I already knew that you can run a 110/80-18 front on the 2.5x18 front but given the wheel/tire sizes I was never sure what radial you could put on 2.75x17 Y-spoke rear wheel.  Was lurking over at the MOA forum recently and noticed that someone is running an Avon AV46 140/80-17 on a Y-spoke rear.  Hmmm....  Did some Googling on what are allowable tire sizes for various rim sizes and, sure enough, that tire size is OK for that wheel size.

And, just for grins, here's how they compare to the stock bias ply tire sizes:

A 110/80-18 is about 0.6% smaller in circumference and diameter than a 100/90-18. 

A 140/80-17 is about 1.5% smaller than a 130/90-17.

If I were putting new tires on a non-drum K75/K100 with Y spoke wheels I'd go with a Bridgestone BT-023 front and Avon AV46 rear. (That's what I run on my K75s with 3-spoke wheels and they handle quite well.)

I was thinking of buying 2nd hand k1100 3 spoke wheels front and back & putting on avon radials 110 & 140 on my 89 k100lt
Apparently this should work without issues. Could someone confirm this for me please?
Colin

Colin:

I believe the Avon AV55 Storm 2 on the front and the Avon AV46 rear has been documented as working on either this cite or on of the others.

I can understand wanting to keep the purchase in the country, and you are limited to the Avon for the rear if you are looking for a road-only radial.

I have Avon Road Runners on my RD350 over Bridgestone BT-45's that a lot of others recommend on them.

You may want to to a search for a comparison between the Bridgestone and Avon for the front. 

There is probably a good reason this guy suggested a non-Avon for the front:

http://www.motobrick.com/index.php?topic=2241.msg12166#msg12166

Addendum:

For people that spend a lot of time commuting/highways instead of twisties and racetracks the author of the post cited chooses to use dual compound tires that last a lot longer, which rules out the Avon on the front.  Can't say I blame him.

colinijohnson wrote:I was thinking of buying 2nd hand k1100 3 spoke wheels front and back & putting on avon radials 110 & 140 on my 89 k100lt
Apparently this should work without issues. Could someone confirm this for me please?
Colin

If you want to install a K1100LT front wheel then the only sane way to do it is to replace the whole front end - brakes, master cylinder, fork trees, forks.....  LOTS of parts involved.

Why not get a K75/K100 3 spoke front wheel?  

The 3x17 K1100LT rear wheel is the same 3 spoke used on earlier K100s:

http://www.realoem.com/bmw/partxref.do?part=36312311149

and it "bolts right up" with no need to worry about the center stand or swing arm clearance.

Hi there, my k100rs has the three spoke rims, 2.5 wide at front and 3.0 at rear.
I´m using a Dunlop K505 110/80 at the front end (Used to be a D205 but is no longer available), and this seems to be the limit due to interference with the forks and braking components.
At the rear I´ve used Dunlopd D205 140/80 with no issues during 1400kmts. .
I´m currently running  a D205 150/70, have done near 7000kmt with no issues but with a very tight fit. Be aware that this is out the range of rim wide recomended by dunlop.
Hope this helps.
Best regards
JAP

You are picking the right time of the year to start a conversion like this, Colin.
As duck says, you need the complete front end including top and bottom yokes (trees). You could look for a 3 spoke K100/75 front wheel but they are as rare as rocking horse poo.
I had collected just about all of the necessary parts needed and then the sun came out. Rather spend my time riding than tinkering during the warm weather.
Some say the answer is to have more than one K...
The wider RS(16v) rim will fit straight in but you do need to either throw away the centre stand or replace with the RS item.
The other thing to bear in mind is that if you still have ABS on your LT, it may not be compatible with the sensor on the 16v front wheel. I reckoned it should be as there is only one tooth difference on the ABS ring but you are in unknown territory and it may be necessary to scrap it if it didn't work.
If you take a look on the old threads you should find plenty of info about the conversion.

It is possible to get ABS running with a K1100LT front wheel.  I have that working on my K75 Frankenbrick.

I'm not sure if this is the only approach but here's how I went about it:

K1100 ABS I control unit. All of the pin-outs for both control units are the same except that the power comes in on Pin 15 for a K75/K100 but it comes in on Pin 16 for the K1100 control unit.  I took the wiring harness connector apart and moved the green power wire from 15 to 16.

K1100LT front wheel and ABS sensor.

