Reduce unsprung weight

What I always find amusing with regards to weight saving, is most blokes could do with losing a stone or two. By eating & drinking less they would save money & make their bike lighter. Spending a fortune on new bits for the bike certainly makes ones wallet a lot lighter!

Fullauto said:

That's not my experience. Having handled stock wheels with tyres fitted and one with a 2.5 inch Morad rim with tyre fitted, there is a significant difference in weight. This is at the same time, putting one down and picking the other up.

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The placebo effect? ;-)

No offence, Ken. There are not that many variables in the equation. I would trust my scale and simple math over my senses, anytime.

-Knut

Stock 1.85" x 19" steel rim 5 lbs 7.2 oz
Shouldered 1.85" x 19" alloy rim 4 lbs 2.5 oz.

In metric, about 668 grams ( 1.47 lbs)
A 2.15 or 2.5 shouldered alloy rim might weight close to the stock narrow steel rim.
By modern standards, the Commando is still a fairly light motorcycle.

mdt-son said:

The placebo effect? ;-)

No offence, Ken. There are not that many variables in the equation. I would trust my scale and simple math over my senses, anytime.

-Knut

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When I first scrapped the chromed steel rims and laced up shouldered alloys, I could feel an immediate difference in turning quickness and ease of handling. Reducing unsprung weight is the best thing you can do for ANY motorcycle. Ask any sportbike owner who has swapped their cast wheels for forged or carbon fiber.

That crafty Ludwig will be saving more with NON shouldered and four less spokes (each end ?).

Matchless said:

What I always find amusing with regards to weight saving, is most blokes could do with losing a stone or two. By eating & drinking less they would save money & make their bike lighter. Spending a fortune on new bits for the bike certainly makes ones wallet a lot lighter!

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What always amuses me is how some generalize and confuse. Unsprung versus sprung; not the same thing in the OP context. The OP inquired about unsprung weight. Unless you plan to hang on to and become part of the unsprung mass while riding, rider weight is irrelevant. On the other hand, if YOU want to improve the sprung to unsprung weight ratio - bulk up and have at it!

Time Warp said:

Stock 1.85" x 19" steel rim 5 lbs 7.2 oz
Shouldered 1.85" x 19" alloy rim 4 lbs 2.5 oz.

In metric, about 668 grams ( 1.47 lbs)
A 2.15 or 2.5 shouldered alloy rim might weight close to the stock narrow steel rim.
By modern standards, the Commando is still a fairly light motorcycle.

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Good information Time Warp and thanks. 1.47 lbs is significant. Would it be fair to say there would be a similar or even greater weight savings between a steel and aluminum 2.15 or 2.50?

If you want to explore going tubeless, one can drop another 3 to 4 lbs. There are kits out there to convert spoke wheels to tubeless. A local race shop has used them and I have not heard of any failures but I just don't have the level of comfort to try something like that on a system critical component until I see more history on it.

I have a rear wheel that came with a Colin Seeley Mk2 frame fitted with a disk brake. The rim was 18" alloy with very skinny (too skinny) spokes and aluminum spoke nipples. Previous life may have been a 7R. I never saw aluminum spoke nipples and will not use the wheel as configured - sure is trick looking sitting in my "bin of stuff" in the garage.

I know the original poster isn't interested in my modifications because my bike is indeed a "marriage" of bike parts. But, just to add perspective to the conversation, I went down the path you are asking about in an attempt to get as many improvements as I could. I adapted yamaha cast aluminum wheels to my commando. I also used an aluminum rear sprocket, tubeless tires front and rear, a fiberglass front fender. The yamaha brake disc is lighter than the lockheed disc. The yamaha rear hub is a modern cush drive set up too...

I'm sure my wheels are somewhat lighter than stock commando wheels. I'm not sure if they are as light as aluminum rimmed stock commando wheels. (I should weigh my set up to have an exact weight to compare against stock) It would be hard to make modifications and then claim you feel a significant difference, if it took you a week to get your bike back on the road. I believe if you swapped bikes for a side by side testing, you would notice some differences.

What does it mean in a practical sense?... probably not a lot since we're not pushing our bikes to their limits in a race, but ride quality will change incrementally. Every time you make an improvement, you get a little better performance. If you do enough improvements the differences begin to add up...

Recently, I swapped bikes with someone at the norton rally, The other rider, who rode my modified 750 thought my steering was lighter, quicker and better handling than his 850. I thought his 850 had greater low rpm torque than my 750, and was a rock solid bike, with a bit heavier, slower handling, but very stable going straight. I was surprised that he instantly felt a significant difference in handling in a positive way. I would have thought that the difference wouldn't be big enough to overcome the discomfort from going to opposite side foot controls, different sized handlebars and my rear sets, but he actually commented on the handling quality, which I attributed to my lighter unsprung weight, new roadrider tires, and my steeper '70 yoke geometry.

The differences add up, but aren't worlds apart... The more improvements you make, the more things add up.

I would be using WM3 (2.15") Alloys to replace the WM3 steels that are on there now with 4.10/19 Avons. So, as Dances noted, I would expect a similar difference between the steel WM3s that are on the bike now and the alloy. As he stated, 1.47 pounds is a good bit of difference.

Re sealed spoke wheels to eliminate the tubes...I'm thinking about that. I know folks who have done it with no issues using 3M 5200 but, for some reason, I'm a bit gunshy about it...not sure why. I'd probably buy one of the kits as opposed to going the 5200 route though I know from years of marine experience that it is excellent stuff. For that matter, it's probably better than whatever the kits contain though the kit stuff is probably much less messy to apply!

