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Discussion Starter #1
Been considering building a front wheel dedicated to road use, with a 19" rim. Has anyone done this, and if so could you post pics of the wheel on the bike?

Thanks
 

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Not sure if this would even work,it may upset the geometry of the bike for the worse.
It will turn in quicker as your making the steering angle more aggressive but like I said I'm not sure if this would be a good thing.

I know they drop 17" wheels into dirt bikes to make supermoto's.

I personally think you might be better on spending the money on the standard suspension and making that better instead of possibly wasting money on building a wheel which could make the bike dangerous.
 

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Been considering building a front wheel dedicated to road use, with a 19" rim. Has anyone done this, and if so could you post pics of the wheel on the bike?

Thanks
I think you should order a rim and spokes from Buchanan's, put a fat tire on it and tell us how it works. I did the same on an XR650 and liked it. Of course I am an old flat tracker, like you...
 

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Discussion Starter #4
I think you should order a rim and spokes from Buchanan's, put a fat tire on it and tell us how it works. I did the same on an XR650 and liked it. Of course I am an old flat tracker, like you...
I built one for the KTM 950 Adv that I used to have and it worked really well on the street. The main thing I'm concerned about is if the front fender will work with it. I'll dig up a 19" tire and see how well it fits in there before going any further with the project.
 

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I built one for the KTM 950 Adv that I used to have and it worked really well on the street. The main thing I'm concerned about is if the front fender will work with it. I'll dig up a 19" tire and see how well it fits in there before going any further with the project.
After seeing your pic of Gary Nixon, I figured you were thinking how great the 19 would work for TTing on dirt roads. I already tried putting a 120/70-21 on mine but it rubbed the fender. Rugged Roads offers some fender lifting brackets. I am thinking of biting the bullet and go with a high fender. Then I can do whatever I want with the front wheel.
 

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Discussion Starter #6
After seeing your pic of Gary Nixon, I figured you were thinking how great the 19 would work for TTing on dirt roads. I already tried putting a 120/70-21 on mine but it rubbed the fender. Rugged Roads offers some fender lifting brackets. I am thinking of biting the bullet and go with a high fender. Then I can do whatever I want with the front wheel.
You're assumption isn't far off. Though I'd set up the 21" with a knobby, I'd also set up the 19" with something in the area of a 50/50 tire for street and fire roads. These big Adv bikes are marginal for hard core single track and hill climbing (for us mortal riders) but make awesome sideways fire-roaders. But what really got me starting seriously considering a 19 on the front were the moments when I was hot dogin' a bit on the pavement and felt the front end start drifting more than the back end. Not a comforting feeling.

BTW, good on you for recognizing Gary Nixon. For those of you who haven't seen the full size version of this pic, he's in a full-lock power slide while sticking his tongue out at the photographer, at about 80 mph. He was an amazing (and a little crazy) racer.

Are high fenders available for the AT?
 

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Curious if there has been any update on this. I found an OEM hub and spokes I'll get from Buchanans, but need help with a 19in gold front rim 36 spoke. I looked at the Excel Taskago gold ones, but they are running about $200/rim. Sound about right, any better options out there? Then I was just going to lace it up myself.

My thought is to only have a "sport" front wheel, then swap the knobby 21, and spoon on a knobby 18 when I want to do some real off road. 90% of my weekly riding is sport touring, but on the long weekends and holidays I want to get as lost as I can in the woods. I have all tire changing tools at my house, and with tube tires it makes it a bit easier.

I did some figuring, and found that with a 160/60-18 rear and 120/70-19 front, the rear wheel speed will be off by just a bit (160/60 is a slightly smaller diameter compared to a 150/80) (you'll be going slower than the speedo reads) and the traction control will be less intrusive at all settings (allows more wheel slip) (going to a smaller wheel means it is spinner faster going the same indicated speed as the 21in wheel, and as such the rear wheel will be spinning slower. TC works in that it kicks in when it detects the rear wheel spinning faster than the front)

ABS should be okay, it might kick in a bit sooner, but the way the AT ABS works is that is engaged when the wheel is sliding (so not spinning) and shouldn't have any affect on a faster spinning wheel.

