Obviously this topic has been done before, but i wanted to more directly address the trade-off.

ie, i see as a trade-off between more fine-grained steering control (non-quick rack) vs. the ability to more quickly get to the steering position you want (eg, correcting oversteer more quickly).

Have i characterized it correctly?

Also, i have a Fiesta (89-99) steering rack...does anyone know the number of turns lock to lock? I am actually hoping for compromise of somewhere around 3.0. Good choice?

TIA. Cheers, -sm

I orginally built mine with a slow rack, and she was fine except on track when I was getting out of shape a lot. I had to take hands off the wheel a lot. Not ideal, one of the causes of me dinging a barrier at Kirkistown.
Rebuilt with a quick rack, car is similar to drive on the road, I haven't noticed any major issues really, but on the track she os a lot more controllable when getting out of shape.
I'd go for a QR again, but if you're car is only for the road it might not be worth the money.

I forgot to mention my new QR isn't really really sharp, it's about 2.8 turns lock to lock (from memory).
The old one was (again I think) 4 or so?

Similar experience here as I'm now on my third steering rack.x

First was a standard mk2 Escort rack, hopeless on track and on full lock either side the wheels hit the chassis rails (Striker). Then fitted a 2.4 QR which was great on track but quite nervous on the road so you had to concentrate all the time.

Final configuration is a 2.9 QR which is a good balance between road and track. I've had to relearn how much lock I need on track to catch it but its fine once you're "dialed in". The wheels don't touch the rails on full lock.

I have a quick rack and notice no problems on the road. It isn't twitchy and is generally well behaved. I would fit a quick rack every time.

Hi agrred whith smart51. It can take time to smooth your self out and get used to the QR but is usually always wort it.

The reason bimbleuk you may be having trouble is that dont forget that strikers are verry short wheelbace and twichey at the best of times but playing with the tracking can sort that out tho.

cheers matt

How quick is quick? I don't like the term "Number of turns lock to lock" This depends how much lock you actually have. And the same rack will be quite different on cars with diferent steering arm length. I quickened the steering on my car by making new (shorter) steering arms. I have seen racing saloon cars having their steering arms changed at the track to improve theur handleing. Sometimes I have seen the overall steering ratio quoted, which is, I guess, the number of degrees you turn the wheel to get the wheels to steer one degree. Typically I think this is about 20 - 30. When shopping for a rack I measure how much it moves when you turn the wheel on complete rotation. Typically they move about 50mm. 60mm for a slaoon car seems to be about as fast as you get. I have noticed Alfa and triumph herald as being relatively quick, but the real gains are from shortening the steering arms. My car is about 2.2 lock to lock, but it is not a very tight lock, about 32 degrees on full lock. This is a bit extreme for a 2.1m wheelbase, but I love it. Anyone got some real verified data on rack ratios? Cheers, Brian

2.4 quickrack for me.

I don't have much experience in a seven, but in a number of road and competition cars, 2.4 racks seem to be very stable on the road and quick enough on the track.

Quicker still is nice but can be very heavy at low speeds.

To put it in perspective, my grasser has 0.8 turns lock to lock and much more lock than a locost (grasser has approx 60 deg) , and is still driveable (though rather darty! ) on tarmac.



grassersteer4

Bear in mind that a standard sierra with power steering is 2.8 turns lock to lock and that is not exactly demanding to drive in a straight line!!!!

[Edited on 20/10/06 by NS Dev]

0.8 turns lock to lock and 120 degrees lock to lock at the wheels. Thats a steering reduction ration of about 1:2. Am I understanding you right? The pinion would be about 4 inches in diameter. ???

"Twitchy" is a condition caused by poor castor or bump steer caused by the wrong position of the rack.
Having a "quick rack" does not cause a car to be twitchy.
If bump steer is ok and you have enough castor, then it doesn't matter what rack you use.
My Titan rack is 1 1/4 turns lock to lock and it is no problem at all.

Maybe the poly bushes in my upper rocker arms were causing the twitchyness as they were starting to bind. Ive since fitted the 2.9 rack and spherical bearings in the rockers arms which has made the front much more stable.

Same geometry settings though.

[Edited on 20/10/06 by bimbleuk]

quote:

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Originally posted by Ratman
And the same rack will be quite different on cars with diferent steering arm length. I quickened the steering on my car by making new (shorter) steering arms.

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quote:

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Originally posted by nitram38
"Twitchy" is a condition caused by poor castor or bump steer caused by the wrong position of the rack.

