Bump stops, im very confused. - JKowners.com : Jeep Wrangler JK Forum
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post #1 of 17 Old 11-29-2018, 08:56 AM Thread Starter
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Bump stops, im very confused.

So im sure im over thinking it but whayts up with bump stops? Do i have to run them? I know you add them so you don't flex too much and start ruining suspension components and having your tires hit your fenders. I just don't wanna over do it losing some articulation. Im running 3 inch rock krawler progressive springs, and Bilstein 5160s rated for 1.5 to 3.5 inches of lift.
People say that you add as much bump stop as you have lift which makes sense but does that apply to flat fender setups too? I have the aries aluminum tube fenders they clear the stop fender position by about 2 or 3 inches. I know i can try different setups but i dont understand anything about shock lengths and when i should add bumpstop for them or not. Anything would help because i want to tackle the install on sunday

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post #2 of 17 Old 11-29-2018, 10:41 AM
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You add bump stop for the increase in tire size not lift size. IF you lift and dont change tires you should not need any more bump stop unless you run longer body shocks that would bottom out. Then you would run enough bump stop to prevent the bottoming.

To see how much you might need you have to cycle the suspension with both tires stuffed, and one side stuffed and one side drooped.

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post #3 of 17 Old 11-30-2018, 03:15 PM
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Originally Posted by thedirtman View Post
You add bump stop for the increase in tire size not lift size.
What if you have a cordless Milwaukee sawzall and are willing to use it instead of increasing bump stop?

I'm running 3" bump stops now and want to increase tire size. Adding bump stop alone (with the same coils and shocks) will reduce my upward travel, right? Going from 3" to a 4" bump would reduce the cutting I need to do to fit 40's. At the same time, I am running 4" springs with the 3" blocks.

I'll see how much cutting of the tub i can tolerate before compensating with bump stop. I do want to try and keep that metal front fender support that sticks out with 40" tires and chopped stock fenders. I ordered a set of King hydraulic stops so I can adjust and get it perfect up front.
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post #4 of 17 Old 11-30-2018, 03:57 PM
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Originally Posted by White13JKUR View Post
What if you have a cordless Milwaukee sawzall and are willing to use it instead of increasing bump stop?

I'm running 3" bump stops now and want to increase tire size. Adding bump stop alone (with the same coils and shocks) will reduce my upward travel, right? Going from 3" to a 4" bump would reduce the cutting I need to do to fit 40's. At the same time, I am running 4" springs with the 3" blocks.

I'll see how much cutting of the tub i can tolerate before compensating with bump stop. I do want to try and keep that metal front fender support that sticks out with 40" tires and chopped stock fenders. I ordered a set of King hydraulic stops so I can adjust and get it perfect up front.
We run 4 inches of bump stop on our red 4 door with 40s. Seems to work out well. I think we could get away with about 3.5 or 3.75 if we really wanted to dial it in.

Last edited by spinuck; 11-30-2018 at 04:07 PM.
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post #5 of 17 Old 11-30-2018, 04:00 PM
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Originally Posted by spinuck View Post
We run 4 inches of bump stop on our red 4 door with 40s. Seems to work out well. I think if we could get away with about 3.5 or 3.75 if we really wanted to dial it in.
Which fenders? how much cutting with the 4" blocks?
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post #6 of 17 Old 11-30-2018, 04:51 PM
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Which fenders? how much cutting with the 4" blocks?
Trimmed stock fenders. Yeah, still quite a bit of cutting on the seam behind the front tire.
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post #7 of 17 Old 11-30-2018, 05:04 PM
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Trimmed stock fenders. Yeah, still quite a bit of cutting on the seam behind the front tire.
Did you go past the bolt at the bottom and re-attach some how or stop at the bolt? Grille trimming?
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post #8 of 17 Old 11-30-2018, 05:19 PM
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Did you go past the bolt at the bottom and re-attach some how or stop at the bolt? Grille trimming?
I did go past that then drilled a new hole and put the bolt there. Didnt need any grill trimming. I dont think I've seen anyone with 40s have to trim the grill, just 42s.
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post #9 of 17 Old 12-01-2018, 07:34 AM
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I did go past that then drilled a new hole and put the bolt there. Didnt need any grill trimming. I dont think I've seen anyone with 40s have to trim the grill, just 42s.
This is on the red one with 4" blocks?
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post #10 of 17 Old 12-01-2018, 07:49 AM
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Most people that go 40's dont worry about up travel and triming. They just bump stop it and runn almost all down travel. Most every one I see just has 3"-4" of up travel. Major modifications to the frame and moving of other components are need if you want to keep a resonably low lift. Of course, tire width, size, wheel backspacing, lift height, and shock travel will all come into play. The king bump are going to be a waste of time and money if you dont have much up travel in your set up due to the fact you will always be riding on them. And for crawling you are just as good off with the factory foam stops.

In all honesty it you would be better off jsut runnign 37's on 4" of lift with flat fenders giving your wheels and suspneison enough room to work in both directions.

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post #11 of 17 Old 12-01-2018, 08:29 AM
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Originally Posted by thedirtman View Post
Most people that go 40's dont worry about up travel and triming. They just bump stop it and runn almost all down travel. Most every one I see just has 3"-4" of up travel. Major modifications to the frame and moving of other components are need if you want to keep a resonably low lift. Of course, tire width, size, wheel backspacing, lift height, and shock travel will all come into play. The king bump are going to be a waste of time and money if you dont have much up travel in your set up due to the fact you will always be riding on them. And for crawling you are just as good off with the factory foam stops.

