Roadgraveller

Hi,

I'm after a little advice

I have Cannondale Carbon HollowGram HG22 (622 25c) wheels which have an inner rim width of 25mm.
Currently I have 37c WTB Riddlers (tubeless).

I'm looking at a bit more road riding and wonder if I could fit Continental GP5000 Tubeless 28c tires or it that a little too narrow? Should I size up to 32c? I don't want them coming off.

It's mega hilly where I live so want to give myself the best chance of getting up'em.

Cheers
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Barrettscv 

A 28mm tire will fit the rim correctly. I would recommend the 32mm size to maintain some on-gravel versatility, and only considered using them on gravel that is hard packed. I have the prior generation GP 4000 in the 700x28 size these measure about 31mm. If the gravel is firm and well pcked, the tires are sufficient. Once the gravel becomes loose, progress becomes slow and hazardous.

Roadgraveller

That's great thank you, I was worried the profile of a 28 might be a little squashed on a 25mm inner width rim, or worse still come off. But if you've run them and they were fine that gives me the reassurance I was looking for.

aggiegrads

A narrower tire on a wider rim is at greater risk for pinch flats than if were on a narrower rim.

I don’t notice any difference in speed between 28s and 32s, but I do notice more comfort and grip on 32s.

Roadgraveller

Thanks, I think maybe 32s might be a better choice. Roads where I am can be a little bumpy.

Gconan

Tire & Rim Fit compatibility Chart

Steve B.

I run Conti Grand Prix 4 Season 28’s on WTB ST i23 TCS, 28h rims, whose width is 24mm. On these rims these 28 tires actually end up at 31mm.

Roadgraveller

Great thanks for sharing, it's all good background info. I'm pretty new into cycling so still loads to learn.

westrid_dad

I'm running Continental GP5000's 700 x 28 tubeless on my road wheelset (622 x 22). I run them between 60-70 psi, and they are very comfortable and fast enough for me. When it is time to replace them, I may go for the 700 x 32 size for some additional plushiness.

katsup

I'd be cautious running 28-32mm tires on a 25 internal width rim. You'll probably be fine, and I have personally never seen any issues, but it is not suggested by manufactures.

Longfellow02

Newbie to all this...can you please explain why manufacturers would not suggest a 28-32 mm tire on a 25 internal width rim ? thanks !!​​​​​​

katsup

I'd imagine for the same reason the OP mentioned, higher risk of the tire becoming unseated.

aggiegrads

When I think about the profile of a tire mounted on a too-wide rim, I envision a “flattened” vs round profile. This would result in higher forces applied axially (pressure times larger area) and a proportional loss of lateral force which keeps the tire seated on the bead.

Steve B.

And yet I’ve read that you get a better aerodynamic profile with a wide rim and tire near the rims width. So somehow that works.

aggiegrads

Most 25mm rims have an overall width greater than 30mm.

Recalling a conversation with a very experienced wheel builder, the advantage is a properly matched rim/tire vs a tire with a too-small rim. That would cause a “lightbulb” profile, which has a poor aero shape.

Even if there is no aero advantage, you are still at higher risk for pinch flats.

Oso Polar

These wide aerodynamic rims are usually much wider outside than inside. For example, the just announced Roval Rapide CLX (https://rovalcomponents.com/products/rapide-clx): 35 mm outside width, only 21 mm inside. I've used 32 mm GP 5000 on 23 mm internal width rims without any problems (manufacturer recommends minimum 35 mm). They were true to size (unlike GP 4000 that usually run larger).

JamesW74

Hi, I’m facing exactly the same dilemma with the same wheels! Can’t decide how narrow you can go. Some websites say that even the 37c they ship with are on the boundary of being safe, including WTB (whose tires they come with!). Did you go for something narrower and how did you get on?!

Wilbur76

I would try to consult the wheel manufacturer’s product support on your specific model. My Industry Nine wheels have 24.5mm inner width but minimum tire size is 33mm (running 40 rn).

chas58

Wilber has good advice. Go by the ETRO chart and if you go outside the boundaries, know the risks and how to mitigate them (the chart is very conservative, IMHO, so don't think you have to stay in the range).

a 28mm GP5000 on a 24mm ID rim is a poor combination. I've done it on a 22ID rim with the much larger 28mm GP4000. In hard cornering, I'm off the tread cap and cornering on the sidewall. Not what the designers had in mind. It also exposes me to sidewall gashes that a narrow rim would protect me better from. So, yeah, you can do it - but you open youself up to potential problems. Also, when going outside the range of the chart below, avoid extremely high or low pressures. You are going beyond what was designed for the tire/rim interface, and at the extremes, you are more suseptible to a tire blow off (high pressure) or having the tire lose its seal to the rim (low pressure).

Gconan

Roadgraveller

Hiya, yes I ignored the ETRO chart, it's dated and hasn't kept up with modern wider aero wheels.
Here's a few pages which should give you some comfort (I'm now on https://www.schwalbe.com/en/road-rea...be-pro-one-tle 30mm tyres and my wheels have a huge 25mm internal rim, not easy to inflate but great tyres for the road).
https://www.enve.com/en/lp/tire-compatibility/ click SES AR which shows you can go as narrow as 27mm on a 25mm inner width wheel.
https://www.3t.bike/en/products/whee...2-ltd-637.html these recommend 28mm to 30mm tyres.
I hope this helps.
J.

shoota 

Holy crap you guys are making this way too complicated. Pick the best 28-32mm tire you can find and slap them on there. Done.

Roadgraveller

You'd think it should be that easy but some of the manufacturers like Envy don't advise the use of some tyres like continental GPs probably because they might come off.

fishboat

38mm Panaracer Gravelking slicks. Lightweight, fast, cushy ride and good on gravel as well as roads.

chas58

shoota - It is too complicated, because there are no good standards and a lot of variables that conflict with each other. Multiple things have to match to get the tire to mount and stay mounted.

In Enve's case, you can use a GP5000, but you can not inflate it to its maximum pressure on the sidewall. Continental (and everyone actually) does not approve of going more than 5bar on a hookless rim. Conti have stated it is fine to use them hookless below 5 bar (which is what I do).

Some brands like Stans, & probably anyone hookless, tend to make the rim diameter a tad bigger than its nominal diameter. Conti makes the bead as small as they can in pursuit of high pressure safety. The result is that it is darn near impossible to mount the tubeless Conti GP on some of these rims.