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Discussion Starter · #1 ·
So I just picked up a Specialized Diverge, it comes stock with Roval Control SCS wheels and Roubaix 25/28 tyres.

On the wheels themselves there is a sticker that says minimum tyre width 30c. Given that the tyres that came with it are 28's, is this an issue at all? Seems strange for Specialized to provide stock equipment that don't seem to fit from a minimum requirements perspective.
 

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Bianchi-Campagnolo
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Bianchi-Campagnolo
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It would be nice if ERTRO could upgrade their chart.
 

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Adorable Furry Hombre
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OP, narrow tires != faster tires. Needing higher inflation pressure to not pinch flat it is actually the other way around.

It would be nice if ERTRO could upgrade their chart.
Since when did anyone care what the ETRTO said about anything?
 

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You got the wrong tires with your bike. Depending which level you got it should have had 30's and/or 32's.
I'd take it back and get the tires you should have gotten. Presumably you bought that type of bike not for racing but riding where 32ish tires are beneficial.

Anyway, 28 is definitely fine on a 21 internal rim. 25 should be fine too but I'm only 99.9% sure of that one.
 

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Banned Sock Puppet
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OP, narrow tires != faster tires.
This was the old way of thinking, but has since been debunked. It may still be true if you are talking about perfectly controlled road surfaces. In the real world, not necessarily true.

In fact, wider tires actually have less rolling resistance. Given that is offset by greater weight and more aerodynamic drag. In the end, when you're talking about differences between 23c and 28c, they pretty much cancel each other out as far as speed is concerned. So if I am not gaining or losing any speed by moving up to a more comfortable 28c tire that I can use less pressure in, it's a no-brainer.
 

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This was the old way of thinking, but has since been debunked. It may still be true if you are talking about perfectly controlled road surfaces. In the real world, not necessarily true.

In fact, wider tires actually have less rolling resistance. Given that is offset by greater weight and more aerodynamic drag. In the end, when you're talking about differences between 23c and 28c, they pretty much cancel each other out as far as speed is concerned. So if I am not gaining or losing any speed by moving up to a more comfortable 28c tire that I can use less pressure in, it's a no-brainer.
I think he was trying to type ≠
 

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Bianchi-Campagnolo
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OP, narrow tires != faster tires. Needing higher inflation pressure to not pinch flat it is actually the other way around.



Since when did anyone care what the ETRTO said about anything?
April 1st, I know.
 

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Discussion Starter · #14 ·
You got the wrong tires with your bike. Depending which level you got it should have had 30's and/or 32's.
I'd take it back and get the tires you should have gotten. Presumably you bought that type of bike not for racing but riding where 32ish tires are beneficial.

Anyway, 28 is definitely fine on a 21 internal rim. 25 should be fine too but I'm only 99.9% sure of that one.
When I first started reading up on this bike, the default tyre was the 32 Roubaix, but not sure in what market or country that is, the specs on the Australian Spesh site actually list the tyre as the 25/28, so it came as per the spec, but why I was surprised to see the sticker on the wheel.
Not sure if you can access this site, but this is the page here in Oz https://www.specialized.com/au/en-au/bikes/road/diverge-pro-cen/107476

i was there when they pulled the bike out the box, so definitely what it came with
 

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Discussion Starter · #15 ·
I heard back from Specialized Australia - apparently the sticker is there for overseas markets. That doesn't make all that much sense to me, but was the answer that I was given and that my 25/28's are fine on those wheels.
 

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Discussion Starter · #16 ·
So further to this now, was just looking at some tyres from Challenge Chicane which are 33mm wide.
The specs state a rim width of 15-19mm, my Rovals are 22mm, is this a no-no?
 

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So further to this now, was just looking at some tyres from Challenge Chicane which are 33mm wide.
The specs state a rim width of 15-19mm, my Rovals are 22mm, is this a no-no?
You won't have any issues running up to 40-45mm tires, and beyond, with those rims. Mountain bike rims used to be the same internal width as road rims (17-19mm) and there were never any real issues with stock 2.1-2.25 inch tires.

As far as going to something more narrow, I personally wouldn't run skinnier tires than the external width of my rims.
 

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So further to this now, was just looking at some tyres from Challenge Chicane which are 33mm wide.
The specs state a rim width of 15-19mm, my Rovals are 22mm, is this a no-no?
No it's fine. I really don't know where some of these tires companies get such outrageous information from.

Those are great tires by the way. I found it amazing how much they don't seem to slow me down on the road at all yet are pretty good in the muck and loose stuff off road.
 

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Discussion Starter · #19 · (Edited)
Thanks guys, I would never have considered tyre / wheel compatibility just a few years ago and it wasn't until I read this on the Challenge website that got me thinking about it "Yes, you need to be careful of how you pair tires and rims! As wider rims gain popularity, the industry is forgetting the compatibility standards and education is lacking about pairing rims and tyres"

No it's fine. I really don't know where some of these tires companies get such outrageous information from.

Those are great tires by the way. I found it amazing how much they don't seem to slow me down on the road at all yet are pretty good in the muck and loose stuff off road.
They do look like they tick a lot of boxes, I have actually just ordered a pair of Conti CX Speeds, but think the Chicanes will be next on the list to try. They are hard to find around here (not a great number of them online either) and not all that cheap. Where did you get yours from?

edit: i found some Chicanes on sale on the Bike24 website, so just ordered a pair of them too :)
 

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I suppose those old tire compatibility charts were more for older rims with straight sides and no "hooks" to help hold the tire on the rim. I could see a smooth sided rim letting the bead creep up and off the rim if the pull from the tire was quite vertical.

But the newer wide rims hold the tires in place. I'm running "tubeless ready" HED Ardennes+ rims. The beads "pop" into place while they are being inflated, and kind of lock in there. Those rims measure 25.5 mm wide on the outside, and 20.6 inside width. I use GP4000S 23c tires, which measure about 26.5 mm on the rim. It's been working great.
 
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