Eliminating body roll...

[Mikey_Boy]

I might be coming into this thread a bit cold having only just read a couple of the posts so apologies if I am repeating anything.. A quick thought - most people in racing make the mistake thinking that stiff and low for springs is good. Just by stopping the suspension working or indeed moving as it should does not eliminate the fundamental problems! Most roll axis issues for corners are cured through either a) a stiff structure to start with and b) work with anti roll bars. Lotus Espirits for example are limited on spring rate due to a lack of inherent body shell stiffness - moving your shell is another complication you really don't need!

Cheers,
Mikey_Boy

[GeoffBob]

I might be coming into this thread a bit cold having only just read a couple of the posts so apologies if I am repeating anything.. A quick thought - most people in racing make the mistake thinking that stiff and low for springs is good. Just by stopping the suspension working or indeed moving as it should does not eliminate the fundamental problems! Most roll axis issues for corners are cured through either a) a stiff structure to start with and b) work with anti roll bars. Lotus Espirits for example are limited on spring rate due to a lack of inherent body shell stiffness - moving your shell is another complication you really don't need!

Cheers,
Mikey_Boy

Well said Mike. May be this is a bit harsh, but I am of the opinion that many so called performance modifications are justified by sales jargon rather than the laws of physics. It is understandable that many don't wish to understand in detail the operation of their cars suspension (or brakes, LSD gearbox etc), but it is equally unacceptable that we accept blindly that certain parts will indeed improve the control, stability and timing of our cars while out on track. I maintain that to objectively decide whether a certain part (new spring, ARB, caliper, tyre etc) will benefit my car, I first need to understand how it will work in combination with what is already there, and then (should I decide to fit the part) evaluate on the track if it achieves what was promised on the can.

[Rusty_McRusty]

If good handling is what you're after, I'd suggest that your car is too low. Lowering more than around 35-40 mm does more for the aesthetics than it does for the cars ability to corner.

I think I touched on earlier with a comment about the rear suspension and camber issues. More camber means less contact area to 'put the power down' and so, despite improved cornering characteristics, traction can become an issue, it's the reverse of braking issues encountered with too much front camber.

With the front suspension, the camber shift with compression on a MacPherson strut design can cause issues too, I'm currently working to reduce this issue on my S2. The arc scribed by the lower arm relative to the fixed top mount means that with extremem lowering, rather than the desireable situation where the camber becomes more negative with compression, it actually starts to become less negative and in some cases shifts to positive on the outer wheel, something that isn't brilliant. This effect can be seen in some hard cornering pictures of my S2 but does seem to be less evident on the E30, perhaps a function of improved geometry due to the RWD layout. Moving the top mount point inwards can help here, hence the availability of offset or adjustable top mounts.

[spic]

I understand all of the above... but if lowering the car more than 40 mill will ruin the handling what will fitting a cup sport kit do as it lowers the car by roughly 2 inches... I infact missled you all about the springs i fitted as i thought i had fitted Apex springs but after checking my invoice for the spring drop i noticed i infact fitted Jamex springs so i guess straight away by changing springs and all bushes i may feel a little less roll/control ...

[Rusty_McRusty]

Spring rates are unlikely to be massively different so any changes will be minor when swapping to Apex, HnR etc. If the Jamex springs are a silly drop (-80mm) then the HnR kit will provide a more sensible height with some advantages in geometry, something like 45mm lowering, so the handling should improve, once all the tracking etc. has been setup. The Apex kits sit either side of the HnR at -30 and -60 with the -30 kit being about the same drop as stock M Tec and the -60 kit heading towards the more aesthetic style kit, great on a budget but I'd say the HnRs will sit better but at double the cost. I have both -30 and -60 kit here but am unsure about what I'll end up using. Currently got the -30 kit on there and it's a little lofty, I do have a few options with it and I'm not sure I want to go -60 as it could start to mess up the geometry. As GeoffBob says above, best to test it to make an informed decision! If you want to try some Apex springs then let me give me a shout!

Sounds like the dampers will be the largest upgrade you can do on non-coilover suspension, if the Jamex springs are a sensible drop then get some proper dampers on there, it won't alter roll when loaded but will give you more control in the transient condition and should give more confidence as the body motion is better controlled.