The rear modulators are the same but the front one is different (somehow?) so I used one from a K1100 ABS I bike.  The pipe threads for the K75 modulator are both 10mm.  On a K1100 front modulator one is 10mm and one is 12mm. I was not able to find a suitable adapter so I cut a 12mm connector off of a K1100 brake line and was lucky to find a guy at a local brake shop who had the know-how and tools to install it on the end of the K75 metal brake line.

By the way, I am comfortable riding both ABS and non-ABS bikes.  I did this mostly for the challenge of seeing if it could be done.

I have Michelin A48 100/90-18 in front, and Michelin M48E 120/90-17 rear.
Good sticky tyres, also on wet, grass and sand.

G'day All , my last set of tyres where Avons , Storm on the front with an Azaro on the rear , 110/80/18 front , 140/80/17 rear , fitted to a 2.5 inch three spoke front and a 3.0 inch three spoke rear , in my 33 years of riding I have never had a worse tyre on the rear , the super aggressive tread of the rear made the bike "walk" side to side as the wheel rotated , at slow speeds ( < 40kmh ) say traffic filtering speed you could feel it wobbling side to side , at higher speed it translated to a vibration , I had the tyre remounted twice to no avail , I put up with it until the tyre did the honourable thing and delaminated itself ( never had this happen before either ) , I'd look elsewhere if you are considering an Avon Azaro , I've now just completed the "big" wheel upgrade and am now running Michelin Pilot Road 3's ( 160/60/18 ) on a 4.5x18 inch rim

JR

When my bike was delievered it was shod with Michelin A48 / M48 back in 1987 , how old are those tyres Wheeldigger ? , they must be as hard as a rock !

JR

Surprisingly soft, and still in good condition, and very very much better than the Metzelers before.
Don't know where they came from, they were on the white K75RT when I bought it some months ago.
The white one needs an overhauling, so changed the wheels with tyres to my daily green one.
The Metzelers were iceskating without skates, altough 1 year old and looking like new.

I'm very surprised to hear you don't like the AV46.  I've run them on several different Ks (K1100LT, K100 and K75) and have been quite happy with them.  I get pretty far leaned over on turns when I ride and they feel very "planted" and solid. I've never felt any quirky behavior from them at any speed - be it fully loaded up on the K1100LT or riding solo on a K75. There's also quite a few riders over on the K1100LT forum who run the AV46 rear and are quite happy with it.

What tire pressure are you running it at?  I run mine at 42 psi.

Comberjohn wrote:You could look for a 3 spoke K100/75 front wheel but they are as rare as rocking horse poo.

I was fortunate enough to find a set from a wrecker in PA and will retrofit my 85RT. :pirat: 

The above noted post from Motorbrick refers to 93K75S with the same 3-spoke wheels (not Y wheels).

Am still a newbie about what tires to use on these "narrow" 3-spoke rims, so thanks for your comments. Perhaps we need a separate thread for this subject as people are looking here for information on the "Y" rims.

G'day Duck , yup ditto , 38/39 front & 42 psi for the Azaro rear , maybe I got a bad one ? , it balanced up ok , minimum weights required , the rim was straight & true as well , spooky tyres

JR

The issue with comparing tyre performance around the world is that road surface construction varies as does the condition of the surface owing to climate and usage.

M48, A48 combo, My first RS had these on as delivered in 1985, 13th September, Friday.
New bike, new rider to biggish bikes. I had to ride bike, in the pissing down, to the next state on dealer plates to get the rego. I swear it rained every time I rode that bike (I broke the drought), so much so that I rode faster in the wet than the dry on those Michies. 
I totally was displeased with the ME33, 2,300km, Then settled on the Dunlop duo of K701F 110/80-18 140/80-17 that I ran for a number of years. Probably the sticky tyre for the front was a TT100 Dunlop 90/90-18, I remember tyres from the past with melancholy......
On the spare K I have run the BT45 thing, and the some Italian option tyres, and was still looking for a good combo.
The 'new' K has a Arrowmax 501F on the front and a Lazertech on the rear, but I would like to have radial tyres. Azaro and Storm, Has anyone found these in Australia?

G'day Richarde1605 , scroll up to post number 9 , Avon Storm & Azaro were my last set of tyres

JR

But, where did you get them? Some tyres suit different folk, I just want options, not all that happy with bt45's or demons, but if that's all there is?

Looks like another wheel job.........

Yokahama also made a fitment back then, they were sticky, but also gone....

G'day Richarde1605 , got my Avon's from a local tyre shop ( Pablo's ) , take a look at www.proaccessories.com.au , or call them on 0732770675 , they are the importers into Australia for Avon

JR

I'm getting real cheap Metzeler ME880 140/80/17 rear tyre and was wondering is that OK for 2,75" Y-spoke. According to this thread it seems to be. Right?

