Ride Height & Rear Camber

[DavidBrough]

Hi guys,  I have a 1969 280SL Auto and have though for some time that my car was riding low at the rear so I spent a while reading all the various posts on ride height which were very informative and I am now going to fit some new rear springs and rubber mounts. I thought the first task was to measure everything and see what is fitted before ordering any new parts especially as it didn’t seem too difficult a job. However, I am now a little confused as the parts I have don’t seem to match the details in the copy BBB I have and I would appreciate some guidance on the best thing to do and whether science or trial and error work best.

I have approx 1 deg negative camber which I understand should be 1.5 positive so need to move things some 2.5 deg. From previous posts it seems that 6mm in spring height equates to 0.5 deg of camber so I need an extra 30mm of spring height which seems a lot. Does that sound correct?

I removed the LHR spring which was numbered 113 324 04 04 had three red stripes on a lower coil and four yellow stripes on a middle coil, the lower support plate was set on the middle notch and the top rubber was part 110 325 03 85 (14mm when new according to my copy BBB) which measured 13mm at right angles to the lowest point although spring pressure had worn into this at least a further 4mm. I measured the free length of the spring at 286mm which was much harder than I thought it would be. I took the measure between the two coil ends being the longest points and measured by laying the spring on a large piece of card, marking the end points carefully with a pencil.

The copy BBB I have has spring details at 32-0/5 to 32-0/8 and makes no mention of yellow stripes so I assume the red ones are correct. The part numbers quoted for normal and hard springs are the same but I think I have standard springs from the height measurement. 289.5mm new with mine now at 286mm. I do have an old caliper which gave the wire thickness at approx 16mm so could be either.

As far as I can see from the BBB tables, standard springs with three red stripes should have a 20mm top pad, part 110 325 02 85, with the bottom mount on notch 3. However, mine appears to have a 14mm top pad, part 110 325 03 85 (only used with blue springs and definitely no blue paint on mine) and the bottom mount on the middle notch.

Am I right in assuming that the coloured stripes were put on by the factory as each car was built to indicate the settings used and parts fitted to that individual vehicle?

I appreciate that my car may have had the settings altered after manufacture but presumably this would only have been to obtain the correct settings. However, from the history I have and as most things I have come across have been standard, my feeling is it hasn’t been touched from new.

I also understand that the diff mount rubber in the boot/trunk affects camber and will renew this at the same time, is this just another complication?

Anyway, I am going to buy new standard springs but should I replace the top rubbers with the same size as fitted i.e. 14mm or 20mm as the BBB indicates or 30mm as my measuring indicates (actually 35mm but I think 30mm are the biggest) or pick any size and see what happens!

Any thoughts or guidance would be gratefully received.

[A Dalton]

Both the top [ trunk] and bottom [ pivot pin] hanger mounts should be checked first, as they both effect ride height/camber.
 Both can easily be eye-balled. The top should have  at least 1/4' spacing between the washer and the base of the mount and the lower should be centered with the pivot pin bolt head. Wear/collapse on either results in neg camber.
 Also look at the end rubbers on the compensating spring. These came in different original sizings , but it is recommended to use the largest [ 6mm ] on replacement. [ most parts houses only sell that size ].  Any  comp. spring  changes effect camber equally on both sides , wereas spring/mount changes that side only, so spring pad sizes can be  selected individually as required. Any final tweaking can be done by rotating the bottom spring mounting plate. It has a rotational height adjustment, but here again , most 113's just use the highest setting...

[DavidBrough]

Thanks, I think my top diff mount is U/S as there is only 1 to 2mm of gap between the plates and it's ripped on one side when the axel is raised. The lower mounting seems OK, thankfully, as this looks difficult to replace.

I think I will go ahead and replace the springs as well as they are 3 to 4mm short and replace the mounting rubbers with the same size as currently installed.

[rwmastel]

quote:Originally posted by DavidBrough

Hi guys,  I have a 1969 280SL Auto and have though for some time that my car was riding low at the rear...

Are you sure it's not just riding too high in the front?

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[DavidBrough]

Hi Rod, I don't think so, but then I'm not really that sure either. The front sort of looks OK and with the rear camber being 1 deg negative I sort of assumed it was at the back. I think the bad diff mount needs fixing first then I will measure things all round again.

