[trackday_prep] Cameron's Mi16 / Gti6 Hybrid

[Cameron 16]

Cool, we're gonna end up with pretty much the same car soon!

 

I think I'm gonna get myself a thicker rear ARB next, what's yours running? Have you still got the extra one too?

[oli-pug 6 2 Cars]

Haha well the proof is in the pudding as they say, it's just what works to make a good track car ain't it fella!

 

Anti-roll bar!!! I thought that was a swear word to you I'm running a chopped down/ end plate welded on gti-6 24mm bar in the beam as well as a Whiteline adjustable bar. Definitely handles better around a track with the rear end as stiff as poss in my opinion. Back lanes can get a bit interesting though!

[Cameron 16]

Haha yeah I know! BUT, I've been doing all this crazy suspension design stuff for my spaceframe project and well.. looks like it's not such a bad idea after all. I'd always been thinking that encouraging weight transfer was a bad thing, but I reckon it should actually help the front out quite a lot. I'll see how it goes when I try it I guess!

 

Not gonna go mental on it, I think 24mm should be fine for me but I'll see how I get on.

[Spiky 37]

regarding ARB

 

i have 300lb front with 309 ARB

 

rear i have std TB with 24 ARB on a 309 beam

 

i did have a bit of understeer, then i fitted the 24mm ARB and it pretty much eliminated all of it

[Cameron 16]

You should definitely get some thicker TB's on the back, it makes a pretty surprising difference!

[edbar 6]

would you say to get the tb's done first or arb? I wanted to get the tb's then try a bigger arb after in case it didnt work out, thought increasing the spring rate first would be best?

[Cameron 16]

I'd say torsion bars first, especially if you've fitted stiffer springs up front.

[welshpug 1,626]

depends a lot on how you like the car to behave and how the whole package is looked at, some build chassis arrangements without any ARB's at all and they work very well.

[edbar 6]

Camerons car seems a nice balance(watched the ring vids), mine is very neutral at the mo and want to keep that, then play with balance see if i prefer it.

[Cameron 16]

That's absolutely the right thing to do. The reason I've always disliked the use of thick rear ARB's is that I think every effort should be made to get as much improvement in grip out of the car before you go degrading it by fitting ARB's. I really like the balance of mine at the moment, but I'm pretty positive that the increase in rear camber I'll get with the SBC tub axles / ZX arms combo will put the balance back towards understeer, so a bigger rear ARB will definitely help things out.

 

But yeah, 100% agree that it's your car and what you fit to it depends entirely on how you think the balance is. BUT I would definitely recommend thicker torsion bars if you have stiffer front springs.

[Spiky 37]

is there a formula for working out the right TB in comparission to front springs used?

 

i.e

 

300 front springs tb size?

325

350

400

 

i have 300 but may try slightly harder at some point

Edited April 26, 2011 by Spiky

[Cameron 16]

Somebody posted a table of the comparisons last year, I remember re-posting it in a thread but can't remember what one it was.

 

I have 350lb front springs and it worked out that I should be using 24mm TB's, if you've got 300lb and thinking of going firmer then I'd probably recommend going for 24mm too.

Edited April 26, 2011 by Cameron

[Spiky 37]

ok cool,

 

something to think about then

[welshpug 1,626]

Quite difficult toquantify specifically I'd imagine, corner weighting will help as the front-rear balance does vary, I'd like to find out the same but for a ZX or 306 chassis.

 

I'm fairly sure Sandy has posted something about this a while ago, though it might be on the 106 RR forum.

[oli-pug 6 2 Cars]

I'd agree with cameron on this, always a good idea to start with the spring rates and damping to create a car that is as neutral as possible and doesn't become unsettled on kerbs or bottom out anywhere.

 

You can then use the anti roll bars to adjust the balance of the car to suit your driving style and the circuit in question i.e its layout, track surface and the weather conditions.

 

If a track has a lot of long sweeping bends and long straights like snetterton and silverstone, i like to run the back end quite loose and adjustable with the throttle without having to make any steering alterations. This way, as long as you're confident with the car, you can carry more speed through the bend and onto the straight.

 

If a circuit has tight and twisty sections with switchbacks like cadwell for instance, you probably want a more neutral balanced car to avoid any nasty oversteer moments. I tend to use a slow in fast out approach with these, get the front tyres working and the car balanced then using all the track available to keep your momentum up.

[Cameron 16]

Yep, that's definitely the right approach.

 

Wheel rates for torsion bars are going to be very tricky to calculate, it'd be much better to measure the wheel rate using a force gauge and jacking a wheel up. I'm not sure if that's how the data in this table was collected (it came from a Swedish guy iirc..) but it gave values for wheel rate which makes me thing it was measured rather than calculated. Either way, the wheel rate for 24mm tb's was slightly lower than the front wheel rate with 350lb/in springs, which is what you want for a track / race car (a difference in front and rear ride rates is a good idea to stop the car see-sawing over bumps, and having the front end stiffer improves turn-in response).

[Cameron 16]

Ready to go!

 

[Mad Scientist 106]

Nice to meet you the other day Cameron. Hope you got home OK.

 

I timed some of your laps, first session out after the fuel. Let me know if you want to know them!!!

 

Pete

[Cameron 16]

Yeah was good to meet you too! Got home fine, dosed up on coffee before I got going so I just about managed to stay awake.

 

Oooh yeah go on then.. (racing driver excuses coming up) I think my times were quickest in the very last session, I was trying to get the braking and turn-in points for turn 1 right and eventually got it nailed in the last 5 laps or so.

 

Was a brilliant day, I got off to a bad start when my battery went flat in the que for sighting laps.. then I had to get all the people to reverse back so I could get out of the que! Then I had a bit of a scary half-spin 2 wheels moment when I was trying to heel-toe into the Shell Hairpin and accidentally stamped the brake.

 

Eventually settled down though and was loving it so much I ended up doing a couple of 40 minute stints towards the end of the day! New clutch and flywheel has made so much difference to the way it drives, and it's actually really really manageable. I did find a few problems though, the biggest being the bump steer, which is pretty bad! Makes it very difficult to commit in the really fast bumpy bits as the car wants to dart about, so I'll definitely be looking to fix that before I next go out.

[Mad Scientist 106]

2m10.1 (first lap after outlap)

2m9.0

2m8.2

2m7.3

2m11.2 (saw you stuck behind some traffic)

 

At this point we headed off for a coffee!

 

Pretty good times there Cameron. For reference, the Escort Cossie rally car, with a service crew, was doing 1m58s and right on the edge.

 

See you at a track soon, hopefully when i'm taking part!

 

Let us know how you get on with the bumpsteer so I can steel your solutions!!!!

 

[Cameron 16]

Cool, that's a pretty good improvement rate!

 

I reckon I might have knocked a second or so off that by the end of the day, I was getting a lot braver particularly in the first corner and the fast left between Cascades and the hairpin. Thanks for timing!

 

Yeah I reckon I just need to raise the steering rack by 40mm or so, not sure how plausible that is with the standard pedals in the way, but we'll see!

Edited April 28, 2011 by Cameron

[EdCherry 34 1 Cars]

Would be easier to move the arms down 40mm than moving the rack up I would have thought.

[Liquid_106 97 1 Cars]

Could you mount your TREs to the underside of the hubs, so in effect raise your rack and lessen the bumpsteer?

[oli-pug 6 2 Cars]

Could you mount your TREs to the underside of the hubs, so in effect raise your rack and lessen the bumpsteer?

 

That's how they are standard

[Liquid_106 97 1 Cars]

That's how they are standard

Sorry, had a 'moment' there - was thinking of a Nova :S