R100RS tire sizes

[plehman]

The tires on the new to me R100RS from 1981 are 8 and 9 years old. Plenty of tread, but too old and hard as a rock. Metzlers

The front says: 3.25 on 19inch. I assume that's 100/90 but that designation isn't on the tire.

The rears say 120/90 on 18in. But J&P Cycles says that tire doesn't fit my model, claims it should be 110/90.

Any suggestions?

Then of course there's the religious discussion of brands... I'm thinking the Shinko 712s

 

[20774]

Your bike came with a inch-sized tires, 3.25x19 up front and 4.00x18 in the back. I strongly suggest that you go with inch-sized and not metric. I can't believe that a 120 tire is on the rear...that could very likely be near rubbing on the swing arm housing and will be tough to get past the rear shock and brake.

Michelin Pilot Activs get good marks...in inch sizes. The bead is a bit tough to install...will need a machine for sure.

 

[beemerphile]

The front says: 3.25 on 19inch. I assume that's 100/90 but that designation isn't on the tire.

If the 3.25x19 were stated as a metric tire, it would be 90/100-19. Such an animal does not exist. A 90/90-19 tire is the right width, but the sidewall is shorter. A 100/90-19 has the correct sidewall height but is too wide. A too wide tire handles poorly on this bike. People used to cram 3.50x19 tires on the front of these bikes for some unknown (bigger is better?) reason. It turns the rubber cow into something that handles worse than a rubber cow.

I agree with using 3.25x19 and 4.00x18 inch sized tires on these bikes. Bikes are designed from the tires up. If you change the tire size, congratulations, you are now the bike designer. But good luck beating the guy who had control over all the other variables that go together to make the bike do what it does.

 

[plehman]

Thank you. Great advice. So many ways to make mistakes...

 

[ccolwell]

Your bike came with a inch-sized tires, 3.25x19 up front and 4.00x18 in the back. I strongly suggest that you go with inch-sized and not metric. I can't believe that a 120 tire is on the rear...that could very likely be near rubbing on the swing arm housing and will be tough to get past the rear shock and brake.

Michelin Pilot Activs get good marks...in inch sizes. The bead is a bit tough to install...will need a machine for sure.

You can install them without a machine. Not that I would ever try to do so again...

 

[beemerphile]

You can install them without a machine. Not that I would ever try to do so again...

They are brutal with tubes (twin shock applications). I take my Pilot Activs to the local motorcycle shop for my R75. For the tubeless Pilot Activs on my 1992 R100RS (monoshock application) I can do them myself.

 

[pglaves]

They are brutal with tubes (twin shock applications). I take my Pilot Activs to the local motorcycle shop for my R75. For the tubeless Pilot Activs on my 1992 R100RS (monoshock application) I can do them myself.

Meaning that if you get a flat tire you will soon have the bike on a wrecker. So plan accordingly.

 

[lkchris]

Your bike came with a inch-sized tires, 3.25x19 up front and 4.00x18 in the back. I strongly suggest that you go with inch-sized and not metric. I can't believe that a 120 tire is on the rear...that could very likely be near rubbing on the swing arm housing and will be tough to get past the rear shock and brake.

Michelin Pilot Activs get good marks...in inch sizes. The bead is a bit tough to install...will need a machine for sure.

Just to expand on this (with which I agree 100%)

There are NO metric equivalents to 3.25-19 and 4.00-18

If a particular brand does not offer these sizes, that brand does not offer tires for Airheads. Why would you want to fight this? Every bit of the design engineering for these bikes was done with these size tires and you cannot do anything but detract from that by installing nonspecified tires.

These original tires were bias ply, not radial. Only Continental has gone to the trouble of designing a radial tire for Airheads in the proper sizes.

Your bike did not come from the factory with wheels with features for safely securing tubeless tires and therefore you must use tubes ... whether mounting tube-type or tubeless tires. You can't blithely make a modern motorcycle out of these vintage bikes by fitting modern equipment ... shade tree engineering isn't engineering and anecdotal evidence does not supersede engineering design and testing.

Since you have to install tubes in any event, you'll be better off finding tube-type tires. They will be much easier to fit and your chances of repairing them on the road is much greater. This will be difficult and you'll likely have to find them in Europe. This is simply the cost of doing business when running a "historical" or "vintage" motorcycle. Lots of folks are in denial regarding this.

The tire situation for Airheads was modernized by BMW with the K-bike based models from '87 on. None of that fits the earlier bikes.

The USA is a third world country with respect to things automotive ... in Europe Airheads are still approved for road use because original specification equipment is still available (and required). In the USA, "vintage" equipment is simply left behind save for just a few specialist suppliers and of course there's zero/zip/nada in the way of regulatory inspection and enforcement. It's the wild west. Don't ever think motorcycling is cheap.

 

[lmo1131]

Gosh, this topic has been kicked around forever, it seems; so many times, in fact, that I've lost track of what's available.

