Old Tire Sizing Nomenclature: what does it mean?

Discussion in 'Battle Scooters' started by Ludeykrus, Dec 30, 2009.

  1. Ludeykrus

    Ludeykrus Adventurer

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    On older tires, the tire would be, say, 3.00"x10.

    I know the 10 is the rim diameter in inches, but what is the 3.00"? Sidewall height?
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  2. 2speed

    2speed Puching adventurer

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    Tire width in inches.

    Today it's expressed in millimeters.
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  3. Ludeykrus

    Ludeykrus Adventurer

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    Cool.

    So would going bigger or smaller affect the rolling circumference of the wheel? My scooter should have a 2.75x10 tire, it currently has a 2.25x10, and I was wondering if going to a 3.00x10 would significantly change the gearing (the bike is currently RPM-limited, not power)

    Or is there an equivalent size for a 2.75x10 tire in today's sizing system? Say, 100/90-10?
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  4. techguy

    techguy Scooter Trash

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    It is my understanding the 10 is the diameter of the tire at the bead and the other number is the diameter of the tire from that point. If you add too much diameter you run the risk of the tire hitting the forks and other support items from being too wide. I would think the larger you go, the softer the ride and it could adversely effect your handling if the tire rolls under too easily.

    I would like to hear input from others here too.

    These guys have this tire for $22.98 pretty cheap in my book. 2.75 x 10" for knobby off road tire.

    http://tinyurl.com/ycuwope
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  5. pennintj

    pennintj Down & Dirty Mechanic

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    Modern tire for a 2.75x10 is more like 80/90-10. 90/90x10 is roughly 3.25x10 Ex: Vespa tires are 100/90x10 (3.5x10) and 90/90x10 (3.25x10)

    Trouble with a bigger tire is going to be clearance. For example, if you stick a 90/90x10 on certain smaller 50cc scooter, you won't be able to clear the exhaust, engine cases, fender, and possibly the shock.

    -=Tom
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  6. Ludeykrus

    Ludeykrus Adventurer

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    I figured that .25" either way oversize couldn't cause that much trouble. From looking at the rear tire, the worst I would have to do is possibly shave a little bit off at the rear of the case, which there appears to be enough room.

    I've been driving this scoot to work and back, 30 miles round trip. If I could squeek out a few more MPH on the top end for around $20-25, it would be worth spending less time in the freezing cold! Then again, I don't want to toss out the money by not doing some simple homework.
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  7. techguy

    techguy Scooter Trash

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    What model scoot are we talking about here?
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  8. Ludeykrus

    Ludeykrus Adventurer

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    Thanks Tom! Now I have some decent numbers to play with. I'll toss the scoot up on a bench and take some measurements and see exactly what kind of clearances I'm actually playing with.

    Techguy, it's an ~87 Honda Aero (NB50). It came with 2.75's from the factory, but the PO tossed on the 2.25's for some reason. The bike's had the air box gutted and the exhaust pipe drilled out along with the carb being rejetted. It pulls great, but tops out on flatland around 32-33mph. I think I can have it flirting with 40mph with different gearing.

    From what I've read online, they should do around 35-37mph from the factory...
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  9. pennintj

    pennintj Down & Dirty Mechanic

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    If it fits, I doubt you'll see a noticeable performance increase.

    If I was going to spend money on a Honda Aero 50 (I searched), it'd probably be towards a set of roller weights, belt, and air filter depending on mileage and age. Add to that new fuel & vaccum lines, a new spark plug, and then start looking at the exhaust.

    Then I'd start researching an SA or SB50 Honda Dio engine swap, if you're attached to that bike....or a newer Yamaha Zuma if you're not.

    Granted, a 30-mile round trip on a 50cc is probably not going to get any shorter, not matter what you do.

    If you can get the weight & variator information, you may be able to get "updated" parts for it. Daelim used that engine in the Cordi, but I don't know if all the same pieces fit.

