Eibach's take on Bumpstops

[MFlight]

This is the answer I received from Eibach regarding the stock Bumpstops and installing their springs.

"Hello Tobbe, Regarding your question below. Our Eibach Pro-Kit for the 2010 M3 Coupe does not require modifications to the bumpstop. Our kit is made to work with the OE dampers and bumpstop as is. The kit is designed to have lowering of 0.8" at the front and 0.6" at the rear. There is still enough suspension travel before bumpstop contact with the lowering of our kit. The kit works great! You should not have any concerns. Please let me know if you have any other questions. Thank you for your interested in the Eibach product.

Best Regards,

Phong Diep | Research & Development Manager

Eibach Springs, Inc. | 264 Mariah Circle | Corona, CA 92879-1751
T +1 951-256-8300 x118 | F +1 951-256-8321
pdiep@eibach.com"

[rzm3]

Originally Posted by MFlight

The kit is designed to have lowering of 0.8" at the front and 0.6" at the rear. There is still enough suspension travel before bumpstop contact with the lowering of our kit.

Sorry, this is simply NOT true.

When lowering 0.8" at the front, the bumpstop WILL MAKE CONTACT. See pictures below where I measured the suspension travel to be around 0.75" before making contact with the bumpstop.

The actual suspension travel before bumpstop contact may be <0.75" (perhaps as low as 0.5" per Dinan) as my wheels are fully turned to the left, which raises the suspension slightly.

[MFlight]

Originally Posted by rldzhao

Sorry, this is simply NOT true.

When lowering 0.8" at the front, the bumpstop WILL MAKE CONTACT. See pictures below where I measured the suspension travel to be around 0.75" before making contact with the bumpstop.

The actual suspension travel before bumpstop contact may be <0.75" (perhaps as low as 0.5" per Dinan) as my wheels are fully turned to the left, which raises the suspension slightly.

What would you recommend in order to prevent the contact? This is the one issue that's preventing me from buying and lowering my M3. I'm looking for a good solution not a winging it solution that so many apply.

I thought by asking Eibach I would be able to get the answer I'm looking for but I guess it is never that easy.


Thanks...

[MrHarris]

Everyone that has eibachs say they could not be happier with the performance. What are the negative effects of hitting the bumpstops?

[Dartanium]

I thought modern suspension is designed to work with bump stop contact, progressive bump stops that contribute somewhat to the overall spring rate with sway bars included. But I am a dummy for proper amount of suspension travel, so I suspect that total suspension travel will be decreased as rldzhao have suggested unless a proper length strut is fitted with the shorter spring. If ohlin comes out an adjustable shorter strut, then our world would be perfect.

[MrHarris]

Yeah imagine is a quality shock company comes out with an EDC replacement shock that's designed to work with a certain spring (H&R, Eibach, RDSport) and at a reasonable price. That company would make bank!

[AMPowerJ]

Originally Posted by MFlight

What would you recommend in order to prevent the contact? This is the one issue that's preventing me from buying and lowering my M3. I'm looking for a good solution not a winging it solution that so many apply.

I thought by asking Eibach I would be able to get the answer I'm looking for but I guess it is never that easy.


Thanks...

Buy Dinan to be sure or just go with Eibach to save some $$$ and be a bit lower. I really think you can't go wrong either way even though I have Dinan. You probably sacrifice a bit of handling/ride comfort with Eibach over Dinan but I don't have any proof of that.

[quality_sound]

From my conversations with Eibach about the same question I was told that Eibach, on cars with progressive rate bumpstops, that the "spring rate" of the bumpstop is taken in to account when they design the new springs so they work as a package and that if you cut the bumpstop the total spring rate will be significantly lower than spec'd.

[disruptv]

my mechanic trimmed my bumpstops for my eibach springs...I was gonna use the e36 bumpstops but I couldnt get them in time...So far no problems w/bottoming out and dips...

