Unsprung weight - does it matter much?

Might be a daft question but I've heard people talking about the unsprung weight (mainly on motorbikes) and how much difference it makes to have lighter wheels/tyres.

I'm about to change my wheels and tyres, it looks like modulars are at least 10Kg per wheel lighter than an average alloy, so does that mean better unsprung weight, which means better mpg, helps keep the wheel in contact with the road better etc? Has anyone changed from alloys to a modular/steel wheel and found it better?

Any experts out there?

shotgun0589 said:

Might be a daft question but I've heard people talking about the unsprung weight (mainly on motorbikes) and how much difference it makes to have lighter wheels/tyres.

I'm about to change my wheels and tyres, it looks like modulars are at least 10Kg per wheel lighter than an average alloy, so does that mean better unsprung weight, which means better mpg, helps keep the wheel in contact with the road better etc? Has anyone changed from alloys to a modular/steel wheel and found it better?

Any experts out there?

Click to expand...

I somehow don't think you will notice the difference in fuel economy by skimming 40kgs off a landys weight.

I've been looking this up and I've been told for every Kg that is removed from the unsprung weight, ie before the springs, then it makes the equivalent of 10x the difference of the sprung weight, so by losing 40KG, it's like losing the weight of 4 people in the car.
Maybe I'm just trying to convince myself to save some money and buy a set of modulars?!!

You won't really notice the difference in a landy, but when you get to push bikes, motorbikes, sports cars etc you can really notice the difference.

:5biagree:

Makes a big difference on bikes - I have put dymags on a couple and you really notice a change in the handling.

Landrover? Not so much. Think the ratio of sprung to unsprung is too big. But it can't hurt and may make the suspension respond better.


Oh and I don't think you notice any mpg improvement.

Cheers SpringDon, just wondered, I've raced bikes for years, given up now though, never got the chance to get any Dymags or Carbon wheels as I wasn't that good! Just thought I'd ask the question, the difference of 10Kg+ per wheel could potentially make a slight difference.

It's all said above ..

On lighter vehicles unsprung weight loss can make a massive difference, and it can also help in heavier vehicles that go fast, rally type fast I mean .. For Landrovers it really makes so little difference, unless you're competing, that it isn't usually economically viable. Of course, if you want a wheel change anyway, it _can_ be another good reason to pass on to whoever holds the purse strings!

When I raced model cars, unsprung weight was critical, similarly sidecar racing, but trials bikes it didn't matter, the speed necessary for suspension compliance made the weight only a small component.

That said, if you're in a stripped out trials machine with very soft springs, then again it might become critical to suspension compliance, but you'd have to be really good to notice the difference!

My modulars were much heavier than my alloys (not standard Landrover) but made no difference to handling that I could tell. The extra weight isn't noticeable either ..

10kg seems like a big difference to me, regardless of the effects and savings - are you sure a bare modular is 10kg lighter and the alloy in question??

As said, low unsprung weight on competition vehicles is key to good handling, but we're talking perhaps inboard shocks and springs, where every 100g might make a difference, not a landy with live axles and dirty great cast iron hubs.

Tom

shotgun0589 said:

I've been looking this up and I've been told for every Kg that is removed from the unsprung weight, ie before the springs, then it makes the equivalent of 10x the difference of the sprung weight, so by losing 40KG, it's like losing the weight of 4 people in the car.
Maybe I'm just trying to convince myself to save some money and buy a set of modulars?!!

Click to expand...

I have a set of almost new white modulars if you are interested.
Send me a PM if you are.

It does make a difference but as said on a landrover with heavy brakes, hubs, steering bars, diff guards and bloody heavy live axles and diffs that are all unsprung weight, it'll make feckall difference.

The axles and all the suspension, steering components, wheels etc or anything else that's unsprung on a landrover Defender for example probably accounts for close enough to half the weight of the vehicle if its 90 pickup with very little gear on it.

The only noticeable difference when changing from alloys to modulate is the drumming sound at speed, on my dads 90 when going from his everyday tyres on boost alloys to the offroad tyres on modulars they echo

It might make a difference to a fireblade or BMW M3 CSL. You really aren't going to notice on a couple of tonnes of Land Rover with the top speed, acceleration, aerodynamics and handling of a 1960s bungalow.

I have worked on Land Rovers since 1983 so have driven many and they all drive better on road on smaller wheels even new RR 405's are better on 19's, obviously the profile of the tyre has an effect
Also it isn't just the unsprung weight there is also the flywheel effect 4 big heavy wheels take more energy too accelerate.