Steering rack selection

[L_O_O_M]

Hi all

I was wondering if anyone can please tell me how different steering systems work in the sens of how do I match the pump with the rack,how can I see if a different rack will work on the car with regards to length...etc, pulley size on the pump,what pump,if the pumps pulley is to small (due to the right size for the pump to run right at ideal) but smaller then the original pumps pulley what do I do if the belt slack is to much for the belt tensioner,the reason I ask is I would like to do an engine conversion on a car that use recirculating ball steering but I think I am going to convert to rack and pinion so I would like to know how to select the right rack,pump,,,etc



The car is a mercedes benz w108(I know this is not the best forum to post on but some of you guy's have allot of knowledge about these sort of thing.)

[astroracer]

Swapping to a rack involves a whole lot more thought than most people realize. That's why this question gets asked so often. Swapping a rack (pick a rack, any rack) into a suspension that was not initially designed with that intent usually creates a suspension with unusual amounts of bumpsteer and drastically reduced (or increased) turn radii. The racks inner tierod pivot point locations are tied directly into the upper and lower control arm pivot points. If the inner tierod points aren't in the right location (both cross-car, longitudinally AND vertically) this will cause all kinds of issues with bumpsteer, road feel, turn-in and turn-out.
Read this Longacre article. Best explanation I have found of why NOT to try to adapt a rack where it doesn't belong....
http://www.longacreracing.com/articles/art.asp?ARTID=13
Like it says in the article, to do this right you need to start with a clean sheet of paper and design the suspension (read that suspension AND frame) AROUND the rack.

[L_O_O_M]

Thanks for replying astroracer,thanks for the info I have been reading up on bump steer it's very interesting it helps.Ok now the other thing,how do I select the right rack and pinion(like what should I measure,....etc)?And how do I match the rack with the pump?

[another69]

The rack manufacturer will recommend or supply a pump with the proper flow rate for the rack. Get a rack that has been designed to retrofit into your car (not sure about your Benz) and bump steer can be minimized to almost nothing. I put a rack into my 1st gen and will NEVER EVER go back to a steering box and linkage.

[L_O_O_M]

The rack manufacturer will recommend or supply a pump with the proper flow rate for the rack. Get a rack that has been designed to retrofit into your car (not sure about your Benz) and bump steer can be minimized to almost nothing. I put a rack into my 1st gen and will NEVER EVER go back to a steering box and linkage.

I thought you looked at steering pump pressure rating as well?

[Oside68]

Hey another69, I'm looking to update my 68, which mfg. did you go with?

[another69]

Sorry it took so long to reply- I went with Unisteer. Very happy with the power rack