Time to replace rim?

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Jay Gee
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Time to replace rim?

Postby Jay Gee » 31 Dec 2020, 8:38pm

I noticed that my rear rim brake track (H+ Son archetype) has become rather concave. Measured today, the thickness is down to 0.6mm in places. I can't see any kind of wear indicator. Is it time to swap the rim?

Brucey
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Re: Time to replace rim?

Postby Brucey » 31 Dec 2020, 8:58pm

yes, time for a new one; many rims split before they get that worn.

cheers
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Jay Gee
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Re: Time to replace rim?

Postby Jay Gee » 31 Dec 2020, 9:22pm

I thought that might be the case, thanks.

iandusud
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Re: Time to replace rim?

Postby iandusud » 1 Jan 2021, 10:29am

Try pumping your tyre up to 100 psi and stand back :D

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iow
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Re: Time to replace rim?

Postby iow » 2 Jan 2021, 9:38am

I think those rims have a wear indicator, but at 0.6mm it's probably long disappeared!
mark

Jdsk
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Re: Time to replace rim?

Postby Jdsk » 2 Jan 2021, 9:50am

... who else read that and pondered a wear indicator wear indicator?

; - )

Jonathan

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Chris Jeggo
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Re: Time to replace rim?

Postby Chris Jeggo » 2 Jan 2021, 10:49am

A 'wear indicator' is either a wear non-indicator or a non-wear indicator.

Brucey
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Re: Time to replace rim?

Postby Brucey » 2 Jan 2021, 10:55am

Chris Jeggo wrote:A 'wear indicator' is either a wear non-indicator or a non-wear indicator.


depends what sort it is...?

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Chris Jeggo
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Re: Time to replace rim?

Postby Chris Jeggo » 2 Jan 2021, 11:06am

Brucey wrote:
Chris Jeggo wrote:A 'wear indicator' is either a wear non-indicator or a non-wear indicator.


depends what sort it is...?

cheers


True! I'd forgotten about the other sort.

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Mick F
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Re: Time to replace rim?

Postby Mick F » 2 Jan 2021, 3:59pm

iandusud wrote:Try pumping your tyre up to 100 psi and stand back :D
Rear tyres on my bikes are 120psi on one, and 100psi on the other.

The Moulton rear is at 100psi ......... or it is each time top it up and ride it.
The rim is worn, and I've discussed this on here on a thread somewhere. Give me some time, and I'll find it.
I was so concerned about it, that I bought a new rim ................ still not needed even though I bought it in Oct 2019.

Found it! :D

Taken from this thread.
viewtopic.php?f=5&t=133217

Mick F wrote:Bought two CR18 rims 28h and 36h.
Measured the brand new ones. 1.5mm.
This means that my rear one at 1.1mm after 4000miles = loss of 0.4mm = 1mm wear per 1000miles.
Therefore I could well have 1000miles left before it gets down the magic 1mm.
I'm going to run my wheels to destruction. It may not be until early next year, but the new rims are ready and willing to take over.


Given that it was Oct 2019 @ 1.1mm @ 4000miles and I've not ridden Moulton so much as before .........
The bike has now done in the region of 8,500miles and had done 3,000miles when I fitted these rims, they are 5,500miles down the line, so could well explode next time I pump them up.

I doubt it very much indeed..
If I feel so inclined tomorrow, I'll take out the rear wheel, remove the tyre and tube, and measure again.
Mick F. Cornwall

iandusud
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Re: Time to replace rim?

Postby iandusud » 3 Jan 2021, 9:50am

Mick F wrote:
iandusud wrote:Try pumping your tyre up to 100 psi and stand back :D
Rear tyres on my bikes are 120psi on one, and 100psi on the other.

The Moulton rear is at 100psi ......... or it is each time top it up and ride it.
The rim is worn, and I've discussed this on here on a thread somewhere. Give me some time, and I'll find it.
I was so concerned about it, that I bought a new rim ................ still not needed even though I bought it in Oct 2019.

