Does anyone else's stock RX8 bottom out in rear on the mildest of speed bumbs?
02-06-2011, 12:06 AM
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Does anyone else's stock RX8 bottom out in rear on the mildest of speed bumbs?
I have a 2004 RX8 Touring Edition that feels like it bottoms out when I go over any bumps at all. Speed bumps at more than a crawls pace hit hard in the back... like teeth jarring hard. Even road construction where the pavement level jumps up an inch or so causes it to bottom. I've had a few shops look at it and they tell me the shocks seem fine & there are no visible leaks. The car only 70k miles on it, so they all say springs last a long time so they can't be the problem. 
I push down on the back end & it doesn't bounce whatsoever. It goes down, then immediately back to the starting position.
Does anybody know of stock coils getting soft extremely early or does what I described sound like it could actually be the shocks needing replacing? Could this be another problem?
I have parked on my uphill driveway for 6+ years. I'm wondering if the hill has put more weight on the back end & over time it's compressed the rear springs.
BTW - how can I measure how much sag there is in the back (such as wheel well to center of wheel measurement)?
I already bought Tein S springs to put on it but would like to find out beforehand if I should be replacing shocks while I'm at it too.
Sorry for the book... I'm just getting frustrated with people telling me they don't see a problem when I'm sure as hell feeling a problem.
I push down on the back end & it doesn't bounce whatsoever. It goes down, then immediately back to the starting position.
Does anybody know of stock coils getting soft extremely early or does what I described sound like it could actually be the shocks needing replacing? Could this be another problem?
I have parked on my uphill driveway for 6+ years. I'm wondering if the hill has put more weight on the back end & over time it's compressed the rear springs.
BTW - how can I measure how much sag there is in the back (such as wheel well to center of wheel measurement)?
I already bought Tein S springs to put on it but would like to find out beforehand if I should be replacing shocks while I'm at it too.
Sorry for the book... I'm just getting frustrated with people telling me they don't see a problem when I'm sure as hell feeling a problem.
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02-06-2011, 01:16 AM
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Thanks for the response but could you elaborate please? What is it that indicates it's a shock? Shouldn't it bounce after pushing down the back end if a shock is bad?
02-06-2011, 02:58 AM
#4
Sorry c0ldf1ame, I don't believe it is a shock. Shocks absorb the osculations of the movement of the wheel. Springs are what determine the ride height of the car.
csuttman, did you buy the car second hand? The previous owner could have put lowering springs on the car. I have done this to mine and I do scrub intermittently.
csuttman, did you buy the car second hand? The previous owner could have put lowering springs on the car. I have done this to mine and I do scrub intermittently.
02-06-2011, 03:39 AM
#5
Sydney, Australia
apart from the short version above - it IS a symptom of a blown shock and its not uncommon for the factory ones to 'go' at 40,000klms. They are a gas over oil type device - you may see physical symptoms like oil leaks, you may not, but go get any suspension place to check the car and you get the same conclusion.
Secondly - the RX-8 sags at the rear ANYWAY and with all due respect the the normal science of spring holding the weight and shocks doing the oscillation control, the RX-8 is somewhat wierd in that some of the weight seems to be controlled by the shocks themselves - perhaps hence the premature failure.
"I already bought Tein S springs to put on it but would like to find out beforehand if I should be replacing shocks while I'm at it too."
given the labour involved in the above - the short answer is why not at the same time!. Check out my posts here:
https://www.rx8club.com/series-i-wheels-tires-brakes-suspension-55/experiment-progress-im-interested-gauging-interest-possible-product-198139/
https://www.rx8club.com/showthread.php?t=198139
Secondly - the RX-8 sags at the rear ANYWAY and with all due respect the the normal science of spring holding the weight and shocks doing the oscillation control, the RX-8 is somewhat wierd in that some of the weight seems to be controlled by the shocks themselves - perhaps hence the premature failure.
"I already bought Tein S springs to put on it but would like to find out beforehand if I should be replacing shocks while I'm at it too."
given the labour involved in the above - the short answer is why not at the same time!. Check out my posts here:
https://www.rx8club.com/series-i-wheels-tires-brakes-suspension-55/experiment-progress-im-interested-gauging-interest-possible-product-198139/
https://www.rx8club.com/showthread.php?t=198139
02-06-2011, 11:05 PM
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alneilson,
That's the logic I've been using but am definitely having 2nd thoughts as to it's validity. I think I see now that when I hit a bump... if the damper is not doing it's job, the car will not rise with the bump in a timely manner, therefore bottoming out if the bump is big enough.
sarras,
Very interesting discovery with the Koni's. Were you able to verify if the Koni perch is in fact lower when off the car & next to another shock? That makes me wonder which shocks have their own drop built in... causing the double drop effect with lowered springs. I also just want the .8" drop so hope the shocks I buy are standard height so the springs handle the drop alone. I've seen the name Bilstein HD's all of this forum & they seem to be inexpensive in comparison to many others. I'm on a strict budget, so cheap while still having a decent firmness & better than average lifespan is what I'm after.
