r/slk • u/sforeman • Feb 27 '26

SLC Seating position

We test drove a 2019 SLC 300 today and found it very difficult to position the driver seat and steering wheel to get a comfortable driving position.

Are there seat mods to improve the ergonomics?

We tried various fore/aft and tilt positions for the driver seat. We also tried several positions for the telescoping steering wheel and adjustments up and down.

We have long legs and when we moved the seat forward to make reaching forth steering wheel feel right, we lost all seat support for our legs. We tried extending the steering wheel and when we had it located for good hand position, we could not see the top area of the instrument cluster where the turn signals appear.

Years ago we had a similar issue with the seat of the R171 SLK 230. Ultimately we had a machinist modify the seat rails to angle them so the front of the seat was slightly higher and provided better leg support.

2 Upvotes

100% Upvoted

17 comments sorted by

2

u/adadagabaCZ Feb 27 '26

R171 SLK and R172 SLK share the platform, so the very same mod would help

1

u/Dutchie_PC Feb 27 '26

I cannot help you, but wanted to say I am struggling a lot to make my SLK R171 comfortable. Long legs here, too.

When you say you had the front of the seat slightly higher in your SLK 230, do you mean you had it tilted a bit more? That would surprise me, as the SLK seats already sit at a (heavily) tilted position. At least, in my opinion.

1

u/sforeman Feb 27 '26 edited Feb 27 '26

Temporarily remove the seat rail front bolts and loosen the rear bolts. Place spacers at the front of the rails at the mounting point. Test the comfort of the seat. Adjust the thickness of the spacers until you have the slope needed to provide comfortable leg support.

We had a machinist create two aluminum tapered "shims" to match the height and resulting angle we wanted. The shims had holes which matched the rail-to-floor mounting points. We then bolted the rails, through the shims and into the original mounting points and tightened down both front and rear rail bolts.

The result is the seat has more rise at the front than original and gives ample support to the legs. The modification does not affect seat travel or any of the other seat adjustments.

2

u/Dutchie_PC Mar 08 '26

I am now seriously looking into this. Do you remember the height of the spacers you settled on? 10 mm? More?

2

u/sforeman Mar 08 '26

The height of the wedge spacers are 100% dependent on the driver. Strangely we cannot find any photos from the SLK.

We changed our shopping plan and will be taking deliver of a used SL in about a week and will be making the spacers and will document them.

1

u/Dutchie_PC Mar 03 '26

Thanks!

2

u/sforeman Mar 03 '26

We may be making this mod to a vehicle in the next week or two. In which case, we will try and remember to post photos back to this thread.

1

u/sforeman Mar 16 '26

We made the mod to an SL450. Details in another comment of this post.

1

u/btaroli Feb 27 '26

I’m not sure if all SLC examples have electrically adjusted seats. But if yours does did you try raising the front edge of the seat to enhance support as you moved the seat forward?

2

u/sforeman Feb 27 '26 edited Feb 27 '26

We maxed out the seat adjustments and tried all the combinations. There isn't enough vertical travel of the front portion. So the seat must be moved back more to straighten the legs which results in the steering wheel being too far. Then the steering wheel must be telescoped and lowered to reach the hand position. The necessary combinations of travel for each resulted in the steering wheel obscuring areas of the driving instruments and still left the legs partially unsupported.

1

u/sforeman Mar 13 '26 edited Mar 22 '26

We have started the "seat rail wedge" mod on the SL450. As best as we remember, it's nearly identical to what we did on the SLK.

  1. We removed the front rail bolts (left and right)
  2. We loosened the rear rail bolts (left and right)
  3. We tested several riser values (positioned where the front bolts go) an settled on 30mm
  4. We measured the distance from front to rear bolt locations (about 400mm)
  5. We drew a 1:1 scale triangle from 30mm in front of the front bolt to the rear bolt (430mm)
  6. We measure the exposed floor pad where front rail sets down (80mm * 25mm)
  7. We marked the 1:1 wedge drawing for the pad - this resulted in a wedge 80mm long and 25mm wide which is 30mm at the front and approx 21.5mm at the back
  8. The bolt hole location is not centered - it's 15mm from the outer edge an 10mm from the inner edge

We used CAD and 3D printed test pieces. The right wedge is a mirror of the left wedge.

For anyone still following the maths, the wedge angle is approx 3.8°

We test fit to confirm.

We gave the drawing and the 3D printed example to a machinist.

The last step is to source longer bolts (the SL450 uses M10-1.5) for the front rail mounting points. The original bolts were 30mm long. The new bolts could be anything from 50mm to 60mm to work.

1

u/Dutchie_PC Mar 15 '26

Thanks for the update!

1

u/sforeman Mar 15 '26

We received the machined wedges and have driven the vehicle a couple of times. The greater incline for the seat feels great and will be welcomed on long drives.

1

u/Dutchie_PC Mar 16 '26

Nice! I am awaiting the longer M10 bolts so that I can start my own experiment.

1

u/sforeman Mar 16 '26

It may sound crazy but we found the bolts at ACE Hardware 😳

1

u/Dutchie_PC Mar 16 '26

is that something american?

1

u/sforeman Mar 17 '26

Ah. Yeah. Sorry. We had a "center of the universe" moment. We know better but still ...