- Allows ride heights from stock all the way down to 90mm
- Reduces roll-center migration by 1/2.
- Reduces excessive camber gain to keep the effective camber while cornering in a more optimum window.
- With stock steering arms you can get -3 degrees front camber at 110mm ride height.
These ideas have been designed in software, tested on the track, and proven with Wins and Championships.Strength and Weight:Lotus used forged steel for the uprights for cost and strength, certainly not weight. When we started this process we spent a ton of time on material selection. 6061 aluminum is excellent, but not strong enough to meet our weight reduction targets and achieve our desired factors of safety. We needed more strength without a weight penalty. his took us to Aircraft Grade 7075 aluminum. You see 7075-T6 thrown around a lot in aftermarket auto applications. It is very strong, but has a key weakness. 7075-T6 is susceptible to stress corrosion cracking (SCC). This means that cracks propagate at an increased rate in the presence of corrosion. This is why you won’t see 7075-T6 used by an OEM in any automotive application outside of the cabin.We chose to use Aluminum, but the more expensive 7075-T7351. This material retains the high strength compared to 6061, performs well in cyclic fatigue conditions and is significantly less susceptible to stress corrosion cracking vs 7075-T6. It is the right aluminum alloy for the job.We weren't terribly concerned about weight. If we could be lighter than stock, great, but we wanted the robustness to be as good as stock or better.Over the last couple of YEARs we've done 14 unique versions with multiple tweaks within each design. We've looked at Finite Element analysis of stresses and even modelled fastener strength. Ultimately we are as light as the lightest uprights available BUT far stronger, with higher factor of safety(FOS) even compared to the stock upright! FOS 1 or higher is deemed acceptable. Obviously the higher the better.
Fastening:Unlike some other aftermarket options, all of our threaded sections have helicoil inserts for strength. The taper for the lower ball is machined 17-4 PH stainless insert heat treated to H1150 condition. This provides excellent strength and elongation to break, along with good corrosion resistance. Thus the ball joint taper will retain its shape after many years of use. Was this all strictly necessary? Maybe not to some, but we wanted the Ultimate Upright!
Finish:Some manufacturers tout the benefits of hard anodizing. Hard anodize is a really tough finish and it has its place. However, it does have an issue with micro cracking which can cause corrosion issues. We're using regular anodize which provides oxidation protection with no microcracking downside.
Wheel selection:Wheel selection and tire sizing is very interesting on these cars. Essentially, the rears use a ~ 24.7" tire and the fronts use a ~ 23" tire. Generally tires are either ~23" or ~25" diameter. You don't see 24" tires. For our purposes we'll call them small tire and big tire. Also you will find Lots of 17" tires sizes and lots of 15" tire sizes, but 16" is an odd duck.We learned a long time ago that downsizing the front wheel to a 15" has many benefits to tire selection. 23" tall x 15" tires can be had in 205, 225, and now some 245 street tires. In Hoosiers you can get 205,225,245,275, and even 295! wide front tires!The trick with 15" wheels is getting the brakes and steering to clear the rim barrel. If you simply shift the hub centers upward you can crash the lower ball joint into the wheel you were planning to run!We designed our Ultimate upright from the beginning to work with 15" wheels. You don't have to run 15" wheels, 16s work fine, but you CAN run 15" wheels. We've modelled 6UL, TD, and a few others.
Braking:To start with, the stock NA Elise and 2006 Exiges have perfectly adequate brakes for the stock 190HP. Braking demand has everything to do with Max vs Min speed, frequency of application, and cooling.The bias of the brakes is a bit too high to the front. As many of you know we've helped people use the staggered pad setup to increase rear bias. Lotus put "Cup Brakes" on some Exiges with bigger 308mm discs and 4 pistons fronts. This makes the front bias even worse!!!! Additionally, the 308mm discs are very expensive and make it difficult to run 15" front wheels. Stillen did a Brembo BBK that eliminates 15" brakes completely. By and large the whole Big Brake Kit(BBK) thing is just a wallet flush. More on that later.We've learned some hard fought lessons over the years on braking, especially on the Optima Ultimate street car. Alex was the driver of that car and complained about losing the brakes. To my shame, I thought it was in her head until I almost drove the car out the front of the trailer when loading it the first time. How she drove around my idiocy, I'll never know.Our cars now have more power than stock so they generate higher Vmax. Many folks track on street tires(like optima/NASA etc). The lower grip of the street tires reduces cornering speed vs race tires. So the delta between Vmax and Vmin is much higher and thus braking demand is also much higher. Thus we were boiling fluid. We put in in our Stainless pistons which helped and we ran the best brake fluid on the planet, Castrol SRF(yes Motul fanboys, it is better than Motul). SRF is $75 a quart and comes in a gold bottle for a reason. We boiled that.Upon analysis, we weren't warping rotors, we weren't cooking the pads(CL pads are good to 1200F), we just had too small a pad to absorb and dissipate the heat and thus cooked the fluid. The answer is to do a larger pad in the front and thus a real need for a big brake kit. HOWEVER, we don't want to make the front bias worse. We want to retain the 288mm disc as it is perfectly good enough, lower rotational mass, and lots of aftermarket 2 piece options. Our offering will be scalable with 4 piston fronts to work with stock rears that provide more rear bias, but those fronts can be moved to the rear later with different fronts for more total braking if desired. More on that later, just know that we have you higher HP folks covered with a bulletproof, cost-effective brake upgrade coming shortly. These uprights are designed to handle the stock AP 2 piston, the Cup 4 piston, and our new offering.
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Features
- -Improved Geometry for lowered cars
-2lbs lighter than stock uprights
-Designed to be stronger than stock steel forging.
-Stainless steel inserts
-7075-T7351 aerospace aluminum to resist corrosion cracking
-fits most 15" wheels
-More brake options
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