A good eye @ tape measure, can you help?

[Steve I]

I need someone with a R1128 a good eye and a tape measure?
As you may be are aware, I’m having trouble with my Rii28 based three wheelers steering. I think it’s something to do with the poisoning of the steering rack Malcolm set me on the track of the car suffering from creating bump steer. After swotting up on this, I think he’s hit the nail on the head.
As the chassis is home made I’m having difficulty checking the ride height is set as specified or using the rule of thumb principles for adjusting the steering rack.
The upshot is that I need datum points to work from. These being the, R1128, distance from the chassis lower suspension fixing bolt to the bottom of the chassis, so I can set the ride height and the distance from the top mounting bolt to the centre of the rack on a X Y axis.
I used a couple of Malcolm’s photos, to illustrate what measurements I need.

Also a few of how the rack is mounted at present. “I’ve put them in My album as I can’t work out how to put them in this post”.
With this data I can then have some chance to workout whether the rack is in the correct place.
Many thanks in advance Steve I

 

[malcolm]

Measurements are a bit rough (couldn't find them in the manual so had a rough try on a spare chassis). It wasn't best positioned so accuracy will be only within 5mm. Ought to be close enough to see if your rack is in the right ballpark. Be aware the R4 rack has spacers behind the mounting which are approx 3mm thickness.

Measurements are taken using the R4 floor as a horizontal datum. Rack mountings are above and forward of the top front suspension mounting bolt. The actual mounting slants, but assume the yellow lines in the photo are completely horizontal or vertical and go to the center of the mounting hole as if the mounting bracket was vertical in the photo.

If you are bouncing against the bumpstops the dampers will probably make more difference than fine tuning rack positioning. Roll stiffness isn't great on the R4 and removing a rear wheel won't improve it. But if your rack is miles out bear in mind the R4 is designed to roll, and geometry is a key part in that. It ought to steer correctly even with failed dampers.

PS - How to load photos on the forum: http://www.renault4.co.uk/forum/showthread.php?t=2531

 

[Steve I]

Thanks Malcolm, have you the distance from the lower bolt to the bottom of the chassis. With this I can check the ride height, at the moment its 60mm which is too high but this chassis is only 20mm below the lower fixing. The dampers were bottoming even when going down a straight. I’ve just ordered a new set from AVO.
As soon as I get a chance I’ll check the dimensions against the ones you have supplied and let you know the results. Again many thanks

 

[malcolm]

I make it 24mm from the center of the front lower bolt to the bottom of the chassis.

 

[Steve I]

Thanks for that Malcolm, I’ve made new mountings for the rack, the rack was too close to the suspension, 48mm rather than 55mm and it was lower than it should be, 11mm should be 18.5mm. Added to this one side was lower than the other by 6mm.
I’ll let you know the results when I’ve put it back together and driven it.

I’ve been looking in to checking the bump steer on vehicles. It’s not that hard to make a gauge to check the rack/box height. As the 4’s is so critical on steering box height, it may be beneficial to 4 owners

If anyone wants to try making a gauge, it’s not that hard. I’m not sure about posting web links on this forum but if you search for “make a bump steer gauge”.
A good explanation of bump steer can be found by doing a search on, “Bump Steer Technical Information, bakerprecision”. It’s an American site but the explanation is very clear

 

[angel]

Nice links Steve...especially to people like you who are forced to "re-discover" the correct R4 geometry.

Renault had two ways of putting the steering rack on the correct position. That being described in the early manuals measured the steering rack position in relationship to the upper wishbone ball joints. Later, they made their own bump steer gauge, which operates exactly on the same principle as Longacre's gauge.

Unfortunately they don't give any tool information or dimensions and today they must be "introuvable".

Another problem could be that, in order to operate the front suspension to its full travel we need to remove the torsion bars, not too easy a task...or else use a fixture to compress the suspension similar to Renault's tool (two threaded rods hooked on the lower wishbone pins driving upwards a bar placed on the underside of the lower wishbones).

In any case it it far easier for me, to drive the car to a wheel alignment specialist that knows his job...

 

[Steve I]

update I’ve lost the wobbles.

It’s all down to this forum I would have struggled without it.
Thanks to Malcolm’s input I identified that the rack had been installed about 10mm to close and 8mm to low to the top wishbone. I constructed new mountings and it drives remarkable better I’m yet to put the new AVO’s on, which should improve the handling still further.
Could it be possible that the wrong shocks are fitted? There is only about 15mm travel on the ones that are fitted, see photo, is that about right?
The car go’s around corner like its on rails but straight it’s still not as positive as I would like. I think I may increase the castor slightly. any sugestions?

 

[malcolm]

Nowhere near enough damper travel there. Must be 50mm available before the bumpstops on standard cars, and your private messages suggested you are already sitting a bit high . So probably the dampers are incorrect. Should be interesting to compare the AVO dampers.

Cars are a pain when you don't know what's been done to them.

(edit: misread the PM - probably sitting too low.)

 

[angel]

The shocks seem correct to me, in fact there is nothing else that will fit R4 R5 and R6. If your car uses the R4 wishbone uprights, then it may be sitting too low, if not, the top shock absorber mounting is incorrectly fabricated.
Increasing the castor is fairly easy as the tie rods are adjustable. Worth trying it as this suspension operates on lots of castor (13 degrees nominal).

 

[Steve I]

Latest up date,

Well what a difference a set of shocks make. The AVOs are just fantastic not even had to adjust them. I still may increases the castor though, as it has been referred to in a article about the DRK. I ended up setting the cassis height at 155mm the front still looks low but that’s due to the chassis crossmember being a piece of 50x50 box section.. The wishbones ar now sitting level.
The next thing is the clutch is slipping, I never dared to go fast enough to find out before, so do I lookout for a 5 speed box? And can I update the brakes to disc’s R1128.

 

[malcolm]

Just a thought about the castor - the pre-'69 Renault 4s had 7 degree castor which isn't enough. Later ones increased to 13 degrees. Worth checking the article referred to the later ones.

Handbrake is the only real difficulty in a disc brake upgrade - the hand brake is on the rear wheels. You'd need uprights, discs, callipers, rear brakes, handbrake mechanism. and ideally master cylinder. Might be able to help with the bits.

 

[Steve I]

The handbrake is already on the rear wheel, although thinking about it I’ll keep the drums as it looks a little moor 30s I fancy putting the handbrake on the outside, I found this photo the other day some nice touches.

I think this is what I.m heading for. We’ll see what the winter brings.
Any thoughts abot a 5 speed box?
and is ther any improvment to the drum brakes? like are ther bigger ones on the van?

 

[pepper]

I actually think the drum brakes on BB are quite good, they are certainly far better than the Morris Minors and Oxfords brakes which we also own!