Tag Archives: Seven

Setting up a Seven – Wheels and Tires

My new WCM Ultralite S2K

When I initially purchased the Ultralite it was running on a set of generic 7.5″ wide alloys with 235-width Falken Azeni RT-615 tires all around(above). While the Azenis are decent tires (we use them on the Lemons car), they are still street tires and just cannot cope with the absurd power of the seven. After having a few moments of wheelspin in 3rd gear, I decided that while long slides are fun, I did want to go to more grippy setup as well as increase the rear grip level to give the car some better balance.

I quickly learned that one of the more annoying things about having a kit car is the extreme amount of pain you have to go through to get a set of wheels. While most kit cars use off the shelf components from production cars for their hubs, they generally also use parts off different cars front to rear and have very different offsets anyway. In the case of the Ultralite it uses 5×100 bolt pattern with with the most common wheel sizes being a 17×8 fronts (offset 35-38) and 17×9/10 rear (45×48 offset). Now the unfortunate part is that while the specifications themselves are fairly common (Subaru WRX), I could not find a single large scale wheel maker that makes both sizes (8″ and 10 “) in the same wheel design. I should also add that 99% of the online sites out there only allow you to sear for wheels by car model and not by wheel specs which made the tire search extremely frustrating.

The only viable option that I found were the Team Dynamics Pro Race 1.2 wheels that are used by a few other Ultralite owners out there. They are an afforable option and by all accounts stand up well to regular track use. Unfortunately because they are a fairly small operation out of England, the US importers have quite a limited stock of wheels which meant that I would have to special order the wheels and that could take anywhere from 2-6 months to get here.

At this point I happened to take my wheels off only to find that one of the wheel studs on the left front wheel was loose. I gently unscrewed the stud by hand only to find a large amount of aluminium shavings in the stud threads. It appeared that at some point in the past, a previous owner waaaay overtightened the lug nuts on the wheel and literally stripped the stud out of the hub. Additionally a couple of the studs were at a slight angle from horizontal which along with the stripping meant that the hub damage was too extensive to repair.

I contacted Brian Andersen at World Class Motorsports to get a part number for the hub only to find that the hub was actually a custom part that WCM modified before they put it on the car. They took a stock Wilwood Pinto hub with an existing 5×114 and 5×120 bolt pattern and machined a set of 5×100 pattern holes to which they added the wheel studs. This was probably done such that the bolt pattern on the front wheels would match the stock Subaru 5×100 pattern on the rear hubs. Unfortunately this also meant that if I bought a new hub I would would have to find someone to custom drill the new pattern into place for me. At this point I had the sudden brainwave that since the existing hub was mechanically sound (only the 5×100 stud openings were damaged) and still had other bolt patterns, I could just switch to a different bolt pattern and keep using the same hub. Luckily I had delayed placing an order for the Team Dynamics wheels which meant that I could just buy the front wheels with new bolt pattern without any wheel fitment issues. I went ahead and got a couple of multi-drilled rotor hats (existing ones were 5×100 only) with some ARP studs and quickly changed the front wheels to a 5×114 bolt pattern which allowed me to reuse the existing hubs and gave me access to a wider selection of front wheel options.

At this point I decided that I could not wait the 2-6 months for the Team Dynamics wheels and instead began investigating other wheel options. I came across the Wheeldude.com folks who had a good selection of Rota wheels and had the added benefit of being local (Fremont). While looking through their website I found that while they did not have any one line of wheels that would fit both my front and rear wheel requirements, they did have a number of different wheel lines that looked similar enough that you wouldn’t really notice the difference. After going through several different options, I decided that setup of G-force fronts and DPT rears would likely be my best bet. I then went over to their warehouse and got to see a couple of the actual wheels and compare them side-by-side before picking a set of 5×114 17×8 G-forces for the front and dual drilled 5×100/114 17×9 DPTs for the rear ($750 for the full set). An additional benefit of getting the DPTs for the rear is that I can in future move to the upgraded WRX STI rear end (5×114 hubs) and continue using the same wheel set.

The next step was to figure out the tires to use and it was a pretty easy decision to go for an R-compound tire. Sure I would have no grip in the rain or in sub-zero conditions but the chances of encountering either condition in a roofless, door-less, windshield-less car in California are pretty low :). Additionally I had been using Toyo RA-1 tires on my Elise for the last year and was very impressed with not only their grip but also how they do not have any heat-cycling issues (important on a lightweight car like the Seven). Unfortunately Toyo has discontinued making the RA-1 and though they are planning to restart production for 2010 there were no estimate for when the tires would actually reach dealers.

