HELP! 
I need to replace both tyres on my 85 K100RT renovation as they are both past their use by date......the current tyres are 100/90-18 front and 130/90-17 rear. 
The trouble is I don't understand what tyre size options can be fitted ......such as can I fit a 110/80-18 instead of the 100/90-18 as the choice of tyres available in the original sizes seems a bit limited I.e.  Battlax BT45's or Pilot Actives. 
What are the pros and cons of upgrading to 3 spoke wheels?

The tyre fanatics will be along shortly to tell you what others will fit, including a few radials.
I've used both BT45's and Pilots and found both perfectly adequate, with better mileage from the Pilots.
You can upgrade to the three spokes from the 16v RS. The LT uses the same rim size as the 8v, so not much point.
Rear wheel is a straight swap but you'll need the complete front end, including brakes and yokes, for the front wheel.
Need the RS centre stand, too.

I've found this chart handy:

http://www.mtsac.edu/~cliff/storage/gs/Motorcycle_Rim_Width_Tire_Size_Chart.pdf

Three spoke wheels are wider -- 3.00 vs. 2.50 for the front and 3.50 vs. 3.00 for the rear. Wider rims gives more tire options, especially on radials which improve the bike handling immensely.

There are 6 versions of 3 spoke wheels.
K75s has front 2.5" x 18 and rear 3" x 17 The front will take the std K100 type discs and the rear fits the monolever rear drive i.e. it sits centre.
K100RS 16v and K1100RS 3.5" x 17 front and 4.5" x 18 rear The front has the 305mm disc (floating type) and fits the 41.7mm forks which only came on the 16v bikes. Rear is designed to fit the paralever drive and will fit on the monolever but sits 14mm to the left.
K1100LT Front 2.5" x 18 and rear 3" x 17 Front takes the 305mm discs and the rear is designed to fit the paralever drive and will fit on the monolever but sits 14mm to the left.
If you want 3 spoke on a K100 8v for looks the easy way is use the K75s wheels if you can find a set.
If you want to fit the wider radials then you need the K100 16v or K1100RS wheels with the complete front end and paralever rear drive which allows the rear wheel to be centred.
There are many ways to have combinations most of which requires some making of parts.

A simple option on tyre size on the standard Y spoke wheels is to use a 110/80-18 front and a 140/80-17 rear. These fit, clear everything, and in most cases give a slightly better, more planted 'feel' over the road. I prefer the bias ply but radial-like Pirelli Sport Demon over the Michelin Pilot Activ or the Bridgestone Battlax BT45. Results may vary.

For radials on bog standard Y spoke wheels, try a Bridgie BT023 front in 110/80ZR18 and an Avon Azaro in a 140/80ZR17.

AFAIK the BT023 has been superceded by the T30 which looks to be a better tyre and a little cheaper too . Finding a size for the rear may still be a problem but it is available in 150/70ZR-17. I think it would fit??? I have the Azaro45 rear and there's still a tight finger width clearance.

It's true that T30 replaces BT021, 022 & 023, and is a better compound (dual), but since the 023 didn't sell in volume there are piles of them left. That alone might get you a deal if you enquire. It is a good tyre, regardless.

Don't try to squeeze a 150/70 tyre where a 130/90 or 140/80 are meant to go.

robmack wrote:I've found this chart handy:

http://www.mtsac.edu/~cliff/storage/gs/Motorcycle_Rim_Width_Tire_Size_Chart.pdf

Thanks Rob,
That's a very useful chart.

Paul.

100 and 140   bts on mine.

Both good fit.

Two Wheels Better wrote:It's true that T30 replaces BT021, 022 & 023, and is a better compound (dual), but since the 023 didn't sell in volume there are piles of them left. That alone might get you a deal if you enquire. It is a good tyre, regardless.

Don't try to squeeze a 150/70 tyre where a 130/90 or 140/80 are meant to go.

You're right, the rim is a B's D too small.

I have the 023 on the front and I certainly can't complain. Performance is outstanding.
It was just a thought because I'll be up for a new rear in 2 or 3 months and I thought of maybe getting something to match but I have to say the BT023/Azaro45 combo is good.

One downside is that the Avon Azaro 45 has only done just under 6,000klm and I'm down to 3.5mm already.

Thanks for all the explanations and recommendations; I now understand tyre/wheel ratios a bit better.

I have searched local suppliers and some tyres recommended are not available to me in the UK so it looks like I'll go with Bridgestone BT45s front and rear as I can get 130/90-18 front and 130/90-17 or 140/80-17 rear fairly easily and the prices are reasonable.

Thanks to all

Aladin


I have used the BT45 quite a bit and very happy with them.

