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19" front wheel

9.9K views 30 replies 10 participants last post by  fork12  
#1 ·
Tell me why/not I should/shouldn't make a 790 scrambler by putting a 19" front wheel on one?
 
#4 ·
I am definitely not an Australian but I guess both side of the Tasman sea can think a bit laterally.
I want some technical opinion on what problems may be encountered.
I love riding gravel roads but am not an "adventure" rider so don't need 8" of suspension travel and especially don't need a 850mm+ seat height. Most adventure bikes with reasonable power are overweight and way taller than necessary IMO.
 
#7 ·
If you fit a different rolling circumference front tyre to a 790/890 . 2 Things WILL HAPPEN

1) Your SPEEDO WILL BE WELL OFF. The speedo operates from teh front ABS sensoring disk
2) The ABS will probably fail. As there will be a mismatch twixt fore and ABS pulses/second. I DO NOT KNOW THIS 100% for the KTM - But is fully documented for other ABS systems.

There are several 17" Adventure (Mud and Snow) tyres front and rear that fit. Still high speed rated. If I ever get to ride again (COVID and the ruddy weather) enough to wear out the Maxxi's - I will move to M&S almost certainly.
 
#8 ·
I think this could be remedied by putting the 17" wheel ABS sensor ring on the 19" wheel so the bike thinks it still has a 17" wheel? There also seems to be (just) enough clearance for an inch bigger radius wheel and full suspension travel?
I am no motorcycle mechanic. This is why I am asking as there are undoubtable more knowledgeable people on here than me.
 
#9 ·
I think this could be remedied by putting the 17" wheel ABS sensor ring on the 19" wheel so the bike thinks it still has a 17" wheel?
I don't think that will work - the disc has slots cut in it which are used to detect rotation... with a 19" wheel you will have travelled further than with a 17" wheel as each slot moves past the sensor.

If the 17" disc has N slots in it, for a 19" wheel you would need a disc with N * 19 / 17 slots which is probably not a whole number.

The bike's dash processor would really need to know the wheel size and let it do the calculations instead. I doubt that's exposed or supported.
 
#12 ·
Call Burt and see what he says.

Joking aside why would you want to ruin what is one of the best bikes to come on the scene in a long time?

Rather than wreck a perfectly good bike? Go get a dual sport or Adventure bike.

If you would do this for looks, consider that your choice of front tires are very limited. I remember when I had my KTM 1190 Adventure. There were many great tires I wanted to run only to discover they don't make it in a 19 inch size.
Image
 
#13 ·
I don't think I would be ruining it. I would be able to swap out the wheels/tyre combination at will.
I love the 790 as a road bike and if the experiment works I will no doubt end up with two of them. As I said earlier, modern adventure bikes that make half decent power are all overweight and overpriced. A 790 Duke that would rip up gravel would be awesome. The sort of thing I have in mind is a Ducati Scrambler Desert Sled but they are way overpriced for what they are. The Duke is much cheaper, more powerful, lighter, has much better electronics/rider aids and is better speced all round. Why wouldn't you want a sealed road one and a gravel road one?
As far as tyres go I would be looking at somethin 80% road 20% off road so that shouldn't be a problem in 19".
 
#17 ·
And here is a 790 Duke on 17" rims and 20:80 tyres.

6170


I freely confess that this photo truly inspired me. I dont do much off road - but around where my mum lives the roads can be grubby. And here they can turn from perfect to horrendous in a matter of metres. I'd just fit GOOD Dual Road Tyres.
 
#18 ·
Thanks for that info. Yes. I think you are right that a 19" tyre will surpass that range. That's why I am looking into exactly what will need to alter to make it work. A 19" front guard and sump guard will be necessary too. Along with
6171

putting the standard rear fender back on.
I have seen the bike you posted before but I don't think the simple addition of off road tyres (I would call those more 50/50 than 80/20) would make a lot of difference to the handling of the bike on gravel. It is the geometry I am wanting to alter. I used to own a DR650 an do a lot of gravel roads on that. When I first got it the previous owner had been using it as a commuter and had road tyres on it. I rode it like that until I wore them out and then changed to Shinko 705s but didn't notice a lot of difference in grip on the gravel. It didn't spin up quite as quickly coming out of corners with the new tyres and was probably accelerating more quickly but then I am not doing this to make a go fast bike. My aim is to make a bike as fun on the gravel as the Duke is fun on the road. You may ask "Well why not just get a big dirt bike then?" My answer is that a lot of the great gravel roads I want to ride are an hour or more from home so I want to have fun (and be comfortable) on the way there and back too.
 