[George Davis]

David,

going from -1 to +1.5 degree camber takes a fairly large increase in rear ride height, I had to do the same with my car.  I'd suggest using the thickest rubber spacers for a start.  My car had the thickest spacers, and installing new springs didn't get it anywhere near +1.5 degrees.  I ended up installing longer custom-made springs.  This was with a new diff mount, too.

Also, the new MB springs were noticably stiffer than the old springs, so be prepared for that.

George Davis
'69 280 SL Euro manual

[DavidBrough]

Thanks George. Although Arthur’s original comments have set me thinking and reading more posts, always dangerous. I think I must deal with the diff hanger mounts first. My top one is shot and whilst the bottom one seems OK, from what people say, my leaking pinion oil seal may well indicate otherwise. As a result, I do have a few more questions and perhaps someone who has completed these tasks could enlighten me.

1. For pinion seal replacement, my Haynes manual makes no mention of having to remove the diff front plate but comments made make me think that it is very difficult to pry out if you don’t. In other words, am I likely to damage or break something with my big crow bar and screwdrivers if I don’t!

2. Is it better to remove the front plate to replace the seal or does this just lead to further problems?

3. If I have to remove the front plate, I am then inclined to just carry on and replace the bottom rubber bushing in the diff hanger as I am sure mine is the original and whilst it looks sort of OK there has been some comment about them not really lasting all that long and I may as well get one of the new one piece items from SLS people have mentioned or, is this best left well alone if it looks OK?

4. From the posts I’ve read, it is possible to do this with the axel in place and I’m not too phased by having to make a right angle jig to put the hanger arm back and I do have to replace the top mount anyway (although this seems an easy job in isolation). Is it possible to drop the diff enough to actually remove the hanger arm and also properly measure its distance from the flange joint with everything else still connected?

5. Can the centre compensating spring stay in place during all this or does it have to come off?

6. I think I understand all the stuff about replacing the slotted pinion nut slowly to the same relative position to preserve the crush ring and confirm the diff turning torque. Should this be 26/30 mkp? I assume I pray that that is what it is when I check before removal or does it not matter what it is as long as I make it the same on reassembly. Does anyone know what this mkp stuff is in good old ft/lbs. Also, is there a torque setting for the slotted nut again in ft/lbs if I have to replace the crush washer.

7. If I have to replace the crush washer, is it the small shim in front of the roller bearing or the spacer sleeve between the bearings or something else not on my parts list!

Sorry to babble on and ask so many questions but hopefully someone who has tackled this job will be able to point me in the right direction.

[A Dalton]

If the pinion seal is leaking and the hanger mount looks OK , you do not have to pull the front diff housing/plate.  The front flange is all that has to be removed. Indexing of the retaining slotted  nut is the easiest way to get bearing preload retainment without fear of upsetting the crush sleeve. A pin wrench is usually the best for nut removal. The seal is easy to pry out by puncturing the seals outer metal ring around the circumference and prying it from opposite sides  [ like any pressed seal] Some use a sharp screwdriver , I use a sturdy all.
 I have a Snap-On Torque-O-Meter , so I alway check the preload anyway, as you are there anyway and I usually get a little more out of the nut without exceeding turning spec. [ approx 1/8" past your index mark , not to be confused with 1/8 turn] This is done b/c indexing only gets you back to the previous preload, which you are only assuming was correct. Someone else may have been there before you or  bearing wear may also effect it, so a quick torque check is easy enough to do. I see you have done some homework, so you are aware of the possiblilty of too much torque resulting in the crush reaching point of No Return, so easy does it , in small steps..
One reason why most just go for the Index technique.......
 One also want to check/clean the vent on the top of the left axle casing for blockage and check diff. for possible over-fill . Both of these are over-looked, primary  causes forleaking pinion seal

[DavidBrough]

Thanks Arthur, I can now go ahead with a lot more confidence.

[DavidBrough]

Hi Guys, started the job of replacing my pinion seal whilst waiting for other parts to arrive and hit a snag almost straight away as the drive shaft won’t release from the diff. I removed all the bolts but the prop is very tight against the diff flange and will only move with significant leverage from a pry bar. Do I need to release the tension from the front of the shaft first; my manual makes no mention of having to do this. If I do can anyone confirm the size of the nuts before I go and buy some spanners as they seem very large. My caliper says they must be 42mm and 46mm is this correct? Also, which way loosens the tension, I assume a clockwise turn on the rear adjuster when facing forward, is this correct? Finally, should the drive shaft be adjusted this tight when replacing?