Since my preferred option was not available I had to decide between the Yoko AO48, Nitto NT01 and the Toyo R888s. Both the AO48 and the R888 tires are pretty common in the Elise community and from all the feedback I was hearing they appear to be good tires with a high peak grip but are prone to getting greasy after several laps and also heat cycle before they run out of tread depth. The RA-1s in comparison have a slightly lower peak grip but instead will maintain the same level of grip after several laps and can be used all the way to the cords without any heat cycling out. Since I will only be using the Seven for recreational driving and non-competition events, peak grip isn’t an issue and with the light weight (1300 lbs), heat cycling resistance is much more important than tire wear. Looking further into the Nitto NT01 option, I was surprised to find that Nitto was actually a subsidiary of Toyo and the NT01 apparently uses the same rubber compound as the discontinued RA1. A little more investigation showed that Discount Tire Direct would sell me a a set of 4 tires for ~$725 shipped which also made them the cheapest option by far :D

So in the end after about 2 months of searching and modifying the bolt pattern I ended up with 235/40ZR-17 Nitto NT01s on 17×8 Rota G-Forces up front with 275/40ZR-17 Nitto NT01s on 17×9 Rota DPTs on the back. As you can see from the pictures below, the wheels actually match quite well and people don’t realize that they are different front to rear until I explicitly point it out.

So far I have only used the car for street events and one truncated track day at Laguna Seca but even in this short span I have to say that the wheel combo is very well balanced and it now takes some intentional provacation before the rear wheels start spinning. In terms of absolute grip I was able to easily pull 1.2 G at Laguna despite having a lot suspension issues and not pushing very hard. Once I get the setup sorted out and start really pushing the car I expect that the G meter will be reading quite a bit higher. I should also add that I have been running the tires at about 15 psi hot all around which seems to work pretty well. Tire pressure only goes up by about 2-3 psi during a track session which may not sound like much on a regular car but its a 20% increase when you start at such low pressures.

Setting up a Seven – Safety

As you can see from the picture above, when I got the Ultralite it came with a simple asymmetrical rollbar that was barely taller than my head. While most track clubs would let me drive the car as is, the lack of side impact protection meant that I was not comfortable tracking the car without a full roll cage. Additionally the existing Ultrashield race seat had no head and neck support and the harnesses were long expired which meant I generally had to perform a full safety upgrade before tracking the car. For this I turned to Tony at TC Design who is the Bay Area’s premier roll cage fabricator.

Roll Cage
After looking at some of the existing cage designs for the Ultralite we decided to go for a design that had single high rear hoop and two side impact bars on each side.

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The two side impact bars tie into the existing chassis hoop that holds the dash in place before the top bar extends further up to the main chassis rails.

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Additionally they welded in a new square tube section within the chassis to act as a load path for the upper impact bar.

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The next step is to paint the cage and add some SFI spec padding for extra protection in an impact.

Race Seat
The biggest difficulty in putting a race seat into a Seven is usually the severe lack of space. Surprisingly my biggest problem with the existing seat was actually the fact that it was too big for me. I was getting thrown around between the two rib cage supports and the supports also interfered with my left elbow while making large steering inputs. Additionally the seat was completely lacking in lumbar support and even though I tried putting in some additional padding in various positions I would invariably end up with some back pain if i drove it for over an hour. My initial plan was to go with a custom Kirkey seat with full HALO support but after the back pain issues I decided to put in a composite seat instead. Composite seats are generally a lot more comfortable (I’ve done 4+ hour stints in the Lemon) and they have a one-size fits all approach which means you don’t have to screw around with measurements for every specification.

OMP Pista

After deciding on the composite seat, I pulled the existing seat out of the car to measure the width of the cockpit to see how much internal room I would have. The 18.5 inch width, along with my HALO requirement meant that there were very few seats I could actually consider. The two main seats I narrowed it down to were the Sparco Circuit Pro and the OMP Pista. Both are FIA homologated with full Halo support and were narrow enough to fit in the car. I then contacted Wine Country Motorsports to see if I could try out the OMP Pista before purchasing it. Mike @ Wine Country was fantastic to deal with and was happy to help me not only try out the seat but also to test fit in the Seven to make sure the measurements would fit. After trying it out I found that it was a snug fit (I likely wouldn’t have fit in it 2 years ago) but was very comfortable and holes in the HALO support afforded excellent visibility as well. After buying the seat I took it back to TC Design to have them fabricate the necessary mounts and fit it in the car.

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The seat is now mounted using 4 bolts going through the car floor and attached using large size backing washers. Also it may not be visible from the pictures but the left edge of seat us actually under the chassis tube – this is literally the largest possible seat you could fit into the car without modifying the transmission tunnel.

