Tire size conversion woes...

[CRXSi90]

I need new tires for my 1981 Kawasaki KE175. There are three options that I’m considering:

Shinko 244 (2.75-21, 3.50-18)



Shinko 705 (90/90-21, 4.10-18)



Shinko 250 / Shinko 712 (MH90-21, 100/90-18)




I’m struggling with two things: (1) type of tire I want, and (2) what sizes will fit. My goal in this post is to get help with #2.

The factory tires are 2.75-21 and 3.50-18. The 244’s are right on as far as size, but realistically I should have something more street-oriented for the type of riding I’ll be doing. I say this thinking about grip and lifetime. I also have an appreciation for staying with the factory size, which is where the problem arises.

http://www.dansmc.com/tirespecs1.htm

I think the Shinko 705 would be ideal for me, but the front would be ~20mm wider and the rear would be ~15mm wider. For the Shinko 250/712, the front would be 10mm wider, and the rear would be 11mm wider. I think the 705 is my ideal tire, but I’m not comfortable going that much wider due to increased stress on the rim, and reduced contact area due to bowing of the tread. I’m not concerned about clearance because I currently have 3.00-12 and 4.10-18 non-DOT knobbies.

My best guess at this point is that the rim widths are: front-1.85” rear-2.15” based on measuring the outside of the rim (2” and 2.31” F/R).

So here are the questions: Are my concerns about going 15-20mm over the stock width justified? Would I be better off using the 250/712 combo that’s 10-11mm over?

Thanks,
Kevin

P.S. Here’s a few more helpful links to add to the confusion:
https://www.denniskirk.com/help_center/tire-sizes.jsp
http://www.dropbears.com/u/utilities/tyrerim.htm
http://www.motorcycle-superstore.com...IZE-CHART.ASPX

[crazy steve]

I don't think you'll have any problems fitting any of these tires; I suspect the the main difference in 'size' is the tread design and the actual tire carcass is probably very close. The dual-sport tires simply have a 'larger' tread design to help with wear/traction.

With that said, the dual-sports would probably be the best choice if you're planning any off-road riding in dirt; the 250/712 combo will give near-zero traction on any even slightly muddy surfaces...

[CRXSi90]

Hi Steve, thanks for the feedback. I agree that it's silly to put street tires on a dual sport, but realistically I'll be doing 90%+ street riding. I know it's the wrong motorcycle for what I'm doing, but my XS is in a sad state of disrepair, and this is the quickest way for me to get back into some 2-wheeled fun. Then again, I can't say for sure that I won't be going off-road, so I don't want to rule out that possibility.

I ran across another reference for rim sizes and tire widths. According to this, the Shinko 705's are an acceptable alternate size, which is currently my preference.

http://www.hagon-shocks.co.uk/common/pdf/wheels2011.pdf

Here are the tire sizes they claim to be acceptable for my rim widths. Bold is the "recommended" width, others are "alternate".

1.85" Rim

80 (3.15)
90 (3.54) - Shinko 705

2.15" Rim

80 (3.15)
90 (3.54)
100 (3.94)
(4.10) - Shinko 705
110 (4.33)

Thanks again. I'll shoot for getting the Shinko 705's.

[jetmechmarty]

The tire manufacturer should tell you what the minimum width is for their particular tire. Most list them on their websites.

[CRXSi90]

Good thought - go straight to the source. The widths weren't listed on the website, but I just sent an email off to their support address. Thanks!

[CRXSi90]

Fwiw

I contacted Shinko, and they recommend a 2.15" rim for the 90/90 and 2.5 for the 4.10-18. Both of those are the next "step" wider than what I have. They are listed on the Korean version of their website.

Shinko 244
http://www.shinkotire.co.kr/english/...ode=AA00050045

Shinko 705
http://www.shinkotire.co.kr/english/...ode=AA00050044

Shinko 250 (front)
http://www.shinkotire.co.kr/02produc...ode=AA00040038
Shinko 712 (rear)
http://www.shinkotire.co.kr/02produc...ode=AA00030028

I contacted Kenda with a similar question, and their recommendations were pretty much the same. Neither offered an "operating range" for the width, just a single width or nothing. But as I have seen in my search, people have had success with slight deviations from the recommendations, which is probably what I'll try. We'll see what strikes my fancy when I place my order (early May).

Thanks for your thoughts and suggestions!

[crazy steve]

Remember, those are 'recommendations', not an absolute. They call out a 3" wide rim for a 130/90-17 tire (the correct size for a XS standard) but the XS 17" rim is only 2.5" wide. Lots of owners run these with no issues at all....

[daveyg]

I did something similar, I have a 72 Suzuki ts185 that I put 120/90/18 kenda challengers on. Only problem turned out was that my front rubs on both forks, as they r not spaced wide enough for the tire, making it feel like the front brake is on full lock. I'm considering machining my own trees with a wider spacing and slightly less trail...

[CRXSi90]

I did something similar, I have a 72 Suzuki ts185 that I put 120/90/18 kenda challengers on. Only problem turned out was that my front rubs on both forks, as they r not spaced wide enough for the tire, making it feel like the front brake is on full lock. I'm considering machining my own trees with a wider spacing and slightly less trail...

I bet that's a fun ride. Do you have any pictures? I had to have mine transported across the state, but it's scheduled to arrive on Tuesday. I'll try to get some pictures of mine when it arrives. How fast have you had your TS185 going? I had the KE175 topped out at 62mph, but that was with 8 year old gas and a -1 tooth front sprocket. I don't have any aspirations of freeway cruising with it, but I'm excited to see what it will do with some new gas and either a factory or +1 sprocket.

[daveyg]

Ha. Fastest I've had the ts going was about 10mph the day I got it, after a quick carb clean and new plug, but with half flat tires. Need to get the front tire/forks sorted out before I can get her on the road again.