#19 ·
Think you might want to look at a longer rear hugger to protect the shock and swinger from gravel
I have just fiited a solid sump guard from IBEX in Germany. What Did You Do To Your Duke Today? + Off Topic
Rad guard - I already had.
Make sure a 19" front guard will not clout the rad guard on full compression - I did some measuring a while back looking for space to fit more LIGHTING - but there is very little clearance.

ONE OPTION - though saying such might be construed as heresy - Royal-Enfield 650 Himalayan due in March. The 400 is supposed to be excellent, just too gutless.
I am a wuss so If I was going off road I'd be on something WAY less pokey than a 790. And I'd not risk the cash a 790ADV costs.
 
#22 ·
Think you might want to look at a longer rear hugger to protect the shock and swinger from gravel
I have just fiited a solid sump guard from IBEX in Germany. What Did You Do To Your Duke Today? + Off Topic
Rad guard - I already had.
Make sure a 19" front guard will not clout the rad guard on full compression - I did some measuring a while back looking for space to fit more LIGHTING - but there is very little clearance.

ONE OPTION - though saying such might be construed as heresy - Royal-Enfield 650 Himalayan due in March. The 400 is supposed to be excellent, just too gutless.
I am a wuss so If I was going off road I'd be on something WAY less pokey than a 790. And I'd not risk the cash a 790ADV costs.
Yes. Clearance may be an issue.
Already been down the track of low powered dual purpose. Not my think.
 
#20 ·
My riding buddy has a Husky 701. I got to ride it a while back. Man what a machine.

Very capable in the dirt and decent on the road too. The engine is a real gem. Power delivery is very much like the 790 Duke.

The only real draw back is how tall it is but I guess if you want long suspension travel it just goes with the territory. This is where I think the 790 Duke will suck off road. The shorter travel sport bike suspension will beat the crap out of you off road. This might be ok for a young whipper snapper, but for an old guy with a bad back like me, it's a deal killer.

Good luck with your decision.

Image
 
#23 ·
Yes. Big powerful dirt bikes are great if you want to go off roading but this is my point. I am going to be riding gravel ROADS. I don't need/want 8" of suspension travel. I am not going to be smashing big ruts or getting air. I am going to be drifting it around corners and hitting the odd bit of corrugation. (and hopefully staying upright :) )
I am not a young whipper snapper (57) and I also have a bad back, but I am a light weight (65kgs) and have short legs so something like the Husky (although a great bike) is totally wrong for me. Again, think Desert Sled, but without the price, weight or lack of power.
 
#28 ·
Speaking to a custom shop dealer today who is doing something similar. Though NOT on a KTM.

He wants to upgrade from 19"-17" to 21"-18". Just because he wants to. Not even the factory knows if it is possible. They have however offered to try.
What matters is the frequency slot/noslot/slot/noslot of each wheel ABS disc as it spins AND the relation of these frequencies to each other. But also it seems some ABS systems are very fussy about the amount of metal needed to trigger the detection.

I have seen elsewhere that there is a requirement (in Europe) for a plus/minus 3% per wheel to compenaste for wear and permit alternative tyre choice. This is also specified as a LIMIT in many countries because it does affect speedometers. But have seen that a total variance front/rear of over 5% can start ABS failures. Can this be programmed out? - well that will depend I think on how flexible the ECU software is to modification. I will be pleasantly surprised if it can be done.

The 1290's all share - I think - the same dash/ECU - The 790ADV and Duke have different dash's. Thinking aloud.

Q: With a 790Duke run without the OEM dash?. CANBUS is a bugger at times.

I am actually not disinterested if it works. 790Dukventure could be interesting in so many ways.
 
#30 ·
If you go to spokes - The only spoke kit I have found so far for a Duke is KINEOS - Hideously expensive.

Alpina do kits for KTM but only the ADV's. The plus of Alpina is they use the original discs/sprockets. KINEOS seem to have/need their own sprockets.

I honestly, overall, prefer cast wheels these days. I'm fundamentally lazy with cleaning. And no JetWash near bearings - EVER!.