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So your width will vary a little depending on the size rim u use.
On my 1.85" rim the width at the widest point is about 3.6 inches...
20210614_125055.jpg
 

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Discussion Starter · #22 ·
Thank you for that, JCW! I've been delving deeper into Conti's catalogs. In your 2015 catalog and elsewhere, they say acceptable rims for the 100/90 R 18 RoadAttack 2 CR were 2.50 and 2.75. But now, in some of their catalogs, they say that the same size RoadAttack 3 CR can be fitted to a 2.15 rim. I emailed their technical department to try to clear up the confusion. I don't really expect a reply, but we'll see.
 

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Looks like a huge range of rim widths...
In fact 2.15 appears to be right on the middle of the range!

104718
 

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Discussion Starter · #24 ·
Yeah, I'm liking that 2.15 is the pick of the litter, but suspicious of that way wide range. Even if their tires are the hot lick, I'm not sure we can really trust Conti's specs!
 

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I don't have a 90/90 Conti but I do have the old style ribbed front 3.25x18 on a 2.15 rim off XS650.
It's much closer to 3-5/8" (3.625") wide than 3-1/4" (3.250")
Tyres are always 'nominal' although I do remember reading somewhere many years ago to have minimum of 1/4" each side and 3/4" clearance around outside to allow for 'growth'
The centrifugal loading on tyres is also extremely high at high speeds. I forget which magazine did the article but 1 pound of 'rubber' on 18" rim at 150mph was close to 4 ton load? (if I remember right)
 

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Discussion Starter · #26 ·
Hi Crazypj. Yes, tires vary a lot from their nominal sizes, which is why I've been so frustrated by Continental's rather screwy spec sheets. Fortunately, JCW has a 90/90 R 18 ClassicAttack and was able to measure the width for me. As it turns out, that tire is pretty darn close, at 91.5mm wide. One of the benefits of the Conti's radial construction is that radials don't gow much at speed, but I'm figuruing on leaving a good 1/2" on top, just in case. BTW, if you are reading this JCW, did you happen to measure the overall diameter of that tire?
 

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I wonder what's the best way to measure diameter... I can think of a couple ways.... all with their own drawbacks

It'll be an estimate unless I dismount the wheel.
 

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BTW. I have about 1/2" clearance to my fender. Now I'm not sure if the fender flexes a little as well but I've topped the bike out at redline in top gear (probably only around 110 or so) repeatedly on the track and I don't see any evidence of rubbing.
 

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Discussion Starter · #31 ·
Please don't go to any trouble on this. Just eyeballing a ruler or tape through the center (axle) will be close enough. Amazon lists the size (for shipping purposes) as 24" x 24". If the diameter is that small, it will not work for me. I am hoping for something in the 25-25.5" range. Thanks, guys.
 

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i didnt see the bit about racing the bike. so why is this thread in the “racing” section? boring...
 

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i didnt see the bit about racing the bike. so why is this thread in the “racing” section? boring...
Good point...

So, this'll be my last contribution...
a tape wrapped around the circumference measured 76.25". 24.2" diameter.
Tire might have been low on pressure from sitting... so take the measurements as it is, an estimate.
Compared to continental's conti go dimensions in the same size, 619mm vs 615mm. Well within the error of my measuring method.

Measuring any other way i had available to me was way more inaccurate. +/- up to 1/2 to 3/4" and really just a guess due to parallax error.
 

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Discussion Starter · #34 ·
Thank you very much for getting that measurement, JCW. Sounds like a hassle. That OD is a bit small for this bike, I think, which makes the 100/90 R 18 RoadAttack the best choice for me. So far as putting my opening query on the racing forum, dirtchecken, the tires in question are, from what I understand, more common on the track (at least for track days) than they are on the street. I needed an answer to the question, and sure enough, JCW was here to answer it.
 

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So far as putting my opening query on the racing forum, dirtchecken, the tires in question are, from what I understand, more common on the track (at least for track days)
i type this from the track and last post too. big al races the sport demons, most others are on avon am23, 22, 20’s, metz sport techs or conti attack sports 2,3. you might see a bt45 or two. thats my track report, carry on, out
 
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Thank you very much for getting that measurement, JCW. Sounds like a hassle. That OD is a bit small for this bike, I think, which makes the 100/90 R 18 RoadAttack the best choice for me. So far as putting my opening query on the racing forum, dirtchecken, the tires in question are, from what I understand, more common on the track (at least for track days) than they are on the street. I needed an answer to the question, and sure enough, JCW was here to answer it.
No problemo
 

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If you fit a 100/90 you will probably need a wider rim
I went to post 1 and saw you already have 2.15 rim
 
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