Shovel Jockey
Piano Tuna
Anyone using these tires with success and satisfaction?
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Dunlop K70's/K81's
- Thread starter Shovel Jockey
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Not since the late 70's, was a good tire then, should still be a good tire.
Leo
Leo
yamasarus
XS650 Addict
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Fastest way I know to kill the handling on your bike. Tires have advanced so much in the last 40 years. You are talking tires that were designed in the 60s. The only use they have is for perfect restorations......and they did not come stock on your 78. I have them on my restored 70 because that is what it came with, but on my 75 I have Bridgestone BT45s. A world of difference.
Shovel Jockey
Piano Tuna
Barry, what size BT45's are you running on your 75? I'm running Bridgestone S11 Spitfires on my 78 and really like them. The previous owner had them installed 100/90X19 and 120/90X18 (a little big I think).Will change the rear to a 110/90 when this one wears.
yamasarus
XS650 Addict
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I run a 100/90 19 on the front and a 120/90 18 on the rear. These are the correct metric sizes for the 650. If you are happy with the S11s I would stay with them. For most riding they are just as good as the 45s and cost less money. I have them on several of my bikes and S11s have become my vintage tire of choice. I would not go to a 110 on the rear. It's just too small.
I like them. They are on the F and SK. I get moderate milege from them. The road handling is good enough for my skills.
If I stayed on a paved road all the time I might think differently. My drive is 1/8 mile of packed river rock, very slippery when wet. And I take some off road short cuts, have been known to chase cows with one. The only thing worse than wet river rock is a quick turn with rear on a big patty. The rounded edged tires just slide soooooo easy on greased grass and then the cows laugh at you for falling down.
Like XSLeo said they were a good tire in the day and may be a good solution for you today.
If I stayed on a paved road all the time I might think differently. My drive is 1/8 mile of packed river rock, very slippery when wet. And I take some off road short cuts, have been known to chase cows with one. The only thing worse than wet river rock is a quick turn with rear on a big patty. The rounded edged tires just slide soooooo easy on greased grass and then the cows laugh at you for falling down.
Like XSLeo said they were a good tire in the day and may be a good solution for you today.
The 120 is not the correct size for an 18" 650 rear wheel, it's too big. 110 is correct and about the closest metric size to the 4.00 original. I've run both 120s and 110s and prefer the 110. I think the bike handles better and steers quicker with the smaller, more correct size.
25.4 mm = 1 inch, so 4.00 inches x 25.4 = 101.6 mm. That make a 100/90-18 closer to the stock 4.00 width.
A 4.25 is 107.95mm, A 4.50 is 114. A 4.75 is 120.65.
So yes a 120 is too big to match a stock tire.
On the front a 3.50 is the stock size. except for the first couple years. They used a 3.25 tire thats 82.55 mm. Most had a 3.50. 3.50 x 25.4 = 88.9. Thats real close too a 90/90-19.
100 mm = 3.93 close enough to call a 4.00. 110 is real close to 4.25.
I think, but not sure, but the numerical sized tires were all 1005 aspect ratios. So the number size tire will be taller than the same width metric tire.
3.25 would most likely be very close to an 80 mm tire.
a 3.50 would be a 90.
a 4.00 will be 100.
a 4.25 will be a 110.
a 4.50 will be a 120.
A 90/90-19 on front and a 100/90-18 on the rear are as close to stock as you can get. Unless you use a reproduction tire. Then they may just be an old tread pattern on a metric molded tire.
Leo
A 4.25 is 107.95mm, A 4.50 is 114. A 4.75 is 120.65.
So yes a 120 is too big to match a stock tire.
On the front a 3.50 is the stock size. except for the first couple years. They used a 3.25 tire thats 82.55 mm. Most had a 3.50. 3.50 x 25.4 = 88.9. Thats real close too a 90/90-19.
100 mm = 3.93 close enough to call a 4.00. 110 is real close to 4.25.
I think, but not sure, but the numerical sized tires were all 1005 aspect ratios. So the number size tire will be taller than the same width metric tire.
3.25 would most likely be very close to an 80 mm tire.
a 3.50 would be a 90.
a 4.00 will be 100.
a 4.25 will be a 110.
a 4.50 will be a 120.
A 90/90-19 on front and a 100/90-18 on the rear are as close to stock as you can get. Unless you use a reproduction tire. Then they may just be an old tread pattern on a metric molded tire.
Leo
Shovel Jockey
Piano Tuna
I thought it more important to match the height of the original 3.50/4.00 than to worry too much with the width. Then I found out that tire height varies substantially even with the same size but different manufacturers
krza
XS650 Member
Hey all, wondering if you can help with this.
