Topic: 120/90-18 tire on 2.15 rim

[redgalvin]

 Cant get bead to seat. Did I Screw up? As much work as it was to get it on the rim, I think I'll have to cut it off if it wont work! I'm new at this. Any help much appreciated! Thanks, Red

[Kevin D]

Red, I have a 120/90-18 Bridgestone on the rear wheel of my K1. The parts fiche says I have a 2.15"x 18 rim..... so I'd have to say yes it will fit. Whats your bike??



77CB750 K7

If this is your bike the parts fiche that I looked at says you have a 17" rim. 
That kinda misfit shoulda went on real easy, not difficult.

[markjenn]

120 is right at the limit for what is permissible with a 2.15", but it should work.  Of course, the diameter has to exact - you can't fit a 18" tire on a 17" rim.  BTW, the rim width measure is bead seat to bead seat, not outside of the rim.

Are you doing tubeless or tubed.  On tubeless, you need a compressor that can deliver a fair volume of air - hand pumps or little electric ones often won't work.  Taking out the valve stem helps deliver air faster.

Tubed or tubeless, you want lots of lube and the bead seating area needs to be clean.  (I use WD40 and plastic scotch brite pad to scour the bead seats before mounting a new tire.)  You can overpressure by a fair amount to get a bead to seat - I do 60 psi now and then if I have to, but get very nervous above this.  One trick on a tubeless is to wrap a racheting tie down around the center circumference of the tire to splay the beads towards the rim.

- Mark

[redgalvin]

Sorry guys, not enough information. I laced a 2.15 x18 excell rim to my '77 hub.when I air it up I can't get it to seat evenly around the rim. It's a Conti Tour tire. Thanks for the help.Been messing with it all day. Have even tried tobacco and alcohol. Red

[Flying J]

i use a little soapy water to help create a seal

[Kevin D]

I laced a 2.15 x18 excell rim to my '77 hub

I'm new at this.

I think I'll have to cut it off if it wont work!

If you have laced/trued a rim you are far from a newb. 
But maybe you pinched the tube. What sort of tire tools do you have? Did you use a proper rim band? Did you shorten the spokes flush with the nipples or do they protrude?


I looked at some Excell rim photos.....sweet....got any pics of your work?

[redgalvin]

New rim strip, spokes finished up just below flush with nipples, no pinched tube. No matter how I adjust the tire it inflates with a one foot section low in the rim, not allways the same area of the tire.Bouncing it as I slowly inflate it, same result.Been using soupy H20. Will pick up some commercial tire snot after work today and give her hell again tonight. As for being new at this, I'd never laced a wheel but I've trued bicycle wheels on the machine with a crayon to mark the high spots. I used a wheel stand and dial guage for this job as I have 3+ more wheels to lace. Thanks again, Red

[Industrial Cafe]

i had to grab, and man-handle the tire with soapy water on the lip to get it to seat right.
do this under low pressure, like 10-15psi.
 also, try pushing on the other side a little while you do it.

[rhinoracer]

I read somewhere (Cycle World or Motorcyclist) that using soap to seat tires on aluminum rims will cause pitting to the bead seat. Not the reason why it's not popping but thought it could be useful to know.

[crazypj]

Sorry guys, not enough information. I laced a 2.15 x18 excell rim to my '77 hub.when I air it up I can't get it to seat evenly around the rim. It's a Conti Tour tire. Thanks for the help.Been messing with it all day. Have even tried tobacco and alcohol. Red

 If spokes are not tight enough the rim will still be too large a diameter (a few thou makes a difference)
 Check spoke tension now you have tyre on rim, manhandling it on may have tweaked a few things, if you find any loose re-tighten and true wheel
 Another thing to do is get as much air as possible in there and 'bump' tyre at low spots.
 Anyone who's fitted Avon road race tyres will have had the same problem (I was given an almost new (part worn) pair of AM20/22 18" because guy couldn't get them to seat properly on his rims
They took a lot of effort to get on and get beaded correctly.
PJ

[drdreas]

Red, I have a 120/90-18 Bridgestone on the rear wheel of my K1. The parts fiche says I have a 2.15"x 18 rim..... so I'd have to say yes it will fit. Whats your bike??