So now that I've decided to do the shocks too... the question becomes "do the Bilstein HD's cause an additional drop like the Koni's or should I be looking at another?
BTW - Thanks to everyone that is so helpful on this site. May much good Karma come your way.
That's the logic I've been using but am definitely having 2nd thoughts as to it's validity. I think I see now that when I hit a bump... if the damper is not doing it's job, the car will not rise with the bump in a timely manner, therefore bottoming out if the bump is big enough.
sarras,
Very interesting discovery with the Koni's. Were you able to verify if the Koni perch is in fact lower when off the car & next to another shock? That makes me wonder which shocks have their own drop built in... causing the double drop effect with lowered springs. I also just want the .8" drop so hope the shocks I buy are standard height so the springs handle the drop alone. I've seen the name Bilstein HD's all of this forum & they seem to be inexpensive in comparison to many others. I'm on a strict budget, so cheap while still having a decent firmness & better than average lifespan is what I'm after.
So now that I've decided to do the shocks too... the question becomes "do the Bilstein HD's cause an additional drop like the Koni's or should I be looking at another?
BTW - Thanks to everyone that is so helpful on this site. May much good Karma come your way.
02-06-2011, 11:15 PM
#7
First of all, you spelled my name wrong.
When I go over a bump, that I think is too big, I go at a dead slow pace and may bottom out. That is because of the lowering springs. If you are bottoming out at a faster pace, where you wouldn't at a slow speed, then that could be a shock.
Bilstein & KYB are high pressure shocks. I put them on a previous car and it actually gained ride height. Koni & Tokico are low pressure shocks. The ride height shouldn't change when using them as a replacement shock with OEM springs.
When I go over a bump, that I think is too big, I go at a dead slow pace and may bottom out. That is because of the lowering springs. If you are bottoming out at a faster pace, where you wouldn't at a slow speed, then that could be a shock.
Bilstein & KYB are high pressure shocks. I put them on a previous car and it actually gained ride height. Koni & Tokico are low pressure shocks. The ride height shouldn't change when using them as a replacement shock with OEM springs.
02-06-2011, 11:57 PM
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alnielsen,
Sorry about the misspelling. I have a name that everyone misspells so I, of all people, should know better.
When I say I'm "bottoming out"... what I mean is that the bump-stop is being hit hard. Not sure from your response if you may have thought the car frame is hitting the bump. Sorry for any confusion.
One of the bumps I hit daily is a pavement level change where construction is being done at the end of a highway off ramp. I assume the pavement goes up maybe 1 to 1.5 inches & I'm traveling at 40-50 mph. The back end goes "thud" hard when I hit it... which is what makes me think the rear must be sagging for a < 1.5" bump to cause it to bottom out on the bump-stops. I would think the suspension would allow for more than 1.5 inches of travel.
The info you've given about the different brands being high or low pressure shocks is great information. The Bilsteins I'm looking at will be paired with Tein lowering spriings I already purchased & I'm hoping to get the .8 inch lower like the springs say they do & the shocks won't have a ride height effect one way or another of their own.
Sorry about the misspelling. I have a name that everyone misspells so I, of all people, should know better.
When I say I'm "bottoming out"... what I mean is that the bump-stop is being hit hard. Not sure from your response if you may have thought the car frame is hitting the bump. Sorry for any confusion.
One of the bumps I hit daily is a pavement level change where construction is being done at the end of a highway off ramp. I assume the pavement goes up maybe 1 to 1.5 inches & I'm traveling at 40-50 mph. The back end goes "thud" hard when I hit it... which is what makes me think the rear must be sagging for a < 1.5" bump to cause it to bottom out on the bump-stops. I would think the suspension would allow for more than 1.5 inches of travel.
The info you've given about the different brands being high or low pressure shocks is great information. The Bilsteins I'm looking at will be paired with Tein lowering spriings I already purchased & I'm hoping to get the .8 inch lower like the springs say they do & the shocks won't have a ride height effect one way or another of their own.