I have a '75 XS650 that is built as a custom street tracker. I have K70s on spoked 19"/18" original wheels. I have traction loss issues with the K70--and I'm talking about frequent and multiple times. Fortunately I've been crashing dirtbikes since I was 10 and I don't mind it too much. But I've lowsided this bike at least 6 times now, on low speed corners, with little turn angle. Usually its a result of throttle and steer combination. I can't tell if the K70 just has poor grip, or if something else is afoot here. I do have Hagon rear suspension tailored to my weight, and the rear end is far stiffer than stock. I suspect that could have something to do with it.
Appreciate any help here.
I have a '75 XS650 that is built as a custom street tracker. I have K70s on spoked 19"/18" original wheels. I have traction loss issues with the K70--and I'm talking about frequent and multiple times. Fortunately I've been crashing dirtbikes since I was 10 and I don't mind it too much. But I've lowsided this bike at least 6 times now, on low speed corners, with little turn angle. Usually its a result of throttle and steer combination. I can't tell if the K70 just has poor grip, or if something else is afoot here. I do have Hagon rear suspension tailored to my weight, and the rear end is far stiffer than stock. I suspect that could have something to do with it.
Appreciate any help here.
How old are the tyres?
krza
XS650 Member
Very new. Bought last spring. I'm running them at 32 PSI.
On what surface?
Dirt, gravel, sand, mud, ice, snow, rough asphalt, brick, smooth asphalt, grass, wood, cinder, concrete, paint, sheet metal, cattle patties, oil slicks?
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In the late 60`s & early 70`s the Dunlop K70 was the Flat Track tire of choice, (with a razor blade cut of course). Then Carlisle then Goodyear or Pirelli M53. They all had the same basic tread design. Looking back I always blamed the tire! Low side, not enough traction. High side too much bite. Unloading was never my fault.
TimeMachine
SeventyEighte
Dunlop K81 "tt100's" front & rear are a nice versatile choice. I've used the tt100's on a previous XS standard and liked them enough to put a set on the next standard.
The K81 is a tough versatile tread pattern which I have found to feel good and hold the road with confidence.
The old tread design worked well in its day and is still a popular choice by british bike riders. Nortons commonly used tires of similar size front & rear. I've duplicated this in tire size selection running a 4.10×18 inch rear with a 4.10×19 inch front. Yes, that sounds like an oversize front, it is slightly. I have not been able to source a 3.60 front for years and would likely buy one but the 4.10 front actually feels solid and well planted on rougher roads. Tire selection is infact mostly dependant on your riding style and conditions isn't it ?
Measuring up the mounted tire set widths on stock standard rims shows the rear to be very near 4.090" and the front to be very near 4.080".
K81's do have a center channel and nicely shaped side tread blocks. They are nostalgic, eye pleasing, and ride well.
My XS's are not ridden as sport bikes so I am not pursuing modern road performance. However, the K70's just have not caught my eye. Having ridden quite a few more modern motorcycles on a variety of more modern performance tires, I would recommend looking at the K81 tt100 's over the K70's. Maybe a K70 is a better dirt tire ? A K70 is certainly easier to find.
Isle of Mann, Joey Dunlop.. TT100's
The K81 is a tough versatile tread pattern which I have found to feel good and hold the road with confidence.
The old tread design worked well in its day and is still a popular choice by british bike riders. Nortons commonly used tires of similar size front & rear. I've duplicated this in tire size selection running a 4.10×18 inch rear with a 4.10×19 inch front. Yes, that sounds like an oversize front, it is slightly. I have not been able to source a 3.60 front for years and would likely buy one but the 4.10 front actually feels solid and well planted on rougher roads. Tire selection is infact mostly dependant on your riding style and conditions isn't it ?
Measuring up the mounted tire set widths on stock standard rims shows the rear to be very near 4.090" and the front to be very near 4.080".
K81's do have a center channel and nicely shaped side tread blocks. They are nostalgic, eye pleasing, and ride well.
My XS's are not ridden as sport bikes so I am not pursuing modern road performance. However, the K70's just have not caught my eye. Having ridden quite a few more modern motorcycles on a variety of more modern performance tires, I would recommend looking at the K81 tt100 's over the K70's. Maybe a K70 is a better dirt tire ? A K70 is certainly easier to find.
Isle of Mann, Joey Dunlop.. TT100's
TimeMachine
SeventyEighte
Ditto. I switched to K81s on my other XS1B back when I cafe'd it in '74.
A real peg scraper...
krza
XS650 Member
Sheet metal, glass, and ice rinks, mostly.
Okay real answer is asphalt of all texture. Standard city streets. I've lost the back tire in hot weather on dry pavement, I lost it in warm weather on damp pavement, cold weather on dry and damp pavement... the list goes on. Dampness obviously is a factor, as is cold, but really its happened in just about all settings.
