MBWorld.org Forums - CL Handling Project

All, I have been asked by several members to post the results of my 05 CL55 handling project since it has general application to all CLs. This project evolved over my 10 years of ownership of the car and so I think it is worth giving a little background on how this project developed as I think it is still possible to improve on what I did and make the car handle even better.

In the mid-2000s there were a number of car magazine articles that compared the CL to the other high end European GT coupes of the day, notably the Ferrari, Aston Martin, Bentley and Jag. Typically the articles would say the Ferrari won with a close second by the CL. However, the interesting thing is that the Ferrari typically won because of cachet, not really on the merits. One of the typical articles was the following:

https://www.caranddriver.com/reviews...mparison-tests

In the article it said this about the CL’s handling: "Then there's the semi active hydraulic suspension. It's a system of sensors and computer-controlled hydraulic rams and shocks at all four corners. It can instantly adjust from cushy soft for soaking up bumps to sports-car stiff to reduce body lean in corners. It's not perfect--some abrupt freeway impacts send jitters through the body--but in general, it works fantastically. The CL digs into corners with a surprising amount of bite and enthusiasm. One tester wrote, "Wow, very impressive in the turns, feels almost as agile and frisky as the Ferrari."

I actually owned the Ferrari in the article as well as the CL55 and so I was able to personally compare the 2 vehicles. While I agreed that the CL was a great handling car, it didn’t handle for me the way my Ferrari handled. The most noticeable thing I found was the steering response was “soft” in comparison to “go kart” handling feeling of the Ferrari. But I started to read up on the merits of the CL’s ABC suspension system and decided that Mercedes had “dumbed down” the system to have a one size fit all appeal to little old ladies from Pasadena as well as old street racers like myself, which of course is very understandable from a marketing perspective.

Essentially, the ABC suspension system is designed for heavy luxury cars to counter body lean in corners. This allows for better handling like a sports car but at the same time maintains the comfortable ride of a luxury car. So I wanted to see how far I could push the system by making mods to achieve handling which was more sports car like but at the same time maintain the luxury ride. When I was finished I ended up with a car that could definitely keep up with my Ferrari, had that tight “go kart” feeling in the steering, and still maintained a very comfortable ride. So if you are interested in improving the handling of your CL and also not affecting the ride, you may want to try some or all of these mods, which overall are relatively low cost, are all bolt on and require no great skill or mechanical expertise.

Essentially, the mods I made amounted to this: (1) lowering links to get the car’s center of gravity lower, (2) altering the scrub radius on the front wheels to obtain a more connected feeling in the steering, (3) altering the offsets on all wheels to obtain a wider stance, and (4) getting wider and stickier wheels and tires with thinner sidewalls for improved handling.

If you decide to try any or all of these mods, I suggest you do this little test on a before and after basis to judge the effect. Find a safe 90 degree intersection and take the corner as fast as you feel comfortable doing in your unmodified car without braking. Then after making the modifications do it again. Just for fun, when I was finished my project I put back on the original wheels and tires and raised the suspension back to the original height and did a before and after (in reverse order). I found the results jaw dropping. I could take the corner at a much higher speed and the car felt like a slot car bolted to the ground. The ABC system literally eliminated all body lean and you got to feel the full effect of the mod without any change in ride.

So here are the individual components:

Lowering Links

This is a major part of the improvements and can be done by itself or in conjunction with the other items and is the easiest and cheapest part. I bought my lowering links on eBay and here is a typical link (they vary depending on your model of CL):

https://www.ebay.com/itm/2000-06-MER...frcectupt=true

As you can see they are only about $100 for a 4 wheel set and even if you are not mechanically inclined, they are a simple install. I had my mechanic install them for about $150 if you want to go that route. I lowered my CL by 1.5 inches and the results were dramatic. How much you can or should lower your car will depend on your wheel and tire combination. However, the CL has massive oversized wheel wells and can easily handle significant lowering. Although I could have done more than 1.5 inches, I liked the look at that level and didn’t want the “slammed” street rod look (of course, if that is the look you are going for then this really is for you because there is lots of room). The technical benefit of the lowering links is that it gets the car’s center of gravity much lower and with a car as heavy as the CL this makes a dramatic difference in handling. Also, the beauty of the ABC system with the lowering links is that the system remains fully functional and before and after lowering, the ride is exactly the same. So the lowering does not result in a harsh ride which might result from some other lowering procedures. Also, when you go over rough patches or speed bumps you can easily raise the suspension with the ABC system. So you get the benefit of the lowered ride and handling on smooth roads but can still deal with rough roads at the push of a button.

