Question for the Dyno guys?

[Chopcor]

Why does a 240 tire on a Gen 2 negatively affect the power output versus the stock 200 tire if they are very similar in diameter?? Have seen multiple cases where the bike put out less rwh with a 240 and am not understanding why?

 

[marsmax85]

I had heard it will drop 6 to10 horses Probably due to the weight of rim and tire .

 

[Traumahawk]

I wonder if it can increase the rolling resistance due to the width of the tire?

 

[customizedcreationz]

All of the above. More rolling mass generates more friction and more width generates more friction.

I was told when I dyno'ed my turbo bike that I could lose up to 20 hp with to soft of a tire. That it will spin on the dyno easy. As luck had it I just mounted a Shinko ultra soft brand new on the bike the day before.

I was told to get an old hard tire and that will give me the best "bite" on the rollers.

But think of it this way, is it easier bowl with a 3 lb ball or a 15 lb ball? The 15 lb ball will hold its momentum longer, but takes more energy to get it to speed.

Now widen that bowling ball and you increased the amount of friction the surface sees because of the additional width.

1 inch contact patch vs 3 inch contact patch.

I could easily see 5 hp lose from a wider heavier tier.

Todd

 

[jfeagins]

Spinning inertia. More weight to spin requires a tad more hp to get it up to speed.

 

[Itgoes]

Yes, all of the above.

Tire inflation does have an effect on dyno results.....if you are ever in a "dyno shootout" it's best to have you rear tire at, at least 42 PSI.

All things being equal though as far as tire pressure and traction, and in the case of the Gen 2 numbers, it is the extra weight of the bigger wheel and tire. This has been proven by the results of dyno runs with BST carbon fiber wheels and a light weight tire. That combo will give almost identical results to the stock 200 wheel and tire (actually about 1 HP better)

My best dyno was 186 HP with the wide wheel. That was with a cat eliminator and a big air kit through stock mufflers. The 200 wheel and tire would have produced 8 more HP....so around 194 HP. A better exhaust would add 4-5 more HP.

 

[marsmax85]

Does anybody know where I can get a big air kit for gen 2 ?

 

[Itgoes]

Does anybody know where I can get a big air kit for gen 2 ?

No one is currently making/selling them.

That is a good mod if you are only looking for max peak HP. You will lose substantial power in the low-mid range, that's why I took mine off. Many don't mind because there is still plenty of power down there, but I didn't think it was worth it. If I was going to do a lot more drag racing, I might consider putting one back on.

 

[marsmax85]

No one is currently making/selling them.

That is a good mod if you are only looking for max peak HP. You will lose substantial power in the low-mid range, that's why I took mine off. Many don't mind because there is still plenty of power down there, but I didn't think it was worth it. If I was going to do a lot more drag racing, I might consider putting one back on.

Thanks for the info ....

 

[Chopcor]

Thanks, Guys- I think I'm starting to get it now. Must have been having a brain fart, LOL!

 

[one2dmax]

Exactly. The dyno's purpose is to measure the ability of the driving wheel to overcome the resistance needed to turn it's drum. So, the increased weight and reciprocating mass only adds to that resistance which it is not giving you any "credit" for.

Soft tires and slicks I don't think lower the number much but it's very hard on the tire and they can have a higher failure rate.