Conti GP 5000 35C: a new standard for road frames?

[cateto]

Okay, so I've been tinkering.

The 35mm GP5Ks have only just arrived so I don't know how they ride yet.
Observations - They are very easy to fit on a 25mm internal and feel much more secure on a 32mm internal.
To the point that regardless or ETRTO I wouldt ride them on the two 25mm internal wheel sets I have.

To date my fauoured set up is the 32mm GP5K clincher on the 32mm internal.

a 32mm nominal tire on a 32int rim is wild
Keep tinkering please

[POTOOOOOOOO]

That's very interesting. This is what makes we wonder when people state tyre width X is faster/slower/more comfortable/... than tyre width Y.
There is so much variability in WAM for a certain tyre that people might be talking the same but mean something differently and vice versa.

Did you also measured tyre height?

I knew someone would ask for the height 🤓 no, I didn’t.

I currently have the 35s on the 32int and the 32s on a 25int. I can measure those but I can’t be bothered to swap everything around again for all permutations.

[Takiyaki]

I did some math around how to estimate EW given a tire's claimed width and the rim's IW

https://weightweenies.starbike.com/forum/viewtopic.php?p=1968122

Formula is (Tire Size)*(.6708 * IW/TS + .5192)

So for POTOO....'s presented combos the estimated EWs would be:

TS   IW   EW
30   25   32.097
32   25   33.1188
32   32   37.8144
35   32   39.3471
35   25   34.6515

Def not perfect, Im wondering if the relationship isn't linear and I'll play with regressions some more. I think the most accurate way to figure it out would be to measure bead to bead but that obviously comes with other issues. Maybe an approximation based on IW, EW and tire height etc actually mounted and inflated. Etc. etc. But I think it's definitely possible to know what WAM a tire will have on a rim ahead of time.

And yea a 0mm gap between tire size and IW is a little crazy for me. I like to stay around 3mm or bigger.

[POTOOOOOOOO]

I’ve seen your work on WW. Well done 👍🏼
I tend to just try things rather than calculate as there seems to be so many variables involved.

The 32-32 combination was an experiment but I’m amazed at how well it performs, how well it feels and how securely the tyres are held in the rims.

Maybe not for everyone but I feel more secure ridding those than other ETRTO compliant combinations I’ve tried before.
We all make out judgements and we are all adults.

I trust my own judgement over anything else

To my eye the 30mm on a 25int looks to be the same profile/shape as a 32mm on a 32int

[rosteven]

If I didn't already have a pair of 32s Id be all over this for my long distance wheels. Im glad some wheel makers are finally getting with the program, but Elitewheels and a bunch of others still have 28 EW as their standard. I feel like 31-32 EW is the new minimum.

And yea I figured out a rough formula for estimating WAM from tire width and rim IW...... on the max -4 Id feel safe with (figuring 28c tires on a 24 IW rim so 31 IW for these) I wouldnt be surprised if these got to 38-39 WAM. These will really need generous frame clearances to run safely but there are def options out there. I think 32s are prob the new standard.

My EliteWheels Gravel SLR have a 45mm depth, with an EW of 34mm and IW of 24mm. And they also now have a new Gravel Aero+ wheel with a 45mm depth with an EW of 40mm and IW of 32mm (which is a real chunky boy).

[Takiyaki]

My EliteWheels Gravel SLR have a 45mm depth, with an EW of 34mm and IW of 24mm. And they also now have a new Gravel Aero+ wheel with a 45mm depth with an EW of 40mm and IW of 32mm (which is a real chunky boy).

I have seen those. I think I will still go XMCS for my next wheelsets. If Elitewheels updated their road wheels to 32-34mm EW and offered a no logo option theyd have a slam dunk budget wheelset.

[Serge_K]

I m trying to buy a wheelset for a gravel bike i have, that can run a 35C road well (aero + safe). Have come across this rim profile from Serenade / 7tiger, 50 deep, IW 28, EW 38.
afaik, ETRTO says 35C is max 27 IW, but given they're too dumb to differentiate hooked and hookless, safety wise, i'd ride a 35C on a hooked 28 IW over a 27 IW hookless all day, every day.

And so, because a 32 IW is very far off ETRTO standards and arguably well into dangerous territory (emphasis on arguably, it's not really tested, and it's above my pay grade), this is the 1st OEM rim so far i find that can legit run a 35C with aerodynamics in mind, AND safety (at least on paper).

38 EW is narrower than i'd like by 1-2mm, but the market is very new, it's bleeding tech stuff (afaik). It just came out, it's not in the catalogue for 2026-2027, fwiw. Lead time is 30+ days.

If anyone has come across 50-60mm rims with similar features (c.28 IW, 38-40 EW), please shout.

