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

[Serge_K]

Hello.
https://www.bicyclerollingresistance.com/cx-gravel-reviews/continental-grand-prix-5000-s-tr-35
This came out, and confirmed the 35C is just as fast as the others. The gold standard of road cycling is not any slower in 35C, & available for purchase.
Various OEMs sell rims as wide as 36, 39, or even 41mm. (checked with Peter, Serenade / 7 tiger, Zen).
ETRTO 2024 doesn't agree with the rule of 105, i'm not sure if it's safe to just ignore that standard (assumes hooked rims, nobody seems to be making such wide rims hookless anyway).

Pogi rode that tyre on an unreleased Enve rim. He's sub 66kg. So, 66kg Roubaix vs 80+kg road, seems logical. He had 32C at the back because his frame can't clear more, i'd wager.

In summer 2023, i bought a rear wheel that's 32 wide, that was marketed as gravel only back then. I almost bought the first rims out of that mold. I didn't have the balls to order the same in front, so i went for a 28 wide rim. I regret it to this day: should have gone just as wide in front, and I "knew it", but didn't have the courage. It was pretty "out there" then. On that rear rim, the GP5000 32C measures 34.4mm. Now, pro riders often are on these very rims (32C measuring more).

This feels similar now: we know the rule of 105, and it's the best rule of thumb we have. For most people (western men c.80kg who want something that performs but also just works), i think running that 35C at the back is a no brainer. I also suspect that running the same 35C with an optimal rim is also the best choice, over a 30 or 32C: the biggest change over the years on my bikes has been comfort, and average speeds keep going up. Peace of mind while motoring through bad road patches is wonderful. Not being beaten up at the end of the ride. Not worrying (or less) about potholes, road cracks, tram tracks, gutter grills, greasy hairpins, dirty forest roads, less than ideal roads at altitude, and so on.
Currently, OEMs are selling these wide rims exclusively for gravel, to the point where some dont want to sell me a set if it's to use a 35C tyre, because of ETRTO.

Bottom line:
I think the new frame standard should become 35C (from 32C currently), assuming that means clearance for a rim that's 41mm with a 35C on it.
I'm not upgrading my daily driver for anything that can't clear that (future proofing + comfort w/o rolling resistance penalty).

Anyone to weigh in on the safety / relevance of ETRTO w, say, a 41mm external (hooked) rim w that GP5000 35C?

[POTOOOOOOOO]

So what’s the questions here ?
You want to use 35mm rubber but ETRTO is putting you off ?


I started using a 25mm (Hooked) internal rims back in 2020 when they were first available from lightbicycle. They’ve had everything on them from 28mm GP5Ks to 2.1 thunderberts.

I’m fortunate enough to have quite a few bikes and currently 10 sets of various wheels. My main take away from ETRTO is it’s massively flawed, and should be used only as a guide. Quite simply, different tyres are a tighter and looser fit on different wheels regardless of adherence to ETRTO.
I think their main objective is to keep things safe by ensuring tyre retention when the tyre is flat. However, in my experience and personal testing, it doesn’t ensure anything of the sort.


I’ve had 30mm GP5Ks on a Bontrager wheel that would always try and fall into the central channel - ETRTO compliant, but I wouldn’t ride it.
However, my current favourite is a 32mm GP5K with a tpu tube on a 32mm internal hooked and 40mm external.
Well outside of ETRTO but that tyre is absolutely not going anywhere - I’ve tested it and tried to unmount it, even when flat.
I previously use a 35mm Pro5 which was ok, but not as secure as the smaller GP5K.

My advice is, if you want to put trust in a flawed system, go with ETRTO. However, if you have the ability to test tyres for yourself - go ahead.

Disclaimer - We are all adults and can do whatever we like. Do what you feel is safe and there are probably 20+ other things more effective you can do rather than chase rule 105. ( which has kind of been debunked on newer wheels anyway )

[Rolle2k]

According to BRR these measures 34mm on 18mm IW rims, which would mean almost ~37MM on 25mm IW rims.
I think we would need U-shaped rims with wider external profile, but keeping internal 25-26mm..
So essentialy 25-26mm IW, ~37mm EW at its widest.

[Takiyaki]

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.

[alfiomotrambo]

Same here: for long-distance wheels I’d take a good 32c setup today, but I can see 35c becoming the obvious next step once frames catch up. The speed penalty seems much less worrying than the old road-bike mindset made it sound, while the comfort/safety margin on bad roads is real.

I’d probably shop for wide-road wheels with at least 31–32mm external now, rather than old 28mm EW “road” profiles. One AliExpress example in that direction https://it.aliexpress.com/item/1005009497190160.html

[cccccccccccccccx]

I would not buy a bike that does not fit 35c tyres if 35c is faster and more comfortable, which it seems to be.

But who decided we should stop at 35c? Did Conti and Pirelli test 40, 45 and 50 mm tyres and find 35 to be the fastest? Is there a white paper showing the data for this?

It doesn't make sense to buy a new frame until we have data that shows the actual breakpoint. At what point does a wider tyre become slower?

[POTOOOOOOOO]

I would not buy a bike that does not fit 35c tyres. If 35c is faster and more comfortable, which it seems to be.

But who decided we should stop at 35c? Did Conti and Pirelli test 40, 45 and 50 mm tyres and find 35 to be the fastest? Is there a white paper showing the data for this?

It doesn't make sense to buy a new frame until we have data that shows the actual breakpoint. At what point does a wider tyre become slower?

As will all these things, it depends.
Aero drag vs rolling resistance.
The rougher it is where you ride, the wider the tyre.

I think 35mm is just a good all rounder right now, but the wheels and frames really limit going any wider.

Yes, you can use a gravel frame for wider wheels, but that’s a different thing.

