Rim diameter vs tire diameter

[davidrouse00]

I own an XC 29er (Cube Attention SL).  The Schawbe Smart Sams it rolled off the floor with feel like running in dress shoes (way slippy).  I’d like throw on some more aggressive rubber but what I am seeing is most of the tires I’m interested in (Maxxis Aggressor, Minion) are 29 x 2.5 . The rims on my Cube are 29 x 2.25.

So my question is, with the proper amount of determination and profanity, could I mount the 2.5 tires on the 2.25 rim?

-David

[Jeff Barber]

You should have no problem mounting them. The only issue is the tire won’t be quite the right shape for the tread, at least according to the tire designers and engineers.

In practice though, it’s all about personal preference. I’ve run 2.6″ tires on 25mm rims and it felt fine to me, but to others it might not be as desirable as say a more appropriate 2.3″ tire.

Give it a try and let us know how it works out!

[Noggus]

First things first.  Check the specs for your fork and rear triangle to make sure 2.5″ wide tires will have proper clearance.

Second, what is the internal width of your rims?  There exist recommended rim to tire width ratios which you should take into consideration.  Here’s a link to the chart I prefer to reference that also includes maximum tire pressure recommendations – https://www.eastoncycling.com/media/Easton%20Rim%20pressure.pdf

[davidrouse00]

Thanks Noggus and Jeff.  Im going to do some more research first I think before I purchase.  I did find 2.3 varieties of the tires I wanted but after reviewing what Noggus linked, I may rethink this and throw on wider rims first.  Clearance wise, I think I should be fine by the looks of things but will break out the tape measure for that as well.

[Jeff Barber]

Good point Noggus. Fork clearance isn’t usually an issue, but rear clearance certainly can be. I found I can’t fit 2.6″ rear tires.

[Noggus]

Same deal for me. 2.35″ rear is what I’m running with very minor chainstay rub. Alloy frame so not a concern.

Also running 2.35″ up front and I am just now realizing my new front fork (15 x 100 fox 34) should fit 2.5″ tires. Hmmmm.  Thinking I might be shopping for a new front tire to try out this winter.

[Bike Nerd]

On any tire there is a range of rims widths that will work well with that tire width. The way to determine that rim width range is to convert tire width to mm(millimeters) then subtract 31mm to get the widest inner rim width. Then do the same but subtract 41mm to get the narrowest inner rim width. So for 2.5in tires:

2.5in x 25.4 = 64mm

64mm – 31mm = i33mm (i=inner rim width) widest

64mm – 41mm = i23mm (i=inner rim width) narrowest

So, any i23-33mm rim will work well with a 2.5in wide tire. Obviously, the wider rim will allow for the most volume, the least tire flop, and the lowest tire pressures. However, the wider rim does weigh more. If you already have say i25mm rims, I doubt you will be able to feel much difference in performance if you went to an i32mm rim. Save your money!

*This rule applies only to Mountain bike tires in the 2.0-3.2in range. Fat bikes, Gravel bikes, and Road bikes break this rule all the time.*

Here is a chart of some common tires widths.

3.0in tire i35-45mm rim
2.8in tire i30-40mm rim
2.6in tire i25-35mm rim
2.4in tire i20-30mm rim
2.2in tire i15-25mm rim
2.0in tire i15-20mm rim (i15mm is about as narrow as rims get.)

[davidrouse00]

So to finish the thread, I went ahead and purchased the minion DHF and the Aggressor.  the Aggressor went on easier than the minion but with a bit of effort I got both 2.3 wheels onto my 2.25 rims.   I took them for their first ride today and everything went great.  Thanks everyone for all your suggestions and advice, it is appreciated.

 

 

[TwiceHorn]

Sounds good.  But, as alluded to above, and a matter of nomenclature and more, there is no such thing as 2.25″ rims (well there may be, but they aren’t in common use on bicycles).  There are rims with 2.25″ tires on them, but that doesn’t tell you anything about the rims and therefore nothing about what tires might fit on them, other than the 2.25″ ones that are currently on it.

Looked up your bike and the rims are listed as ZX24, which I take to mean, most likely, 24mm internal width rims.  So, you can use the formulae provided by Plusbike Nerd to determine  what tires will go on your rims, but not necessarily your bike, which is also governed by frame and fork dimensions.

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