Retro fit independant rear suspension

[stylussprinter]

Interesting to see, since I am doing similar to my Stylus.
I know it is a track car, but to my uneducated eye you appear to have very little bump travel (and potentially alot of rebound) from those photos... do you run some insanely high rate springs to compensate for under-damping?

DH2

With the power he has up front and running at Sepang , yes , he does have very heavy poundage springs . Having said that , my spring rates are 285 front , 250 rear on my 600kgs car and have even less travel than that up front and just about double his rear travel . Trust me , heavy spring rates don't feel hard on track --- as long as the piston can still ' travel ' in all situations.
We also don't know if those pic's show the shocks in final settings Kelvin will reveal all in due course

[DH2]

With the power he has up front and running at Sepang , yes , he does have very heavy poundage springs . Having said that , my spring rates are 285 front , 250 rear on my 600kgs car and have even less travel than that up front and just about double his rear travel . Trust me , heavy spring rates don't feel hard on track --- as long as the piston can still ' travel ' in all situations.
We also don't know if those pic's show the shocks in final settings Kelvin will reveal all in due course

High rate springs generally limit suspension travel and velocity (to mask poor damping control) - you already state you have very little travel at the front - "the suspension works great if you don't let it"...

DH2

[stylussprinter]

With the power he has up front and running at Sepang , yes , he does have very heavy poundage springs . Having said that , my spring rates are 285 front , 250 rear on my 600kgs car and have even less travel than that up front and just about double his rear travel . Trust me , heavy spring rates don't feel hard on track --- as long as the piston can still ' travel ' in all situations.
We also don't know if those pic's show the shocks in final settings Kelvin will reveal all in due course

High rate springs generally limit suspension travel and velocity (to mask poor damping control) - you already state you have very little travel at the front - "the suspension works great if you don't let it"...

DH2

That was the whole point in using those rates , exactly because they limit suspension travel . When you set out to modify a full bodied kit car for competition use , wheel travel becomes a problem due to wanting a lowered chassis height. The mod's for my car have evolved over 12 years , only 2yrs of that being on road after first build . Arches were innitially made higher then several incarnations of higher again plus flared to cover the tyres , all due to lowering . Along with that came many different shock lengths/spring rates . Regarding ' poor damping ' , I can't agree . Dampers are matched to the car weight/springs and are double adjustable . Many hours of testing in competition led me to the rates and shock settings I now run . These took me from 104 sec's around Goodwood to a 91.8sec's best over several seasons of experimental settings , rake etc.
Velocity wise , I don't actually want fast velocity in a shock , in fact the exact opposite. Springs decide how much travel they'll be but shocks control the transition of that travel --- giving better driver control in extreme situations , perfect for competition. '' Not letting it work '' It's working alright , just not within road driving parameters which of course I haven't done since 2003 .

[Berw]

Not sure how much bump or rebound there is at the moment, I will try and see the car the weekend, I believe that they have 'copied' the set up on the original silvia that donated the uprights, diff and drive shafts, yes the car does have strong springs, can't remember what at the moment as they are in KG, the dampers are fully adjustable, for bump and rebound, booked a track session for the 7th of april for tesing so will know more then.
Tell me why you think the bump is to little, your eys is better educated than mine, (althought I hope not the engineer who built this).
The car does not need much suspension movement as it only runs at Sepang, which is very smooth, although I am hoping to run it at the Macau GP this year, which will be lot rougher.
Kelvin

[DH2]

Firstly, I'm no expert on these things - a little bit of knowledge is a dangerous thing after all



Bump travel appears to be between the two solid lines. You are then into the bump stop until the upper dotted line. The lower solid line to somewhere near the lower dotted line (I'm assuming the length of the piston here for the purposes of example) would appear to be the rebound travel.

I appreciate you are running only on a smooth track, but that doesn't mean you don't need suspension movement to maintain your contact patch.

As I say, I am nothing more than an interested novice, so I may well be mis-interpreting it - I'm sure it will work just fine for you.

