single skin steel vs double skin alloy rims?

jimmyhackers

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ive managed to blow out the side of my dual skin 20" bmx hub rim. (see pic)

20220626_190433[1].jpg

needless to say, i need to replace it and would like something more durable.
im probably going to fit a disc break to the rear now aswell. (need to weld a bracket to the frame)

just wondering if a single skin steel rims as comparable strength-wise to a double skin alluminum?
 
jimmyhackers said:
ive managed to blow out the side of my dual skin 20" bmx hub rim. (see pic)

20220626_190433[1].jpg

needless to say, i need to replace it and would like something more durable.
More durable will depend on your specific usage scenario, and what you get vs what you have.

For instance, if you are using rim brakes, they wear away the surface of the rim over time and eventually the rim can be thin enough that high tire pressures especially combined with hard riding on rough surfaces (potholes, curb jumping, etc) could cause a rim fracture along the most-worn area.

Low tire pressure along with impacts (potholes, curbs, etc) can also break rims like that.

Some rims are made stronger, though I don't know which specific models are better than what you have; you can look thru Chalo's posts on rims and wheels to see which ones he recommends, though.

just wondering if a single skin steel rims as comparable strength-wise to a double skin alluminum?

Not for the weight. The aluminum rim is stronger and lighter, and it will also fit the tire bead better since it's extruded to a shape specifically for that, and the steel rim is just rolled at the edges.
 
yep, that was an inwards dent due to low tyre pressure. no crack. i usually run at 50psi but had a slow puncture and was at 10psi by the end.

it had been fine for months then the other day i noticed it was now an outwards dent and had cracked :(

im not too fussed about weight, its more strength/durability, i was kinda hoping a steel rim would be a cheap alternative. i can get a pair for 30 quid or one alloy rim for £50+
 
jimmyhackers said:
yep, that was an inwards dent due to low tyre pressure. no crack. i usually run at 50psi but had a slow puncture and was at 10psi by the end.

it had been fine for months then the other day i noticed it was now an outwards dent and had cracked :(
Unfortunately that's just a common failure mode for aluminum. (steel could do that too, just less likely...but if you bend a rim from an impact, then you might expect it to eventually fail further from the repeated stresses the bend will now see that are different from the loading it would have had when undamaged. Every bump even small ones change the pressure in the tire slightly, which changes the pressure of the bead against the rim. Each increase pushes outward on the rim, and the damaged part will push differently than the rest, whcih flexes it along the change in shape, and that over time increases the fracturing, until it gives way and does what you see now.

I've bent a few rims this way by hitting unavoidable (and sometimes unexpected) sharp-edged deep potholes while riding in traffic, and the one thing I've found that will make them fail even faster and in a worse way (peeling the side off the rim!) is to attempt to bend them back straight, so don't do that if you do ever bend another rim. ;)
 
There are signs that the rim has been abraded by brake pads that wore down to their metal backings at some point. When this happens, the metal core of the pad cuts a groove in the rim that can become a failure point. This is one of those times that you should not simply ignore that noise and hope it goes away.

Some rims have a wear indicator line extruded into them, to show when the rim has been thinned enough to require replacement.

If you want to replace the rim but reuse the spokes, you'll need to find a rim with similar effective rim diameter (ERD). You can measure this value yourself with a little patience and some extrapolation, or you can have a bike shop do it for you.

Those spokes look like they're too thick for bicycle rims (thicker than 14 gauge or 2mm diameter). If so, you may as well replace them too, and choose from a wider selection of rims that may have different ERD. BMX freestyle rims are the best value for strong 20” wheels. There are many to choose from. You'll want one with rim brake compatible sidewalls.