Wheels and Tires

This is the part that I worked on the most and probably never absolutely nailed. My inspiration, in addition to the magazine articles that I mentioned, were the Brabus modified CL’s of the day (the K8), which were in my neighborhood and which performed spectacularly. So I initially copied their wheel and tire combinations (including getting Brabus Monoblock VI wheels). Here are the finished project’s before and after specs on the wheels and tires:

Before:

Front: 245/45R18 ET44 (offset) 8.5 rim width. Rear: 265/40R18 ET46 (offset) 9.5 rim width

After:

Front: 255/35ZR19 ET40 (offset) 8.5 rim width. Rear: 275/35ZR19 ET35 (offset) 10 rim width

A few things to note here:

On the front wheels I played with the offset using spacers and found that if I altered the offset and the resulting scrub radius that I significantly improved the “feel” to the driver of the steering and got rid of that “soft” feeling and got the much more direct “go kart” feeling. I went from a 0 scrub radius to about a 7 mm positive scrub radius (and the tire only stuck out about 9 mm more than the original). So the front wheels and tires are by no means as wide or as inboard as you can go, I was only looking for the steering response.

On the rears, I was trying for as wide of a stance as I could achieve to improve handling. So this is the absolute maximum width with the 1.5 inch lowering that I mentioned (the tire stuck out about 16 mm further than the original). Note, I actually went a little wider and the tires rubbed when I was lowered so I backed it off. However, there certainly is more room inboard if you want wider wheels and tires, I was merely going for the outboard maximum.

In playing with wheel and tire combinations and offsets I found the following website very helpful:

http://www.wheel-size.com/size/mercedes/cl-class/

This link will take you to the specs for your car and then you can go to the “Tire Calculator” tab and you can compare any proposed change to your car to the original set up and see exactly what effect it is going to have and fine tune it. Although I am not really a fan of spacers, I used them to play with the offset effect and to achieve the overall stance that I wanted. However, the numbers I have provided for offset are “net” of the spacers. So if you have wheels that are not the right offset you can achieve the effect by applying spacers. In using spacers you might need to obtain longer wheel bolts (I obtained a pretty good collection of various sizes over the years). Typically you want the bolt to be thickness of your wheel plus spacer plus an additional 15-17 mm sticking out. You will find Phil at Otis Inc to be very helpful, they have great wheel bolts and will work with you on any wheel and bolt combination that you have and come up with the right size bolt:

Otis Inc LA
RAD USA Direct
toll-free 855.OTIS.INC (684.7462)
toll-free 888.RAD.BOLT (723.2658)
international +01.310.995.8939
https://otisincla.com/

In terms of tire sidewall size, I would recommend 35s and not 30s. I initially tried 30s and found that there was not enough sidewall. Because the CL is such a heavy car I encountered rim damage when going over speed bumps with 30s.

In terms of tires I recommend Michelin Super Sports (the last ones I had were the 4S). Over the years I tried various Michelin and Pirelli tires and found the Super Sports to be heads and shoulders above all of the rest (including other Michelins). They were the most sticky of all the tires and yet had the best ride, lowest noise level and the longest life span.

Also, for wheels I used 19s because that was what Brabus used. Recently a lot of Mercedes have been coming with 20s and there are a lot of OEM wheel takeoffs available at a very low price on the internet. So one thing I thought about was getting some OEM 20s and putting them on the car to get a more current look. You can use the Wheel-size.com site to figure that out since all you need to worry about is the overall circumference of the tire (I wanted to keep it the same as original on the rears for the speedo) and the sidewall size (due to what I discussed above about wheel damage). In terms of ride, you really don’t have to worry about the width of the tires or the smaller shoulder affecting it. The ABC really provides for a great ride even with the mods that I made and I could not discern any change in terms of ride, just handling.

So you can choose to use some or all of the above mods as you see fit. Each part is independent of the other and definitely adds to the overall handling but together they create an awesome handling machine. If anybody tries any of this, let me know how it turns out. I hope you enjoy your CL as much as I did mine. It was the greatest car I have every owned.