mag rims

Chris Wehrheim · Posted: Thu Jul 26, 2001 4:29 am Post subject: mag rims

Ok i was just wondering what you guys have found as the best mag. rim out there and do they make that big of difference on the track.
Thanks Chris

Keith Archambeau · Posted: Thu Jul 26, 2001 6:35 am Post subject: mag rims

Chris, can't really say which mag is best. What we have found is that if your looking for a little more grip the mags help. Although when the grip is very high the mags will agravate a hop. When the mags hop they seem to have a high spring rate, kind of springy compared to a cast or billit aluminum wheel. The mags make the hop more voilent. In retro, the mags add more grip. Most of the time we will mix. Mag in rear or front only. Hope this helps

Christofer Hoff · Posted: Thu Jul 26, 2001 7:08 am Post subject: mag rims

quote:
Originally posted by Keith Archambeau:
Chris, can't really say which mag is best. What we have found is that if your looking for a little more grip the mags help. Although when the grip is very high the mags will agravate a hop. When the mags hop they seem to have a high spring rate, kind of springy compared to a cast or billit aluminum wheel. The mags make the hop more voilent. In retro, the mags add more grip. Most of the time we will mix. Mag in rear or front only. Hope this helps

Keith, do you have any insight as to WHY the mags. assist in providing more grip? One would think that the more downforce (weight) applied to the contact patch of a tire would perhaps help that contact patch remain in contact with the pavement. So, would decreasing the mass reduce this. Logically if so, one would think it might decrease grip. This of course approaches a point of diminishing returns, but I'd be curious if anyone can identify the physics of this environment.

Also, I don't mean to pick nits here, but I don't think it's accurate to refer to 'spring rate' in the context of a non-articulated suspension that has a remarkable lack of springs or dampeners in its functional implementation.

The mass of the rims are certainly less with Magnesium based units, and that may account for the fact that they allow the flex in the chassis to make itself more pronounced (it requires less work in the same amount of time for the rim/tire to lift and fall,) and thus the frequency of the hopping motion more intense, but I'd be cautious in defining these dynamics as being anyway related to spring rates.

If I understood you correctly, I think you were intimating that given less mass, the rims will tend to hop more, correct?

Interestingly, in this context can we even describe the suspension components and rims as being 'unsprung weight' since there is no 'sprung weight?'

Hey, this is the 'Tech Hit Squad' forum...

/Hoff

Pete Howarth · Joined: 18 Jul 2001 Posts: 40

What is a spring “technically”?
Is a coiled piece of metal? Not necessarily, it could be a leaf spring.
Or, is it a piece of metal? Not necessarily, it could be any material.
All materials have some amount of elasticity. Anything that bends or changes shape and then returns to its original shape is a spring of sorts.

I’d venture to say that axles are springs. They flex under load and return to their original shape. They are very like a ¼ elliptic spring, only without the “elliptic” part.

So, I’m not ready to throw out the “sprung weight argument”.
What is the weight difference from aluminum to magnesium? I’m not ready to throw that out either. Also, wouldn’t the flex of the rim add to this too? Maybe it’s a combo of the three. I wish I still had my old textbooks, so I could look up the spring rates for different materials.

I don’t know much about the wheel types and I’d like to hear more about this.

So, mag. = more grip, but might hop under too much grip. Why don’t you change the air pressure? Or, the type of hubs your using?

Chad Stapleton · Joined: 19 Jul 2001 Posts: 4403

Magnesium wheels have two advantages over aluminium;-
Weight reduction - with its various associated benefits - This is a physical fact.
Better Heat transfer from the tyre - this is a bit less easy to verify and probably the subject of debate as to weather it is of benifit or not !
Some also claim to be "stiffer" than alloy, though of course this is more a function of the detail dimentional design than the minor differences in the material characteristics.
On the down side they are definitely more brittle - prone to fracture easier - and suseptable to corrosion.
And of course the cost is double !!

Many the above +ve /-ve points apply to a degree for Carbon Fibre wheels also.

These things have more affect on peoples "pit credability" than on their track results !!

Brandon Adkins · Joined: 25 Jul 2001 Posts: 27

I think everyone is a little wrong, i think the mags make for less grip bz they dont alow the tire to get as hot as aluminum wheel, so there for if the tire dont get hot then there would not be as much hop. Also every kart is different so everyones situation is going to be different, if u have a peice of crap european kart then yea it might add more bite and therefore be more hope, but if u have a good handleing american or any other kind of kart that works, then i would say less hope bz of stablization. Hope i made some sense if not your loss.

Brian O'Hara · Posted: Thu Jul 26, 2001 5:41 pm Post subject: mag rims

quote:
Originally posted by Brandon Adkins:
...if u have a peice of crap european kart then yea it might add more bite and therefore be more hope, but if u have a good handleing american or any other kind of kart that works, then i would say less hope bz of stablization. Hope i made some sense if not your loss.

