Nerd Alert! - OEM Bumpstop Resiliency Over Time

[donaldjl]

This was prompted from a conversation with Scott (scotman) stemming from the Koni shock thread. The topic briefly came up about the OEM bumpstops and how well they aged over time and miles. Did they get stiffer, softer, no real difference? We have some basic information now. Using the Instron in our lab, I took the opportunity to measure one of the stops before I assembled the second strut assembly. Once the old struts came off, I disassembled them and tested the used parts for comparison. It's not a ground-breaking statistical study, but basic data sees the used bumpers losing around 24% of their load bearing capability at a given displacement after around 97,000 miles. Variability between the left and right may not be correlative to the side, or statistically significant given a sufficient sample size.

Ideally, I would test 10 new parts, and ten used parts all with similar mileage and driving environmental conditions. Today, we have to take what we get.

 

[scotman]

I couldn't see any physical degradation. I assumed a precise measurement might see 35 percent. I certainly can't feel any difference in use. I'm impressed with the low loss!
Thanks for the data Don!
How do the STRT Koni dampers feel so far?

 

[donaldjl]

Sorry, was in the Yoop and just saw this.

Lovin' the Konis so far. They seem a bit stiffer in initial damping and moreso in rebound, but very comfortable on the road, and not beating things up on our wonderfully pockmarked and potholed pavement. Brake dive and side-to-side transitions seem more controlled.

I test foams here and there, and have found them to be variable at times regarding degradation over time and under various conditions. Some stiffen up and seem to harden, some sack out and take a permanent set. It may not have been a big difference, but given what I saw, I'm glad I replaced them. I don't know how much time our cars spend on the bump stops, but seeing as how they're an integral part of the system, the change from original seemed to warrant the replacement.

I also don't know for sure whether or not third-party parts would need to meet whatever requirements the original parts meet unless they're being sold to the actual manufacturing plants. If, say, Autozone or O'Reilly's offers them as OEM replacement, they probably should. Otherwise, if they're dimensionally within tolerance, that may be what's important to some parts manufacturers. Aftermarket adherence to the original specification might be hard to enforce.

 

[scotman]

I like the overall feel of the STR-T. On the H&R coils it definitely feels like the Koni Sport set at the soft end of the adjustment scale. Which, given the rough and choppy condition of Michigan roads, is perfectly fine.