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Steering Rack - Why rigid mounted not isolation bush
Posted: Thu Feb 29, 2024 21:02
by MetBlue
For reasons I'll go into elsewhere, I've had my rack rebuilt, but the main casing was beyond help, so it was rebuilt with a different second hand casing the company had kicking around.
On collection I note it has isolation bushes pressed into the mounting points. For some reason, Lotus used two top hat bushes at each end to fix the rack without isolation to the chassis.
Not best photo but on left you can just about make out the isolation bushing.
The owner of the company, an ex Burman guy was most surprised saying he could think of no other vehicle with a rigidly mounted rack.
Presumably Lotus did this intentionally.
Thoughts anyone on what they could have been trying to achieve?
Anyone else done any rack work and fitted using isolation bushes?
Should I be getting those bushes out and using the rigid Lotus intent ?
Tony
Re: Steering Rack - Why rigid mounted not isolation bush
Posted: Thu Feb 29, 2024 22:17
by Marten
MetBlue wrote: ↑Thu Feb 29, 2024 21:02
For reasons I'll go into elsewhere, I've had my rack rebuilt, but the main casing was beyond help, so it was rebuilt with a different second hand casing the company had kicking around.
On collection I note it has isolation bushes pressed into the mounting points. For some reason, Lotus used two top hat bushes at each end to fix the rack without isolation to the chassis.
Not best photo but on left you can just about make out the isolation bushing.
The owner of the company, an ex Burman guy was most surprised saying he could think of no other vehicle with a rigidly mounted rack.
Presumably Lotus did this intentionally.
Thoughts anyone on what they could have been trying to achieve?
Anyone else done any rack work and fitted using isolation bushes?
Should I be getting those bushes out and using the rigid Lotus intent ?
Tony
Mounting the rack solid removes flex and gives more steering precision, which is what a Lotus is supposed to be about.
Re: Steering Rack - Why rigid mounted not isolation bush
Posted: Thu Feb 29, 2024 22:23
by Alan_M
As Marten says - more precise control. What our cars are renowned for, so I’d certainly want to keep the original setup.
Having a rubber bush will allow small movements of the rack losing some of the precision and feedback between road and hands. Similar concept to using rose joints rather than rubber bushes for suspension for race cars.
The Elise etc also use rigidly mounted racks
Re: Steering Rack - Why rigid mounted not isolation bush
Posted: Sat Mar 02, 2024 13:20
by MetBlue
Had decided the rubber bushes were heading for the bin, but became a no brainer anyway. Bolt for the bush was M10. Chassis hole and bolt is M12.
Didn't take a lot to remove. Only the inner sleeve was steel, so pulled out easily with a long bolt and a socket to draw into.
Re: Steering Rack - Why rigid mounted not isolation bush
Posted: Sat Mar 02, 2024 15:52
by Pete Boole
So do you know what the original application for the steering rack was with the bushes in place?
Pete
Re: Steering Rack - Why rigid mounted not isolation bush
Posted: Sat Mar 02, 2024 17:41
by MetBlue
The casing is badged FORD logo.
Sierra Cosworth definitely. May be also the wider Sierra range.