Spacer(s) for 17" rear wheel on R1100RT?

[DavidEBSmith]

So I got the bike back from the final pre-Iron Butt Rally service and mounted the 17" K12 rear wheel (with bias ME880) in place of the stock 18" rear wheel. One of the first things I noticed is that the 17" wheel and tire come much closer to the swingarm than the 18" wheel and tire. With the 18" wheel, there's about a 1 1/2 fingers space, with the 17" wheel there's about a 1 finger space.

 

To give a little extra clearance, and since I had them in the garage, I put on two of the spacers that go between the wheel and the hub. The spacers are 2 mm thick, so it's not a whole lot more clearance.

 

What has everybody else done that has put the 17" K bike rear wheel on an Oilhead? Ignore the clearance issue? Add spacers?

 

And now that I think about it, I'm using the K-bike lug bolts, which are 5 mm shorter than the R-bike lug bolts. Will they now be too short with the added spacer? But wouldn't the R-bike bolts be too long?

[Rocketman51]

Hi, I have a K1200LT rear rim on my 97 RT. That is a 17" rim. Now I used the stock bolts and one spacer. I would expect the tire to be closer than the stock rim to the swing arm, as the LT rim is 5" wide. The stock rim is, I believe 4.65" wide. Now I am 300 miles from the rims, so I can not measure them for you. With some help, get a couple of 8' streight 2 x 4's, and put on each side of rear rim, and see if your front rim is in the middle of the 2 x 4's. This is going to require more than 2 hands, and finding streight pieces of wood. Anyway, i did this and mine was very close to the center line. Good Luck

[fatbob]

David:

I ran mine with one spacer and the LT bolts, cause I think the RT bolts would bottom out on the hub with the LT wheel. I believe that your new tire / wheel is wider than the 18", so your tire will be closer to the swing arm.

 

Bob

[Jay B]

I have a KRS rim I run with an 880 once in a while. I just use the stock RT bolts and single spacer. Must work, as I have put about 15k on this wheel, and it hasn't fallen off even once!

[Paul Mihalka]

For many-many miles I used on my '99 R1100RT the K-LT/RS wheel (they are the same if 5") and bias 160/70x17 ME880 tires. As stated, with the wider wheel the tire is pushed out some. I used NO spacer and used the K wheel bolts. Even with one spacer I would use the K bolts as that is the way they are on the K bikes. Adding spacers will increase PTTR, messing up your front tire wear as it produces left side scalloping.

[bmwmick]

David,

I'm using a K-RS 5" rear wheel with one spacer and the shorter K-Bike lug bolts. It is very slightly closer to the swingarm but I can still get a full finger in there. Love my 880's!! I don't think you need the second spacer.

160X70X17 Bias-Ply rear. 120X70X17 Bias-Ply front.

 

Mick

[DavidEBSmith]

OK, for you guys using the bias-ply ME880s, what do you have for tire pressure? I set mine to 40F / 45 R as a start (the bike is really, really heavily loaded) and the ride is really, really harsh. The sidewall says 42 max front, 50 max rear.

[Paul Mihalka]

I used 38/42. Probably less loaded than you are. The ride is harsh compared to radials. It is the only downside I found.

[bmwmick]

38/40 f/r

I tried 40/42 like I normally carried in the radials but it was a bit too rough. I think unloaded I could even drop them to 36/38 because of the sidewalls on these reinforced tires are REALLY strong. That contributes to the harsh ride......but you knew that.

 

Mick

[AndyS]

Just a casually curious question - what spacers are you talking about?

Surely, if you are talking about the disc that goes between the wheel and the drive housing - you may get more/less clearance between the swinging arm, but the front and rear wheels will no longer be in-line!

 

AndyS

[ShovelStrokeEd]

Andy,

They are not in line to start with.

 

A few mm should do it and you can build that up from the factory spacer set.

 

I did not read the rest of the thread but if the wheel is from a later RT it should have the proper offset built in and not require any additional spacers. This may also be true with the wheel from a KRS.

 

You can verify with a straight edge and a scale. Just set the straight edge across the right side wheel flange and measure down to the drive flange. A scale will give sufficient accuracy for this comparison. So long as the dimensions are the same or nearly so between the 18 and 17" wheels all should be well.

