Sumo Springs, Tires and Alignment

[Tiato]

This past weekend marked the start of my 2015 track driving at Watkins Glen. In prep for this years towing I performed some further suspension enhancements over and above my rear Konis.

In my philosophy of incremental improvement in order to feel each individual upgrade I was for a while undecided on front koni struts or front and rear Sumo Springs. After much deliberation, I opted for the lower expense of the Sumo Springs. While the install was not difficult at all, it is good to know or take this modification as a stepping stone to learn how to jack up the coach using the factory Mercedes jacking points. Needless to say that little bottle jack left me mightily impressed.

After finishing the work and immediately as I started down my driveway, I could feel magic. From the get go, the Interstate felt smoother. Upon crossing the 1.5" belgian block lip at the bottom of my driveway I could immediately feel less rear chassis sway. The road test left me nearly speechless. The ride was so smooth and composed. Amazing. I must add that I believe that the sumo springs raised the front ride height a bit as the camber looked a bit more positive in addition to the +camber present before the change.

Of course the real test was 2 days later. A 230 mile tow to Watkins Glen, NY. The winter scarred roads of NJ, PA and NY were my test track. The ride was super smooth. The chassis much more composed. Even the numerous winter damaged roads were made tolerable. Rear chassis roll was significantly reduced and the rolling completed much quicker.

Of course winter had a hard time letting go last week. Strong crosswinds and continuous flurries made the ride a bit more interesting. In cross winds the chassis would still sway but at a reduced rate. Large rigs passing? Hardly affected the ride.

Best of all, my wife commented how much the ride has smoothed out.
Great ride improvement. Wife approved. Win, win.

At this point I do not see a reason to upgrade to front konis at all, or a rear anti roll bar. These bump stops deliver an amazing ride for little money.

But riding on bump stops? Yup. Even BMW has done that. Case in point: The e90/e92 M3. BMW designed the dampers to have limited travel and are spec'd with a reasonably soft spring. Yet the ride is still pretty damn good when driven hard in the corners. How did they do it? Progressive rate bump stops. Same principle with these Sumo springs. These bump stops are nothing more than auxillary progressive rate springs that work in conjunction with the suspension, improving the ride.

To cap off the week of prep, the stock Continental tires were replaced at 17,000 miles due to excess outside shoulder wear. New Michelin LTX m/s2 were installed. Super ride.

Today I had the front end re-aligned by a local shop. Finally had the positive camber neutralized. Took it from a pre alignment setting of +.9(left) and +1.3(right) and reset to a static 0. Toe was reset by 5 degrees on both sides (initial .29 left / .28 right) set to a more factory reccomended of .24 to .22 degrees. Caster remained unchanged at 4.6.

By loosening the front strut knuckle bolts, there is enough adjustability to get the camber to a more tire friendly number. No camber bolts neccessary.

How does it ride now? Solid smooth with just a bit more steering weight. Guess that's what happens when the front goes from riding on a skinny strip of tread to the whole tire tread face.

All in all a busy week of work with positive results. I look forward to this Thursday when I can test the whole enchilada on another trip to Watkins Glen.

[jerhofer]

Were these the jounce springs? Is the installation a matter of replacing the bump stops with these units? Where did you get them and how much? Did you happen to take any photos?
Thanks.

[Tiato]

J,-

Yup, the jounce springs. Use these to replace the OEM ones.

Got the SSF-160-40 fronts from some vendor on Amazon for about $151.

The rears, SSR-335-47 from etrailer for about $180

SumoSprings Custom Helper Springs Kit - Rear Axle - Medium Duty SuperSprings Vehicle Suspension SSR-335-47

I took no install pix. The underchassis road grime makes for dirty hands. However, this post from the sprinter source forum shows the same images I would have taken:

Sprinter-Forum - View Single Post - Sumo Springs

[jerhofer]

Thanks for the info. What do you run at Watkins Glen?

[jerhofer]

Another question. I am most interested in doing something about the ride in the rear. What do you think about only installing the rears?

[Tiato]

Hi Jerry,

Previous cars raced and tracked at the Glen is a '96 M3 race car built for BMW Club Racing, a 2008 M3 sedan and more recently a dedicated track prepped 1996 BMW M3. I consider Watkins Glen my home track and my wife and I spend about 14-18 days a year driving there.

2014 post build shake down of my current car:
https://vimeo.com/109694763

For the rear, as a budget mod, the rear sumo springs will definately help and would be a good start. But I think you really need to upgrade the shocks eventually. The rear of the coach is extremely underdamped for the weight.

