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Anyone on here running a real coil over rear setup?

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TomK
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Anyone on here running a real coil over rear setup?

Post by TomK » Fri Nov 10, 2017 9:03 pm

Beedub wrote: Fri Nov 10, 2017 8:53 pm wow big money..... !!
It's fantastic kit.
Ordering process
Intrax wrote: As you already know, all our shocks are custom made. We only start producing after we have enough information about the car, wishes of the driver and of course after order.
Things we would like to know are:
For what purpose will your car be used (street, trackday, race, rally etc. or a combination)?
What type and size tire will the car drive on?
What size rim do you use?
Any other change (compared to standard) on the car that can influence the handling of the car (weight, power, roll cage etc)?
MC[IB], CSL airbox, Schrick 288/280 cams, 4.44FD, UUC SSK, SS race cat back, AP CP9660[F]/5144[R] brakes, Apex ARC-8 with AR-1 or PS5, KW ClubSport 2-way, Turner spherical arms, PMC uniball rtab, VB engine mounts, Rogue pulleys & RSMs, Tillett B6, half cage

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GuidoK
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Anyone on here running a real coil over rear setup?

Post by GuidoK » Fri Nov 10, 2017 10:07 pm

TomK wrote: Fri Nov 10, 2017 7:35 pm

I'm not sure though that the e46 subframe issue is such a great analogy for the forces involved here? I do though agree that getting access to fix any spot welds etc issues around that area is going to be an issue.

Its a fine example to show that load bearing issues are not always apparant in the first1-2 years or 5k miles.
And also a fine example of the possible extend of damage.
Its not said that the first signs of damage will be a small crack in the top of the shock perch easily welded up. It can just as well be a row of spotwelds somewhere down low where the side/shockperch is welded into the bottom plate which can be really hard to get to.
Is it also really a potential issue that a load is subjected constantly as you suggest? I would have thought that would not be a problem as long as it is within tolerance?
Well, the tolerance is just the issue isnt'it? What is the tolerance?
In the stock configuration the rear shock tower doesnt get any constant load. Its just there to hold the shock, that dampenes motion.
The shock doesnt resist the force of bumps and such; thats the task of the spring. The shock slowly dissipates energy.
In the normal situation the weight of the car sits on the spring perch underneath, not on the shock tower.
About the tolerance thats very very hard to predict. I'm sure bmw makes a computer model that stress tests all welds etc but based on the stock situation. If the coilover situation holds and doesnt break immediately that doesnt mean in a few years there wont be any issues.
I dont know if you know what a Wöhler curve is, but thats basically a curve that dictates that increased loads will accelerate stress fails. It's a life cycle curve (used in material sciences studies). And its logaritmic/exponential, so a linear increase in load will have an exponential accelerated failure rate.
But that makes it also very difficult to predict. There might be failure in 3 years or 30 years. It's a personal decision if one is willing to take that risc. There is no real user experience. There is no one saying: hey, I installed that kit 7 years ago and did 60k miles since then without any problems. People who buy those kits are low mileage users. Going to shows and trackdays.
But there are plenty of people who daily their car for years on normal coilovers like kw/hr/etc that did serious miles.
That is the only information you can go on really. Failure rate of others who've done serious miles.
Someone who's selling the product assuring its ok only has a value if he can give a no questions unlimited warranty on shocks and chassis for a representative time in relation to how long you want to hold on to the car.
Z4 3.0i | ESS TS2+ | Quaife ATB LSD | Brembo/BMW performance BBK front/rear | Schrick FI cams | Schmiedmann headers+cats | fully polybushed | Vibra-technics engine mounts | H&R anti rollbars | KW V3 coilovers | Sachs Race Engineering clutch

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TomK
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Anyone on here running a real coil over rear setup?

Post by TomK » Fri Nov 10, 2017 10:34 pm

GuidoK wrote: Fri Nov 10, 2017 10:07 pm
TomK wrote: Fri Nov 10, 2017 7:35 pm

I'm not sure though that the e46 subframe issue is such a great analogy for the forces involved here? I do though agree that getting access to fix any spot welds etc issues around that area is going to be an issue.