[quality_sound]

It's not so much that you'll bottom out but the ride will be softer than intended. According to Eibach at least.

[GTM]

If it was my car, I would put Ei-bach springs and Dinan's bump stop.(from other BMW model)

[rzm3]

Originally Posted by MFlight

What would you recommend in order to prevent the contact? This is the one issue that's preventing me from buying and lowering my M3. I'm looking for a good solution not a winging it solution that so many apply.

I thought by asking Eibach I would be able to get the answer I'm looking for but I guess it is never that easy.

Thanks...

Well, here's how you can maintain the factory suspension travel before bumpstop contact:

1) get a E30/6 M3 bumpstop that is shorter than E92
2) modify your upper guidesupport to be slightly shorter
3) less aggressive drop

Let me just explain what happens when the car is constantly riding on the bumpstop.

Our front springs have a rate of about 160 lbm (pound mass) per inch of compression. So for every inch you compress, you need an additional 160 lbm.

Now, let's look at bumpstops. A bumpstop is another spring. On modern cars it selectively adds stiffness to the suspension. Our bumpstops are about 2.375" long, and 2" in diameter. Below you will see a similar, though not exactly the same, bumpstop force vs. displacement graph. You will notice that the curve is relatively flat initially, but shoots up when the bumpstop is compressed by just over 1" (25.4 mm).

On a stock car, there is still about 0.75" of travel before the bumpstop is compressed, and you get another 1" or so before the bumpstop force starts to shoot up and add significant stiffness to the suspension.

However, on a lowered car, let's say Eibach, you will already be riding on them, so you only get 1" or so of travel before the suspension becomes extremely stiff. This also reduces the amount of total (compression) travel allowed at the front wheels.

[MFlight]

Originally Posted by rldzhao

Well, here's how you can maintain the factory suspension travel before bumpstop contact:

1) get a E30/6 M3 bumpstop that is shorter than E92
2) modify your upper guidesupport to be slightly shorter
3) less aggressive drop

Let me just explain what happens when the car is constantly riding on the bumpstop.

Our front springs have a rate of about 160 lbm (pound mass) per inch of compression. So for every inch you compress, you need an additional 160 lbm.

Now, let's look at bumpstops. A bumpstop is another spring. On modern cars it selectively adds stiffness to the suspension. Our bumpstops are about 2.375" long, and 2" in diameter. Below you will see a similar, though not exactly the same, bumpstop force vs. displacement graph. You will notice that the curve is relatively flat initially, but shoots up when the bumpstop is compressed by just over 1" (25.4 mm).

On a stock car, there is still about 0.75" of travel before the bumpstop is compressed, and you get another 1" or so before the bumpstop force starts to shoot up and add significant stiffness to the suspension.

However, on a lowered car, let's say Eibach, you will already be riding on them, so you only get 1" or so of travel before the suspension becomes extremely stiff. This also reduces the amount of total (compression) travel allowed at the front wheels.

So by changing the stock bumpstops for the E30/6 M3 bumpstops I should be able to add the Eibach springs and still have enough travel left in the suspension? Will the different bumpstops change the performance of the Eibach springs due to the increase in travel not indicated by the company?

I would assume that this is what Dinan is doing with their package?

Thank you for the explanation...

[isugoo]

Originally Posted by MFlight

I would assume that this is what Dinan is doing with their package?

Yes- Dinan did it same way to all M3s (E90/92/93) and added rear spacer and modified rear spring pockets on E90 and E93s (rear heavy M3s).

[disruptv]

so now im curious

What are the benefits and cons of trimming the oem bumpstops that are on the car? Is there anything I need to keep an eye out on?

[TLud]

Originally Posted by rldzhao

Well, here's how you can maintain the factory suspension travel before bumpstop contact:

1) get a E30/6 M3 bumpstop that is shorter than E92
2) modify your upper guidesupport to be slightly shorter
3) less aggressive drop

Let me just explain what happens when the car is constantly riding on the bumpstop.

