Rebound and bump for idiots

[daniel]

Hi,

There appears to be a lot of experience with KW suspension on this forum so I thought I would pose the question... how does bump and rebound affect my ride quality.

I have read the pdf on thorney website but am having trouble relating to real world and my setup. For example, the pdf suggest rebound impacts dive and roll, whereas I thought softening off my compression (bump) would result in a great weight transfer, and ultimately grip?

Which setting has the greatest impact on ride comfort? ie help soaking up bumps and ridges while just cruising?

Thanks

[shimmy]

Hi,

There appears to be a lot of experience with KW suspension on this forum so I thought I would pose the question... how does bump and rebound affect my ride quality.

I have read the pdf on thorney website but am having trouble relating to real world and my setup. For example, the pdf suggest rebound impacts dive and roll, whereas I thought softening off my compression (bump) would result in a great weight transfer, and ultimately grip?

Which setting has the greatest impact on ride comfort? ie help soaking up bumps and ridges while just cruising?

Thanks


Most effective way of improving ride quality is by......










Going back to OEM as KW has a poor range for road settings :)

[Thorney]

lol.

I'm writing an article for a magazine about car set up so the full detail will have a wait (its a 5 page article) but in essence:

Spring - holds the car up and combined with ARB controls some aspects of the cars roll, stiffer spring means car will roll less but means it will take more of a bump to get it to compress (I wont go into progressive rates etc).

Compression (bump) damping - controls the speed at which the shock compresses when hitting a bump in the road, on 3 way suspension this is split between high speed and slow speed. High speed means high speed compression, ie hitting a kerb, slow speed is more transissional; undulations in the road. So, if you have a ride where the car feels too crashy over bumps then its likely your bump is too hard and needs to be softer. However if you go too soft the chances are the spring is too hard for your needs and you're better off changing a spring rather than running damping on full soft.

Rebound damping - this controls the speed the shock extends after compression, rebound tends to control the speed at which the car retains its balance, if the car feels bouncy the chances are the rebound is too soft and is reacting too quickly so you need to stiffen it up.

Add in tyres, wheels, ARB's, ride height, camber, castor, trail, toe, mono tube/twin tube, aero and driver style and you can see why it takes some time to really develop suspension for road or track. In development we tend to use three way adjustable (4 way sometimes buts its hard work) to set up damper settings which are then used on the less adjustable shocks for the road. Takes me 2 full days to set up a race car from scratch on three ways for example and assumes about three spring rate changes.

[Thorney]

There is also no 'right' answer, I tend to prefer very stiff springs and very soft damping as (IMO) it allows greater adjustment of grip over a wide range of applications, but other people prefer a very soft spring and very hard damping, its a case of whatever works for you.

Generally soft = grip but it comes at the expense of overall speed.

[glendog74]

Most effective way of improving ride quality is by......

Going back to OEM as KW has a poor range for road settings :)

Rubbish...

And you have had first hand experience of KW Shim? :smt012

[Curly]

he's pulling yer chain snoopdog;)

[shimmy]

And you have had first hand experience of KW Shim? :smt012

yep

[glendog74]

he's pulling yer chain snoopdog;)

Most probably - as Shimmy always does... :clown:

yep

Go on then, tell me all about your personal experience of KW V3's or Clubsports as fitted to your M3 CSL & why there isn't enough adjustment... :whistle:

[daniel]

Thanks for the help:thumbs:

So bump will infact control things like rear end squat and diving under braking.

Based on no experience at all I would have thought that a soft to moderate bump and harder rebound would suit our roads?

[shimmy]

Most probably - as Shimmy always does... :clown:



Go on then, tell me all about your personal experience of KW V3's or Clubsports as fitted to your M3 CSL & why there isn't enough adjustment... :whistle:

not my CSL but the M3 i drove with KWV3, the only criticism i found was there didnt seem to be enough adjustment to get it compliant enough for the road anywhere near OEM or as much as Intrax. It seemed to still be a bit lumpy and thumpy which i was not used to

Now i know the springs might have been different but that was my experience:smokin:

[glendog74]

not my CSL but the M3 i drove with KWV3

Hardly a long term test impression then? :whistle:

I have to admit, when i first got my KW Clubsport kit, i had it fitted by a reputable garage but one, who by their own admission, were not familiar with KW and it's setup. It was fitted in a bit of a rush during a hectic day and without particular reference to the fitting/setup instructions... Needless to say, my initial impressions were of no obvious improvement over OEM on the road, but comfort was similar.

