11E Rescue Bike - Project Update

[MaximPhil]

I did get so concerned about a tire I considered pinched too much that I failed to consider the load rating. On my own bike I installed the highest load rating available. The 130 wide tire has a much different appearance on the Special.

In a few days I'll go home and give you guys a break. I'm not busy enough at work right now.

Hi Jetmechmarty,
Well I know I have enjoyed the exchange of ideas about tires.You and Steve have raised some very good points that most of us had not been aware of. Jeff's bike progress is interesting too
Thanks
Phil

[crazy steve]

I should probably put together a 'tire size' tip for the tech forum, as those 'inch to metric size convertor' charts persistantly show that 120/90-17 as an acceptable replacement size for the 4.50H-17 the standard bikes came with when it's not. Most XS owners know this, but some don't and get misled by those...

[jetmechmarty]

Most XS owners know this, but some don't and get misled by those...

Who could that be?

[crazy steve]

Not pointin' any fingers here....

[fredintoon]

I should probably put together a 'tire size' tip for the tech forum, as those 'inch to metric size convertor' charts persistantly show that 120/90-17 as an acceptable replacement size for the 4.50H-17 the standard bikes came with when it's not. Most XS owners know this, but some don't and get misled by those...

Hi Steve,
I run a car tire on a Special so I'm impartial here.
4.5 is the tire width in inches and the inch-designated tires were 100% height-width ratio so they were 4.5" tall, too.
My mathbox sez 4.5" = 114.3mm which is only ~3/16" narrower than the 120mm width of a 120/90 tire and the 90% height ratio gives it a 1/2" smaller OD.
So why ain't it an acceptable replacement size?

[crazy steve]

Fred, I don't know where they came up with the '4.50' size, but the actual tire is considerably larger than that. The 'vintage' Conti I still have measures 27.25" tall (diameter) and 5.25" wide. That's over 2" taller than a 120/90-17, and about 1/4" wider. Same width as a 130, about an inch taller than a 130/90-17 as currently sold.

But that's not the deal breaker; the load rating on the 120 is only about 620 lbs. The OEM 4.50 was rated at 670 lbs, or 50 lbs more. Possibly not a problem if you ride solo, but put bags, trunk, etc and a passenger on there and you could easily exceed that rating, leading to tire failure. The 'modern' 130/90-17 (or 16) is rated at about 690 lbs, over the factory rating, so that's the only size that gets close to or meets all the requirements...

[motoman]

Fred, I don't know where they came up with the '4.50' size, but the actual tire is considerably larger than that. The 'vintage' Conti I still have measures 27.25" tall (diameter) and 5.25" wide.

................and if I had a Special, would be runnin' the 'vintage' K112/RB2.........these scoots rode and handled like a dream wearing these!........and they stuck like glue, wet or dry. Like you say, they were larger and came really close to the driveline tube on my Venturer.......could slide a washer thru the gap. For a long time now, not done in a 17" though.