pros & cons of a 21" front wheel vs. large 16" wheel/ tire

Discussion in 'The Garage' started by boatpuller, Nov 21, 2012.

  1. kellymac530

    kellymac530 motorcycle addict

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    Again SB, you are missing the point of the OP. The question was not about HIS bike, just what would work better in a certain condition.

    I have always contended that a 19" front is the best multi use tire for a moderate dual sport bike.

    As to BPs sportster I do not know exactly what he plans for his suspension. If he is doing anything like JTH sportster then a 21" is still the best option.

    I am really curious though if you have ever tried a 19" tire on your CR450F for the desert?

    I am not sure if you noticed the measurements, but that three fifty actually measures narrower than the 21" on your 450f. Maybe be an optical illusion though.

    I just went out to MY garage and measured MY 1965 Yamaha Ym1 rear tire, which is a 3.50-18 and it measure exactly 3-1/2" and so does the more knobbie looking tire that came off of it. And yes I have ridden it in the dirt. I also measured my airhead R80G/S which has a 90/90-21 and it measures almost 3-3/4" wide although optically looks narrower that the smaller diameter on my old yami.

    If this discussion was whether or not the taller sidewall was better in the dez for flats or pinches...different discussion.

    PS: I love old and vintage things so none of this is because I think old is bad....my daily driver is a 1949 Studebaker truck with a V8 conversion....not a small block chevy like most but a 1963 Studebaker V8 conversion that I did myself. It still runs the stock 3 on the tree with OD and the stock 5.56 geared Timkem split center diff. No A/C. No PS. No PW....my current motorcycles are a '96 RT, an '86 G/S, an '83 Honda POS project and a 1965 Yami Ym1 305cc 2 stroke twin...I obviously love old and vintage.
    #41
  2. Haar

    Haar Adventurer

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    Bio: 63 yrs. old, ridin' 49 yrs. Owned many types, styles etc. From '67 Big Bear to Tenere. Not all that many (serious) miles, just for fun and pleasure. Both sons ride (1-- all over the place, now on Tenere). I rode WABDR with him this summer on my DR650. Other son on DR and Seattle son on Tenere. Also have NX650 (21" front). I live in N. Mich., lots of gravel, sand (some deep). For MY riding "pleasure", I first noticed nice tractability on gravel at moderate speed seemed better on the TDM (that I recently purchased) and that urged me to try the Tenere. (btw: sold FJR - not practical for up here). I really ENJOY the Tenere's handling of gravel, washboard, eroded, some light sand and that it seems to be the ideal bike for my old (titanium hipped) ass. I surely do not have the experience of ya'll, but as an avid rider and fairly analytical of my riding, I can see where the argument for a chubby, 19" front may be the ticket for enjoyable handling in somewhat precarious riding environments. Your analyses are duly noted and I only wish I had done the riding that a lot of you were able to do. Different lives, times, demands. Just trying to help, BP.
    #42
  3. boatpuller

    boatpuller Long timer

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    Finally got to read some unread motorcycle magazines over the weekend, and found a very interesting editorial in the July issue of Motorcycle Consumer News (a bare-bones no advertising fairly technical motorcycle publication I really enjoy. The editorials tend to be very engineering oriented, and thought-provoking).

    The topic was on gyroscopic effects of motorcycle wheels and tires. The biggest contributor to gyroscopic effects, mathematically, is diameter.

    Could the benefit of a 21" wheel in the dirt be the increased stability provided by the gyroscopic affect of the larger wheel/tire at the slower speeds usually ridden off pavement, especially in conditions that tend to cause slippage or side-loading due to the rough or loose terrain?
    #43
  4. kellymac530

    kellymac530 motorcycle addict

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    I believe that article to be true. No single factor makes something work or not work.
    I do know that when Honda tried the 23" front back in the late 70s early 80s that was the issue, very HEAVY steering feel. An example of too much of a good thing. This I believe is also the reason why a street bike with a 21", like a DS bike has a heavier turn in feel and usually requires a bit more counter steer input to make it turn. Not that it handles much worse per say, just more steering input.