You will find that with leaving the front end unmodified, you will feel a roll differential rear to front. The rear will roll less than the front and the rear will feel much better than the front. An unbalanced chassis irks me because my race and track cars have made me so sensitive to it but you might find it ok.

[jerhofer]

Originally Posted by Tiato

Hi Jerry,

Previous cars raced and tracked at the Glen is a '96 M3 race car built for BMW Club Racing, a 2008 M3 sedan and more recently a dedicated track prepped 1996 BMW M3. I consider Watkins Glen my home track and my wife and I spend about 14-18 days a year driving there.

2014 post build shake down of my current car:
https://vimeo.com/109694763

For the rear, as a budget mod, the rear sumo springs will definately help and would be a good start. But I think you really need to upgrade the shocks eventually. The rear of the coach is extremely underdamped for the weight.

You will find that with leaving the front end unmodified, you will feel a roll differential rear to front. The rear will roll less than the front and the rear will feel much better than the front. An unbalanced chassis irks me because my race and track cars have made me so sensitive to it but you might find it ok.

You're probably right about the balance and the shocks. It is a relatively inexpensive fix compared to the air suspensions and, based on your experience, should be worth a try. Did you find jacking up the truck on the frame rail allowed for enough suspension droop to install the Sumosprings?

I enjoyed the video. Looks like you have the car dialed in well and you obviously know the line after that much track time. It's good to see you using the entire track instead of the sanitized version that NASCAR runs. Based on the fact that they can make very few laps without a yellow flag on that course, I can see why they don't do the full track. Even more chaos would erupt. The M3 would make a great track car. I had E36 and E46 M3's and loved them both.

My wife and I both used to do track events. As a 37 year Porsche Club member our track cars were all Porsches. Being from northern Indiana, we mainly drove on the Midwest tracks...Road America, Mid-Ohio, Blackhawk Farms, Grattan, Gingerman, Putnam Park and Waterford Hills. I did venture somewhat further to Summit Point, Pocono, Road Atlanta, Sebring and I even made it to Laguna Seca and the infamous corkscrew. We drove at Watkins Glen only once and had very little track time as the car broke.

And it was an exciting break!! We were driving a 1962 Porsche 356 E-Production car. I was entering the boot at full bore. When I hit the brakes, the car immediately turned left and all hell broke loose. This happened in the late '80's and, at that time, that blue guardrail was very close to the edge of the track. To this day I don't know how I did not hit it. I spun and ended up in the grass at the outside of the turn. The corner worker rushed over to see if I was OK and asked what happened. Told him I had no idea. Turned out that I had broken the right rear trailing arm causing the right rear wheel to be pushed back under braking and providing me with a rear steer car. It could have been much worse.

The photo below shows my wife driving that car at Grattan Raceway in Michigan and a much younger (and much skinnier) me in the red shirt working on that car at Watkins Glen. We removed the part, found a local welder on a Saturday to fix it, re-installed it only to have it break again. At that point, it was decided that someone did not want us to run at Watkins Glen!! It was a shame as we loved the track. This was before they installed the chicane. When I got back to Indiana, I had a local fabricator make two new trailing arms and we never had this issue again.

[Tiato]

Jerry,

Well, Ill be....

(edit: Ahhh....youre the fellow who posted the awesome tow bar install thread for the Abarth. Awesome work!!)

Greetings to a fellow track lover.

Nice Porsche! Totally relate to the husband/wife driver set. No doubt a mechanical failure into T6 will make for an exiting adventure. T6 is one of my favorite turns and the only turn at the Glen where I almost had in contact with the armco when I lost it in a club race in a rented race car at the apex.

Did Skip Barber at Road Atlanta and have raced/driven at NJMP, Summit, Mid-Ohio, Lime Rock and VIR. I have heard of the other midwest tracks but have not yet had any opportunity to drive them. Got this || close to once racing at Nelson Ledges. Sadly, that track is now closed but I heard the racing surface was killer on the equipment.

However now that my active race days are behind me (dont get me wrong, I still race for the hell of it when I can get a seat in someone else's car) I spend my time instructing or coaching with a few NE clubs. This weekend I have the pleasure of instructing a student who drives a 650+hp Nissan GTR.