Only other option, that's not been mentioned due to cost, is the Ireland engineering stage 3 springs, I emailed him about these when I was looking and costs were mad for 1 set but I'm sure that for a group buy, they'd be much better.

http://store.nexternal.com/shared/Store ... =216834664

I was quoted $170 postage on a single set..

TBH, those Leda coilovers looked most tempting for the money, that's about the cost of some decent dampers...

[GeoffBob]

I understand all of the above... but if lowering the car more than 40 mill will ruin the handling what will fitting a cup sport kit do as it lowers the car by roughly 2 inches... I infact missled you all about the springs i fitted as i thought i had fitted Apex springs but after checking my invoice for the spring drop i noticed i infact fitted Jamex springs so i guess straight away by changing springs and all bushes i may feel a little less roll/control ...

Because the designer of this kit has no doubt selected a damper whose rod is extended not far off mid-way of the total stroke when sat upon the ground with the spring. They also claim a 1.5" (38mm) drop, whose effect upon dynamic camber (by their own assesment I would imagine) is within reason.

from the H&R website:

H&R's Touring Cup Kits contain a specifically matched shock and spring set designed to provide improved handling, comfort and styling in one, precision-engineered package at an affordable price.

The kit includes a specially developed progressive spring tuned explicitly for your vehicle and then matched to custom-valved performance shocks. Most Touring Cup Kit applications will lower the ride height approximately 1.5" for enhanced performance while maintaining outstanding ride quality.

For the record, fitting shorter springs (to lower a car) without assessing the stroke of the damper is what Lepu and Bernie used to do in their East End chop-shop. Follow their example and you're one step away from fitting 4" wide wheel spacers .

BTW, I just love the bit above where H&R claim that their springs are tuned "explicitly" for my vehicle. I contacted them to ask when it was exactly that they popped around to corner-weight my car but they didn't reply.

Spic, just an idea, but have you considered having someone do a coil-over conversion on your car for you? It's not as much work/costly as you may think and there are a number of people on the Zone who have done this. I am one of them.

[Mikey_Boy]

+1

I fitted coilovers to my car and they made a big big difference - nothing fancy, just a Gaz road set up.

Biggest handling improvement though was fitting poly bushes all round and Eibach adjustable anti roll bars. I had issues with too much roll at the rear giving me understeer problems - instantly cured with the uprated and adjustable roll bars.

Fitting all that made me realise I need a stiffer shell than I have already!! (Standard E30 shell with 6 point safety devices bolt in roll cage)..

[GeoffBob]

With the front suspension, the camber shift with compression on a MacPherson strut design can cause issues too, I'm currently working to reduce this issue on my S2. The arc scribed by the lower arm relative to the fixed top mount means that with extremem lowering, rather than the desireable situation where the camber becomes more negative with compression, it actually starts to become less negative and in some cases shifts to positive on the outer wheel, something that isn't brilliant.

Rusty, I worked on exactly this problem when I designed my spaceframe. Short of inplementing a set of compound levers (in which case I may have just thrown away the McPhersons and fitted double wishbones off another car) I opted to lower the height of the strut towers (requiring a physically shorter strut) but then I raised the height of the points where the arms locate to the frame. I have seen some E30's lowered so badly that that the arms are almost horizontal (shifting the camber towards positive while cornering). Despite the fact that my car is lower (although lower than exactly what is a matter of debate ), my arms are still angled downwards at a good 20 to 30' or so while static (iirc).

The disadvantage of doing this is that the cross member (and steering rack) sit higher than on a lowered car (not far off stock actually). This is not a problem for me as my 4-pot sits behind the cross-member, but I can see this as being an issue for others. Another way look at this is that I didn't raise the wheels up into the wheel arches, I lowered the body down over the stock suspension.

BTW, this is the technique that was inplemented on the DTM cars. Pics of the front suspension clearly showed how they reaised the lower mounting points without having to cut away whole chunks of car.

[Rusty_McRusty]

Just caught up on you R5/E30 thread, loving your work I'll get round to something a bit more extreme one day, a few little things to sort out first, like money and a garage ;)

I believe that in quite a few 'tin top' racing series, you're allowed to move the suspension mounting points by a pre-determined limit, this was certainly the case for the Audi 80 Competition quattro that campaigned in the early 90s in the French and Italian supertouring series - 25mm springs to mind but that's just the grey matter ticking over. The DTM was always more extreme and your description certainly illustrates that! Those cars have more than likely driven many to their love of E30s, I know that's the case with me, since as long ago as I can remember quattro rally cars, E30 DTM, Merc DTM and Cosworth BTCC were very much in the blood, seeing them in the flesh hardly helped either!