    The diameter of a wheel also effects turn in I think effects it in more than one way. A wheel being round that is smaller in diameter will turn a tighter radius with the same input. That is just my feelings, no scienece behind it that I have, just my own experiences. If you drop a washer and it lands on its edge but leaning on an angle it will roll in a pretty small circle, if you MC wheel on its edge {tire} at about the same angle the circle it will roll is much larger. Add gyro effect and you have a genuine formula for how a bike might handle with a 17", 19", 21" front wheel.
    #44
  5. foxtrapper

    foxtrapper Long timer

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    Well, as one who has one of those 23" tired Hondas right now, I can say today that the steering is not heavy on it.
    #45
  6. motu

    motu Loose Pre Unit

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    I've been a gravel road rider all my life, and I used to believe a 21'' was the only way to go....then I realised I didn't believe that at all. This is a bike I rode in the '70's, great in gravel, and got it going the other day...still a good bike in gravel. 3.25x17 front and rear.

    [​IMG]

    Rode this in the '90's, orsome in gravel. 3.50x19 front.

    [​IMG]

    This is my 21st Century gravel road bike. 4.00x18 front and rear.

    [​IMG]

    None of them heavy steering and excellent in gravel. You will notice a theme - Dunlop K70's. It's a lot to do with profile - your modern tyre has a radius, 1/3 will have contact with the road, then the 1/3 on the sides gets used in corners. But in gravel those 2/3d's have stones under them, stopping that central section from getting down to the traction. That's why your bike handles like shit in gravel. The competition trials tyre that those desert racers had on are a similar cross section, and get down and hook up.
    #46
  7. Solo Lobo

    Solo Lobo airhead or nothing

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    Having ridden tons of highway miles on my 21" wheeled G/S and GS I would say that sucking is an overstatement if you are running today's street biased knobbies (ex: TCK80). While the smaller front wheels of the street bikes I have owned are certainly better, the 21" front does not limit my riding.

    I'm not really that slow, but I certainly don't operate well above posted limits any longer.

    If I was going on a long trip and expected to do dirt, I would (and do now) go with the 21".
    #47
  8. tHEtREV

    tHEtREV Captain Awesome... tEAM iDIOT.

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    Slightly of topic, but aren't speedway bikes using 23 inch front wheels?

    For a bike that is never really going in a straight line on nicely groomed tracks I thought they would benefit from a smaller tyre... :1drink
    #48
  9. PeterW

    PeterW Long timer

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    My experience was that it's mostly diameter and the fact that 21" fronts tend to be narrower. Don't get me wrong, I'm sure there is a gyro effect, but it's rolling over shit rather than climbing and/or sliding sideways that made the biggest difference to feel.

    Overall the bike I have now with a 19" front is faster and more stable on gravel than the lighter 21" dirt bikes I used to ride, well, until the size of the lumps goes up, then it gets unpleasant.

    Pete
    #49
  10. ibgary

    ibgary Been here awhile

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    Have you thought of looking for a Buell Ulysses? 1200 engine, good suspension, about 500 Lbs.

    I wish I had bought that instead of my XL1200R. I looked at them both. Now I'm on. GS @ 420 Lbs.
    #50
  11. cleatusj

    cleatusj Dirt floor engineer

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    Size ......... Dia. Width
    120/90-18 26.5 4.69
    110/90-19 26.81 4.29
    90/90-21 27.36 3.54

    Just one brand of tires for Harley fronts. Not much difference in height.
    #51
  12. boatpuller

    boatpuller Long timer

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    Yes, I have. Even found one at a dealer to test ride. Have never wanted to end the test ride and return the bike back to the dealer more than I did on that Ulysses. And that surprised me greatly. Had expected to love it. Can't really ID why it was such a bad "fit" for me, but it was.
    #52
  13. markk53

    markk53 jack of all trades...