[DavidEBSmith]

The wheel is a 5" wheel from a K12RS/LT, so it's probably not the same offset as the RT wheel.

 

Actually, now that I've test-ridden the bike, the issue isn't so much the spacer as the bias-ply ME880s. The Works shocks on my bike are pretty stiff, and combined with the stiffer bias tires, the ride quality ranges from harsh to downright atrocious.

 

I was hoping to use the bias tires for the IBR because the rear tire has much more tread depth than the radials (9 mm vs. 6.5). The idea was to be able to ride the whole rally without changing tires. However, as hard as the bike rides with the bias tires, I'm not sure that it (and I) would hold together for 11,000 miles.

 

Tonight I'll try lowering the pressure on the bias tires and see if that makes a difference in the ride quality. Of course, that will reduce the tire life, so it reduces the advantage over using the radial tires.

 

The fallback strategy is that I've got a radial front and two radial rears mounted on wheels. I can swap the rear wheel & tire at the first checkpoint (5 days), and hope that the front lasts the whole rally.

 

Whatever I do, it'll have to be sorted out by Friday, or not.

[Paul Mihalka]

Are your radials ME880? They last almost as long as the bias 880s.

[DavidEBSmith]

Yeah, it's the "almost" that's the issue. The set of radials I just took off, I measured the tread depth at various points, and I calculated that I would get 9000-10000 miles on the rear. That won't quite do it.

 

Everything I've read about bias vs. radials says that radials have longer life because they handle the heat better. OTOH, the bias rear ME880 has much deeper tread than the radial. People on K12LTs are reporting getting 15K and up on the bias 880s. (Maybe I should just buy a K12LT?)

[Paul Mihalka]

Then you will have to ride like the people who get 15K on the tires

PS On my R1100RT I used the bias 880s combined with Ohlins shocks. The ride was perfectly acceptable. May be the Works don't respond that well to small but harsh bumps.

[DavidEBSmith]

May be the Works don't respond that well to small but harsh bumps.

 

That's always been the one thing I've never been happy with on the Works shocks - they don't respond well to sharp bumps. Things like the narrow frost heaves we get around here, and abrupt pavement transitions, get transmitted as a big bang. Too much compression damping? It's not adjustable on these anyway.

[ShovelStrokeEd]

And therin lies your problem.

 

Too much high speed compression damping.

 

You could send the shock to somebody like Lindeman or even back to Works but I doubt you'd get it back in time at this point.

 

I really think you are way overboard on your tire pressure and that's the source of your problem. Run some pressure rise tests and settle on a pressure that only goes up about 10% after being ridden fully laden.

 

Better yet, take your bike out with a similar load to your IB one. Now ride your bike a good 20 miles and then set your tire pressure to the max recommended by Metzeler. Whatever that turns out to be when things cool back off is where you should run. I'd be surprised it that is much over 40 PSIG or so. Remember the higher pressure is going to make the tire assume a rounder profile and thus reduce contact patch. You will now be concentrating more of the load on less of the tread and may actually reduce wear life.

[DavidEBSmith]

Problem resolved.

 

I lowered the pressure on the bias tires down to a couple of pounds over Metzeler's minimum, then took the bike out on the local torture track (I-94). Still sucked, but less so.

 

So I got to thinking, the handling sucks with higher pressures, with lower pressures I don't know if I'll get the mileage. So I have a more uncomfortable ride with no assurance of getting the mileage benefit. Plus, the front wheel with the bias tire mounted on it has loose brake disk bobbins, which I got and could replace, but that's another evening of work. Not to mention that with the smaller bias tire, I'm running at higher RPMs, and using more gas. Lot of negatives, not many positives.

 

So I put the radials back on and took it for a test ride. Yeah. Rides fine, I can read the GPS because it's not shaking all over the place.

 

So I've got a spare radial rear mounted on a wheel. If I swap that at the first checkpoint, I should be good for the rally. (If I end up needing a front tire, it's a fairly common size and I can probably find one). I can take along my old beam torque wrench and swap that wheel in about 20 minutes (now that I've had lots of practice over the past few days).

 

Nothing like planning ahead.

[BUSTED]

42F/42R if 2 up with gear. Deflate rear for less gear or passenger.