In all honesty it you would be better off jsut runnign 37's on 4" of lift with flat fenders giving your wheels and suspneison enough room to work in both directions.
Well, I am running 4" coils and 3" blocks now and I feel I get great travel now with the 37s for sure.

I want to keep the suspension mostly as-is and just trim the tub. It's not clear that I need to do any frame cutting. My drag link is flipped so I need the 3" blocks for that. The Fusion axle has a raised, but not flipped drag link so unless I hit something else, i might be able to get a little more up travel than I do now with the 3" blocks - at least in my tiny brain.

The King bump stops come with 3" blocks now so that should give them better useful range. I think the only time you use them without lower bump stops is on a stock height jeep. The adjustability will also let me fine tune the front bump stops to keep the tires away from the front fender support tang thingy. As far as I know, you can only go 3" of bump stop on the front from the axle otherwise the bump stop could come into contact with the spring. I have been told this by two reliable sources and this is why you need to add additional bump stop from the top anyway. I do hope to retain the 4" coils so maybe that gives me a little more compression than you are thinking.
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post #12 of 17 Old 12-01-2018, 08:48 AM
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Going from 37x12.5 tire to 40x13.5 tire wil cost you roughly 2" of up travel if you keep the suspenison the same and had the 37's set up correctly. This means you need 2" of additional bump stop.
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post #13 of 17 Old 12-01-2018, 09:31 AM
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Originally Posted by thedirtman View Post
This means you need 2" of additional bump stop.
Bump stop and/or tub trimming?

That's about the number I had in mind for trimming. I figure that with an increase of 1.5" in radius that 2" would be a safe number.

Right now, I am hoping to trim about 2" of sheet metal from being the front and rear tires as well as 2" from in front of the rear tire. All this with no more bump stop.
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post #14 of 17 Old 12-01-2018, 09:38 AM
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2" Bump stop plus lots of trimming.
The bumps are basically going to keep the tires out of the upper fender area and the frame/control arms. Your extra axle width will help out on the frame/control arms but not on the stuffed into the fenders clearacne. Your trimming is basically the body to account for the extra width of the tire.

40's look cool and will let unskilled drivers run over everything but they do have drawbacks and a lot of work to make them fit well.

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post #15 of 17 Old 12-01-2018, 10:52 AM
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Quote:
Originally Posted by thedirtman View Post
2" Bump stop plus lots of trimming.
The bumps are basically going to keep the tires out of the upper fender area and the frame/control arms. Your extra axle width will help out on the frame/control arms but not on the stuffed into the fenders clearacne. Your trimming is basically the body to account for the extra width of the tire.

40's look cool and will let unskilled drivers run over everything but they do have drawbacks and a lot of work to make them fit well.

Not that I had a problem with 37s. Ive said it before that life was good. Maybe too good on 37s. Good everything. Good road manners, good wheeling, good challenge. Easy to fit. They took me everywhere I wanted to go and then some.

Holding hands and first dates are way behind me now with respect to my relationship with 40s. Im fully committed to 71 tons and 4.5 BS beadlocks. Im already picking names for my first new beadlock.

Width-wise, I feel like I am in a good spot. At least on paper. I dont rub anything at all now with Nitto 37s. Metal Cloak arms are tucked in nicely, FWIW/FYI. Aired down MTR 37s with mud in the lugs kissed the frame slightly. It was a gently, kiss-your-sister kind of kiss, though. The MTRs measured slightly larger than the Nittos.

I gain 5.5 total width (71-65.5=5.5)

Cut that in half to 2.75

Going from 4 BS to 4.5 BS loses 0.5, so now its 2.25

40 tires are wider by 1 total. With an 8.5 wide Trail Ready @ 4.5 BS we can say I lose another 0.75 per side, leaving me with 1.5 of buffer there.

Seems decent.

Upward travel, whether it be both wheels or one at full stuff and the other at full droop, I can see trimming the wheel wells as we have been chatting about in another thread.

I am really happy with the way the current lift works so I want to stay as close to that as possible. It will be a fine line between bump stops and the Sawzall.

My go forward plan on the bump stops is this.

Setup the front with the adjustable Kings to something equivalent to the 3 bump blocks with OEM stops up top that I have now. If the front tire hits the metal front fender tab then I will tweak up the up the King bump stops to compensate. Beyond that, I will trim back the front fender. I will report back in January once the deed is done. I feel that adjustment with the Kings will be easy for me to do.

On the rear, I am going to leave the 3 bump stop in place and cut out the wheel well openings. If it turns out that I need to add some bump stop, Ill try to either bolt something onto the top of the fixed-height blocks or replace them with adjustables. Probably easier to just add some height to the 3-ers. Anyway, I have a Milwuakee Fuel Sawzall with an LED headlight and a fresh set of blades. Lets get jiggy. When Im done, well go with some tub-o-sealant.
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post #16 of 17 Old 12-01-2018, 11:12 AM
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You also need to add the change in height to the frame clearance as it moves your tire closer when turned so you wil be tirghter then you think and on the trail things will flex but I still think you will be ok on width.

Your shocks will have a lot to do with the overall fit and articulation as well as far as trimming goes especailly if you are planning on using the factory mount locations.

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post #17 of 17 Old 12-01-2018, 01:26 PM
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Quote:
Originally Posted by thedirtman View Post
You also need to add the change in height to the frame clearance as it moves your tire closer when turned so you wil be tirghter then you think and on the trail things will flex but I still think you will be ok on width.

Your shocks will have a lot to do with the overall fit and articulation as well as far as trimming goes especailly if you are planning on using the factory mount locations.
We'll see where I end up in January when I get all the parts, start putting it all together and begin hucking expletives.
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