Imperial to metric tyre sizes?

Imperial to metric tyre sizes?
Looking to shod the 650 with some new tyre's, says in book the recommended tyres sizes are

Front: 3.00-21 51P
Rear: 4.50-18 70P

Anyone know what the equivalent metric sizes are please ?


Cheers

Front will be 90/90-21, thats 90mm wide with a profile height 90% of the width.
Rear can take 120 (standard), 130 or 140 width and 80%, 90% or 100% profile. There's many combinations available, depending on street pattern, on/off road and MX fitment. I've used 120/90-18, 120/80-18 and currently 140/80-18.

Cheers,
Phil

Cheers Phil - good to know what the figures stand for.
So 120 for the rear is the factory standard , was told elsewhere its 130.
Have meaty 140 on back but would prefer to go with honda's recommendation, some seem to like the wider the better but think at this stage you have less ground pressure for the mix of off and on road riding I'll be doing, think 120 would perform better on winding tarmac than a 140 ? Or is a wider tyre more suited to the XR for longevity with the ability to spread the huge oodles of torque across the wider width ?

Can anyone please point me in a direction to show offical documentation of Metric sizes for both tyres ? Know now the standard is 120 for the rear but still looks to be conjecture of profile to the standard. I just want my bike set to standard so I can have a base to tweak from if need be.


Front: 3.00-21 51P
Rear: 4.50-18 70P

Is the 51P a 51% profile height of the width ?

Those last figures for Imperial tyres are something to do with the carcase construction (ply, weave, thickness etc.) and poss. speed rating as well.
There may be a good Metric-to-Imperial chart online, but I've not found it in my searches. The manufacturers websites look like the best places for this info.

Cheers,
Phil

Cheerz Phil

I got my set of E-07 Mitas today - 130 wide rear which is equivalent to the 120 standard you informed me about.

Tyre guy said to run them at 30 PSI on the tar or the side wall starts to heat up to much if around 20 etc

I was looking at an IRC 140/80 18 is that a tire that will fit the PIG?

Hello.

I live in spain and every two years you have to pass a technical inspection of the bike to be street legal, so usually it pays to buy a legal tyre for your bike.

my bike paperwork says 3.00 x 21 in the front and 4.50 x 18 in the rear. as its dificult to buy these sizes in spain, I went to the inspection office and ask them to give me the metric size equivalent to these.

to my surprise they gave me a list of every possible tyre that I can fit in the bike and be OK with them, including some sizes that fisically can't fit in the bike, like 150/90 17 in the front. looks like at least in spain, the only thing that needs to be the same is to keep the circumference of the tyre withing a +/- 3% of the original tyre.

so from that list I only take in account the sizes that uses the same rims the bike has these are:

front:
100-80 R21
120-70 R21
80-100 R21
90-90 R21

rear:
110-100 R18
110-110 R18
120-100 R18
120-90 R18
130-90 R18
140-80 R18
140-90 R18
160-70 R18
200-55 R18
210-55 R18
360-30 R18

another thing, completelly different, is what of these sizes can actually fit in the rims or in the bike, specially in the back. I just got a 120-90 R18 and guess they will fit with no problems, will a 130-90 or 140-80 fit, I could like people from this forum to tell me.

Jabonet