Coilovers for E86 - comfort road use

[Tankyuusha]

Hello,

I've recently got back into a Z4 coupe 3.0Si, (I bought a brand new one in 2007), and, despite being fitted with Toyo Proxes Sport (not runflats), the ride is still quite harsh. So I am looking to fit coilovers that won't lower the car, or if they do, only minimally and won't firm up the ride / make it more crashy. I looked at KW ST X COILOVERS, but understand that they can be a bit hard and lower the car a lot. Any advice, experience of suspension upgrades that increase comfort whilst not detracting from the cars handling capabilities?

 

[True-Blue]

If it’s on the original shock absorbers they are likely to blame and I suspect replacing them with O.E. Sachs shocks would make a world of difference

 

[Rockhopper]

I don't think anyone would suggest fitting coil overs if you wanted a more comfortable ride.

 

[plenty]

Check spring rates. 6-7 kgs front and 10 kgs rear will be perfectly compliant as long as the damping is matched.

I'm not sure about the Si as I've only got direct experience of the Z4M which has different front mountings, but BC Racing coilovers on the Z4M can run higher than OEM ride height if wanted.

 

[Tankyuusha]

Thanks for all the tips. Plenty, exceptionally helpful!!

 

[Tankyuusha]

Thanks for all the tips. Plenty, exceptionally helpful!!

 

[Tankyuusha]

Has anyone experienced these from KW: https://www.kwsuspensions.co.uk/shop/BMW_Z4_Coupe__E86__03_2006-01_2009_E86_3.0_si_Petrol_195KW_2996ccm_crKfgX-8HlICOdsIi2Whrw../56/Street_Performance/18220004

 

[Mr Tidy]

My MC came fitted with nearly new H & R coil-overs and to be honest I find the ride on most British roads terrible, to the point of being crashy on poor surfaces. But they are fantastic if you find a smooth stretch of tarmac, as I discovered last year doing a couple of parade laps around Donington!

But they can reduce ride height by up to 2" at the front and 1.7" at the rear, so the springs are that much shorter than OE and inevitably to keep it off the bump-stops they are much stiffer - as I found out this year when I had a passenger ride in an MC on OE suspension that was only 20,000 miles old.

As only the ride height is adjustable, so they are nothing more than variable height lowering springs! And having got them as high as they will go (0.9" drop front and 0.7" rear) that's where they will stay! When I got it the first time I encountered a speed bump the floor grounded.

Based on that if I was buying suspension for my car I'd only consider buying coil-overs with adjustable compression and rebound.

I know my E86 isn't the same model but I expect the same would apply.

 

[Tankyuusha]

Cheers Mr Tidy!

 

[Tankyuusha]

Check spring rates. 6-7 kgs front and 10 kgs rear will be perfectly compliant as long as the damping is matched.

I'm not sure about the Si as I've only got direct experience of the Z4M which has different front mountings, but BC Racing coilovers on the Z4M can run higher than OEM ride height if wanted.

These look promising; https://www.kamracing.co.uk/bc-racing-br-series-coilover-bmw-z4-e85-e86-2002-to-2008.html

 

[DaveD]

I’ve got ST XTAs fitted - the ones with fully adjustable camber/castor plates at the front. I think they’re pretty good ride comfort wise. They’re no firmer than the B6 dampers and sport springs I had previously but have much better Rolland pitch control. And I’m running 7 degrees of castor be stock 5 degrees. Makes the steering much better - significantly more so than just moving the adjustment ring on the electric steering. I’d recommend them and they’re excellent value for money given it’s KW damping

 

[plenty]

These look promising; https://www.kamracing.co.uk/bc-racing-br-series-coilover-bmw-z4-e85-e86-2002-to-2008.html

I run the BC BR series on my Z4M, 6 kgs F / 10 kgs R with good results with ride height close to OEM. For a little more money you can find the BC RM series which are superior to the BR series as they use inverted front dampers: https://cp-performance.co.uk/product/bc-racing-rm-series-coilover-kit-bmw-z4-m-e85/#

Bear in mind as mentioned the fronts have different mounting points in the Si and I don't know if it's possible to achieve the same ride height on non ///M models.