    -=Tom
    Scooter Mechanic
    FX Motorsports
    http://www.fxmotorsports.net
    New Orleans, LA
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  10. Ludeykrus

    Ludeykrus Adventurer

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    Understood; just trying to make a crappy ride more crappy :lol3

    No engine swaps, this is a rat-scooter that I will keep cheap, reliable, and did I say cheap? No engine swaps. If I want much faster, I'd hop on the Harley or the cafe racer.

    No air filter necessary, it's been tuned to run without. Belt and roller weights will come, they work great for the stock trim motor. New plug, side-gapped. Motor surprisingly holds excellent compression and kicks over on the first kick when cold (below 30 F).

    I'll hopefully be welding up a custom expansion chamber for it tomorrow, putting max power just above the stock redline. I'm hoping for a good power curve that has peak power just a hair above the stock peak power point, while giving a good fat torque curve. My plans are this will give me the mix of reliability and speed I want while maintaining enough of a powerband to climb the rolling hills around here. The tires will be tossed on at the same time as the roller weights and expansion chamber.

    :chace
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  11. techguy

    techguy Scooter Trash

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    I don't see that you'd get much difference in the top speed when changing the tires such a relatively minor amount. I know that the biggest speed difference happen when the CVT and muffler are optimized.

    If the weights are worn you will loose top speed. Is it possible the PO added different CVT weights to make it do wheelies or anything else.? You can many times get better acceleration from weight changes but lose a lot of top-speed when you do so. Also, confirm the CVT was de-restricted and that the CDI is not limiting your speed (these are often done at the factory to meet a states "moped" speed restriction laws).

    I have hard if the muffler is not producing enough back pressure, it will lose speed too. I may be wrong on this one.
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  12. Ludeykrus

    Ludeykrus Adventurer

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    [​IMG]

    Looks like you're right. I'll be looking at 2-3 mph up top, at best. Looks like I need to recalculate new dimensions for the expansion chamber.

    Yeah, there's a lot of room for improvement in the exhaust side of the old 70's/80's 2-stroke Hondas. I've tuned my '81 Express II, and encountered the same problem. Honda apparently used the boxy 'muffler' to act as a restricting bottleneck for the system, keeping the MPH where they wanted them to be.

    The nice thing about the Aero's is they have better ports than the Expresses. Still contemplating whether I want to do anything more than portmatch the motor....

    Techguy, the rollers are stock. I don't think this scoot has a restricted CVT, do you think otherwise? And it's not the restricted CDI model. It bombs down hills fine now (had some carb problems before...), and I think the 'Iowa' models were the ones restricted with the CDI.
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  13. pennintj

    pennintj Down & Dirty Mechanic

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    Honda Dio, Kymco ZX50 performance exhaust. Probably very, very close to what you need for the Aero since the Dio/ZX/SA/etc engine is close to the NH. Can probably "make" it work if you weld.

    Jiangwayne also has a few more conservative pipes that should work. That'll give you an idea of what you're looking for.

    Or go hit the local dirt bike graveyard, or eBay, and dig up a busted fatty pipe from an old 2-stroker and have fun :)

    You'd need a bigger carb for the race pipe above.

    -=Tom
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  14. techguy

    techguy Scooter Trash

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    I don't know if it is restricted but it my understanding that unless you ensure it is de-restricted, you are wasting time on all the the other things. It may be worth replacing the rollers with DR Slider Rollers in the correct weight if they are worn. the sliders move faster than the rollers and some sets will give you a better top end (at the expense of a lower rate of initial acceleration). It may be worth your time to find out.

    I don't know if they were restricted ever but if they were it is likely to be a spacer in the CVT pulleys, a limited CDI and muffler restrictions. These are the the most common restrictions I know of.... not that I am an expert.
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  15. pennintj

    pennintj Down & Dirty Mechanic

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    If there's any restriction, it'll be the back of the variator itself where the back piece bolts to the variator....I'd look at parts 17 and 6.

    -=Tom
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  16. Cosmic_Jumper

    Cosmic_Jumper Been here awhile

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