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There is another factor I've discovered after changing to a quick rack - not "twitchy" as such, but there is a requirement to be more alert, as it is easy to wander if you don't pay attention to keeping it straight!

David

Personal choice but as stated before, a QR can get you into more trouble than it can get you out of by over correcting.......

I would suggest if your sliding the car around on track (too the extent you have too take hands of wheel too correct it) either the car needs a good dose of setting up or driving style needs a dose off looking at. Not suggesting it would never get that sideways but as a norm it shouldn't, not if your looking for speed anyway.

I know a lot of quick drivers slide the car but that's all 4 wheels and controlled with the right foot not the steering wheel.

<---------The pic on the left, hairpin at Mallory, tight as it gets, std rack, hands never off wheel, turn in and allow power too take the lock off coming out.


Runs off and hides for cover........

I've got one of rally designs 'in-a-slght-hurry' racks. The 2.9 turns is nicely in the middle of the standard 3.4 and the quick 2.4 so a nice compromise. And best of all they are dirt cheap from rally design compared to the quick racks.

Liam

Final steering ratios are done by comparing wheel rotation to degrees of axle turning. IE if one turn (360) of the wheel gets 20 degrees of rotation, 360/20=18 or 18:1.

Racks are also done by degrees per inch or something.

Quick ratio racks are "always" better when driving hard but there is always the sneeze factor. Any lack of attention (like a sneeze) and you are in the next lane or worse. Even my camaro with a 11:1 (2 turns lock to lock) you had to pay attention to and I would consider that as slow as you can have for fast driving. Ive also had very slow ratio boxes in trucks where I have literally taken the wheel and thrown it around as hard as I could to get the wheels to turn fast enough to keep my ass out of the ditch while fishtailing (didn't work one day http://www3.telus.net/public/corym/crash/ )

Anyhow long story short, you need to look at your intended uses and plan accordingly. It is a comfort thing. I like 2 turns lock to lock for a street toy personally.
Even at that, once I spent a week driving the 1ton truck with loose steering on a work trip. Came home tired at 2am (23hr day) and got in my camaro to drive home. When I let the clutch out to enter the road I found myself about to go into the ditch (wasn't used to the power anymore) then corrected and found myself aimed at the curb on the other side. A few blocks of swervy driving and I was used to the car again but it shows you how quick you get used to something else .
Cheers.

[Edited on 21/10/06 by C10CoryM]

Wow...thanks for all the replies!!! Is really helping me think about the alternatives. I really like Jon's point about almost never needing to take your hands off the wheel on a race track, and that you shouldn't really be getting sideways (unless ur messing around! ).

On the other hand, my racing experience is in go-karts...hmmmm...and i just measured that Ford Fiesta rack. 4.25 turns!!! Seems a bit extreme.

However (please excuse my inexperience), what do i look for in a replacement. Note, this is for a lhd US car. The fiesta rack that i have is rhd rear mount rack that is meant to be turned upside down and front mounted for this application. Probably not the best choice, besides the 4.25 turns i just discovered. I guess i can go scavenging the junk yards. What should i look for? Could be difficult to find something in the US, since the car uses Sierra (raceleda) front uprights. ie, what US car has the right dimension front mounting lhd rack, w/ threads to match my sierra rod ends????

Your car should not be twitchy if it is set to hard suspension.
Bump steer will cause direction changes when the suspension lands, which is made worse by hard suspension as it will bounce more.
As to changing lanes when sneezing, if you have enough castor then the steering will feel heavier and stop this. The steering will be more sensitive than a normal car, but more castor will cause better self centering and make the car stable with more effort required to turn the wheel in the first olace.

Hmmm - interesting. After reading this thread I went out to the garage and measured my steering. The steering wheel turns less than twice from full lock to full lock! I'm not aware of it being a quick rack (I bought a rolling chassis with steering already fitted) but there is a decent enough lock, i.e. the turning circle is OK, so maybe it is a quick rack... is there any way to find out from markings?

EDIT: just been out to check again, and the cycle wings hit the headlamps on full lock... might try to move the lights to get a bit more turn.

[Edited on 21/10/06 by Humbug]

quote:

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Originally posted by Humbug
Hmmm - interesting. After reading this thread I went out to the garage and measured my steering. The steering wheel turns less than twice from full lock to full lock! I'm not aware of it being a quick rack (I bought a rolling chassis with steering already fitted) but there is a decent enough lock, i.e. the turning circle is OK, so maybe it is a quick rack... is there any way to find out from markings?

