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Discussion Starter #1
Looking for a lil help here guys...I got a 98 beautiful seville sts on 20" rims...i have never had a problem with this car but lately, i have noticed the back end saggin a lil lower than the front...you really cant tell the difference but i had two of my friends in the back this weekend and I could hear the tires rubbing against the wheel well whenever i hit a bump...no problems before and no problems with no one sittin in the back...no codes either...any help would be greatly appreciated...thanks
 

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I am having the same problem with my 2000 DeVille. There was no problem with the stock wheels. I now have 20's on mine as well. Visibly it doesn't look any different but when I take sharp turns or go over speed bumps I can hear the back wheels scraping. Last weekend I had people in the back seat for the first time and the scraping was even worse. Any advice on how to fix this would be greatly appreciated! I have to pick my grandparents up from the airport next week and need to be able to put them in the back seat!
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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At the very least you need to calculate the tire tread width, section width, height, overall diameter, offset, bolt circle, and rim width for the OEM stock setup. Then use a tire that, with 20" wheels, will very nearly duplicate the OEM measurements. Anything else is a wild guess. Your best bet ???? Go back to the stock wheels with the best V/Z rated tires you can find IN THE PROPER SIZE FOR THE CAR, as noted on the driver's door sticker. They'll cost less than the 20" mess you appear to have installed. If the car doesn't appear to have a slight forward rake, you also have rear ride height problems.
 

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'97 Seville STS
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Another thing to check is your air leveling suspension. I see a lot of Cady's rolling around riding low in back because the air-leveling is out. When I bought my car for example the air-leveling had been disabled.

Disabled or broken air-leveling will cause the rear to ride slightly low, but with stock wheels it can be tolerated.

A common thing to happen is to get an air leak in the rubber boot of the rear shock absorbers (boot is involved in air leveling). Listen if your leveling pump is on all the time. To make sure the pump isn't burned out, see if it can be heard shortly after the car is started. If not, the pump may be out, probably due to a leak in the shock boot.

If the pump works spray soapy water on the boot and look for bubbles. Of course all this can be done by mechanic too.

I'm disappointed in the previous answers. I think the previous answers drive more at the authors' opinions that 20's are a bad choice of wheel, rather than answering the question possed, which was possible causes for the lower than expected rear.

I do not like 20's on Cady's and I suspect they're detrimental to performance among other things. If you guys like your 20's nonetheless, it's your call, and the 20's are not necesarily the sole potential cause of the low ride.
 

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I'm disappointed in the previous answers. I think the previous answers drive more at the authors' opinions that 20's are a bad choice of wheel, rather than answering the question
It's not that 20's are necessarliy bad, just that all 20's, or other vanity, large size aftermarket setups I've ever seen have an offset that no matter what size tire you put on them , will scrape on the outside edge. It is worthwhile to check the level ride. I have even adjusted ride heights quite high in these scenarios to minimize rubbing, but you'll never get rid of it with this type of wheel / tire.
 

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Discussion Starter #7
Another thing to check is your air leveling suspension. I see a lot of Cady's rolling around riding low in back because the air-leveling is out. When I bought my car for example the air-leveling had been disabled.

Disabled or broken air-leveling will cause the rear to ride slightly low, but with stock wheels it can be tolerated.

A common thing to happen is to get an air leak in the rubber boot of the rear shock absorbers (boot is involved in air leveling). Listen if your leveling pump is on all the time. To make sure the pump isn't burned out, see if it can be heard shortly after the car is started. If not, the pump may be out, probably due to a leak in the shock boot.

If the pump works spray soapy water on the boot and look for bubbles. Of course all this can be done by mechanic too.

I'm disappointed in the previous answers. I think the previous answers drive more at the authors' opinions that 20's are a bad choice of wheel, rather than answering the question possed, which was possible causes for the lower than expected rear.

I do not like 20's on Cady's and I suspect they're detrimental to performance among other things. If you guys like your 20's nonetheless, it's your call, and the 20's are not necesarily the sole potential cause of the low ride.
Thank you for your unbiased answer...Like I said earlier, my car WAS fine and i WAS NOT having problems with my 20's EVER rubbing...However, I noticed that the compressor was not kicking on AFTER i heard it rub with about 650lbs of weight in my backseat..My question is, could it also be some type of "relay switch" and not the compressor?? I just want to make absolutely sure its the compressor before i drop $150 as opposed to $10 for the relay...Thanks again...

 

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Normally sagging rear ends are attributed to age :)

Seriously though. I think I've read here about a leveling sensor/switch. I would imagine you could test the output of it to the compressor. If you are not hearing the pump come on I suggest looking there before chasing a leak.
 

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Discussion Starter #9
how do i test the relay and where is it located...someone said something about putting a 9v battery to the relay and listening for a click??
 

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i had two of my friends in the back this weekend and I could hear the tires rubbing against the wheel well whenever i hit a bump...no problems before and no problems with no one sittin in the back...no codes either...
Daaaaammnn!! You have two friends that add up to 650lbs??!! And, you expect your Caddy to accomodate that! :) Just havin' fun, sort of.

These do have issues with the LR sensor that can cause level ride problems, but don't expect 650lbs in the back seat not to hit the tires over bumps or dips with those 20's........that's abuse!

Two people...650lbs..wow.
 

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Discussion Starter #11
hahahaha...thanks, i meant 550!! they r some pretty big dudes but not that BIG! where is the LR sensor located and how do i test it??
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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:confused: jvegas.......In your pic of the crimson pearl STS, compared to my identical (17") STS, your vehicle's rear is significantly lower. I believe you have a ride height problem somewhere, but no good advice.......just an observation to back up your sagging theory.....
 

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The sensor is inside the LR wheel well at the forward (or left side as you look at it). It is held on by one 10mm nut and has a link that extends down to the control arm. A short three wire pigtail comes out of it and goes under to the inside. If you have an ohmmeter, disconnect the sensor and watch the resistance across terminals A and B (I think) of the sensor side of the pigtail while slowly moving the disconnected link up and down. You should get a smooth change in resistance all of the way through from around 300 to around 900 ohms.
 

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Discussion Starter #14
thanks for the advice...pulled the code and i got a RSS C1378...any help with that one?? whats wrong?? thanks
 

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so if i have a leak in the boot would i be able to replace that, because my pump is always on and the back sags more and more as time goes by.
 

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so if i have a leak in the boot would i be able to replace that, because my pump is always on and the back sags more and more as time goes by.
That would require new struts if the boot is leaking. If the compressor has been running way too much for a long time, it is probably weak now. You'll need to have the pressure checked or do the struts and then see if the compressor can do its job.
 
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