Author Topic: Re: K75S radials- mushy in high speed corners and its not all about tires is it?  (Read 275 times)

Offline Rcgreaves

  • ^ SuperNatural Motobricker
  • Posts: 593
I may have issues...sounds like the lead in to a joke:  my 87 K75s would track hands off at any speed.  I want that with K2 or k bike #2.  I have new bearings for the triple tree but it may just be that the clamp on those bearings have loosened so that’s where I’ll start.  I could order up some of that stuff Corning grease and repack the steering damper as a matter of course...25 year’s old, worth a look..
I struggle to imagine how my forks could be twisted or misaligned for stiction until I relive how my 87 looked after sliding on its side at 80 into a ditch- a bent fork would do this right?  point being that I have never taken them off etc who knows what a PO did to/with it so I’ll break out my long straight edge and while I’m installing my low seat maybe reposition things a few mm lower.  Maybe fresh front fork oil.

Is the rear swing arm bushed  in a way that slop could be introduced at the rear swing arm through a worn bushing? Like my Water Buffalos?  I think not.  Maybe the aluminum housing could elongate and get hogged out if loose?? When I install my new T30 in a week I’ll be certain to scrutinize all these pivots.  How do I trouble shoot my rear shock of unknown  age?  Maybe my rear spring preload is set too soft?? I’m a petite 210# after all. Who services rear shocks?.  I’ll look up those settings today and if anything stiffen the rear. 

Pouring rain Sunday morning here in the Chee, good day for service.  Maybe there’s a paralever in my K75 future.  Cheers mates.  I greatly enjoy and appreciate the feedback here.
  • Livingston, SW WI. USA-"With the good earth all around."
  • NEW 1995 K1100RS Red,1994 K75S Red,1985 GL1200A Goldwing Aspencade, dreaming of adding a sidecar to the mix in 2019
Doing “better than I deserve”

Offline Rcgreaves

  • ^ SuperNatural Motobricker
  • Posts: 593
In an earlier reply marshall suggested better than stock front springs.  Ok, what from what source would be an appropriate update front spring update?  Rear damper age Marshall asks— I’ll dig I may have a dated receipt.  Cheers
  • Livingston, SW WI. USA-"With the good earth all around."
  • NEW 1995 K1100RS Red,1994 K75S Red,1985 GL1200A Goldwing Aspencade, dreaming of adding a sidecar to the mix in 2019
Doing “better than I deserve”

Offline mlytle

  • ^ Quintessential Motobricker
  • Posts: 1063
front springs...
-Progressive brand popular, but they are one rate fits all.  i had them.  unimpressed.  ditched them for...
-Race tech, much better.  you get a spring rate that is "fitted" to your usage and weight.  not everyone is the same. https://www.racetech.com/ProductSearch/2/BMW/K75%20C-S-RT/1992-95

#210 is heavy for a stock rear spring when it was new.  30 years later the spring is softer than it was, and guaranteed the damper is shot.  rebuilding waste of time.  just get a new one.  can't go wrong with Ted's https://www.beemershop.com/  there are a range of options.

I have
K75S #1  progressive front/ progressive 465 rear.  works ok on track.  that is all this bike gets used for.
K75S #2  Race Tech front/ Fox DA rear.  works great on track or street
K1100RS  Race Tech front/ Progressive 465 rear.  has not been on track, but very happy with sport touring riding
K1300S    Wilbers DA front and rear with ESA function deleted.  freaking awesome control...track or street.

A good suspension makes a HUGE difference in how a bike rides and handles.  It is not a place to ignore or cheap out if a bike is to be enjoyed.
  • alexandria, va
  • 92 K75s, 94 K75s, 96 K1100RS SE (custodian), 09 K1300s
Marshall
Project Thread "K75s Midlife Refresh"
http://www.motobrick.com/index.php/topic,7810.0.html

Offline Rcgreaves

  • ^ SuperNatural Motobricker
  • Posts: 593
Turns out my rear shock is a Wilber’s with 46 46 50 220 spring installed.  Nice Geeeerman unit..

The tech at Beemer bone yard says that’s a spring for a 300# load.  So for one up riding that’s a bit stiffer than optimal and two up I would want to dial in some preload.

The 50 translates to 286# to compress one inch.  I weigh 203#

So my plan for the rear is to set sag to 1 1/4” and off the damping dial all the way 25 clicks counter- clockwise and see how she feels at different settings.  Maybe low mid high..