Is there an "airhead suitable" tire brand cross reference chart?

 

[20774]

Is there an "airhead suitable" tire brand cross reference chart?

Lew -

I think asking about a brand gets more into the personal choice in terms of how a tire handles, sticks in the corners, runs in the wet, etc. That's all very subjective.

I don't have access to brochures or rider's manuals across the years, but from Phil Hawksley's site, it would seem that generally twin shock models came equipped with inch-sized tires. When the monoshock bikes came out, they were shod with metric tires. So, if you're looking for tires for a pre 1985 bike (again, generally speaking), any brand that offers inch-sized tires is what should be looked at.

I've used metric tires on my /7 and while they "felt" OK for my style of riding, the fact that they don't have the profile and are at least 0.5" smaller in diameter, my sidestand wouldn't function properly anymore. The bike sat closer to the ground so it sat more upright when on the sidestand...so much so that it fell over at a gas stop years ago. That's when the light bulb came on for me...no more metric tires.

 

[pglaves]

Lew -

I think asking about a brand gets more into the personal choice in terms of how a tire handles, sticks in the corners, runs in the wet, etc. That's all very subjective.

What is needed is simply a list of current tire brands and models available in the specified inch sizes. Then folks can argue their merits, but figuring out what is available needs to precede any such interesting discussion.

 

[m_stock10506]

What is needed is simply a list of current tire brands and models available in the specified inch sizes. Then folks can argue their merits, but figuring out what is available needs to precede any such interesting discussion.

You can go to the web site for American Motorcycle Tire, and you can shop for street tires by size. They list 11 tires in 3.25-19, 11 in 4.00-18.

https://www.americanmototire.com/street-tires/?

Michelin Pilot Activ, Metzeler ME11, Metzeler Lasertec, Avon Speedmaster, Avon AM26 Roadrider, ContiGo, Dunlop K-70, others

 

[pglaves]

You can go to the web site for American Motorcycle Tire, and you can shop for street tires by size. They list 11 tires in 3.25-19, 11 in 4.00-18.

https://www.americanmototire.com/street-tires/?

Michelin Pilot Activ, Metzeler ME11, Metzeler Lasertec, Avon Speedmaster, Avon AM26 Roadrider, ContiGo, Dunlop K-70, others

Thanks. I think I will go there and write down the list for next time this thread comes up.

 

[beemerphile]

To add to the confusion, some of the 11 are rated tubeless, some tube type, some tube/tubeless, and some don't say.

 

[20774]

IMHO the tube/tubeless nature of a tire is less important (to a point) than the tire size. With limited exceptions, I don't think anyone would have a problem using a tubeless tire on a tube-type rim...sometimes that might be all you can get. Since the inner tube is your key defining factor with the tire/tube mounting, the nature of the tire is something of a secondary factor. I'm not a tire engineer, but I'm thinking that the rim profile for a tube-type rim will handle the bead on a tubeless tire. I would personally not go the other way...using a tube-type tire on a tubeless rim. The tube-type rim is not designed to grab the tire bead in the same way as the tubeless tire rim will.

 

[pglaves]

IMHO the tube/tubeless nature of a tire is less important (to a point) than the tire size. With limited exceptions, I don't think anyone would have a problem using a tubeless tire on a tube-type rim...sometimes that might be all you can get. Since the inner tube is your key defining factor with the tire/tube mounting, the nature of the tire is something of a secondary factor. I'm not a tire engineer, but I'm thinking that the rim profile for a tube-type rim will handle the bead on a tubeless tire. I would personally not go the other way...using a tube-type tire on a tubeless rim. The tube-type rim is not designed to grab the tire bead in the same way as the tubeless tire rim will.

Sometimes the interior of a tubless tire is rough to the point it might abrade the tube while flexing. I would be happiest with a TT (Tube/Tubeless) tire if one I liked was available.

 

[20774]

So now we need to add interior roughness to the criteria? Sheesh! Where do I find that stat on the tire websites?

 

[pglaves]

So now we need to add interior roughness to the criteria? Sheesh! Where do I find that stat on the tire websites?

You don't. But that is part of the Tube/Tubeless info builders put out. I recall buying a tire - I don't remember the brand - that said do not use a tube in this tire.

 

[20774]

You don't. But that is part of the Tube/Tubeless info builders put out. I recall buying a tire - I don't remember the brand - that said do not use a tube in this tire.

Never seen that before. Bought a lot of tires/tubes in my career...not as many as you, though!

 

[khittner]

You can add Heidenau tires to the list, with several proper inch-sized tires for front and/or rear; most look like Metzeler knockoffs. http://heidenautires.com/vintage-motorcycle-tires/

I have not used them myself on either my RT or Vespa P200, but their scooter tire offerings are typically thought of as being the top of the heap in the vintage scooter community, FWIW.