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Fitting thinner tires to rims with 20mm internal width

Old 03-23-18, 07:28 AM
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disq
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Fitting thinner tires to rims with 20mm internal width

Hi,

Can I fit 25mm tires to a 20mm-internal-width wheelset?

The tires I'd like to fit are Michelin Pro4's (SC or Endurance)

The rims are Swiss E1800 and/or R470db 's, profile is 20mm internal, 24mm external width, and 23mm depth.

I know that I probably shouldn't, 20mm x 1.4 multiplier gives me 28mm as the minimum recommended tire size on these rims, but what would happen if I did? Would it be dangerous? Bead sitting trouble? More punctures?

Cheers!
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Old 03-23-18, 07:33 AM
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Well, thinner tires would likely lead to more punctures, but narrow tires on a wide rim could lead to pinch flats, as the tire will have a flatter profile. Also, higher speed turns may be less stable. I don't see a good reason to do it, and please don't cite weight. I see the Pro 4's do not come wider that 25mm, but there's nothing magical about them. Wider tires have low rolling resistance, fewer flats, are easier to mount, and neither rolling resistance nor the miniscule weight difference are major factors in going faster or easier.

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Old 03-23-18, 07:39 AM
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A 25c tire is too narrow for a 20 mm rim, IMO.

According to Stan's NoTubes, running a tire that's too narrow for the rim "decreases impact absorbing ability, cornering control, and exposes sidewall to cuts."
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Old 03-23-18, 08:10 AM
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I originally ran 23mm on my Hed Belgium rims, which are 19/23 wide. No problems at all. In fact I put a 23 on my front wheel again last April since I had a new one left. It's been fine with about 5500 miles on it now. So your 25 should work. I run 25s now since I am a believer in the wider tire lower pressure concept. They measure 28 mounted on the Heds. I'd go wider if my frame could accommodate.
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Old 03-23-18, 08:14 AM
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I don't think 25 mm tires on those rims would be a hazard but, as recommended above, 28s would be a better match if your frame and fork have the clearance.
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Old 03-23-18, 08:57 AM
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It won't be a problem.

Cervelo sells high-end R5 bikes with 21 mm inside width HED Ardennes Plus rims and 25 mm Continental tires. 20 or 21 mm inside width rims with 25 mm tires is a great combination. Lots of guys are running this and my next road bike will have this exact combination.

Not only will it work fine but it will handle really well and look great.


-Tim-
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Old 03-23-18, 09:09 AM
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Tufo Tubular-Clinchers? https://www.biketiresdirect.com/prod...lincher?sg=500
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Old 03-23-18, 11:09 AM
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Originally Posted by disq View Post
Hi,

Can I fit 25mm tires to a 20mm-internal-width wheelset?

The tires I'd like to fit are Michelin Pro4's (SC or Endurance)

The rims are Swiss E1800 and/or R470db 's, profile is 20mm internal, 24mm external width, and 23mm depth.

I know that I probably shouldn't, 20mm x 1.4 multiplier gives me 28mm as the minimum recommended tire size on these rims, but what would happen if I did? Would it be dangerous? Bead sitting trouble? More punctures?

Cheers!
Go for it!

I have a spare Mavic A119 wheel with a 700x23C tire on it @110psi in the basement. I get pretty similar numbers to your scenario. (25/20=1.25, 23/19=1.21) Tire measures a healthy 25mm in practice thanks to the extra width.

ETRTO guidelines are an attempt to say "this absolutely will work", but it's very possible to go outside of them with success. Especially with tubeless-ready rims that capture the bead more securely than older-style ones.
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Old 03-23-18, 11:17 AM
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It'll be fine. I'd run 28s if they could clear though.
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Old 03-23-18, 01:38 PM
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If you are not pushing max weight on the bike or you do stuff that imposes more than average loading on the tires, such as riding down steps, then you might be okay. Once you go for things that aren't specifically recommended by the mfr, you are experimental IMO. Not that that is bad. I'm experimental quite a bit. Especially when someone tells me I can't.

Mavic has lot of info on their site that many others don't. Here is a chart from one of their articles showing that you'd be a size or two off from their recommended....


But even in their article that this appears they say that it's just a recommendation, not a limit. THE RIGHT TYRE WIDTH ON THE RIGHT RIM WIDTH - Engineerstalk : Engineerstalk
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Old 03-23-18, 01:44 PM
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I wasn't expecting such variety of opinions. Reading the first replies I thought "not worth it" but now I'll give it a go.

