Steering racks

[chris.richard]

I've twiddled my rack, and it's 2.75 turns, I read the works cars used 2 turns; what is everybody else using?

[SUSIT]

Hi Chris
There has been threads about this before. One school of thought is that a high ratio rack makes the car more twichy and tireing to drive. The rack in my car is also around 2.75 - 1

Stephen Struthers

[guy mayers]

And harder to turn! My car is about 2.5 turns lock to lock with loads of castor I've at least got some feedback through the wheel plus some self centering. But with 225s on the front it's heavy at low speeds. The Alfa 145 is 2 turns lock to lock which is great but that's what you get when you can have power steeing. So, has anyone thought about going down that route yet?

[rutthenut]

Originally posted by guy mayers
The Alfa 145 is 2 turns lock to lock which is great...

But the number of turns isn't the whole story.
The Alfa 156 GTA has a pretty low figure quoted, but has an appalling turning circle!

Not that the Strat should have that problem with it's short wheelbase and lack of driveshaft issues or tyre problems in the front arch. (nor it's rear wheel drive setup allowing donut-type turns on demand!)

[CorseChris]

The rack in my Corse S is about 1.75:1 assuming I counted it correctly. This sounds a weensy bit too 'quick' to me, but as John rightly says, it isn't turns, it's what those turns translate to in terms of wheel deflection that matters and that depends on other factors of course...

...no doubt I'll find out one day if this is OK or not. At least it's quick, easy and remarkably cheap to change the ratio on a Titan rack.......

Andy G has commented that his Corse S has a poor turning circle but I doubt our racks are the same.

[Stratos]

Originally posted by CorseChris
The rack in my Corse S is about 1.75:1

Andy G has commented that his Corse S has a poor turning circle but I doubt our racks are the same.

Chris,

I think you will find they are the same. I seem to remember Gary Lomas commenting to me one time that his rack was 1.75:1, and this is the car that Andy G has now,

The turning circle on my Allora is also poor, but my ratio is 2.75:1

[CorseChris]

David,

That's interesting... I spotted that Andy's car (when it was Gary's if you see what I mean...) has a Litton rack (made by Titan). For some reason, I sort of assumed that the rack specifications had changed a bit since then and that mine would be different. Still, I think I can change the ratio to 2.18:1 by swapping the pinion from a 10 tooth to an 8 tooth should I need to.

All these ratios are confusing and somewhat meaningless without a direct comparison of some sort though - Titan specify inches of rack movement per turn of pinion which makes it a bit simpler I think.

[chris.richard]

It also hinges (!) on the distance from pivot to steering arm - the longer that distance, the more travel required to achieve the same wheel deflection. This may well vary from Hawk / Transformer to Litton / Allora / Corse

[CorseChris]

Indeed.

Only figure that's really going to do it would be degrees of wheel deflection per turn of steering wheel.

This figure could then be related to size of arm muscles and reaction times of the driver.....

[rutthenut]

Originally posted by CorseChris
Only figure that's really going to do it would be degrees of wheel deflection per turn of steering wheel.

And then you have to factor in the wheelbase, unless comparing fitment to the same car (i.e. the Strat).

Arm muscles too, also depending upon the diameter of the steering wheel. I've known of people having accidents, or near-accidents, through using an exceptionally small steering wheel on cars in the past. Maybe it's the brain cells and reaction times at fault then though, not just geometry.

[Stratos]

Originally posted by rutthenut
Maybe it's the brain cells and reaction times at fault then though, not just geometry.

Don't think I should count up the number of incidents my car has had - if I did, it might indicate my brain cell count was well into negative territory.:rolleyes: :rolleyes:

[CorseChris]

Originally posted by Stratos


Don't think I should count up the number of incidents my car has had - ........


But you are still smiling and still having heaps of fun......


...so who's counting!!

[David May]

My Corse S with a Titon 'Gp4-type' ratio rack has just under 2 turns lock to lock, but with a lousy turning circle. I've modified the steering arms to get alternative mounting points (about 30% shorter) which now gets me really "full-opposite-lock" with the widest tyres just touching the bodywork. It's a bit heavy going at parking speeds, but I can now catch it (sometimes) before it spins! The sensitive steering is a matter of taste - I recon you have to work the steering in any Stratos, they all seem to want to go where you don't want them to!

Dave May

[guy mayers]

Originally posted by David May
Stratos, they all seem to want to go where you don't want them to!

Dave May

Progress at last! After 18 months away from home, where I didn't want it to go, the Stratos will be returning to live above the Spider! The lift is finally working and all I have to do is rehang the garage door!!
Happy Guy!

[CorseChris]

Originally posted by David May
..I've modified the steering arms to get alternative mounting points (about 30% shorter)


Dave, I thought you had an I for some reason.... you wouldn't happen to have some drawings for those S steering arms would you??? Sounds like I might be wanting to modify my car at this rate.

Last thing you want in a car with such poor rear vision is having to do lots of 8 point turns......

...still, there's always the loud pedal to tighten up the turning circle I suppose....:eek:

[Stratos]

Originally posted by CorseChris



Dave, I thought you had an I for some reason.... you wouldn't happen to have some drawings for those S steering arms would you??? Sounds like I might be wanting to modify my car at this rate.


What effect do these modifications have on Ackermann angle, bump steer, etc?

[David May]

Opps, sorry about that typo.. Mine is an 'I' so the arms are fabricated steel bits that bolt onto the uprights and are easily re-fabricated!

Dave May

[CorseChris]

Originally posted by Stratos


What effect do these modifications have on Ackermann angle, bump steer, etc?

Ackermann should be easy enough to get right with a bit of care, not sure bump would be affected as long as the track rod end ball-centre height was maintained as before...??

No reason why the S arms couldn't be made in a similar way to the I (and Hawk) arms I suppose. Different geometry no doubt though.

'praps I'll just try and finish the damn thing first........

[David May]

Ackermann was around in the days of horse and carts and although his principles are sound, there appear to be few cars on the road today that apply them to the letter. The flexibility and slip angles of tyres allows a lot of error and once the speed gets up, the inside wheel is significantly unloaded. There are far more misalignents caused by changing ride heights.
It may well be that my tyres are fighting each other towards full lock, but there are no obvious signs (noise, scrubbing..) and no detremental effects on the stability. The improved turning circle is much appreciated when parking.

I modified mine by welding on another lug so that I can swap the steering arms from one location to another should I even want to return to soggy steering!

Dave May