: Calculate HP gains based on reduction of rim diameter?



LITTLEELVISDAN
06-28-10, 02:42 PM
Does anyone know how to calculate HP gained by reducing the diameter of the rims? It's been dyno proven to loose HP by going to larger diameter rims due to moving rotational mass out. I was wondering how many horses I would gain if I took off my 22's to say 18's. I should gain by moving rotational mass in 4 inches. I even thought about going to 16x10's to even gain more but don,t want to dyno each combo.

Anyone know how to calculate?

Ronin
06-28-10, 03:08 PM
Anyone know how to calculate?

Yes.

Dyno the truck with 18s...

Then with the 22s.

Subtract the difference, if any, and there's your answer. :D

Rotating mass affects a lot more than just horsepower; braking, handling, etc. But unless we're talking a significant difference in weight, on a 3+ ton SUV are you really going to be able to tell the difference? Putting 16 inch wheels on a truck the Escalade's size for exactly what benefit? I'd get real use to explaining it to people, a lot, while they laugh and point at your tiny/dinky wheels..

I can tell you that swapping wheels out on a MINI Cooper I was working on resulted in over a 14 pound loss of rotating mass per wheel, same rim size. It went from go-kart, to extremely angry go-kart, on steroids, with just that one change. Almost 60 pounds of rotational mass on a car that size makes a massive difference, on a behemoth like the Escalade, not much at all...

LITTLEELVISDAN
06-28-10, 03:15 PM
I wou
Id have to think 6 inches less would make a decent improvement. Not only bringing in mass that much but getting lighter rims than stock combined should make a noticeable difference. No?

cu3rv0_bl4ck
06-28-10, 04:29 PM
One thing to consider is the overall wheel plus tire diameter. I know that an 18in wheels tire is thicker than 22. what the diffrence in both I do not know but it should be less than 6in.

Ronin
06-28-10, 05:06 PM
I wouId have to think 6 inches less would make a decent improvement. Not only bringing in mass that much but getting lighter rims than stock combined should make a noticeable difference. No?

I don't know of a quality lightweight wheel rated for a vehicle this size that would fit the bill...maybe Carl/hcvone would. The problem with lightweight wheels for such a large/heavy vehicle is the ride quality would suffer dramatically if they're too light, and the rims would take a whoopin'. Never mind finding a tire that would be properly rated for the load, etc. No offense, but I think you're way off the reservation on this one...

fivepix
06-28-10, 06:02 PM
I have 18 inch wheels I put on in the winter and I run 24’s in the summer and I see small differences in horsepower but not much.

Both my 18 and 24 inch wheels are the same diameter if you include the tires so in my case it’s the weight of the wheels I believe makes the difference, the 18’s defiantly make the truck feel lighter specially around turns but I don’t think I see too much HP increase. I’ve heard people say that 1 lb off could give up to 2.5 in horsepower but I’m not sure how accurate this is.

I would avoid using 16 inches wheels the Escalade is way to heavy and it would just look weird pulling up to a civic with the same size wheels :)

hcvone
06-29-10, 08:15 AM
We did this last year at the track, I ran my 09' with my winter setup stock chrome 18's with 275/65/18 Revo's vs. 24's (my wheels are the lightest forged 24's you will find ) with 305/35/24 Pirelli's and my truck was almost a second slower with the 24's in the 1/4. The big problem is most people use cast 24's that are so heavy they are killing their drive train and brakes

WaterKing
06-29-10, 08:52 AM
hcvone, can you provide us with the weight of your 305/35/24 combination? Perhaps broken down by wheel and tire?

LITTLEELVISDAN
06-29-10, 09:53 AM
I have 18 inch wheels I put on in the winter and I run 24ís in the summer and I see small differences in horsepower but not much.

Both my 18 and 24 inch wheels are the same diameter if you include the tires so in my case itís the weight of the wheels I believe makes the difference, the 18ís defiantly make the truck feel lighter specially around turns but I donít think I see too much HP increase. Iíve heard people say that 1 lb off could give up to 2.5 in horsepower but Iím not sure how accurate this is.

I would avoid using 16 inches wheels the Escalade is way to heavy and it would just look weird pulling up to a civic with the same size wheels :)
I have seen some pretty flimsy looking 22's and 24's designs on the road. Just because they measure 22' doesn't mean they are stronger than 16's, 17's, or 18's. Don't get me wrong I wouldn't go putting 17' Volks on my lade. i'll bet a 16' steel wheel is stronger than most 24's, not pretty but would hold the load just fine.

My 04 denial had stock 18's and was pretty quick. I went to 22's and noticed a big difference in lower gas mileage and slower off the line.

The reason for starting this thread was to find out if going to say 17x10's and running off road tires to the same OD of stock would gain me any HP and gas mileage. Has anyone done it? I have an AWD so it sits pretty high as it is so no need to lift it. It would move the rim in 5 inches and be a crap load lighter. Has anyone picked up a stock 22? they are freekin HEAVY.