Its a fine example to show that load bearing issues are not always apparant in the first1-2 years or 5k miles.
And also a fine example of the possible extend of damage.
Its not said that the first signs of damage will be a small crack in the top of the shock perch easily welded up. It can just as well be a row of spotwelds somewhere down low where the side/shockperch is welded into the bottom plate which can be really hard to get to.
Is it also really a potential issue that a load is subjected constantly as you suggest? I would have thought that would not be a problem as long as it is within tolerance?
Well, the tolerance is just the issue isnt'it? What is the tolerance?
In the stock configuration the rear shock tower doesnt get any constant load. Its just there to hold the shock, that dampenes motion.
The shock doesnt resist the force of bumps and such; thats the task of the spring. The shock slowly dissipates energy.
In the normal situation the weight of the car sits on the spring perch underneath, not on the shock tower.
About the tolerance thats very very hard to predict. I'm sure bmw makes a computer model that stress tests all welds etc but based on the stock situation. If the coilover situation holds and doesnt break immediately that doesnt mean in a few years there wont be any issues.
I dont know if you know what a Wöhler curve is, but thats basically a curve that dictates that increased loads will accelerate stress fails. It's a life cycle curve (used in material sciences studies). And its logaritmic/exponential, so a linear increase in load will have an exponential accelerated failure rate.
But that makes it also very difficult to predict. There might be failure in 3 years or 30 years. It's a personal decision if one is willing to take that risc. There is no real user experience. There is no one saying: hey, I installed that kit 7 years ago and did 60k miles since then without any problems. People who buy those kits are low mileage users. Going to shows and trackdays.
But there are plenty of people who daily their car for years on normal coilovers like kw/hr/etc that did serious miles.
That is the only information you can go on really. Failure rate of others who've done serious miles.
Someone who's selling the product assuring its ok only has a value if he can give a no questions unlimited warranty on shocks and chassis for a representative time in relation to how long you want to hold on to the car.
Thanks, again all good points.
The only thing is in this case Intrax or Nitron sell both a full coilover rear and if you like a separate barrel/damper arrangement, there is no difference in price and no (monetary gain) reason to overly sell me one way or the other. They say the coilover is better for my situation, but like you say I will never get any kind of guarantee out of them for the chassis nor would I expect them to.
MC[IB], CSL airbox, Schrick 288/280 cams, 4.44FD, UUC SSK, SS race cat back, AP CP9660[F]/5144[R] brakes, Apex ARC-8 with AR-1 or PS5, KW ClubSport 2-way, Turner spherical arms, PMC uniball rtab, VB engine mounts, Rogue pulleys & RSMs, Tillett B6, half cage

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GuidoK
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Anyone on here running a real coil over rear setup?

Post by GuidoK » Sat Nov 11, 2017 12:09 am

TomK wrote: Fri Nov 10, 2017 10:34 pm They say the coilover is better for my situation
Better what?
Better handling (I dont doubt that) or better life expectancy of your chassis welds?
Its a decision only you can make. Its your car. Everyone is willing to risk different things.
I'm usually willing to risk a lot of mechanical things because I know I can fix them easily and usually cheaply. But when it comes to the body/chassis, I have a totally different approach. Maybe if my pockets were really deep it wouldnt be an issue, but alas they aint :roll:
Z4 3.0i | ESS TS2+ | Quaife ATB LSD | Brembo/BMW performance BBK front/rear | Schrick FI cams | Schmiedmann headers+cats | fully polybushed | Vibra-technics engine mounts | H&R anti rollbars | KW V3 coilovers | Sachs Race Engineering clutch

gazpat
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Anyone on here running a real coil over rear setup?

Post by gazpat » Fri Nov 24, 2017 2:10 pm

Hi TomK,

Re. running 'real' rear coilovers, I posted the note below in a thread a while back, not sure how to link it to this thread. I haven't done loads of miles since the install due to working away from home and a recent hand injury preventing me from driving, but all good so far. I wasn't aware of potential design/loading issues with the rear strut towers (Centre Gravity didn't voice any concerns), i'll repost when the arse falls out of my car lol!

Cheers.

Gaz.

Earlier post:

Apologies in advance for my lack of involvement on here, I'm not a great one for posting on forums.

Just thought I'd reply to Muckinonthesofa's comment "These cars must be incredible with the top of the range coil over kits fitted!"

Well, I had a set of Nitron coilovers fitted to my roadster and set up by Centre Gravity last week. Done a couple of hundred miles since, and I can say it's completely transformed the car.

I found the standard setup harsh and crashy over bumps and poorly surfaced roads, and the front end was a bit vague especially during hard acceleration. Now, all the old cliches can be rolled out. It's completely planted, stable, on rails etc, I can feel exactly what the car is doing. It's still firm, but the crashing over bumps has gone. It's a different car.

I specified that I wanted to keep the standard ride height, and have it set up for real world road conditions, and Centre Gravity have delivered this requirement perfectly IMO.

Only 'downside'?....well... it did cost a shedload of cash....but was it worth it?... most certainly yes... the best money i'll ever spend on this car for sure....

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