Dave

[stylussprinter]

'' Dave DH2 '' ---- one of the points to be aware of with bumpstops is that , in the main , cheaper coilovers tend to have really hard rubber bumpstops so the piston travel available finishes there . Others like mine , for instance , have a much softer compound so can be compressed quite easily up to a point . I can squeeze the bumpstops on my TRAKSPAX double adjusters with my fingers through the spring gaps.
My visable piston travel up front is just 12mm's but can actually move down 25mm's which is ample. As long as the piston doesn't come to a halt on something solid then it's working.

[DH2]

Yep I'm aware that it looks like Kelvin has these progressive bump stops on - but they will become solid relatively soon...

[Craig-Chap]

I did an extremely short stint in the chassis tuning department at work, and found it very interesting how they went about it. In the very early stages of development (steady state) the balance of the car in high mu conditions (i.e., dry) was tuned using a combination of ARB, springs and spring assists (or bump stops). In low mu the car can't generate enough 'lat acc' to hit the spring assists, so it's just ARB and springs in that case. Damper and bush tuning refines the transition phases of cornering and of course ride. One model went through 600 iterations of damper set up alone!

Not sure how relevant that is to the topic but I thought you might find it interesting.

[josephmoore]

Craig, that's some serious patience to fine tune to that detail - I envy those with the attention span to manage it!

[stylussprinter]

That's what it takes but some never bother , even in competition. Personally , I have always enjoyed ' set-up ' and my theories behind it , just as much as competition . In fact competing for me is really to ''proof'' the set-up.

[Berw]

OK Looking a the pictures I am not to worried about hitting the bump stops, say there is 15 mm of movement before the bump stop, that would be 30 mm at the outside of the wheel, (say) and that would be more than enought to foul the rear body, I am going to look at the car on tuesday for the day with tape measue and paper. Also I don't think there is aproblem in moving the shock upper mount up if needed, these are expensive shocks. I was more worried about there actualy being enough rebound travel for the spring to fall out.

[Berw]

Seen the car now, bump and rebound look ok, car is on stands so full rebound is easy to see, and bump kooks ok when on the wheels, currently fitting rear arb

[stylussprinter]

Seen the car now, bump and rebound look ok, car is on stands so full rebound is easy to see, and bump kooks ok when on the wheels, currently fitting rear arb

It would be good to see the final photos of the new suspension once set-up and of course the full body on pics

[Berw]

Ran the car sunday, absolutly fantastic, could not get lap times as a track day and could not get clean laps, and I was not well with alung infection, but the car is much quiker on the long fast right hand turms (3 and 10 due to the longer diff stoping me hit the rev limit) and much faster in the fast turns 6,6 7 and 8 and very much faster throught the dound hill sweepers at 12 and 13 due to increased grip.

It was way faster then the Hicom 'works' westfield zeetecs (they ran 6 with good drivers) and else nothing came close to it it overtook everything. WRX's Evo's 911's Vtec race cars, way the fastest car on the track, now painting and final body mods and I'll put up some pictures

Definitly worth the effort I'm thinking at leat 5 secs a lap,

[stylussprinter]

Ran the car sunday, absolutly fantastic, could not get lap times as a track day and could not get clean laps, and I was not well with alung infection, but the car is much quiker on the long fast right hand turms (3 and 10 due to the longer diff stoping me hit the rev limit) and much faster in the fast turns 6,6 7 and 8 and very much faster throught the dound hill sweepers at 12 and 13 due to increased grip.

It was way faster then the Hicom 'works' westfield zeetecs (they ran 6 with good drivers) and else nothing came close to it it overtook everything. WRX's Evo's 911's Vtec race cars, way the fastest car on the track, now painting and final body mods and I'll put up some pictures

Definitly worth the effort I'm thinking at leat 5 secs a lap,

Sounds great Kelvin Sounds a little like the Phoenix I had a drive in at Abbeville with 300bhp at the wheels -- that was 2lt zetec supercharged/Rotrex . Too much travel (shock/spring) upsets the car on corner entry/exit and what you have , looked ok for track to me. Roll on competition time plus some pics