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Location:
Terrigal
Registered:
May 2002
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Shortening steering rack?
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Fri, 02 January 2004 08:01
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Hello, does anyone know if it is possible to shorten a steering rack by around 30mm? 15mm each side. If so, what company would do this?
Thanks
Joel
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Location:
Menai area of Sydney
Registered:
June 2003
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Location:
Terrigal
Registered:
May 2002
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Re: Shortening steering rack?
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Fri, 02 January 2004 10:16
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It's actually the rack I need to shorten though, not the steering arms. It's in a car it doesn't belong in, and a bit wide which is causing bump steer.
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Location:
Menai area of Sydney
Registered:
June 2003
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Re: Shortening steering rack?
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Fri, 02 January 2004 11:49
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I won't pretend to understand why it causes bumpsteer but if it's any help, under the rubber boot there is often a bit of a cavity in the housing before the steering arm reaches the mounting bush. You may be able to cut away some of the excess housing.
Is it a case of the rack having too much travel ? Can you weld a nut and bolt to the control arms somewher to limit how far the wheels can be turned ?
Anyway, I doubt if you can shorten the internals of the rack easily and because I don't understand what the actual problem is I'll shut up for a while and see if I can learn something. 
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Location:
Brisbane
Registered:
September 2003
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Re: Shortening steering rack?
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Fri, 02 January 2004 13:46
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Joel,
Shortening racks is fairly common in the clubman community (eg Lotus 7, Westfield, Caterham, PRB, Locost et al) and for exactly the same reason. How easy it is depends on the particular rack and how much you want to remove.
For as little as 30mm it could be as simple as Scorpion says - just chop off some of the threaded end of the rack and screw the track rods down further. If that going to leave you short of travel (which seems unlikely for 30mm) then you may have to shorten the housing as well. Alternatively, some racks have stops at the ends to limit travel - you may be able to adjust or remove them. Shortening the housing can be quite straightforward if it's alloy - just pick a plain, straight part of the housing, chop 30mm out and re-weld. A steel housing is the same just somewhat harder to weld (depending on your level of skill and equipment of course  )
Hope this is helpful. If you need more guidance I may be able to refer you to some of the clubman builders I know who've actually shortened racks.
Dominic
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Location:
Terrigal
Registered:
May 2002
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Re: Shortening steering rack?
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Fri, 02 January 2004 21:27
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Thanks for that Dominic, so just to clarify...
Is the section in red the track rod you refer to? Can this come off and there is a threaded section?
It is a KE70 rack. Travel isn't a real problem. As the car used to have a steering box there are stops on the control arms/steering knuckles that limit the travel. It currently hits these before the rack runs out of travel. So taking 30mm shouldn't be a problem.
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Location:
Terrigal
Registered:
May 2002
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Re: Shortening steering rack?
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Fri, 02 January 2004 21:34
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Scorpion, on my limited knowledge of bump steer....
In order to have zero, or close to it, the steering arms from the rack need to pivot at exactly the same point as the control arms do. If the rack is wider than the control arms pivot point, you have the steering arms and control arms moving in unequal arcs which can create unwanted bump steer.
Other things such as rack height and outer tie rod end height all plays a part in it also.
I've put a KE70 rack into my Celica. The Celica control arm pivot points are 590mm apart. The KE70 corolla has the control arms 620mm apart. Another idea I suppose would be to move the control arm pivot points on the Celica apart 30mm. But I think this would be a engineering headache, whereas shortening the rack shouldn't be such a headache.
Cheers
Joel
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Location:
Menai area of Sydney
Registered:
June 2003
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Re: Shortening steering rack?
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Fri, 02 January 2004 22:41
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Thanks for the info; it makes sense when you look at the overall movements of the steering/suspension. Car engineering design is pretty interesting - there are so many subtle interactions. No wonder there have been some lemons over the years. Cheers.
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Location:
Brisbane
Registered:
September 2003
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Re: Shortening steering rack?
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Sat, 03 January 2004 01:44
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| TurboRA28 wrote on Sat, 03 January 2004 07:27 |
Is the section in red the track rod you refer to? Can this come off and there is a threaded section?
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Yeah, the inner pivot on the end of the rack has flats machined in the sides so you can grip it to unscrew. It's apparent that that's the drivers side, with the teeth quite close to the end of the rack. Might well be easier to chop 30mm off the other end and have it rethreaded as it should have no teeth nearby.
If you've got plenty of travel to play with then shortening the housing obviously isn't required. To put things in perspective, the clubman builders I mentioned before are often taking as much as 100mm out of Ford Escort racks which definitely does need the housing modded
So, out with the rack, off with the track rods (actually tie rods probably is more correct terminology for a R&P), and down to your local engineering shop for a quick cut and rethread. Job done
Good luck,
Dominic
(who, as a form of personal torture, is building a mid-engined clubman style car, with silvertop 20-valve drivetrain behind the seats and Gemini front suspension)
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Location:
Montrose, VIC
Registered:
May 2002
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Re: Shortening steering rack?
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Sat, 03 January 2004 07:34
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Here's a thought - anyone ever tried a mild shortening on a POWER steering rack  Just an idea I had then if I ever want to fit power steering to me AE86 ('cause factory PS racks don't exactly grow on trees..)
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Location:
Terrigal
Registered:
May 2002
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Re: Shortening steering rack?
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Sat, 03 January 2004 07:50
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Thanks all for the info, been a good help.
I unscrewed the inner tie rods from the rack, and the threaded hole is quite deep. So should be easy enough for someone to cut 30mm off and re-thread it. When I unscrewed these, there is a plate that sits behind it that look like it is to prevent them from unscrewing by themselves. Anyhow, after taking them off it looks like maybe it can only be used once? The tabs that would have locked into the rack snap off when unscrewing it. Is that correct? Can you purchase these locking plates?
One thing I noticed is that the inner tie rods, those blocks they sit in that screw into the rack. It seems there are some different thickness ones of these. I had a old rack from a TA63 celica lying under the house and had a look at it, they are 3mm smaller than the KE70 items. I wonder if i'd be lucky enough to find some that are smaller yet again, and then it would mean taking less off the rack itself.
Mrshin, I know someone selling a complete power steering setup for AE86 if interested. I think he is asking $400.
Cheers
Joel
[Updated on: Sat, 03 January 2004 07:52]
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Location:
Sydney
Registered:
February 2003
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Re: Shortening steering rack?
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Sat, 03 January 2004 12:02
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Joel,
As Dominic said shortening the rack is not rocket science, however getting the inner tie rod ends into the correct position is close to it.
The tie rods should be parallel with the lower wishbones and the inner tie rod ball joint should be in a straight line between the upper and lower inner wishbone pivots, the game changes again when you are talking strut suspension.
I suggest that you go to a good automotive book shop and buy the relevant reference, the Race and Rally Source Book by Alan Staniforth is in plain english is a good read and not a bad starting point before you head off into the heavy stuff.
You will not be able to cut more thread on the tie rods because it is a " rolled " thread and created in a forging process.
Find a rack that is a suitable length ( or shorten ), if you then can't cut down the tie rod to a suitable length and still have thread, buy shorter ones and either make or have made suitable tie rod extenders, most machine shops will do this for only a few beer tokens.
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