Ride Heights (Again)

[malcolm]

I think the front of the Gordini is a bit high - it doesn't handle as well as the GTL, and the front tyres squeal a bit on cornering. It has GTL suspension and I want to drop it 20-30mm to make it closer to GTL height. I guessed the position when building the car.

Can anyone remember what the change in height would be from 1 spline on the front torsion bars? Logic would suggest if turning both ends by 1 spline changes the height by 3mm, and there are 20 splines, then the total would be 60mm, but that feels high.

Yet working it out roughly, one spline should adjust the angle of the lower arm by 18 degrees, and with roughly 370mm between the pivot and the wheel center that would result in 114mm movement which feels even higher.

PS - I've searched through the forum for ride height data for GTLs and popped it into a page for comparison - http://www.renault4.co.uk/tech-ride-heights.htm

If anyone can add info for their cars please post it here - we've all got 30 year old cars that are sagging a little, but it helps build a picture.

 

[angel]

You have already answered your question, Malcolm...if you rotate the bar one spline at one end only, the ride height difference is great.

You are right too about the 3mm rule, so you need to rotate each bar by 6 to 10 splines, at both ends to achieve the desired ride height. Before tensioning the bar you can check that you were right by measuring dimension "Y" (pictured on the Haynes supplement, distance between edge of anchor lever to edge of floor panel hole). When Y is lowered by 1mm, ride height drops by 3mm.

I have made an Excel worksheet similar to your ride height table that allows me to calculate rapidly all necessary measurements needed for adjusting ride height, by simply giving H1, H2, H3 and H4, plus the desired deviation from standard ride height. I can translate it to english, is there a way to make it available to all fellow R4 suspensiologists?

 

[malcolm]

Certainly there is a way - it sounds really useful. I will send an email address via PM.

 

[David M]

Torsion Bars

I have made an Excel worksheet similar to your ride height table that allows me to calculate rapidly all necessary measurements needed for adjusting ride height, by simply giving H1, H2, H3 and H4, plus the desired deviation from standard ride height. I can translate it to english, is there a way to make it available to all fellow R4 suspensiologists?


Yes please.

There are several of us who are at the point in time when our R4 is in need of a maintenance cycle. Many of these appear to be total body-off strip-downs.

I would think that your data would be warmly welcomed and it should be put in a highly visible place. eg Tech Tips.

Regards,

David

 

[jjad]

I think that our GTL is low at the rear (it has had significant work on the inner suspension mountings). Measuring (not particularly accurately) with about half a tank of fuel gives me H5-H4 measurements of 90mm on the LHS (driver's side - it's LHD) and 93mm on the RHS. Haynes says (for the earlier cars, p. 196) that this should be 127mm for a full tank. As my tank wasn't full it must be quite a bit lower than it should be.

Any thoughts? I suppose it's not just old shocks, but a tightening up of the torsion bars?

Any advice greatly received - I don't want it bumping along when we go to France!

Many thanks, Jonathan

 

[Geoff in the Gully]

I have made an Excel worksheet similar to your ride height table that allows me to calculate rapidly all necessary measurements needed for adjusting ride height, by simply giving H1, H2, H3 and H4, plus the desired deviation from standard ride height. I can translate it to english, is there a way to make it available to all fellow R4 suspensiologists?


Yes please.

There are several of us who are at the point in time when our R4 is in need of a maintenance cycle. Many of these appear to be total body-off strip-downs.

I would think that your data would be warmly welcomed and it should be put in a highly visible place. eg Tech Tips.

Regards,

David

Did this spreadsheet get posted in the end?

I don't suppose it works for the early pre-spline torsion bar suspensions?

Geoff

 

[angel]

No, it does not work for them, mostly because there was another way of measurement for pre-1969 models, that used the jacking points as a reference. You can rely on the factory workshop manual for this.
Anyway, I don't think that by using the "post-69" method on a pre-69 R4 will end up with incorrect ride heights. As such early R4s are not to be found here anymore, I never needed to make such an Excel file. But it would be unnecessary since the "old" type of measurement is more straightforward and does not have any height differences to calculate.

