The Underdog

Does anyone have any ideas on how I can DIY make my focus rear arb stiffer please.money doesn't allow me to buy a whit line before my next track day so what can I do to the standard one please?
Ive thought of welding on to it to stiffening it but read on net it's sprung steel and heat would ruin it. Is there different drop links I could use?

Any safe ideas appreciated

Thanks.

Rowe

you could cut the ends off and replace the centre part with a thicker piece of pipe.

the_frozen_one

iTrader: (1)

The heat of welding the pipe in might distort the sprung steel.

Don't think there's much you can do to be honest, there's no easy way to make adjustable links either.

Over inflate the rear tyres, will induce oversteer like a stiffer arb

The Underdog

thanks for replies. i already run rear tyre higher than front but im looking for added grip to the front not losing grip to the rear.

iv got an idea of spacing the anti roll bar mount bracket 25mm out then drilling a new drop link hole 25mm further up bar. this i think should give a stiffer bar like an adjustable arb. what do you think?? will it work??

Stoka

what about another mount in the middle to stop the bar moving up/down in middle ?

GVK.

In theory it will work if it all lines up.

When you get an adjustable ARB there are mounting holes for the links, which allow the 'lever' part of the ARB to be shorter hence making it stiffer.

This is my Golf one. (this was in the middle setting, there are 3 holes)



Does an RS have a thicker rear ARB?

foreigneRS

it will work, but could be too drastic a change. what is the length of the lever now, and what will it be after you've reduced it by 25mm?

smudger068

You have said you want more grip at the front but not change the back?
So why would you adjust the rear anti roll bar?
Why would you not go to the issue at the front, on what part of the corner are you under steering (initial turn in / mid corner / exit) ?
Whats your spring rate ratio from front to rear (is your front to stiff)?
Are you getting weight transfer onto the front (Is the back to soft front to stiff)?
Tbh I have seen some of your video you posted before and it does look like the back is too soft, possibly why you feel comfortable with the grip level on the rear

Just a thought even if you glance into your profile pic, assuming that is the same setup as that car, then the rear rate is too soft!

The Underdog

thanks. im not sure what the rs is to be honest.


i havent measured it yet as its just ideas stage but it could be reversed if too stiff.



iv been told a stiffer rear arb is a great mod for this car so thats my reason.for a fwd i cant really complain too much about front grip as its very good as it is but if it can be better i want it lol

my springs are 392lbs front and rear. i have 30 settings on shocks and found 17 front and 25 rear best so far. any less on front and it understeers more. its far from soft on the rear. it barely moves if i bounce on it. not scientific but its stiff lol also they are BC racing coilovers.

i have around -3.5 camber front and rear. thats max on front and gives best grip in my testing

the car in my sig is not the my track car thats my other car that is bog standard.

thanks for watching my vids and everyone for all replies.

smudger068

Okay but to what point is it a great mod, for a standard road car or a race car...
Okay so your front spring rate is stiffer than your rear (because your rear has a motion ratio of say half (guess!!) then you square root that which will give you an even softer rate!)
Are you hitting the bump stops on the front of the car under braking? have you lowered the vehicle so the wishbones are more or less parallel (front) ?
Yeh 3.5 sounds good but that's upto u to fine tune depending on tyre wear and heat across the tyre!
Yeh do not use your dampers to change understeer and oversteer of the vehicle (its not what there for!!) use them so the springs and your suspension system rides the road surface accordingly
sorry I got carried away lol

The Underdog

you lost me on the first maths bit lol. not hitting bump stops and wishbones near parralel.
i have a different opinion on shocks to you and most of the tuning articles i read. shocks are a major component in controlling handling of car but not many people understand how to fine tune them.im still learning.

thanks for all the input

smudger068

haha, motion ratio in google will help you
Excellent
yes they are a major component in controlling handling of a car but don't actually use them to adjust your understeer or over steer of your car.
A wheel hits bump if there to stiff it can cruise over it loosing grip.... if there to soft the vehicle can oscillate (unstability) fine tune them through steering input and feeling what the car does over the service.
They are also a critical factor especially in the likes of WRC cars all you gotta do is watch a WRC jump and when it lands all 4 wheels end up in the same position unlike jump a school car 9/10 in ends up in the tree! because the dampers can maintain the control of the spring from excessive oscillation

Personally I think the rear end of your vehicle is way to soft! its probably why its said that the anti roll bar upgrade is a better option because of the stiffening of the rear.

The Underdog

i dont understand how the rear is considered softer? the front has 62% of the cars weight and rear 38% so the rear is taking less load than the front on a same spring rate. what am i missing? not many kits are sprung this stiff at the rear so i considered this better than most.

i love researching geometry and handling and discusing it but you are one of a small minority who understand or talk about it on pf so thanks for that.

smudger068

Its why you need to understand motion ratio to wheel ratio
The front uses a McPherson strut setup give or take its normal gives a 0.9 ratio
So say your spring ratio for arguments sake is 100. The spring rate at the wheel will be 99
The rear uses a trailing arm setup so give or take (on a Honda civic type r) its 0.5
So
100 divided by (0.5 squared) = 25

Front = 99lb spring
Rear = 25lb spring

So the rear of the vehicle is softer

You can simply measure the motion ratio by lifting the rear wheels off the ground
then take the wheel off
measure spring length (e.g 100mm)
jack the wheel up 10mm
Remeasure spring length and it will be different than 10mm
divide these two and it will give you your motion ratio

http://www.hypercoils.com/spring-rate-calculator/

use this link and it has definitions at the bottom
if its all confusing its okay I just spent 3 years at uni and 2 on a suspension project haha

it will also show you how to measure your rear motion ratio if your unsure I can also check for you by using my focus

nevsrevs

What you have to remember on the rear mate is leaver input, we run a inboard spring so your getting a different force rate to a true coilover,

When we where running a 800lb rear spring with no arb the car was very lose on the fast corners, now with 550lb rears and still no arb the car feels the best it ever has, so predictable,

If you want to try some different rates I have 3 pairs of springs you can try.

The Underdog

iv spent a few years playing forza motorsport on x box so cant compete with your uni knowledge lol
im starting to make sense of it though so thanks


and in pops my other source of knowledge. lol. yes that makes sense how you describe the lever effect rog. hadnt thought of it like that.

what other rate springs do you have rog?? get yourself booked in to combe on 30th and i can steal your wisdom and see your car.

the whole idea of me doin this to arb is its almost free to try it and if i dont like it i can put it back in half hour.

cheers both

smudger068

haha the amount times I tested a lambo around brands hatch before I started uni on need for speed haha
Sounds a plan
Good luck

nevsrevs

Car is in hibernation for now mate, but might be able to drop the springs up to you to play with, got some 800lb at 2 different heights and another pair of 600lb I think, will have a dig,

You could cut up another bar and clamp it to the middle of you one, then try running the car without it, just to please me lol.

The Underdog

rog the car needs to come out of hibernation on the 30th. there some jap cars you need to take down.
really appreciate offer of springs, your a top man. im going to give this mod a go and see how i get on and see from there. ive picked up some peices of alluminium for the spacers and removed arb tonight to take bolts to get a longer size then its just a case of drill arb and test. should have it done on or by wkend.

The Underdog

well iv done it and it works well. cost was around Ł11 for bolts and drill bit so very cheap mod. il get some pics sorted and update my build thread with it when i get chance.

Straight_4_N/a

Fit a second anit roll bar just below the std one.
or /and
fit stiffer anit roll bar bushes.

The Underdog

iv already got poly bushes. the mod works well so im happy as is. drifts nice on the roundabouts.