02-07-2011, 06:34 AM
#11
Sydney, Australia
alneilson,
That's the logic I've been using but am definitely having 2nd thoughts as to it's validity. I think I see now that when I hit a bump... if the damper is not doing it's job, the car will not rise with the bump in a timely manner, therefore bottoming out if the bump is big enough.
sarras,
Very interesting discovery with the Koni's. Were you able to verify if the Koni perch is in fact lower when off the car & next to another shock? That makes me wonder which shocks have their own drop built in... causing the double drop effect with lowered springs. I also just want the .8" drop so hope the shocks I buy are standard height so the springs handle the drop alone. I've seen the name Bilstein HD's all of this forum & they seem to be inexpensive in comparison to many others. I'm on a strict budget, so cheap while still having a decent firmness & better than average lifespan is what I'm after.
So now that I've decided to do the shocks too... the question becomes "do the Bilstein HD's cause an additional drop like the Koni's or should I be looking at another?
BTW - Thanks to everyone that is so helpful on this site. May much good Karma come your way.
That's the logic I've been using but am definitely having 2nd thoughts as to it's validity. I think I see now that when I hit a bump... if the damper is not doing it's job, the car will not rise with the bump in a timely manner, therefore bottoming out if the bump is big enough.
sarras,
Very interesting discovery with the Koni's. Were you able to verify if the Koni perch is in fact lower when off the car & next to another shock? That makes me wonder which shocks have their own drop built in... causing the double drop effect with lowered springs. I also just want the .8" drop so hope the shocks I buy are standard height so the springs handle the drop alone. I've seen the name Bilstein HD's all of this forum & they seem to be inexpensive in comparison to many others. I'm on a strict budget, so cheap while still having a decent firmness & better than average lifespan is what I'm after.
So now that I've decided to do the shocks too... the question becomes "do the Bilstein HD's cause an additional drop like the Koni's or should I be looking at another?
BTW - Thanks to everyone that is so helpful on this site. May much good Karma come your way.
Having googled this issue of the Konis massively, and long chats with my mechanic (who has after all, now done two sets of springs with the Konis on the same car), and indeed Lovells, who went to amazing lengths to build the custom springs to an exact aspirational specification - its my opinion that Koni Goofed with the perch height on the RX-8 specs. The ultimate test would be to compare measurements of the Konis with say, a set of Bilsteins when all shocks were off the car, but the on-car results definitely point to a miscalculation on the perch position with the Konis.
This has been an horrendously expensive experience for me (we pay dearly for such parts in Oz) and it all started with the thumping/bottoming out sensation you're experiencing over speed bumps and the like - hence my assured belief that your shocks are shot as such. In the end though, I have an amazing suspension setup - its tight and lean, but doesn't bottom out even with 4 large people in the car and its very stable and smooth at cruising speeds - not choppy and bobbing about like with the Teins. To compare apples and oranges - what I have now feels very much like my Boss's Maserati GranSport and that thing cost over $200,000 when it was new - so in the end I'm very happy with the final result.
Last edited by SARRAS; 02-07-2011 at 06:45 AM.
02-07-2011, 12:02 PM
#13
csuttman,
My 07 GT did exactly what you describe from day one.
I tracked it about 7 times, and even could see the rear flex a couple inches in the HPDE pics, but the way I fixed it was to realign the suspension.
The rears tend to have too much camber (mine was over -2.1), so you need to try for about -1.5 rear camber on both rears and zero toe.
My right rear would only go down to -1.65 camber, so I made both rears that, and I don't hear or feel anything wrong with the rears anymore.
Maybe with the high neg camber the shocks are not pushing straight and binding inside.
That's the theory I got.
My 07 GT did exactly what you describe from day one.
I tracked it about 7 times, and even could see the rear flex a couple inches in the HPDE pics, but the way I fixed it was to realign the suspension.
The rears tend to have too much camber (mine was over -2.1), so you need to try for about -1.5 rear camber on both rears and zero toe.
My right rear would only go down to -1.65 camber, so I made both rears that, and I don't hear or feel anything wrong with the rears anymore.
Maybe with the high neg camber the shocks are not pushing straight and binding inside.
That's the theory I got.
02-09-2011, 06:52 AM
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sassas,
That sounds like you've had a marketable product created. Can you find out what Lovells would charge for shipping to the US... so others here could weight the pros & cons of going that route? Personally, I still do want the .8" drop for the looks so that won't be my route. Great info though!
red,
Wouldn't adjusting the camber like that affect the tire wear?
That sounds like you've had a marketable product created. Can you find out what Lovells would charge for shipping to the US... so others here could weight the pros & cons of going that route? Personally, I still do want the .8" drop for the looks so that won't be my route. Great info though!
red,
Wouldn't adjusting the camber like that affect the tire wear?
