Spring rates.

[guilleracing]

Looking to improve the grip on the seven. It is an Ital axle car.

 

Planning to upgrade the spring rates,

to 400lbs front and 275lbs rear.

 

What do the experts think?

 

 

Greg.

[OliverSedlacek]

Don't do that! IMO stiff springs ruin a seven, and the chassis isn't terribly stiff so they don't even work that well. If you want more grip get some stickier tyres. If they are more than two years old, ditch them even if they've got plenty of tread left.

[James_Russell]

Classic Grad race cars with heavy vauxhall 8v engines run 225lb front and 140lb rear. As far as I'm aware, very stiff strings aren't viewed as advantageous on a live-axled car because you tend to see greater yaw angles and greater differential between the front and rear slip angles on these cars. Stiffer setups make this attitude harder to acheive/maintain, it would also negatively effect wet cornering and of course comfort.

Check your set-up is roughly right and experiment with tyres, as Oliver said.

 

Q41 ACF Classic Grad #98

[Richard Price]

Greg,

Your question is a bit too open.

 

What engine do you have?

What tyres are you planning on using?

What is your intended use for the car?

What consfiguration is your front suspension?

 

Whatever you intend, 275lbs/in rears sound incredibly stiff (unless its a drift car!)

 

 

 

Edited by - Richard Price on 16 Sep 2010 12:00:51

[tiddy1]

Don't do it, those spring rates will really not improve the grip of your car, as said you really do not want to go above 250 rear/140 front.

 

You state you want to improve 'grip' but what do you mean?

 

if the wheels are spinning in a straight line then its just tyres

if its a question of understeer you are better off putting more -ve camber on teh front

 

if its oversteer then increasing Front ARB stiffness

 

Simon

[jonboylaw]

Max 150lbs on the back and even then be prepared to be bounced all over the shop, 115lbs work well and I run 300lbs on the front (xflow engined car).

 

Tweek the dampers and sort the ride height, also as suggested, get some grippy rubber.

 

 

 

Jonathan

=========================

My Flickr Gallery

 

92 Supersprint, Ford LSD LA, RK AX Crossflow. Stealth model (Matt Black and Ali), rebuild completed.

 

[bstark]

I'd second that - also on a live axle xflow. From memory I think I've got 270lb front and 105lb back (whatever Redline recommended as a good track / fast road compromise - it was a few years ago now).

 

If its grip you want I'd be looking at tyres and dampers first. I was amazed at the difference a set of GAZ adjustables made compared to the old Spax, which it turned out weren't working at all at the back .

 

Everyone told me live axles were a bit lively so I just assumed TADTS - explained several hairy moments sprinting at Lydden. A tad more controllable when the back is damped

 

If the car is rolling too much and that needs controlling then the springs are your friend. FWIW my car is now a delight on the road (on AO21Rs) and won its class in the local sprint championship (also on AO21Rs, but I found several seconds through experience, switching to R888's, adding working dampers and an ATB) - all with the above spring rates.

 

Bob Stark

Supersprinter

[Paul Deslandes]

Greg

 

I have 120 on the rear and 275 on the widetrack front with the Vx engine. Effective rate on the front is about 82 mid-range.

 

Paul

 

 

[guilleracing]

Hi Guys,

 

Thanks for all the replies. I have, ( as Paul knows.) a crossflow 1600 seven. No trick parts on it whatsoever. This year I only just managed toscrape a win in the 1600 class at the annual Jersey Historic hillclimb at Greve de Lecq. To say I was driving the wheels off it would be an understatement. I had a lot of really "Nasty moments" so I have decided to do some upgrades. The comentator convinced my wife that I was seconds from disaster the whole way up. Yes the tyres are cheap copies of a Pirelli P6 and as hard as lorry rubber. (Evidenced by wheel spins into 3rd with a stock 1600.) I am going to invest in new dampers and springs as well as a new set of tyres. The reason I was looking to go so hard is because the car on its original springs on the rear is bottoming out a lot and fully extending the unloaded side to the point where I can feel the spring unseating! The body roll is very bad. I am also looking to convert the front suspension to someting more stable than the original with the anti roll bar being the top link. I can see it bending under hard braking! All that said I do like stiffly cars, being a single seater driver for my many sins. I think I will try Pauls settings as I have seen plenty of his videos and his car seems stable.

 

 

Thanks once again.

 

Greg.

[James_Russell]

For the 1997threads on this if you seach Techtalk- It is a relatively inexpensive and simple mod which (I'm told) improves the stability of the car, particularly in controlling 'pitching' forward under heavy braking. Once you've done it you can also use a selection of Narrow-track ARB's (De-dion type).

The modification is bolt-on and can be bought as a kit from Redline components. The only thing you'll have to do before it'll fit is cut a slot in the side-skin on each side for the front half of the wishbone to bolt to the chassis.

If the flex your experiencing is because of the chassis, changing the springs won't help (much)

 

EDIT: This Picture from when I first bought the car shows what the upgrade looks like...

 

Q41 ACF Classic Grad #98

 

Edited by - James_Russell on 19 Sep 2010 21:39:19