Is a 140/80 18 always a 140/80 18??

Hi all,

I need to replace my first rear tyre and looking to get the Dunlop Geomax MX51. I spoke with the local bike shop and they tell me there is no MX51 available in that size. I explained that the stock tyre was a Michelin Enduro Competition 140/80-18 and they said all brands were different, and that a 140/80 in Michelin would probably equate to a 120/90 in the Dunlop. Well I was a little confused, I mean, it's maths right, and 140mm = 140mm. Am I missing something ?

Funnily enough though, Dunlop don't make a MX51 in 140/80:

http://www.dunlopmotorcycle.com/tire-catalog/off-road-adventure/mxsx-off-road-geomax-series/mx51/

So could I go for a 120/90-18, which seems to be the closest, or would I be sacrificing too much grip? Or perhaps just replace the Michelin with another Michelin? I got 1100kms out of it and never had any real problems, I was just hoping to try something different for comparison.

The shop told me I would get better cornering if I went for a 120, does that make sense?

Thanks one and all in advance.

A 120 in another brand will be the same size as your 140 michelin... I ride a 120-100-18 Kenda. Any tire that says 140 is going to be the same as a 120 as far as I know. My bro rides a 110 and the difference in width between his and my tire is a mere 5mm or 1/4 inch.

I've heard similar for Mich dirt tire sizing.

Here's an easy thing to do.

Measure the knob to knob width.
Measure the sidewall to sidewall width.

If those are similar, don't worry about it.

A great all around tire for these is the Dunlop 606 and it comes in a 140.

Thanks guys,

Rensho you are right on the money. After some discussion today it turns out Michelin measure the width including the knobs, where as pretty much everyone else just measures the carcass. So yep, a Michelin 140 = a Dunlop 120. Those wacky Frenchmen!

tye size can be unusual: I think it may be a proportion, ie side wall 80% of the width, but not sure.
The best tyre I have found is dunlop 120/90/18 D952 sports 65M. Great tread, feel, and lasts. I will get the equivellent on the front next. For me I want the tyre close to the ground and don't like the 120/100/18: too much bounce.

I am also finding particularly on the front wheel these days a higher tyre pressure so the suspension gives before the tyre? What pressure do people use front and rear? I am finding 12 psi is not enough on the front and is sort of ok on the back although 13/14 psi is better.

I think the peculiar sizes of the Michelin only apply to the AC10. This tyre is road legal (in UK) but not FIM approved. The blocks are 18mm and FIM max block size is 13mm I think.

Anyways, the AC10 are measured across the width of the carcass and not the blocks. So an AC10 120 is equal to a 140 in their and other manufacturers ranges. You can by the Michelin competition in standard sizes.

Thanks

Derek

I went from the 140 metzler to a 120 dunlop under the same advice that they are a similar width. I have found that while the overall width is the same, the tread profile is narrower on the 120. It seems to me that the 140 is flatter across the tread and the 120 is a rounder shape making it good for corners but not so good on highspeed stuff. I loved the metzler but got less than 400 km out of it! I get almost double out of the dunlop. Im on my second dunlop now but am thinking i want to find a similar wearing tyre in a 140 next time.

akshun said:

I went from the 140 metzler to a 120 dunlop under the same advice that they are a similar width. I have found that while the overall width is the same, the tread profile is narrower on the 120. It seems to me that the 140 is flatter across the tread and the 120 is a rounder shape making it good for corners but not so good on highspeed stuff. I loved the metzler but got less than 400 km out of it! I get almost double out of the dunlop. Im on my second dunlop now but am thinking i want to find a similar wearing tyre in a 140 next time.

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Tyres seem to be such a personal preference, I've read great reviews and terrible reviews on pretty much everything There is a local shop that had the Michelin S12's going for cheap and they seem to have a pretty good wrap online. I thinks it's between the MX51 and the S12's. Heading in to summer I'm, thinking the MX51 would probably be a better choice.

Maybe consider the IRC M5B, 130? The stock Dunlops on my '13 did not instill confidence in handling for me. It is a motocross tire after all . . . .

M5B wears like iron, and is an absolute monster of a knobby. Designed for off road/desert a bit more than the M51/M31, in my opinion. Only a trials tire hooks up better :mrgreen:

The 130 is just the right size for our big bores. Ive run it since '99, aside from the Pirelli trials.

Regards

Berg570FE said:

Maybe consider the IRC M5B, 130? The stock Dunlops on my '13 did not instill confidence in handling for me. It is a motocross tire after all . . . .

M5B wears like iron, and is an absolute monster of a knobby. Designed for off road/desert a bit more than the M51/M31, in my opinion. Only a trials tire hooks up better :mrgreen:

The 130 is just the right size for our big bores. Ive run it since '99, aside from the Pirelli trials.

Regards

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Man, those are the biggest knobbies I've ever seen

It's listed as a soft terrain tyre, do you find it holds up from a wear perspective for use on rocky areas as well?

Yes, it wears well. Certainly longer than the Dunlops. It has a very stiff carcass, so running slightly lower tire pressure gets you the most out of it. A guy can become spoiled with that amount of hook-up is about the only problem, wanting a fresh tire when its not really needed . . . yet

Rocky Mountain has the best price on it, from what Ive found.

Regards

Berg570FE said:

Yes, it wears well. Certainly longer than the Dunlops. It has a very stiff carcass, so running slightly lower tire pressure gets you the most out of it. A guy can become spoiled with that amount of hook-up is about the only problem, wanting a fresh tire when its not really needed . . . yet

Rocky Mountain has the best price on it, from what Ive found.

Regards

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Thanks very much. I'm in Australia and the only size in the country at the moment is 120/80. Think I should give it a run?

gjws said:

Berg570FE said:

Yes, it wears well. Certainly longer than the Dunlops. It has a very stiff carcass, so running slightly lower tire pressure gets you the most out of it. A guy can become spoiled with that amount of hook-up is about the only problem, wanting a fresh tire when its not really needed . . . yet

Rocky Mountain has the best price on it, from what Ive found.

Regards

Click to expand...

Thanks very much. I'm in Australia and the only size in the country at the moment is 120/80. Think I should give it a run?

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The 120 will work just fine.
I've been running M5b's for ten years or so, the only drawback running the larger sizes is that they don't let the bike lean over in corners as easily as the smaller sizes. On my xr650r I started with the 140, then the 130 and finally the 120 which I stuck with for it's better turning traits.
I usually put the M5b on at the start of the rainy season and by the time dry season comes around it's worn down & rounded off just right for harder terrain.
Unfortunately S12's last about ONE day on higher HP bikes, total waste of money on anything over 250cc. Been there..