Nate Kern's R12S front spring issue - Page 2

BMW Atlanta · 06-22-2006, 06:19 AM

Quote:

Originally posted by blkduc1
Well Ok then....... I just thought they do a lot of set-up and do a lot of suspension/ shock work and tuning. Figured they might have a way to customize a spring or two for Ohlins or whatever........ There's a shock on the back and one on the front...... right??? Figured if Nate told them what he wanted they might be able to make it happen. And they are close to y'all. Just a thought. Hope it all works out.

Good runnin' to Nate!! We rootin' for ye!

Yeah, one would think and Max is too busy running the place to do it himself these days. Which means I spent 10 minutes yesterday trying to school one of his guys on BMW's and that the front shock actually has a 62nm rate spring to which his reply was front springs numbers have nothing to do with rate which is the case on fork springs,.........not Ohlins front SHOCK springs as found on the telelever.

Appreciate all the suggestions, however Ohlins doesnt do custom set up for BMW's, they only apply known good set ups and since their name isnt on the side of the bike there's too much cost for them to make a custom spring. Try calling Ohlins and asking for a stiffer spring on an R1100S Ohlins,...they will fight you to the end and not reccomend an 85nm front spring. Yet it's a known good set up for Nate, Myself and many others. However Kent at Computrack is much more willing and able to help and will be custom ordering a spring if the out of the box Ohlins spring turns out to be the wrong application on this new R12S. This new R12S front end is a bit different then the old. We can use some of the same tricks, but the geometry is different enough to have to relearn what to change. Between the newer gen Telelever and Paralever, its a challenge!

BMW Atlanta · 06-22-2006, 06:24 AM

Quote:

Originally posted by jalopy
Is there any chance you could use RR's idea of cutting down a spring on the 210mm to make in an 85 Nm 190mm?

Is a spring rubber like NASCAR uses out of the question?

On geometry, consider the fork tubes as the hypontenous of a triangle. With springs in the tubes, they compress with both horizontal (braking) forces and vertical (weight = mass x acceleration) forces. The Telelever, Earles and Duolever transfer the horizontal forces to the frame without (much) spring compression (how "much" depends on how horizontal the arm is.) Vertical weight forces compress all designs, and remember that at head dragging speeds there's a lot of centrefical acceleration that to the spring makes the bike look heavier. (Note that I'm calling vertical reletive to the bike whether it's leaned over or not.)

And finally, since this is post #1 for me here, if you think passing "fast" modern sport bikes on a race track is fun on a new BMW (All oilheads are "new" to me), you should experience it on Vintage! So N8, I hear you're just a super nice guy, but if they're not faster than you and your gummy cow, they won't talk nice to you at the track.

Already been considered, but would most likely make the front 85nm 200mm long spring we have swapped in too stiff. The other possible option is to lengthen the front shock internally to alleviate some of the pre-load in order to manipulate the telever/sag/leverage geometry. Second option is to shorten the stock front spring to stiffen it as there is some room on the threads to loose spring length and gain spring rate as a trade off. I think the ideal spring is going to be about 75-77nm in a 190mm length. That will have to be custom wound.

BMW Atlanta · 06-22-2006, 06:26 AM

Quote:

Originally posted by acidburn
i do not have access to my shop right now, i have two sets of ohlins for my 02 r1100sa, i believe that Ram Jet has the spring specs for both sets, one with Eibach springs one with official olies springs, i was diving the front end too far / hard on the street, have a similar problem to what is being described here,, increased F&R shock spring rates fixed that.
I will loan the spare shocks or springs if it is needed or is in time.
For the left coast, Lindeman and Kyle get it done right.
Kyle seems to have excellent access to spare springs, ohlie factory stuff.

Ohlins doesnt make what we need. Not in the USA and not in Europe according to their charts. Everything in the rate we are looking for is too big of a diameter to safely fit on the shock body.

roger albert · 07:00 AM

>
Which means I spent 10 minutes yesterday trying to school one of his guys on BMW's

BTDT. Funny, eh?

Again, if someone would get me the full dimensions, I might could come up wth the spring (custom). Nate's bike might need to run an extra sticker or two though.

So, k=76 N-m an l=190mm, right? I.D needed to fit spring seat properly (both top and bottom?) Max allowable O.D. to provide other needed clearances (both top and bottom) ??

Let me know. No guarantees, but...

badger · 06-22-2006, 07:08 AM

Ya, know, I can't contribute squat to this thread, but I wanna say:

This has gotta be the most awesome thread I have ever seen on any BBS anywhere

Freakin' awesome! Go N8!

HugoVW · 06-22-2006, 12:00 PM

An interesting article about anti-dive can be found here:
http://www.tonyfoale.com/Articles/Dive/DIVE.htm
So if BMW changed the CoG position (and I think they have; doesn't the new S has more weight on the front?) then the anti-dive characteritic is already altered. Setting up a bike with a different front suspension then teles is difficult because the bike tends to react different to input parameters.

Hugo