25mm tires on 21mm ID rims - open tubulars an issue?

Discuss light weight issues concerning road bikes & parts.

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guadzilla
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Joined: Sat Mar 19, 2011 6:55 pm

by guadzilla

So I bought a pair of my tried and trusted Veloflex Master 25s to put on a pair of incoming Lightbicycle AR36 wheels, and just realized that Veloflex doesnt recommend them on rims with an inner diameter of over 17mm. That got me looking, and I noticed that my CLX64s are 21mm ID and while I currently have S-Works Turbo 26s on them, I was planning to put Turbo Cotton 24s on them and apparently THAT is a no-no, by ERTO standards.

I've been running 23s on my old wide-rim HED Jet 9s for several years, and nothing has assploded yet. But those are regular clinchers and I use them mainly on flat or rolling roads. The Lightbicycle wheels are specifically for climbing, and i expect to be doing a lot of hard cornering in them - I have always used "regular width" Al rims for this, and this is the first time i am using a wide carbon rim here (yay for disc brakes). Is having the tire blowing off the rim a legit risk - especially open tubulars like Veloflex Masters*? The rims are normal tubeless-compatibles - not the hookless variant.

I've just decided to upgrade my bikes recently - man, it has gotten complicated with compatibility and stuff. I need to find some CX riders and yell at them to get off my lawn. :)

[*I am aware of Veloflex and their stated "dont wmork with carbon rims" statement. I am specifically looking to get info on tire blowout risk]

by Weenie


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naylor343
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by naylor343

This last season I have been using that tyre on a 20mm ID rim, all the time in the high mountains too with lots of high speed cornering, no issues at all.

guadzilla
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by guadzilla

naylor343 wrote:
Fri Dec 27, 2019 5:12 pm
This last season I have been using that tyre on a 20mm ID rim, all the time in the high mountains too with lots of high speed cornering, no issues at all.
Ok, that's good to know. I had them on my HED9/disc combo without any issues, but the TT bike doesnt really get cornered too aggressively - glad to know that the Veloflex holds up on mountain descents.

Thank you for that.

bm0p700f
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by bm0p700f

Your thinking about it wrong. Veloflex will have an ideal tyre shape for there tyres and range of Internal widths that give that shape. As a general rule for tyres that sit at 25mm wiee or thereabouts 21mm is to wide as these rims force them to sit wider witha flatter top. This changes how the tyres wears and alter the contact patch a bit.

It's not a blow off risk.

Everyone needs to remember back 20 years ago 21mm internal width rims where for down hill mtb tyres. Mavic 721 where what I had
I put a 2.3" on them.
Last edited by bm0p700f on Sun Dec 29, 2019 9:07 pm, edited 1 time in total.

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naylor343
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by naylor343

bm0p700f wrote:
Fri Dec 27, 2019 6:01 pm
Your thinking about it wrong. Veloflex will have an ideal tyre shape for there tyres and ranger of rik I ternal widths that give that shape. As a general rule for tyres that sit at 25mm wiee or thereabouts 21mm is to wide as these rims force them to sit wider witha flatter top. This changes how the tyres wears and alter the contact patch a bit.

It's not a blow off risk.

Everyone needs to remember back 20 years ago 21mm internal width rims where for down hill mtb tyres. Mavic 721 where what I had
I put a 2.3" on them.
Totally understand the reasoning behind this, but luckily I have not come across any issues with wear, also cornering grip and speed appears unaffected. Obviously this is how they feel to me as it cannot be measured. The corsa does sit with a very nice round profile when mounted.
Funnily I find my previous tyres I used with these rims, 25mm pro4's which are far bigger tyre and should be more suited to this rim, these wore out far quicker, the rear squaring off quite quickly. Running them with vittoria latex tubes I found them more comfortable than the pro4's too. I am currently trying to find out the bead to bead measurement of the 28mm veloflex, hoping it would sit between the corsa 25 and the pro4 25 as far as width goes.

As for the older rims, I am still using my 26" 717's. Still going strong, hard to believe they are 17mm inner width!

Hexsense
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by Hexsense

Then follow Veloflex's advice or switch tire brand. Very likely, while it works, Veloflex feels that they don't have center tread wide enough for their safety margin when using wide rim.

However, if you look at Vittoria Corsa G2.0 and many other recently updated tires, they all increase the tread width and decrease carcass width in comparison to prior versions. So those would be fine to stretch more on wider rims.

In any case, please ignore ETRTO standard. It is a standard written conservatively decades ago for wire bead tire on hand built rim with lousy manufacturing tolerance, NOT precise kevlar bead on tubeless compatible rims.

JoO
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by JoO

No issue running vittoria Corsa 25c on velocity quill 622-21 rims

JoO
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by JoO

No issue running vittoria Corsa 25c on velocity quill 622-21 rims

Pierre86
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by Pierre86

The tire failures veloflex and other open tubulars suffered was from sharp carbon beads slicing soft sidewalls, something the newer SPS should prevent.

The width of the rim shouldn't make the tire more susceptible to blowing off, though I suppose it might unseat easier when flat?

I've done 500k using 25 masters and Belgium+ rims, 20.5 I'd, no issues, brilliant tire
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S5 Aero

c60rider
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by c60rider

Interesting I didn't know Veloflex said not to use 25mm masters on rims bigger than 17mm internal width. I've been using 25mm Masters on Mavic Open Pro UST rims for 2 years oblivious to this and with no problems. Official internal width is 19mm but actual appears to be 18.6mm but still more than they recommend :noidea:

guadzilla
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by guadzilla

Thank guys. I'll give them a go on the wide rim - but i will pay attention to the size of the center tread, to make sure it is suitable for the shape of the tire when mounted.

by Weenie


bm0p700f
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by bm0p700f

naylor343 wrote:
Fri Dec 27, 2019 6:33 pm
bm0p700f wrote:
Fri Dec 27, 2019 6:01 pm
Your thinking about it wrong. Veloflex will have an ideal tyre shape for there tyres and ranger of rik I ternal widths that give that shape. As a general rule for tyres that sit at 25mm wiee or thereabouts 21mm is to wide as these rims force them to sit wider witha flatter top. This changes how the tyres wears and alter the contact patch a bit.

It's not a blow off risk.

Everyone needs to remember back 20 years ago 21mm internal width rims where for down hill mtb tyres. Mavic 721 where what I had
I put a 2.3" on them.
Totally understand the reasoning behind this, but luckily I have not come across any issues with wear, also cornering grip and speed appears unaffected. Obviously this is how they feel to me as it cannot be measured. The corsa does sit with a very nice round profile when mounted.
Funnily I find my previous tyres I used with these rims, 25mm pro4's which are far bigger tyre and should be more suited to this rim, these wore out far quicker, the rear squaring off quite quickly. Running them with vittoria latex tubes I found them more comfortable than the pro4's too. I am currently trying to find out the bead to bead measurement of the 28mm veloflex, hoping it would sit between the corsa 25 and the pro4 25 as far as width goes.

As for the older rims, I am still using my 26" 717's. Still going strong, hard to believe they are 17mm inner width!

You probably wont notice but I have noticed 25mm conti gp5000 to tyres on 20mm internal width rims wearing with a "hollow" in the centre. That's not right. Found that on other tyres that have been mounted on rims that are really too wide for them. Grip is not affected.

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