[crownver]

Hey guys,

My son is building a 73 Celica with a 350SBC, Borg Warner 4 speed, and a Ford 9" in it. He needs to convert to a rack and pinion, mainly because of header clearance issues. He has it mocked up now and it seems to be working, after changing the height of the rack a couple of times. I've read a lot of the info on it and I just don't understand the stuff about ackerman and bumpsteer. Can anybody tell me a simple way to make sure the setup will work when he get's it on the road? Or is there no such thing as simple? Any tips would be appreciated.

[joe_padavano]

Originally Posted by crownver

Hey guys,

My son is building a 73 Celica with a 350SBC, Borg Warner 4 speed, and a Ford 9" in it. He needs to convert to a rack and pinion, mainly because of header clearance issues. He has it mocked up now and it seems to be working, after changing the height of the rack a couple of times. I've read a lot of the info on it and I just don't understand the stuff about ackerman and bumpsteer. Can anybody tell me a simple way to make sure the setup will work when he get's it on the road? Or is there no such thing as simple? Any tips would be appreciated.

The simple way is that you need to find a rack that has the inner tie rod pivots in the same place as the inner ends of the tie rods with the original steering linkage. Any other configuration will result in bump steer, which means that when you go over a bump (or otherwise move the suspension), the tires will steer in an unintended direction. Bring a change of underwear while driving if you don't get this right.

[crownver]

Thanks Joe,

I don't think he gave any thought to this at all, and he's the type of kid (aren't they all) that figures if it looks right it is right. I'll go over this weekend and check it out. I'm pretty sure he'll have chucked the old steering by now, so not sure what to look for.

[joe_padavano]

Originally Posted by crownver

Thanks Joe,

I don't think he gave any thought to this at all, and he's the type of kid (aren't they all) that figures if it looks right it is right.

Yeah, I've got one of those too...

Unfortunately, there are a million wrong ways to do this and only one right way.

[Triaged]

Pull the spring out and put the suspension back together. Put the car up on jack stands, a tire on, a jack under the lower control arm, and a piece of ply-wood leaning against the tire. If when you raise or lower the tire it creates a gap (front or back) between the sidewall of the tire and the ply-wood (don't let the bottom move) you have bump steer. I wouldn't worry too much about the Ackerman as that is mostly built into the steering knuckle. Just make sure when looking from above that the rack and pinion is mostly in line with the tie-rods.

[crownver]

Thanks Triaged, I'll get him to try that. Is there any acceptable level of bump steer?

[Triaged]

One answer would be "less than it had before". It seems that it is too late for that one to work however. Another choice could be less than the toe spec (if the spec is 1/16" toe-in per tire than I think less than 1/16" would be a good bet). The last choice could be "as little as you can get" because with a swap like this that might be all you could hope for.

Here is another thread on the topic.
Bumpsteer limits