Found it! :D

Taken from this thread.
viewtopic.php?f=5&t=133217

Mick F wrote:Bought two CR18 rims 28h and 36h.
Measured the brand new ones. 1.5mm.
This means that my rear one at 1.1mm after 4000miles = loss of 0.4mm = 1mm wear per 1000miles.
Therefore I could well have 1000miles left before it gets down the magic 1mm.
I'm going to run my wheels to destruction. It may not be until early next year, but the new rims are ready and willing to take over.


Given that it was Oct 2019 @ 1.1mm @ 4000miles and I've not ridden Moulton so much as before .........
The bike has now done in the region of 8,500miles and had done 3,000miles when I fitted these rims, they are 5,500miles down the line, so could well explode next time I pump them up.

I doubt it very much indeed..
If I feel so inclined tomorrow, I'll take out the rear wheel, remove the tyre and tube, and measure again.

Hi Mick,
But are they down to 0.6mm as in the case of the OP? (BTW My post was a bit tongue in cheek but I have seen a rim split with a huge bang on a bike whilst it was being ridden on a club run. I can imagine how it happened. The guy drags his bike out on Saturday morning pumps the tyres up rock solid...)
I don't know what rims you have on your Moulton but the 17" Mistral rims fitted on the earlier AMs have a lot of meat on them. I don't really remember worn out rims being an issue back in the day (whenever that was) but I think that in the quest to make rims lighter, and with better alloys, rims have got to be much thinner than they were and I find myself rebuilding my wheels much more frequently (or maybe I'm just getting older and use my brakes more :D )

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Mick F
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Re: Time to replace rim?

Postby Mick F » 3 Jan 2021, 11:06am

Are they down to 0.6mm?
Dunno yet.
Just having a cuppa and a sit-down before going back into the wood to collect some logs I've just cut up.

Happy days! :D

I'll get Moulton upside down this afternoon and check the rear rim out. I'll also be giving the cheap Nutrak tyres a look-see.
£3odd a tyre and I have four spare! :D
Mick F. Cornwall

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Mick F
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Re: Time to replace rim?

Postby Mick F » 3 Jan 2021, 2:51pm

Done it.
Rear wheel off, tyre off and tube out.
Swanson Gauge says 1mm.

Checked a brand new one, and that's 1.5mm.
So, if (say) 0.5mm is the final end, it means my rear rim is half-way through its life. It's lost 0.5mm out of a total wear available of 1mm maximum.

Is this correct, or am I looking at the idea wrongly?
Mick F. Cornwall

Brucey
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Re: Time to replace rim?

Postby Brucey » 3 Jan 2021, 3:30pm

at the kind of pressures/tyre widths you run I'd be thinking about changing the rims whenever the thickness measures less than 1.0mm.

The strength of the rim goes as the cube of the remaining wall thickness. This means (for example) that a rim that started out 1.5mm wall thickness is already about 1/3rd that strength when it is worn to 1.0mm and once it is worn to 0.8mm it is half that strength, so 1/6th of the original strength.

If you measure any given thickness, you have to reckon that (because the thickness is never uniform) there will probably be other areas which are at least 0.1mm thinner again.

One way of assessing the state of the rim is to compare the width of the rim (at the lips) with the tyre inflated and deflated. More than about 0.3mm difference would be cause for concern.

BTW by 'Swanson' gauge you presumably mean Iwanson gauge...?

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Mick F
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Re: Time to replace rim?

Postby Mick F » 3 Jan 2021, 3:40pm

Thanks Brucey!

Yes, it isn't a Swanson Gauge ......... but it sounds better eh? :lol:

I've refitted the tyre etc and it's now back up to 100psi.
What I should do now, is measure the rim width, let the tyre down and measure it again.
I have a 1" micrometer that'll do it nicely, though my digital callipers would be easier perhaps, plus being more relevant in this metric day and age.

Give me a few minutes or so, and I'll do it .................. in the interests of science or course! :D
Mick F. Cornwall