Bike rims – explain width differences and benefits

So new bike day for my wife, needs a wheel set and we need to explain to her the benefits and negatives of rim width. Please help with a simple way to explain this to a highly intelligent individual-skilled rider who is not grasping mine or daughters explanation.

New bike is a stage Evo….from PSA….we have option of

25mm internal width

30 mm internal width

Or smaller and bigger.

All help appreciated

Narrower rims will be lighter and less strong because there is less material in them. Conversely wider rims will be heavier and stronger.

Narrower rims will fit narrower tyres better, wider rims will fit wider tyres better.

Narrower rims will be lighter and less strong because there is less material in them. Conversely wider rims will be heavier and stronger.

Narrower rims will fit narrower tyres better, wider rims will fit wider tyres better.

Basically that.

With the caveat that 30mm isn’t really all that wide. If it was a decision between 25 and 35 then the drawbacks of “too wide” might have been a factor, but I’d say 30mm is pretty goldilocks for a ~2.4″ tyre.

As above, for most people, most of the time, on typical trail bike tyres – 30mm is about right.

A 2.3/2.4 will be more stable on a 30mm rim at lower pressures than a 25mm rim too.

And a narrower rim isn’t necessarily weaker than a wider one, that’s more about the type of rim you buy (XC or DH). You can’t go too far wrong with 30mm as most modern tyres are built to work best with that width rim.

Its funny, i re-listened to the NSMB podcast with Chris Porter the other day and he was talking about the advantages of running a 25mm rim over 30mm rim – basically saying they were faster and that 25mm gave the tire a better profile.

He seemed to think most of the world cup downhillers were running EX471 rims at 25mm (even the ones sponsored by AN.Others) this was back in 2021 though!

I’d agree with the others though. Most people will go 30mm inner width – i know i just did (XM481s)

30mm is pretty much the standard width now. Quite a few fast riders are running 25mm, especially on the back, for the rounder and thus faster rolling, tyre profile.

Stiffness and strength are independent width, there’s no consistent correlation.

Cheers all.

She is thinking 35mm front and 30mm for back wheel.

IMO 35mm inner width on the front is too wide unless you’re planning on using 2.6″ tyres. Bigger tyres will be more comfortable but are a bit more vague when it comes to cornering than narrower equivalents.

Just to be awkward I think 27/28mm is the perfect width for 2.4 tyres, choice of 25 or 30 then definitely 30mm, you can’t go too wrong there, 35mm is for 2.6 and over imho.

The industry and tyre manufacturers seem to have settled on 30mm id. You can happily run 2.25 up to 2.6 which I would say covers most riders nowadays.

Bigger tyres will be more comfortable but are a bit more vague when it comes to cornering than narrower equivalents.

I disagree with vague. 2.8 on the front here on my HT and with the right (low) tyre pressure it corners like it’s on rails. The tyre is not even that great (some Bontrager thing) but I can really push it on anything and it grips like anything. Downside: weight and slow rolling (relative) on hardpack.

FWIW on a recommendation I put some 650g, 30mm internal width rims on a light XC 29er about 13 years ago and I expected them to be ott compared to the skinny Mavics I’d been using, in fact combined with 2.4 tyres ~18psi it was one of the best things I’d changed on my bikes in a long time. It was the last of any light wheel XC weenie-ism in me I think.

I think for most weekend riders, most of the time, 5mm in the width of your rim makes sod all difference, and if you think it does is mostly placebo. How well the wheel is built is going to make a bigger impact on how the bike rides.

I run a 30 on the front and a 25 on the rear.  My rear has a little less room than the front so i fut a slightly narrower tyre.

For the avoidance of doubt, i dont do this beacause im fast.

I doubt I could actually tell the difference between the same tyre on a 25mm or 30mm rim if we’re talking a 2.3 or 2.4” tyre. With bigger tyres than that you can see from the profile of the tyre on a 25mm rim that it’s on a rim that’s ideally a bit too narrow, but in reality they work ok.

My hardtail has winter wheels with 30mm internal and summer wheels with 25mm internal (I was trying to make a light fast but strong wheelset with the 25mm ones – XM421 on Erase Components hubs) – I tend to run 2.6” tyres on both wheel sets for the cushioning effect of bigger volume. Both ride fine.

On my other bike it’s 30mm back and front – got a set of XM481 rims on one wheelset and a mix of EX511 rear / XM481 front. I normally use 2.4” Contis but equally have used 2.3” / 2.5” / 2.6” Maxxis

Depends what tyres you are running.

I run 2.4 DHR’s on 25mm rims, yet a 2.5 assegai on a 25mm ends up too rounded, so run a 30mm.

Narrower rims will be lighter and less strong because there is less material in them. Conversely wider rims will be heavier and stronger.

DT Swiss has you covered, different widths at the same rim model.

I’d go 25mm, drop a bit of weight and make life easier on the ups. Also don’t go fitting slow sticky tyres, pick something sensible. You don’t need an asseagi/mary/argotal for trail centres !

i feel 25mm is a thing of the past, (ignoring pro’s which isnt real world) 28mm/30mm for 2.4-2.55 tyres

strength is more to do with the materials and construction, my old hope enduro wheels dented on second ride, sure they were 25mm internals..

24mm internals on gravel bike for win..

30mm is pretty much the standard width now. Quite a few fast riders are running 25mm, especially on the back, for the rounder and thus faster rolling, tyre profile.

And some slow riders as well (me for one).

a narrower rim isn’t necessarily weaker than a wider one

Yes, please ignore that first response.

A 25mm EX471 rim (my first choice for rear) will absolutely not be weaker than most 30mm rims.

A narrower rim can allow for more material to be placed in the areas prone to damage, while retaining the same weight as a wider one.

He seemed to think most of the world cup downhillers were running EX471 rims at 25mm (even the ones sponsored by AN.Others) this was back in 2021 though!

Watched a bike check vid a week or two ago, might have been the Pivot or Norco pits. Chief mech said they’d tired a bunch and always came back to 25mm, most of the field was the same. Interviewer asked why 30mm was pushed so hard and he gave a sort of a sheepish shrug and a smile!

Pace, pressure and lean angle maths are different for  DH pros compared to recreational riders, but probably 30mm is oversold for anyone trying to go fast downhill with pressures over 20psi.  What are XC pro racers riding, I wonder? Off to Google…

(I went for 30mm on the last 3 sets I’ve bought)

30mm front, 25mm rear here. Usually XM481 front and EX471 rear

Chief mech said they’d tired a bunch and always came back to 25mm, most of the field was the same. Interviewer asked why 30mm was pushed so hard and he gave a sort of a sheepish shrug and a smile!

Interesting – though I suppose full-on DH carcasses are pretty un-foldy compared to a trail one (and DHers probably don’t ever go above 2.4s either, do they?)