Supermoto on stock Stark Varg MX

[Erwin P]

Last saturday afternoon i decided i wanted to try a SM session. So i got myself a used leather suit from marketplace, put some road tyres around some KTM MX rims (21-19) i had lying around and had a blast the next morning.

Actually worked pretty well.
Was the only one to show up without proper 17' wheelset with slicks and one of the very few without tyre heaters.
Apart from the front brake getting a little squeezy over time and the grip when leaning in having it's limits it worked great. Well, i had a great time and that's what matters.

Would you guys go for a 3.50/5.00 or 3.50/3.50 SM rim set

 

[Theo]

Your setup reminds me of the Supemoto BigFoots that Gianni Borgiotti, an Italian supermoto rider, who used to be (still is?) almost pro level and still is an instructor, tried to spread years ago; he also competed in the S2 class (for the fastest amateurs and slower professionals) of the Italian Championship in 2014 with those wheels.
Here is a high level race he did like that during the motorcycles show EICMA:

I mean that the riders were high level, the asphalt section of the track not so much.
His idea was to use 19" with certain dirt track tyres, front and rear, to do supermoto and motocross and he said that they were cheaper than slicks, lasted longer and still provided quite some grip on asphalt.

EDIT: I've also found a video I recorded and edited myself during a race he did in a parking lot:

 

[Erwin P]

Funny to see diverent riders actual prever different setups.
But mine was not a preverence. It was the best i could come up with

Still had a great time riding and actually liked riding it better than the fully setup Husqvarna 501 i rode in the video. Especially on the tight stuff the predictible engine brake and power was so much smoother than riding a fully setup 501. For me as a beginner at least.
The 501 owner also rode my bike. Offcourse he was ''very slow'' on the 21-19 road tyres because he was so carefull, but he could very wel see the potentional. Afterwards he talked about selling his and getting a Stark

 

[Erwin P]

Ah yess this is also a little bit of a range test:

Each session i did about 17-18 minutes and used about 25%.
That's incluiding 80hp pulls on the straight, going a 120+ km/h back to 180 degree turn in a few hundred meters. That are about 17 laps of 1 km. So 17km x 4 = 68km range. IF you ride like an idiot full throttle and full braking. For ride style look above.

The EX Enduro street legal version is at a 10% bigger battery, but because a lott of that is netto win and it should be more efficient Stark says it has 20% more range. So 75 to 82km.
However i would expect with road touring you get about 1,5 times as far so 112 to 123km.

Those are very loose calculations, but give i reasonable assumption i guess.

 

[Theo]

predictible engine brake

Did the bike show any tendency to slide because of the engine braking? I guess not, for these reasons:
• It seems to me that, even when set at 100%, the engine braking of the Varg is not so much.
• Something that should be kept in mind when using some kind of BigFoot setup is that the braking force depends on the ratio between the diameter of the wheel and the diameter of the rotor. With a 21" or a 19" rim, even a 320 mm rotor wouldn't brake as hard as it would with a 17" rim.
Similarly, the engine braking would be stronger with a 17" rear wheel.
(The gear ratios also affect engine braking.)
• Less braking force available from the front brake and less braking force usuable anyways because of a low performance tyre means less aggressive braking and therefore less load transfer to the front and less tendency to stay sideways, since during a drift the front end is slowed down to make the rear end tending to overtake it.
• In my experience, low grip tyres also tend to slide roughly, while more sport oriented tyres drift more smoothly.

Not that I am a fast supermoto rider, but in more than ten years of supermoto trackdays with a bike having huge engine brake I've learnt the dynamics of drifting.

 

[Erwin P]

Not because of the engine breaking. I used just 50% and like it very much that way. On a sidenote i had the Stark at 100% on Enduro downhills where it did ''lock-up'' and slide. I would however experiment with the engine brake a bit more next time.
I loved it on most of the track, but adding some would greatly improve breaking at the end of the straight. So i was considering putting engine brake to 100% at the 80 hp map i used on the straight. This would add breaking and get max regen out of it, while using less power with my left hand and less wear. Only concern would be it would maybe upset the bike switching back to 48hp/50% mid corner. I now switched back from 80-48hp, but regen remained the same.

The ratio between disc and wheel sure is important, but a 23% increase in diameter will matter. It's also not ''just'' how hard you can brake, but also how often. A small disc is perfectly able to lock a wheel, but it gets hotter faster. Still you're on point. This however was a very cheap mod. The caliper adapter is just €20 and i've seen people use it. Hard to see how this won't be worth the money or effort

Engine brake would be less strong on the 17 most people are using. With a 160-60-17 you have a wheel circle of 8% more than the 110-80-19 i was using. With the wheel also being way heavier engine braking should be even less.

In the SM braking and drifting department i'm a total rookie so i will take your word for it since it sounds logical. I come from the dirt and apart from some track days at above go-cart track there won't be much SuperMoto for me. Focus will be in Enduro with some casual SM.
And drifting in the dirt is quite the opposite, no brakes, open throttle and go slideways.

I didn't had the courage to do drifting on my first SM day. I had some slide at the end of the straight with a deathgrip on both brakes since i was overshooting it. I was keeping up with someone who overtook me right before the straight. Little did i realise his dual brake setup on gummy 17' would be able to brake tens of metres later