Bump Stop Trimming

Bump Stop Trimming

Without a doubt lowering springs is easily one of our biggest sellers. It’s a simple upgrade for someone wanting to lower their vehicle but not wanting to really sacrifice much in the way of ride quality, and it’s also much more affordable than a coilover kit. This is an especially common upgrade for people with newer vehicles, or cars still under warranty (or maybe they don’t have much to spend since they just got a new car).

As many of you may know, we make our lowering springs compatible with factory (OEM) dampers. Not necessarily in just fitment, but also in spring rate. Our lowering springs are not very aggressive. If you take a look at our lowering springs’ specifications for your vehicle, you may see that the ride height drop is not too aggressive (maybe better than some other manufacturers). Some other applications of our lowering springs may seem to be very aggressive. It’s all a matter of how much room we have to play with when designing our lowering springs.

Most important for customers is reducing the tire to fender gap. As of the past few years, the request is for a “flush” fitment, where the tire just closes up the gap with the top of the fender opening. As much as possible, we want to create that type of fitment for the customers, even making a staggered ride height drop for front and rear to achieve a nice and even wheel gap. But, where we reach limitations is the factory damper stroke length.

Some factory suspensions have very limited stroke length, and this makes it increasingly difficult to design a spring that will aggressively lower a vehicle. That isn’t the only limitation. We look at clearance with the fender, within the wheel well, as well as how it may affect steering/suspension geometry. We always design our lowering springs to give you the most ride height drop in as safe a level as possible.

So, in regards to trimming bump stops- why is this important? If we find that aspects, other than damper stroke length, seem to be very generous, we know that we can make a lowering spring that will work with a shortened bump stop. So we include a chart by vehicle application that shows how much you will need to trim for front and rear when installing our lowering springs.

Some cases may require a different type of trimming style for the bump stop. Typically it is just trimming the bottom portion of bump stop and retaining the top piece (A Type). Sometimes it’s the reverse (B Type). In other cases, you may need to trim a middle section and retain the top and bottom piece (C or D Type). See below the different style cuts we recommend, depending on the vehicle:


bump stop trim style

We know several customers skip the bump stop trimming step. This can cause several issues. We’ve added this measure so that you can retain a bit more stroke length at the newly lowered ride height. This also helps improve ride quality. Because the bump stop is made of a high durometer polyurethane material, it is like a secondary spring, but a really stiff secondary spring. Since the dampers are not valved to handle such a stiff secondary spring, it can make rebound feel really harsh. Some may say bouncy. Constantly hitting the bump stop can cause the damper to prematurely wear or potentially blow out, too.

bump stop trim 001

Bump Stops come in all sorts of goofy shapes. Mind you, these were engineered with a specific design.

bump stop trim 003

The bump stop itself is a really lightweight piece, but it is of a high durometer and takes a lot of force to compress. At least it is easy to cut into.

Fortunately, you can cut easily into the bump stop using a box cutter/safety blade. It slices pretty easily.

bump stop trim 004

Here’s a picture of a 2015 Camry bump stop. This is a more typical design that we see- top is a larger outside diameter and tapers, with billows that make it easier to determine which section we recommend trimming.

bump stop trim 005

Using a safety blade, we’re able to cut a bottom portion of the Camry’s bump stop. We’ll be retaining the larger piece on the left and reinstalling onto the front strut.

bump stop trim 006

This bump stop uses some plastic ring, likely to control the bump stop’s compression. In our case, we need to trim a middle section.

bump stop trim 007

We cut this into three pieces, and the middle piece will be removed. The remaining top (left) and bottom piece (right) will be reassembled on to the damper.

So, while you will have your suspension taken a part for a little while when installing our springs, take the time to see if your bump stops will need to be trimmed. Check the included instructions with our lowering springs to find out that info.

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This entry was posted by Paul P. on Friday, September 25th, 2015 at 10:28 AM and is filed under Tech. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.