BMW4X4 vs. 4X4BMW

Originally printed in the October 1993 Roundel

by Gordon Haines, iX Registry Coordinator. Membership Info

*After taking delivery of the red four door `89 iX, we had to endure about two weeks of Denver's typically dry November before the next freezing rain and snowfall. We had attached our "BMW4X4" vanity plates, installed studded Vredesteins on factory steel wheels and anxiously awaited a chance to try the all-weather Bimmer in the elements.


*The opportunity came on a snowy evening, but frankly the testing was disappointing because it was so uneventful and undramatic. But then as we pulled into our driveway, a Jeep slid through a nearby intersection and bounced off the curb. Perhaps the streets were slicker than we had thought!

*We decided to make a comparison between the iX and our old faithful '71 Volvo 142E. With skinny studded snows, limited power, and a 50/50 weight distribution, there are few rear drive cars which can match a Volvo's traction on slippery roads. In the heavily falling snow, we prepared for a shoot-out on the streets of our neighborhood. Starting in the lead in the iX, Gordon blasted up the hill, exercised the ABS at the stop sign, continued up the hill and parked it in the garage. As he climbed out of the iX and closed the garage door, Bev in the Volvo was nowhere in sight.

*After she finally arrived, Gordon took the Volvo to the hill and learned why it took her so long to return. It was extremely slick. From that night on, we have been believers! The 325 iX truly is awesome in the snow. Now with 38K miles on it, the `89 "BMW4X4" has served as Bev's daily driver on her 50 mile commute and has been perfect for occasional winter trips to the mountains with the dogs. Gordon, who has been coaxing a heavily modified `74 Fiat Xl/9 through 17 winters (and until recently drove a tricked out 6-series which rarely saw rain or snow) became more and more envious of the iX for its performance in poor weather. Perhaps he should buy a clean `88 iX 2-door with Recaros.

*But Gordon really appreciates crisp handling. He has been racing Bill Schaefer's ITA tii and Gregg Ten Eyck's ITC/GT-4 Datsun and drove to a 3rd place finish with Co VanHerwaarden in an M3 in the '91 SCCA Escort World Challenge Series race at Sears Point. Could this BMW fanatic be happy driving an understeering, moderately powered, taller-than-your-average Bimmer regularly on Denver's normally dry streets? He decided "yes" -- if some improvements could be made.

*After looking at five or six `88s, we decided to buy the clean white one with 58K miles we found at the BMW dealer in Colorado Springs. A week after we took delivery, Gordon took it to the Rocky Mountain Chapter's 1992 Icekhana on the lake at Georgetown. We had installed the white "4X4BMW" plates and studded 185/65 R 14 T Hakkapeliitta 10's mounted on factory steel wheels. Yes, we got some grief over the full moon covers (you saw it here first), but at least we had no trouble with snow packing into the basket weave of the factory alloys. Gordon, Bruce Hazard and Bill Schaefer took 1st, 2nd and 3rd fastest times of day in Gordon's iX and everyone who drove this iX agreed that it was more than capable of "burning some ice."

Cut Spring *But now it was time to modify Gordon's `88 iX for the 90% of the time it would be driven in the dry and to reduce the unsightly excessive clearance in the front wheel opening. As we had often done on our low budget IT race cars, Gordon cut the front springs. One and a half coils were removed as shown in the accompanying diagram to lower the front of the iX one and a quarter inches. This modification was done with the struts still installed on the car and using two sets of spring compressors. It was a little tricky but really not too difficult given some experience with strut repair and a good air die grinder/cutter. (Koni's were installed about a year later.) After the mods were completed, a front wheel alignment check showed that toe needed to be adjusted. Cutting the springs resulted in increased camber which was just slightly out of spec on the right side. Overall camber was within spec and the extra camber would be perfect for driver schools and spirited cornering.

Wheels *But the real solution to the inherent understeer on Gordon's iX was to replace the stock wimpy rear 14.5 mm swaybar with a 19 mm Suspension Techniques bar adjusted in the stiff position. (NOTE: If you upgrade the rear bar, you will need to strengthen all the mounting brackets for the bar on both the body and the trailing arms -- see iXchange Newsletter #4 for more info.) The stock front 17 mm swaybar was retained but the rubber mounts were replaced with generic polyurethane bushings from J.C. Whitney. (These had to be carved somewhat to fit into the stock brackets.) The iX looked great and felt great on the street. Gordon couldn't wait to get to the track for some hot laps.