Wow Brandon, that was enlightening! Perhaps you should be a bit more diplomatic in you description of the way you see things. I know that you are young, and probably trying to make a career in motorsports, so you should keep in mind what potential sponsors might think when they see a reply like that.

Regards,

Brian O'Hara

Oscar Aguilera · Joined: 18 Jul 2001 Posts: 1614

Mag wheels are harder and therefore stiffer. Stiffer equals more grip. It is the last thing IMO you can change if you have changed everything else or you don't own other things that could be changed first. I.E. you bought a kart wiht extra wheels anthe extra set are aluminum, your main set is mag. and it didn't come with extra axles.

The mag is lighter and it is spinning weight which makes it more crucial. The mag will heat up slower whci is better for racing.

Cast Aluminum is next in line and spun aluminum are the softest. Soft equal less grip. Aluminum wheels heat up faster and are traditionally used for mounting rain tires and racing in the rain. Faster heat wil heat the tire quicker which is better in the rain.
My $.005 for what it is worth.

Tim Megenbier · Joined: 25 Jul 2001 Posts: 573

Mag or Aluminum, The driver should be able to tune to, or around the difference in the materials. Set a baseline.Take your kart out with Mags and do 5-6 laps. This will warm up the tires and should give you a start. Document your findings, tight in a sweeper, loose in the hair pin etc.
Now put on the aluminum wheels. make sure you dismount the same tires that you used on the mags and remount them on the aluminum wheels, in the same position you had them on the kart. Do your same 5-6 laps. You should have a pretty good comparison.
I also think the biggest over looked problem is the offset between the mag and the aluminum wheels. To figure this out put 1 of each wheels next to each other on a flat surface(without tires)with valve stems facing up, measure from the surface to the mounting flange.(the 3 hole flat part in the center of the wheel)Make sure it is the same distance from the surface to the flange on both wheels. In my experience that the mags seem to have a bit more offset. this would cause the rear with to be slightly wider.
If the offset is not the same it would be an unfair comparison. We feel that the mags tend to be a little bit stiffer, Again you should be able to tune around the problem. The lighter the rotating mass the faster the acceleration! The question is how much faster? You couldn't measure it on the track. terrorinc17@aol.com

Jon Betts · Posted: Fri Jul 27, 2001 5:26 am Post subject: mag rims

I have a 98 Trackmagic demon which has the old US 3 on 2.5" bolt pattern does anyone know where I can get Mag or cast Aluminum wheels with this pattern, I know I can change the rear hubs to 3 on 58mm but I think it would become an expensive proposition to change the front hubs, also I have 2 sets of Douglas Wheels with the US bolt pattern.

Thanks JB

Larry Ferguson · Posted: Fri Jul 27, 2001 5:43 am Post subject: mag rims

[QUOTE]Originally posted by terrorinc17:

Just in case you weren't around for this earlier, you will kndly stick to your real name, as opposed to a nickname. You will surely wear out your welcome if you can't play like the rest of us. Thanks.
Larry

Larry Ferguson · Posted: Fri Jul 27, 2001 5:50 am Post subject: mag rims

quote:
Originally posted by Brandon Adkins:
I think everyone is a little wrong, i think the mags make for less grip bz they dont alow the tire to get as hot as aluminum wheel, so there for if the tire dont get hot then there would not be as much hop. Also every kart is different so everyones situation is going to be different, if u have a peice of crap european kart then yea it might add more bite and therefore be more hope, but if u have a good handleing american or any other kind of kart that works, then i would say less hope bz of stablization. Hope i made some sense if not your loss.

Whoa there, boy! It's already been said, but you better watch yourself here! This isn't a forum for boycotting foreign goods. Your reply was most definatly out of line. Hopefully you will see this as quickly as I have. Perhaps you should have a proofreader handy to look things over prior to your posting such ridiculous garbage. Now, pull your pants back up and don't let this happen again!
Larry

Chris Wehrheim · Posted: Fri Jul 27, 2001 6:08 am Post subject: mag rims

Thank you everyone for your reply and man was brandon way out of line. Cool your jets dude.

bird · Joined: 17 Jul 2001 Posts: 147

He sounds like a silly little tart, did a Tony beat him or something?

Keith Freber · Joined: 27 Jul 2001 Posts: 88

He sounds like a silly little tart, did a Tony beat him or something?

You must not be familiar with Brandon...there is not much of anything (or anyone)that can beat him. I saw him put in one of the best drives I've seen in a long time this past weekend at the Springfield MWSS event. Quick, mature and measured (hard to believe after his comments...), he showed the all the juniors and seniors how it should be done. BTW, he gets it naturally...his father was the best ever in my book.

[ July 27, 2001: Message edited by: Keith Freber ]