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Old 4th November 2008, 18:52   #1
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Default Is 4.00x18 the correct replacement for 100/90-18?

I want to know this. A friend fitted 3.25x18 on his Apache which had 100/90-18 as stock and has no complaints. I dont want to put too fat a tyre as I will lose out on mileage and performance.

I dont care abt looks. I hope I'll be going too fast for anyone to notice :

Technically 4.00x18 means 4 inches in width which is about 101.6mm. 100/90 means 100mm is the width and 90 is the profile.

But my friend says 3.25x18 is the correct size for 100/90 and he knows a lot about bikes which makes it difficult for me to ignore him

I'm looking at the Michelin M45s and if anyone has any opinion on this, please feel free.

Last edited by Nikhilb2008 : 4th November 2008 at 18:55.
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Old 4th November 2008, 19:57   #2
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AFAIK 4.00x18 means that the tyre size is 4.00/100x18 or 100/100x18, so it is not the correct size for 100/90x18. But then neither is 3.25x18.

But I should admit, my knowledge of two wheeler tyres is rather dated & patchy.
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Old 4th November 2008, 20:52   #3
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4.00x18 doesnt specify the profile unlike the 100/90-18 type of sizes.

I am not worried about the profile at all.
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Old 4th November 2008, 21:18   #4
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I would agree with him. Will be buy the 3.25 for the CBZ and RD very soon.

3.25 - 100/90
3.5 - 110/90
4 - 120/90
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Old 4th November 2008, 21:23   #5
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Quote:
Originally Posted by crazydiablo View Post
I would agree with him. Will be buy the 3.25 for the CBZ and RD very soon.

3.25 - 100/90
3.5 - 110/90
4 - 120/90
what exactly are these translations. The inches to metric conversions dont match
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Old 4th November 2008, 22:03   #6
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This might help


http://www.motobrio.com/catalogues/T...sion_Chart.pdf
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Old 4th November 2008, 22:31   #7
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Quote:
Originally Posted by Nikhilb2008 View Post
A friend fitted 3.25x18 on his Apache which had 100/90-18 as stock and has no complaints.

Technically 4.00x18 means 4 inches in width which is about 101.6mm. 100/90 means 100mm is the width and 90 is the profile.

But my friend says 3.25x18 is the correct size for 100/90 and he knows a lot about bikes which makes it difficult for me to ignore him
Hi Nikhil
Your friend is right actually 3.25 x 18 is nothing but 100 / 90 R18

In fact your friend has fitted his apache with the same size of the tires i.e. same width and same aspect ratio.

Quote:
Originally Posted by Nikhilb2008 View Post
4.00x18 doesnt specify the profile unlike the 100/90-18 type of sizes.

I am not worried about the profile at all.
I think the profile your mentioning is nothing but aspect ratio !! If I am correct the 4.00 x 18 would be nothing but 120 / 90 R 18 in this case you will be going wider, well technically when you convert the exact inches into mm you wont get the exact answer.

Inch system doesn't mention about the profile because they are known as standard profile or square profile. Hope that answers your question.


Quote:
Originally Posted by Mpower View Post
what exactly are these translations. The inches to metric conversions dont match

In my bike I am running with 140 / 80 and so my size would be 5.50. There is no straight answer, there are actually conversion charts and since the mine is a low profile its tough to tell it exactly in inches as there is not correct substitute.

Nikhil : If your are very doubtful like which tire, the easiest thing would be to buy the one with metric system


EDIT : Shaken soul : thanks for the posting the conversion chart I think it will be of great help

Last edited by rranjith_kum : 4th November 2008 at 22:34.
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Old 4th November 2008, 23:19   #8
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Hi Nikhil, the motorcycle tyre that are sized in Inches x Dia and mm/profile x Dia are not comparable directly. I had a MRF Moto C 4.25x18 tyre on the Bullet and the thread section width was nearly comparable to a 120/90 x 18 Zapper Q, but then the Zapper Q wouldn't fit between the swingarm of my bike :S

I got the section width data from the website MRF LIMITED : MRF is India's No.1 tyre manufacturer producing a premium range of tyres and conveyor belts that meet quality standards across the globe. But when i tried to checked now i am getting a database error as i click on the "Tyres" link. MRF's website, the link i gave, had a lot of information regarding the tyres, like section width, diameter, load rating etc etc. Sad that the database is down.


I am pretty sure that the section width would change for different manufacturers, and for different models from the same manufacturer, even if the advertised tyre size is same.
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Old 5th November 2008, 11:08   #9
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Quote:
Originally Posted by Nikhilb2008 View Post
I want to know this. A friend fitted 3.25x18 on his Apache which had 100/90-18 as stock and has no complaints. I dont want to put too fat a tyre as I will lose out on mileage and performance.
100/90 = 3.25

The 3.25 M45 I got from you, put it on my bike with a CBZ rear rim. that thing is too friggin fat :P Its the same size as a 100/90!!!!
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Old 5th November 2008, 11:16   #10
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Well, I dont have a choice actually.
The only options I have now are 3.00x18 or 4.00x18. Company doesnt have any other sizes in stock.,
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Old 5th November 2008, 23:19   #11
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I fitted the 3.00 to the front and the 4.00 to the rear. 4.00x18 is a little bigger than the stock size but not too much. The grip is awesome. The ride comfort though is truly in a class of it's own. I havent really pushed the tyres to the limits of it's grip and hence cant judge properly, but the ride comfort is truly astonishing.
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Old 6th November 2008, 03:57   #12
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Quote:
Originally Posted by Nikhilb2008 View Post
I fitted the 3.00 to the front and the 4.00 to the rear. 4.00x18 is a little bigger than the stock size but not too much. The grip is awesome. The ride comfort though is truly in a class of it's own. I havent really pushed the tyres to the limits of it's grip and hence cant judge properly, but the ride comfort is truly astonishing.
Good thing you went with a 3.00x18 on the front for your P180.
first model or the DTSI and which version?
For the Zma, the 2.75x18 M45 is enough i feel, if available, even if shod with 4.00x18 M45 at the rear. i.e.
Maybe a tad heavy-booted but does the bike feel more planted now and the front disk brake feels a bit more progressive in feel and bite?

M45 is basically a rear tyre for motorcycles and even as per that chart posted by SS, 4.00x18" is 110/90.
So that is pretty ok i think.
Plus you also have a bigger front tyre to balance out any changes in the stance.
Please do keep us updated with your experiences and thoughts.
Will be very helpful to newbies like me as there is a sudden and serious dearth of sensible riders who can analyse and comprehend the effects of changes to their bikes.

Last edited by BIKeINSTEIN : 6th November 2008 at 04:14.
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Old 6th November 2008, 08:52   #13
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Mine is a Pulsar 180DTSi V1. 18"steel rims and no gas filled shocks.

The biggest difference I can find is the ride quality. It truly glides over bad roads.

The grip part, havent really pushed my bike. It was dark when I left my shop last night and even though I rode for about 20 odd kms after that, I didnt push it because it was dark. I pushed only once on the flyover coming from Richmond road towards Lalbagh road and I just didnt feel scared at all pushing the bike on the curve.

Will test more when I get some time to hit theh ighway.
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