Edit:

How does tyre size change in this case affect on speedo and does it affect on ABS - standard rim.

It will have no effect on the ABS, but will affect the speedo. Speedos are inaccurate anyway and it is wise to check yours against a GPS sometimes.

A 140 x 80 x 17 is very close to the same diameter as a 130 x 90 x 17. I think it is marginally smaller in circumference but so small as to not be worth the trouble to do anything about it.
I have run both and could not pick the difference with the speedo/tacho readings.

A 140/80 would have a tyre wall height of 140mm - 20% = 112mm. The 130/90 would be 130mm - 10% = 117mm. So overall there would be about 10mm difference in diameter (5mm top and 5mm bottom). You would hardly notice that at all. You would find that different make of tyre could also have different diameters even at the same sizes.

bikerboy wrote:It will have no effect on the ABS, but will affect the speedo. Speedos are inaccurate anyway and it is wise to check yours against a GPS sometimes.

I have noticed this. My bike's speedo says 90km/h when real speed is about 80km/h or even less. Will it go worse or better? 

And thank you all. Only 100 euros for that tyre and K100 stock exhaust pipes (no muffler). + shipping. I think that price is OK.

Smaller diameter wheel/tyre speedo reads higher larger diameter it reads lower, but don't get hung up on it as new tyres are a larger diameter than worn tyres.

Look at it differently - for the same speedo speed (which relates to a revolution of the rear wheel) the faster you go with a larger diameter wheel/tire.  So if your speedo shows a speed higher than real the tire is too small. You could of course also adjust the speedo for the tires you want to use :-)

"You could of course also adjust the speedo for the tires you want to use :-)"
But would you adjust it for a new tyre or a worn tyre? Either way it will not stay accurate. Not worth the effort when a small GPS will give you your true speed.

I don't believe there is a BMW speedometer ever made that is accurate when installed.  Everyone of my friends BMW's both 2 wheel and 4 wheel along with my  99 323i, 07 325i, 10 128i and K75 all run between 3 and 5 mph faster than actual. Choices are; You either adjust the speedo using a gps, or use a GPS to determine your particular amount of error and calculate speed by the tach or just run with a gps.   Using any of these methods you can adjust for any change in tire size.

Most speedos have an error which makes them read a bit fast. I have never come across a speedo that is accurate through the whole range. A dial type as is on a K will always have usually have a point where it reads correct.
We all learn fairly quickly what the error is and drive accordingly.
A digital readout is the most consistent but they usually also read high.
Here in Australia we have a rule that states that a speedo can't read low and no more than 10% high so that most of the manufacturers set the speed to read somewhere in the 6-7kph high and most of us know that and set our speeds accordingly.

I'm not adjusting anything, just going to check the real speed vs. speedo and try to remember how fast I can go.  

Which made me think of completetly other issue, but I ask it anyway in here if you don't mind.

Is there a speed limit given from BMW when driving with original side bags?

Yes, it can be found in the owners manual.

Tenox wrote:Is there a speed limit given from BMW when driving with original side bags?

130 km/h, if I don't remember wrong.

Ok thanks. My manual is written in germany which I don't understand. Good to know..

Confirmed: max 130 km/h / max 10 kg in each pannier.

I put Givi panniers on mine so I can go as fast as I like 

Hush, Rick, you're on a BMW forum....

Inge K. wrote:Confirmed: max 130 km/h / max 10 kg in each pannier.

Guess mine don't know  

Inge K. wrote:Hush, Rick, you're on a BMW forum....

Oops got a bit carried away then. I really only ever travel at a very safe speed and obey all the road rules.

I have ridden legally at 230kmh with panniers and topbox fitted (and a dog on the tank).  The bike showed no signs of instability at all.

It was purely an exercise to find out how much fuel I could use in a short time. It wasnt a BMW though.

Al

Anybody has experience with a 150/70 on the rear? There are some options that might be interesting (radials). Where could you find if it would fit the rim (old Y wheels)? Thinking of Pirelli Angel GT's.

ReneZ wrote:Anybody has experience with a 150/70 on the rear? There are some options that might be interesting (radials). Where could you find if it would fit the rim (old Y wheels)? Thinking of Pirelli Angel GT's.

Tyre is too wide for the rim (2.75) 140/80 is max.

http://www.c-note.dk/wordpress/wp-content/uploads/2013/12/Motorcycle_Rim_Width_Tire_Size_Chart.pdf

Al