[Takiyaki]

Im not crazy about how the rim pinches in at the bead. 28IW and 38-40EW will either require a very thick hook or a rim profile that really bulges out. XMCS has a 32.5/40 IW/EW rim that could work with arguably a better profile IMO.

https://www.xmcarbonspeed.cc/products/cs-d53cu-41-disc-brake-carbon-hooked-gravel-rims-325mm-internal-width

[Serge_K]

Im not crazy about how the rim pinches in at the bead. 28IW and 38-40EW will either require a very thick hook or a rim profile that really bulges out. XMCS has a 32.5/40 IW/EW rim that could work with arguably a better profile IMO.

https://www.xmcarbonspeed.cc/products/cs-d53cu-41-disc-brake-carbon-hooked-gravel-rims-325mm-internal-width

There are lots of options that are 32 IW, 38-41 EW, but as per earlier in this thread, 35C w 32 IW is very far off ETRTO standards and therefore highly questionable. I'm not in love with that Serenade rim profile that caves in, but it's the best i've seen so far with these specs. I assume that if the rim doesnt cave in, you have to add a ton of material and we re all sensitive to weight.

[Takiyaki]

Is 35 on 32 IW really that bad? I have been running 28s on 24-25 IW for years and thats about as far off by ETRTO standards. I think if you're not going crazy with pressures or doing 60MPH Pogacar descents it's probably fine. Other thing I guess is the 105 rule is kind of overrated from what Ive heard, so if your 35s mount to 37s on a ~36 EW/28 IW wheel it's probably not the end of the world.

[Sakizashi]

Is 35 on 32 IW really that bad? I have been running 28s on 24-25 IW for years and thats about as far off by ETRTO standards. I think if you're not going crazy with pressures or doing 60MPH Pogacar descents it's probably fine. Other thing I guess is the 105 rule is kind of overrated from what Ive heard, so if your 35s mount to 37s on a ~36 EW/28 IW wheel it's probably not the end of the world.

The problem is that it's likely unknown. The point of the ETRTO standards is that they are the IW to which member tire manufacturers have agreed to certify their tires. Its a reference standard, not a safety testing standard. It's not that using wider widths is known to be unsafe, just that the tires weren't designed to be used on rims with IW that wide, and so the manufacturers didn't validate it.

Blowouts are one concern, but the tread cap being too small and getting flats from riding on the sidewalls are also practical concerns.

Personally, I don't mess around with this. The consequences of getting it wrong are just too high.

[POTOOOOOOOO]

The problem is that it's likely unknown. The point of the ETRTO standards is that they are the IW to which member tire manufacturers have agreed to certify their tires. Its a reference standard, not a safety testing standard. It's not that using wider widths is known to be unsafe, just that the tires weren't designed to be used on rims with IW that wide, and so the manufacturers didn't validate it.

Blowouts are one concern, but the tread cap being too small and getting flats from riding on the sidewalls are also practical concerns.

Personally, I don't mess around with this. The consequences of getting it wrong are just too high.

Good post.

By now you probably know I generally ignore ETRTO and do my own testing.
It’s interesting that the GP5K 35mm tyres I’ve recently purchased were horribly loose on two different 25mm internal hooked wheel sets I tried them with.

I did a test spin but could pop the tyres into the channel with around 15psi in the tyre, and it was extremely easy to burp them with closer to 40psi.

These are all ETRO compliant but I was extremely uncomfortable knowing people would buy these and ride them without a second thought after doing their ETRTO due diligence.

It’s a flawed process for sure. After all my 32mm tyres /rim combo shows no sidewall damage after 1500+ kilometres of hard cornering. And that’s about as far away from Compliant as you can get. ( pictures ported previously )
I’m not recommending it, but id trust these WAY more than the 35mm tyres on 25mm internals I mentioned previously.

[Serge_K]

Cool, I added this info to the https://rubbersideup.cc/ database.

Wonderful resource this. rubbersideup.cc ftw.

[biceryder]

After learning in this thread that Pirelli 40c TLRs were not designed for 32IW wheels.  I continued to ride them for about 500mi.  No issues to report.  My OCD kicked in and I did order Goodyear XPLR 40c road tires.  Expensive, yes.  Took forever to get, yes.  Mounted them on my Tagoola’s tonight.  Interestingly, 40c Pirellis mounted on 32IW rims measured at just over 43mm with 38psi.
Goodyears measured at exactly 40mm at the same PSI.  Interested to see how they perform tomorrow.

[POTOOOOOOOO]

Welcome to the stupid world of ETRTO where the wider tyre isnt compliant, but the narrower one is 🤡

I really didn’t like the Goodyear tyres. They aren’t very fast and they need a really low pressure to be comfortable, so they’re even slower.