Anyone on here running a real coil over rear setup?

[TomK]

After strut tower advice/thoughts please...

 

[Beedub]

you'll need some sort of reinforcement , the rear strut tower was never designed to take the additional loads. Ideally id want to tie a roll cage to it, or some sort of half cage.

Their some really fantastic options using the separate damper and barrel spring, MCS is one of them, nitron, Clubsports...


whats you reasoning for wanting to go this route and what gains are you hoping to achieve?

 

[TomK]

Well to me the big gain is that the spring can be much softer and therefore far more progressive. Also there are tons more options available for different spring rates with that kind of design, with the barrel you're kind of limited.
Nitron, I've looked at, and they suggest the full coil over as does intrax (which I'm currently favouring). I spoke with them today and they have not heard of a failure on a Z4M setup like that yet, admittedly there's probably very few out there though!

Eta, not clear but I would love to hear from someone who has done it without a cage, I suspect I'll be waiting a while though :tumbleweed emoji:

 

[Beedub]

Well to me the big gain is that the spring can be much softer and therefore far more progressive. Also there are tons more options available for different spring rates with that kind of design, with the barrel you're kind of limited.
Nitron, I've looked at, and they suggest the full coil over as does intrax (which I'm currently favouring). I spoke with them today and they have not heard of a failure on a Z4M setup like that yet, admittedly there's probably very few out there though!

Eta, not clear but I would love to hear from someone who has done it without a cage, I suspect I'll be waiting a while though :tumbleweed emoji:

its pretty much a no no without some real enforcement back their... Simpson have done a few of these conversions so maybe drop them a line. i don't think I've ever seen one without a cage or some sort of weld in piece tbh, and very few seem to stray from the stock layout as it works so well once sorted with top level items.

i look forward to seeing this thread develop however. After seeing this area on my own car many a time their just isn't enough material their to take this load imo.

Great thread however, wish we had more like it.

 

[TomK]

Yes I think you might be right (if perhaps only in terms of peace of mind), but Intrax say it is not necessary (but won't guarantee that!) and I know of many e46s which face the same predicament and it being fine for them too. The RSMs are pretty fancy with them, I'm awaiting thoughts from simpsons funnily enough
I wonder whether adding something like this in might help matters without welding http://www.wiechers-sport.de/en/shop/dom-fahrwerkstreben/produkte/df-bmw-z4-e86-fahrwerkstrebe-alu-hinten-detail
Otherwise I guess I'm looking at something like this

 

[bradz]

There is a nice chap called Scott Weeks on the Z4 facbook group that runs Gaz rear coil-overs on his Coupe, Hes been running them for a while without issue...

Send him a message and say Adam sent you, he will be more than happy to tell you all about them, I was very tempted to try some as the rear end on the coupe does look pretty solid... but I still wasn't sure enough to take the plunge.

 

[TomK]

I wasn't aware Gaz made a true coilover for the rear of these cars? Are you sure?
For reference pretty much all the 'coilovers' available for these are not a real coil over at the rear, they have a separate barrel spring and adjustable damper much like the OEM setup.
All KW(v2,3,clubsport), BC, etc run this. 3 or 4 companies that I know of make what I'm after, but they're many multiples of GAz normal stuff pricing.
Pm please his details if possible if they are a proper coil over, I'd be keen to hear his thoughts. Thanks
Is it an M coupe or regular? The setup is different, but still I'm interested in how he's got on with/without reinforcement.

 

[Machine monkey]

Nitron do a kit? They are local to me and make only the best kit! Not cheap and I am not sur if this is a generic kit or not? Call them and ask.

 

[TomK]

Yes, as said above, I've been speaking with them. Cheers
Like intrax they do a kit like that or one for the pussies with the barrel damper arrangement :lol:
tbh I think I'll probably end up going down the pussy route let's see

 

[bradz]

They do but I don't think its available off the shelf.

I know what a coilover is... Its on a Si Coupe.

I did have a picture, but I can't find it at the moment.

 

[TomK]

They do but I don't think its available off the shelf.

I know what a coilover is... Its on a Si Coupe.

I did have a picture, but I can't find it at the moment.

Cheers, sorry didn't mean to sound condescending but the amount of times I see people refer to an adjustable set up as a 'coilover' made me want to clarify
Interested very much to see how he's gone about it, if you could put me in touch some how that'd be great, thanks

 

[bradz]

No worrys.

 

[Machine monkey]

Yes, as said above, I've been speaking with them. Cheers
Like intrax they do a kit like that or one for the pussies with the barrel damper arrangement :lol:
tbh I think I'll probably end up going down the pussy route let's see

Whoops my mistake skim reading.

You may just have to find a good race company. And get somthing made and welded in. I can recomend a really good fabricator if you go that route. He builds some great stuff.

 

[GuidoK]

I think the main risk is that there is no real userexperience regarding if the chassis can hold a coilover or not without severely stiffening up the suspension.
There might be some people driving around with true rear coilovers, but how many miles did they do? What does it take to regard something as 'properly tested'? 5 cars having done 10k miles or 50 cars having done 100k miles? Im sure the last one doesnt fit the true coilover community.
It's very hard to predict if using true coilovers at the rear will damage the chassis or not.
But if you look at for example the e46 m3 subframe cracks what can happen if forces are not properly dealt with, thats not something you want to experience (and who's to say that things wont get even worse)
With normal coilover sets (kw/h&r/etc) with the conventional rear setup there are so many users that have done so many miles with it, that its pretty safe to say that that doesnt give any problems (although I have seen pictures of even front chassis perches/towers cracking due to stiffer springs)

 

[Beedub]

good input their from above.

yes i once saw a pic of the z4 with a ballooned Front turret using the kw club sport since having mine on I've made sure to run the underside reinforcement plates and the SB , between these two i feel pretty confident in the additional strenthening.

