Minimum Rim Wall Thickness

For discussions about bikes and equipment.
Jim77
Posts: 113
Joined: 20 Nov 2022, 1:13am

Minimum Rim Wall Thickness

Post by Jim77 »

Hi all

What is the minimum thickness of a rim that is safe to ride on? In other words at what thickness should the rim be replaced after wear from rim brakes?

Thanks in advance.
User avatar
Mick F
Spambuster
Posts: 56359
Joined: 7 Jan 2007, 11:24am
Location: Tamar Valley, Cornwall

Re: Minimum Rim Wall Thickness

Post by Mick F »

It's a good question.
I have a thread on here - long one? - asking that very question.
viewtopic.php?t=133217

Wot I did, was to buy a pair of rims some years before, and when I was in doubt the worn ones, I re-rimmed the wheels with them, and recycled the worn ones.

As for minimum safe thickness, it's a moot point methinks.
Mick F. Cornwall
Jim77
Posts: 113
Joined: 20 Nov 2022, 1:13am

Re: Minimum Rim Wall Thickness

Post by Jim77 »

Thanks Mick - I will have a thorough read of it. On a quick initial skim through it seems that anything less than 1mm should be replaced.
gxaustin
Posts: 890
Joined: 23 Sep 2015, 12:07pm

Re: Minimum Rim Wall Thickness

Post by gxaustin »

I had an Open Pro rim which gave up at a smidge under 1mm. Nowadays I check with my Iwanson gauge and re-rim or junk at 1mm. If the rim has a wear guide I go by that.
Jim77
Posts: 113
Joined: 20 Nov 2022, 1:13am

Re: Minimum Rim Wall Thickness

Post by Jim77 »

gxaustin wrote: 7 Dec 2022, 4:49pm I had an Open Pro rim which gave up at a smidge under 1mm. Nowadays I check with my Iwanson gauge and re-rim or junk at 1mm. If the rim has a wear guide I go by that.
Thank you for your advice.
Jim77
Posts: 113
Joined: 20 Nov 2022, 1:13am

Re: Minimum Rim Wall Thickness

Post by Jim77 »

Just measured with Iwanson gauge and one side is at 1mm so will replace definitely - especially as already rebuilding the wheel.

Interestingly the other side of the rim was a fair bit more than 1mm.

Presumably because the brake calliper was applying more force to one side more than the other?
User avatar
cycleruk
Posts: 6065
Joined: 17 Jan 2009, 9:30pm
Location: Lancashire

Re: Minimum Rim Wall Thickness

Post by cycleruk »

Jim77 wrote: 7 Dec 2022, 5:14pm Just measured with Iwanson gauge and one side is at 1mm so will replace definitely - especially as already rebuilding the wheel.

Interestingly the other side of the rim was a fair bit more than 1mm.
Presumably because the brake calliper was applying more force to one side more than the other?
Would it be a good idea to turn the front wheel around now and again.
Swap the skewer round to the other side and turn the tyre as well if it's directional ?

Wouldn't work on the back obviously.
You'll never know if you don't try it.
richardfm
Posts: 969
Joined: 15 Apr 2018, 3:17pm
Location: Cardiff, Wales

Re: Minimum Rim Wall Thickness

Post by richardfm »

It would be a better idea to balance the brakes properly so that they apply equal pressure to both sides
Richard M
Cardiff
Jim77
Posts: 113
Joined: 20 Nov 2022, 1:13am

Re: Minimum Rim Wall Thickness

Post by Jim77 »

richardfm wrote: 7 Dec 2022, 7:14pm It would be a better idea to balance the brakes properly so that they apply equal pressure to both sides
How is this done?
richardfm
Posts: 969
Joined: 15 Apr 2018, 3:17pm
Location: Cardiff, Wales

Re: Minimum Rim Wall Thickness

Post by richardfm »

Jim77 wrote: 7 Dec 2022, 7:15pm
richardfm wrote: 7 Dec 2022, 7:14pm It would be a better idea to balance the brakes properly so that they apply equal pressure to both sides
How is this done?
That depends on the type of brake. If it's V brakes it's by using the adjusting screws for the spring tension to ensure that both pads are an equal distance from the rim and the brake arms move the same amount when the brake lever is operated.
Also when mounting the wheel ensure it is central, an equal distance from each fork at the rim.
Richard M
Cardiff
PT1029
Posts: 1744
Joined: 16 Apr 2012, 9:20pm

Re: Minimum Rim Wall Thickness

Post by PT1029 »

If you have dual pivot brakes (1 pivot in the centre, 1 off to one side), the arm with it's pivot off to one side have a greater mechanical advantage than the other arm. Thus the pad on that side of the brake exerts a greater force, so wearing the pad/rim faster than the other ride of the rim.
Jim77
Posts: 113
Joined: 20 Nov 2022, 1:13am

Re: Minimum Rim Wall Thickness

Post by Jim77 »

PT1029 wrote: 7 Dec 2022, 8:04pm If you have dual pivot brakes (1 pivot in the centre, 1 off to one side), the arm with it's pivot off to one side have a greater mechanical advantage than the other arm. Thus the pad on that side of the brake exerts a greater force, so wearing the pad/rim faster than the other ride of the rim.
Yes it is a Tiagra dual pivot brake.
Steve
Posts: 388
Joined: 2 Apr 2007, 1:42pm

Re: Minimum Rim Wall Thickness

Post by Steve »

The two sides may not have been the same thickness from the start, and often the thickness of one side itself varies. Something to do with the manufacturing process I believe.
User avatar
cycleruk
Posts: 6065
Joined: 17 Jan 2009, 9:30pm
Location: Lancashire

Re: Minimum Rim Wall Thickness

Post by cycleruk »

Jim77 wrote: 7 Dec 2022, 7:15pm
richardfm wrote: 7 Dec 2022, 7:14pm It would be a better idea to balance the brakes properly so that they apply equal pressure to both sides
How is this done?
With Shimano dual pivot brakes there is a little grub screw in one of the arms. (The one opposite the cable.) This is used to take up any slight adjustment of the brake pads.
An easy quick check is to pull on the brake lever while watching the rim to see if it moves sideways. If it does then the brake needs adjusting.
For my initial setting up of the brakes or if they are out by a lot :-
Slacken the main centre hold screw/bolt just enough so the unit is free to rotate. Pull on the brakes with a bit of force so that the brake shoes really clamp the rim. Now, while still holding the brake lever, retighten the bolt. This usually works fine for me and normally needs no fine adjustment.
Before doing any adjustment make sure the wheels are seated properly.
You'll never know if you don't try it.
TheBomber
Posts: 525
Joined: 16 Feb 2020, 8:18pm

Re: Minimum Rim Wall Thickness

Post by TheBomber »

I always used to find with dual pivots that when set up correctly (as described above) the pads would make a sort of slapping noise when they hit the rims.
Post Reply