Steering rack height

[Andy McGhee]

Hi all

What are the effects on toe-in/out, camber and tyre wear if the steering rack setting is a) too high and b) too low?

 

[malcolm]

A small change would have no effect to camber at all (assuming you are going to be using a standard rack and mountings). For toe and tyre wear you'd just need to adjust the tracking after refitting the rack.

Main changes would be in bump steer and sensitivity to road wheel imbalance. What are you planning?

 

[Andy McGhee]

I'm still trying to get to the bottom of the negative camber problem I mentioned in a previous thread. I've tried everything I can think of; the van went straight through the MOT without any problems, although the tester said there was slight play in one of the tie-rod bushes. As you can see from the attached photo, both of them were in a pretty bad way(!) The newer one - from eBay - has only lasted a year before breaking up. I imagine the other one is the original; the bolt had been bodged, albeit very effectively, to compensate for the wear in the bush, but the hole in the offside tie-rod has become enlarged - I'm looking for a good replacement.
Anyway, back to the thread! I thought I might have got the rack setting wrong when I last replaced it, but I've had a good look today, and it appears to be fine. The weird thing is that the van sometimes seems to sit correctly, with that slight positive camber look, and sometimes seems too low - not drastically, but definitely with too much negative camber. The front tyres are wearing on the inside edge.
I think the problem must be what I've suspected all along -a ride height issue. Sadly, it's an 83 F6, so no cams to help! I'm afraid that when it comes to torsion bars, I'm completely lost. How much do you think it would cost to have the front ride height adjusted?

 

[malcolm]

Those are the nastiest tie rod bushes I've seen. They would certainly cause bad tracking, tyre wear and weird suspension angles. Der Franzose have replacements for about 5 euro each, supposedly made in Europe (and silver rather in cadmium so possibly different from your replacement).

You'd need to set the tracking every time you change a bush or a balljoint. Especially if it was last set with worn joints. I'd be very surprised if the problem isn't excessive toe out.

Though for ride height it can mess up a car if you have the wrong ride height, either because it's too low or because you adjust it too high. Do you have any numbers for the ride height? Angel posted a method of measuring it here: http://www.renault4.co.uk/forum/showthread.php?t=1335&page=2

 

[Andy McGhee]

Yes, I've got various manuals with the numbers for ride height calculation. On a less technical level, I can tell that the front end is very slightly lower than it was because the bowl I use for oil changes now snags on the anti-roll bar!
I've changed all the parts I thought might be responsible - I had to change the wheel bearings, so I replaced all the balljoints, the track rod ends and the nasty bushes in the photo. The only part I still need to change is the offside tie-rod; the hole at the bush end is slightly too big, so I think there could be a tiny bit of play there. Will see how things go, and then have the tracking checked.

 

[angel]

Assuming you don't have a broken or bent suspension component, the only factor affecting camber angle on the R4 is ride height. Steering rack height has nothing to do (but has to do with proper R4 hanling as Malcolm said).
You must measure it accurately as per the manual, no guesswork here like "how many fingers gap between tyre and wing edge" :-)
The ride height can still be adjusted on your R4 even with the latest torsion bar mountings, however it is time consuming compared to the earlier cams.
What puzzled me is why your tie rod bushes are so badly worn, and even worse, why the new one lasted only so little. It seems that they are unduly stressed (bent wishbone? incorrectly adjusted tie rod? worn out lower wishbone bush?). When you loosen both bolts that hold the tie-rod, can they be removed and refitted easily, or do they need levering and hammering?

 

[malcolm]

Assuming you don't have a broken or bent suspension component, the only factor affecting camber angle on the R4 is ride height.

Don't forget steering angle

In the Renault 4 the wishbones are closer to equal length and parallel than on many other cars. I'd be surprised if a small change in ride height by itself could account for unevenly worn tyres.

Instead much of the camber required to compensate for body roll in cornering results from the high castor angle. Turn the wheel as far as it goes and it won't look very upright.

Also just off the straight ahead there can be movement in the bushes as the wheels pull outwards on moving forward. A check for that would be if the camber is the same after pushing the car a few feet forwards on a flat surface as it after it's been pushed backwards a few feet. It's possible to measure camber accurately enough for this using a plumb line between the top and bottom of the wheel rim (split pin and cotton are OK).

