azza_333

Just a quick question what is everyone's thoughts in the ideal interior rim width for a 35c tire? I am finding a bit of conflicting information online. Thanks in advance.

rumrunn6

dunno but I was surprised when I got a 29er style MTB, which takes quite wide tires (seen here w/ 2.25" Riddlers) , has rims no wider than my Trek hybrids. the tires look kinda funny on such narrow rims but they don't fall off ...! :-)

mstateglfr 

Ill go with 23mm inner for 'ideal'. And then Ill add that anything from 17mm-26mm is common and totally fine in absolutely every single way. Ill go further and mention how 2.1" mtb tires were run on 15mm internal rims for ever and it wasnt an issue. The lightbulb shape may not be ideal, but its also not detrimental. People not only survived, but enjoyed riding in spite of such specs.

pdlamb

A quick web search for "bicycle tire rim width chart" gives 17-21 mm internal width. It's not critical; I'd be comfortable going a couple mm wider.

GamblerGORD53

Get Velocity Dyad rims, mine have machined brake tracks. NOTHING is better. They are about 23.5 outside. These are on all 3 of my bikes. The 650B one has 38 mm, the others 35.
Two have a front SA XL-FDD dyno drum brake, with 2.3/ 2.0 spokes. One has 27,000+ miles and still like new.
The medium pointy profile and NO stupid eyelets is the reason they are so perfect.

mstateglfr 

https://sugarwheelworks.com/blog/how...and-tire-size/ - says 21-26mm internal

https://www.wtb.com/pages/tire-rim-fit-chart - says 17mm-25mm internal

https://www.lightbicycle.com/newslet...cycle-rim.html - says 17-25 internal.


^figured I would link some industry info since my first post may sound a bit glib. Looking at the above numbers, I kinda nailed it in that first response. Go me- 5* for an answer.

chaadster

The thing about that term, ideal, is that it needs qualified. Ideal for aero? Cost? Handling? General use?

Pictured are Herse 35c Bon Jon Pass on 24mm internal Spinergy GX rims. To my tastes, this is a great matchup, largely because the handling is accurate and there is no perceptible sidewall slip when leaning the tire over in a turn. I do run fairly high pressure, though, which helps, but mainly it’s down to the way the width shapes the carcass. It’s probably not aero optimized, however, and were that the goal, I imagine we’d be looking at a very wide rim, probably close to 30mm internal, which is impracticable probably.

ThermionicScott 

I have a theory (but nothing solid to back it up) that the original ETRTO rim guidelines just intended to "complete the circle" of the tire's cross-section, given a particular nominal inflated width. For example, a 28mm tire with a circular cross-section would have a circumference of 88mm. If the tire has a bead-to-bead width of 70mm (usually 2.5 times the nominal width), then an arc of about 18mm remains to be made up by the rim. That works out to about 16.8mm across, which is 60% of the nominal tire width. But it would be unreasonably restrictive to limit each tire to one exact rim width and vice versa, so they allowed some latitude in each direction. If you work backward from the older ETRTO charts, you can see a recommended rim width range of about 50% to 69% (nice.)

But it's clear that lots of combinations outside of that range can work just fine. Fat MTB tires on skinny rims, and now skinny road tires on wide rims. So the ISO guidelines are always playing catch-up, and currently look kinda goofy and inconsistent as a result.

What was the question again?

Iride01 

Ideal how?

Cornering? Rolling resistance? Smoothing out bumps? Easy to change tires? Somewhat aero with rim? Looks good with rim? and etc, etc, etc.

https://www.bicyclerollingresistance...rim-width-test

scottfsmith

The one thing I never figured out about those charts is if you want to have deep section aero rims you don't want to have a big discontinuity between the tire and the rim exterior.. you want the rim exterior to be not much narrower than the mounted tire width. There is the mythical "105% rule" which states the tire should be only 105% of the rim width for optimal aerodynamics.

I have some 50mm depth aero rims and I got them with 25mm inner width (edited - not ID) since I was running 35c tires. The rims are 32mm wide (putting me at 110%, still over the 105% rule), that should be more aero than the 35c mounted on my road rims which are 28mm wide (125%, well over the 105% rule).

All of this is moot for non-aero rims, the charts seem fine for that.

azza_333

Ideal for comfort primarily, and rolling resistance secondarily.

chaadster

You probably mean IW (internal width), no?

chaadster

I guess it’s good news to you that neither of those things have much to do with internal rim width.

azza_333

Most of my concern was going to wide, and having decreased impact absorption (comfort), I don't think cornering grip will be effect since I run with slicks.

PeteHski

This^
I wouldn't worry too much about it. As I'm in the market for a new pair of road wheels myself, I had noticed that a lot of manufacturers are settling on 21 mm internal width for their latest rims, but some are going to 23 or even 25 mm. I would also say that most modern road wheels are likely to be optimised around 28c tyres, so 21 mm internal width is probably the sweet spot for those tyres. So for a 35c tyre, maybe a 23-25 mm internal width may be a slight advantage. It's also worth checking with the tyre manufacturers too. Most of them advise on internal widths.

azza_333

There are a lot of manufacturer charts online, but I understand that tubeless and non tubeless tires have different ID requirements. The charts don't mention if they are for tubes or tubeless though.

The 2 rims I am looking at are 21mm and 24mm. For touring I use 35c (Tubes), but for bunch rides I drop to 32c (Tubless).

chaadster

ID? You mean IW?

azza_333

I mean the internal width of the rim.

chaadster

Right…width, not diameter, ergo IW. ID is a different thing, like BSW (bead seat width) and ERD (effective rim diameter).

rumrunn6

just occurred to me, if one buys new wheels, one might consider the rim tape for tubed tires. the last time I bought new rim tape I had to measure wheels & the tape I had in stock at home. I've had occasion to change rim tape on the road while fixing a flat & having the right size for the wheels on the bike I was riding was important. on at least one occasion, at home I wound up trimming an entire length of new rim tape because I didn't want to put off the repair job until I could get new tape

pdlamb

I'll bite; why would you need to change rim tape to fix a flat on the road? Only time I've needed to replace good cloth tape was when, after too many spoke replacements, the adhesive was gone.

rumrunn6

not often but it has happened. but you touched on the key ... bought a used bike w/ cheap plastic rim tape. while changing the flat realized the tape moved & was exposing a spoke nipple which poked a hole in my tube. & that is was junk tape & couldn't be repositioned adequately. I'm sure I have a field photo, let me dig ... hmmm, that was easy





so if you buy new wheels, do they have good tape? do you have the correct size at home? should you buy rim tape w/ new wheels? was kinda what I was getting at

Flatforkcrown

that’s why most of my tires came with the tape already glued on.

Iride01 

Your tires have tape glued on them?

Flatforkcrown

yes, and then I glue the whole thing to the rim.