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Ex-Mooderator
2001 RSTi, 2011 WRX Hatch
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3,256 Posts
Discussion Starter #1 (Edited)
Some of you have read my Koni + Gymkhana thread and appreciated the measurements and photos I provided.

I am going to do the same now, but I'm going to open an entirely different can of worms...(You can click on all images for larger versions).

When I was building the setup, I took the time to measure the bump stops, and amount of strut travel you would have before you encountered them. The front bump stops measured 2.25" and available strut travel was 4.25":



I went out today and measured my static ride height (F/R: 14.375"/13.370").



I then used the distance in between the rim and the fender to get an accurate measurement of how much droop travel I have (5.125" static, 9.125" at full droop = 4" of droop travel):


So looking at the amount of strut travel available at full droop (4.25") and the amount of droop I have from static height (4"), you would assume that I have .25" of travel before I hit the bump stops...that's close, but not quite.

Because the wheel is mounted at the end of a lever (your control arm), and the strut is mounted farther in, 1" of wheel movement only equals about .97" of strut movement (Note: .97 is the only ratio I could find online, if you have something more accurate, please supply it!). For my 4" of droop travel, this is only ~3.88" of travel at the strut. And 4.25" - 3.88" = .37" of travel before the strut hits the bumpstops.

At least I am on Konis and can add an inch of bump travel easily:
http://forums.nasioc.com/forums/showthread.php?t=602326
http://www.turninconcepts.com/product_info.php?cPath=1_9_7_480_490_507&products_id=458

This is not too bad, but what about folks that are lower?

JdmGary is on P1 springs, and noted yesterday that his ride height was F/R 13.75"/13.25"
This makes his droop travel 4.625" and inner strut travel 4.48" meaning that his car is always sitting ~0.23" on the bump stops, or basically...just touching them.

This leads me to believe that most lowering springs are really acting as helper springs for the bump stops and that the bump stops are really doing all of the work...

I don't think this a good thing... Are these springs designed with this in mind?
I know that the stock suspension is dependent on the bumpstops as an integral part of it's function, but I'm not sure these bump stops were designed to do more work than the actual springs that are installed...

Discuss.

-- Dave
 

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Ex-Mooderator
2001 RSTi, 2011 WRX Hatch
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3,256 Posts
Discussion Starter #2
It would be great if someone who is on P1 springs and doesn't have dust boots could take a picture of their bump stops with the car at rest?

I think if you turn the wheel enough, you can get a picture of the strut from the front of the car...

-- Dave
 

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Registered
88 XT6. 2.7l H6, 4.11 5MT
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565 Posts
I'm not sure of the case of your springs, or P1s. but most lowering springs that I've worked with that offer a substantial drop in ride height and increased spring rate include something in the instructions/package to tell you to cut/remove/replace the bump stops.


with an increased spring rate, the bump stop doesn't need to be nearly as big to prevent the strut from bottoming out.....so cut it in half.




I run without them.....but am experimenting with shock/strut/spring combos to get the ride height, and am using el cheapo used stock shocks/struts and don't care about destroying them (although still don't bottom out on them, being dropped about 3" from stock with 400lb/in springs)
 

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The Silverback Mod
05 Black OBS
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8,896 Posts
I cut the tallest nub off ALL bump stops (front and rear) when I last did my Swift/Tokico upgrade. Then checked it with a zip tie on all four strut rods ~ drove the sh*t out of the car over dips and in corners! No touchy bump stops = No bouncy on bump stops!
 

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Registered
2000 Imp 5 door Sport
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6,269 Posts
sorta kinda on topic. is that yellow bump stock the factory one or did you get it with your konies caues i didn't get one with my konies
 

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Ex-Mooderator
2001 RSTi, 2011 WRX Hatch
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3,256 Posts
Discussion Starter #7
sorta kinda on topic. is that yellow bump stock the factory one or did you get it with your konies caues i didn't get one with my konies
All factory.