 

[Barty]

Ive got ST X coilovers on my coupe and -when combined with 19” wheels- the ride can be quite firm. I’ve had the pleasure of testing the ride back to back with [ref]MaldivesMax[/ref]’s Z4 which is on 18”, Eibach springs and new Sachs dampers. A very comfortable, much more refined setup that still allows you to throw the car around well enough (though not quite as flat and poised as on the coils), especially with the overhauled bushings and RTAB limiters fitted to his roadster. Michelin Pilot Sports also help in that regard

 

[Z4Mariner]

My 2006 3.0Si coupe is over 17 years old now. It came with the Sport (aka M-Sport) suspension, so this past Winter/Spring I installed new OE spec Sport springs on all corners together with B4 struts and shocks. My goal was to restore a compliant ride with decent handling on relatively rough roads. It worked for me, and it now feels solid but supple.

My reading on what suspension to install turned up a new E86 owner who stated that his new-to-him coupe rode worse than a Shelby Cobra. Upon advice from others, he lowered his tire pressures significantly and suddenly found his car much more enjoyable to drive - better ride, but no loss in handling. I took that advice to heart this Spring and I experimented with tire pressures. 1 to 3 PSI changes in tire pressures seem to make a huge impact on my ride - this seems more dramatic that on other cars that I've had. I suspect that this is more pronounced on the E86 than the E85 because of a stiffer chassis. So once you decide what hardware to install, plan to explore your tire pressures to help tune in the ride you want.

PS - my tires are Michelin PS4-AS - not runflats

 

[matsmith749]

So now I'm confused - I thought all suspension that had a combined shock absorber & spring around it was called a 'coilover'.

As such - you can get them in any specification you prefer - from super rock hard & lowered, to the softest of the soft.

Have I got it worng all these years?

 

[plenty]

As such - you can get them in any specification you prefer - from super rock hard & lowered, to the softest of the soft.

Indeed. But it's also true that a number of aftermarket coilover products come with default specs that are less compliant than OEM. Presumably that's what the market wants, as somehow a firm ride has become associated with 'sportiness'.

Hence the importance of paying attention to the spring rates.

 

[Tankyuusha]

My 2006 3.0Si coupe is over 17 years old now. It came with the Sport (aka M-Sport) suspension, so this past Winter/Spring I installed new OE spec Sport springs on all corners together with B4 struts and shocks. My goal was to restore a compliant ride with decent handling on relatively rough roads. It worked for me, and it now feels solid but supple.

My reading on what suspension to install turned up a new E86 owner who stated that his new-to-him coupe rode worse than a Shelby Cobra. Upon advice from others, he lowered his tire pressures significantly and suddenly found his car much more enjoyable to drive - better ride, but no loss in handling. I took that advice to heart this Spring and I experimented with tire pressures. 1 to 3 PSI changes in tire pressures seem to make a huge impact on my ride - this seems more dramatic that on other cars that I've had. I suspect that this is more pronounced on the E86 than the E85 because of a stiffer chassis. So once you decide what hardware to install, plan to explore your tire pressures to help tune in the ride you want.

PS - my tires are Michelin PS4-AS - not runflats

Brilliant advice! Thank you, I’ll have a play!

 

[9designs]

Yep.... one of my pet hates the term "Coil over" so misused. The Front is coil over as stock being a McPherson strut design. Rear is a divorced spring, many kits keep it like that.
Lesson learn for me on a previous E85 I bought a BC kit, but it had bushed top mounts rather than stock rubber mounts. Terrible move for the road, just made it crashy and harsh.
I'll also avoid "cheap" dampers, as they don't have the free movement and low friction of the better ones. If adjustable and they have the range then no reason for them to be worse ride, I'd expect better. As long as the spring rate is matched.

Stiff dampers and soft springs makes for a crashy ride. So if using stock springs they would need to be able to go soft enough, other wise fit stiffer springs to give the dampers more work to do and take the harshness out. If you can't soften the damper, stiffen the spring, similar effect but with less travel.

 

[SparkyE86]

As a side note on suspension....Remember when wheeler dealers got custom shocks done for a 993 ? That place (quantum racing) is run by Patrick Murphy (ex F1 mechanic) I got a price....around £2900 + some development time. They hadn't done a set for a E86 before and were concerned about expectations (never been in a E86 before with M-sport suspension....that needs a refresh lol). Not a bad price really considering it would be tailored specifically to the car with some input from yourself. Ed China on a live Q&A was asked about that set up and he said it was superb.