 

[TomK]

I think the main risk is that there is no real userexperience regarding if the chassis can hold a coilover or not without severely stiffening up the suspension.
There might be some people driving around with true rear coilovers, but how many miles did they do? What does it take to regard something as 'properly tested'? 5 cars having done 10k miles or 50 cars having done 100k miles? Im sure the last one doesnt fit the true coilover community.
It's very hard to predict if using true coilovers at the rear will damage the chassis or not.
But if you look at for example the e46 m3 subframe cracks what can happen if forces are not properly dealt with, thats not something you want to experience (and who's to say that things wont get even worse)
With normal coilover sets (kw/h&r/etc) with the conventional rear setup there are so many users that have done so many miles with it, that its pretty safe to say that that doesnt give any problems (although I have seen pictures of even front chassis perches/towers cracking due to stiffer springs)

Yes I agree with your points, it's an unknown to some extent. Intrax engineers suggest that on a street set-up (which mine will be) there is no need to reinforce as the spring rate will be soft. On a race spring set-up then they say reinforcement will be necessary. There are a number (how many I don't know!) of Z4Ms running around europe in this configuration with no issues that they have yet heard of.
Simpsons who install a lot of intrax stuff into e46m3s have done many without cage/reinforcement and have yet had a rear turret failure. But as you say, who knows how many miles and how long these cars are run, will the metal fatigue badly over time, not to mention that's a different chassis?
I think the front towers cracking come from yes stiffer springs but also the adjustable solid mount camber plates often used. As beedub suggests you should probably run the bmw reinforcement plates if you're running those.
Guido, do you think the rear strut brace or similar I linked at the beginning of this thread would do anything positive in this regard? I.e. not welded solution

 

[bradz]

good input their from above.

yes i once saw a pic of the z4 with a ballooned Front turret using the kw club sport since having mine on I've made sure to run the underside reinforcement plates and the SB , between these two i feel pretty confident in the additional strenthening.

Do you have any more info on the reinforcement plates? SB.. Strut Brace?

 

[TomK]

good input their from above.

yes i once saw a pic of the z4 with a ballooned Front turret using the kw club sport since having mine on I've made sure to run the underside reinforcement plates and the SB , between these two i feel pretty confident in the additional strenthening.

Do you have any more info on the reinforcement plates? SB.. Strut Brace?

It was these that I ran with my intrax on the e46m3
https://www.turnermotorsport.com/p-323-e46-strut-tower-reinforcement-plates-priced-each/
not sure if they fit our cars but I think so, beedub can confirm

 

[bradz]

Personally for me...

It has not been tested enough, at least the stock config is tried and tested.

My biggest worry was popping the top mount or snapping/bending the lower arm, if that happens... you ain't getting home... and its not an easy fix that the average garage can fix... whereas you can drive with a failed shock/spring with the OE config.

 

[GuidoK]

Intrax engineers suggest that on a street set-up (which mine will be) there is no need to reinforce as the spring rate will be soft.

Easy to say....but are they willing to give a 2 year unlimited warranty on the chassis? I think not.
And in case of the e46 m3 subframe problems even that (2 year bmw warranty) wasnt enough, as problems started only after 5 years or so..
TBH most cars that are heavily modified and run on track do very limited miles (maybe 1k/year max) and are often not that long in posession (3 years or so and then they move on). If you're planning to keep and enjoy the car for years, I'd only go with tried/proven solutions, especially where it concerns the chassis/body. I mean a subframe or control arm is easily replaced, it may cost you 1-2k, but extensive repairs on a chassis....not so much (and will the chassis ever be the same again....)

Guido, do you think the rear strut brace or similar I linked at the beginning of this thread would do anything positive in this regard? I.e. not welded solution

Personally I dont think it will be effective agains the problems I can imagine. It only transferes some lateral movement to the other tower. It doesnt strenghten the lower welds etc.

My biggest worry was popping the top mount or snapping/bending the lower arm, if that happens... you ain't getting home... and its not an easy fix that the average garage can fix... whereas you can drive with a failed shock/spring with the OE config.

I dont think that's the biggest worry that can happen.
I'm thinking more like spotwelds slowly seperating/tearing apart (for instance in the wheel wells and under the boot), tears in bodypanels etc.
And the problem is, lots of panes and constructions there in the chassis are double panels etc, so even getting to a spotweld to drill out and reweld is a huge problem and can mean cutting out other panels, then do the repair and then weld in a new panel etc etc.
Take a look at the youtube vids from redish motorsport and what they do. And that is on a known problem for which tried and tested solutions have been developed over the years. Can you think of doing that on a car that has new problems no one has ever seen before?
And what those problems could be is very difficult to predict. Its not that you're gonna increase load on certain parts, you're gonna change from parts that now and then get a load on it (only when the shock compresses/decompresses) to something that is continously loaded up (not only the increased load of the springs, but it will be loaded up all the time as long as the car sits on its wheels)

And why should you do it? The rear suspension only travels about 20cm max in extreme conditions (not on a track...). Sure a longer spring can be made so that it can control every step of that motion to the outer extends of that motion a little bit more carefully in terms of consistency in spring rate etc, but its not like the z4 is a baja buggy where long springs are required. A corvette still has a leaf spring and will still kick the z4's ass on a track.... :roll:
I'd only go that route if I was an experienced body repair tech that would be able to repair the potential damages myself. (or could afford one obviously)