if you are sitting on the bump stops statically, you really have an issue. Dynamically, tie a zip-tie on the shaft and see how far that zip-tie travels up to or into the dump stops will give you a better sense of how much more compression travel you really need.
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Time to settle things - lowering springs and bump stops
- Thread starter TypeRx
- Start date
Bumpstops serve two purposes.
1. They protect the damper if you hit a bump that is well outside the designed limit. A bump stop will cause the saying rate to dramatically increase. This helps to stop compression before the internals of the damper stop the compression. The latter can cause damage.
2. They help prevent a sudden loss of control. As stated above, bump stops prevent the internals from stopping the compression. If this were to occur, the spring rate essentially becomes the sum of the elasticity of the materials of the damper. For practical purposes, you can think of it as a rate of infinity. If this happens mid corner and your on the edge of grip, you're likely to lose grip in a hurry Bumpstops help make it a bit more progressive so you don't lose control as easily. But as it still increasing the spring rate rather suddenly, you don't want to be running into it unless you happen to run over something mid corner.
The ideal result is that a bumpstops needs to be sorry enough to stay out of the way for all intended driving scenarios, but becomes involved when an intended compression event occurs. And it needs to do so as progressively as possible without allowing internal contact if damper components.
I'd follow the spring manufacturer's recommendation at a minimum. There are better solutions. But most of us won't be able to determine what is needed and availability of an off the shelf part that would meet those requirements may be difficult to find.
1. They protect the damper if you hit a bump that is well outside the designed limit. A bump stop will cause the saying rate to dramatically increase. This helps to stop compression before the internals of the damper stop the compression. The latter can cause damage.
2. They help prevent a sudden loss of control. As stated above, bump stops prevent the internals from stopping the compression. If this were to occur, the spring rate essentially becomes the sum of the elasticity of the materials of the damper. For practical purposes, you can think of it as a rate of infinity. If this happens mid corner and your on the edge of grip, you're likely to lose grip in a hurry Bumpstops help make it a bit more progressive so you don't lose control as easily. But as it still increasing the spring rate rather suddenly, you don't want to be running into it unless you happen to run over something mid corner.
The ideal result is that a bumpstops needs to be sorry enough to stay out of the way for all intended driving scenarios, but becomes involved when an intended compression event occurs. And it needs to do so as progressively as possible without allowing internal contact if damper components.
I'd follow the spring manufacturer's recommendation at a minimum. There are better solutions. But most of us won't be able to determine what is needed and availability of an off the shelf part that would meet those requirements may be difficult to find.
Hey guys, I am new here. Sorry for bumping this thread up. Unfortunately, I found this thread after I installed springs and shocks.
I installed KONI Yellow's (sport line) and Eibach PRO KIT springs and now I am wondering do I need to trim bump stops or not.
I've read every single message in this thread and still have this question opened
Shocks are rebound adjustable and I set mid-settings on both front and rear. Omg, corners on smooth road are so nice, almost no body roll. Steering response also very very nice.
I rode about 200km on this setup and feel like it rides smoother than OEM on small road imperfections, but larger curved bumps are more noticeable. At some speed and bumps frequency I can even feel slight bounciness from front to end (not simultaneously). I wound is that beacause I hit bumps stops and it triggers rebound quicker or should I play with adjustments, what do you think?
Thanks in advance.
I installed KONI Yellow's (sport line) and Eibach PRO KIT springs and now I am wondering do I need to trim bump stops or not.
I've read every single message in this thread and still have this question opened
Shocks are rebound adjustable and I set mid-settings on both front and rear. Omg, corners on smooth road are so nice, almost no body roll. Steering response also very very nice.
I rode about 200km on this setup and feel like it rides smoother than OEM on small road imperfections, but larger curved bumps are more noticeable. At some speed and bumps frequency I can even feel slight bounciness from front to end (not simultaneously). I wound is that beacause I hit bumps stops and it triggers rebound quicker or should I play with adjustments, what do you think?
Thanks in advance.
Thanks for the post with the diagrams. What's the purpose of "c" and "d"?Seems some lowering spring companies recommend trimming (Eibach, Tein, some H&R) while others are silent (UP, T-Sportline, and others). I have Eibachs and the instructions say to trim 25mm in back and 20mm in front. Did Eibach include this instruction when it's actually not necessary? Why do they give a different spec for front and back? All BS? Maybe - but I assume a reputable suspension company would add that into the instructions for a reason. If you look at some Eibach instructions, different trimming amounts are recommended for different cars and even whether you trim the top or the bottom. Again, I don't believe it's random.
Here's a good write up from the Tein website:
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:
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.
At the end of the day it's up to you on what your comfort level is. I'm sure based on driving styles and road conditions many will never run into a situation that maxes out the stroke to hit the untrimmed bumpstop so in those cases trimming or not will not matter. Note that Tein says not trimming "can cause several issues" rather than will cause several issues - meaning you may never experience any problem if you don't trim them. What ever amount your spring lowers your car by is the same amount you will lose in damper stroke.
Best bet is to follow what the engineer states to do. Less chance of a problem and if you have a warranty issue it's one less argument that can be used against you. Only thing lost is a bit of extra effort.
I've read every single message in this thread and still have this question opened
Shocks are rebound adjustable and I set mid-settings on both front and rear. Omg, corners on smooth road are so nice, almost no body roll. Steering response also very very nice.
I rode about 200km on this setup and feel like it rides smoother than OEM on small road imperfections, but larger curved bumps are more noticeable. At some speed and bumps frequency I can even feel slight bounciness from front to end (not simultaneously). I wound is that beacause I hit bumps stops and it triggers rebound quicker or should I play with adjustments, what do you think?
I'm dealing with this same exact thing right now. I've found that the rear suspension is sitting on the bump stops at rest. Not only that, they're actually compressed a bit. This is at STOCK ride height. Just last night I trimmed the first stage (about 7/8") from the bottom of the rear stops. Initial impressions are good, but I'll know more later.
This is probably why you never see a Model 3 sagging in the rear, even loaded up with passengers.
gregkang
Member
Thanks for the info. What do you think about Ohlins? They're DFV suspensions are specially tuned for EVs. I've got 21s" on my Y and not happy with the stance and would like to lower her without compromising the ride quality as much as possible. appreciate your feedback.
gregkang
Member
Thanks for the info SDM44. So the Eibach springs are for your white Model Y as pictured? What sizes/spec wheels are you riding on? I ask as I've gone with MYP 21" wheels and spec and with my tire set up my offset is tad negative. No issues with rubbing against fenders? Thanks.
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