Saving weight at the rim is also different from saving weight at the hub due to the way centripetal forces work.

mdt-son said:

The placebo effect? ;-)

No offence, Ken. There are not that many variables in the equation. I would trust my scale and simple math over my senses, anytime.

-Knut

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No placebo effect. The wheels were right there. A direct side by side comparison.
You're wrong.

mdt-son said:

No. In a recent thread about rims, I documented that there is hardly any weight advantage in selecting alloy rims, unless you choose the super-light racing variety which is hardly suitable for a road bike. Yeah, go-faster items look nice but the reality bites you.

-Knut

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And what other items can contribute to unsprung weight? We weren't quantifying the saving, there will be some no matter how little, alloy rims of the same size as steel rims will weigh less!

Belt final drive wasn't something that came to mind for me, I agree it would be interesting to see how that stacks up.

Another alternative is Japanese lighweight rear drum wheel. 350 Honda wheels have been used in race bikes.

But how many really want to go that route?

I followed a Commando for a couple of hours this morning in a group run. Pretty stock bike, but I won't take much persuading he was having a more fun ride than me! I certainly enjoyed listening to it!

o0norton0o said:

I know the original poster isn't interested in my modifications because my bike is indeed a "marriage" of bike parts. But, just to add perspective to the conversation, I went down the path you are asking about in an attempt to get as many improvements as I could. I adapted yamaha cast aluminum wheels to my commando. I also used an aluminum rear sprocket, tubeless tires front and rear, a fiberglass front fender. The yamaha brake disc is lighter than the lockheed disc. The yamaha rear hub is a modern cush drive set up too...

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But on one of my race bikes I am changing the cast Yamaha wheels (discs front and rear) to wire spoked unflanged alloy rims on Yamaha hubs to reduce unsprung weight!

Matchless said:

What I always find amusing with regards to weight saving, is most blokes could do with losing a stone or two. By eating & drinking less they would save money & make their bike lighter. Spending a fortune on new bits for the bike certainly makes ones wallet a lot lighter!

Click to expand...

Good plan for my racing, losing a stone generally means getting fitter too, which always helps when racing, but like the man said, actual unsprung weight will be just the same!

SteveA said:

But on one of my race bikes I am changing the cast Yamaha wheels (discs front and rear) to wire spoked unflanged alloy rims on Yamaha hubs to reduce unsprung weight!

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Were you able to go with tubeless tires also to eliminate the weight of the inner tube?

*** There's a lot of physics involved in motorcycles. here's a link to a professor walter lewin video that is 49 minutes long, but it addresses the physics of rolling motion...

Time Warp said:

Shouldered 1.85" x 19" alloy rim 4 lbs 2.5 oz.

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May I ask which brand and version of rim you refer to? There are racing type of alloy rims and there are roadworthy reinforced alloy rims. In my book rims weighing 4 lbs + (1.85 kg) are racing type of rims, but I may be wrong. It's important to compare apples with apples ....

-Knut

o0norton0o said:

Were you able to go with tubeless tires also to eliminate the weight of the inner tube?

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On the cast wheels no, they don't have the right shoulder ridges for tubeless fitment.

Be careful with this. If a tubeless tyre becomes dislodged from the rim through pressure loss, instability will be instant....you won't like it! I have a road Yamaha that has a tubeless rear fitting and a tubed front fitting, that is the front wheel has no shoulder ridge to secure the tyre to the rim! Guess what? When I changed tyres soon after purchase tube type was clearly stated on the tyre, but there was no tube in the front! This is a dangerous condition.

Ironically, I have spoked alloy rims with shoulder ridges that secure the tyre but have to use tubes due to the spokes!

o0norton0o said:

*** There's a lot of physics involved in motorcycles. here's a link to a professor walter lewin video that is 49 minutes long, but it addresses the physics of rolling motion...

Click to expand...

Indeed, my maths isn't up to an in depth study of this subject, but at the age of 17 I started getting some education on avionics systems, including gyroscopes and gyroscopic precession!

That helped me understand the basics of steering a motorcycle.....

Shock absorbers also contribute to unsprung weight, this is what I just wrote on a separate thread:

"
A couple years ago one of my Hagons broke off on the first outing of a track weekend on my Slimline 850, box section swingarm, Manx forks. I went round the paddock to find a solution and a Nortonista friend lent me a pair of Fournales oleo-pneumatic shocks. It was an instant revelation, the handling was transformed while the Curve exit traction got significantly better!

Fournales shocks are extremely light units at about 900g or 2lbs. each, which lowers the unsprung weight significantly as a bonus. (As well as the bike's net weight of course).

Needless to say, I immediatly contacted the factory in Toulouse, France and ordered a pair. I must emphasize the responsiveness and professionalism of that company (they build shocks for a lot of applications, mainly aeronautics and racing cars and bikes, they build the units according to your bike specs and your weight. The units are beautifully finished with a classic look and have performed flawlessly for the last 3 years/20000km. The price is very competitive considering the quality and service.

More than highly recommended."

First I've heard of them - sound interesting!

Re that - I looked them up and I see a shock listed for "850 Commando" and shock with a different part number listed for "850 Commando Mk 2" Frankly, I don't know what a Mark II 850 is compared to an 850 but apparently something in the shock/mount is different. Is that correct?

Part MA 01 0198 is for 850; MA 01 0199 is for 850 Mk2