The Audi is a difficult car to tune in that respect as it's so tight up front and there's a lot going on that all needs room. The subframe carries a monster gearbox that includes front and centre diffs (some 100kg!) and it also has to clear at least 3" downpipe. Some have to space the subframe away from the chassis (lower), thus making things even worse! A custom designed subframe would be a good plan and could allow for some properly located wishbones but it's not reached that stage yet as it's more a road car that get used on track... I'll have to give this some thought at some point... or just go mad on an E30 instead, I'm certainly getting to love my IS, somewhat of a RWD training vehicle.

In an attempt to address the wishbone angle of dangle, some have tried ball joint extenders that move the wishbone ball joint end downwards by approx. the amount lowered (~30mm)but I'm not a fan, they just don't strike me as a great idea and there are some clearance issues with the brake discs, dust shields... and ground. The rack is on the bulkhead (as with many VAG cars) so that's not an issue there. The E30 has a lot more room for manouvre as the RWD chassis allows for plenty or scope to move things around.

The B5 chassis Audi S4s have twin wishbone and while they don't have the RWD handling characteristics of the E36 and E46 (both of which emply MacPherson), they ride and handle superbly well but at the expense of involvement - the handling side really is chassis setup by Audi, some work on geometry, spring rates, ARB rates etc. really can work miracles on them - they're well balanced and don't suffer from the same long engine in the nose that the earlier I5 cars did, like mine. That said, there are a few B7 RS4s that can testify that old technology can loom large in the rear mirror.

Many (actaully it's not many based on performance and sheer money invested!) who have driven my now 16 year old S2 have commented that they like the steering and involvement, all this on a car that was described as anodine when it was launched, this includes the S4 driver and two E46 drivers... The E30 is a little better now but as stock it wasn't as good. Sometimes it's good to have a slightly flawed setup as it makes things more interesting, that's not the case in racing but for track days, I prefer smiles rather than lap times.

Most interesting comparing and contrasting the two cars, they're different but a both similar in that they bring a large smile to all who I've given a lift to, either on UK tracks or round the 'ring.

Another long post and slightly off topic. Ooops.

[GeoffBob]

An interesting read Rusty. Sounds like there is so much more room/potential to play with your E30 M42/44 hybrid than with the S2.

Ball joint extenders were not something that crossed my mind when I tackled my suspension, but certainly one way around the problem. Much like yourself, I would not feel confortable using these.

[Rusty_McRusty]

The S2 is stockish with a chip and running 300bhp/330ftlbs... potential is about 450bhp on the road with a GT3071 to maintain some driveability, whatever the budget will stretch to on track, GT40 sees about 575-600bhp if you have the £. RWD handling and adjustability vs. bullish performance and tenacious grip, they both have their place and complement each other well

Tempted to follow Tim_S's route of a 2.1 and then ITB it for that true 'baby M3' experience, eithger that or an M50/52. As it stands, it's a nice daily car, if not a very sensible one.

[spic]

I was thinking about coil-overs because the bilstien B6 shocks which i have been looking at are nearly 400 for the set and i see RPM are selling Gaz coil-overs from 595.00, but i think i would go for the GAZ Gold if money wasnt an issue ! fitting isnt realy a problem as im ok with the spanners but im a little worried that if i go down that route then there will be offer parts i need to complete the job which well then lead to me blowing my budget...The springs i have fitted are 40-35 drop so not to extreme i hope, has anyone used the Gaz adjustable shocks inserts, are they any good i wonder...? i was given a price of around £75 per shock for them and they do sound quite appealing for the money,

[Rusty_McRusty]

Gaz themselves say that the cheaper coilovers are not for track use. See no reason not to use the inserts though, make sure they're matched to your spring choice if that's an option, best to speak to them.

Jamex springs should be OK, measure wire OD and count coils if you want to compare, TÃaV data sheets show this info for Eibach, HnR, Apex, etc. ~12mm wire and about ~6.5 coils on the Apex / HnR fronts I think, 7.5 coils for Eibach... check though, that's from memory.