I then had a helpful mechanic stiffen the setup better for my recent track day at Donny and it seemed to help a little - but again; not very impressive. This unfortunately made the ride stiff and very crashy - particularly at high speed on the Autobahn (>120mph...)

To make things worse, i then had the driver's side front lower wishbone replaced under warranty by BMW which cocked the whole camber/toe settings right up!

So, i had a car with decent suspension that was simply not right...

To illustrate quite how badly the car was now setup, i recently had the car setup by a 'KW specialist' somewhere on the Continent... They found the front camber was -2.5deg left side, -1.0 right (thanks BMW...), the ride height had been set too low and was at risk of becoming coil-bound, and the rear toe was in on one side - out on the other! I had wondered why the car was pulling to the left... :banghead:

Well, the 'KW specialist' returned all settings to the ones that they recommend and straight away the car felt a lot better on road and much more composed at high speed. Ride was a little firmer than OEM but not uncomfortably so.

However, it was on track that the settings have really transformed the car - the best setup i have experienced yet. I had the chance to drive the Ring last week over 4 days and had both wet, dry, and damp conditions to experiment on. Having been shown how to adjust the car bump and rebound settings (which is a lot easier to do than some 'nay sayers' will claim) i was able to dial out a little understeer skip in wet conditions by softening rebound. In the dry the car is absolutely fucking awesome - and that was on PS2 tyres! :supz:

So what i'm trying to say is, there are several top brands of suspension out there and we have knowledge and good things to say of some more than others. The key really is in the setup and how well this has been done. I will now soften the car out a little for UK road winter driving and it will be fine.

What i do know is that my KW Clubsport kit is now setup superbly and i also have the knowledge to fine tune it to suit. It really does engender huge confidence in the car around a track and is very liveable with day to day on road - i'm now very very happy! :thumbs: :thumbs: :thumbs:

[northernjim]

I did wonder what the flock you were doing at the factory rob.....


I can vouch for how different a few 'twiddles'technical term I know! of the knobs can transform a car;)



now you can put up all the pictures of their RS! and how it drove???

[daniel]

Glendog74 - with a statement like that you are going to have to share your ride height and camber/toe settings:thumbs:

[shimmy]

there didnt seem to be enough adjustment to get it compliant enough for the road anywhere near OEM or as much as Intrax. It seemed to still be a bit lumpy and thumpy which i was not used to


Hardly a long term test impression then? :whistle:


but it seems pretty accurate though




no obvious improvement over OEM on the road, but comfort was similar.

This unfortunately made the ride stiff and very crashy - particularly at high speed on the Autobahn (>120mph...)

Well, the 'KW specialist' returned all settings to the ones that they recommend and straight away the car felt a lot better on road and much more composed at high speed. Ride was a little firmer than OEM but not uncomfortably so.


so on road it was no better than oem, then rubbish and CRASHY, then finally firmer but not uncomfortably so :whistle:.

i am not arguing about track set up at all, but just that KWV3 seemed to not have a soft a setting for road as OEM:supz:

[glendog74]

i am not arguing about track set up at all, but just that KWV3 seemed to not have a soft a setting for road as OEM:supz:

And herein lies a flaw in that point: OEM suspensions are built with compromise always in mind between sporty handling characteristics and ride comfort...

I didn't fit KW Clubsports to emulate OEM road ride comfort after all! But if i'm honest they really aren't that indifferent to that now anyway when set up for road.

[shimmy]

And herein lies a flaw in that point: OEM suspensions are built with compromise always in mind between sporty handling characteristics and ride comfort...

