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Spring Rates
mackei23b - 23/12/08 at 10:21 AM

Ok so I've had my MK Indy running for a number of months and it's time for some fine tuning. At present it gives quite a bit of under steer with just me in the car, it's close to 50/50 between the front and the back axle, general set up includes:

-1.5 degree camber front and rear
1 degree tow in front, 0 degree rear
Dampers – approx 5 clicks front and rear
Chassis Height Front = 10cm, rear = 13cm
LSD Diff

I'm running 200lb springs at the rear and 300lb at the front. I've softened the front dampers, firmed up at the rear etc, but there is still a high level of under steer.

So my next thoughts are with approx 50/50 weight, then the spring should be similar front and rear to get a more neutral balance? I’m certainly looking at the option of reducing the spring rates at the front.

Your thoughts please?

[Edited on 23/12/08 by mackei23b]

Mr Whippy - 23/12/08 at 10:38 AM

my thoughts would be keep the understeer as that’s by far the safest option especially with a rwd car. If you want to drift round corners then just use the throttle, if you over-cook it all you have to do is take your foot off.

You should try driving an oversteering car like a beetle or even my buggy that’ll put hairs on your chest…while you go backwards very fast

Many 4x4s drift totally sideways neither understeering or oversteering and just instead tend to fly off the road so keep it as it is

mackei23b - 23/12/08 at 10:57 AM

The aim at present is to get the car as neutral as possibe. at approx 60mph and understeering, more throttle just pushes the car wider with more understear.

quote:
Originally posted by Mr Whippy
my thoughts would be keep the understeer as that’s by far the safest option especially with a rwd car. If you want to drift round corners then just use the throttle, if you over-cook it all you have to do is take your foot off.

You should try driving an oversteering car like a beetle or even my buggy that’ll put hairs on your chest…while you go backwards very fast

Many 4x4s drift totally sideways neither understeering or oversteering and just instead tend to fly off the road so keep it as it is

Wadders - 23/12/08 at 10:57 AM

It does sound a bit over sprung for a bec. IIRC my ST ZX9 has 170/220 springs.
Have a word with Hellfire r.e handling mods and spring rates etc.

Al.



Originally posted by mackei23b
Ok so I've had my MK Indy running for a number of months and it's time for some fine tuning. At present it gives quite a bit of under steer with just me in the car, it's close to 50/50 between the front and the back axle, general set up includes:

-1.5 degree camber front and rear
1 degree tow in front, 0 degree rear
Dampers – approx 5 clicks front and rear
Chassis Height Front = 10cm, rear = 13cm
LSD Diff

I'm running 200lb springs at the rear and 300lb at the front. I've softened the front dampers, firmed up at the rear etc, but there is still a high level of under steer.

So my next thoughts are with approx 50/50 weight, then the spring should be similar front and rear to get a more neutral balance? I’m certainly looking at the option of reducing the spring rates at the front.

Your thoughts please?

[Edited on 23/12/08 by mackei23b]



[Edited on 23/12/08 by Wadders]

Mr Whippy - 23/12/08 at 11:16 AM

quote:
Originally posted by mackei23b
The aim at present is to get the car as neutral as possibe. at approx 60mph and understeering, more throttle just pushes the car wider with more understear.


what I did with the Falcon was simply adjust the toe in, done in a wet car park so once set and I have my foot flat to the floor it drifted sideway but the car never tries to spin round. No need to bother with different damping or spring rates (non adjustable anyway), all done with like I say just the toe in. Simply turn both sides half a turn at a time and try it out, one way you'll find the car will overstear the other under. Once sorted you'll be able to confidently scream round corners (even in the wet) flat out as I've done round the top of Scotland (super twisty roads )

mr henderson - 23/12/08 at 12:15 PM

quote:
Originally posted by mackei23b

So my next thoughts are with approx 50/50 weight, then the spring should be similar front and rear to get a more neutral balance? I’m certainly looking at the option of reducing the spring rates at the front.



Bear in mind that the front springs are at a much greater angle to the direction of travel of the pivot on the bottom wishbone than are the rears, which will be almost in line with the deflection of the rear suspension.

In effect this means that for a given amount of suspension movement, let's say one inch upwards, the front springs will be compressed by only about half of what the rears will be. So equal springs would not mean equal effective spring rates.

Personally I would follow Mr Whippy's advice and experiment with the toe first.

John

[Edited on 23/12/08 by mr henderson]

Kriss - 23/12/08 at 12:33 PM

I am in the middle of doing exactly the same.

First thing first is to ensure that the clicks on your coilovers are equal and paired.

I have just had mine revalved and balanced so say 5 clicks on one side is the same as 5 clicks on the other. If you have Protech shocks I would advise this.

me and my mate have done to rough calculations and we feel that the front springs are way too overated and could be dropped easily into the 200's or less.

I would also look at tyre pressures on your current set up, especially if you are using a semislick.

fianlly, are all of you settings done with no driver or passenger, as your weight will throw your settings out a tad too.

mackei23b - 23/12/08 at 02:46 PM

I've got matched GAZ shocks all round, set to 5 clicks. Tyre pressures are set at 18PSI, I've not played with tyre pressures yet.

In addition, perhaps should have mentioned this earlier, there is also an undeven build in temperature across the front tread, hotter towards the inside. Again all points to the front tyres not working as well as they could.

Axle weights are with the driver only, but the car has not had the corner weights done yet.

Cheers

Ian


quote:
Originally posted by Kriss
I am in the middle of doing exactly the same.

First thing first is to ensure that the clicks on your coilovers are equal and paired.

I have just had mine revalved and balanced so say 5 clicks on one side is the same as 5 clicks on the other. If you have Protech shocks I would advise this.

me and my mate have done to rough calculations and we feel that the front springs are way too overated and could be dropped easily into the 200's or less.

I would also look at tyre pressures on your current set up, especially if you are using a semislick.

fianlly, are all of you settings done with no driver or passenger, as your weight will throw your settings out a tad too.

PAUL FISHER - 23/12/08 at 05:50 PM

I did quite a bit of experimenting with spring rates with my 1st Indy for the track,I found 175 front,and 275 rear worked best,this reduced the rear end body roll you see with so many Indys on the track,and help it turn in better eliminating understeer,the 300 springs for the front of the Indy are too strong in my opinion for a BEC,the ride on the road with 275's on the rear, is a little firm on the road,but worth the trade off in my opinion for better track performance.