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

I highly doubt you were riding when Scramblers were at their height, let alone when light weight race bikes became available to purchase from the dealers. Scramblers and desert sleds went away simply due to the advancement of lightweight two strokes. Now lightweight high performance four strokes dominate. The key here is weight and ability to un-weight the front end of the bike and that is where the 21" shines. The OP here on this thread is taking about a bike (550 lb 1200cc Sportster) that weighs TWICE what a high performance bike does. A bike with a heavy front end that has a tendency to plow will benefit from a 19" wheel with a wide tire.

IF you were racing back in the day of desert sleds and the big front end heavy Greeves show in my pics, you would know that indeed 19" wheels were far superior. There was a reason they were used, simply because they worked. I know, I speaking from personal experience, I was racing the dez in the 60's and I still race the dez today.

Duh..... no one is racing bikes that benefit from running the 19" wheel any more, but that doesn't mean that when they did race them, they didn't benefit from them. And as you say, NO ONE (not even Mouse or JRC) are racing a 550lb Sporter either.

I don't think anyone argues that the most capable heavyweight off road bike is the KTM 950/990. Service intervals, road manners, and reliability is why many if not most shy away from them and turn towards the GS/GSA. Off road ability is by superior on the KTM and the reasons are suspension and the 21" front wheel.

I did not start my riding lifestyle as early as you, but I did start in 1970 when 19" fronts were the norm. I had a 380 Greeves but mine did not have a leading link fork, it had Cerrianis and 21" front and far out handled the 19" bikes.

Sand and soft dirt is what the OP was asking about on a heavy bike. Sand is similar to water and a flat bottom boat planes above the water, floating, but it still needs a rudder to steer.

Floatation on sand does not make for good steering, there is NO control and if you are trying to use steering input while the tire is floating on sand and it happens to dig in it dives right or left and plows. Look at how many pics there are of GS/GSAs laying on their sides in other threads.

Your arguement is also flawed on the point of heavy bikes being somehow different that the 300# ish 650R that JC rides. My arguement for that would be if a 19" worked better anywhere except the street than Cyril Despress, Marco Coma, and Gaston Raiher would have ALL used on when racing in the sands of Africa on their 500# ish bikes....yet NONE did.

Just because someone is not as old as you or has a different opinion does not mean they know nothing.

OP put a 19" on your sporty ans enjoy the street riding and the occasional hard pack fire road. Follow old farts ideas and ride it in the sand and post pics of it regularly laying on its side....I love those.

OP here.

One of the Sportster models comes with a 21" spoked wheel stock. Not sure if it's a good adv tour wheel, but it's already there and I'll probably try it.

If I understand this thread so far, a 21" wheel is not ideal for the road, especially the twisties. It's probably okay for the highway and non-aggressive riding. The narrow contact patch may want to follow road grooves, or it may not, or it may depend. The 21" wheel/tire will have greater diameter, even though the tire appears to be lower profile than the 19 or 16 inch wheel's tires. The Sportster is too heavy to be lifting the front wheel easily (unless I so overload the weight behind the rear axle, like they did in the Cannon Ball Run Movie....). There is disagreement on the advantages of floating over loose material or slicing through loose material, with slightly more leaning toward slicing through.

I'm building this for long highway trips to off pavement destinations, like Prudhoe Bay and the Trans Canada Ride for example. So, I should consider the importance of safety on the pavement. Is there a braking reduction with the narrow contact patch of the 21" wheel's tire?

In case this little bit of history helps any, Most of my long rides this decade have been on big heavy touring bikes with fat front tires. They just glide down the highway effortlessly. Haven't taken these 900lb monsters on too many fire roads, but they did surprisingly well on the few bad gravel roads I had to take, and on the few patches of dirt my shortcuts demanded.

hi guys,,just happened to cruise the new posts and found this well worn topic,,,

here's a thread that shares the experience of folks having ridden on 19/17 and then tried the 21''

http://www.advrider.com/forums/showthread.php?t=663107&page=2

check out what jimmy lewis one of several adv/dual-sport riding gurus,,i\first american to podium ona bmw in the paris/dakar rallye several years ago,,,test/development rider for BMWs HP-2 project and learn to ride maestro...has to say not to mention his wife Heather even commented on her experience in post #106

http://www.advrider.com/forums/showpost.php?p=19955266&postcount=106

i tend to create solutions that you will appreciate in real world riding....