I didn't fit KW Clubsports to emulate OEM road ride comfort after all! But if i'm honest they really aren't that indifferent to that now anyway when set up for road.

not sure what you are trying to prove Rob. the original poster just asked how he can make his car more comfortable when 'cruising' and refitting OEM is what suggested.



The OEM may be a compromise but in my opinion it is a much better compromise than Intrax or KWV3 for road/ring/track even with the adjustment. You cna bet your last dollar that more money was spent on designing it and setting it up than any of our a/m versions.

I tend now to favour the track use hence the Intrax but if my car was doing 14k miles a year again on road i would have no hesitation in getting the BMW suspension back on

[glendog74]

not sure what you are trying to prove Rob. the original poster just asked how he can make his car more comfortable when 'cruising' and refitting OEM is what suggested.


Not trying to prove anything Shim - i was just countering your habit of answering peoples questions with a simple one line/word answer that doesn't always consider the bigger picture or take other implications into account.

He has KW V3 (by the sounds of it) and he may not have OEM anymore? So potentially not a simple or cheap swap back...

If you want mega comfort, then you could also consider KW V1 or Bilstein/ other aftermarket ride comfort biased offerings. I'm pretty sure that he doesn't want a floaty/wafty big Merc type of ride though...

[shimmy]

He has KW V3 (by the sounds of it) and he may not have OEM anymore? So potentially not a simple or cheap swap back...



ill sell him mine for £1000 - its fooking crap :beer:

[glendog74]

Numpty :birdman::birdman::hahaha:

[glendog74]

Glendog74 - with a statement like that you are going to have to share your ride height and camber/toe settings:thumbs:

All set-up i.a.w. standard KW settings for fitting:

http://www.kw-gmbh.de/kw_upload/Einbau/eah35220825.pdf

Set-up:

http://www.kw-gmbh.de/kw_upload/Einbau/ea68579016.pdf

Not sure what toe settings were put on but my front camber is set to -2.5deg with ability to increase to -3.5deg if needed without any geo adjustments.

[shimmy]

i wish i ran -3.5 on track Rob, but dont you find that your inner road tyre wear with -2.5 camber is quite heavy?

i would be interested to find out what you front toe is with -2.5 and -3.5, castor as well:thumbs:

[daniel]

Wow, its all kicking off in here. :whistle:

I don't want to go as soft as the OEM suspension, just wanted to understand how to create a slightly softer ride for long motorway drives. Think I now have an understand of what I need to be playing with.

Glendog74 - Thanks for the link.

[AlexGTT]

i wish i ran -3.5 on track Rob, but dont you find that your inner road tyre wear with -2.5 camber is quite heavy?

i would be interested to find out what you front toe is with -2.5 and -3.5, castor as well:thumbs:

Shim, I run -2.5 all the time on road with adjustment to -3.5 for track. No inner tyre wear issues at all. Ask Julian/Ant what toe and castor settings are because I haven't a clue.

[glendog74]

i wish i ran -3.5 on track Rob, but dont you find that your inner road tyre wear with -2.5 camber is quite heavy?


I'm not sure yet!

Bearing in mind that i use a different set of wheels/tyres on road and track, i previously ran -1.5deg road and -2.5deg track; i found very slight outer wear issues on my road PS2 tyres (probably due to 'occasional' track use of my road set), and distinct outer wear on my track tyres - indicating not enough negative camber. My front PSC tyres have been written off prematurely due to severe wear with banding showing on the outside edges, whereas the centre/inner part of tyre has loads of tread left... :banghead:

Now that i have extra camber dialled in, i am happy to accept some additional road tyre wear - the track set should now wear evenly. If it gets that bad on road, i can always downgrade my road rubber to the 'cheapskate tyre of choice' - hard Falkens... Track is where i want my rubber to perform to its best ability :whistle:

[DuncanR]

I have Intrax 4-ways fitted, and drive everywhere with whatever settings Andy Mulholland dialled in, as Im too confused to touch it, and Im an engineer ! seemed to get him around the ring fairly quickly though !
imho im way too new to the car and track days,Ring etc. to even contemplate making adjustments, without any kind of benchmark, changes in setup would be futile in my case, all i know is that its gets around Spa in the wet, and the Ring, and it was pretty good around Bedford this week-end. It is I admit a bit harsh on the road but I have a large a$$ built for comfort. It would be nice in the future though to understand all about setup and how it can improve or otherwise my driving experince, but for now its foot down and hang on im afraid. I will however watch out for inner edge tyre wear as people have commented on the amount of camber Im running.

