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Project BMW 325is Part 5: The Driver Interface

Dan Barnes
Oct 11, 2003 SHARE

Having a car fit me properly is very important: I always feel like I'm trying to run in wrong-size shoes if it doesn't. Project 325 was never quite right. The factory power seats didn't offer much lateral support for the track driving I plan to do. Furthermore, the driver's-side seat had broken switches, resulting in a driving position that could allow the rearview mirror to conceal an entire Hyundai Accent two lanes over. I tried to remove the switches for replacement, but couldn't free them. At the same time, the seat weighed a hefty 67 lb--offering a superb opportunity to reduce the 325is' battleship-like curb weight. My goal for new seats was to save weight, lower the driving position for proper visibility and greater helmet clearance, and gain support and comfort. I found a solution at Sube Sports.

The Cobra Daytona is a great seat for a daily driver that will also see track duty. It should reduce weight in most modern cars, especially those with power-adjustable seats. It combines excellent lateral support with the flexibility needed for everyday comfort for a variety of body shapes and sizes. It provides slots for a competition or DOT-legal harness but also works properly with factory seatbelts.

The Daytona features a double-locking Keiper/Recaro tilt mechanism, in which a knob on the side provides infinitely fine tilt adjustment, and a bar across the bottom of the seat back allows the back to tilt forward for rear passenger access. Sube Sports offered the Daytonas in fabric or leather for Project 325. I like the idea of keeping the BMW's leather interior all leather but, in the end, applied the "go fast or suck" criteria and chose comfortable, breathable and ultra-grippy black rock fabric with reinforcements in high-wear areas on the bolsters.

Most aftermarket seats have a universal mounting interface and require a vehicle-specific bracket for installation. However, while the mounting bolt pattern is standard on most seats, there is no standard for the rest of the seat; the width of bolsters, reclining mechanisms, shoulder "wings" and other parts are entirely up to each manufacturer's designers. That makes it tricky for anyone attempting to design a bracket that will mount every seat in a car. Wedge Engineering is among the most experienced and widely used seat-bracket manufacturers and was recommended by Sube Sports.

My first attempt at installing the passenger-side bracket resulted in the inboard seatbelt mechanism running into the carpet. Danny Paisano at Wedge stayed late one evening to show me how the bracket fit. It was designed with a wider seat in a 325is that came with a smaller seatbelt tensioner assembly. Danny and his technician also were invaluable in removing the seatbelt latch sensor wire from the stock driver's seat so it could be transferred intact, a delicate and difficult task.

After several trial installations to assess various configurations, I realized that the bracket put the seat in just the right position if I mounted it directly, with no sliders and the upper, U-shaped brackets set evenly. It gave the lowest seating position for the lowest center of mass in the vehicle as well as being the lightest possible installation. The only downside is that only small people can be comfortable in the back seat, but the few who will ride there are likely to complain. The brackets offset the seats slightly outboard. I got used to the change easily enough but may decide to do something about it down the road. A Cobra Daytona by itself weighs just 29 lb, but with the brackets and belt tensioner, it weighs 45 lb--still a savings of 22 lb per side.

I found the best procedure was to install the inner seatbelt latch to the bracket, not even finger tight, providing plenty of wiggle room. Then assemble the seat to the brackets. With the seat assembly secure, I installed it in the car. Some force is required to press the seatbelt tensioner into the carpet padding so all the holes align. Tighten the fasteners only after all are threaded in. Last, tighten the bolt holding the seatbelt tensioner to the main bracket by sliding a box wrench between the seat and the center tunnel.

BMP Design provided a Schroth Quick-Fit four-point harness (see "Select Gear," December 2002). It is a version of the DOT-legal Rally-4 asm(R) harness. Schroth's patented asm (Anti-Submarining Mechanism) shoulder-belt design greatly reduces the likelihood of submarining during an accident, limits peak loads on the chest and neck and reduces intense contact with an airbag. The Quick-Fit belt is designed to be installed or removed from the vehicle in just seconds after the initial fitting. By mounting to the inboard seatbelt clip, rather than the mounting for the seatbelt tensioner, it combines the functions of factory belts and the superior driver location of a competition harness. The outboard end clips to a pigtail that is mounted to the factory seatbelt mounting system, using the factory bolt. (You bought your set of Torx bits months ago, right?) Quick-Fit belts are available in red and black for BMW E36, E46, E39 and MINI, and must be used only in the vehicle model and on the side for which they were designed.

I installed the MOMO Aluminum Sport shift knob from Project Rally MINI in Project 325. A 1/2-in. flat washer drilled out to 9/16-in. and dropped over the shifter held the shift boot higher to avoid exposing the shift lever. The MOMO knob is not as tall as the factory knob, so it is a little farther from the steering wheel and less comfortable to reach. Because it is aluminum, it transmits heat from the transmission when the car is parked. I love this shift knob, but it's not working as well as I'd hoped in this car.

MOMO's Corse steering wheel is proving to be a much better match. MOMO's E36 adapter hub was perfect. Be sure to disconnect the battery before going near any airbag, which is removed when changing the wheel. I smeared a little of the copper-based, conductive grease from the original wheel's horn contact ring on the adapter's corresponding surface and bolted it in place. The whole thing took just minutes.

It's taken some work, and a lot of tinkering, but Project 325's driver interface is now nearly perfect for my 6-ft 4-in. frame. One more area of Project 325 is now ready for the track.

Special thanks are due Graphicsworks, which provided vinyl graphics for the month's cover shoot on short notice.

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Sources

Griot's Garage
Tacoma, WA 98409
800-345-5789
www.griotsgarage.com
BMP Design
Tyler, TX 75701
903-581-1855
http://www.bmpdesign.com
Sube Sports
By Dan Barnes
78 Articles

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