CB450 Trouble Mounting Dunlop D404 Rear Tire

Hey guys, I'm finally getting back to work on my CB450 cafe racer project but I've run into an issue mounting the Dunlop D404 120/90-18 rear tire that was purchased for this bike. I can't seem to get the bead to seat on the inner "shoulder" of the rim. The front tire went on with almost no issue. I tired to take a few pics to illustrate the issue I seem to have. The diameter of the bead seems to be 1/4"+ smaller than the rim itself. Is that characteristic of tires that are intended to be run tubeless? I've only ever used tube-type tires on my bikes in the past and they seem to fit much more comfortably on the rim and seem much more pliable. Another issue with this particular tire was that the beads were almost touching because it had been wrapped so tightly when it shipped. I could barely force them apart enough to get the tube in.

Things I've tried so far:

- Removed and remounted
- Over inflated to 70PSI and left overnight
- Deflated, beat the shit out of it with a mallet, re-inflated (multiple times)

If it would stop raining I'd set it out in the sun for the day but is that really going help with such a big difference between the bead diameter and rim diameter?

Any suggestions would be greatly appreciated. I've only had this happen one other time with a Duro rear tire and ultimately the solution was to buy a new tire, same size and model and it went on fine.

Get it on, inflate to 120 PSI and then if it doesn't seat with the pop sound give it a whack fully inflated with the mallet on the tread, It should pop on the rim then. I use Tubeless on mu Tube type rims all the time and I have had that D404 on it once. not my favorite tyre but it did mount right. Last one I did was on the walk of a rental place half way on a 1000 mile trip and it was a Shinko 230. I only had a portable compressor that I could just get 70 PSI and it wouldn't do the "POP" to know it was seated, stood it up and whacked it with a big wrench and "POP" all was good.

Maritime said:

Get it on, inflate to 120 PSI and then if it doesn't seat with the pop sound give it a whack fully inflated with the mallet on the tread, It should pop on the rim then. I use Tubeless on mu Tube type rims all the time and I have had that D404 on it once. not my favorite tyre but it did mount right. Last one I did was on the walk of a rental place half way on a 1000 mile trip and it was a Shinko 230. I only had a portable compressor that I could just get 70 PSI and it wouldn't do the "POP" to know it was seated, stood it up and whacked it with a big wrench and "POP" all was good.

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I'll give that a try this evening, wasn't sure how far I could safely push the PSI. Should I be hitting the tread on the side that isn't seated, or the opposite side? Or all the way around? Thanks!

whack the tread in the center of the tire with it standing up. It forces the beads outward towards the rim.

Maritime said:

whack the tread in the center of the tire with it standing up. It forces the beads outward towards the rim.

Click to expand...

Will do. I'll follow up with the outcome. Thanks again.

One more quick question: would a 110/90-18 have been a more suitable replacement for the old 3.5-18 stock tire instead of the 120/90-18 that I purchased based on the info I found on Common-Motor when I ordered the tires originally?

https://www.common-motor.com/honda-cb450-faq#cb450tiresize

The 120/90-18 that I'm trying to mount seems way too big.

Check Dunlops site, they should list the acceptable rim widths for the size. 12/90-18 can actually vary between tyre models within a brand and Tyre brands too.

Says rim width should be 2.75 so range should be like 2.5-3.0

So that would mean that it's not suitable for the stock 3.50 rim, unless I'm misunderstanding what the measurements are referring to. That would explain why the gap between beads of the tire seemed so small compared to other tires I've run on my own CB450.

Either way, the decision has been made to run more "traditional" tires for the time being. Even letting the tire sit with 120PSI in it over night did not make any improvement.

Thank you for the help.

funny it's listed on their site for such a narrow rim. I didn't like the handling of the D404 on my GL, it was fine on the highway but got almost scary in twisties. Switching it out for the shinko 230 was soooo much better.

If I were choosing tyres for your bike I'd go with Avon Roadriders. Those were excellent tyres on my CM450T.

Thanks for the suggestions. I'll check those out.