EDIT: just been out to check again, and the cycle wings hit the headlamps on full lock... might try to move the lights to get a bit more turn.

[Edited on 21/10/06 by Humbug]

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Scotmac - popular in the US are things called steering quickeners - a small gearbox you place somewhere in the steering column to change the steering ratio. Use em on hot rods and stuff - just do a google. One of these would let you keep your existing fiesta rack.

Liam

"As to changing lanes when sneezing, if you have enough castor then the steering will feel heavier and stop this. The steering will be more sensitive than a normal car, but more castor will cause better self centering and make the car stable with more effort required to turn the wheel in the first olace."

Agreed, I like lots of castor (more to compensate for my lousy driving though) and power assist. However, there is definitely a limit on castor before things get ugly. Even with castor there are definitely people who cannot deal with a quick rack while driving around.

Scotmac, as Liam said if your rack is already suited to the car with no bumpsteer issues you should consider a "steering quickener". Mostly oval track guys using them. They run about $150usd for a basic one and come in common ratios of 1.75:1 or 2:1. Others are around. Only thing is they are usually recommended for power assist cars but thats because they are used in heavy dirt/paved oval track cars. Im sure a 1500lb car with skinny tires wouldn't hurt one. Pretty sure the DOT hates them anyway though so do it after an inspection .
Cheers.

Cool. It sounds like it shouldn't be that hard to add the steering quickener later. So, i can lock myself into the fiesta thing, somewhat, and then if i don't like it, add the quickener later.

Great, i like it.

Note, i found that Rally design has a left hand drive ford rack, and it appears that the pinto and mustang II stuff are readily available in the US, tho quick versions seem to be a bit difficult.

Thanks alot guys.

Cheers, -sm

[Edited on 22/10/06 by scotmac]

Jon, understand what your saying, but when you just push it that little bit to far round a corner and the back end steps out, it makes it easier to catch if you only have to move the steering wheel a small amount. Surely the more you have to move the wheel the less chance you have of catching it.

Ok it might make people over correct, but if you get used to it, it must make those small corrections easier.

Nitram - I think when people say it makes it twitchy they mean when you move the steering wheel a little the car will dart about more than would happen with a slower rack. Whenever you drive on the road, you normally end up moving the steering wheel a little involuntarely. Nothing to do with changing geometry. Sorry if I have misunderstood you though.

Like I said personal choice, but most people that find themselves in an over steer situation and go off, go off on the outside of the corner, why ? Over correct, the tyres find grip and the opposite lock applied (too much of it) steers them off.

the few times that this has happened to me like jon describes, is because you cant take the lock off fast enough once it bits. My preference is for the quickest possible, with suitable castor to stabilise it at speed.

like in this video, from 40 seconds onwards:

http://video.google.co.uk/videoplay?docid=4844493610789993406&q=sideways+sevens

[Edited on 22/10/06 by JoelP]

quote:

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Originally posted by Ratman
0.8 turns lock to lock and 120 degrees lock to lock at the wheels. Thats a steering reduction ration of about 1:2. Am I understanding you right? The pinion would be about 4 inches in diameter. ???

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NS Dev, tks for explaining. All makes sense. Just what you need to get that opposite lock on quickly. There is a case to be made that if you are setting up steering geometry to work well on oposite lock, then you should have negative ackerman. Draw a sketch. With the tail hanging out and opposite lock on, at this point, do you want both front wheels to be tracking round the same notional center point? If they do, does this give you better grip and improve steering effectiveness?


MikeRJ made some good points a page or two back. My experience of "twitchness" was not really related to steering ratio, more to hard front suspension, and the imperfections in the road surface that traffic cause. This causes the car to jumps about a bit in a random sort of way.. but it is not really a problem once you are used to it. A few experimental quick twists of the wheel will assure you that the car is eminently controlable, and if you just relax a bit you will find the car doesn't actually bump off course by any significant amount. You will find the problem goes away completely at some speeds and is never a problem on the track where you are turning, braking and changing speed quickly, there are no invisble heavy trafic ruts in the pavement and the car aerodynamics seem to damp out minor road surface influences... or maybe it's just that your mind is on other things. Swapping to a wider front tyre can help with twitchyness. I guess this is because it gives a bit more sidewall flexibility. You might be able to experiment with this just by swapping your front wheels with the back ones.

[Edited on 26/10/06 by Ratman]