Rim thickness - worn out?

[reohn2]

Bike supplied with black Moulton rims. After exactly 3008miles, I fitted the Sun CR18 rims. I still have the empty Moulton rims. Yet to measure them, but I will and report back.

1.5mm and 1.6mm
1.5mm was probably the rear one.


So .............. if we consider that 406 rims be they Moulton MT20 or SunCR18 wear similarly - not fact but maybe similar?
The rims wear 0.4mm per 1,000miles.

This would make the rims 2mm thick when brand new.
Does this sound correct?

Is my arithmetic about ball-park?

It can't be an exact science as the alloys used and the weather both types of rims were used in can differ greatly.

[Mick F]

It depends on WHY you ride a bike IMHO.
I wanted something "different" and I got it!

costly
maintenance hungry
quirky
easy to ride but hard work on the hills
comfortable
recognisable
fun
fits in the car easily

The hard work on the hills bit is an advantage to me. If riding a bike is too easy, you need to go further to get the same fitness benefit.
Hard work is good. Easy riding is just that - easy.





I know it's not an exact science about rim wear. There's no way I could tell you the thicknesses at brand new, and there's no way I could calculate the various brake block compositions or number of brake applications in what weather.

I reckon that 2mm is about the thickness at new for rims.
Anyone got a brand new rim of any size or make to measure?

If you know the mileage of your rims, you should be able to predict when they will be down to 1mm.

[reohn2]

It depends on WHY you ride a bike IMHO.
I wanted something "different" and I got it!

costly
maintenance hungry
quirky
easy to ride but hard work on the hills
comfortable
recognisable
fun
fits in the car easily

The hard work on the hills bit is an advantage to me. If riding a bike is too easy, you need to go further to get the same fitness benefit.
Hard work is good. Easy riding is just that - easy.

That sums up the Moulton and your reasons for owning and riding one,as I posted they're niche.
My post was not a criticism of you but of Moulton in the wider sense,the proof of which is because they're niche.If they were a better alround bike to the standard large(r) wheeled bicycle design they'de be more popular and would've overcome any prejudice cyclists may have had,they aren't and remain niche because they are an answer only for enthusiasts and converts for whatever reason all of which are valid for those converts and enthusiasts.

I know it's not an exact science about rim wear......

I know you know,but you did ask

EDIT post rewritten for clarity

[NATURAL ANKLING]

Hi,
2 mm thick rims, that's what used to get with mavics in bygone days
Will need to measure new rims, many I have measured start at 1.7 down to Even 1.3 mm, maybe more exotic stuff differ.

Like R2 says small wheeled bikes are a bit of a novelty, you are certainly a limited to what parts you can buy, Keeps you busy though

[reohn2]

Hi,
2 mm thick rims, that's what used to get with mavics in bygone days
Will need to measure new rims, many I have measured start at 1.7 down to Even 1.3 mm, maybe more exotic stuff differ.

Like R2 says small wheeled bikes are a bit of a novelty, you are certainly a limited to what parts you can buy, Keeps you busy though

I've never had a rim that measured more than 1.9mm and those were Sputniks,IIRC Mavic 519/719/217/221 were all around 1.7/1.6mm or less.

[Mick F]

Ok then.
Lets say 1.75mm when new.

1.5mm at 3000miles for the Moulton MT20 rims.
1.75 - 1.5 = 0.25mm
= 0.25/3000 = 0.083mm per 1000miles of wear.


However, Sun C18 at 1.75mm new and 1.1mm after 4100miles gives a figure of
1.75 - 1.1 = 0.65mm
= 0.65/4100 = 0.16mm per 1000miles of wear.

Twice the wear?
Is that reasonable?

[NATURAL ANKLING]

Hi,
I am going back further to Mavic module argent, they probably disappeared in the 80s.
I will check the thickness again, I I RC They were between 1.9 and two mil.

[Mick F]

I'm going to drop SJS Cycles a question about the original thickness of their CR18 rims.
See if they know!

[Brucey]

if this dwg is to be believed the thickness under the lips is roughly between 1.25 and 1.5mm when the rim is new.

cheers

[NATURAL ANKLING]

hi,
From the diagram you posted as little as 1.25 as suggested.
From the photo of the item it could be even less.
I'm not sure I'de been mounting them on my bike unless it's just the occasional shopper (rim brakes)
Oh, machine rims too?

[JohnW]

AIUI ..................

?

[JohnW]

IIRC ....................IME .................

?

[JohnW]

..............IMHO.....................

?

[JohnW]

Seriously, it's a good question - and a serious matter.
Many years ago - probably 40 or more - my rear wheel collapsed in the centre of Brighouse, on my way home from work.
I'd had to make a severe brake application, and it caused the heavily worn rim to disintegrate.
If it'd been on my front wheel, or at any significant speed, I could have been seriously injured.
The thought of it happening downhill makes me cringe.
Could be fatal.
I'm over cautious now.

There was a funny side to it. The acoustics were impressive.
First there was a springy "twang", and then a bang like a pistol shot, as the tube burst.
Then there was a cacophony, like the sound of a load of empty dustbins falling off the back of a lorry.
I was right by a 'bus stop, with waiting passengers.
One lady ran for cover into a shop doorway!

A friend with whom I often rode part way on the way home was riding behind me, and he said that it took him a second or two to realise what had happened.
He said that the pistol shot was accompanied by a puff of what appeared to be gunpowder.............I always apply plenty of French chalk, or cheap talc, inside the tyre when fitting it.
He'd stopped right by the 'bus queue, and it appeared that I'd really caused quite a stir.
No encores though.

Can't be careful enough.

[Mick F]

if this dwg is to be believed the thickness under the lips is roughly between 1.25 and 1.5mm when the rim is new.

Yes, I've seen that diagram a few times and I have a screenshot of the profile on my computer.

Scale is the issue, and the artist's impression. It ain't a photo of the cross-section.

If the rim was as thin as 1.5mm when new, I've nothing to worry about for quite a while as it's only worn 0.4mm in 4100 miles.
If it was 1.25 when new, I have even less to worry about as it's only worn 0.15mm in that distance.

Photo of rear rim when new.
It looks quite chunky ........... but looks can be deceptive perhaps?