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Mangocats
Mangocats New Reader
12/13/20 4:38 p.m.

In reply to OldGray320i :

At 12lbs per corner (!?), only between a 1/4 and 1/2 second

True, it's a small difference on the stopwatch, but a much bigger difference in the seat of the pants.  I have both factory steel and lightweight alloy wheels for my Miata, I think the difference is something like 8lbs per wheel.  The car is certainly driveable with either set of wheels, but you can definitely tell when one set is on vs the other.

Somewhere shy of forged aluminum, the cost-benefit curve goes crazy.  Just don't make the mistake of ignoring wheel weight altogether.  There are benefits in smoother running on the highway as well, less sensitivity to bumps, your shock absorbers are more effective, etc.

 

SVreX (Forum Supporter)
SVreX (Forum Supporter) MegaDork
12/15/20 3:03 p.m.
Snrub said:
SVreX (Forum Supporter) said:

It's hard to find sometimes, but it is a much bigger variation than most people realize. 

Tire rack has that info for every tire they sell. I picked 245/40/18:

Competition class tires: Hosiers are 21-22lbs. Everything else 25-26lbs.

200tw: 25-28lbs.

I think the problem with picking tires based on weight is that a heavier tire may be faster than lighter one. There is info on which tire is faster. There is no performance, or even durability data on wheels, so the only thing people focus on is weight. In the Enkei test it's a .4sec difference on a road course with a non-viable wheel vs. a viable one. Is it maybe .1 between a decent wheel and a worst one?

That may depend on what rules you are playing by. 
 

I brought a car to the Challenge a few years ago wearing Hoosier Road Racing bias plys.  (DOT legal is not required at the Challenge).  They were 14 lbs per corner. By the time we included the lightweight wheels, we saved 24 lbs per corner. 96 lbs rotational weight.  That's a lot!

The operating temperature was off. The road racing tires were intended for extended periods at speed, not short autocross.  We compensated by using smaller tires intended for a lighter car than we were running.

It worked perfectly. 

Shavarsh
Shavarsh New Reader
12/15/20 3:32 p.m.

Can't wait to see the bumpy part 2 article. Great discussion here. 

Shaun
Shaun Dork
5/31/21 5:52 p.m.

In reply to Mangocats :

As a non racing gearhead the GRM site/forum helped me to recalibrate my value of time in a motorsport context.  '1/2 a second' (or some such) per lap (or whatever metric the specific performance motor sport is using) is allot in most time evaluations.  1/2 a second a lap on a short 60 second ish lap like this is ALLOT in motorsport terms.  Like in a 10 lap race you are nowhere to be seen at the finish if you are 1/2 a second a lap slower.   

67LS1
67LS1 New Reader
6/1/21 9:30 a.m.

I guess my answer to the title question would be yes, every time.

But is it worth spending up to get lighter wheels? That would be a personal and application specific decision.

I've got American Racing VR Rodder wheels on my car and am looking to make a change. I noticed that Torque Thrust ll wheel are 6 lbs lighter per wheel. That pretty significant for a budget wheel line like American Racing.

 

05CAR
05CAR None
6/2/21 10:34 p.m.

Rallye or racecircuit is gonna be a bigger difference 

05CAR
05CAR New Reader
6/2/21 10:34 p.m.

Rallye or racecircuit is gonna be a bigger difference 

mhisstc
mhisstc New Reader
6/3/21 1:50 a.m.

So is the difference in rotational mass between a heavy vs. light wheel setup something that can be easily verified on a chassis dyno as a difference in measured HP/TQ at the wheel?

Mel9146
Mel9146 New Reader
6/7/21 5:20 p.m.

You stated you are not that competive yet.  More rubber will help.  In the learning phase keep the cost down.  After you have done all the inexspensive things, and are now near the top gor the lighter wheels.  I recommend three piece wheels.  My 9`` RSR 2.8 clone car runs BBS Magnesium centers andaluminum hats.  With gears, it keeps the 3+ liters looking directly over there shoulder.

 

Remember lighter generallly means easier to damage.  For Autocross on parking lots stay away from pot holes, on the race track try not to drop the wheel off the track, any bend means end of the weekend for that wheel.  One must check the center of a 3 piece wheel if one damages a hat.

jerel77494
jerel77494 New Reader
9/20/21 7:55 a.m.

In reply to OldGray320i :

Yeah, but at least you'll suck less!

livinon2wheels
livinon2wheels GRM+ Memberand Reader
1/8/23 4:09 p.m.
Tom1200 said:

I've commented on various posts before about running the smallest wheel & tire you can get away with BUT I'm racing cars that only have 100whp. 

My experience certainly bears out what you are saying as the truth. I usually manage one track day a year due to financial constraints and other competing interests but it is nonetheless important. Last year I took the devilwagon to VIR on 16" wheels with 225/50-16s as opposed 225/45-17s from the previous year. Obviously there are numerous things in play here, ride height is down some, so less weight transfer in corners and under braking, more favorable gearing allowing me to get nearly to the top of 4th gear and bump the rev limiter occasionally, the lighter wheels helped I am sure. At any rate in combination, I was better than 2 seconds a lap faster than the previous year. How much was track familiarity? Who knows? but I can tell you the lower ride height and the slightly shorter gearing were noticeable changes to me as the driver and made some positive difference in my lap times. The overall wheel/tire weight was about 5 lbs lower per wheel than when on 17s. Never mind I had gained a few pounds myself. :(

Still, the car was faster. I want to try a good 200tw tire this year in the same size 225/50-16 that will hold up for street use and see what kind of improvement I can get. I have no doubt that will make the car more predictable at the limit and thus easier to drive on the edge of the friction circle. Suggestions for a long lasting consistent performing inexpensive 200tw tire in the 225/50-16 size will be gratefully entertained.

racerfink
racerfink UberDork
1/8/23 7:37 p.m.

In reply to livinon2wheels :

If you aren't testing things on the same day, lap times are pretty much useless.  It's amazing the times I've gone to Sebring and been two seconds off my regular pace, along with everyone else in Spec Miata.  Track temps, humidity, wind, oil on track, recent rains, did Indycar recently test and leave super sticky rubber down...  it all affects lap times.

z31maniac
z31maniac MegaDork
1/8/23 8:01 p.m.

I'm sure it's a tiny difference, but for the most part, fancy lightweight (well made wheels) tend to look much better. 

wspohn
wspohn SuperDork
1/9/23 12:13 p.m.

I ran one of my race cars on magnesium wheels but when I switched to vintage racing I went back to fairly heavy knock off peg drive stock steel wheels. I can't say that the lap times changed, but the feel certainly did - I preferred the alloys.  I also ran a race on some other steel wheels and under hard braking the car was twitchy - presumably the wheels were flexing. Fortunately that was not the case with the peg drive steel wheels (or the magnesium ones) - I could take my hands slightly off the steering wheel under full braking and no twitch!.

 

 

Scott M
Scott M New Reader
3/25/24 9:27 a.m.

I'm interested in a revisit to this topic, but with a car that would not be so susceptible to the weight difference.  For example, a Corvette - something with plenty of power and, specifically, torque.  In that case, how significant is the difference in losing ~10lbs at each corner by switching to lighter wheels?

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