[TANKSLAPPER]

Duncan, don't you start ! ! ! !

LOL

[DuncanR]

T$ as my mentor with all things CSL at the mo, im like a sponge for knowledge ! ... and no i dont want to swap you my Intrax system for your very reasonably priced refurbed Bilstiens !!:hahaha:

[shimmy]

I have Intrax 4-ways fitted, and drive everywhere with whatever settings Andy Mulholland dialled in, as Im too confused to touch it, and Im an engineer ! seemed to get him around the ring fairly quickly though !
imho im way too new to the car and track days,Ring etc. to even contemplate making adjustments, without any kind of benchmark, changes in setup would be futile in my case, all i know is that its gets around Spa in the wet, and the Ring, and it was pretty good around Bedford this week-end. It is I admit a bit harsh on the road but I have a large a$$ built for comfort. It would be nice in the future though to understand all about setup and how it can improve or otherwise my driving experince, but for now its foot down and hang on im afraid. I will however watch out for inner edge tyre wear as people have commented on the amount of camber Im running.

i could have hours of fun playing with your 4 way Duncan!!!

[DazBlackCSL]

i could have hours of fun playing with your 4 way Duncan!!!

dont you start :whistle::hahaha:

[Lee13]

Hi Glendog74 I would be really interested to know what castor and toe settings are linked to the -2.5 & -3.5 negative camber and how it changes if at all when moved to -3.5. Also do you know how they set the back up?? Camber & toe?? I'm quite shocked other people are running as much as -2.5 negative with no premature tyre wear inside on the road. Sorry for all the questions but I'm fairly new to CSL ownership and have adjustable topmounts now so would like the best of both worlds on road and track......:thumbs:

[shimmy]

Hi Glendog74 I would be really interested to know what castor and toe settings are linked to the -2.5 & -3.5 negative camber and how it changes if at all when moved to -3.5. Also do you know how they set the back up?? Camber & toe?? I'm quite shocked other people are running as much as -2.5 negative with no premature tyre wear inside on the road. Sorry for all the questions but I'm fairly new to CSL ownership and have adjustable topmounts now so would like the best of both worlds on road and track......:thumbs:

ive seen cars running -2 on road with premature front inner wear let alone -2.5 so i am shocked as well, so maybe depends on mileage and maybe other settings such as toe and castor as well more than i thought?

my toe used to move from 1mm in to 0.5mm out when i changed camber form -1.5 to -2.5. Simpsons recently said that the movement in toe is more now i have -2 to -3 (no figures though) and i guess even more with -2.5 to -3.5 making it difficult to have the toe acceptable on road and track

[Lee13]

Thanks Shimmy, everyone seems to run different and has different tyre wear. I have set mine at -2.0 for the road with standard castor and toe. I guess I should just see how I get on and maybe run -3.0 on track. Do you find that's ok then?? Do you find a little toe out on track is better than the standard 0 degrees?? Also what do you run on the rear? I cant find anything really on set up only -0.5 camber to help oversteer but no mention of toe settings.... Thanks in advance for the help Lee

[s.mac]

I have standard suspension running at -1.5 camber with 10mm spacers and I have premature inner front tyre wear. Don't ask me about toe and castor though :whistle:

tyre wear is quite severe :banghead:

[shimmy]

ok, my car is set up by Simpsons. I used to have it set up for heavy road use (lots of miles) so went with front -1.5 camber, 1mm in toe. My PS2 tyres have lasted about 20k miles so far and on front still have 2mm and a little inner premature wear (but i suspect this was from -2 camber days a few years ago)

I think that Simpsons prefer to run toe out a little on track rather than have too much toe in on road. I think the balance is quite tricky but for the -1.5/-2.5 set up 1mm in and 0.5mm out was ok.