 

[jjad]

Can anyone confirm that a low rear end is definitely fixed by tightening the torsion bars and not just replacing the shock absorbers?

Thanks, Jonathan

 

[utilitare-extrordinaire]

I can confirm that Jonathan.

The shock absorbers (or dampers which is a better name for them) should not support the weight of the car in any way (unless they have perhaps seized or got bent-unlikely). Their sole purpose is to damp the motion of the suspension as the car goes over bumps; if you removed them entirely the ride height would be unchanged.

 

[malcolm]

True enough it's not the shocks.

Oddly it's the inner rear suspension mounting points that tend to cause the trouble on GTLs. They go all rusty and if the holes are out by just 1mm when repaired the ride height will change. Generally this happens on one side more than the other and causes all sorts of weird handling problems.

Yours are definitely out as we couldn't set the tracking perfectly so I'd guess it's that. I'd live with it if the car is sitting straight. Fix is rear suspension out and put the repair right with a jig (or if it's only slightly out redrill the holes and use a bit of weld on the edge of the hole to set the bolts in the new position). I've never managed to remove the rear toraion bars for adjustment, but that would be another way to fix it true enough.

 

[jjad]

Thanks both for confirming what I thought. I think we'll have to live with it. I just hope that when the boot is full of camping kit it doesn't 'bottom out' - are there rubber stops!?
Jonathan

 

[John Doe]

True enough it's not the shocks.

Oddly it's the inner rear suspension mounting points that tend to cause the trouble on GTLs. They go all rusty and if the holes are out by just 1mm when repaired the ride height will change. Generally this happens on one side more than the other and causes all sorts of weird handling problems.

I am very affraid of this. My car is not sitting correctly at the moment because mounting points are rusty. Major repair will be done with the new outer and inner beams, I do have rear suspension jig but I am still affraid of this.

 

[jjad]

I think that you will be OK with a jig.

I don't think that the 'experts' who rebuilt my rear suspension did it properly: the tracking was bad (rear wheel toe-in was about 20mm).

 

[angel]

. I just hope that when the boot is full of camping kit it doesn't 'bottom out' - are there rubber stops!?
Jonathan

If your R4 spec is not of the "poor road" type, it will not have any type of bump stop. If you drive on smooth roads, there will always be a hotel nearby, so no need to overload your R4 with useless camping stuff, and therefore no need to equip it with bump stops :-D .

Be careful as it's not that hard to bottom out and you may damage something.

 

[godlike]

I'we got a "normal road" type and as I remember there are rubber stops on the shock absorbers.

 

[jjad]

Thanks Angel, I'll make sure not to overload the car, but we are going camping so will need a tent and all the gear

Godlike, our 4 is Slovenian too. I've just checked and the shock absorbers/dampers do have rubber stops built in, but there are no bump stops to stop the trailing arm from hitting the chassis (but it looks like the damper would reach the end of its travel before the trailing arm could hit the chassis).

 

[angel]

The rear dampers should not have bump stops inside them, at least strong enough to support a fully loaded car. Don't rely on these, they may be damaged if they reach full travel.
Remember, the dampers are extending as the suspension compresses, so any type of rubber buffer visible on the outside of the damper rod is a top-out buffer!

 

[godlike]

Mine used to drive around 150 kg off fertilizer in back with two persons in-front.
That was when my grandfather used to live.

 

[jjad]

Thanks guys, looking at this photo I now can see that the dampers extend under suspension compression, so the bump stop on the damper is for when the suspension is under no compression!

Out of interest, where would the proper rubber bump stops be (e.g. on a rough road car)?

Thanks, Jonathan

 

[Geoff in the Gully]

Jonathon,
Some pics from an early model.

The first shows the bump stop in place. You can't see the mount bracket though.

Second pic shows where the bump stop strikes the body - blue circle

Third pic show the rear suspension parts. The mounting bracket is circled. You can see the early bump stop also.

Later pressed metal arms had the mounting bracket also though I think the bump stop was a different shape. I believe the cast arms like yours don't have the mounting bracket.

Geoff