To the nearest approximation, all steel bicycle rims are garbage that should be avoided. They are structurally, frictionally, thermally, and dimensionally inferior to even the crudest aluminum rims.
 
thanks for info, i havnt gone to metal on the pads every :p ....i just ride a 30-40mph in muddy/sandy/gritty places.
i go through a set of pad cartidges every month or so. needless to say it will be disc brakes on the rear from now on.

my price range options appear to be either a halo sub-4 rim for 40 quid or a gusset trix for 33quid.

https://www.ebay.co.uk/itm/123806839692?epid=10028232770&hash=item1cd376738c:g:jHkAAOSwGJpiE7Ha

https://www.ebay.co.uk/itm/115387979811?hash=item1adda8d823:g:UHsAAOSwpQpihNfh

my head says halo but my wallet says gusset. any educated guesses on which will be stronger?
 
jimmyhackers said:
https://www.ebay.co.uk/itm/123806839692

https://www.ebay.co.uk/itm/115387979811?

my head says halo but my wallet says gusset. any educated guesses on which will be stronger?

Given that the Halo rim is positioned as a race model and is called Sub-4 (under 400g?), I think the Gusset is a better bet.

You can get better deals on beefier rims, if ERD isn't a factor:
https://www.sourcebmx.com/collections/bmx-rims/products/mission-honor-rim
 
ive just had a measure of my spokes and spoke nipples width. 2.4mm and 4.3mm respectively.

problem is i cant find anywhere the size of the eyelet holes in the halo, gusset or that honor wheel.

a bit annoying as the gusset and the halo have steel eyelet inserts (so i cant drill them out).

does anyone know thier sizes?
 
jimmyhackers said:
ive just had a measure of my spokes and spoke nipples width. 2.4mm and 4.3mm respectively.

problem is i cant find anywhere the size of the eyelet holes in the halo, gusset or that honor wheel.

a bit annoying as the gusset and the halo have steel eyelet inserts (so i cant drill them out).

does anyone know thier sizes?

Your spoke nipples will fit, but won't gimbal as far as if you were using normal 2.0mm spokes with 4mm nipples. In some cases this might cause the spokes to kink where they exit the nipples, and later break at the threads. You probably can't know whether it's problem before you lace up the wheel.
 
thanks for the info

just googled "gimbal" and its not just a thing for cameras :lol:

i figure you mean that they wont accept an "off" angle as easily?
i.e. the smaller hole will mean it less accepting of not 90 angles

i guess that wont make so much of a problem as the spokes on this tiny wheel are all at a "90" to the rim/hub with no crossovers?

im leaning towards the gusset trix... between the three its the heaviest (by 50g), is the medium width 32mm (halo was 30mm, mission was 36mm) has the ERD closest to my exsiting rim.
 
jimmyhackers said:
i guess that wont make so much of a problem as the spokes on this tiny wheel are all at a "90" to the rim/hub with no crossovers?

Probably won't be an issue. If there's a limitation, it will be in allowing however much lateral bracing angle you have. If that's a problem, you can lace inside the flange instead of outside the flange, to reduce the bracing angle.
 
well....the spoke nipples didnt fit through the eylets in the gusset trix rim.

yay :(

not all is lost....i can use it for a front rim, once i use up all my spare v-brake pads and rims :p
i suppose by then i may of gotten round to making the front a disc brake too. should be easier as the mounts are already on the forks, just gotta find the right length spokes and a suitable front disc hub.

ive ordered the mission honor rim....at least i can drill that one out if the hole are too small.
 
UPDATE! finally got round to getting the right size spokes, 65 quid from ebay alex warick cycles. 36x sapim 12g spokes at a 75mm length.

wheel went together like a dream, partly thanks to the spoke driver tool i purchased.
20230315_165310[1].jpg

only had to drill out all 36 spoke holes to 5mm and debur everything. I couldnt be bothered to clean the hub after it all :D
 
UPDATE! finally got round to getting the right size spokes, 65 quid from ebay alex warick cycles. 36x sapim 12g spokes at a 75mm length.

Those are not the right size spokes. I guess you decided to treat yourself to more of the same problems you've already been dealing with.

14 gauge or thinner spokes. Easy and cheap. Or you can choose expensive trouble, and use thick spokes.
 
the only problem i had with the original 20" rim was that i dinked and snapped a lip (low tyre pressure), the spoke holes are/were fine.

i guess i will find out how well it holds up with the thicker spokes.
 
been for three rides now.... as expected the spokes had a little "stretch/loosening" after the first ride.​
re-tightened them and they've been behaving on the subsequent other two rides.​
 
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