[Sakizashi]

I was a pretty early adopter of 32mm tires on the road — at least among my local groups. I went back to 28mm-30mm a couple of years ago because at my size and weight, even 32mm wasn't needed unless I was planning to hit some gravel.

Cobbles are no joke, so I would also run min 32 or 35mm tires if i was doing the Paris Roubaix sportive or smth.

However, there are plenty of trade-offs with wider tires, both in frame design and geometry, and in aero, so I am not eager to see the industry push people onto bikes that officially clear 35mm tires. Fork width is one issue. Aero-wise, superwide seems to perform best in sims, but narrow seems to do just as well IRL. With wider tires, you negate some of the effort put into the first and the second, as it's likely still optimized around the more aero 28-30mm size. So for a light bike or an endurance-type frame, I want clearance for 35mm tires, even if that means my chainstays can't be 405mm. For an aero bike, I probably still want it designed around 28-30mm tires. While people might still cram wider tires in it, I wouldn't change the design if it affects the optimization.

Rule of 105 is also irrelevant. It was coined in reference to a relatively narrow Toroidal shape and was designed to optimize tire selection for a known rim. It's not really that useful for thinking about rim selection for a tire size, nor is it really relevant for non-toroidal shapes, nor for rims that go out to 35mm at their widest point. That said, you do want a relatively smooth transition from the tire wall to the rim, or if it's designed this way, use a wider bead hook as a tripping feature. I know of very few rims that are designed this way. Oddly, there is one in the DFS catalog that is 25mm internal and 35mm external at the hooks going out to like 37 or 38mm. They even appear to have done some basic CFD. Unfortunately, it tops out at 50mm deep, but it could be an option for someone adventurous enough to go there. I didn't order these because I was worried they wouldn't clear the super-narrow 3T fork I use on my road bike.

The other problem is that tire sizing is all over the place. While 35c is clear shorthand for a 700c x 35mm tire. It doesn't quite mean the same thing as clearing a 35mm-wide tire with 6mm or 4mm on each side, which are both ISO specs, because tire manufacturers use different size references for internal width. I think, for example, Continental uses 23mm IW for 28mm and 30mm tires, but 25mm IW reference for 32mm and 35mm tires. Additionally, I think a lot of the western brand bikes that clear 34mm or 35mm tires are doing it under the ISO racing bike category for 4mm of clearance, but that really means a 30mm tire is what the bike would come with from the factory to meet regulations in a lot of countries that require 5.5 or 6mm of clearance. This is an annoying bike industry thing that probably requires a longer post to get into. I think one could also convince me that 4mm isnt really what you should be recommending for daily use, as the chance of damage is quite high.

[jeanpierrebalsac]

I have been running a 40mm ext 32mm int hooked rims with a 36mm tires (Challenge Strada Bianchi) for a couple of months now, and I love it.

Tires blow up to 40mm wide, so nice shape with respect to the rim.

I built the bike 6 years a go to be my road and gravel bike (Merlin Malt G2X in a couple of sizes smaller than my size so the stack is not too high with 2 wheelsets). The frame has 40mm tire clearance. But the times have caught up to it (as 40mm isnt really consideres gravel anymore) so now its just a roadbike with wide tires. The great part is that when I see a nice mtb/gravel trail in a forrest, I can just send it. Also, can run lower pressure.

[CycOps]

35mm for endurance and allroad frames yes, very confi. But nor for aero frames. Today's aero frames like Cervelo S5 and similar can run 34mm tires WAM. Y1RS does not in the rear, guess some day Y2RS will do. And on normal roads in okay condition, 30mm WAM is already quite confortable, even with stiff frames. I can't see a reason why you would need more than 32mm on an all out aero bike. In the end super wide tires for road bikes is another trend the industry wants to sell.

[bremerradkurier]

35c tires are also going to function better tubeless as the typical air pressure is in a better working range for sealant than narrower tires.

[jonathanf2]

I get a lot of hate from from my road buddies because I run 25c tubeless on my road bikes. I have no problem just running them at 55-60 psi all day. They blow up close to 27-28c and I have no complaints. For my 2x road bikes I really prefer the nimble response of 25c tires. I've tried running 28c tires multiple times and I just don't like them.

On my 1x gravel bikes using a second wheelset, I'm okay running wider 30-35c slicks. For some reason I feel like 1x works better especially since I'm geared lower than 1:1 allowing me to spin at higher cadence.

[tisun]

I'm also an early adopter of 32mm tires.  However, as other members said, I went back to 28mm since the weight penalty was too much (100g per tire) and I'm lightweight anyway (65kg).  Running Conti 28mm with TPU tubes, it hits the sweet spot for me.

[patliean1]

This season I've been running 32c rear and a 30c front set of GP5000 clinchers w/ TPUs. Across a variety of different wheels with internal rim widths either 23mm or 24mm. I weigh around 76kg running 58-61 PSI. So far the setup has been a great balance between race days and general endurance riding.

My latest set of XMCS wheels uses 26mm internal rim. Decided to mount in a full set of 32c front and rear GP5000 STR albeit still w/ tubes because that's all I had lying around. The tires stretch to 34.5mm-ish at the rim. 55-57 PSI.

While comfortable and super smooth, both the weight penalty and lack of road feedback is noticeable. 100% awesome for steady state efforts on not so great pavement. But anytime out of the saddle or accelerating out of a corner is when you are reminded of the larger volume. And added weight. Not mention STR tires are inherently heavier than their clincher counterparts. I think I'm gonna bit the bullet and just order a new set of 30c clinchers. They should still stretch to around 31-32mm at the rim anyway.

[Pistonbroke]

I'm very much up for some fatty boom batty 35mm or bigger on my next road build.
Roads round here are like downtown Mogadishu.