118mm Rear Bump Stop - Part Number 1K0 511 353 N
The bump stops in most modern day Volkswagens (and plenty of other cars as well) function as supplemental springs. If you take a look at the picture above, you’ll notice that the bump stop is designed to get progressively stiffer. The narrower nose section is significantly softer than the larger ribs in the middle. When carrying a heavy load or during aggressive driving, the nose contacts the shock body and the sections collapse. As more sections collapse, the spring rate of the bump stop progressively gets stiffer and the combined spring rate increases. The rear bump stop usually has more travel to deal with than the front (from weight change resulting from baggage or passengers) so the length is about double that of the fronts. The system is finely tuned and handling changes can be made by simply altering the length or stiffness of the stop.
Bump stops are usually cut when the suspension is lowered too free up some travel. If you lower the MK5 too much, you end up riding on the bump stops and the ride becomes very hard. Not fun. By cutting the stops, you gain back some comfort but end up with a huge, sudden increase in spring rate when you do contact the bump stops. You lose the progressive nature of the uncut stock bump stop. Not exactly a good thing when you’re in the middle of a turn and you hit a mid-corner bump. Spring rate goes up a lot and it can upset the chassis of the car.
If you are using the springs from the later model year GTI’s with the lowered ride height or lowering springs with a mild drop (Eibach Pro-Kit), you might want to consider using the Euro bump stops versus cutting your existing ones. It’ll help preserve the progressive ride characteristics that the factory designated. The US GTI comes with 133mm rear bump stops and 70mm front stops. The Euro spec ones are 118mm for the rear and 55mm for the front. If you compare the two side by side, it’s like taking off one of the middle ribs.
The part numbers are :
Front: 1K0 412 303 F
Rear: 1K0 511 353 N
I already have the shorter front stop but was still running on the 133mm rear stop. I purchased the 118mm rear stops from urotuning.com
to allow the rear a little more travel with the lower 2008 and up suspension.
A little unrelated but Urotuning sent me two different bump stops. One was the original part and the other is the Febi OEM equivalent. They feel the same but are two completely different colors. It’s giving me ocd. Urotuning assured me that they are the same though.