Will bigger wheels affect dyno readings?

[monstaR]

Hi guys, wanted to dyno my car and was unsure if the rims that i have on now would affect the readings on the dyno or alternatively, should i put back the stock rims on my dc2r????? :confused:

[mxtcy]

nah they will be fine... you get three runs anyway when you have a dyno session.. so have one with the big rims and one with the stock rims or something

[IRI]

Difference in unsprung weight (ie rims/tyres) makes a huge difference, but since a dyno is on rollers and momentum is continually building, it may not have an effect....

[bluebird]

I can assure you guys rims and relavant tire sizes DO have an affect on a dyno readout.... :)

A friend tested it, three dyno runs with 18s, three dyno runs with stock 14s, and he got 5kw less on the bigger wheels.

I don't think it would matter as much if you wheels/tyres are perfectly matched compared to the stock wheels, but from what I gather, not many peoples cars are like that :)

[Boost]

The only way to find out is to speak to someone who runs a dyno shop... maybe dynodave . You need to speak to someone who knows how they work. I doubt anyone in here would beable to give you the exact answer to that question.

[K3NstyL]

Nah shouldnt have any effect on dyno, wheel performance is only relative to the car, and the car ain't movin. :cool:

[bluebird]

Nah shouldnt have any effect on dyno, wheel performance is only relative to the car, and the car ain't movin. :cool:
Well a car NEVER moves, but the wheels certainly do.

There's no difference to the way a car moves it's wheels on the dyno to on the street as far as i'm concerned?

But I agree - DYNODAVE would be able to answer this question perfectly.

[monstaR]

Hey guys,

I think I will carry on dynoing the car with the 17s....... and we will see what happens cos bringing the stockies are too much of a hassle. :thumbsup:

[Boost]

hey monstaR, but if you bring the stockies with you on the day... you can compare and see for yourself if it makes a diff. or not. Experimentation and obtaining the results infront of you is always better than word of mouth IMO.
:)

[bennjamin]

the engine takes more effort ( and loses HP ) throught larger wheels - which makes perfect sense when you compare weights of wheels - such as little 14inch wheels will require less effort to move than big 18's.

The difference is not possible to just work out - you have to measure it for yourself - with 1 dyno run with say stockies, then the next with the 18's. . . and measuring the difference.

[Jus-10]

What are you dynoing the car for?

Dynos are a tuning tool first and foremost, and yes, bigger and heavier tyres will generally offset the power readings. A mate of mine in an E46 M3 with 20s put out just over 120kw at the wheels....

If all you are after is an impressive power figure, get them to tweak the dyno for you.

[r|Ce_bOi]

the engine takes more effort ( and loses HP ) throught larger wheels - which makes perfect sense when you compare weights of wheels - such as little 14inch wheels will require less effort to move than big 18's.

The difference is not possible to just work out - you have to measure it for yourself - with 1 dyno run with say stockies, then the next with the 18's. . . and measuring the difference.

bennjamin does have a point here...
a heavier wheel is harder to turn than a lighter one...

but of course i could be wrong.. just try 2 runs with both sets and see how you go... :)

[monstaR]

Thanks guys....... i am dynoing the car to see the amount of power it can put out with mugen extractors, mugen exhaust, high flow cat and air filter. Just want to see if i can go beyond the 110kw mark?????...... I will see what happens. :D

[Type R Positive]

A chassis dyno makes more hp than a normal dyno cause no wheels. This should answer your question.

[integrity]

with bigger wheels i think that it does affect your performance ...
the stock size for my integra ls is 14 inches and i upped them to 17 inches ... when you have bigger wheels on your diff it makes them take longer to do a full rotation so that means the bigger the size it will take longer to do a full spin ...

[monstaR]

Quite true.... my stock R has 15/55/195 and i upped it to 17/40/215..... :p

[monstaR]

But I think the 17 work emotion that i putin is only abit or not the same weight as the stock rims?????

[Type R Positive]

should work off total weight of tyres included. Rims may be lighter but tyres may not.

[monstaR]

point taken..... :thumbsup:

[2ds]

more rotational mass = less torque doesn't it ?

-2ds