The thing is I have a pair of lightly-used 25mm Pro4 tires from my previous bike, which had "Axis Sport Deep" oem wheels (sizing/profile info unknown, but probably in the same range) and I'd like to continue using them. Current 28mm tires are Conti Grand Prix "SL" which is not common, it might even be Canyon-specific. And has weak braking performance in wet weather. (maybe I started going faster so it skids more?)

BTW I'm nowhere near the max weight. Thanks for the info.

Last edited by disq; 03-23-18 at 01:47 PM.
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Old 03-23-18, 01:53 PM
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I'd keep them pumped up. Less tire width might increase the risk your rim might get damaged by sharp bumps, pot holes and such that the sidewalls would otherwise protect with a wider tire at lower psi.
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Old 03-23-18, 04:24 PM
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Originally Posted by disq View Post
I wasn't expecting such variety of opinions. Reading the first replies I thought "not worth it" but now I'll give it a go.

The thing is I have a pair of lightly-used 25mm Pro4 tires from my previous bike...Current 28mm tires are Conti Grand Prix "SL" which is not common, it might even be Canyon-specific (??). And has weak braking performance in wet weather.
It is a fact that running a too-narrow tire will make your tire/rim more vulnerable to impact, and will provide a less desirable profile for turning at speed. No facts have been suggested to refute that reality. There are opinions that it's "OK" but nobody can actually do the balancing of pro's and con's for you. It appears that the only positives are that you have the tires and you like them. That's fine, but don't confuse facts with opinion.
As for braking performance, there's certainly nothing to indicate that the Pro4's will brake better than the Conti's.
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Old 03-23-18, 06:10 PM
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They run wide anyhow.

25mm pro4 measure 27.5mm wide on my 17.5mm internal rims.
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Old 03-24-18, 03:10 PM
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The funny part of all these responses expressing caution that a 25mm tyre might be a problem is the those rims are specifically design for 25mm tyres

OP, run 25mm tyres without fear, unless you're thinking the DT engineers are chumps....
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Old 03-24-18, 03:37 PM
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Actually unless there is a misprint somewhere in DT-Swiss's publications, then I'd have to say that 28mm is the smallest that they recommend with the 20mm internal width.

https://dycteyr72g97f.cloudfront.net...WEB_ZZ_001.pdf

But as the OP already has the tires and rims, along with the fact he's not pushing load weight limits they probably be okay. As someone else mentioned turns might be a little more squirrely unless the OP's been riding the wider tires at a high pressure and is used to that handling.

But it's not IMO a big safety issue. And as far as this and other posts being opinion, well yes they are. Even the safety standards are someones opinion about how safe something should be.

Last edited by Iride01; 03-24-18 at 03:40 PM.
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Old 03-24-18, 06:54 PM
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I've run 23mm GP4000S on my HED Ardennes Plus rims for a couple of years. The rims are 25.5mm outside, and 20.6 mm inside width. These 23mm tires measure 26mm on the rims. Yes, the tire is only about 1 mm wider than the rim. They work great. I use 80 psi front and 95 psi rear.

These rims are "tubeless ready" (I use tubes) so the bead snaps into the rim with a sharp pop sound when first inflated. I feel a little more secure that the tire won't come loose, even though the sidewall is almost vertical at the rim. In fact, I had a pinch flat after hitting an egg sized, sharp edged stone at 30 mph. The beads stayed locked on the rim after it flatted.

I've run 25mm GP4-seasons on the same rims. Those measured 29mm! It was a very plush ride at 65 psi front, 80 psi rear.

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Old 03-24-18, 08:24 PM
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It will not be a problem.

Charts are BS and you can find 25 mm tires on 20 mm inside width rims everywhere. People are running 32's and 35's on 21 mm wide rims.

It is a non issue. Put them on and enjoy.


-Tim-
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Old 03-25-18, 12:35 AM
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HED Ardennes Plus with 23's

My son put 23mm Michelin Pro Endurance on his HED Ardennes Plus wheels so I called HED to see if that was ok. They said that rim was designed for 23mm tire. I put the same tire in 25mm on the same rims. I like my setup and he likes his. Our respective tires both gained a couple of mm width on the wide rims.
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Old 10-01-22, 05:21 AM
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I have a variation on this question. I have 26" wheels on my MTB with 20 mm internal spacing between the rims. Can I use a 1.5" or even narrower tyre on these wheels. Is there a risk of the tyre detaching? I'm not worried about the increased risk of flats.
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Old 10-01-22, 06:09 AM
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Originally Posted by Eugbug View Post
Can I use a 1.5" or even narrower tyre on these wheels. Is there a risk of the tyre detaching?
1-1/2 inch is fine on those rims. You can probably go as narrow as 28 mm but IMO ride quality will suffer and you'll not go any faster, unless you're light and can run lower pressures.
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