Without measuring the car it's just debate, but it would be interesting to see measurements for the front tracking and the ride height.

 

[angel]

Malcolm, by saying "camber" it is self-explanatory that we mean static camber with the front wheels pointing straight ahead.
What you describe is a factor of castor angle (just take a look at a 2CV, with its 15 degrees castor angle, at full lock) and steering axis inclination.
Also the wishbones are not so parallel as they seem. The whole concept on this excellently designed suspension is to give negative camber when compressing (e.g. when cornering hard). That's why initial height setting is rather critical.
I'm with you about the measurements...do you have them Andy?

 

[Andy McGhee]

Well, I measured the H1 (ground to wheel centre) - H2 (ground to bottom of chassis longeron [in line with wheel centre]) distance. The fuel tank was full, and I checked the tyre pressures. According to the manuals, for an F6 -R2370- the difference should be 51mm, +/- 10mm.
The measurements are: Nearside: H1 260mm - H2 142mm = 118mm; offside: 264mm-152mm = 112mm.
I was a bit surprised by this, so I did the same measurement (offside only) on my GTL, whose suspension is fine. Here the difference is supposed to be 41mm, +/- 10mm. The figures were: 250mm-145mm = 105mm!

As far as the tie-rods/suspension bushes are concerned, yes, I had to do a little levering to get the bush bolts out, but nothing too drastic. Has anyone else had problems with the cheap bushes breaking up?

What are your thoughts on the H1-H2 results?

 

[angel]

Both cars seem to be too low at the front.
What do you mean that the GTL's suspension is "fine"? That's 65mm lower, it must be visible even when looking from the outside! No wonder then that you have so much negative camber. The solution would be to adjust the ride height correctly.

About the tie-rod bushes. I have always been buying cadmium-plated ones, not silver. Definitely not genuine Renault, but never had any problems with premature wear. The only problem I can recall was about 6 months ago, when I got a pair that looked of different design...thicker sheet metal, slightly different shape, and soething like plastic bush (not rubber). They didn't fit in the chassis and I returned them back.
A little leverage on the holes, as you describe, is normal.

 

[malcolm]

I've just measured my GTL (offside only). H1 250mm, H2 154mm Difference = 96mm. So mine is nearly 10mm higher than yours. I did push mine backwards and then forwards again as it has been stopped with it's brakes on a damp patch, and moving the car seemed to increase the height a little. Drives and handles perfectly well with even tyre wear.

I don't have a 850cc car to measure, but these would probably be closer to the book figures. At least they look higher at the front than the GTL but not as high as the early L.

As far as I understand the suspension wasn't changed when they dropped the heavy 1108cc engine in there, so the GTL sat a couple of inches lower at the front. That's one of the reasons they look odd with retro chrome trim. I did an engine swap on an 850cc once and ended up with GTL ride height. Can't find any book figures for what it should be though.

 

[angel]

Very interesting...neither do I have measurements for the GTL except for a general wheel alignment data book (from ETAI) which does not give any different numbers for TL and GTL. Paul? Any info on this?

Incidentally I haven't measured a GTL yet (not even my Jogging!) to see what is happening. Malcolm, your GTL is Ermintrude? Just want to see if it seems low in the photos.

Something that comes to my mind is an almost forgotten instruction I read in the RTA, it says that ride height up front for R4s with "tripod" inner driveshaft joints should be 5mm lower (difference 5mm greater). This is practically valid for all our R4s (I doubt anyone still has 4-ball inner joints)

 

[malcolm]

It was Ermintrude I measured. My guess is they stuffed the 1108cc engine into the first prototypes and decided they liked the handling, or maybe they liked the more aggressive looks. Can't have been the ride as that's much nicer in the 850cc cars.

Factory manuals for the later R4s seem rare. I guess that's because there were other people like Haynes printing cheaper manuals by that time. Pity as the information is a lot better in the factory manuals.

 

[angel]

Ermintrude seems low to my eyes both on front and rear (but not excessively).
You must be right about GTLs being set lower than 850s as at the factory they adjusted the ride height by measuring torsion bar preload (and I doubt they measured each vehicle's height at the tend of the production line...).
I couldn't find a reference to the later models even on the Dialogys CD.