*But what about the engine? A Dinan chip seemed to be the answer. Gordon had taken 0-60 times prior to installing the chip, making repeated runs in both directions on the same section of highway. He followed the same procedure with the chip and found some significant improvements. It was also time to make some side-by-side comparisons between the stock `89 "BMW4X4" red four door and the modified `88 "4X4BMW" white two door, so he also made similar multiple runs in the stock `89. These runs were made without abusing the drivetrain. And for those of you expecting quicker times, please note that they were made at an elevation of about 5600 ft. where about 25% of horsepower is lost to the thinner atmosphere.

*The stock `89 was a little faster than the stock `88, perhaps because of fewer miles on the `89 or some improvements by BMW in the `89 vs. `88 model. But the Dinan chip made a very noticeable improvement in the straight line performance of the `88 iX. This showed up as a 1.4 second reduction of 0-60 times and a feeling that the engine was very strong pulling to the redline which was increased to 7K rpm. (Such a noticeable improvement may not be possible on later models. Gordon installed a Dinan chip in a `91 iX and measured a smaller improvement of 0.7 seconds and no detectable increase in the rev limit.)

*But the real test would be on the track where the effect of both the chip and the suspension mods could be measured. So on one of those glorious Colorado sunny spring days, Bev and Gordon left Denver and convoyed 120 miles south on 1-25 to Pueblo Motorsport Park. Cruising at 70-75 mph, mileage on both cars was 26.8 mpg with no detectable difference because of the Dinan chip, except for the need for premium unleaded. The Pueblo track is a 2.2 mile road course at 4900 ft. which includes a full drag strip on the front straight with terminal speeds around 100 mph before a 70 mph decreasing radius sweeper at the end. The back section of the track includes a good combination of low speed turns and elevation changes to test handling and torque characteristics.

*Gordon has probably taken 600 laps around this track and the day we were there, we had it completely to ourselves. Unfortunately, the concrete barriers separating the two drag race lanes at the start line were in place. This required entrance speed to the front straight to be reduced from about 65 mph to about 45 mph and prevented a direct comparison with ITB 2002 times which are in the 1:56 range. The `88 was run with Pirelli 600s and the `89 with Michelin MXV3s, both on the factory alloys. Later testing of these tires on the same car (the `88) showed no significant difference in lap times because of the tires. The results of testing quantitatively proved what is immediately apparent from just driving the two cars. The modified iX is significantly faster in all regards and a real pleasure to drive. And it handles like a BMW should.

*The test results summary:

* Average best three lap times on the stock `89: 2:08. On the modified `88: 2:01. (The difference of7 seconds is very significant, exceeding the difference between the fastest and slowest cars in a typical race class.)

* Average Quarter mile results on the stock `89:18.6 sec. at 78 mph. On the modified `88: 17.5 sec. at 82mph. (This represents 8 car lengths, going away.)

* Average 0-60 times (5600 ft. elevation) on the stock `89: 10.76 sec. On the modified `88: 9.83 sec.

* On the track, the stock `89 exhibits significant understeer upon application of power exiting the turn. This requires the driver to try to "run over" the apex of a turn, get on the power early and rely on the plowing to move the car outward. It is not a comfortable handling characteristic for anyone who prefers the neutral characteristic of a typical BMW. The stock iX feels under-powered and has a pronounced flat spot when shifting from 2nd to 3rd.

*In addition to more power at the top end, the modified `88 has significantly more mid-range torque than the stock `89. It is still nearly impossible to break the rear end loose, but this "4X4BMW" can be driven through turns like a traditional BMW. Transient handling is much more crisp than the stock iX. Power can be applied much earlier in the turns without worrying about running out of track on the outside. Surprisingly, it also exhibits less oversteer when lifting in a turn, perhaps because the stiffer front springs decrease the effect of forward weight transfer.

*In stock form, the 325iX is a very capable vehicle. Especially if the car is not driven in a manner in which the few quirks of the all wheel drive detract from driving enjoyment. For driving schools and other demanding encounters of daily driving, the modifications described have proven to be very gratifying. With these relatively simple changes, the 325iX is truly a Bimmer for all seasons. Weather or not!

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