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    "Scramblers" back in the 60s and early 70s were high piped street bikes like the new Triumph. They sucked when taken truly off the beaten path.

    21" wheels have been in use since the early days of serious off roaders. Even the big old thumpers mostly had 21s. As said, they roll over large bumps and across ruts, they cut into soft terrain getting traction down deep, and are lighter for lofting the front wheel or planing off over rough ground/sand. The front tires come in at 3.00, but there are 2.75 and in some cases around 3.25 or so. The narrower tire is good for lighter smaller bikes the fatter tire helps a bit for desert where rocks can be damaging and a bit of floatation without totally sacrificing the knifing effect of the narrower tire. It is a compromise. Desert sleds used to do 19s, but now have gone back to 21s for the most part, supercross did a 20" front wheel for a bit too. Honda tried the 23 for off road and dual sport back around 79, but it was too much. The 21 worked better and there was wider tire selection available.

    Same has happened with the road going wheels for sportier rides. The 16 on road racers and then on the Interceptors started it, but eventually it shook out to the 17 being the best all around for the more sporting bikes. Tire widths have done the same on sport models sticking at no wider than 120 and going 110 on some smaller displacement bikes. The 18 and 19 seem to go for the cruisers for sure and the adventure bikes that do more road use. They are heavier than the 21, roll over bumps better than the 17s, a good compromise for the riders that are leaning more to the Adventure type riding that entails a lot more road. I think they probably are better for the really heavy bikes too, over the 21, but that's a guess.

    Wheel size choices, in the long run, are a choice for the rider. Evidence may point to a size as best, but it is the rider's choice in the long run - they have to ride with it and whatever trips their trigger.
    #53
  14. Strong Bad

    Strong Bad n00balicious

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    Yeah right!! I suppose none of guys like Mike Burke were serious:

    [​IMG]

    Narrower 21" wheels were much better than 350 or 400 19" in the rocks, but you obviously have never been on a desert sled in the soft stuff with a 275 21". The 19" floats, the 21" dig in as you said. Later on the lighter bikes (big bore 2 strokes) the 21" was (and still is) the way to go.

    But to say that those who came before you were not serious is ridiculous at best.
    #54
  15. markk53

    markk53 jack of all trades...

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    Bad wording on my part. "Serious off roaders" meant the motorcycles, not the riders. If you read it a bit more carefully you will see in context that serious off roaders were bikes built for true off road racing. Bikes like the Lito, Husqvarna, and other 500 singles. They frequently had 21" rims back in the 60s, probably even in the 50s. It was the motorcycles, not the riders. Even Honda and Triumph eventually stuck 21" rims on the front of their SL350 and Trophy 500 respectively.

    [​IMG]
    [​IMG]

    Burke had championships on Triumphs up to 1974, the years when a lot of desert riders still ran 19" rims and modified twin cylinder street bikes. As you say, lighter two strokes made the 4.00-19 obsolete.

    I mentioned the 2.75 being for smaller bikes and in addition I should have mentioned trials bikes. The 3.25-21 was the desert tire when it was around. A bit better than a 4.00-19.
    #55
  16. Strong Bad

    Strong Bad n00balicious

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    Sorry, but Mike Burke never held a championship and he only raced up to 1974, the lowest number he ever earned was 9 in the open class in 1970. By 1970 most of the big desert sleds were gone. I know, I was there in 1970 with a class win at Barstow to Vegas with a 21" on my 125cc:

    [​IMG]

    [​IMG]

    Even though us 125cc and above guys started using 21" wheels, many of the the 100cc guys (aka: Trail Bike class) continued running 350x19 fronts, again to try to float on top of the sand and not plow.

    But I digress,

    Serious off road bikes like the BSA Catalina Scrambler?

