sincityIS

Those who lowered with eibachs on their IS250....

1. Did you cut the bump stops?
2. Will my car ride too stiff if I don't cut them?
3. Are there adverse affects to cutting/not cutting?

I dont want to not have enough travel, but I also don't want to have too much and I know the bump stops were designed to stop the suspension where it is at for a reason and just because you put on lowering springs I dont see how the car should have more up travel then with OEM setup.

iSuxeL

iTrader: (21)

Im wondering the same thing, but from what I know youre supposed to cut half of it or something, it should come with directions though.

sincityIS

It does say to trim 10mm in the instructions, but I never did on any of my previous cars I have lowered and they seemed to work fine?

kilo6_one

iTrader: (2)

i cut them......... the recomended amount, my experince is that it really does not matter, however if you were to bottom out hard enough and there is not enough give you could damage something, possibly the strut or worse.

the person to ask is lobuxracer, he knows more about cars then the tech manuals.

but i have always followed directions, they are included for a reason

sincityIS

How could you damage the strut by not cutting them. I would think that cutting them would be more prone to damaging the strut since you can make the shock over travel and possibly bottom out, which can cause premature wear and damage, right?

lobuxracer

iTrader: (2)

Right, but the other reason the bump stops are there is to prevent coil bind in the springs. There are a lot of ways to skin the cat when it comes to springs, and I would follow the spring manufacturer's recommendation unless I knew there was a problem with it. The real issue is, it isn't possible for a home mechanic to fully test a spring install, so you are pretty much stuck with following their instructions.

The only sure bad thing you get from leaving the stops at the stock length is you will hit them with less compression than if you cut them. When you hit the bump stop, your spring rate skyrockets to near infinity and it can cause handling issues almost the same as if the spring went into coil bind. The rubber they use for the stop is supposed to reduce the rise in the spring rate, but it doesn't always work the way you'd like it to.

sincityIS

Well am I right to assume that the OEM designed bump stop was designed for the shocks stroke? I mean if you had aftermarket shocks that were shorter then I could understand trimming the bumpstop, but I can imagine they would leave that much up travel on the shock after the bump stop has exhausted.

There are 2 things I am looking to avoid if I trim the stop.
1. Bottoming out of the shock
2. Not having enough stoppage to prevent the tire from slamming in the fender on big bumps.

There are things I am looking to avoid if I don't cut.
1. bump stop acting like a spring and causing a rough ride
2. Not enough travel.

So in other words what I want it is to not sacfrice ride or put undue stress on suspension components.

lobuxracer

iTrader: (2)

Then you're going to have to do some engineering on your own, starting with measuring the shock stroke. Then you need to install the shock without the spring and fully compress the suspension, first with the wheel off to ensure the shock doesn't bottom out, then with the wheel on to measure the clearance between the tire and the wheel well. Be sure to leave at least 10mm clearance at full compression to allow for component flex in service (your suspension bushings are rubber, and so is your bump stop - they will allow movement under normal suspension loading, but keep in mind, suspension loads are calculated in tonnes.)

Finally, you'll need to measure full compression on the spring to see how long it is at coil bind, then ensure the shock never gets that short between the perch and the hat in service.

It's a PITA to do, but if you check everything, you can be sure you won't damage anything.

Also, I would be concerned as you are about compressing the stock shock too much. If it bottoms hard it's very painful for the suspension and potentially damaging to the piston inside the shock.

sincityIS

Or maybe I should trim 5mm instead of the 10mm they say you should trim. This way it will be a happy medium.

sinister2c

just take it out...thats what used to do to hondas.

pwpanas

Undoubtedly, what's good for a Honda, must also be good for a Lexus, right?

sincityIS

Yeah I am going to listen to someone who can't form a complete sentence.

sinister2c

its only a damn car...eventually you'll need to replace the shocks so just cut the bump stop.

lobuxracer

iTrader: (2)

^^still not very helpful advice. Eventually, you'll need to replace the entire car. That doesn't mean it's prudent to make modifications without considering the consequences and effects on service life.

07IS350

Wow.....