# Lower tire pressure on wider rims?

For a given tire width, can you safely run a lower pressure on wider rims?

Background:

My road bike can only fit up to 23 mm tires due to frame clearance, however my rims are a relatively wide 23 mm. So I was wondering if I can run a lower tire pressure than normal for a more comfortable ride without pinch flatting or damaging the wheels on bad pavement.

• No, rim too wide increases the chances of a pinch flat. Are you sure the frame can only take 23 mm? Aug 25, 2015 at 20:23
• So, if your rim was 2mm wider it would rub on your frame? Aug 25, 2015 at 20:57
• I guess you are talking about the 23 mm wide side to side? Rim width is measured by the inner distance, fyi.. Aug 25, 2015 at 21:37
• It's possible but uncommon to run tyres narrower than the rims, but you need high pressure as a rule.
– Móż
Aug 25, 2015 at 21:57
• To answer your basic question, rim width is only weakly associated with the "optimal" tire pressure. Aug 25, 2015 at 23:23

Running 23 mm tires on a rim width of 23 mm is insane -- your tires should be around to 40-50 mm.

To summarize Sheldon Brown's page:

Narrow tire on wide rim = pinch flats + damage from road hazards (which is the case you are in)

Wide tire on narrow rim = sidewall damage + rim failure and bad handling

You need to get a narrower rim for the bike (or possibly do a 650b conversion if possible, so you can run decent sized tires).

• Of course, Opie is probably measuring the outside width of the rims, when the "standard" measurement is of the inside width. The difference would be on the order of 5 mm. Aug 25, 2015 at 23:21
• This comment is simply wrong. HED has an entire set of rims (C2) where you run 23mm tires on 23mm wide rims (remember, that's external width). You also run lower pressures because the wider rim supports the sidewall better. But hey, what would HED know about safety? Apr 29, 2016 at 16:42
• @RichWagenknecht note that you are talking about rims with an outside width of 23 mm. The inner width is certainly considerably smaller. Unless specifically mentioned when only stating width of a rim the inner width is meant. Except for (exotic) deep section aero rims (eg HED's) the outside width is not particularily important. Nov 20, 2019 at 22:06
• 23c tires on 23mm (outside size) rims should work fine, I've seen it many times on road bike wheels, if however 23mm is the inside dimension of the tire seat you should take batman's advice, regarding the original question I agree with dlu Nov 25, 2019 at 19:44

No, you can run lower pressure on wider tires. Think about it this way: you need a certain amount of force holding the rims up off of the road. You can get if from a small contact patch and a lot of pressure or from a larger contact area and a lower pressure.

But as you increase the width of the rim the tire goes from an approximation of a circle to a box to a thin sheet of rubber – you loose the flexibility of the sidewalls that comes from the more or less circular shape of a properly matched tire to rim.