-- Dave
 

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2.0L Turboner
94 RWD WRX & 82 EJ Brat
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8,673 Posts
Although I have nothing to contribute to this thread I just wanted to thank you Dave for taking the time to post this information. My eyes were opened to poor amounts of suspension travel when I began reading Stretch's threads over at IWSTI and now I'm much more critical about spring and strut upgrades. I hope the information you've posted will open others' eyes.
 

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Ex-Mooderator
2001 RSTi, 2011 WRX Hatch
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3,256 Posts
Discussion Starter #11
I don't really need any measurements...

I'm just stating the fact that if your ride height is below 14in in the front, and you are using stock bumpstops, that you are sitting on them 100% of the time.

If he used the stock bump stops w/o cutting them, then he's riding on them, it's that simple.

The question for folks is if they care that they are riding on their bumpstops or not. I do, so I'll be trimming mine immediately, and then possibly getting the koni bump travel extenders that I linked in my first post.

I'd rather have the Konis do their job, vs having to waste time fighting extremely non-linear spring rates due to encountering bumpstops.

-- Dave
 

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Ex-Mooderator
2001 RSTi, 2011 WRX Hatch
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3,256 Posts
Discussion Starter #13
i'll be buying those exstenders this week. you know if they work in the rear just fine too?
The only question is of clearance with the axle boot in the front. I believe the rears are directly open to the road, with nothing else in the way. I'd get under there with a ruler and check though...

-- Dave
 

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Registered
2000 Imp 5 door Sport
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6,269 Posts
The only question is of clearance with the axle boot in the front. I believe the rears are directly open to the road, with nothing else in the way. I'd get under there with a ruler and check though...

-- Dave
well they say for the front of a subie. ill measure this week but that would not only solve my current problem of not drilling a centered hole but would give me more shock travel where can i lose?

thank you so much dave i need to buy you a beer some time. your have saved me ass a couple times now ill involving konis and springs haha
 

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Ex-Mooderator
2001 RSTi, 2011 WRX Hatch
Joined
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3,256 Posts
Discussion Starter #15
well they say for the front of a subie. ill measure this week but that would not only solve my current problem of not drilling a centered hole but would give me more shock travel where can i lose?

thank you so much dave i need to buy you a beer some time. your have saved me ass a couple times now ill involving konis and springs haha
Yeah, when you were describing your issue the other day, I figured these would be perfect.

They don't mention them for the rear, but there is no reason they wouldn't be advantageous...

Just watch out that you have less bump stroke (before encountering bumpstop) length than you have max-compressed-spring length.

Would hate to give you more strut travel in trade for coil bind... At least if you are getting coil bind, you can always add longer bump stops, or use a different spring...

-- Dave
 

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Registered
2000 Imp 5 door Sport
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6,269 Posts
ya i noticed today autoxing that i hit my stock bump stops anyway. but ill be on ground controls so i don't think i should have issues. if i do ill get a longer spring.

mom is depositing state taxes first part of this week once those hit ill be getting some extenders and posting some good pics
 

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Premium Member
2.5RS
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8,447 Posts
great write-up dave. This does involve some issues for me. I've always felt that my KYB's were just not performing well or my fenders were getting smashed..but now that I think about it..its most def my bumpstops..even in the rear.

What alternative do use AGX/P1 users really have...Camber plates to add some length?
 

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Ex-Mooderator
2001 RSTi, 2011 WRX Hatch
Joined
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3,256 Posts
Discussion Starter #20 (Edited)
great write-up dave. This does involve some issues for me. I've always felt that my KYB's were just not performing well or my fenders were getting smashed..but now that I think about it..its most def my bumpstops..even in the rear.

What alternative do use AGX/P1 users really have...Camber plates to add some length?
You can cut off the thickest/largest section of your bumpstop...that's probably the best route.
This is the section from 1.5" to 2.25" mark on my measuring tape in the below pic:


That should give you about 1/2" before you hit the bump stops from static height, and then when you do hit them, they will be a bit softer than they would be at full-length. The only issue with this is that you won't have the bumpstop supporting your car's weight at rest, so your ride height will probably decrease a little bit...adding more clearance issues...

Camber plates would raise your ride height a bit, but your bump travel would not be affected...the only way to gain more bump travel would be to cut the bump stops.

-- Dave
 
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