Our front springs have a rate of about 160 lbm (pound mass) per inch of compression. So for every inch you compress, you need an additional 160 lbm.

Now, let's look at bumpstops. A bumpstop is another spring. On modern cars it selectively adds stiffness to the suspension. Our bumpstops are about 2.375" long, and 2" in diameter. Below you will see a similar, though not exactly the same, bumpstop force vs. displacement graph. You will notice that the curve is relatively flat initially, but shoots up when the bumpstop is compressed by just over 1" (25.4 mm).

On a stock car, there is still about 0.75" of travel before the bumpstop is compressed, and you get another 1" or so before the bumpstop force starts to shoot up and add significant stiffness to the suspension.

However, on a lowered car, let's say Eibach, you will already be riding on them, so you only get 1" or so of travel before the suspension becomes extremely stiff. This also reduces the amount of total (compression) travel allowed at the front wheels.

Great explanatory post. My car with Eibach springs is not riding on the E36 M3 bumps (the same ones that come with the Dinan kit). I'll try to get a decent measurement in the next few days. I installed the new bumps at the same time as the new springs, so I can't comment on the Eibachs/stock bumps setup. I considered, but didn't attempt to shave down the guide supports, and I currently don't feel that there's any need to do so. I'm very happy with the current feel.

[J08M3]

About 8 months now with Eibach and OEM bumpstops, no problems here.... I'll keep you posted though if anything changes

[rzm3]

Just to sum things up w/o a prolonged discussion:

1. I have never driven or ridden in an Eibach-equipped car, so I cannot comment on whether the ride or so-called performance (however this is actually measured) is better or worse than stock. I have been merely stating facts about what happens when a car is lowered using springs w/o changing anything else.

2. But having owned both H&R (-1" front) and Dinan (-0.5" front but maintains factory suspension travel), I can share my observations for both. The H&R felt fine on smooth roads, but when I drove over slightly bigger bumps on the road, the suspension would often reach the limit of compression travel and make a somewhat hard contact with the chassis. I remember pming a fellow member and telling him that the car chassis felt "upset" when going over slightly rough roads.

Dinan on the other hand felt nearly the same as factory suspension in terms of the ride and comfort. I really do not have more comments except to say that it feels just like stock, except your car is now lowered by 0.5".

3. Now the million dollar question: which offers better performance? Well, it depends on what performance means to you.

In terms of the 'ride', I definitely feel that the Dinan kit is more tamed, feeling the same as stock and not rough over bumps.

How about 'handling'? Well, I cannot give an answer, as no one (i think) has tested/experimented these systems back to back in a controlled situation and judge the difference in handling, control, and lap times of different set ups. Neither do we have enough technical information to conduct a thorough analysis...

Hope this helps.

[quality_sound]

Originally Posted by disruptv

so now im curious

What are the benefits and cons of trimming the oem bumpstops that are on the car? Is there anything I need to keep an eye out on?

Trimming the bumpstops will make them less linear.

[MrHarris]

So Eibach springs +e36 bumpstops is a win? Where do we purchase e36 bumpstops?

[CT-Bimmer]

Curious as well.. received my Eibach's a couple weeks ago along with my MS Spacers and MS filter! Too bad the weather in CT sucks! In the meantime.. I guess I will order the bumpstops. Anyone know the price on these?

[disruptv]

Originally Posted by MrHarris

So Eibach springs +e36 bumpstops is a win? Where do we purchase e36 bumpstops?

Any oem parts store--contact gregw i think he knows a online retailer

Originally Posted by CT-Bimmer

Curious as well.. received my Eibach's a couple weeks ago along with my MS Spacers and MS filter! Too bad the weather in CT sucks! In the meantime.. I guess I will order the bumpstops. Anyone know the price on these?

They r inexpensive...Like 20-30 bucks for the fronts....I think you may need something else as well b/c ur a sedan...e92s only need front ones but verts and sedans need a few extra parts I believe