If you want Bilstein then the B8s are designed for lowering springs, also, the fronts have a larger diameter shaft so I believe they're stiffer in bending to help under cornering.

The Bilstein dampers are a one fits all solution, they're not adjustable but can be re-valved when rebuilt. Perhaps better to be able to alter damping for different tracks...

[BadDave]

I use the GAZ inserts in my DIY coilover conversion.

I got them to fit shorter piston rods and revise the damping to suit MY requirements.

IF you go through a 3rd party you'll get stock dampers.
IF you deal with GAZ directly, they'll fit shorter rods/tweak them, if you ask them too.

They are decent enough when you give them a call.

I just deal directly with them,cutting out the middleman which usually saves time and money

[spic]

If you want Bilstein then the B8s are designed for lowering springs

After reading this and another thread i was sure B6's were for the lower spring ?

[Rusty_McRusty]

Well, according to Bilstein themselves, the B6 is not an all out sports shock and the B8 is shortened (for use with shorter lowering springs). B8 is what you want but your pocket won't like you. Gaz inserts sound interesting and those Ledas are looking good vfm.

http://www.bilstein.de/products/high-pe ... in-b6.html

http://www.bilstein.de/products/high-pe ... in-b8.html

[spic]

The B8's do sound like the ones so i guess the B6's are realy for the low riders... any idea what the 8's are priced at ? ECP gave me a price of 95 fronts each and 75 rears each plus the vat ! i guess they will be around that priceor more ?

[Rusty_McRusty]

The B12 kit has B8 dampers but is a small fortune and for the IS it comes with the soft Eibach springs so best avoided, that said, Balance Motorsport mention on their website that they'll do custom kits with springs of your choice.

The B8s are available through Demon Tweeks, not saying they're the cheapest though:-

http://www.demon-tweeks.co.uk/Performan ... /332/24137

Europerformance have a good website but I can't see the B8s, only B6s

http://www.europerformance.co.uk/pages/ ... kabsorbers

The Gaz dampers seem to be about half the price, contact them directly though, as above.

Motorsport World site is also quite good:-

Front - http://www.motorsportworld.co.uk/detpro ... PID=839541
Rear - http://www.motorsportworld.co.uk/detpro ... PID=845802

The B8s are know as 'Sprint', B6s as 'Sport'.

As before, they're not adjustable.

HTH

[spic]

Thanks Rusty for your trouble posting these links, I spoke to GAZ today and Dave there was very helpful and after a little talk with him i have decided to go for there shock inserts but with the internals from the Gaz gold coil-overs... i think he said 87 plus the vat for the fronts each and 57 for the rears... even though there only adjustable for the re-bound, would it be wise to reinforce the rear top mounts or would that be overkill ? is there anything else i should replace while im in there beside the front top mounts ?

[RPM]

Dave is the designer at GAZ and really knows his stuff

If you are looking at buying GAZ, we offer them at a cheaper price than GAZ direct due to our volume and discount of which we pass an amount to the customer.

For example your prices above:
Front insert from GAZ £102.22 inc VAT
Front insert from RPM £79.95 inc VAT

Rear adjustable damper from GAZ £66.97 inc VAT
Rear adjustable damper from RPM £65.00 inc VAT (not much in that one admitidly)

The difference on coilovers is however £100's cheaper from us

If you are looking for topmounts we have the below:
http://raceperformancemodified.com/BMW- ... -Topmounts
http://raceperformancemodified.com/BMW- ... -Topmounts

Drop us an email or give us a call if we can be of any additional help

[GeoffBob]

Thanks Rusty for your trouble posting these links, I spoke to GAZ today and Dave there was very helpful and after a little talk with him i have decided to go for there shock inserts but with the internals from the Gaz gold coil-overs... i think he said 87 plus the vat for the fronts each and 57 for the rears... even though there only adjustable for the re-bound, would it be wise to reinforce the rear top mounts or would that be overkill ? is there anything else i should replace while im in there beside the front top mounts ?

Sounds like you are on the right track spic I tend to refrain from pointing people towards specific products as opinions abound and few seldom agree. I am however pleased to hear that you have chosen Gaz dampers. Adjustable on the rebound will be more than adequate. BTW, Gaz and Koni are my preferred brands.

[spic]

Thanks for posting RPM i will be calling you with my order in due course, With regards to fitting adjustable shocks it there anything else i need to do besides fitting new shock top mounts ?