My plan is to do pirelli Angel GT tires front and rear for the *sport* setting and Mitas e-10s (or something similar) for the knobbies.

Anyway. I didn't want to get two full sets just yet. Maybe down the road I'll get a set of the Alpina Tubeless, but I didnt want to drop that cash on them without trying different wheel sizes first. I also didn't want to stray too far from the OEM rear tire diameter (ie a 17in wheelset)

The Africa Twin is such a versatile bike, I just wanted to push it into an even more versatile direction. Hair scrambles, ADV touring, Sport touring, supermoto, wheelies, skids. This bike can really do it all. I'll keep you guys posted on my progress and search for the right rim/spoke combo.
 

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Discussion Starter #11
I didn't have a 120/70-19 to test, but did have two other 19" tires for measuring. Compared to the OEM 90/90-21, a 100/90-19 will be about 1/4" wider and 1/4" lower. This should fit the bike, but the gain in width was so little that it didn't seem worth the cost and effort to build a 19" wheel for doing this. The other tire I measured was a 110/80-19. It dropped the bike 1 7/8" and is about 5/8" wider. I see more potential for a performance increase with this size, but it's too wide to fit inside the inner portion of the front fender, so would require considerable modification to the fender or going to a high fender. It would be interesting to hear how the 120/70-19 would compare with the OEM 90/90-21.
 

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I was leaning toward the 120/70-19. That paired with a 160/60-18 means the OD of both wheels(and tires) will be within 0.2% of eachother for the same diameter. This should give the bike a more neutral turn in and be a bit easier to move around. Currently the front axle rides higher than the rear, due to the larger front wheel. (gives it a "speed boat in water" turning feel). An axle that rides higher in the rear means faster turn in. (think 16.5in wheel on supermoto bikes).

Good to know that the front fender wont clear. I'll have to make a new bracket and fender for it. Might forego the high fender, I think it could be easier to make a bracket and mount a small plastic one. (think cafe racer minimal style).

Haha sometimes there is just too much time to think and tinker with everything!
 

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I don't why you're considering a 19" front, my AT is stock currently running continental TKC 70 tires front and rear. I have scraped the pegs and bottom right side frame numerous times on various twisty roads this machine can carve some corners, the 21" front works great on this bike
 

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I'd love to see how the 19” 120/70 goes, been thinking about doing this myself when funds allow. My only concern is the effect it'd have on the ABS, but if it works the way you say, then great! Have you see the front fender rise kits from rugged roads? Hopefully something like that would help?
 

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I dont think it will be too pricy for the front wheel. $150 for the front hub, $200 for a rim, and $150 for spokes/nipples? $500 for a front wheel isnt awful. I am leaning towards the AltRider high front fender kit, so I wont have to worry about tire clearance. Dubya quoted me $1600 for a 17/17 set, and $700 for just a 19in front wheel for reference. I spent a little too much on other upgrades, so this has taken a back seat until later in the season....haha
 

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Rally Raid have a number of rim options including a 19/17 option. I think ProCycle have a 19 front they are building now as well. From all reports the front 19 does give better front end turn in and feel than the 21. Have not had an answer on if a 19/18 combo works Ok with the ABS and TC.
 

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I was speaking to Rally Raid this week re tubeless and the 19 and 17 inch combo was mentioned - they have a demo set on a manual and want to try them on a DCT - to check gear changes etc - I have volunteered my bike so will see them in near future, try them out and if good may well ride away with them.
 

