Shocks... because somebody had to do it.

[Dust]

I like the Bilstein numbers mean something...
So, now if I could just figure out how many Newtons I can get tin the bed of my truck and launch it off a berm so that I can calculate which that many Newtons the truck went from full extended on the shock to full compressed {in inches} and convert that to mm'z and then factor that by say 0.02 seconds to get something in meters per second...

Ya, it is all smoke and mirrors and I agree call a magician, because I ain't one.

[randomthoughtsracing]

The Bilstein numbers like 170/60 mean 1700 newtons of rebound and 180 newtons of compression at .5 M/S. The catch is that with piston or other changes it takes a differant valve stack to generate those forces. I dont use these premade methods for race applications. Yesterday I tried to post the new spreadsheet for the 60mm piston but this site dosent allow PDF. In the future we plan on dynoing each valve profile so that the stacks can also relate to performance. I have yet to decide what shaft speed to use for the forces though since .5m/s is rather slow for hard off road use. I am leaning more towards 1 m/s. Opinions of Party and Kris would be appreciated.

ADMIN EDIT: Image added. You can also use the link below for a pdf file that might be easier to zoom-in.

https://docs.google.com/fileview?id=19v ... MTdR&hl=en

[SteveG]

Joel, if you email the pdf file to gofastbroncos (at) gmail.com I can upload it to the site Google Documents page and post the link.

[randomthoughtsracing]

Usually when shafts bend it's for something else failing or poor setup. If everything is set-up correctly, 3/4" is plenty large enough for anything. 5/8" is good enough for 75% of the stuff out there.

To revisit shaft bending a bit more... the bending comes from some kind of bind or side loading. The shock is at its weakest at full extension and the longer the travel the more seceptable it is to bending. This is where the rod guide, tube, piston tolerances, and bearings come into play. Attached is a photo of what I am talking about and call the "bearing support length" measured from the end of the wear band (which is a bearing) to the end of the rod guide or wherever the support ends at the seal head.

Outside of the shock I have seen bending caused by a number of influences. Coil bind, rubber bushing bind (under articulation), or binding contact between the rod end spring hat or other part of the shock against the chassis.

For rubber mount shocks like the 5100 or 5150 I reccomend changing the rod side rubber bushing to a heim end from the 7100 series shock to reduce the possibility of shaft bending bushing bind.

[randomthoughtsracing]

Joel, if you email the pdf file to gofastbroncos (at) gmail.com I can upload it to the site Google Documents page and post the link.

Thanks for posting the chart.

For reference a full size bronco rear bypass valving would start at...
30 -10 rebound
30 -6 compression

[Dust]

All of the bent shafts I have seen that were not bent by an external object (A log stuffed through the suspension for example) were SRE's and Coil-Overs. I do not think I have ever seen one that was rubber or poly mounted... that bent for "no reason". Obviously there is a reason.

I have wondered about the piston and bearing on some of them, In one case (Doestech sp?) it really looked like the shaft was on the small side, like they made a Street Shock an 'Off Road' be making things longer. Still it should not have bent.

[shockseals.com]

All of the bent shafts I have seen that were not bent by an external object (A log stuffed through the suspension for example) were SRE's and Coil-Overs. I do not think I have ever seen one that was rubber or poly mounted... that bent for "no reason". Obviously there is a reason.

I have wondered about the piston and bearing on some of them, In one case (Doestech sp?) it really looked like the shaft was on the small side, like they made a Street Shock an 'Off Road' be making things longer. Still it should not have bent.

Most bent or broken shafts I have seen are sideload issues at full hang (only takes a little bit of sideload and a lot of shaft speed) or mounts that bind. A rubber or urethane mounted shock usually doesnt see the abuse a SRE does as the urethane wouldnt live in the same environment.

If it is straight buckling the only cure is larger diameter. Rick Husemans pro4 when the truck was still being dialed in we tried 7/8 shafts and they last a lap or two before breaking.

[shockseals.com]

Ya, it is all smoke and mirrors and I agree call a magician, because I ain't one.

Bilstein's is not smoke and mirrors. Granted they only list 1 shaft speed, if you called im sure you could get damping forces at multiple shaft speeds for a specific valving they sell and they could probably help you out if you wanted changes at specific shaft speeds, but then again you need to be able to relay exactly what the car is doing "wrong". I know with the OEM shock supplier I work with their prints have 3 forces at 3 speeds(low/mid/hi) for compression and rebound and thats all I need to know if im in the ball park or not. Granted they have 50 different pistons for me to choose from as well to get to the numbers I request when im tuning but thats OEM and OEM is a lot more precise than offroad.

I know King purchased an EMA so we may see some real numbers from them soon.

[Dust]

Ya, it is all smoke and mirrors and I agree call a magician, because I ain't one.

Bilstein's is not smoke and mirrors. Granted they only list 1 shaft speed, if you called im sure you could get damping forces at multiple shaft speeds for a specific valving they sell and they could probably help you out if you wanted changes at specific shaft speeds, but then again you need to be able to relay exactly what the car is doing "wrong". I know with the OEM shock supplier I work with their prints have 3 forces at 3 speeds(low/mid/hi) for compression and rebound and thats all I need to know if im in the ball park or not. Granted they have 50 different pistons for me to choose from as well to get to the numbers I request when im tuning but thats OEM and OEM is a lot more precise than offroad.

I know King purchased an EMA so we may see some real numbers from them soon.

Whoa, don't take that line wrong!
What I (obviously) failed to say is if you do not have the data to plug into the formula you can not use the formula, thus it in direct application may as well be smoke.
Further I will be making just that call tomorrow. I am in effect calling the magician.

C

[randomthoughtsracing]

...
I know King purchased an EMA so we may see some real numbers from them soon.

Nice, I hope it is the 6k! ... 8 m/s

http://www.roehrigengineering.com/Produ ... 20page.htm