The last time I changed the rear I went from 130/90 to 140/80 and I prefer it. The one thing I have done is that where there are different speed ratings I have gone for the lower rating due to riding all year. Realistically a K will not do over 130mph so you don't need a tyre rated for that speed. The lower rating is slightly softer and in winter will be of help. The difference is probably marginal but having used both ratings I have noticed the difference in winter riding in icy conditions.

When I got the rear tyre on it was wet and on the way back from the Honda dealer [located beside the local BMW dealer] the first few miles felt like the tyre had grease on it. Scrub carefully.....

Olaf

That's really helpful advice especially with regard to speed ratings. 

I am not a fast rider anyway preferring to ride in the 60-70mph range even when I have a clear road ahead of me. I was thinking of going to 140/80 rear so Thanks for the feedback on your experience. Not only am I a steady eddy rider but also a confirmed fair weather rider (purely recreational)..........not a proper biker I hear some of our colleagues groaning..........but we all enjoy our Ks in different ways.

We both share similar weather so do you think the lower speed rated tyres will be better for our 'summer' wet and dry weather?

Hi,

4 me the Pirelli Sport Demon run Perfectly

Lighter...Faster...detailed road reading

Last less than competitor, but have Better Grip and increases confidence...

K 100 1986...Titanium... love them


Cheers

Aladin

As you say similar weather. I have always stayed at a lower speed rating if I can help it, simply because it can mean you are in the optimum for a particular tyre. It is more noticeable in winter but on a day like we have here with blue sky and sunshine probably very little difference. Its not that I get scared in the wet, I don't and quite happily go out in rain or snow and love the feel of the bike in those conditions when you feel good tyres doing their job well. On the bike in low temperatures on wet roads an older or high speed rating tyre will take its time to warm up and I live on a bad road so had a chance to compare quite a few in winter conditions. If you are generally under the 70mph you wont be putting too much stress on the tyres.

Summer wet weather after a long dry spell is the most risky in my book.  Old rubber, diesel etc on the road acts as a lubricant and you skid easily and can get caught by surprise no matter what you are on.

Busas wrote:Hi,

4 me the Pirelli Sport Demon run Perfectly

Lighter...Faster...detailed road reading

Last less than competitor, but have Better Grip and increases confidence...

K 100 1986...Titanium... love them


Cheers

100% agreement! The Pirelli Sport Demon is the best radial-like bias ply tyre for K bikes.

Busas wrote:Hi,

4 me the Pirelli Sport Demon run Perfectly

Lighter...Faster...detailed road reading

Busas, what size do you have on the rear?

Personally I'm not too fussed about tyre speed ratings, but be aware that insurance companies will always look for a 'get-out' clause, so a bike with lower than specified speed rated tyres could be a problem...........even though we aren't allowed to go over 70 mph. 

Paul.

sidecar paul wrote:Personally I'm not too fussed about tyre speed ratings, but be aware that insurance companies will always look for a 'get-out' clause, so a bike with lower than specified speed rated tyres could be a problem...........even though we aren't allowed to go over 70 mph. 

Paul.

Paul

I thought that could be a problem too, it came up on the car when it went for our MOT. Tester said that provided the tyre ratings met the requirements of either the maximum speed of the car or the legal maximum speed limit they would pass it which they did. [Interesting he also said that if the sizes did not match manufacturer or rim sizes they would not pass. Something to remember if using oversize tyres]. But therein lies a problem if you then take that same car/bike to Germany and NO speed limit, or to say France where the speed limit is 130 or about 80mph. It does seem like manufacturers specify ratings for speeds a vehicle cant actually reach. I eventually got a handbook last week and it lists a V rating for the tyres on the K, for speeds above 130mph, which a K100 can barely achieve.

The BT45 comes in H and V ratings both of which are safe on a K.

I suppose the whole debate demonstrates that most riders take their tyres very seriously which has to be good.

B: 50kph 31mph
C: 60kph 37mph
D: 65 kph 40mph
E: 70 kph 43 mph
F: 80 kph 50mph
G: 90kph 56mph
J: 100kph 62mph
K: 110kph 68mph
L: 120kph 75mph
M: 130kph 81mph
N: 140kph 87mph
P: 150kph 93mph
Q: 160kph 99mph
R: 170kph 106mph
S: 180kph 112mph
T: 190kph 118mph
U: 200kph 124mph
H: 210kph 130mph
V: 240kph 149mph

Rather than MOT testers, I was thinking of insurance companies inspecting a vehicle after a claim.

So your tester would pass a Hyabusa with a 'L' rated tyre? (for use in countries with a 70 mph limit)  

Paul.

Paul

You are very correct with that. I wasn't quite thinking of going back as far as an L rating,  at least we cant get such low ratings here. And if it was a serious personal injury claim then yes the insurance will try to use the tyres as a get out. And I would agree an L rating would certainly get them a long way off the hook.

These days you'll be lucky to find an H rating. Most 'big bike' tyres start at V... something to do with reducing manufacturing costs.