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Point to note is that the cage had to be modified so that the side impact bars would clear the halo wings of the drivers seat. It did not have to flare on the passenger side since I do not plan on fitting in a HALO seat and there is no room to fit one in either (passenger area is 2 inches narrower than the drivers side). The other unfortunate side effect is that my legs are now slightly higher in the car which means that my knees interfere with the stock steering wheel. I removed the seat bottom padding to drop myself lower into the car seat but still had to move to a smaller steering wheel to get the full range of motion. While the smaller wheel is ok at speed, it does make driving a lot more physical at low speed and in hard turns (T11 at Laguna is tough).

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Racing Harnesses
Since the harnesses in the car had expired several years ago (SFI belts expire in 2 years) , I had to get a new set of harnesses. Having used a several different belts over the years I decided to go for the Scroth Profi II 6-point belts since I find their adjustment system to be the fastest and easiest to use. The other feature I like the way the lap belts can be configured to pull-up tightening which allows you to strap yourself in tighter without any outside help. The final step was to add a set of arm-restraints though I will likely use them only on track days and not on the street (I use my helmet and R3 on the street)

Conclusion
All in all it was a pretty expensive and slow process to go through all the safety upgrades but it is a one-time thing and should now last me for several years. I have to give a huge thanks to TC Design for doing a fantastic job with the full safety setup and also squeezing me into their busy schedule. Thanks also to Wine Country Motorsports for letting me try out the seat before actually buying it.

You can see more pictures of the cage and seat installation at in my Flickr set. Click here for the rest of my “Setting up a Seven” series.

Setting up a Seven – The Ultralite Experience

My new WCM Ultralite S2K

As many of you know I purchased a Lotus Seven replica called the WCM Ultralite S2K late last year to make it a street legal track toy. While the Ultralite may maintain the spirit of the original Seven, as you can see below, it has a distinctly different shape and has generally larger dimensions to accommodate drivers of all sizes. In order to move this extra bulk (relatively speaking) around it comes with the incredible F20C engine out of the Honda S2000. The end product has some astonishing performance figures:

Weight: 1300 lbs
Horsepower: 240 bhp
Redline: 9000 rpm
Power to weight ratio: 400+ hp/ton
0-60 mph: 3.5 seconds

With the (more) original predecessor

My particular car was the first prototype built by World Class Motorsports and is the actual car used in most of the magazine tests. The original owner of the car then sold it to an active PCA member who took fantastic care of the car and documented his changes. He also had the car made street legal under the California SB100 exemption for kit cars. After a few years he ended up selling it and the car went through 2 other owners before I found out that it was on sale again and jumped at the chance.

The previous owner of the Ultralite going through the corkscrew

The first and most immediate thing that hits you when driving the Ultralite is sheer mind-blowing acceleration. When I bought the car it was on a set of fairly old 235 width Falken Azenis. Now while the Azenins are actually pretty good tires for autocross, they have nowhere near enough grip for the ridiculous horsepower of the Ultralite. The very first time I tried a hard acceleration run I spun the rear wheels in 3rd gear and got a full on fishtail moment at 60+ mph. This is the only car I have driven where you have to rev match on upshifts or the rear wheels will happily lose traction :D Even within the same gear the acceleration is phenomenal. The car pulls pretty strongly below 6k rpm but once you go above the 6k threshold the VTEC cuts in an it feels like someone has hit the fast forward button. Plus with the 9k redline you have plenty of time in the powerband and dont have to keep rowing the gears. Also despite the fearsome power, I do have to say that the Ultralite is actually a very benign handling car. The rear gives you plenty of notice before it steps out and you can easily use the throttle to play with oversteer through the bends (see opposite lock below :)).

Driving the Seven is very visceral experience where you can see, feel and hear every mechanical thing on the car. While you are “one with the road” it is a very different experience than what you feel in a Lotus Elise. The Elise is delicate, nimble car and will eagerly follow your every command while the Ultralite is like a raging bull that you have to manhandle into position before you step on the throttle and hold on for dear life. It is very much of a “mans car” where the controls are very heavy and you end up smelling of oil and gasoline after every drive. :)

Offroad Seven

While the car was in running, registered and mostly-drivable condition when I bought it, I nonetheless had several improvements in mind before it would be truly track worthy. While this car is likely to be a project car for the rest of my life, for the more immediate future I plan on a series of “Setting up a Seven” blog posts about work I have already done including the safety setup, wheels/tires, exhaust, suspension, etc… In the meantime enjoy this video of Rob doing a run at the last Lotus Club autocross of the 2009 season.


video by cxcheng