[DavidBrough]

Actually, just had a thought, can I release the tension using just one spanner with the transmission in park?

[DavidBrough]

No panic, borrowed a large adjustable and when I'd worked out it was a lock and not an adjusting nut I turned it the right way and the drive shaft is now off.

[DavidBrough]

OK, next update. That slotted nut's a ****. Ground down a 1/2" drive 1" socket and made it quite a good fit. Does a 3/4" drive socket make a better fit and should I get one?

However I suppose 100+lbs of torque takes some moving and trying to stop the socket from jumping is near impossible with the car on stands. I'm using a 14" tommy handle but have had to give up. Will try to get the car higher tomorrow so I can try the 24". Any thoughts gratefully received apart from go to the gym and pull harder that is.

[Ricardo]

Hey David
I too, made one from a 1/2" drive and it stood up to the torqueing, but I found I had to get assistance with keeping it seated...two person job as it turned out...probably the proper tool works just enough better....

[JimVillers]

David .... I found that an impact wrench was needed to remove the slotted nut in my car.  It was impossible to hold and torque everything.  It was my "excuse" to buy a compressor many years ago.  With an impact wrench, it came off in 2 seconds with in creditable ease.

Jim Villers
190SL, 230SL 5-Speed, 190E 2.3-16 Kompressor

[Markus]

Regarding the ride height I too just went through all the calculations, and consternations that you did with spring color codes, options,  etc. BBB, and ended up having to remove the new 30 and 32.5mm rubber buffers on top of the springs, and replace them with the original thickness rubber buffers, 18 and 20mm. The bottom line is this. If the springs are not broken or out of spec, use them, and replace all the suspension,rubbers, mounts, bushings with original spec replacement parts. Odds are, your ride height will return to look perfectly stock after the mounts, and rubbers have been replaced. Would recommend the thicker rubbers on the compensating spring though, since the thinner ones squish out too easily. A small change in rubber thickness on top of the springs makes a significant change in ride height,and camber in the rear particularly. It also makes the car look ungainly.

[DavidBrough]

OK guys, time for a progress report. Took Jim’s advice and purchased an impact wrench but the slotted nut just shrugged it off. In the end I put it all back together and took it to a local garage that had no better luck. They tried heavy duty air and electric impact wrenched and long breaker bars with a number of burly blokes on the end and some heat. Nothing. They gave up in the end being unsure just how much heat and muscle could be applied without actually breaking anything. Has anyone come across this problem before and any advice on the levels of force and heat that can be applied?

In the meantime, my new rear suspension rubbers have now arrived so I won’t be idle at the weekend.

[ja17]

Hello David,

Have you cleared the metal lock plate out of the slots in the flange before attempting removal of the slotted nut?

Joe Alexander
Blacklick, Ohio

[DavidBrough]

Hi Joe, Yes I think so. My new lock plate is a ring which goes around the outside of the slotted nut between the nut and the flange and I assume this is fitted and bent onto the back of the nut prior to fitting with the lock then being provided by bending a portion of the front into one of the slots on the flange. When I removed the prop shaft, one side of the existing ring was bent into a slot on the flange and I just straightened it out and started trying to remove the nut. Is there more I should do?

[DavidBrough]

Well, I’ve now fitted the new top diff hanger mounting and replaced the top and bottom spring rubbers. Old top mountings were 14mm and I replaced them with 20mm, didn't bother replacing the springs at this stage. Rear camber angle is now 1deg positive but without the hardtop. Car looks much better and rides very well. I have a new set of 6mm rubbers for the compensating spring and I think that these will give the proper 1.5deg camber with the hardtop in place. Had a quick go at removing the comp spring but my spring compressors are far too big, I will have to find a much smaller pair. Does anyone have any tips on removing the comp spring?

[jeffc280sl]

I think the best way to remove the comp spring is to use spring compressors just enough to take the load off the spring end bracket which is bolted in place.  Once this is done you can unbolt the bracket and remove the spring.

Jeff C.
1970 280SL 4-speed