so tell me/us what ya noticed whe riding your bike with different wheel diameters on different types of terrain....
woody

everyone must already know that there is only a 5-6% difference in mounted tire diameter between the common 19 and 21 DS type tires, hardly seems a big enough variance to make a difference traversing varied terrain, especially on a DS bike, as opposed to a dedicated offroad moto.

the section width of the same tires is a different story, with the variance being over 20%.

so it's unlikely the diameter that accounts for handling reports in mud, sand, etc., the argument comes down to running skinny versus not so skinny.

i like the 19 for running both paved and gravel, does well on both.

regarding my first hi-lighted statement....well as amatter of fact it does make a difference as evidenced by all the positive feedback from those that have actually ridden the various upgrades ...

and the second hi lited staement of yours:,,,,and that is why 90% of the dual sport market is supplied in this configuration,,why we call it our 50-50 set up,,not the ultimate on the pavement or in the dirt,,,hence,,the need to get set-ups that work for your specific needs/riding style /location/intent .

w

woody, maybe i wasn't clear in my statement. do you think the favorable reports on 21" DS wheels is due to the only slightly larger inflated tire diameter or the much smaller cross section tire width, or both?

well for starters the 21 does not have a ''slightly larger'' inflated tire diameter...i just measured several variants of 21'' and 19'' tire diameters...FYI,,,the average 21'' measures 28'' OA as opposed to 26'' for the 19'' set-up...that alone accounts for the smoother ride in the dirt

the 21'' front wheel assy is generically circa one pound lighter than the 19''s.. and with proper choice of hubs/discs/rims have been able to make them 2-4+ lbs lighter...now that is significant because that all equates to less un-sprung weight...which of course makes it easier to loft the front end and makes the ride more supple.

i'll need to get a more definitive ie scientific answer regarding what the narrower rim does [truth is i have customers banging at my door who need my attention NOW] to be cont'd
excuse me for a few,,
woody

BP {the OP} Based on what you want to do with your steed I personally think I would go with the 19" front wheel. Harley did make a 19" cast wheel with like 10 spokes which is tubless, the best way to go for what you want to do imho, but they also made a 19" laced wheel with a aluminum hub and if I remember correctly even an aluminum outer rim ring. You may want to look at any narrow glide front end even like the Dyna std and the Dyna low rider and Dyna sport which may be the aluminum rim model.

If you were planning on doing more dirt/sand/off-road than you describe then I still am with Woody and Jimmy Lewis and his wife, 21" all the way.

Yes you are correct that the narrow contact patch and usually a more knobbie design on 21" tires makes the less steady on pavement. If you are NOT going to run knobbies I would never run a 21" given the option. If I am running a street biased tire I would go 19".

Your original questions on soft dirt and sand and the "floatation" concept has been debunked imho. Only a few dissenters and I will bet they are looking at it from a different angle and not to be disrespectful, but they are wrong.

Here is a pic of a true sand rail, note the differential in tire size front to rear. The front is remarkable narrow for a car. Most even use a blade or fin around the center to act as a rudder as I stated earlier.



JD, you commented on "only" 5-6% increrase in diameter, do you want a 5-6% decrease in pay? That is substantially more than you think it is. The issue is not ONLY diameter, but the amount of circumference that comes with diameter. As Hondos simple diagram shows {while exagerated} the circumference plays a role in that obstacle bridging.

For you pavement based riding with the occasional gravel or graded fire or service access road then the 19" is great. You CAN ride any trail with any size tire, but comfort level and ease is aided by tire size that is appropriate to intended uses.

hardly, 5-6% is exactly what i think it is. the calculated inflated tire diameters are only slightly less than Woody posted, so let's round it up to 6%, of itself not an impressive difference. especially since the cross section variance is a multiple of that number.

woody is correct in pointing out that there are a number of factors involved, including the unsprung weight of the wheel assembly, something i hadn't considered.

i've run plenty of miles off paved surfaces on 17, 19, and 21", so i do know a least a little about how these sizes perform in different conditions.

