Front tire size question?

cbxnova · Post by **cbxnova** » Fri Dec 22, 2006 9:39 pm

Planning to mount a 2.50x18 boomerang rim on the front of my '81 CBX. The standard front wheel presently has a 100-90-19 but with the wider front wheel, I'm wondering if I shouldn't go to the 110-90 tire? The 100-90 tire on the stock wheel looks absolutely normal, just don't want the 110 tire to look TOO BIG. Any imput from you folks??? Thanks, Chuck in Mpls....4188

dan1995 · Post by **dan1995** » Fri Dec 22, 2006 9:41 pm

you might have a problem with tire clearance with the fender

cbxnova · Post by **cbxnova** » Fri Dec 22, 2006 9:48 pm

Hi Dan, I noticed that on Linda's '82 that she has a 110-90-19, where the new rim I plan on mounting is a 18. Yes the tire is fatter, I'll have to consider that...Thanks for your input...CO

Terry · Post by **Terry** » Fri Dec 22, 2006 11:16 pm

On my 82 I've run the 110 on a stock rim with no clearance problems. I switched back to the 100 for better turn in in the twisties.

Mike Barone #123 · Post by **Mike Barone #123** » Sat Dec 23, 2006 12:07 am

cbxnova wrote:Planning to mount a 2.50x18 boomerang rim on the front of my '81 CBX. The standard front wheel presently has a 100-90-19 but with the wider front wheel, I'm wondering if I shouldn't go to the 110-90 tire? The 100-90 tire on the stock wheel looks absolutely normal, just don't want the 110 tire to look TOO BIG. Any imput from you folks??? Thanks, Chuck in Mpls....4188

Hi Chuck

Here is a good link for you to check tire diameters and widths http://www.us.metzelermoto.com/media/metzeler_2006.pdf

It looks like the circumference of 110x90x18 is 657mm and the 100x90x19 is 674mm which is about 3/4" larger.

The 110 looks to be 6mm wider or 1/4" ...or 1/8" on each side, but again check the charts yourself.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

A oversize 19" front tire will eat the front fender tip off an early model under certain conditions....as in ...at redline in 5th. Note I did not say the tire was a 110 because this was way back in the early 80s and I am not sure the tires sizes were metric like now ...but I do know I did fit an oversize front tire..........and the results were as stated.

Another phenom with this oversize front tire was that the Dawgie didnt wonder around as much as with the orig size front tire........probably less wind resistance with an inch or so of the front fender missing.

How have you been doing............welcome to the line btw.

Mike

EMS · Post by **EMS** » Sat Dec 23, 2006 6:21 pm

I had these Gold Boomerangs on my '79 for a while. The front was a 100/90-18. Had to lower the front fender a little to address the "dirt bike look" . I would agree with Terry on the handling, although there may not that much recognizable difference.

Mike Barone #123 · Post by **Mike Barone #123** » Tue Dec 26, 2006 7:10 pm

cbxnova wrote:Planning to mount a 2.50x18 boomerang rim on the front of my '81 CBX. The standard front wheel presently has a 100-90-19 but with the wider front wheel, I'm wondering if I shouldn't go to the 110-90 tire? The 100-90 tire on the stock wheel looks absolutely normal, just don't want the 110 tire to look TOO BIG. Any imput from you folks??? Thanks, Chuck in Mpls....4188

Hi Chuck

This is an exaggerated fender view of what the 110x18 front will look on your CBX since the rim in this photo is 17" vs your 18" rim

As Mike/EMS said you will have to lower the fender to make it look right with the 110x18 rather than worry about your new front rim/tire being toooo tall or big.

Hope this helps. You going to make any of the rallies this year.

Mike

cbxnova · Post by **cbxnova** » Tue Dec 26, 2006 9:22 pm

Thanks Mike for the exaggerated photo. Seeing how the 100 tire is taller, maybe I should stick with the 100-90-18. I also don't want the bike to "sit" too low...cornering-wise. I've never seen gold boomerangs on a late model and can't imagine that they'd that look on one. But...my '81 is a different color so I'm gonna give it a go.

Rallies; I have Daytona in the back of my noggin' hoping to [i]maybe [/i]make it there. I have somewhat of a new job where my "summer bids" only let me get away for 3 days max. (teamster). Thanks for the replies...Chuck.

Mike Barone #123 · Post by **Mike Barone #123** » Wed Dec 27, 2006 1:26 am

cbxnova wrote:Thanks Mike for the exaggerated photo. Seeing how the 100 tire is taller, maybe I should stick with the 100-90-18. I also don't want the bike to "sit" too low...cornering-wise. I've never seen gold boomerangs on a late model and can't imagine that they'd that look on one. But...my '81 is a different color so I'm gonna give it a go.