    Feets Minert told MX action about his 1956 BSA Gold Star that BSA based the Catalina Scrambler on:

    "I used a front brake backing plate with a scoop for additional cooling and ran a 19-inch front wheel instead of the standard 21-inch wheel preferred by the English riders,” says Feets."

    [​IMG]
    #56
  17. markk53

    markk53 jack of all trades...

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    Yeah, I didn't read it close enough on Burke, I just saw he ran mainly Triumph during the desert sled days and also rode a Baja 100 Harley once or so.

    You like names, how about Jeff Smith? Jeff Smith did quite well on the Gold Star winning the FIM championship with it. So yes the Gold Star was quite serious when set up with the appropriate wheels and tires. He didn't run a 500 twin or 650 twin, not a serious off road bike for those uses and eventually not for any racing uses other than flat track or road racing. Husqvarna and Monarch were big four stroke singles in serious dirt use, using 21" wheels. That was the way they developed for hard off road use in Europe and that translated well to most U.S. riding as well, the one exception being the desert, at least in the view of some desert riders running big inch twin street bikes. Husky and others actually installed 19s on some of their bikes, possibly to market that direction, but mainly for the flat track and scrambles/TT.

    The Gold Star was on par with all the other short travel bikes of that time as shown by the Lito. Sure it had a headlight and tail light, but its intent was racing both road and off road. In case you don't realize it, the same was true with Bultacos, running same or similar frames for racing. The Bultacos, which were considered quite serious in a number of styles of racing used essentially the same frame set up save for a gusset or two and head angle on the Pursang, Sherpa S motocross, Sherpa S scrambler/TT (I had one for scrambles and short track, trying to loft that pig of a 19" tire was quite the challenge), Sherpa T, and Metralla road bike/racer. The same basic frame for motocross, short track/scrambles/TT, trials, and road racing. As road bikes they were light, but buzzed like crazy as I found with my Metralla I had and the Sherpa T when I had it licensed.

    As for Feets Minert, a fast and respected rider, he was an old school U.S. west rider running a 19". He eventually was running 21" wheels on his Victors in later years. I bet a lot of riders ran 19s until the first time the Europeans came over in 1968 and trounced virtually every one of them. One of the races was run at Mathias Raceway in New Philadelphia Ohio at the time. DeCoster, Robert, Wolsink, Mickola, and others showed the way it was done - with a 21" wheel on their bikes too.

    You can pull all the old desert racers out to parade how great they thought a 19" front wheel was, but dirt off road racing history from California to Dakar has proven the best for all around use was the 21". Except, of course, flat track and scrambles/TT, which still use 19s, but that might be more tradition than need, not sure. Maybe plodding along with a heavy twin cylinder street bike made one need a fat "bumper" on the front of the bike to bulldoze the way rather than finesse it like a 21 allows.
    #57
  18. Strong Bad

    Strong Bad n00balicious

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    That was pretty obvious and I give up trying to wade through your verbose responses trying to figure out if you've worded something badly or if you you weren't pay attention before becoming a Google research expert.
    #58
  19. markk53

    markk53 jack of all trades...

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    Wasn't google, I started with bikes in 69-70, made a living in the industry for 7 years full time and 15 part time, so I remember a lot. Just figured the pictures would aid your understanding.

    I didn't know I'd have to write down to your level. I'll start thinking of you as working at my middle school students' level then try to write my posts so one of them could understand it. Maybe that will help you will understand more.

    So I guess you are right, all dirt bikes should cut the crap with the 21 inch front rims and go back to 19 inch front rims. Feel better?
    #59
  20. Strong Bad

    Strong Bad n00balicious

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    I'm not one of your students, so come off of your teacher high horse. I never said 19" was the best for all bikes. The point you are missing is that in some applications (as in desert sleds or other heavy bikes) a 19" wheel has more than proven it's preference by many in years past. I even posted a pic of me on my AT-1 with a 21" and made a point of saying so. Why do you teacher always get your panties in a wad so easily?
    #60