Here is some sand car tires for sale, again note the narrow design and fin like rudder to penetrate the sand and steer, not big ballon tires to float like you might find on the rear.

http://www.sandparts.com/servlet/th...ires-cln-Turning-Style-Front-tires/Categories

Here are some quad sand tires

http://www.ebay.com/itm/KENDA-DUNE-...Parts_Accessories&hash=item35c18afa70&vxp=mtr

Here is a pure sand tire for a dirt bike

http://www.motorcycle-superstore.co...spx?SiteID=SLI|Front Sand Tire&WT.MC_ID=10010

Here is what I think you need though. It is a 19" Harley Narrowglide front wheel with Aluminum hub and I believe an aluminum rim as well

http://www.motorcycle-superstore.co...spx?SiteID=SLI|Front Sand Tire&WT.MC_ID=10010

JD,
I honestly do not mean to sound argumentative and I honestly think we are saying some of the same things just looking at them from opposite sides kind of thing.

Are you saying that in the OP original question that a 19" tire is "better" in sand?

That goes against what Woody, Jimmy Lewis, all conventional race bikes heavy or light, and most posters here are saying.

I am very much in agreement with you if you are saying that BP "should" run a 19" on his bike for his intended uses. But NOT in agreement if the arguement is that a fatter 19" is just as good or better in soft dirt applications which is all that the OP question was.

Feels like we have 2 different threads sort of.

Thank you for these links.

The last two however are the same link, for the pure sand tire for a dirt bike. Would you be kind enough to post the link for the 19" Harley narrowglide front wheel?

Yeah you've been pretty confused and argumentative the whole time. Relax man, he ain't racing it and he ain't Johnny Campbell or Jimmy Lewis. Its an Adventure Touring bike based off of a Harley Sportster for Christ's sakes. Recommendations have all been for the OP with his particular application. Examples cited were done to prove that they have worked well in the past. Sometimes even someone like you could learn from the past.

no.

what i said was the 21 works better because of the smaller cross section width, and not the relatively small difference in inflated diameter compared to the 19.

woody pointed out that he can build a 21 lighter than a 19, saving unsprung weight and allowing the suspension to work better, also a factor.

i average over 3000 miles/year on gravel and recommended the 19 for a combination of road surfaces, it's what i run. it hasn't been mentioned, but a 19" tire inflated to rated pressure is a wheel saver on rough roads.

No, not in anyway confused about the issue here. Strong Bad, your comment here is completely BS and off of the OP.
It does not matter if he is JC or JL or my 94 yr old grandma who has never ridden. There is NO time when a 110/80-19" front tire is "better" than a 90/90-21" in soft sand on any size or weight bike!

Here is the OP in quote:


pros & cons of a 21" front wheel vs. large 16" wheel/ tire
<!-- #dg-post-title --><!-- message -->Conventional wisdom is dirt bikes have a 21" front wheel with small tire with a meatier rear tire, and large touring bikes have 16-18" wheels with meaty tires on both ends.

Why?

Wouldn't the meaty front tire float as well over dirt and mud as the 21" with smaller rubber? Does it, or is it a weight issue, or a side-loading issue on unstable terrain, or tradition, or something else altogether?

No where does boatpuller state his riding level, his type of bike, or any conditions you are refering too. He does not tell us it is a sportster enduro conversion until the 10th post in this thread.

No one ever wants to admit they are wrong when they clearly are wrong and this time Strong Bad, YOU are wrong. Simple as that. A 21" works better in soft conditions and rocky conditions as myself and many others have stated for MANY reasons.

Narrower cross section makes it cut through soft dirt and sand and steer more like a rudder. No matter bike weight, a lighter weight tire/wheel combo is better, as Woody has stated that is a 21" combo.

JD, you and I are saying the same thing. A narrower cross section like you stated works better because as I stated the cut the sand.

I also have MANY thousands of miles on asphalt race tracks, street riding, back roads, freeway and about the same amount of miles in the desert, MX tracks and and dirt I can find. I am at about 1 million miles NO LIE. 500,000 documanted street miles with odometer equiped bikes and that much again on dirt bikes doing everything from hare-n-hound, scrambles, Grand Prixs, MX racing, a SX series, and magazine testing for MX and Enduro bikes.....100s of thousands of laps ridden.

