Dirtbike Tire help

[mustangguy289]

What size is equivalent to 4.60-17 and 3.00-21 in the metric labeling?

[dsrtuckteezy]

just run a 110 or 120/90 on the back and a 100/90 on the front..

[mustangguy289]

Would an 80/100-21 work on the front?

I am looking into the IRC ve-33 rears in 4.6-17 and the IRC ve-35 for the front in 80/100-21.

Rear: http://www.motorcycle-superstore.com...Rear-Tire.aspx

Front: http://www.motorcycle-superstore.com...ront-Tire.aspx

This for an old '82 Yamaha XT 250 dual sport. I ride around on the farm and take it to Red River Motorcycle Trails.

[dsrtuckteezy]

yeah it would...the 80/100 will probably be a bit skinnier than what you have now..

[mustangguy289]

What about overall diameter. This one has a speedometer... and not that it is a high priority, but I would like to keep it fairly accurate.

[dsrtuckteezy]

well, aspect ratio on standard tires are usually 100%, so since youre going with a 80/100 (second number being the aspect ratio) the tire will be the same height on a 21 in rim...

edit: assuming your original tire has a 100% aspect ratio (as tall as it is wide) and youre wanting to go with a skinnier tire than stock with the same aspect ratio, it will be roughly between 40-60 mm shorter than stock..

i think...hah

[mustangguy289]

I was searching for conversions last night before posting this question and I ran across a few sites that said all of the tires marked as metric ( ie 80/100) are radial and the ones marked standard (3.00-21) are bias ply. Is this true?

If it is true, can you mix the two? Have a standrard sized tire on the rear and a metric sized tire on the front?

[dsrtuckteezy]

yeah im pretty sure the majority, if not all, standard tires are not belted. bias ply only...thats why theyre are kind of doing away with standard..

i would not mix...either have both radial or both bias ply

[mustangguy289]

yeah im pretty sure the majority, if not all, standard tires are not belted. bias ply only...thats why theyre are kind of doing away with standard..

i would not mix...either have both radial or both bias ply

Ok thanks. The rear tire IRC VE33 is offered in both the 4.6-17 and a 110/100-17 which is why I asked.

Specs:
Common 3.00-21 is 27.6 in dia, 3.15 wide on a 1.6 rim
4.60-17 is 25.4 dia, and 4.72 on a 2.15 rim

The VE35 front 80/100-21 is 27.99 dia, and 3.66 on a 1.6 rim ( a tiny bit taller and wider)

The VE33 rear 110/100-17 is 25.98 dia, and 4.92 on a 2.15 rim (also a tiny bit taller and wider).

Thanks for your help.

[dsrtuckteezy]

but imo, since this is for an old ass dirtbike that was built around bias ply tires, i would stick with just that..

Bias and radial tires have significantly different dynamic properties. They deflect differently, create different cornering forces, have different damping characteristics, as well as other differences. In order for radial tires to be introduced into the two-wheel market, it was necessary to change certain characteristics of the motorcycle. The introduction of the radial tire led to such things as modified frames, new steering geometries and suspensions. Therefore, it is recommended that a motorcycle be used with the type of tire construction that it came with originally. If a change is to be made, then it should only be done if the motorcycle or tire manufacturer has approved the change. Above all, do not mix bias ply and radial tires on the same motorcycle unless it is with the approval of the motorcycle or tire manufacturer.

[mustangguy289]

but imo, since this is for an old ass dirtbike that was built around bias ply tires, i would stick with just that..

There is hardly any availibility in the 3.00-21 except for on street tires. I can get a nice offroad 4.6-17 but not the front tire.