Z4m coupe seat rocking

[internetlag]

Hello, my z4m imola seats have started to rock under acceleration. Im a tall guy so I have my seat set all the way back just before they touch the bulkhead. Under any hard acceleration I can hear the back of the seats hit the bulk head. The mounting bolts are tight and cannot be tightend anymore, this is the back rest pivoting back under acceleration.

Any ideas on what this could be and possible solutions? Do these cars suffer from the bushing issues z3s had?

Additionally if new seats are the solution, im curious to see what seats and mounting solutions are around that will potentially sit lower than the M seats do. Im on the larger side so pole positions are out of the question but I have seen recaro LSBs fit quite nicely.

[Finnegan]

Bushings are not an issue I’ve seen before - although these cars are now “vintage” and some wear and tear over time is inevitable. Some flex is normal I think.

If memory serves, when I got the car back in 2010, I weighed 210 at over 6’ and noticed something similar with flex. At 170 now - I don’t deadlift 500 these days - I don’t notice the same issue.

One idea would be to sit in the passenger seat, and have somebody else drive and provide the type of acceleration that causes the issue in the driver’s seat. If it’s the same, then i’d suggest there’s a normal amount of flex in both seats, since the passenger seat should have seen far less use.

If the amount of flex is equivalent, then I think you’ve already hinted at the potential solution with racing seats - but fitment outside the narrow “skinny guy” versions is tricky given limited space. You should be able to use the search feature to find what people have tried and succeeded or not succeeded with over the years. Replacing the interior door panel with a flat adds space as you’re removing the arm rest. But that’s a pretty hard-core mod that is more track oriented.

[Efthreeoh]

So Z3's have the seat rocking problem. Long ago, there was a cure developed by the aftermarket to swap out the nylon bushings inside the seat rails with Delrin (plastic) bushings. Being the bushings are a replaceable line-item unit in the seat the BMW P/N is 52107137499. It does not reference to use in the Z4 seat rail. In older BMWs individual seat parts are called out in the seat parts diagrams wherein later BMWs there are no listings for equivalent parts. For example, in E30s and E36s BMW has the electric drive motor drive cables as separately replaceable parts whereas in later models BMW does not offer the cables as replaceable parts. However, I own both an E37 Z3 and an E86 Z4. There are many common parts between the two chassis that I have noticed over the years. It may be possible the Z3 Delrin seat rail bushings fit the Z4. Just speculation on my part.

https://www.bimmerworld.com/BMW-Inte...107137499.html


It might be worth a try, or you could call Bimmerworld.

[86Zed]

How much deflection, i.e. 'rocking', are you suggesting? Even racing bucket seats flex and move under higher loads in the absence of external bracing.

As Finnegan mentioned, it may you are just a very observant owner/driver!

[internetlag]

Originally Posted by 86Zed

How much deflection, i.e. 'rocking', are you suggesting? Even racing bucket seats flex and move under higher loads in the absence of external bracing.

As Finnegan mentioned, it may you are just a very observant owner/driver!

Id say its about 2 inches backwards, just enough that my seat hits the rear bulkhead and makes a popping sound when no longer accelerating. I dont remember having this problem when I first bought the car.

I might just source a set of sportster cs seats, in the mean time ive raised my seating position and moved an inch forward to counteract the rocking.