Strong Bad,
Look back at all of my posts, as soon as boat puller told us what he was building, I definately reccomended a 19" front wheel on a bike like that for his riding level, terrain, and skill level. You and I are in agreement on that and I have always made that assertation and even given him a like to a wheel that will bolt on to his sporty and give him a light weight, strong, laced option in a 19" wheel.

The "floatation" issue is not a valid issue that was raised in the OP, especially on a tire that is likely 20-60mm wider and smaller in diameter and circumference. Floatation would not come into effect until substantially wider and ballon style tires would come in to play like on a "Fat Cat". Then speed and street ability is gone. Even the issue on whether a bike should float on sand has been in question. You can not steer without a rudder even if your boat floats, you must have a rudder to have directional control....same on sand.

I love the back and forth discussions here. However when I am wrong I have admitted it and digressed. I am not wrong this time.

110x18? Nope bigger fatter wider than that! I guess I wasn't the only guy who was wrong back in the day because it didn't work!Allow me to bring in a discussion over on the Dirt Bike History 101 thread after I complemented Deadmanridin on his choice of front wheel:

But then, I've never been there or done that nor have many others As my wife says: "You are welcome to your own wrong opinion!"

I like you Strong Bad. You have a great stick to it-ness about you. Even when wrong yet many times again.

I rode a Hodaka as well. I rode fast. It was capable of being ridden fast. In 1971 I loved it. By 1981 it was antiquated.
By your logic we should all ditch our water cooled, reliable, 12" suspended, aluminum framed, high performance machines for a seizure prone, 6" suspended, noodle framed, heavy for its size, beast just because it was the bomb back in its day.

You have not addressed any of the other places you are wrong....when we found out what BP was building, what the orignal issue was....

You are also very wrong on you size comparisons. WAY wrong. I never said 110-18 as you state. I said, and I quote "110/80-19" " That would be the tire size that is common on many heavy weight dual purpose bikes today like a BMW GS/GSA or the Yamaha Super Tenere or a common size that might be used on a Sporty DS conversion.

You are also very wrong on your size comparison of the tires you show. WAY wrong. Modern tires are measured on the metric system. My 90/90-21" is 90mm wide at the widest point generally when aired up, it is 90mm tall in side profile when aired up and new. It fits on a 21" rim, Not a metric dimension but it is the standard.

The tires you show on the Hodaka and sizes you give are measured in U.S. inches. You forgot the decimal point in your post, but that is ok, you forget alot of things. The tire in question you show is actually 3.50x19" which equates to 3 and one half inches wide and gives no sidewall profile and fits a 19" rim. A metric conversion shows that 3.50 or 3-1/2" converts to a mere 88.9 mm. The tire on the front of my KTMs or YZs are 90mm wide a full 1.1mm wider that your Hodaka tire.

And a common ADV bike tire that as I stated would fit a GS or Tenere being a 110/80-19" would actually be 4.3333" almost a full inch wider than your Hodaka tire. Tell all of the people that have converted their big GS bikes from a 4.333" wide x 19" tire up to a narrower 90/90-21", like Jimmy Lewis AND his wife that the fatter smaller diameter tire is better....you can't.

If your argument is that you Hodaka tire was better because it was wider than a common 21" tire, you are wrong.

You are not the only person to have ridden those bikes. Maybe you are one of the few who are stuck in thos days and think progress has not improved bikes, but again you would be wrong.

I love the old and vintage stuff, but it is in NO way Better than modern stuff. Fun- YES. Historic-Yes. Iconic-Yes. Nostalgic-HUGE Yes.....better- NO WAY.

I will buy you a beer if we ever meet and have a laugh or two with you and not argue, but for now, Come ON man...ever watch MNF? Come on man.

350......3.50 whatever.......we called them three-fifty and we used them because they worked PERIOD no matter what you called them or how they were measured. Those were not modern bikes with tons of HP or suspension. What works on my current race bike (Honda CRF 450) has nothing to do with the OP's scooter. A Harley Sportster is barely a modern bike with modern suspension. (let see you argue that)

Your mistake is you think you know my logic or what I think and as such are out smarting yourself. I'll take that beer and maybe even buy one for you, but only because you admit the OP needs the nice big fat 19"!

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.