Front end riding rather high

[Woodstock]

Just purchased a 1971 280SL.  The car has about 100K miles and within the last 2K miles had the front and back Bilstein shocks replaced.  Measuring from the center of the wheel (Mercedes star center on hubcap) to the bottom of the fender is 12 7/8" on both rear wheels and 15 1/4" on drivers front and 15 1/2"  on passenger front.  Needless to say this is not right.  I have read some of the articles on this site concerning this situation and the recommendation to replace the springs.  We have taken the front shocks out (which are gas shocks) and with the shocks out the front end settles down to an acceptable height.  This leads us to believe it is the shock that is impacting the ride height and are questioning whether change the springs will remedy the high front end.  I do understand that if the rear springs are bad (collapsed to some degree) this would impact the difference between the front and back readings, but I am at a loss to see how this would bring the front end down.  Therefore I would appreciate any advise from the experts on this forum concerning the proper next step to take.  I am leaning to putting sport springs all the way round just to improve the handling since this will be a vintage rally car that will be driven on twisty roads at speed.  The sport springs should also help the nose dive the car experiences if nothing else.  Thanks in advance for any feedback.

[Cees Klumper]

Not a suspension expert, actually a real layman when it comes to suspensions, so take this FWIW:

- the shocks likely exert a mild upward force on the body and thus the springs. If the springs are really tired, they may ´give way´as a result and stretch out in the front, allowing the front to lift, when springs in good condition would not stretch. Otherwise, the springs and the weight of the body should not allow the mild upward force of the shocks to influence the ride height

- also, if the rear springs are really worn and sagging, more so than the front ones, then they may be allowing the rear of the car to ´sink´; if the front springs are in better shape, keeping the front where it should be, then it only looks like the front is sitting too high, when in fact it is the rear that is sitting too low

My advice, especially given that you are going to drive the car in rallies, is to get 5 new springs and to go for the progressive rate ones. A group member once let me drive his car with as I recall the John Olson supplied progressive rate springs, and the ride was really nice and certainly no longer had the nose dive on hard braking that is so typical of our cars.

I´m sure more knowledgeable members will chime in soon and correct my amateur advice!

[ja17]

Most likely the rear is riding low. Typical ride heights for the rear are 14 to 15 inches (plus or minus)

[Woodstock]

Thanks for the input ... beginning to conclude the rear springs are sagging and probably need to replace all springs with sport springs.

[Shvegel]

Talk to John Olsen.  I seem to recall he is now advocating a mixture  of Sport and progressive springs he makes. 
His email is office@slmarket.com

[Woodstock]

I have been talking with John for the past several days.  Am leaning towards replacing all springs on the car with Sports Springs for improved handling.  I am sure these springs need replacing.  Just trying to sort out this ride height issue when I am shimming the springs.  Based on maintenance records I noticed that my car had the subframe mounts replaced about 2K miles ago and there was a post on this site that indicated that replacement of these mounts raised the front end of the car by 3/4". 

Based on all the posts I have reviewed on this site and talking to my mechanic and others I am thinking I need to replace the springs with sport springs.  I also may need to replace the new Bilstein Gas Shocks with Konis to get the front end to drop down to an acceptable level.

[stickandrudderman]

The sure way to tell is to find your nearest race car mechanic and ask him if he can check the spring rates for you.

[Iconic]

Based on maintenance records I noticed that my car had the subframe mounts replaced about 2K miles ago and there was a post on this site that indicated that replacement of these mounts raised the front end of the car by 3/4". 

You might have the wrong subframe bushings.
My understanding is that some vendors were selling the much less expensive subframe bushing from another Mercedes and claiming it is for a W113 Pagoda. It is slightly taller and brings the front up a bit and is the wrong part.

[Woodstock]

Iconic:

Good to know the sub frame bushing may be wrong part.  Will check out the part number.

Thanks for the tip!

[ja17]

The individual sub-frame mounts themselves carry the same part number for the SL or the sedan and are the same. The sub-frame kits for the SL and sedan  are different. The "SL" sub-frame kit,  has the metal stop plate included in the kit. The sedans do not use the metal stop plate so it is not included in the kit. The metal stop plates do not wear out. If you choose to use your old stop plates you will save around $300 by buying the sedan sub-frame mounts which are the same. Also notice that the four mounting bolts for the sub-frame mount in the sedan kit are too short since the extra thickness of the stop plates must be considered on the SL. In this case use your old mounting bolts or order four new ones, they are standard metric hardware and inexpensive. The main large center bolt is the same in both kits. Use the new ones provided.

In most cases, the total ride height of the car decreases with age and miles. Rubber spring pads and mounts compress, rubber sub-frame mounts compress, gas shocks weaken, and springs get tired and sag a bit. Often times renewal of the front subframe mounts will raise the front of the car to near original specs, but the tired rear rubber or springs will make the rear look too low or the front seemingly too high.

Measurements from the center of the wheel cover star, straight up to the lip of the wheel opening, will tell the story. Seems all the cars are a little different. Most of them that I see are 14.75 to 15.25 inches at the rear. Correct tire size is critical since improper tire diameter will throw the reading off.

Minor ride height of the rear is possible by changing spring pad rubber thickness and rotation adjustment of the lower spring plate. Don't forget to use the lower spring rubber. They are usually missing or out of place after years of use. I like to use some contact cement or rubber weather strip adhesive, to mount the lower rubber to the plate, so they stay in place.

These cars were equipped with hydraulic/gas filled Bilstein shocks when new. Gas filled shocks provide some up-force when new, less when old or worn out. Very slight change in ride height may be noticed after installing fresh gas filled shocks.

There are lots of variables and choices to make. New rubber mountings and shocks often times make an incredible improvement in ride quality.

[Iconic]

Measurements from the center of the wheel cover star, straight up to the lip of the wheel opening, will tell the story. Seems all the cars are a little different. Most of them that I see are 14.75 to 15.25 inches at the rear. Correct tire size is critical since improper tire diameter will throw the reading off.

Woodstock,
Sorry if I misled you. Joe is saying it is the same part, and therefore the same height. I was sure there was some wrong part that people were selling for the same application, but was taller, maybe 6 or 8 mm or so. In case you haven't been on the forum much, I will tell you that Joe is one of our experts and certainly knows more than me. So, trust him !!!

Joe,
If we measure from the center of the wheel cover star, to the lip of the wheel opening, isn't the tire size irrelevant? The car needs to be on the ground, of course. But, it seems to me the diameter of the tire will not play any role in the measurement from the center of the wheel cover up to the lip... am I missing something??
Mark

[ja17]

Yes Mark, you are right on the tire diameter and the measurement. Thanks for the correction. Tire diameter will effect the ride height but not the measurement from center to lip. 
Also in regards to sub-frame mount heights, I cannot say for certain that the different aftermarket manufacturers are making the mounts to MB specs exactly. However, the individual sub frame mounts for the SL and the W108 sedans do carry the exact same MB part numbers, only the kit part numbers are different.

[Woodstock]

Thanks for all the input.  Based on all this information I have concluded that the first place to start would be to replace the springs with sport springs.  Due to the low rear height numbers I am fairly certain the rear springs are sagging.  I will hold off on replacing shocks until I have installed new springs and shims all the way round and see how the height fluctuates.  My tire size is 195/75/14 as compared to 185/78/14 would give a slightly larger difference in diameter ( 144.3 vs. 146.25 if my math is right).

[Benz Dr.]

I changed the whole sub frame on my car with parts from a 250SE coupe. Of course it was too high at the front because of the coupe being a heavier car. Once I changed the front springs it sat perfectly.