02-09-2011, 07:12 AM
#15
Sydney, Australia
sassas,
That sounds like you've had a marketable product created. Can you find out what Lovells would charge for shipping to the US... so others here could weight the pros & cons of going that route? Personally, I still do want the .8" drop for the looks so that won't be my route. Great info though!
red,
Wouldn't adjusting the camber like that affect the tire wear?
That sounds like you've had a marketable product created. Can you find out what Lovells would charge for shipping to the US... so others here could weight the pros & cons of going that route? Personally, I still do want the .8" drop for the looks so that won't be my route. Great info though!
red,
Wouldn't adjusting the camber like that affect the tire wear?
Lovells themselves don't see it as a marketable product though they do a regular line in stiffer, dropped springs for the RX-8, but those even are slow sellers as I suspect most modders here are going for Japanese springs.
So then I asked about Batch pricing. If I did a batch run I could get the price down to about $US750 including shipping to the States but I'd need a dozen orders to get that sort of price and even then its more than twice the price of things like Teins. So the idea is wonderful, but reality is its just way too expensive for the market.
Having said that - my friend mentioned above took my car, her car, and another experienced driver for a long run in the two cars back to back over a whole series of roads north of Sydney and came home raving about the difference and immediately we ordered her a set at $900 - which proves my original theory that the RX-8 doesn't so much need lowering as it needs stiffening! That's my end opinion - Mazda made it too soft in the springs.
If anyone REALLY desperately wants a set I can get them done for you - its about $900 plus shipping and it takes on average 2 months from order to delivery. Get some friends - lots of them - and it gets a bit cheaper but still takes a couple of months for delivery.
Last edited by SARRAS; 02-09-2011 at 07:22 AM.
02-09-2011, 07:48 AM
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Just placed my order for Bilstein HD's... then stumbled upon this thread about HD's vs Sport. Went to the bilstein site & confirmed the sports are for lowered springs. I didn't even know sports existed... everyone seems to sell the HD's or standard only. I'm searching for sports now & will likely call & cancel my order for HD's.
http://forums.bimmerforums.com/forum....php?t=1116456
http://forums.bimmerforums.com/forum....php?t=1116456
02-09-2011, 11:02 AM
#17
No, wrong camber doesn't wear the tire as much as wrong toe, and I'm lessening the camber in the rear anyway.
Everybody here keeps chasing the suspension, but the alignment made it a whole new animal.
I run 40psi on 225/40r18 Hankooks, and drive as I want on speed bumps whether in the big box parking or the track.
The alignment actually picked up the rear slightly so it works right now.
If the rear ever sags I'll put on bilsteins then.
Everybody here keeps chasing the suspension, but the alignment made it a whole new animal.
I run 40psi on 225/40r18 Hankooks, and drive as I want on speed bumps whether in the big box parking or the track.
The alignment actually picked up the rear slightly so it works right now.
If the rear ever sags I'll put on bilsteins then.
Last edited by REDRX3RX8; 02-09-2011 at 11:12 AM.
02-09-2011, 11:53 AM
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Crap. I know I screwed up but tried to fix it as quickly as I could. I went with the cheapest price I could find online and am kicking myself now. Parts Geek has no phone support, only online tickets. This is the crappy response I got within hours of placing the order. I then received a tracking number 30 minutes after this email from them. UPS does not have the number in their system yet... so they haven't scanned it in yet.
My recommendation... always buy from a company with known good cutomer service. I will never buy from this place again.
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subject[######] Need to cancel my order
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Chris,
A customer support staff member has replied to your support request, ###### with the following response:
We regret to inform you that we cannot cancel orders once they are placed as indicated on our website and order confirmation e-mails. You can either refuse the package upon receipt or contact us for an RMA to return the product. Please be aware that there will be a 15% restocking fee applied to your return.
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My recommendation... always buy from a company with known good cutomer service. I will never buy from this place again.
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from Parts Geek Sales Dept <parts@partsgeek.com>
dateWed, Feb 9, 2011 at 11:18 AM
subject[######] Need to cancel my order
hide details 11:18 AM (1 hour ago)
Chris,
A customer support staff member has replied to your support request, ###### with the following response:
We regret to inform you that we cannot cancel orders once they are placed as indicated on our website and order confirmation e-mails. You can either refuse the package upon receipt or contact us for an RMA to return the product. Please be aware that there will be a 15% restocking fee applied to your return.
