Changing C4 rear suspension roll steer

69427

69427

The Artist formerly known as Turbo84
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I'm kicking around reducing the rear roll steer/toe-in during cornering, and am looking at making different toe links. I like the stock setup with the "old fashioned" tie-rod ends at the knuckles, but the present ones are metric. The tubes I'm looking at in catalogs are SAE thread. So, I was thinking about using older type tie rod ends (like on the original C3 front suspension) that are (I assume) SAE thread. I don't have a clue what size and thread they are (until I unbury the old frame) so if anybody knows and can save me some time I'd appreciate it (hopefully Chevrolet has retained the same taper too). I'm probably stuck using heim joints for the inner pivots (unless I can think of a clean way to anchor tie-rod ends at the inner pivot points too).

Cliff note: Anybody know the thread size and pitch of the tie rod ends on the front of a C3?
 
BBShark said:
I don't have one in front of me but I always thought thet were 1/2-20.
Click to expand...

Well, that would be handy as the sleeve/tubes I'm looking at appear to be 1/2"-20. The stock parts are (IIRC) 14mm, so the "downsizing" to half inch doesn't appear to be too dramatic.

Now I just need to figure out what configuration I'm going with on the inner pivots.
 
BBShark said:
Another (sorta) guess. I think the taper is different.
Click to expand...

I think I'll haul a spare rear knuckle with me to one of the parts stores and try out a couple (old style SAE) tie-rod ends to see what I find. As long as the taper is identical then life is easy. If the taper is different then perhaps I'll just have to use a stock toe link and cut and rethread the inner pivot section. I shortened and rethreaded the outer section for the present build, but I'll have to see if I can get a similar size tap in LH thread.

Visually the present toe link looks excessively long, but doing the geometry calculations indicates it adds only minimal toe-in with 2 inches of movement during roll. However, the SOTP feel is that the car tries to crab into corners. The old C3 suspension always gave me the feeling that the rear would try to pass the front on the outside of the corner, while this (C4) configuration feels like the rear wants to pass the front on the inside of the corner. :wink:
 
Just curious, is the toe-rod assembly common for the whole C4 production run? I can't think of any reason why they would be different or wouldn't interchange.

I was just kicking around reworking a used spare assembly if I could find one cheap.

Edit: I just thought about the individual tie-rod links on C5 and C6 cars. Depending on their length that might be an option.
 
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Tie-rod end search

I hauled a spare C4 rear knuckle to a nearby chain parts store to look at some ends. Apparently (and I can understand) tie-rod ends are not that high of a demand item (ie: they didn't have any in stock). I asked the guy to check several different Chevy platforms, and most are different part numbers. (To his credit, they do supply Moog parts, so at least I'm familiar with the brand.) He's going to order a couple C3 front tie-rod ends for me to try on Monday (and he can send them back to the warehouse if I don't want them). I'll confess some puzzlement why Chevrolet/GM uses so many different part numbers for these things. I can't believe that an Impala and a Corvette, for instance, can't share the same part. A part strong enough for a big Impala should work okay for a lighter Corvette with big tires (I would think).
So, anybody have any insight why Chevrolet/GM did this (other than the right hand didn't know what the left hand was doing)?
 
Well, struck out with the first attempt to find some ends that fit. The original frame is half buried under junk, but I measured some spare C3 steering links I had in a parts box, and the requirements are pretty different. The C3 steering link is 3/4" thick, while the C4 toe link is 1 1/16" thick. Obviously the C3 ends won't fit the C4 knuckle. (I checked the ones at the parts store to make certain, and yep, too short.) So, I guess I'll just have to hit some junk yards with a caliper to measure some steering and suspension links to see if anything looks promising.
 
Well, not making much progress on this issue. I found some specs on the toe-rod ends (PN ES2247 if I read the listing correctly), but haven't been able to find any comparable SAE parts. I could use the stock metric ends, but then I need to use metric threaded tubing, which sounds like a headache to find. Or, buy a perfectly good stock C4 toe assembly and cut and tap the tubing. But, that route seems more expensive (I believe I would have to also buy a left hand metric tap, and L&R metric Heims) than using all SAE stuff, which I can't find anyway, so it's academic.

I'm still trying to decide the magnitude of the headache factor if I used an SAE thread tube and drilled and tapped one end for the 14mm thread of the tie/toe-rod end. As I mentioned in an earlier post I'd have to start with a 1/2" threaded tube to be able to drill and tap it to 14mm. I'm still trying to get a feel for the necessary sizing of the components.

So, the search continues.
 
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