Bigger wheels = less bhp?

[Guest jimmyb]

Is this true i know they'd averagly weigh more and thus slow u down but would it affect the figure at the fly and the wheels? sorry to post probably such a stupidly obvious question. but im from a 206 forum and thought u guys would no more about bhp lol.

[DamanC]

 

typically the first person to reply to your thread cant answer you question

[Jake]

Is this true i know they'd averagly weigh more and thus slow u down but would it affect the figure at the fly and the wheels?

At the flywheel, no.

Unless you're talking about the guessed at flywheel figure that folks 'calculate' from the RWHP figure. But that's a different can o'worms.

 

At the wheels, maybe.

Depends how heavy they are and whether the right sized tyres are used to correct the overall circumference - else it would change the gearing and skew the dyno results

[Homer]

If you have a rolling road dyno, it measures the torque at the wheels. As such, it makes no difference which wheels you have as its only measures what the entire drive train (inc wheels) produces.

 

So, provided EVERYONE who uses the dyno during the day during similar weather conditions, the results will be comparable in terms of actual power put to the road.

 

As soon as someone mentions Flywheel power then you're in no mans land. This is just a guesstimated figure based on inputs by the RR operator. Factors such as drive train, wheels, air temp, humidity, etc come into effect. flywheel figures mean nothing, wheel torque means everything.

 

If you mean, ‘do larger wheels reduce torque put to road', then the answer is probably Yes.

[Jake]

If you have a rolling road dyno, it measures the torque at the wheels. As such, it makes no difference which wheels you have as its only measures what the entire drive train (inc wheels) produces.

I disagree. Heavy wheels would take some extra torque to spin up. Reducing rotation weight anywhere in the drivetrain, including the wheels/tyres, would help the dyno result.

[whitesupratt]

The way I saw it, on rollers larger wheels make no difference to BHP. If does hoever make a difference to acceleration and top speed, but not power, Due to the larger rolling radius

[Homer]

I disagree. Heavy wheels would take some extra torque to spin up. Reducing rotation weight anywhere in the drivetrain, including the wheels/tyres, would help the dyno result.

 

Sorry, my post was badly worded, those first two sentences presumed the poster had been given calculated flywheel figures.

 

Yes, its takes more torque to spin up heavier wheels, thereby the dyno will see a lower result since it only measure at the wheel, not before. I.e. power is wasted spinning up a heavier wheel.

[Jake]

Yeah Darryl, I think we were saying the same thing in different ways

[Jake]

The way I saw it, on rollers larger wheels make no difference to BHP. If does hoever make a difference to acceleration and top speed, but not power, Due to the larger rolling radius

Larger wheels make no difference to rolling radius or circumference if the correctly sized tyres are fitted.

[Gazboy]

I'd assume heavier wheels would increase the amount of power loss getting from the fly to the ground, afterall heavier items need more energy to move them.

[Kranz]

If running a power curve during an acceleration there will be an increased inertia caused by bigger wheels/tyres, however the torque output will be the same as long as the total gearing remains the same. The only difference is that the increased inertia will make the acceleration slower. This is a good thing as it is closer to steady state running (i.e. running at a set speed & load).

 

Taking steady state points (i.e. 1000 rpm, 1500 rpm) and logging the data then moving on to the next speed on the power curve, the bigger wheels/tyres will make no difference.

 

Its the same as having a heavy car Vs a light car. The power output is the same, its just the acceleration thats affected.

 

If the total gearing changes because of the change in wheel/tyre size then torque at the wheels will change. Power will remain the same though as power is based on torque and rpm. Bigger wheels = less torque but more rpm which cancel each other out when looking at power.

 

If you want more torque at the wheels go for smaller diameter wheels & tyres.

[Guest jimmyb]

Thanks guys, was scared u lot would rip into me. Ive gone from 16" to 18" and lost 10 profile. Having it rolling roaded next month (206 gti) havent entered the wonderful world of supra's next.

[ivan]

Bigger wheels = less bhp?

 

Nope.

 

 

Bigger wheels = less torque.