77CB750 K7

If this is your bike the parts fiche that I looked at says you have a 17" rim. 
That kinda misfit shoulda went on real easy, not difficult.

Kevin what is the width of the stock rim on the 77k? I have one, and I can't read on the side of the rim what it is, and when I look at the parts fiche it doesnt specify the rim size.

Thanks

[MCRider]

New rim strip, spokes finished up just below flush with nipples, no pinched tube. No matter how I adjust the tire it inflates with a one foot section low in the rim, not allways the same area of the tire.Bouncing it as I slowly inflate it, same result.Been using soupy H20. Will pick up some commercial tire snot after work today and give her hell again tonight. As for being new at this, I'd never laced a wheel but I've trued bicycle wheels on the machine with a crayon to mark the high spots. I used a wheel stand and dial guage for this job as I have 3+ more wheels to lace. Thanks again, Red

How much air are you using to seat the bead? At least the max on the tire. I don't think its unfair to use 150% of the max on the side of the tire. I do. Ask your local shop how much they use.

Of course let it down quickly after the bead pops on.

PS: Don't take my advice on that, get a second opinion, I might be wrong, and it could be dangerous. I called our local shop and the tech was too busy to come to the phone.

PPS: I've done a lot of searching. Some really strange bead seating technologies out there. But common was the idea of using up to 55psi (some said up to 100, I'll stay conservative). But the step I left out was to remove the valve from the valve stem. Then goop the bead up real good, and with the regulator on your compressor set at the desired pressure, hit it with the air quick and pop it on. Once you remove the air chuck the excess air immediately comes out. Then reinstall the valve and air up.  The tire should be perpendicular to your body while airing on the off chance the bead lets go it will blow to the sides and not to your body.

There were many posts talking about seting the tire on fire! I didn't spend any time with them but they were very common. Mostly for larger tires I think. Also included was to wrap the tire with a tie down strap to keep the circumference of the tire from expanding and put the pressure into the bead.

Its certainly best to use the most benign method possible, but sometimes they are a PITA and these methods work.

56psi max: http://www.dansmc.com/tires1.htm
"overinflate till it pops":  http://en.allexperts.com/q/Motorcycle-Repair-837/tire-change-brake-replacement.htm

[Kevin D]

Kevin what is the width of the stock rim on the 77k?

Sorry dr, couldnt find the stock rim width for K7, only that 4.50-17 is stock tire size.


Heres nine pages of parts fiches for different CB750 models, lots of parts pictured:

http://www.cmsnl.com/honda-cb750four_model14344/


Heres also from dansmc, rim width vs tire size chart:

http://www.dansmc.com/rimwidth.htm

[redgalvin]

 :)Success! Got some tire slip from Les Schwab and inflated it to 65 lbs without the valve in the stem. Finally seated! My spokes that were ringing sweetly are now needing to be retightened. Not a dull 'thud', but not a nice ring anymore. Thanks for the help, guys. Couldn't have done it without you! Now to fine tune it and balance it. Red

[tlbranth]

I think it was on Randack's site that I read to use armorall as a tire lube for seating. It works very well with no apparent side-effects. Soap on the other hand will screw up aluminum and suck moisture out of the air to rust spokes and steel rims.

[MCRider]

:)Success! Got some tire slip from Les Schwab and inflated it to 65 lbs without the valve in the stem. Finally seated! My spokes that were ringing sweetly are now needing to be retightened. Not a dull 'thud', but not a nice ring anymore. Thanks for the help, guys. Couldn't have done it without you! Now to fine tune it and balance it. Red

You're welcome.   

[MCRider]

I think it was on Randack's site that I read to use armorall as a tire lube for seating. It works very well with no apparent side-effects. Soap on the other hand will screw up aluminum and suck moisture out of the air to rust spokes and steel rims.

Armorall does work, but the side effect occurs if you're sloppy. If you get it on the tread portion of the tire, you've just about ruined the tire. It willl be dangerously slick and virtually deadly to drive on. Don't ask me how I know.   

[tlbranth]

Good point MC. OK I won't ask how you know.