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02-09-2011, 12:49 PM
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So, if I were to keep the Bilstein HD's & used them with the shorter Tein springs I already have... I assume it would destroy the shocks since they are made for full length springs & apparently do part of the support work. So instead of working with the spings, they would be doing the bulk of the work. Does that logic sound correct?
02-09-2011, 10:14 PM
#21
You bought the right shock because its a gas shock like whats on the car.
Several people have and or are running the S-Tech Bilstein combo.
i had a set of S-Techs in the box ready to pair with Bilsteins, but traded after hearing about sagging.
If I ever need shocks, I'll put Bilstein with stock springs; I like to make what was designed work first since it's the best I've seen, and I don't need racing compromises.
Several people have and or are running the S-Tech Bilstein combo.
i had a set of S-Techs in the box ready to pair with Bilsteins, but traded after hearing about sagging.
If I ever need shocks, I'll put Bilstein with stock springs; I like to make what was designed work first since it's the best I've seen, and I don't need racing compromises.
05-11-2011, 09:25 PM
#22
I have the same issue as the original poster, so I had a new set of Koni yellows installed today, and I still am scraping something towards the middle of the car until I get the rears up onto the speed bump. I had hoped that the problem was dead OEM shocks (my RX-8 has over 55K miles and they were the original shocks installed in 2004); but the Konis failed to resolve the issue, so I am wondering if my rear springs may be defective. I had considered getting the 2009+ spec rear Konis instead of the 2003-2008 version because of the altered spring perch; but had been warned that I might blow the shock prematurely. Consequently, I am still in need of a solution. One suggestion which I have not yet tried but soon will be, is those hourglass shaped rubber inserts that go in between the steps of the coils, although I consider that something of a desperation move on my part. Does anyone else have any other suggestions?
05-11-2011, 10:20 PM
#23
Sydney, Australia
I have the same issue as the original poster, so I had a new set of Koni yellows installed today, and I still am scraping something towards the middle of the car until I get the rears up onto the speed bump. I had hoped that the problem was dead OEM shocks (my RX-8 has over 55K miles and they were the original shocks installed in 2004); but the Konis failed to resolve the issue, so I am wondering if my rear springs may be defective. I had considered getting the 2009+ spec rear Konis instead of the 2003-2008 version because of the altered spring perch; but had been warned that I might blow the shock prematurely. Consequently, I am still in need of a solution. One suggestion which I have not yet tried but soon will be, is those hourglass shaped rubber inserts that go in between the steps of the coils, although I consider that something of a desperation move on my part. Does anyone else have any other suggestions?
05-12-2011, 07:26 AM
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My issues are fixed & I'm happy again. I now have Tein S's and Koni Yellow's. The car is lower by about an inch and looks much better than stock (low & wide) and it sticks to the ground like magic on hard corners (where I used to slide). Here's what I learned in the process of dealing with this.
Obviously something is worn in the suspension & needs replacing, so whether it's the springs or dampers doesn't matter. Replace both while you're at it. Springs are cheap & stock dampers definitely have a limited lifespan.
The replacement springs are progressive whereas the stock ones didn't seem to be. Small bumps are handled with softness & bigger bumps compress more and get into the firmness. Overall... better ride & makes sense to me.
Fully adjustable shocks that don't need to be removed to adjust them (back only) would have been nice & may have been worth the money (to me). The front Koni's are adjustable while on the car though, and those are the one's I'd probably stiffen up temporarily if autocrossing, so I'm happy with my purchase.
The lowering is working out fine for me, but I live in South Florida where roads are pretty smooth & level. If I still lived in a potholed region... I think the stock height would have made more sense. The ride height alone isn't enough to make a noticable performance difference. Drop for looks only.
Hope this helps someone.
Obviously something is worn in the suspension & needs replacing, so whether it's the springs or dampers doesn't matter. Replace both while you're at it. Springs are cheap & stock dampers definitely have a limited lifespan.
The replacement springs are progressive whereas the stock ones didn't seem to be. Small bumps are handled with softness & bigger bumps compress more and get into the firmness. Overall... better ride & makes sense to me.
Fully adjustable shocks that don't need to be removed to adjust them (back only) would have been nice & may have been worth the money (to me). The front Koni's are adjustable while on the car though, and those are the one's I'd probably stiffen up temporarily if autocrossing, so I'm happy with my purchase.
The lowering is working out fine for me, but I live in South Florida where roads are pretty smooth & level. If I still lived in a potholed region... I think the stock height would have made more sense. The ride height alone isn't enough to make a noticable performance difference. Drop for looks only.
Hope this helps someone.