Rallies; I have Daytona in the back of my noggin' hoping to maybe make it there. I have somewhat of a new job where my "summer bids" only let me get away for 3 days max. (teamster). Thanks for the replies...Chuck.

Hi Chuck

FRONT TIRE SPECS

SIZE>>>>>> >>Diameter >>>Width>>>Rim Width>>>Rim Range

100x90x19 >>> 674mm >>> 108mm >>> 2.5">>>2.15"-2.75"

100x90x18 >>>636mm >>>102mm >>>2.5">>>2.15"-2.75"

110x90x18 >>>657mm >>> 114mm>>> 2.5">>>2.15"-3.00"

Based on this I would go for the 110x18 if you have more than 3mm of clearance on each side of your 100x19 current tire. The 110 is only 17mm or 3/4" in diameter less than stock as where the 100x18 is over 1.5" smaller in diameter than stock!!!!

REAR TIRE

I need your new rear rim width and diameter plus the stock late model rear tire size for a late model .....then...........I can figure out what rear tire you should buy to maintain the stock front tire and stock rear tire size relationship and we can put this puppy to bed.

Daytona is iffffy for me..........guessing no....so how about the Marlinton National in 2008.

Best

Mike

Mike

EMS · Post by **EMS** » Wed Dec 27, 2006 7:04 am

The Gold Boomerang rears came in different sizes. Mine is from my CB1100R that was in pieces at the time and is a 3.00 wide. the CB1100F rear is 2.75.

cbxnova · Post by **cbxnova** » Wed Dec 27, 2006 11:01 pm

My "new" rear wheel is a 2.75x17 (no tyre yet), the stock (tyre) is a 130-90-18. Not a lot of choices for the rear...mostly 130-90-17s. What's the widest you can go in the stock swingarm, 140? I see in the Kirk catalog that Michelin makes a PILOT ACTIV bias ply sport touring tire in a 150-70-17 and a 140-70-17. I was contemplating trying a pair of Kendas on the bike. I've read some favorable reports on these tires. Decisions, decisions, decisions.....co

Mike Barone #123 · Post by **Mike Barone #123** » Thu Dec 28, 2006 10:10 pm

cbxnova wrote:My "new" rear wheel is a 2.75x17 (no tyre yet), the stock (tyre) is a 130-90-18. Not a lot of choices for the rear...mostly 130-90-17s. What's the widest you can go in the stock swingarm, 140? I see in the Kirk catalog that Michelin makes a PILOT ACTIV bias ply sport touring tire in a 150-70-17 and a 140-70-17. I was contemplating trying a pair of Kendas on the bike. I've read some favorable reports on these tires. Decisions, decisions, decisions.....co

Hi Chuck...given the info you supplied........the answer is as you already noted......the only rear tire you can use that fits the rear 2.75 x 17 ....is a 140x70x17 ...and by chance ....this is a great match for the 110x18 front from the standpoint of keeping the stock late model steering geometry.

The stock late model tire sizes you supplied have the stock front tire being 5mm less in diameter than the stock rear tire.

The 110x90x18 and the 140x70x17 has this new front tire being 2mm larger in diameter than then new back tire which is very close so dont go for the 100x90x18.

This is a 7mm difference which can be made up by raising the forks in the tubes by 3.5mm. If you dont do this your late model will steer even slower than stock

NOTE: After installing the new tires I would ride it as is without playing with/raising the forks......you never know...it just might be ok as is for you. If you feel the steering toooo slow with the new tires then I would go right for raising the fork tubes in thg triple trees 10mm or 3/8" ...... then adjust it from there based on how it feels to you. If it still steers toooo slow ...something isnt right in the tire diameter stats above.

Hope this helps and please let us know how it works out and post some pix.

Calling all super techs...........please check the math on this for Chuck and me if you dont mind.

Mike

alimey4u2 · Post by **alimey4u2** » Fri Dec 29, 2006 4:32 am

Excellent calculator here.......

http://www.rbracing-rsr.com/rakeandtrail.html

These are also interesting.......

http://www.tonyfoale.com/Articles/RakeEx/RakeEx.htm

http://en.wikipedia.org/wiki/Bicycle_an ... e_geometry

http://www.sportrider.com/tech/146_0310_art/

Des Brown · Post by **Des Brown** » Sat Dec 30, 2006 8:06 pm

I have fitted these wheels to my 79Z with no problem up front with a 110 80

18 and the rear 140 70 17 and gone from a 630 chain to a 530 with a 18 & 40 sprocket set-up to compensate for the gearing on the engine.

But looking at it now I wish I had gone for a 100 profile for the front

and a 90 for the back this will give you a bigger diameter and reduce the loss

of speedo error and increased engine revs.

I am doing a lot of work on it over winter so I will let you know how I get on.

ps I have a braced aluminium swinging arm so I cannot comment on tyre size for a stock one.

Des

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