Ronin
06-29-10, 11:31 AM
I have seen some pretty flimsy looking 22's and 24's designs on the road. Just because they measure 22' doesn't mean they are stronger than 16's, 17's, or 18's. Don't get me wrong I wouldn't go putting 17' Volks on my lade. i'll bet a 16' steel wheel is stronger than most 24's, not pretty but would hold the load just fine.

My 04 denial had stock 18's and was pretty quick. I went to 22's and noticed a big difference in lower gas mileage and slower off the line.

The reason for starting this thread was to find out if going to say 17x10's and running off road tires to the same OD of stock would gain me any HP and gas mileage. Has anyone done it? I have an AWD so it sits pretty high as it is so no need to lift it. It would move the rim in 5 inches and be a crap load lighter. Has anyone picked up a stock 22? they are freekin HEAVY.

Wow...you're just completely all over the place...now you wanna run off-road tires the same OD as stock...and you think that is gonna help your HP and/or mileage... Any weight you save by going with a smaller diameter wheel is going to be significantly offset by the additional weight of a true off road tire, which coincidentally, also contradicts your idea about getting the overall weight of the wheel as close to the hub as possible to save on rotating weight and, theoretically, increasing horsepower. Those knobbies/lugs whatever you wanna call the tread/pattern put additional weight exactly where you originally said you wanted to remove it from to begin with.

Carl/hcvone gave a pretty good example germane to his wheel combos, but now you're practically talking beadlockers and mudders...really???

LITTLEELVISDAN
06-29-10, 12:19 PM
pretty close to as described above. I use my trucks as construction vehicles. towing trailers, street or dirt, local driving, long distance. yo name it. I have never tracked a SUV nor will I ever so I really don't need ultra low profile tires. They are good for being flashy but thats about it. the northern guys put on 18's and snow tires for that very reason. Hell I just had the entire back end of the lade full with leaking old frozen drink machines. Not to mention the stack of 2x6x12's I had to rest on the center console and hang out the back window. I mainly bought the lade for the interior comfort and features. believe it or not I cross shopped it with a F250 turbo diesel king ranch 4x4. and the ford interior SUCKED.

Sorry but 1 ill placed curb or large rock, my 22's are going to be shot. I might switch to stock 18's. I was hopping to recover some lost HP & TQ by doing so (for towing).. I think hcvone answered my original question as he did see improvements going the 18's

If I want to represent lookin good in the A town or track a car, I'll polish up the STS-V and have a good time.

Ronin
06-29-10, 12:52 PM
pretty close to as described above. I use my trucks as construction vehicles. towing trailers, street or dirt, local driving, long distance. yo name it. I have never tracked a SUV nor will I ever so I really don't need ultra low profile tires. They are good for being flashy but thats about it. the northern guys put on 18's and snow tires for that very reason. Hell I just had the entire back end of the lade full with leaking old frozen drink machines. Not to mention the stack of 2x6x12's I had to rest on the center console and hang out the back window. I mainly bought the lade for the interior comfort and features. believe it or not I cross shopped it with a F250 turbo diesel king ranch 4x4. and the ford interior SUCKED.

Sorry but 1 ill placed curb or large rock, my 22's are going to be shot. I might switch to stock 18's. I was hopping to recover some lost HP & TQ by doing so (for towing).. I think hcvone answered my original question as he did see improvements going the 18's

If I want to represent lookin good in the A town or track a car, I'll polish up the STS-V and have a good time.

I run my 18s in the winter with Blizzaks since we can get up to 100 inches of snow here; pretty sure you're not worrying about that in A-Town...

There's no doubt my truck is more sluggish and doesn't brake as well with the 22s on, although it definitely handles better now that I've dropped it (2 front, 2 1/2 rear) and added front and rear anti-sways.

On my diesel Excursions I had 20s with the Nitto Terra Grapplers (http://www.nittotire.com/#index.tire.terragrappler)...those might be right up your alley. Believe it or not they're relatively quiet on the highway, and they'll handle anything you can throw at them. The Dura Grappler is nice, but not near as aggressive looking or functional off-road and the Mud/Dune/Trail are quite a bit more aggressive than the Terra, weigh and cost more I believe and will definitely give you more cabin noise on the highway...

LITTLEELVISDAN
06-29-10, 03:27 PM
Thanks man. I appreciate it. I'll look into those.

Ronin
06-29-10, 03:51 PM
Thanks man. I appreciate it. I'll look into those.

It's the least I can do for giving you such a hard time! Good luck...

hcvone
06-29-10, 04:23 PM
hcvone, can you provide us with the weight of your 305/35/24 combination? Perhaps broken down by wheel and tire?

37 lbs for the wheels including lugs and 51lbs for the Pirelli Scorpion Zero Asimmetrico tires. They are the wheels on my web site on the home page www.hcvind.com

WaterKing
06-30-10, 09:55 PM
37 lbs for the wheels including lugs and 51lbs for the Pirelli Scorpion Zero Asimmetrico tires. They are the wheels on my web site on the home page www.hcvind.com

Thanks, my Bazo forged wheels come in at 45lbs and Falken 305/45/24 at 48Lbs. Definitely slower with this combination than the stock 22's but some of that is because of decreasing final drive ratio with larger diameter tires. 15" Baer eradispeeds/EBC yellows did bring the brakes back.