Handling off balance - H&R roll bars?

[BMracing]

When we fitted h&r roll bars to our 4 door, I wasn't sure of the best setup for them, so I fixed them to the middle setting front and rear. I guess it partly depends on driving style but i find it a bit tail happy under braking and particularly hairy in the wet.
I have a front strut brace on order for it, would this have a significant enough effect, or should i set the front roll bar to the stiffest setting as well? I know its not always this simple but it just doesnt feel quite right at the moment, its very difficult to trail brake, or even just brake hard in a controlled manner!
Just wondered if anyone has had a similar experience with these roll bars.

Cheers,

Max

[agent006]

I've got my H&Rs on the tightest setting and have no problems with the back end. Maybe try tightening the front or loosening the rear (not both at teh same time though).

[hoshy]

Alright max - how are things?

I run mine on stiffest on the rear and middle on the front. With my suspension (spax psx) set to softest on the front and middle on the back... This leaves it slightly less prone to the understeer and I've not had any real trouble with heavy braking (ds2500 pads) as you saw it seems to handle pretty well like this. Having said that, it's more set-up for road driving than very heavy track work so that could be a factor.

Might be worth having a good 4 wheel alignment too.

[Onz]

what speeds are you driving at? Does your car have an interior, cage, what wheels? what suspension do you have?

Generally it sounds like your shocks are worn.

[march109]

Mine are set hard rear and middle fronts, my back end is pretty low so is pretty jittery anyway,but sticks better than it did on stock arbs. Mine is road based though so no real usefull comparison.

[ian332isport]

When I first fitted my H&R bars, I had softest on the rear, and middle on the front. It was okay, but not great. Moving the front to the stiffest setting made a huge improvement.

Ian.

[shorty73]

If the back is hairy in the wet the rear is too stiff.

Most racers either run the rear on the softest setting or completely disconnect the links altogether.

You should get the spring rates and damping right then fine tune with an AR bar. Look at the last paragraph in this in particular.

Taken from Carroll Smith's Cause and Effect Guide

ANTI-ROLL BARS

Too much anti-roll bar: overall
Ӣ Car will be very sudden in response and will have little feel
”¢ Car will tend to slide or skate rather than taking a set ”“ especially in slow and medium speed corners
Ӣ Car may dart over one wheel or diagonal bumps

Relatively too much anti-roll bar: front
Ӣ Corner entry understeer which usually becomes progressively worse as the driver tries to tighten the corner radius.

Relatively too much anti-roll bar: rear
Ӣ If the imbalance is extreme can cause corner entry oversteer
”¢ Corner exit oversteer. Car won’t put down power but goes directly to oversteer due to inside wheel-spin
Ӣ Excessive sliding on corner exit
”¢ Car has a violent reaction to major bumps and may be upset by ”˜FIA’ kerbs

Too little anti-roll bar: overall
Ӣ Car is lazy in response, generally sloppy
Ӣ Car is reluctant to change direction in chicane and esses

Relatively too little anti-roll bar: front
”¢ Car ”˜falls over’ onto outside tyre on corner entry and then washes out into understeer
Ӣ Car is lazy in direction changes

Relatively too little anti-roll: rear
”¢ My own opinion is that on most road courses a rear anti-roll bar is a bad thing. Anti-roll bars transfer lateral load from the unladen tyre to the laden tyre ”“ exactly what we don’t want at the rear. I would much rather use enough spring to support the rear of the car. The exception comes when there are ”˜washboard ripples’ at corner exits, as on street circuits and poorly paved road circuits.

[Onz]

nice and precise description shorty73

That sounds like quite a straight forward book.

Another thing I noticed was that BMracing was commenting on the car being very hairy in the wet and when he tried to trail brake. I always thought that the point of trail braking was to lose the backend a little.

[BMracing]

Thanks for all your info and opinions guys.

Hey Ash, good thanks. Hope you and Cath are well. Your car certainly did dart around nicely in the highlands, some neat driving by you as well though! Interesting how you and march109 get on with that setup and Ian favours the stiffer front end. Unfortunately i have no adjustment in the shocks
Thanks shorty79 for that useful info.
It seems the general concensous is that stiff rear roll bars or even rear roll bars at all are not a good idea for much harder driving/track use?
Onz the shocks are h&r cup and are less than 2 years/10k miles old so should be ok, havent seen much track use as yet.
Indeed when trail braking you use the back end to help steer the car in to a corner as the weight/grip is transferred to the front, and increase steering wheel input as you release the brakes. The effect just seemed a bit extreme when i was at brands last month, had a fair bit of opposite lock on a few times on the way into Graham Hill. It may just may be me being a bit heavy handed, and i was able to get more and more out of the car as the day progressed, but still never felt 100% confident in the rear end grip.
I'm know master but I felt more confident in the handling at Snetterton, i know its a very different layout, the only difference in the car since then is that we now have 50 profile tyres as oppose to 45 profile.

[Simon13]

the rear end doesn't need to be uber stiff. On my touring i used to use cupkit springs with hartge roll bars. the front is the same as the H&R bar and i used it on the stiffest the rear was fixed though and 16mm.

she used to turn in neutral, would only understeer if you where going in way to hot, but most cars do that. Ease off the throttle and it would immediately turn in

[Jon_Bmw]

I've always understood that in the wet, most people back the stiffness right off in the rear or indeed disconnect them totally. Currently messing around with 205's on track and taking a roll bar out of the picture in the wet is a good 40 min job. So i haven't done it...yet.

[Simon13]

on a trailing arm car like an E30 if the rear bar is too stiff it actually will stop them moving opposite ways when cornering hard. so being a hinderence

Some of the ring guys use H&R coilovers in nurburgring spec with standard roll bars front and rear, but i expect they have nice welded in cages so the shell is soooooo much stiffer than a stock road car that they just aren't needed as much

[oze30]

Mine was fine with softest setting front, stiffest rear (H&R rollbars, 3 hole front, 2 hole rear), Sparco strut brace and it tracked fine and actually handles damn well considering the weight and the engine mounts I'm using (Pug at almost 3 inches tall, dropped subframe). I'm going to lower it all again when the hockey pucks arrive, and then raise the subframe back up to normal.

I tried mine in the middle hole at the front, furthest from the front on the rea (stiffest IIRC) and it would understeer more.

Im running H&R -35, Bilstein B6 fronts. stock rears, soon to be matching sport billies in the rear.

[handpaper]

Indeed, Simon, with proper spring rates you don't need much anti-roll at all. I have the standard 12.5mm rear and a stiffened 20mm front (equivalent to a 21mm bar) and all is rosy and controlled.

According to theory, ARBs will always reduce overall grip, since grip is greatest when the load is shared evenly between the two wheels on an axle and an ARB will tend to lift the inside wheel, reducing the load on it.
This is why it is common for racers to disconnect the rear bar in wet weather - the roll centre moves backward and the car may understeer more, but rear traction is improved.