I've had my 89 lowered about 2" for the last 2 years, and I like it. It looks good, drives good and rides good. My car has an aluminum head 350 and a t-5, so I just cut down a set of V-6 springs. I've got Bilstiens all around. But one item I want to improve on my next update is the rear bump stops for the rear axle. What I have on the car now is cut down stock ones. I basically cut the rubber in half to gain clearance. I had about 1.5" clearance before I cut, and now I've got about 3.5". I still see evidence of contact just with street driving.
Has anyone on the board worked through this problem? If I take the cut down bump stop off, I will gain less than an inch, and I know if I bottom, I'll tear something up. I think I need more clearance above the axle (cut out some metal) and relocate a good stock bump stop off to the side (pretty complicated). I'd just like to know what the rest of you have done in this area. Thanks in advance-

 

Should have cut down a set of V8 springs.

 

that helps...



i'm working on it myself right now as i've had to do the same thing to clearance my 295's with the air ride. when i figure it out i'll let you know, do the same.

 

The best one on the market is Koni # 70-34-53-000-0. Its 2 5/32" long and will compress 1 1/4" to a compressed height of 1 1/32". Heres the progress spring rate increase as it snubs (this will progressively increase your front spring rate as it motions towards bottoming out-not a harsh impact like the stock rubber bumpstops.

compress........rate increase
1/8".................30 lbs
1/4".................45
3/8".................60
1/2".................70
5/8".................85
3/4".................100
7/8".................110
1"....................145
1 1/8"..............195
1 1/4"..............260

stock units will only compress aprox 1/4" and immediately increase rate to 300 Lbs- very harsh.

Just slip the Koni bumpstops over your rear shock shaft then bolt the upper shockmount to the car chassis using the same groments. The bumpstop will just sit freely on the shaft.

 

Thanks for the info- but I think you are thinking the front. Using a jounce bumper there makes perfect sense. But I'm talking about the rear suspension. Sliding a jounce bumper over the rear shock absorber rod might work, but I'd rather not. The rear floor pan is not designed to take those type of loads. I think I need at least 4" of travel until I get to a high rate, and I can't get that with anything that mounts in the stock location. Does anybody else have any other ideas? Thanks

 

that would really solve my problem if that was how it worked. seems like alot of stress on that point though. can you clear it up?

 

I WAS talking about the rear, not the fronts- Your first clue was when I wrote: "Just slip the Koni bumpstops over your rear shock shaft "

What I don't get is nobody that runs front coilovers is concerned about the lack of strength of the front fenderwells holding the entire weight of the weavier front side of the car- but I suggest this being slipped onto the rear shock shaft and now there is nervousness? The rear upper shock mount is 2" away from the rear spring pocket which holds the blunt weight of the rear of the car. This bumpstop would only subsidise the load mildy if and only if the car travels towards bottoming out-and even then, the coilspring is still taking most of the load (2" away)

 

your a funny little man....

 

visxtoy- thanks for clearing up your message- I didn't understand. Maybe the jounce bumper on the rear shock absorber shaft would work. Is your car set up this way? One thing I would want to do is be sure the travel is right on the rear shock. You would want good support from the jounce bumper before the axle housing hits the underside of the body. If your car is already set up this way, then that would show that it would work. If not, and if the rear axle would hit first, then maybe I could fabricate a spacer to move the jounce bumper closer to the shock body. Thanks again for the idea.

 

I removed mine completely after they were pissing me off... no evidence of bottoming out after 30k miles. Seems to me that the wheels will hit the fender well before the bump stops hit... just a maybe though. I've been lucky. In the front I kept the bump stops stock and haven't had them bottom out. I'll probably put a piece of clay on the rear and be absolutely sure. You might want to do the same before removing them.

 

Little man huh Unlike like most that buy big toys to compensate for lack of other things- I drive a V6 and am very confident with my little manliness .

Mike, I run very low and my travel clearance of the Koni's on the rear are 3 1/16" to bottoming out at ride height. The factory bumpstop mount areas (bumpstops removed) has 3 5/8" clearance to the axle.

