Wheel weight

[Dieselman]

Having looked around recently at the effect that wheel weight has on performance, steering response, comfort and economy I decided to weigh my own wheels as a baseline reference.

The general consensus is that each kg increase in weight has 4 times that effect as opposed to overall vehicle weight due to the increased kinematic and gyroscopic effect.
So a wheel/tyre combo weighing 3 kg more has the same effect as adding 48kg to the weight of the car.
3 kg * 4 times the value * 4 wheels. 3*4*4 = 48.

Tyres have a greater effect than the wheels due to their mass being further from the central hub.

I weighed 3 wheel styles all in 7.5x16" size with offset of either ET41 or ET42 and 215x55-16 tyres. Each had fairly worn tyres of equal wear.
Two were MB alloys and one was the MB spare. The alloys are the standard W210 Avantgarde style and the W211 Rucha style.

Surprisingly both alloy combo's weighed the same at 17.9 kg and the steel came in at 19.3 kg.
The tyre probably weighs a little over 10kg in each case.

Has anyone ever weighed their wheels, if so do they want to add the weights on for comparison as 'm particularly interested to see the effect of upsizing diameter or width.

 

[robert.saunders]

Just have a beer will you, and mebbe a movie

 

[Dieselman]

Just have a beer will you, and mebbe a movie

Get yer scales out and yer nuts off...

 

[Will]

I sold a set of standard MB 15", 15-hole, 7J alloy wheels as fitted to the 190E 2.3/2.5-16 models. Tyres were quite well worn (205/55/15 - just a few mm tread on each) and the combined weight for each pair was just under 30kg - so say 15kg each.

I know this because I had to send them by courier, and the maximum weight was 30kg (close!)

Will

 

[whitenemesis]

It's a pretty well know fact that the unsprung weight has a significant effect on handling. The goal has always been to minimise the mass the springs and dampers have to control.

The lightest wheels I ever ran were Revolutions (back on the 70's) easily carried with one hand. The effect on my car was akin to knocking the mud off one's wellingtons

 

[Dieselman]

The effect on my car was akin to knocking the mud off one's wellingtons

Surely the mud helps you press the accelerator further in a diesel...and they all have mighty big wheels, don't they.?

 

[whitenemesis]

Surely the mud helps you press the accelerator further in a diesel...and they all have mighty big wheels, don't they.?

Meeow!!

I know you are joshing but I'll defend my statement

The car in question wasn't a diesel...

And one doesn't have to depress the accelerator as far in a diesel to get the same effect as in a petrol car

 

[stevesey]

I weighed 3 wheel styles all in 7.5x16" size with offset of either ET41 or ET42 and 215x55-16 tyres. Each had fairly worn tyres of equal wear.
Two were MB alloys and one was the MB spare. The alloys are the standard W210 Avantgarde style and the W211 Rucha style.

7J*16 W202 Sport style wheels on (the bathroom scales)

2 * 205/55/16s weigh in at approx 16.5Kgs each
2 * 225/50/16s weigh in at approx 17.5kgs each

Allowing for a bit of reading error the extra 20mm tyre width adds 0.5-> 1 Kg

I have 8Js + 225s on the rear of the car at present, next time I have one off I'll try to remember to weigh it.

 

[Howard]

Guys , it's friday night , shouldn't we all be out drinking beer and smashing shop windows ?

Weighing wheels on a friday night

 

[Number_Cruncher]

>>The general consensus is that each kg increase in weight has 4 times that effect as opposed to overall vehicle weight due to the increased kinematic and gyroscopic effect.

Yes, the rotating mass counts more than once - but where does 4x come from? In my experience, the effective mass isn't anything like that.

 

[stevesey]

Guys , it's friday night , shouldn't we all be out drinking beer and smashing shop windows ?

Weighing wheels on a friday night

Been off work today with man-flu off to bed soon. But now you mention it a beer wouldn't go amis - back out to the garage.

 

[Will]

Been off work today with man-flu off to bed soon. But now you mention it a beer wouldn't go amis - back out to the garage.

Me too. First day off sick for a good few years now. I think it's the Norovirus Knocked it right out of me.

And I didn't weigh my wheels tonight either

Will

 

[230K]

Hi

I weighed steel 16" spare, 17" alloys and 18" alloys

Results here http://www.mbclub.co.uk/forums/showthread.php?t=60852&highlight=alloy+wheels

230K

 

[Dieselman]

So from C320k post

17" x 8" (presumably) with 235/45-17 tyre weighs 21kg.
18" x 8" or 8.5" with 235 or 265 tyres weighs 23kg

Just for ref our other car has 6.5x16" ET42 rims with 205/45-16 tyres and the combo weighs 16.7kg

 

[stats007]

Michelin will supply tyre weights of all of their tyres. Can be surprising to see different brands being 2kg lighter in some instances.

Get some forged or magnesium wheels if you want to see a real difference.

 

[stevesey]

7J*16 W202 Sport style wheels on (the bathroom scales)

2 * 205/55/16s weigh in at approx 16.5Kgs each (ET37)

Just for ref our other car has 6.5x16" ET42 rims with 205/45-16 tyres and the combo weighs 16.7kg

Would have expected yours to be lighter (less metal and rubber) - could just be the error between different scales.

 

[pete vee rod]

Is there a question in this or did I miss it?

 

[Dieselman]

>>The general consensus is that each kg increase in weight has 4 times that effect as opposed to overall vehicle weight due to the increased kinematic and gyroscopic effect.

Yes, the rotating mass counts more than once - but where does 4x come from? In my experience, the effective mass isn't anything like that.

A number of sites, even supposedly technical ones referred to the figure being 4x. I've done some more reading and see a couple of working examples giving 2x.
The problem is that the wheel/tyre combo doesn't behave like a flat disk so tends to concentrate the weight at the outer circumference because of the rim and tyre. This adds to the inertia effect.

Either way, everyone agrees that heavier wheels make a significant difference to acceleration and handling.

HERE is a post covering this
and a Calculation sheet.


http://www.potn.co.uk/blog/2008/05/...r-when-you-could-just-buy-lightweight-wheels/

“Losing 1kg of rotational weight (i.e. wheel weight) is the straightline performance equivalent to removing 10kg from your car”

I assume that means across all four. I've read that previously.

 

[Number_Cruncher]

I wouldn't place too much faith in the spreadsheet - I'm fairly sure it's wrong.

The other link doesn't work for me - it leads to a dead end web page.

I'll see if I can dig out some old calcs I have kicking about from some years a go - I'm fairly sure it's nowhere near a 4x effect.

The other main point to make is that unsprung mass is most important for ride and handling at design time, when the spring and damper rates are chosen. I would be hugely surprised if anyone short of the talents and sensitivities of a top class driver would ever notice the difference made by relatively small changes in unsprung mass on the road.

 

[Dieselman]

I had already said I accepted 2x to be the correct value now.
The link was working at the time of posting it...you've broken it...
Can you remeber Top Gear testing a Renault Avantime performance and everything that did caused it to reduce.
The first mod was bigger brakes and wheels. That cost them over 2 seconds per lap, which they had to spend thousands to recoup.

Avantime