I am not sure what the toe settings are for my new set up (i will ask) but i suspect it is probably around 1.25mm in and 0.5mm out - dont quote this

on the rear i have always run -1.25mm camber and 1mm toe in for road and track. Tyre wear is perfect and curent Cups have now done 7 track days/1200 track miles. There might be better grip set ups at the rear but i am apy with good wear tbh.

NOW i have to add that this year i fitted the Intrax and it makes a massive difference to tyre wear imho on track as it stops the roll quite a bit and saves the edges. Not sure it makes much difference on the road (

[Lee13]

Thanks for all the info Shimmy:clown:

[glendog74]

Hi Glendog74 I would be really interested to know what castor and toe settings are linked to the -2.5 & -3.5 negative camber

Can't help i'm afraid - i don't know!

[daniel]

It sounds like everybody is using simpsons on here! What does a full alignment and proper setup run you?

[shimmy]

tbh sb, Simpsons, Thorney, Bexley Motorworks (BMS) and a few others all can do a good geo, as they all race and do road cars.

Pick your closest if it is just geo you want but just make sure you tell them what you want to achieve

[NZ_M3]

Static toe out on the track is fine - gives better turn in - but on the road it'll tram line quite a bit (that's what happened with mine anyway, so I've gone back to very very slight toe in for better stability) I ran quite a bit of toe out to help with the low speed understeer, but it just made the car way too nervous to drive for me at the limit.

[shimmy]

Static toe out on the track is fine - gives better turn in - but on the road it'll tram line quite a bit (that's what happened with mine anyway, .

thats what i was told at the time :thumbs:

[_Nathan_]

Toe out kills the inside edges but is great on track, everything in suspension seems to be a compromise if you use the car on road and track...

[NZ_M3]

Toe out kills the inside edges but is great on track

According to my experience and the Simpson's article posted by Shimmy it's the other way around actually:


Too much toe-in and the tyres will tend to wear prematurely on the inner edges
through scrubbing. Conversely, too much toe-out will see the outer edges wear in
the same way.

[_Nathan_]

Sorry.

[shimmy]

Sorry. thicko:hahaha:



:beer: i had to look up what castor was yesterday :thumbs:

[_Nathan_]

I'm wearing my dunce's cap now ;)

[Thorney]

Nopt as simple as that, it depends on camber too. Any toe (in or out) can wear the tyres, the elvel of camber dictates whether its inner or outer tyre wear.

[DuncanR]

I hope we are going to have plenty of 4 play before you play with my 4 way Shimmy !:smt055

[Bealo]

How did i miss this thread????

The gay lovers having a go at eachother is pure class :hahaha: :gayfight:

But seriously i haven't got much understanding on the subject but all i know is that i run -2.5 on track and feel i need more as i wore the outside edge on the front cups really quickly.

Not sure if i need to stiffen up the suspension aswell? My issue on track is turn in. the car understeers to much in mid to high speed corners.

Be interested to try out Rob's settings/setup.

When i got my geo done at BMS they recommended using standard CSL geo. What do you guys in the know think about that???

[shimmy]

how did i miss this thread????




yep, surprising as the title is virtually aimed at you!

[daniel]

More settings would be helpful. I am running normal street tyres with -2 and I get understeer. Thinking -2.5 or -3 might be good and also raise the rear a bit.

[shimmy]

More settings would be helpful. I am running normal street tyres with -2 and I get understeer. Thinking -2.5 or -3 might be good and also raise the rear a bit.

neg camber on road of -1.5 is about right, anymore and you compromise straight line stability, tyre wear and braking just to solve a bit if understeer which is predominently caused by driver error

some run -2.0 on road so that track camber is better and can be turned out to -3.0 with adjustable top mounts

[glendog74]

yep, surprising as the title is virtually aimed at you!

:hahaha: :hahaha: :hahaha:

[Bealo]

:hahaha: :hahaha: :hahaha:


HAHA laugh it up pint pot :blalalala:

[glendog74]

HAHA laugh it up pint pot :blalalala:

Will do - sherry glass :gayfight: