Wheel numbers on a Grimeca "snowflake" rim.

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Wheel numbers on a Grimeca "snowflake" rim.

Postby RebelRider.Mike » Sat Aug 10, 2013 3:48 am

Stamped on both rims is this code:

D1.35x17" DOT 1/78

I'm guessing that D1.35 is the inside diameter of the wheel where the bead of the tires go. Can anyone confirm that, or set me strait?

Now, the tires are 2.25" which makes sense as they are "fatter" than the rim. Is there a minimum and maximum width size that will safely fit on these rims?

I get the 17" since the rims are 17" long.

The DOT 1/78 has me stumped. Safety code? Speed rating?

Thanks folks!
Mike

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re: Wheel numbers on a Grimeca "snowflake" rim.

Postby RebelRider.Mike » Tue Aug 13, 2013 4:30 am

Hi folks, I may have a partial answer to my question.
DOT 1/78 may refer to a date of manufacture. I haven't found any examples of this particular code type; if it were 178, it would mean the first week of the 7th month of the 8th year of some decade. That may only refer to tires though. Not sure about rims.

My best guess is that the rims were manufactured in January, 1978. I guess that would make sense as their on a 1979 moped.

Regardless, the code seems to have nothing to do with the tire size needed. I'm still curious to know if there is a range of sizes that will fit the rims, or if I need to stick to the size that is already there.
Mike

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re: Wheel numbers on a Grimeca "snowflake" rim.

Postby John » Tue Aug 13, 2013 4:54 am

probably date... January 1978 when rim style was OK'd by what ever governing body, nothing more!
John

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re: Wheel numbers on a Grimeca "snowflake" rim.

Postby RebelRider.Mike » Wed Aug 14, 2013 8:46 am

Well, I may have a partial answer to my tire width question.

I've read in several places that reducing the tire width may actually be dangerous. The idea is that a narrower tire may not perform properly during turns, when the forces exerted are to one side of the tire instead of the bottom.

The only reference I could find as far as rim width vs. tire width is here:
http://www.mtsac.edu/~cliff/storage/gs/Motorcycle_Rim_Width_Tire_Size_Chart.pdf
While my rim width is not listed, the general pattern seems that tire width may be increased up to 2 sizes from "standard".

A wider tire will have a different profile on a given rim. I.e. a 2.5" wide tire will actually be a little less than 2.5", because it is on a smaller rim than it was intended for. So I guess the height and ratio would change too... Of course, this all assumes the tire will even fit inside the fenders and swing arm.

Someone jump in here and tell me if I'm totally off about this stuff.

I find it interesting that mopeds seem to have the same sized tires front to back, whereas motorcycles tend to have larger rear tires. Anyone ever have a larger moped tire in the back? Would it make any difference?
Mike

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re: Wheel numbers on a Grimeca "snowflake" rim.

Postby scootmeister » Wed Aug 28, 2013 11:00 pm

Mike, I have a Sachs Prima G3 with the same wheels. The standard tire size is 2.25, but I installed a 2.5 on the front and a 2.75 on the rear with no problem. I could have gone with a 3.0 on the rear, but I want plenty of clearance between the tire and the chain. Some peds have narrow swing arms that limit the width of tire you can use. As long as your tires clear everything, frame, fenders, chain, shocks, etc. you're OK. Lots of guys stick to smaller tire size because of weight.
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