Wilber’s suggests rebuild every 12k miles - age unknown-  maybe I’ll have them look it over this winter. A softer rate spring could impact my wobbles.  Cheers.
  • Livingston, SW WI. USA-"With the good earth all around."
  • NEW 1995 K1100RS Red,1994 K75S Red,1985 GL1200A Goldwing Aspencade, dreaming of adding a sidecar to the mix in 2019
Doing “better than I deserve”

Offline mlytle

  • ^ Quintessential Motobricker
  • Posts: 1063
good stuff for the rear.   you can get a lighter spring for it if needed.

check your front springs too.  the front shock oil weight can also be changed to affect damping.  when was it last changed?
  • alexandria, va
  • 92 K75s, 94 K75s, 96 K1100RS SE (custodian), 09 K1300s
Marshall
Project Thread "K75s Midlife Refresh"
http://www.motobrick.com/index.php/topic,7810.0.html

Offline stokester

  • ^ SuperNatural Motobricker
  • Posts: 578
front springs...
-Progressive brand popular, but they are one rate fits all.  i had them.  unimpressed.  ditched them for...
-Race tech, much better.  you get a spring rate that is "fitted" to your usage and weight.  not everyone is the same. https://www.racetech.com/ProductSearch/2/BMW/K75%20C-S-RT/1992-95
I've got Race Tech in my '93 which were installed by the original owner so I don't have a good comparison but during an Airhead Tech session with Tom Cutter at the MOA National Rally he did not have kind words for the Progressive fork springs.  I know this was regarding Airheads but he left me believing they made a basic fork spring and sold it for many motorcycles without regard for its ride characteristics.

The '94 will probably get a set of Race Techs this next year as well as a YSS rear from Ted.
  • Yorktown, Virginia
  • '94 K75S Dakar Yellow - '93 K75S Seiden Blau - '91 R100RT Dark Blue- '78 R100S Smoke Red

Offline Rcgreaves

  • ^ SuperNatural Motobricker
  • Posts: 593
So with the threaded washers dialed all the way back I got the 1 1/4 inch sag recommended when I add my body weight..  A bonus is both feet now touch solidly where til now my 29” inseam has been a “tapping act”. I have yet to install my oem low seat.  I’m liking this!   

So dialed all the way off - (counter clockwise 25 clicks) on the damping wheel -crossing a bridge bump gives two noticeable rebound bounced. My butt says one on same bridge is a suitable benchmark.  Cornering and wobble characteristics are the same.  BBoneyard tech suggested 28 and 30 pressures for solo so I’ll soften tire pressures to that for today’s commute. 

Overnight I spent time really standing on the front binders;; I’m satisfied with the damping/ weight transfer etc.  I’m really hoping fresh bearings-races in the triple tree and fresh damper grease will yield some noticeable reduction in cornering wobble. 

August Is just so “yee Haa” as Johnny says I think I’ll await snow fall before I lay up this bike.  I pose 400 miles a week commuting isn’t great for whatever is causing this shake, this is no museum piece right?  I was praying that change in  rear geometry might help.  No joy.  As always guys I appreciate and value your replies.
  • Livingston, SW WI. USA-"With the good earth all around."
  • NEW 1995 K1100RS Red,1994 K75S Red,1985 GL1200A Goldwing Aspencade, dreaming of adding a sidecar to the mix in 2019
Doing “better than I deserve”

Offline The Mighty Gryphon

  • ^ Quintessential Motobricker
  • Posts: 4596
  BBoneyard tech suggested 28 and 30 pressures for solo so I’ll soften tire pressures to that for today’s commute. 

Sounds a bit low.  Scary, squirmy low.  Factory spec and general consensus is 36-38 front, 40-42 rear.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '91K100RS White/Blue, '89 K100RS Special edition White/Blue
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'91 K100RS "Moby Brick Too
'89 K100RS SE

Offline Filmcamera

  • ^ Quintessential Motobricker
  • Posts: 1333
28 - 30 is fine if you are going to be doing track riding on it but for street you are unlikely to get it warm enough to expand enough for those pressures to be ok.
  • San Jose, Costa Rica
  • 1991 K100RS 16v ABS1, 2018 Triumph Street Triple RS 765
Poserbricker

Offline mlytle

  • ^ Quintessential Motobricker
  • Posts: 1063
agree with both of the above.  those pressures way low and will contribute even worse handling.
  • alexandria, va
  • 92 K75s, 94 K75s, 96 K1100RS SE (custodian), 09 K1300s
Marshall
Project Thread "K75s Midlife Refresh"
http://www.motobrick.com/index.php/topic,7810.0.html

Offline stokester

  • ^ SuperNatural Motobricker
  • Posts: 578
Sounds a bit low.  Scary, squirmy low.  Factory spec and general consensus is 36-38 front, 40-42 rear.
Yup, I usually run 37 and 40.
  • Yorktown, Virginia
  • '94 K75S Dakar Yellow - '93 K75S Seiden Blau - '91 R100RT Dark Blue- '78 R100S Smoke Red

Offline The Mighty Gryphon

  • ^ Quintessential Motobricker
  • Posts: 4596
I wonder if those tire pressure recommendations is how Beemer Boneyard gets their parts bikes.
  • In my garage in Marilla, NY
  • '94 K75RT Mystic Red, '91K100RS White/Blue, '89 K100RS Special edition White/Blue
Current:
'94 K75RT "Ilsa, She Wolf of the SS"
'91 K100RS "Moby Brick Too
'89 K100RS SE

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