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Old 2nd March 2006, 15:21   #1
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Default UNSPRUNG WEIGHT - and its effects

Despite a lot of material on on tyre and rim upgrades etc, I did not find anything on the forum reg an important thing to be considered while doing these mods - Unsprung weight!

Will someone knowlegdable shed some light on the various aspects of unsprung weight, merits/demerits etc for everyones benefit!
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Old 2nd March 2006, 19:26   #2
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Exclamation Extract from www.musclecarclub.com

Unsprung Weight

An important concept is "unsprung weight." This is weight that is not supported by the suspension of the car. This usually includes the the weight of the wheels and tires as well as a percentage of the weight of the suspension itself, including control arms, anti-roll bars, shocks, and struts. Reducing unsprung weight is the key to improving handling. The lower the unsprung weight, the less work the shocks and springs have to do to keep the tires in contact with the road over bumpy surfaces. An easy way to reduce unsprung weight and improve traction is to replace stock wheels and tires with special lightweight wheels. Note that as the wheel diameter or width increases, the weight of the overall wheel and tire package increases, thereby increasing unsprung weight
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Old 2nd March 2006, 19:58   #3
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Therefore what is the effect of a lighter that stock vs heavier unsprung wt.. upsizing ones wheels one runs a clear risk of increasing the wt right?... so what would the effect be.. bad milage?.. more steering effort?.. suspension problems?

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Old 2nd March 2006, 20:36   #4
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Exclamation Here goes..............

Quote:
Originally Posted by kb100
Therefore what is the effect of a lighter that stock vs heavier unsprung wt.. upsizing ones wheels one runs a clear risk of increasing the wt right?... so what would the effect be.. bad milage?.. more steering effort?.. suspension problems?
Increasing or upsizing your wheels and tires doesn't increase the unsprung weight of your car unless it's a drastic upsize like the little bigfoot look!

The alloy wheels of the same size as your OE or one size up will definately weigh less.......so will the tires, because of the alloy in the wheels and the compound used in the tires!

More the unsprung weight, more the effort made by the engine to move the wheels, lesser the mileage! More the suspension wear and tear!!

When i changed over to alloy wheels i kept the steel rims with the biased tires to be used when the car went in for the paint job, i even weighed them...... Each 12" Alloy Wheel shod with Bridgestone tubeless weighed 10kgs whereas the Standard ones[12x4.5] weighed in at 14kgs.....an obvious weight reduction!!!
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Old 2nd March 2006, 20:42   #5
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Just what I thought!1... The elantra comes with 15 in ALLOYS and 195/60/R15s... so logically even a 205/60/R15 will wight more than the stock...and upsizing to 16 " is outta the Q ?? wonder if there are any special brands of low wt/super strong alloys or tyres??... heard somewhere that PIrelli p6000's use a low wt tech.. is that so?
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Old 2nd March 2006, 21:13   #6
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Exclamation Super light................

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Originally Posted by kb100
Wonder if there are any special brands of low wt/super strong alloys or tyres??... heard somewhere that PIrelli p6000's use a low wt tech.. is that so?
There are companies that make really super light weight alloy wheels....... They use a Magnesium Alloy [That's where the term Mag wheels come from]. They are very strong, very light and very costly!!

O.Z. and BBS are only two such companies, where each set can set you back by more than a lac and a half!!
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Old 2nd March 2006, 21:19   #7
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To feel the difference between alloys and steel rims, do this...with your steel rims, floor your car on a dirt track. Then change to alloys and do the same. You feel like you are gliding over the surface, and it's been tarred overnight. That's the difference a few kgs of unsprung weight makes.
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Old 2nd March 2006, 21:31   #8
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Many thanks... Like I said the stock wheels are also alloys - so am not going to have the advantage of upsizing with the absolute comfort of knowing this will nto be a problem... so makes sense to weigh the stock alloy+tyre combo to see what difference it will make with the upsize+tyre combo... and is there a tolerance to these things??... as in can it be a kg over wt without creating problems?

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Old 2nd March 2006, 21:53   #9
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Ooh so you're already running on alloys....... hmmmm...... a kg more should be tolerated..... nothing more!!!

And ditto to what v1p3r said about the absorption levels when the unsprung weight is kept in check!!!
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Old 4th March 2006, 00:15   #10
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For your reference - TBHP: The weight of your wheel&tyre combo (Whats the weight of your wheel-tyre combo??)

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Old 4th March 2006, 20:36   #11
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Hey Thanks Rehaan... made for some interesting reading... now off to buy a small hand held weighing scale - no other way of trying out various combinations - the vendor is unlikely to let it outta his sight!!
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Old 4th March 2006, 23:39   #12
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Quote:
Originally Posted by kb100
Hey Thanks Rehaan... made for some interesting reading... now off to buy a small hand held weighing scale - no other way of trying out various combinations - the vendor is unlikely to let it outta his sight!!

Sounds good to me.
Quite a few tyre shops have large weighing scales but i guess its better to buy a smaller ("higher resolution") one. Maybe going upto 10kgs (then you will have to weight the tyre and the wheels seperately.)

Post your findings in the tyre/alloy weight thread!
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Old 26th March 2007, 15:52   #13
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Hey KB, whats the scene on the weight of the stock alloys & tyres vs 16" alloys and 205/55/R16 tyres. Have you checked them ??

If there is anybody with 16" alloys on the Elantra, pls post your replies.

It would help me decide whether I should upsize the alloys and the tyres.

Thanks in advance.
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