With the Koni bumpstops on the shaft (2 5/32 tall) I have a total of 3/4" free travel before the boumpstop starts to contact and gradually increase rate as shown above. I really don't travel more than 1 1/2" in the rear under the hardest circumstances at the shock points (1 3/4" at the outer tire edge). SO the rate increase I compress the bumpstop elevates the rate to about 100#.

My rear coil springs (progressive rate, springs trimmed slightly on the weaker coil side for slight lowering- 1" lowering to begin with) and the rate is aprox 175 at ride hieght and 225 at 1" lower

So at 1" compressed travel, my overall spring rate increases to 270#'s. 1 1/2" travel increases to 325#'s. Like I stated above, this car does not compression travel more than 1 1/2" in the rear under max conditions.

I also run aprox 820# coils on the front of a V6 car.

 

Frikin probation, can't edit-

Another added note to the above, I had to split the Koni bumpstops with a bandsaw (very carefully) in order to insert them onto the Koni shaft. The dustsheild mount spacer near the top of the Koni's is unremovable and I could not slip it onto the shaft without splicing. I then wrapped the upper circumfrence with electrical tape and reused the Koni black dustsheild boot to keep it from popping out of there sometime in the future unexpectedly. SO its actually hidden.

The original outer bumpstops are still in place, however, I trimmed them down to about 1" tall and tappered them accordingly just in case (alot of sanding)

 

would they work with bilsteins which are slightly larger in dia.?

 

I don't know the Dia of the Bilstiens. They Koni bumps are designed to work with .630" max dia shafts.

 

thanks, that is what i wanted to know...i'll measure them out. the housing dia would not matter correct if it slips over the shaft?

 

That is correct. They do fit underneath my dustshields. I like to keep them on the rear shocks because the Koni's have the adjuster button atop the housing where debris can corrode it over time, but the bumpstop does not affect the adjustment even if it does make contact because the Koni's need to be dismounted on one end and rotated after depressing it.

 

Thanks to all for the info. vsixtoy- one more question. If I understood- you said you had about 1.5" of wheel travel (measured at the shocks) on the rear. Do you have a measuring indicator on the shock shaft, or how do you know that? I would need to calculate what this translates to at the wheel. What I would like to accomplish with this next update is to get more wheel travel in an effort to improve the axle tramming I get on pavement peaks on the freeway (like when you are going on and off a bridge that doesn't match the roadway). I think I need more wheel travel (I know I'm getting about 3.5" at the factory bump stop). I will also work on reducing the friction in all the pivots in the rear suspension, and I'll have Bilstien do another calibration for the rear shocks. Also- where did you get your rear springs? Thanks again for all of the info.

 

The 1 1/2" travel is based on the location of the original factory bumpstops. I have aprox 2 1/2' " travel from axle to trimmed down factory bumpstop which do not touch the axle anymore. They did at one point until I installed the Koni Bumpstops.

I could tell when they made contact. I would be sitting through a corner and hit a dip or bump in the road and wham, it was like I had no suspension- I was grounding out against them. Don't have that problem anymore, Its now progressive and never a sudden halt in travel.

For the record, I have never felt another f-body suspension even close to a stiff as I run this car. You lean on the front end with all your weight and only the tires flex- otherwise no movement. The rear will depress about 1/2" max and I weight 240 lbs.. Most cars I can bounce up and down like a basketball even with sportlines and KYBs.

My coils are Suspension Spring Specialist- they have been in the car 12+ years

 

I try to link to this but it did't work so I'm bumping it TTT

 

I know this is an old thread but didn't want to start a new one since this question was already asked....

my question is the same, with my car lowered and the car sitting on flat pavement I have 1/2" to 3/4" travel until it hits the bumpstop (factory)....I was planning on cutting the bumpstop in half to increase travel but wanted to know if anyone has done anything else besides the overshock bumpstop (which doesn't sound like a bad idea) but just looking for any other ideas. Has anyone replaced the factory bumpstop with an aftermarket softer progressive one?? Or is there such a beast?? THanks guys.