QT50 Tire and tubes

I found some decent IRC NR 77 70/90 tires and some tubes on eBay. I have read that tubes can be off by a bit...

Aaaand....I don't fully inderstand the wiki for this.

Did I get the correct tubes? It says "60/100-14 2.25/2.50-14 Tire Inner Tube fr 50cc 70 90 110 125 150cc Dirt Pit Bike" for the tubes.

See pics attached


Re: QT50 Tire and tubes

No reason why the tubes won't work, but be aware those tires will scrape on your fender brackets. I've been there- got a brand new set of those IRC tires under the bench cuz I ain't taking my fenders off. They're just a little bit wider than the original size.

Re: QT50 Tire and tubes

I am aware of the IRC Tire rub issue.

I had these type of tires on my 79 QT50. I had to put extenders at the connectors for the fender on the front and had to make a custom fender for the rear, out of a broken plactic motorcycle saddlebag lid.

This time around, I at least have an original rear fender that is going to get modified or replicated.

Thank you for your clarification on the tubes. And thank you for adding to the pool of knowledge that we all cling to, here, in the Moped Army forums.

79 QT 50 with custom fender on the right


Re: QT50 Tire and tubes

My reply is above. It's been awhile since I've been in the Forum (edited)

Re: QT50 Tire and tubes

I was just at a Dunham's Sports yesterday and found some of those add-on plastic fenders that don't look too generic for a 26in mountain bike.

Five bucks! Clearance!

I just put them on my e-bike I finally got done. These seem like they would work for a QT50 with some adjustment and modding.

In case you're thinking about using those tires

Re: QT50 Tire and tubes

Same tires and tube size.


Re: QT50 Tire and tubes

I also encountered a tire and tube issue replacing wore out dry rotted IRC tires on my 1988 Yamaha DT50. I was searching for new IRC tires last year around time of the lock down. I couldn’t find the front tire size any where in stock. Went through eBay listings. Couldn’t find the original front tire size. I ended up buying some Golden Boy tires, reading they were heavy duty and lasted longer than the IRC tires. I bought new tubes to install with new Golden Boy tires. Mounting rear tire took 3 new tube! The first 2 tubes were Chinese, I had too stretch the tube over the rim to get in inside the rear tire, both Chinese tubs got pinched and leaked air. I patched the second Chinese tub and tried reinstalling it only to receive a 3rd pinched tub. I bought a new IRC tub and had no pinched tub. But the tile didn’t look like it was centered good in wheel! The front tire mounted easier and with no pinched tub. But the front tire isn’t centered at all in the front wheel. When I get up too about 35 mph the front tire is so out of round the front forks bounce up and down really bad. Part of the tire is down in wheel and not blown out like it should be. The Chinese tubs didn’t fit wheel and front tire doesn’t fit wheel correctly. I have bought some new IRC tires to install. Haven’t installed the IRC tires yet.


Re: QT50 Tire and tubes

Sometimes a tire needs to be over inflated to seat a tire bead ALL the way around the rim before adjusting to final air pressure. Also, bead lube can help tremendously.

Re: QT50 Tire and tubes

That^ , but , I've also had tires that needed to be physically 'centered' before inflating .

Could be that not all manufacturers use the same ruler . ;)

Re: QT50 Tire and tubes

I tried letting air out and moving the tire and pumping the tire up with higher air pressure. Still didn’t fit any different on wheel. Even tried pulling out on the tire bead that’s stuck down in wheel, it went back the same way. The bead area of the tire is thicker than IRC tires. Maybe it’s more of a rear tire than front. Years ago I had a powder coater do some 3 piece Rupp mini bike 10” Mag wheels. A aluminum color that had to be clear coated with clear powder coat. He didn’t wipe off the wheel pieces before applying the clear powder coating. There was specks in the finish. He had to powder coat the wheel pieces, he didn’t remove the first powder coating, powder coated over the first. It turned out with a great finish! But when I mounted the tires they would fit on the wheels and center up because of the powder coating build up. The wheels had to be sand blasted and done a 3rd time. That’s what makes me think the tire size or bead thickness is the problem. Be a few days before I can get too changing out the tires.

Re: QT50 Tire and tubes

You might try leaving the tires in the sun for awhile before you try to mount them..that does wonders sometimes

Re: QT50 Tire and tubes

Jack Rutherford /

this vee rubber tire is beastly

Re: QT50 Tire and tubes

The wife runs those but they wear faster than my NRC (edited)

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