For the rear bump stops, I drove the coach onto a stack of "lego" leveling blocks. The jack point for the rear is in front of the spring mount closest to the propane tank on the right side and in a similar spot on the right side. Look for a wide rounded surface. Once you see the tip of the bootle jack you will see and find its somewhat matching counterpart on the chassis. Jack one side at a time. The OEM bump stops will pull out with enough force but slide one end of the OEM stop either as far rearward or forward as possible. With that done, one of the block lips will be deeper on one side and one shallower. Push against the shallower side to dislodge the block.

[Msmoto]

I do not know what this has to do with Airstreams, but as I have had a few Porsches, I could not resist. First Porsche: 1958 1600N Coupe, daddy bought this for me in 1960. Current: 1999 996 Cab, 111,000 miles and have driven it in nearly all the 48 states.

In September I will be at the VSCDA event at Road America, here is one from last year.... rain and 40 degrees...
Road America_VSCDA_III_09.13.14 by Fantinesvoice.com, on Flickr

When I saw the word Porsche, had to contribute....LOL

[jerhofer]

I quit track events in 1998 when a promotion moved me to Missouri. Not as many tracks available there and my new job was demanding lots of my time. And I had never wrecked any of the track cars so it was a good time to quit.

VIR was closed while I was doing events so I never had an opportunity to drive there. From what I hear, it is a great track. I am going to try to make the vintage race there this September so I can at least see the track. It is only a two hour drive from here so we will probably just drive up for the day.

We ran an '83 944 for five years after I sold the 356. The 356 was a high maintenance car as Vic Skirmants, out of Detroit, was getting 165HP from that little 1.5 liter air cooled motor. It had absolutely no power until 5000rpm and was done at 7000rpm. Very narrow power band made it difficult to drive but we both learned more from driving that car than any other. The 944 was just the opposite. Right after I bought it I installed new rotors and brake pads. While I changed a number of brake pads over the next five years, those rotors were never changed. My son then drove the car for another three years after he graduated from college. We pulled a small trailer behind it with our track tires, tools, etc.



For the last two driving years we drove a 1982 Porsche 911SC with an '89 Turbo motor. 400hp and 2600 lbs made for a very, very fast car. At Road America, I was touching 150mph on the three straights. In spite of having a full cage, I drove it on the street and actually took it on business trips. It was so much fun to drive.

[jerhofer]

Originally Posted by Msmoto

I do not know what this has to do with Airstreams, but as I have had a few Porsches, I could not resist. First Porsche: 1958 1600N Coupe, daddy bought this for me in 1960. Current: 1999 996 Cab, 111,000 miles and have driven it in nearly all the 48 states.

In September I will be at the VSCDA event at Road America, here is one from last year.... rain and 40 degrees...
Road America_VSCDA_III_09.13.14 by Fantinesvoice.com, on Flickr

When I saw the word Porsche, had to contribute....LOL

We used to go to the vintage races at Road America nearly every year. My favorite track to drive and spectate at. How can you go wrong with four miles of track, Johnsonville brats and beer!!!

[Titus]

In your original post: "it is good to know or take this modification as a stepping stone to learn how to jack up the coach using the factory Mercedes jacking points."

How (where?) did you jack up the rear end given that A/S has covered up the intended jack point?

[73shark]

Don't feel bad if you can't find them because when I had mine in at the Mercedes dealer, they couldn't show me the jack points either.

[unifreck]

Just added the Sumo Springs to the front and rear of my 2005 Interstate, after having the heavier sway bar and koni shocks installed by the Sprinter Store last year. What a great combo on the 2500 chassis. I may be ready to race you guys because my INTERSTATE feels like it is on rails. Thank you very much for the performance enhancement suggestions. Passing trucks just got a lot easier and safer.

[jerhofer]

The Sumo springs and the rear Koni's have been installed. Huge difference. The AI doesn't rock side to side like it did and is more controlled over rough roads. There is noticeably less dive under braking and rear squat on takeoff. Well worth the money!!! My buddy bought a 31" camper trailer recently. We are driving out to western NC tomorrow morning for his maiden trip. It will be interesting to see how the AI works on the interstate. I don't normally wish for wind but I would like to see if it is better in windy conditions.

As for riding on the bump stops, that is what NASCAR is doing. Their cars have become faster once they were allowed to do this. My son is a mechanical engineer and works for Toyota Racing Development He is in charge of tire and suspension testing for the NASCAR teams so he has been very involved with this change. Prior to working in NASCAR he spent 12 years designing race tires for Michelin. He learned a lot at Michelin but there is much more money to be made in NASCAR!!! Doubled his salary when he made the switch.