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I think ProCycle have a 19 front they are building now as well. From all reports the front 19 does give better front end turn in and feel than the 21. Have not had an answer on if a 19/18 combo works Ok with the ABS and TC.
Yep. The wheel is built and I have word that my Cogent Dynamics suspension parts are at the shop waiting for me. I'll be getting back to the shop in Oregon in about 2 weeks and top priority will be putting the bike together and getting in as much test riding as the weather allows. I should have a solid answer about the ABS and TC before April.
 

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I really don't think it will be an issue. A 19/17 combo is going to give you basically the same ratio of rev/mi as the 21/18 (either in a 110/80 or 120/70-19 tire) so the bike TC and ABS will work the same on the 19/17 as the 21/18. See my attached spread sheet below for calculations based on tire diameter and front and rear wheel speed sensors (FWSS and RWSS). The stock calibration is around the 0.959 ratio. 110/80 and 120/70 are 0.965 and 0.977 respectively and should have very little affect.

The tricky bit comes in running a 19in front and 18in rear. The wheel speed sensors will be reading that the front wheel is rotating faster than it should be (per the stock calibration). You can think of this similar to backing it in or excessive engine braking, where the rear is spinning slower than the front. This means the ABS rear will kick in sooner, but the front ABS will kick in later. Again the front is spinning faster than the rear, so for the front ABS to kick in, the front needs to be spinning slower than the rear. The wheels are not really spinning faster or slower, but this is what the WSS will be reading.

The Africa Twin has two systems for the front and rear (which is why you can turn off the rear, so they work both together, and independently) so they can and will act differently in these scenarios.

Say you are traveling at 30mph. Your rear wheel speed sensor (RWSS) will read as normal at 6.3983 rev/sec. The front WSS expects the front wheel to be spinning at 6.1388 rev/sec. But with a 19in front wheel (for this example we will focus on the 110/80) the wheel will be spinning at 6.4818 rev/sec. The computers in the bike will say ‘hey! This front wheel is spinning 0.3430 rev/sec faster than it should be!’ (or looking at it the other way, the rear is spinning 0.3430 rev/sec too slow – TC).

When the rear brake is applied, the computer thinks the rear is spinning too slow – approaching skid – so it will kick in. The front on the other hand will think that it is spinning too fast, and wont do anything until it detects a skid at the front wheel. So ABS will still function, but it will be less intrusive at the front and more at the rear….so good thing it is easy to turn that off.

Now – traction control. This only affects the rear wheel (engine output). The 19/17 will again not be an issue. On the 19/18 Since the RWSS is reading that the rear is spinning slower, it will not kick in until the rear is spinning faster than the front. Going back to the 30mph example. Say you give it hard acceleration and you break the rear loose with the TC fully on (3 bars) the sensor at the moment it breaks loose will not register it as an issue until the rear spins faster than the ratio. The front will be at 6.4818 rev/sec but the rear is only at 6.3983 rev/sec. The ratio that the computer expects is 0.959, so until the rear is spinning at 6.755 rev/sec (31.26 mi/hr) it will not kick in. Thus the TC will be less intrusive with a smaller front wheel. This applies at all settings.

And after all this, you will not need a speedo healer because the speed is read off the output sprocket. (unless you re-geared). 3

TLDR: A 19in front wheel will have less intrusive front ABS, and TC. And it will have more intrusive rear ABS. A 19/17 combo will need a speedo correction (smaller wheel at rear so you are traveling less distance with each revolution, similar to a re-gear).

Hope that is helpful!
 

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Do you even know for sure that the ABS computer compares front/rear rotational speeds?
My assumption is that it does not. It only calculates changes in wheel speed at each wheel independently.
Lets say I'm riding on gravel and I have turned off the rear ABS. Going a little hot into a corner I lock up the rear. I'm pretty sure the front ABS still works in that situation.

For what it's worth, running a 19" front wheel on my KTM990 Adventure did not have any effect on the ABS of that bike.

I know most automotive ABS systems compare wheel speeds but cars do not have independently operated front and rear brakes.
 
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