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Discussion in 'GS Boxers' started by jaystonewee, Feb 15, 2019.
Well that's a big help! Thanks, had no idea I can actually use the R/RS/RT axle on the Gs forks.
As I was contemplating the conversion earlier this year, I wanted to keep the front R/RS/RT wheel/axle the same type (considering wheel bearings, spacers, seals etc etc) over getting GS axle modified to suit R/RS/RT wheel. No right or wrong way - those are some of the alternatives to consider and pick what works for you best...
Found a set of wheels finally! Still waiting on the new front axle and the rear wheel to show up. Can't wait to get these thrown on!
good day, since i have done the conversion myself. Just a few hints before you get frustrated ...
1. You can run the original brake disks, but you will need a 2mm Spacer under the Caliper you will notice why when you assemble the front
2. You do not need any adapters from Rennkuh, you exchange the bearing from the standard RS dimension to GS bearings and you can continue to use the GS Axle
3. You need to machine material off the rear wheel and center ring otherwise you have clearance issues with the exhaust. Its something between 3.5 - 4 mm
4. You will need custom rear bolts to match your machined rear wheel
5. You can use a mud guard from the S1000RR with some adapters.
because of #1 its better to run also 320mm brake disks of the RS, for that also a spacer is required.
Next problem is because of the different wheel size the ABS and Tractioncontrol get confused. It will engage too early, therefore an adopted ABS Sensor ring is also needed. This will also avoid the ECU error stored if not done. There is no one size fits all you will need something between 44 and 46 instead of the original 48 ABS Sensor ring.
Excuse my english since i am German ..
Guten Morgen - Your English is just fine and welcome to the 17" conversion camp-fire...
Couple of comments to your hints:
- your suggestion to replace bearings ie. spacers from inside the wheel hub is valid but that's too much labor from my pov - using RS axle and matching LH RS spacer takes care of that in no time and no sweat...
- originally I didn't machine any material off of mounting flange of a rear wheel, when I first installed rear RS wheel with original GS bolts to try it out as-is. As it didn't cause any issues, I kept it the way it was, just spaced out slip-on at mounting point until it cleared rear tire with a clearance;
- further more, if you take a look at actual rear wheel offset btw GS rear wheel (4.5"), RS wider wheel (5.5"), and then compare actual RS wheel offset to a theoretical offset for 5.5" wide wheel (based on OE 4.5"), you'll see that there's no more than +1.5mm difference (wheel mounted outwards toward slip-on). By machining ~4mm off of the flange, you'd be changing that offset to -2.5mm the other way, away from slip-on. Although an option, I didn't find it necessary as that irreversible change turns into snow-balling effect of changing bolts etc - ymmv (your mileage may vary)…
- both RS and GS front wheels use same ABS ring w 48 slots (same p#) so no changes are needed there either as far as I see it. As you stated that there's something else needed, w 44-46 slots, what did you use and why ie. where did that "calculation" come from?? I'm sincerely curious - please share...
I have done this twice on a 1200GS and my 1250GS for both there was no way get enough clearance. Yes you can space out the silencer, but this puts stress on the header.
Your math regarding the offset is not correct. When i will find more time i can explain it in more detail.
The ABS and traction control is based on the wheel circumference. For the rear there is only a minimal change but if you calculate the difference between a 19 inch and a 17 inch tyre there is a difference. The ECU will notice that and log first of all an error code. Secondly it causes as i wrote the traction control to engage way to early. The RS and GS have the same ABS Ring, thats true, but the wheel size is stored as a parameter in the ECU and used by the ABS and Traction Control. I had no way to reprogram this so far.
So to compensate the difference if you calculate this you get to 44.XX slots. I still had too early Traction Control kick in with that, so we ended up with 46 slots which seems to work fine.
However the Speed Control display speed is slightly off with that. The real speed value is taken from the rear sensor and correct no matter what you use at the front.
I hope this is understandable ...
1. Well, with approx. 8000mi on my spaced out slip-on, my headers are still the way they were first day so I'm not sure what stresses I put on them, if any, but they're surviving a-ok. Beside, I don't believe that spacing slip-on out makes any difference what-so-ever on headers nor it introduces any stresses to them...
2. It's possible that my math is all wrong but that's unlikely... Looking forward to your math and how you concluded that 4mm is right offset for rear wheel!
3. It's possible as well but I haven't experienced the issues that you have...
4. Where did 46 slots ABS ring come from ie. which bike? Or, you laser cut one?? I wouldn't mess with ABS ring myself which is why I kept OE style...
ABS Ring is from a local Lasercutter, if anybody needs the DXF file for personal use i am happy to provide it ..
These are the values for the different RIM's i received :
GS K50 : 4.5 x 17 ET -32.5 with 170/60 R17
RX LC K5x : 5.5 x 17 ET -46.5 with 180/55 R17
if you run that through any Rim calculator you get :
Towards exhaust +27mm and -1mm towards swingarm
question is of course if the ET values are correct
I'm not familiar with Rim calculator but am more than familiar with different offset wheels and how they do or not fit my application - there is universal offset (ET) formula that I've used which never failed me... The ETs that you quoted are correct GS/RS ETs for OE wheels respectively, but that rim calculator may be where you got hung up sideways...
Otoh, if your rim calculator tells you -1mm towards the swingarm and you took 4mm off, how is that right then??
Moot point anyway, you machined that off of your rear wheel and that's done and irreversible deal - can't go back...
GL with your set-up, both rear wheel offset and new ABS ring...
So after all that, how does the bike feel?
Found one in english which gives the same results than i quoted before
The reason to machine off, is basically
1. Clearance which you resolved by spacing out the silencer
2. Minimize the offset error between the front and rear weel
Now for point 2 we can continue to calc the alignment error between front and rear which is still there, but you can not machine more material off the rim to get a perfect alignment. The reason is just to get it as perfekt as possible. You can even use a K1200 6.0 series rim which will from an ET perspective be a better fit, but this only works with a header modification.
We have several companies offering 17 Inch conversion kits where there is no offset between front and rear, but this is much more expensive than the RS diy solution ..
I would like the DXF file for the ABS sensor ring please, found the stored fault when switching back to wire wheels about a month ago. Bike rides fine and I never noticed any problems with the traction control despite the wheel diameter difference. Doesn't do any good to have traction control and ABS if the systems are compromised, even a little.
Tried contacting rennkuh recently and was met with some tragic news. Michael’s sister has informed me that her brother has passed away. They are not sure whether they will continue running the shop. RIP
That's really sad to hear...
Hope they'd find the way to continue where Michael left off - there was value in what they were offering as one-stop-shop for those wanting turn key 17" conversion...